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Seasonally Dry Tropical Forests
Journal of Ecology
... The seasonally dry tropical forest (SDTF), in which most Ceiba species are present ( Table 1, 13 species), is characterized by several months of severe drought (with rainfall less than 100 mm) [18,19]. These types of tropical forests usually have a mean annual temperature above 17 °C and annual rainfall ranging from 250 to 2000 mm, which occurs ...
... The seasonally dry tropical forest (SDTF), in which most Ceiba species are present ( Table 1, 13 species), is characterized by several months of severe drought (with rainfall less than 100 mm) [18,19]. These types of tropical forests usually have a mean annual temperature above 17 • C and annual rainfall ranging from 250 to 2000 mm, which occurs mostly during six to eight months [19]. ...
... These types of tropical forests usually have a mean annual temperature above 17 • C and annual rainfall ranging from 250 to 2000 mm, which occurs mostly during six to eight months [19]. Unlike savannahs, which generate under the same climatic conditions and are dominated by a xeromorphic, fire-tolerant grass layer, the SDTF are tree-dominated and have an almost continuous canopy [18]. These ecosystems occur in disjunct floristic nuclei that show high levels of beta diversity [20]. ...
The species of the genus Ceiba produces fruits with fibers with a high content of cellulose. The fiber is used for textiles, cushion filling and for industrial purposes and its characteristics have been studied in some species including Ceiba pentandra (kapok), C. speciosa and C. aesculifolia. The use of the trunk and seeds of Ceiba has also been described for different species. This article presents a review on the biological diversity of the genus Ceiba (Malvaceae). The genus Ceiba has 18 recognized species that are distributed naturally in America and Africa. However, some Ceiba trees have been introduced to various countries, especially in Asia, due to their ornamental interest and potential uses for their fiber. Ecophysiological studies of different Ceiba species have shown that resistance to adverse environmental conditions varies from species to species. Therefore, Ceiba species are considered potentially useful in restoring ecosystems impacted by human activity. The information related to the classification, morphological characteristics, phenology, ecophysiology and distribution of the different species will be extremely relevant for the sustainable production of kapok fiber. Finally, the recent genomic and transcriptomic studies also provide a valuable resource for further genetic improvement and effective use of Ceiba trees.
... On the other hand, in the SDTFs the biota is exposed to environmental stress produced by to long periods of drought, high temperatures, and high solar incidence (Espinosa et al., 2012;Jara-Guerrero et al., 2019Ordóñez-Delgado et al., 2016). Birds respond to this strong climatic seasonality by changing their behavior and physiology to survive during the dry season (Bullock et al., 1995). The main adaptive strategies of these animals are based on changes in daily activity patterns to reduce water loss or changes in the diet to exploit resources that are not available in dry periods (Bullock et al., 1995). ...
... Birds respond to this strong climatic seasonality by changing their behavior and physiology to survive during the dry season (Bullock et al., 1995). The main adaptive strategies of these animals are based on changes in daily activity patterns to reduce water loss or changes in the diet to exploit resources that are not available in dry periods (Bullock et al., 1995). All these strategies allow the adaptation and maintenance of homeostasis (Allostasis processes) (Mcewen & Wingfield, 2010), which involves changes energy use and accumulation of glucocorticoids. ...
Multiple studies have shown that exposure to pollutants can increase genotoxic damage in different taxa. However, to our knowledge, the effects of environmental stress have been explored little. In certain stressful ecosystems, such as seasonally dry tropical forests, the combined effects of anthropogenic activities and ongoing global changes can cause an increase in environmental stresses, in turn, may trigger physiological and genetic effects on biodiversity. The present aims to assess changes in the prevalence of genotoxic damage in birds within three states of forest degradation in the Tumbesian Region of Western Ecuador. We used blood samples from 50 bird species to determine the frequency of micronucleus and nuclear abnormalities in erythrocytes. Our results revealed a significant impact of forest degradation on the occurrence probability of micronucleus and nuclear abnormalities at the community level. Localities with higher levels of degradation exhibited higher levels of abnormalities. However, when analyzing the dominant species, we found contrasting responses. While Lepidocolaptes souleyetii showed a reduction in the proportion of nuclear abnormalities from the natural to shrub‐dominated localities Troglodytes aedon and Polioptila plumbea showed an increase for semi‐natural and shrub‐dominated respectively. We concluded that the degradation process of these tropical forests increases the stress of bird community generating genotoxic damage. Bird responses seem to be species‐specific, which could explain the differences in changes in bird composition reported in other studies.
... El BTS es un tipo de ecosistema accesible para los humanos, lo cual lo expone a altas tasas de cambio de uso de suelo por el desarrollo de actividades mayormente agrícolas y de pastoreo (Bullock et al., 1995). Esto, principalmente porque los suelos del BTS, pueden ser profundos y fértiles y por lo tanto adecuados para cultivos, aunque mayormente dominan suelos jóvenes, rocosos y superficiales, bajos en nutrientes en zonas con pendientes suaves (Cotler et al., 2002). ...
... La investigación enfocada a la ecología del BTS es amplia (e.g., Bullock et al., 1995;Dirzo et al., 2011) y los estudios relacionados con la dinámica funcional del suelo en interacción con la vegetación y bajo efecto antropogénico han incrementado en las últimas décadas (Jaramillo et al., 2010;García-Oliva y Jaramillo, 2011;Powers y Marin-Spiotta, 2017). Sin embargo, aunque se ha hecho un esfuerzo por entender la dinámica funcional del BTS en respuesta a los disturbios, el conocimiento de las implicaciones que tienen el cambio de uso en el suelo y la influencia del cambio climático sobre el BTS a escala de ecosistema aún es limitado; principalmente en relación con el estudio sobre la variabilidad y los procesos que controlan el intercambio de CO2, agua y energía y cómo estos responden a los disturbios (Martínez-Yrízar et al., 2017;Quijas et al., 2019;Jaramillo et al., 2011). ...
Los ecosistemas continuamente intercambian carbono y vapor de agua con la atmósfera a través de procesos ecosistémicos. En general, la producción neta del ecosistema refleja el balance entre los flujos de entrada de carbono por productividad y la liberación por la respiración ecosistémica. Evaluar esta producción a lo largo de los cambios producidos por la sucesión ecológica secundaria representa un desafío muy grande. En este contexto, la técnica de covarianza de vórtices está siendo ampliamente utilizada para cuantificar flujos ecosistémicos de manera continua. En el bosque tropical seco se han establecido varios sitios de monitoreo utilizando esta técnica para conocer la funcionalidad del ecosistema durante la sucesión ecológica. Esta información puede contribuir a la toma de decisiones en términos de conservación y administración de servicios ecosistémicos, así como para alimentar modelos para predecir la respuesta de este ecosistema estacional seco al cambio climático. Los ecosistemas tropicales secos son de gran relevancia para el ciclo del carbono debido a su considerable extensión y productividad. El reto de estudiar estos ecosistemas radica en que su dinámica de producción de carbono está acoplada principalmente a la disponibilidad estacional de agua. De manera que, el objetivo de este trabajo fue actualizar la información de las interacciones biosfera-atmósfera utilizando la técnica de covarianza de vórtices particularmente en bosques tropicales secos, con el fin de resaltar el efecto de la sucesión ecológica en la dinámica del carbono en estos bosques. Asimismo, se muestra y resalta la importancia local y global de este tipo de sistemas de monitoreo funcional de ecosistemas en México.
... Some facies of TDF and most of the savanna types are essentially tree-codominated ecosystems. Vieira and Scariot (2006) suggested that TDF is frequently connected to savanna because they occur under the same (seasonal) climatic conditions, yet the former is often found in soils of higher fertility (Bullock et al. 1995;Pennington et al. 2000). This observation is of value, although the lack of continuous grass undergrowth, and consequently high cover of dead leaf litter, is particularly striking compared with the savannas being functionally C4-grasslands ) although often also wooded. ...
... From the physiognomic perspective, the TDF has at least three faces: tall forests, low (scrub) forests, and low thickets. Pennington et al. (2000) consider the TDF to be mostly deciduous during the dry season, and deciduousness increases along a gradient as rainfall declines, although there is a marked increase in evergreen and succulent species in the driest forests (Bullock et al. 1995). In Africa, the woody species in TDFs are deciduous and semi-deciduous. ...
The forests of South Africa and the neighbouring countries, including Lesotho, eSwatini, Namibia, Botswana, Zimbabwe, and Mozambique (south of the Zambezi River), were mapped and classified according to the global system of biomes. The new four-tier hierarchical biome system suggested in this paper includes zonobiome, global biome, continental biome (all recognised earlier), and regional biome – a novel biome category. The existing spatial coverages of the forests were revised and considerably improved, both in terms of forest-patch coverage and mapping precision. Southern Africa is home to three zonal forest types, namely Subtropical Forests (Zonobiome I), Tropical Dry Forest (TDF; Zonobiome II) and Afrotemperate Forests (Zonobiome X). These three biomes are characterised by unique bioclimatic envelopes. Five, two, and eight regional biomes, respectively, have been recognised within these zonal biomes. Recognition of the Zonobiome I and the global biome Tropical Dry Forests in southern Africa is novel and expands our knowledge of the biome structure of African biotic communities. The system of the azonal regional biomes is also new and comprehensively covers the variability of the azonal helobiomes (riparian woodlands and swamp forests), mangroves, and azonal coastal forests. In total, 11 azonal regional biomes have been recognised in the study area. The forest biomes in southern Africa were captured in our electronic map in the form of more than 60 000 polygons, covering 42 416 km² (1.27% of the study area). No less than 83% of these forests occur in the territory of southern Mozambique.
Abbreviations: for the abbreviation of the biome units, see Table 1; CE: centre of endemism; IOCB: Indian Ocean Coastal Belt; MBSA: the area of the Map of Biomes of Southern Africa; VegMap2006 and VegMap2018: Vegetation Map of South Africa, Lesotho and Swaziland (as released in respective years); for the meaning of the codes of the biome units see Table 1, and for the meaning of the abbreviations of climatic characteristics see Appendix S1
... . These forests are characterized by a severe dry season that lasts several months each year. Dry broad leaved seasonal forests are often characterized by drought-deciduous tree species (Bullock, Mooney and Medina, 1995). The remaining cover of this forest type has been estimated to be roughly 1 million km² globally (Miles et al., 2006). ...
Dry broad-leaved seasonal forests are widespread in Southeast Asia. They are characterized by drought deciduous tree species, which are adapted to a severe dry season that lasts several months each year. Forest fires are frequent in this vegetation type. To further understanding of fire behavior and fire impact, a series of fire field experiments implemented in the Huay Kha Khaeng (HKK) Wildlife Sanctuary (Uthai Thani Province, Thailand) between 2008 and 2016 was analyzed. A fire behavior model based on the Canadian Fire Behavior Prediction System (Prometheus) was calibrated using the experimental data for the deciduous dipterocarp forest fuel type. The model was then tested on a remotely observed large wildfire in Thailand. Our results confirm the slow fire spread and low to moderate fire intensities observed for this forest type in earlier studies. The fire spread model performs well compared to satellite observations but tends to overestimate area burned and fuel consumption and, consequently, fire emissions when used in air pollution models. Our results indicate that widely used global databases may substantially overestimate fuel consumption and hence fire emissions for this forest type.
... Chamela se caracteriza por un clima tropical y una diversidad de ecosistemas, incluyendo bosques tropicales caducifolios, bosques de galería y manglares (Bullock 1986;Duran et al. 2002). La variabilidad topográfica y climática de la región, con una prolongada estación seca y una breve temporada de lluvias, influye significativamente en el ecosistema local (Fig. 2) (Bullock et al. 1995, Lott et al. 1987. ...
... Dry forests are one of the major providers of ES that are vital sources of income and resources to satisfy daily needs for millions of people in the drylands, especially in developing countries (Worku et al., 2014). Dry forests, which constitute nearly half of the world's tropical forests (Blackie et al., 2014;Sunderland et al., 2015), are forests, woodlands, shrublands, thickets, or wooded grasslands that occur in tropical and sub-tropical areas, where rainfall is scarce and erratic, where the mean annual temperature is higher than 17⁰C, and where the annual potential evapotranspiration is higher than precipitation for a significant part of the year (Bullock et al., 1995;Murphy and Lugo, 1986). They are highly diverse systems, characterized by strong seasonality in water availability (Murphy and Lugo, 1986). ...
... No norte do estado de Minas Gerais é conhecida como Mata Seca, considerada uma fitofisionomia da Caatinga (Prado, 2005). Nessas áreas ocorrem longos períodos de estiagem, de cinco a oito meses, com precipitação sazonal inferior a 1600 mm (Mooney et al., 1995), vegetação rica, e predomínio de espécies arbóreas caducifólias (Pennington et al., 2006), com dispersão altamente limitada (Santos et al., 2012). ...
A floresta estacional decidual, também conhecida por Mata Seca no Brasil, é uma formação florestal Neotropical de distribuição disjunta, prioritária para conservação em função de sua redução por atividades humanas, o que torna emergencial estudos para conhecer sua biodiversidade. Entretanto, não existem registros de espécies de opiliões nessa formação florestal. Dessa forma, o presente estudo teve como objetivo inventariar a fauna de opiliões no Parque Estadual da Mata Seca, norte do estado de Minas Gerais, uma das mais importantes áreas de Mata Seca do Brasil. Foram realizadas coletas entre fevereiro e novembro de 2021, com 20 dias de campo, totalizando 60 horas de esforço amostral por pesquisador. Foram registradas três espécies de opiliões de duas famílias, Gryne coccinelloides (Mello-Leitão, 1935), Cosmetidae, representando 89,49% dos espécimes coletados, Metavononoides guttulosus (Mello-Leitão, 1935), Cosmetidae, e Parapachyloides uncinatus (Sørensen, 1879), Gonyleptidae. Este é o primeiro registro da diversidade de opiliões para a Mata Seca no Brasil, sendo que duas espécies não ocorrem em outras unidades de conservação no estado de Minas Gerais, o que reforça a importância dessa área para proteção da biota local.
... The successful implementation of biocontrol strategies to combat the spread of VBD requires a deeper understanding of the pathogen [14,15], the natural behaviors of their vectors [16], as well as the local environmental factors [17] that can be manipulated to break the disease transmission cycle with minimal unintended consequences on non-target organisms or local ecosystems [18]. El Salvador is characterized by tropical dry forests [19,20], consisting of deciduous forests where most tree species shed their leaves during the drought season, and floristically distinct gallery forests where most tree species retain their leaves throughout the year [21]. Seasonally dry tropical forests, such as those in El Salvador, are particularly sensitive to changes in climate, including variations in temperature and precipitation patterns. ...
Vector-borne disease (VBD) accounts for more than 17% of the global infectious disease burden, disproportionately affecting developing nations within tropical and subtropical areas. As Aedes aegypti mosquitoes are the principal vector for the transmission of many Public Health pathogens, our study examined their population dynamics within the seasonal context of tropical dry biomes in El Salvador as incidence of VBD in this region has increased in recent years. Species that rely on sexual reproduction must maintain a balanced sex ratio (1:1) to support their population dynamics, however, our phenological analysis of field collected A. aegypti specimens revealed significant sex ratio variations during dry and wet seasons. Interestingly, we detected a seasonal shift that favored female mosquitoes during the dry season, highlighting the dynamic nature of mosquito populations in highly urbanized environments like El Salvador. By linking sex ratio distortions to anthropogenic factors, our study underscores the importance of comprehensively characterizing the urban ecology of vectors for the development of effective biocontrol strategies. As such, we
advocate for more nuanced vector control approaches that consider ecological factors as well as the human behaviors that influence mosquito breeding habitats to effectively combat the rise of VBDs amid global climate changes.
... At all study sites, periods of complete leaflessness were observed in some individuals under observation during the drier months of December-February for both years. This leafless period is an adaptation to avoid water stress which affects flowering time of tropical forest trees (Bullock et al., 1995). ...
... A nivel global, los BTES abarcan el 42% de la extensión total de los bosques tropicales (Miles et al., 2006). A pesar de su considerable tamaño y su importancia para las comunidades humanas que los habitan, estos ecosistemas han recibido una atención científica sorprendentemente limitada en comparación con los bosques tropicales húmedos de la misma región (Bullock et al., 1995;Sanchez-Azofeifa et al., 2005). Esta falta de interés hacia los BTES se debe en parte a su menor diversidad comparativa, ya que albergan entre 50 y 70 especies de árboles con un diámetro mayor a 2.5 cm por hectárea, en contraste con los bosques húmedos, que pueden llegar a tener entre 200 y 250 especies en condiciones similares (Gentry, 1995 (Janzen, 1988;Dinerstein et al., 1995;Balvanera, 2012 ...
... Tree species diversity is an important aspect of forest ecosystem diversity [14] and also fundamental to tropical forest biodiversity. Tree census plots have been established in forest types through tropical regions to monitor forest dynamics over time and to assess the effects of disturbance and climate change on plant demography [15,16]. As the Eastern Ghats constitute important catchments of the peninsular and natural resources, they are threatened due to anthropogenic disturbances [17]. ...
A landscape level plant diversity and population inventory was made in High altitude forest of eastern Ghats, Visakhapatnam District, Andhra Pradesh, India comprising mostly dry deciduous and moist deciduous forests. In all the three study sites, two belt transects of 5 × 1000 m size (totaling 1 ha) were laid in each site during 2022–2023 and all trees with ≥15 cm girth at breast height (gbh) were enumerated. Within each transect of 1000 x 5 m, quantitative data in respect of herb species was collected from two numbers of small sample plots each measuring 1m x 1 m. A total of 246 species was recorded on enumeration, of which 54 Trees, 50 Shrubs and 90 Herbs were noted.
... Cavanillesia and Ceiba in South America; Commiphora in Africa; Brachychiton in Australia) are the flagship physiognomic features of the TDF (Fig. 2.8). Most importantly, enforcing the functional distinction between savannas and the TDF, Concise ecological accounts of the TDF are found in Murphy and Lugo (1986), Bullock et al. (1995), Pennington et al. (2006), Dirzo et al. (2011) andDexter et al. (2015). ...
The wet Tropics, home to the zonobiome E1, under the strong influence of the high tropical high temperatures and the Intertropical Convergence Zone controlling high precipitation, are shared between the Northern and Southern Hemisphere. The rainforests are shared between four continents (South America, Africa, Asia, and Australia, as well as neighbouring Mesoamerica, Madagascar, Sundaland archipelagos, and numerous islands of the Indian and Pacific Oceans. The chapter focuses on the nature and delimitation of the subtropical rainforests—a biome often neglected or misunderstood. The biome classification of the tropical and subtropical forests reflects the geographic isolation (continents, oceanic archipelagos). Seasonal Tropics, characterised by alternating precipitation-rich and precipitation-poor periods, support two major biomes known as savanna (SAV) and tropical dry forest (TDF). They form a zonobiome E2. The savannas are multi-faced ecosystems, including grasslands and open and closed woodlands. They can be mesic and arid. The unifying functional element is the understory dominated by C4-grasses and the associated importance of recurrent fires. This chapter presents a consolidated hierarchical classification of the savanna, reflecting the continental idiosyncrasies. This chapter pays special attention to the problem of the natural status of the Madagascan savannas (subtropical-tropical grasslands) and the intriguing nature of so-called ‘underground forests’. On the other hand, the TDF is a grass-poor ecosystem and is usually fire-shy. It is widely distributed in the Tropics, but its bioclimatic underpinnings were, until now, poorly analysed. This chapter mitigates this situation by recognising zonal and azonal TDF types and linking the zonal ones to the climatic anomalies of otherwise clearly defined dynamics of the Intertropical Convergence Zone. Particular attention is paid to the bioclimatic underpinnings of Caatinga (a major South American TDF) and the TDF of the Horn of Africa.KeywordsArid savannaCaatingaHorn of AfricaMadagascarMata AtlanticaMesic savannaSubtropical rainforestTropical dry forestTropical rainforestUnderground forests
... In the literature, this area has been historically known as the savanna corridor (Schmidt and Inger, 1951) (or diagonal of open formations, Vanzolini, 1963), a region that includes dry biomes, characterized by low rainfall and well-defined seasonal variation (Werneck, 2011). These areas also have similar vegetation that are adapted to these climatic conditions, in addition to complex mosaic-like distributions (Mooney et al., 1995;Furley and Metcalfe, 2007). Thus, many initial interpretations led to the understanding that throughout this distribution range, the organisms were on the same evolutionary history. ...
... In the literature, this area has been historically known as the savanna corridor (Schmidt and Inger, 1951) (or diagonal of open formations, Vanzolini, 1963), a region that includes dry biomes, characterized by low rainfall and well-defined seasonal variation (Werneck, 2011). These areas also have similar vegetation that are adapted to these climatic conditions, in addition to complex mosaic-like distributions (Mooney et al., 1995;Furley and Metcalfe, 2007). Thus, many initial interpretations led to the understanding that throughout this distribution range, the organisms were on the same evolutionary history. ...
An extensive review of primary and secondary occurrence data, including several new records, of the South American native antlion Dimares elegans (Perty) revealed that this species is endemic to regions of stressful water regime (Caatinga, Cerrado, Chaco and temperate fields) and adjacent areas in Amazon rainforest, Atlantic forest and Pampas. Its known distribution is from Santarém, Pará state, northern Brazil to Río Negro, Chimpay, northwestern Argentina. The known distribution of the species in Brazil has been extended, registering several areas above the São Francisco River (former possible northeastern limit). New limits further east were established from new primary records. For the first time the species is registered from the Brazillian states of Maranhão, Piauí, Rio Grande do Norte, Paraíba, Bahia, Goiáis, Tocantins, Minas Gerais, Mato Grosso do Sul, São Paulo and Paraná, Brazil. Historical data of occurrence in Goiás (Cerrado) have been geopolitically rectified (Tocantins) and, present occurrence in Goiás is reported by primary data in two new localities. Antlions are mostly xerofilous species, however with recent data this species might present much wider distribution than restricted to seasonally dry forests.
Keywords:
Diagonal of open formations; Endemism; Caatinga; Cerrado
... The results of this study will provide new insights into the role of lithology on tropical forest development potential and its responses to environmental and climate changes. Given the large extent of TDF across the tropics (Murphy and Lugo, 1986;Hasnat and Hossain, 2020) and the variety of lithologies characterizing the landscapes where it occurs (Mooney et al., 1995), the results of this study will advance the understanding of TDF dynamics at landscape and regional scales. ...
Introduction: Tropical dry forests (TDF) are not only the most widespread tropical forest type but also the most threatened forest ecosystem worldwide. Yet, because their dynamics have been insufficiently studied, our knowledge about the factors responsible for the spatial and temporal variability in TDF dynamics remains very limited. In this study, we aimed (1) to assess the effects of two lithological substrates on TDF structure, diversity, and species composition, and (2) to determine whether and how these substrates affect temporal dynamics onTDF attributes.
Methods: We used information gathered through a 12-year long annual monitoring of 14 old-growth TDF permanent plots in southern Mexico, seven of which were established on limestone and seven on phyllite. Previous work shows that limestone-derived soils have higher humidity, conductivity, and phosphorous and calcium contents, but lower nitrogen content.
Results: TDF structure and diversity attributes were consistently higher on limestone TDF, while canopy height was higher on phyllite TDF. By contrast, temporal variation in TDF attributes, demographic rates (recruitment, growth, and mortality) and attribute residence times were indistinguishable between substrates. We also found a strong differentiation of species composition between substrates, yet substrates did not influence the temporal behavior of composition.
Discussion: Our results suggest that limestone is a more favorable environment for TDF development (soil-effects mechanism), but the flora of the forest on phyllite seems to be better adapted to cope with harsher environmental conditions (composition-effects mechanism), which counterbalances the environmental advantage of limestone, ultimately resulting in spatially homogeneous TDF dynamics at the landscape level. Future studies should examine the role of functional attributes on old-growth TDF dynamics, as this will allow a better understanding of the impacts of extreme climatic events on forest attributes and their dynamics, as well as to foresee potential ecosystem state shifts and tipping points
... Dry forests are one of the major providers of ES that are vital sources of income and resources to satisfy daily needs for millions of people in the drylands, especially in developing countries (Worku et al., 2014). Dry forests, which constitute nearly half of the world's tropical forests (Blackie et al., 2014;Sunderland et al., 2015), are forests, woodlands, shrublands, thickets, or wooded grasslands that occur in tropical and sub-tropical areas, where rainfall is scarce and erratic, where the mean annual temperature is higher than 17⁰C, and where the annual potential evapotranspiration is higher than precipitation for a significant part of the year (Bullock et al., 1995;Murphy and Lugo, 1986). They are highly diverse systems, characterized by strong seasonality in water availability (Murphy and Lugo, 1986). ...
... P1BSOT, P2BSOT y P3BSOT: Parcelas 1, 2 y 3 de sotobosque en banco; P1SBBSOT, P2SBBSOT y P3SBBSOT: Parcelas 1, 2 y 3 de sotobosque en subbanco; P1BAJ, P2BAJ y P3BAJ: Parcelas 1, 2 y 3 de sotobosque en bajío Table 5.-Beta Diversity Index (Jaccard) for Paired Interactions of physiographic conditions in Sector "A", El Caimital, Obispos, Barinas-Venezuela. Note: P1B, P2B and P3B: physiographic unit bank plots 1, 2 and 3; P1SBB, P2SBB and P3SBB: physiographic unit sub-bank Plots 1, 2 and 3; P1BAJ, P2BAJ and P3BAJ: physiographic unit bajío plots 1, 2 and 3. P1BSOT, P2BSOT and P3BSOT: Plots 1, 2 and 3 of understory in physiographic unit bank; P1SBBSOT, P2SBBSOT and P3SBBSOT: Plots 1, 2 and 3 of understory in physiographic unit sub-bank; P1BAJ, P2BAJ and P3BAJ: Plots 1, 2 and 3 of understory in physiographic unit bajío coincide con los trabajos de: Bullock et al. (2009) para un mismo tipo de bosque; Moret et al. (2010) para el mismo sector del bosque; Lozada et al. (2007) y (2008) en bosques de las Reservas Forestales de IMATACA; Díaz et al. (2012) en bosques ribereños de la cuenca del Río Caura; Gentry (1988), en bosques secos neotropicales. Dentro de las especies más importantes en los resultados IVI e IIA del presente trabajo, B. Alicastrum y C. candidissimum coinciden con el realizado por Moret et al., (2010), en el mismo sector del bosque; Kochaniewicz y Plonczak (2004), reportan a T. americana, A. diversifolia y B. alicastrum en la Reserva Forestal de Caparo; Aymard (2015) de igual forma reporta a C. candidissimum, B. alicastrum y Attalea butyraceae para los llanos venezolanos. ...
El objetivo de este trabajo fue identificar las comunidades boscosas en las diferentes unidades fisiográficas (UF) dentro del Bosque Universitario El Caimital (BUEC), evaluar su estructura y composición florística. Para ello se establecieron, nueve (9) parcelas de 1 ha (100x100m), tres (3) por cada unidad fisiográfica (banco, subbanco y bajío), ubicadas aleatoriamente bajo un diseño con restricciones. En cada parcela, se midieron todos los individuos de especies arbóreas con un DAP ≥ 10 cm y los individuos con DAP < 10 cm se evaluaron 3 transeptos en cada parcela de 2x10 m (20 m2). Se estimaron las diversidades alfa y beta, el Índice de Valor de Importancia (IVI), Índice de Importancia Ampliado (IIA). Se realizó un análisis de conglomerados para determinar si existían similitudes florísticas entre los tipos de bosque. Se registraron 2235 individuos, clasificados en 27 familias y 63 especies. El índice de diversidad de Shannon-Wiener fue 3,33. La densidad promedio del bosque fue 248 individuos/ha. La familia Fabaceae fue la más representada. En las tres unidades fisiográficas se identificaron Attalea butyraceae, Calycophillum candidissimum y Piper sp. Se discuten aspectos florísticos y ecológicos de las especies registradas y se presenta un listado.
... In contrast, the highly seasonal tropical dry forest (TDF) has received less attention from the research community-and society at large-than their more humid tropical counterparts [4]. Indeed, even landmark compilations of TDF ecology and conservation, e.g., [5,6], minimally address the topic of restoration, which is critical as this is one of the most threatened ecosystems on Earth [7,8]. The ten papers in this Sustainability Special Issue represent an effort to close that knowledge gap and advance our understanding of the science and practice of restoring these understudied ecosystems. ...
In 2019, the General Assembly of the United Nations proclaimed 2021 to 2030 to be the United Nations Decade on Ecosystem Restoration [...]
... En comparación con los otros tipos de ecosistemas tropicales, los bosques secos neotropicales han recibido muy poca atención en cuanto a su estudio y conservación. Bullock et al. (1995) hicieron una excelente recopilación de lo que se conoce acerca de este tipo de bosques. En el aspecto florístico y estructural, Gentry (1995) compara la vegetación de esta zona de vida en diferentes localidades del Caribe, Centro y Sudamérica, incluyendo algunas colombianas (Galerazamba en Bolívar, Tayrona en Magdalena, Lomas de Santo Tomás en Tolima y Colosó en Sucre). ...
Se estudió la composición de plantas vasculares de un fragmento de bosque seco tropical, localizado en San Sebastián (Magdalena, Colombia). Se utilizó una muestra de 40 unidades de 100 m2 cada una para un área total de 0.4 ha. Se muestrearon todos los individuos presentes que tuvieran un DAP 3 2.5 cm. Los resultados generales dan un total de 155 especies de plantas vasculares representadas en 42 familias, de las cuales Leguminosae, Bignoniaceae, Rubiaceae, Malpighiaceae, Capparidaceae, Hippocrateaceae y Sapindaceae son las que más especies presentan. Se identificaron 75 géneros, de los cuales Capparis (Capparidaceae) fue el más diverso, con siete especies. La mitad del total de individuos analizados pertenecen a las familias Rubiaceae, Ulmaceae, Leguminosae y Bignoniaceae. Con base en el hábito de crecimiento se encontró que la mayoría de los individuos analizados fueron árboles, seguidos por lianas y arbustos. La mitad de las especies de lianas pertenecen a tres familias, siendo Bignoniaceae la mejor representada, con trece especies.
... Tropical dry forest is one of the major ecosystems in México. This forest is highly seasonal with respect to the amount and distribution of rainfall during the year (Bullock et al., 1995). As higher order consumers, lizards should be affected by this seasonality because invertebrate populations vary with rainfall. ...
... Las áreas donde se recolectó el material de las especies para el presente análisis son de formaciones de bosque seco tropical (BST) y bosque húmedo tropical (BHT), de países como: México, El Salvador, Costa Rica, Panamá, Colombia y Perú (tabla 1). Estas formaciones fueron delimitadas con base en diferentes sistemas de clasificación de zonas de vida (Bullock et al. 1995, Holdridge 1967, Pennington et al. 2000, 2004. ...
Enckea es uno de los clados con distribución neotropical del género Piper (L.), compuesto por aproximadamente 80 especies que generalmente exhiben hábitos de crecimiento arbóreo, arbustivo, herbáceo y lianescente. Dicho clado es el único al interior de Piper que se distribuye en su mayoría en zonas de bosque seco tropical (BST), con un reducido número de especies distribuidas en bosque húmedo tropical (BHT) de Centro y Sur América. A pesar de la particular distribución de Enckea y de ser un elemento frecuente en el BST, no existen trabajos donde se describa de manera detallada la anatomía caulinar de sus especies. Esta información puede usarse para determinar la relación entre la presencia de estos caracteres anatómicos y el hábitat de las especies. En el presente estudio analizamos la anatomía de los ejes caulinares de 25 especies de Enckea, buscando variaciones morfológicas a nivel de hábitos de crecimiento y tipos de hábitat. Encontramos diferencias en los haces vasculares y tejidos de sostén entre las especies arbustivas y herbáceas, así como la presencia de una endodermis claramente diferenciada en algunas especies de BST. Se registra la presencia de aerénquima en Piper nudilimbum, una especie distribuida en llanuras aluviales de la Amazonía. Aunque se observó un considerable rango de variación morfológica, no hubo una clara diferenciación anatómica a nivel caulinar que permitiera diferenciar rigurosamente las especies de Enckea de BST de las de BHT.
... Los bosques secos tropicales (bs-T), corresponden a ecosistemas complejos y frágiles, que albergan una riqueza única de biodiversidad y en los cuales la evaporación excede a la precipitación, presentando uno o dos periodos de sequía que pueden durar entre 4 a 6 meses en el año (Janzen 1986, Luttge 2008, Murphy y Lugo 1996, lo que genera déficit de agua en el suelo, cuya consecuencia es la defoliación de la vegetación como respuesta al estrés hídrico (IAvH 2002, Lobo et al. 2003Murphy y Lugo 1996. Esto genera mayor diversidad estructural y fisiológica en formas de vida (Mooney et al. 1996), mezclando especies caducifolias con siempre verdes, constituyendo patrones complejos de tipo ecofisiológico (Burnham 1997). ...
Se evaluó la diversidad florística en doce fragmentos de bosque seco tropical de siete municipios del sur del departamento del Tolima (Colombia), en la Ecorregión Estratégica de la Tatacoa y su área de influencia del Alto Magdalena. Se estableció una red de 12 parcelas de 50 x 50 m (0,25 ha), una en cada fragmento, registrándose todos los individuos arbóreos con diámetro superior a 5 cm. Se encontraron 121 morfoespecies agrupadas en 41 familias. La riqueza varió entre 15 y 34 especies por parcela, lo que permitió clasificar las coberturas vegetales en diferentes categorías de diversidad según los índices de riqueza y uniformidad. Se determinó la riqueza estimada, cuyos máximos valores variaron entre 44 y 46 especies. Las parcelas con mayor número de especies únicas alcanzaron valores entre 9 y 11; mientras que los valores mayores de especies únicas con abundancia unitarias estuvieron entre 3 y 5. El modelo de abundancia relativa que mejor describe los bosques evaluados corresponde a la serie logarítmica, sin embargo, cuando corresponden a sucesiones tempranas la serie geométrica mejora considerablemente su ajuste. Los modelos Log-Normal y Broken Stick, tienden a ajustes intermedios. Por otro lado, las relaciones de diversidad beta para estos bosques no superaron el 50% de similaridad. Los resultados permitieron priorizar los bosques en cuanto a su diversidad florística y rareza como potenciales para la futura conservación y restauración del bosque seco tropical del Alto Magdalena.
... El uso del suelo predominante es la ganadería de doble propósito con un manejo ganadero homogéneo y relativamente extensivo. La vegetación natural de la región correspondería a Bosque subhúmedo tropical transicional (Holdridge, 2000) con vegetación semi-caducifolia, la que también puede ser considerada como bosque tropical seco estacional (Bullock et al. 1995). La vegetación común es un mosaico de especies nativas y naturalizadas que incluyen pastos, hierbas y vegetación leñosa. ...
In Colombia, where arid and semi-arid landsare also common, the livestock productionhas been limited because the scarcity andthe low quality fodder during the dry sea -sons. In this context woody forage speciesare an option to confront the low forageavailability. An important step for the ex -pansion and adoption of silvopastoral andagrosilvopastoral systems that not only im-prove the function of productivity, but alsowere compatible with the climatic variabili-ty, is the understanding of the multiple func-tions that woody species would present.The biomass production at three cut inter-vals and two cut heights were evaluatedfor Guazuma ulmifolia, Cordia dentata, Hae-matoxylon brasiletto, Caesalpinia coriria, Al-bizia saman, Prosopis juliflora, Senna atoma-ria and Acacia farnesiana. The eight specieswere stablished under the Rueda Nerdel,a systematic design with three repetitions.We found that non-leguminous species asC. dentata y G. ulmifolia had higher biomassproduction after 42 days, 0, 5 m (cut height) and the higher shoot production. For theeight species, functional traits as specificleaf area, leaf dry matter content and leafnitrogen concentration determined that inthe order, G. ulmifolia, C. dentata, A. saman yH. brasiletto presented strategies for a fastuse of resources that can be supported in ahigher growth rate. This result shows thereis compatibility between the biomass pro-duction and the functional biodiversity ofthe woody species tested for the design of multifunctional silvopastoral systems.
... En México, la selva estacionalmente seca (sensu Bullock et al., 1995), también llamada bosque tropical caducifolio (sensu Rzedowski, 2006) o selva baja caducifolia (sensu Miranda y Hernández, 1963) ocupaba originalmente 33.5 millones de hectáreas, según la carta de vegetación potencial para México elaborada por el Instituto Nacional de Estadística y Geografía (Challenger y Soberón, 2008). Este ecosistema ha presentado altas tasas de deforestación y degradación debido a actividades antropogénicas (Trejo y Dirzo, 2000). ...
Antecedentes y Objetivos: La selva estacionalmente seca requiere de acciones de restauración dadas sus altas tasas de deforestación. Para su restauración se ha sugerido el uso de la siembra directa, que se refiere a la colocación de semillas directamente en el suelo. El objetivo de este trabajo fue evaluar el éxito de la siembra directa de semillas de árboles de nueve especies nativas.
Métodos: La emergencia se evaluó durante 30 días y la sobrevivencia después de un año para cuatro especies sucesionales tempranas y cinco tardías sembradas en hábitats con distinta cobertura de hierbas y árboles en dos áreas bajo restauración en Morelos y Puebla, México.
Resultados clave: Las especies más exitosas por su emergencia y sobrevivencia de plántulas fueron las sucesionales tempranas: Spondias purpurea (16.79%) en El Limón y Senegalia macilenta (20.38%) en Teotlalco; el resto de las especies presentaron porcentajes de éxito de <10%. En ambas localidades, el estatus sucesional de las especies no explicó el porcentaje de emergencia. La cobertura de hierbas y árboles favoreció la emergencia de las especies tardías, mientras que las tempranas no respondieron a la cobertura; lo opuesto se observó con la sobrevivencia de las plántulas: las tardías no respondieron a los cambios en la cobertura vegetal.
Conclusiones: La mayor mortalidad de plántulas se registró en los sitios sin intervención de restauración, debido en parte a la falta de cobertura vegetal. Dado que el éxito de las especies por estatus sucesional y entre coberturas fue altamente variable, se recomienda: 1) usar distintas combinaciones de semillas de especies tempranas y tardías para la siembra directa bajo coberturas contrastantes, 2) establecer una cobertura con árboles de rápido crecimiento bajo la cual se siembren las semillas de especies que se benefician de la sombra y, 3) favorecer la sucesión natural para aumentar el éxito de la siembra directa
... Wa r m y e a r-r o u n d , t h e w o r l d 's t r o p i c s v a r y considerably in their seasonal rainfall patterns (Bailey, 1983). Variation in the volume and timing of tropical rainfall patterns produces diverse ecosystems, including tropical rainforests, tropical woodlands and tropical savannahs (Bullock et al., 1995). Where annual rainfall is lower in volume and concentrated over the summer (i.e. the wet-dry tropics), woodlands and savannahs are the dominant tropical ecological vegetation communities (Taylor & Tulloch, 1985;Shine & Brown, 2007). ...
Terrestrial animals in global wet-dry tropical ecosystems experience year-round high temperatures but concentrated summer rainfall. This highly seasonal precipitation is expected to have major evolutionary and ecological consequences for animals. We considered how strong seasonal patterns of rainfall might influence the environment and biological attributes of the world’s largest predatory lizard, the Komodo dragon (Varanus komodoensis). We predicted that annual variation in rainfall or temperature may influence the seasonal phenology of vegetation, and in turn, the phenology of Komodo dragon reproduction and hatchling emergence. Similarly, seasonal environmental differences may affect Komodo dragon rates of somatic growth, body condition, survival and daily movement. Our results indicated evidence of strong seasonal variation in mean monthly rainfall and leaf area index for open deciduous forest and closed dense forest. These environmental variables were significantly correlated with female Komodo dragon nesting activity and hatchling emergence. Neither Komodo dragon somatic growth rate nor body condition exhibited seasonal differences. There was, however, increased daily movement rates of Komodo dragons during the dry season. This suggests dry season associated life-history activities or thermoregulatory efficiency might explain increased daily movement. Ultimately, the Komodo dragon showed differential sensitivities in its biology to seasonal environmental variation.
... Tropical Dry Forests (TDFs), found between 23.5°North and South in areas where annual rainfall ranges from 250 to 2000 mm with a marked dry season of at least five to six months (Murphy and Lugo, 1986;Bullock et al., 1995;Miles et al., 2006), are adapted to uniquely challenging environmental conditions. TDFs occur under the 'Aw' and 'BSh' Köppen-Geiger classification, and the limited amount and seasonality of rainfall strongly influence species distribution, tree phenology, structure, and species-specific adaptations to survive in water limited environments (Borchert, 1994;Schwinning and Ehleringer, 2001;Kennard, 2002;Borchert et al., 2004;Pennington et al., 2009;Sanchez-Azofeifa et al., 2013;Horstman, 2017). ...
Millions of people depend on ecosystem services provided by Tropical Dry Forests (TDFs), yet their proximity to population centers, seasonally dry climate, and the ease at which they are converted to agriculture has left only 10 % of their original extent globally. As more TDFs become protected, basic information relating TDF age to subsurface water resources will help guide forest recovery. Severe deforestation and recent reforestation around Bahía de Caráquez, Ecuador produced a mosaic of different successional stages ideal for exploring relationships between TDF age, subsurface water availability and species-specific responses to seasonal drought. Over one year, we measured gravimetric water content, predawn and midday leaf water potential, and the stable isotope composition of xylem and source waters in two regenerating and one primary forest. Over the transition from wet to dry season, we discovered a sharper decrease in predawn water potential in younger successional forests than in the primary forest. Growing in degraded subsurface environments under increased competition, successional forest trees accessed deeper sources of moisture from unsaturated weathered bedrock and groundwater through the dry season; however, different species employed distinct water use strategies. Ceiba trichistandra maintained midday water potentials above −1.27 MPa through a drought avoidance strategy dependent on groundwater. Sideroxylon celastrinum tolerated drought by lowering predawn and midday water potential through the early dry season but took up greater proportions of saprolite moisture and groundwater as the dry season progressed. Contrastingly, Handroanthus chrysanthus maintained access to shallow soil and saprolite moisture by dropping midday water potential to −4.30 MPa, reflecting drought tolerance. Our results show that limited subsurface water resources in regenerating TDF's lead to species-specific adaptations reliant on deeper sources of moisture. The recovery of soil and saprolite hydrologic properties following disturbances is likely to exceed 100 years, highlighting the importance of forest conservation.
... Previous research on δ 13 C and δ 15 N in coca (Erythroxylum coca) from South America found significant isotopic differences among sample sites and attributed it to differences in soil (for δ 15 N) and length of the wet season (for δ 13 C) (Ehleringer et al. 2000). Soil characteristics, particularly soil water availability and nutrients (Medina et al. 1995;Oliveira-Filho et al. 1998), have also been shown to have an impact on tree growth in dry forests (Toledo et al. 2011), and it is therefore likely to influence wood isotopic composition. This impact shows a spatial gradient (Murphy and Lugo 1986;Ceccon et al. 2006) that progressively shifts in wetter forests where light variation is more important for growth (Engelbrecht et al. 2007;Brienen et al. 2010). ...
With increasing concerns about sustainable exploitation of tropical timber, there is a need for developing independent tools to check their origin. We evaluated the potential of tree-ring stable isotopes for identifying four Cedrela species (C. balansae, C. fissilis, C. odorata, and C. saltensis) and for identifying geographic origin of C. fissilis and C. odorata, two of the most intensively exploited species. We studied differences in 13C and 18O of wood among 11 forest sites (163 trees). We quantified isotope composition of 10-year bulk samples, and for a subset we also evaluated isotopic annual fluctuations for the last 10 years. Although annual isotopic variability was not correlated to precipitation or elevation, we found a significant relationship between the 10-year bulk stable-isotope composition and average precipitation and elevation. However these relationships were not consistent across all sites. We also explored isotopic site and species differentiation using Kernel Discriminant Analyses. Site discrimination was low: 30% accuracy for C. odorata, and 40% for C. fissilis sites. However, species discrimination was 57.5% for C. odorata and 95.3% for C. fissilis. These results suggest that although 13C and 18O isotopic analyses hold potential to verify species identification, discrimination of geographical origin within a country may still be challenging.
... Wa r m y e a r-r o u n d , t h e w o r l d 's t r o p i c s v a r y considerably in their seasonal rainfall patterns (Bailey, 1983). Variation in the volume and timing of tropical rainfall patterns produces diverse ecosystems, including tropical rainforests, tropical woodlands and tropical savannahs (Bullock et al., 1995). Where annual rainfall is lower in volume and concentrated over the summer (i.e. the wet-dry tropics), woodlands and savannahs are the dominant tropical ecological vegetation communities (Taylor & Tulloch, 1985;Shine & Brown, 2007). ...
Terrestrial animals in global wet-dry tropical ecosystems experience year-round high temperatures but concentrated summer rainfall. This highly seasonal precipitation is expected to have major evolutionary and ecological consequences for animals. We considered how strong seasonal patterns of rainfall might influence the environment and biological attributes of the world's largest predatory lizard, the Komodo dragon (Varanus komodoensis). We predicted that annual variation in rainfall or temperature may influence the seasonal phenology of vegetation, and in turn, the phenology of Komodo dragon reproduction and hatchling emergence. Similarly, seasonal environmental differences may affect Komodo dragon rates of somatic growth, body condition, survival and daily movement. Our results indicated evidence of strong seasonal variation in mean monthly rainfall and leaf area index for open deciduous forest and closed dense forest. These environmental variables were significantly correlated with female Komodo dragon nesting activity and hatchling emergence. Neither Komodo dragon somatic growth rate nor body condition exhibited seasonal differences. There was, however, increased daily movement rates of Komodo dragons during the dry season. This suggests dry season associated life-history activities or thermoregulatory efficiency might explain increased daily movement. Ultimately, the Komodo dragon showed differential sensitivities in its biology to seasonal environmental variation.
... The large proportion of infertile TDF soils have low nutrient, particularly P availability, which may constrain plant and microbial growth, as with heavily weathered soils in humid tropical forest biomes [54,55]. On the other hand, the frequent suggestion in the literature that TDFs are developed on fertile soil seems to be influenced by the soil properties of the Neotropical biogeographic domain, where TDF ecosystems have been extensively studied (see efforts of synthesis in [5,52,[56][57][58][59]). ...
Pantropical variation in soils of the tropical dry forest (TDF) biome is enormously high but has been poorly characterized. To quantify variation in the global distribution of TDF soil physical and chemical properties in relation to climate and geology, we produced a synthesis using 7500 points of data with gridded fields representing lithologic, edaphic, and climatic characteristics. Our analyses reveal that 75 TDF ecoregions across five biogeographic domains (Afrotropical, Australasian, Indo-Malayan, Neotropical, and Oceanian) varied strongly with respect to parent material: sediment (57%), metamorphic (22%), volcanic (13%), and plutonic (7%). TDF ecoregions support remarkably high variability in soil suborders (32), with the Neotropical and Oceanian realms being especially diverse. As a whole, TDF soils trend strongly toward low fertility with strong variation across biogeographic domains. Similarly, the exhibited soil properties marked heterogeneity across biogeographic domains, with soil depth varying by an order of magnitude and total organic C, N, and P pools varying threefold. Organic C and N pool sizes were negatively correlated with mean annual temperature (MAT) and positively correlated with mean annual precipitation (MAP). By contrast, the distribution of soil P pools was positively influenced by both MAT and MAP and likely by soil geochemistry, due to high variations in soil parent material across the biogeographic domains. The results summarized here raise important questions as to how climate and parent material control soil biogeochemical processes in TDFs
... Approximately half of the tropical forests are seasonally dry tropical forests (SDTFs); they range from open scrub vegetation rich in succulent plants and deciduous trees to patches of mesic forests, particularly along rivers, mountain slopes, and peaks (Muscarella et al., 2019;Pennington et al., 2009;Prado, 2003). The specific characteristics of forests in different regions depend mainly on the historical length of dry periods and local conditions related to the water availability (Allaby, 2006;Bullock et al., 1995;Moore, 2008). ...
The patterns of the spatial distribution of insects in seasonally dry tropical forests (SDTFs) are strongly influenced by marked seasonal fluctuations. Tropical arthropod seasonality has been linked to multiple factors, ranging from microclimate changes to large‐scale environmental processes. The group of social wasps includes eusocial organisms that play essential roles in ecosystems, acting as pollinators and predators. This study examines the variation in abundance and species richness according to season, rainfall, and temperature in an area of the Caatinga biome in northeastern Brazil, which has distinct vegetation characteristics. Four years of continuous sampling with Malaise traps constituted the medium‐term data used in our study. During dry seasons, populations of xerophytic vegetation experienced significant decreases in abundance, which were associated with decreased rainfall; however, we did not observe the same effect in evergreen vegetation. Mesic habitats have less variation in food resources, which may have kept populations active during droughts. However, during wet periods, especially after heavy rainfall, more individuals were recorded in the xeric area compared with the mesic area. Using results from social wasp populations, we conclude that the spatio‐temporal dynamics of insects in forest areas with seasonal characteristics are greatly affected by factors such as the landscape composition and mainly by the distribution of rainfall.
Abstract in Spanish is available with online material.
... Tropical deciduous forests have a diverse character, owing to increased species richness, varied species associations, uneven stem densities, and base cover, multistory canopy architecture, and various microclimatic conditions [2]. Tropical deciduous forests are regarded as ecosystems rich in species diversity and diverse forms of life [3], have unique plant communities, and are some of the most endangered ecosys-tems in the tropics [4]. ...
... Tropical deciduous forests have a diverse character, owing to increased species richness, varied species associations, uneven stem densities, and base cover, multistory canopy architecture, and various microclimatic conditions [2]. Tropical deciduous forests are regarded as ecosystems rich in species diversity and diverse forms of life [3], have unique plant communities, and are some of the most endangered ecosys-tems in the tropics [4]. ...
... 4 Soil moisture content acts as one of the determining factors, affecting plant species diversity and dispersion in dry forests. 5,6 In addition, plants of dry forests are largely subjected to water stress during dry period of the year. 7,8 Dry forests tends to have moderate to high plant species richness and diversity. ...
A forest tree inventory study was conducted in Vallanadu Black buck sanctuary, Tuticorin. The current study was conducted to assess tree density, species richness, basal area (BA) and aboveground biomass (AGB) stockpile. The study area has been classified as Southern Thorn Forest (SFT). One hundred square plots (total area 1 ha), each 10m × 10m (100 m2 each) laid randomly across study area. All live trees with ≥5 cm diameter at breast height (DBH) measured at 137 cm above the ground. As the whole, 1335 individual trees ≥5cm DBH recorded. A total number of 18 species recorded from 14 genera and 11 families in study area. The family Mimosaceae has maximum number of species (7 species) followed by Rhamnaceae (2 species), while 9 families had just single species’ each. The total basal area recorded was 22.046 m2 ha-1, while, the mean wood density (WD) of trees estimated as 0.70±0.093 g cm-3. Total amount of 50.065 Mg ha-1 present in STF. The contribution of different species in terms of total AGB varied significantly. Commiphora berryi stocked 45.13% (22.588 Mg ha-1) of AGB followed by A. planifrons (23.31%, 11.669 Mg ha-1), A. mellifera (7.233%, 3.621 Mg ha-1), whereas remaining 15 species collectively stocked 24.327% (12.187 Mg ha-1) AGB. The STF had a large number of trees compared to some dry forests within Tamil Nadu. Southern Thorn Forest endowed with a moderate number of trees species. Aboveground biomass stockpile of trees is comparable with the range recorded from Indian dry forests. The study area experiences lesser mean annual rainfall and >6 months dry season. Further, endowed with short-bole and smaller leaved trees, hence stocked a relatively lesser AGB in trees.
... Although the Neotropical dry forests of the American continent are distributed over a large area, that distribution is discontinuous, which has likely promoted the evolution of very high species richness and endemism among many different biotic groups (Banda et al., 2016;Bullock et al., 1995;Ceballos et al., 2010;Dirzo et al., 2011;Pennington et al., 2006;Prieto-Torres et al., 2018). Biogeographic patterns show strong structure, which has led to the recognition of different biotic ecoregions that largely match the main dry forest patches (see Olson et al., 2001). ...
en The Mesoamerican dry forests (MDF), rich in species and in endemic taxa, are distributed nearly continuously nearly continuously along the American Pacific slope from Mexico to Costa Rica; however, several of the bird species inhabiting the MDF show clear phenotypic differentiation recognized through the description of subspecies. There are two currently recognized species of magpie-jays of the genus Calocitta (Corvidae) distributed throughout the MDF: the monotypic black-throated magpie-jay (C. colliei) and the polytypic white-throated magpie-jay (C. formosa). These two species have sometimes been considered conspecific and have been reported to hybridize in sympatric areas, where birds with intermediate plumage characters are recorded. Using mitochondrial and nuclear DNA markers from individuals of the two species, we analyze the phylogeographic structure and the genetic diversity within Calocitta under an isolation with migration (IM) model. The results showed strong genetic structure, in which the two currently recognized species and some of the C. formosa subspecies grouped into four well-supported and reciprocally monophyletic clades. IM analyses suggested divergence dates for the split between C. colliei and C. formosa that were congruent with geological factors, as well as with the deep divergence of the three lineages within C. formosa. These factors likely led to a dynamic demographic history in all lineages. We also found strongly limited gene flow, null or near null migration values, and large genetic fixation and genetic distance values. We suggest that the strong genetic differentiation between lineages is the result of allopatric differentiation with later secondary contact, further supporting a highly dynamic biotic history in MDF.
Resumen
es Los bosques secos Mesoamericanos (MDF) son ricos en especies y están distribuidos casi de manera continua a lo largo de la vertiente pacífica de México hasta Costa Rica; sin embargo, varias de las especies de aves que los habitan muestran clara diferenciación fenotípica, lo que se ha reconocido a través de la descripción de subespecies. Existen dos especies actualmente reconocidas de urracas del género Calocitta (Corvidae) que se distribuyen en los MDF: la monotípica Urraca Hermosa Carinegra (C. colliei) y la politípica Urraca Hermosa Cariblanca (C. formosa). Estas dos especies a veces han sido consideradas conespecificas y se ha reportado que hibridizan en áreas de simpatría, donde se han registrados individuos con caracteres intermedios de plumaje. Usando marcadores de DNA mitocondrial y nuclear para individuos de ambas especies, analizamos la estructura filogeográfica y la diversidad genética dentro de Calocitta bajo un modelo de Aislamiento con Migración (IM). Los resultados muestran una fuerte estructura genética, en la cual las dos especies reconocidas y algunas de las subespecies de C. formosa se agrupan en cuatro clados bien soportados y recíprocamente monofiléticos. Los análisis de IM sugieren fechas de divergencia para la división entre C. colliei y C. formosa que son congruentes con factores geológicos, al igual que para las tres divergencias profundas entre los linajes dentro de C. formosa. Esos factores posiblemente llevaron a una historia demográfica dinámica en todos los linajes. También encontramos flujo génico muy limitado, valores de migración nulos o casi nulos, y valores altos de fijación y distancia genéticas. Sugerimos que esa fuerte diferenciación genética es el resultado de diferenciación alopátrica con posterior contacto secundario, apoyando aún más una historia biótica altamente dinámica en los MDF.
... Gentry, 1942(A.H. Gentry, , 1946 Heterogenous forest of canyon and valley (Leavenworth, 1946) Bosque tropical deciduo (Leopold, 1950;Rzedowski & McVaugh, 1966) Selva baja decidua (Miranda, 1952) Shrubby tree jungle (Turner, 1960) Selva baja caducifolia (Miranda & Hernández-X., 1963) Forêt tropicale basse caducifoliée (Puig, 1974) Bosque tropical caducifolio (Rzedowski, 1978) Tropical dry forest (A.H. Gentry, 1982) Bosque tropical estacionalmente seco (Bullock et al., 1995;Villaseñor & Ortiz, 2014) Selva tropical estacionalmente seca Trejo & Dirzo, 2002) Estructura y composición ...
La transformación drástica y profunda del entorno natural –junto con sus consecuencias indeseables– es uno de los problemas actuales más apremiantes que afrontamos como sociedad. En busca de alternativas para lograr la integridad de los sistemas sociecológicos a largo plazo, exploramos la capacidad de los sistemas agroforestales tradicionales (SAFT) para mantener la vegetación nativa de la selva tropical estacionalmente seca, al mismo tiempo que brindan múltiples contribuciones que ayudan a satisfacer algunas necesidades humanas fundamentales. Realizamos un estudio en el que se combinaron abordajes provenientes de ciencias ecológicas y sociales para responder a las siguientes preguntas de investigación: ¿En qué medida los SAFT son capaces de mantener la vegetación silvestre y de proveer contribuciones para las personas? y ¿Cuáles son las motivaciones de los campesinos para mantener la vegetación silvestre dentro de sus parcelas agrícolas? Realizamos el estudio en tres comunidades de la región de La Cañada, en el Valle de Tehuacán-Cuicatlán, Oaxaca, México. Allí se realizaron nueve muestreos de vegetación para registrar la cobertura forestal mantenida por las y los campesinos en sus SAFT –mediante la implementación de prácticas agroforestales– y compararla con nueve muestreos de la vegetación nativa circundante de selva seca. También hicimos colectas etnobotánicas y tomamos fotografías para documentar los valores de las plantas al mostrarlas a los habitantes. Estimamos los números equivalentes de especies como medidas de la diversidad “verdadera” en los SAFT y la vegetación silvestre, con el fin de comparar ambos escenarios. Para identificar las principales motivaciones de los campesinos para mantener la vegetación, hicimos un análisis cualitativo a partir de entrevistas semiestructuradas con las y los campesinos que manejan los SAFT que estudiamos. Asimismo, realizamos dos talleres con los habitantes de las comunidades, observación participante, charlas informales y registro de notas de campo. Encontramos que los SAFT analizados son capaces de mantener –en promedio– 44% de la cobertura forestal, 68% de las especies (30% de ellas endémicas de México), y 53% de los individuos de plantas perennes nativas de la selva seca. En los SAFT se encontraron 96 especies de plantas útiles (73% del total registrado). La información obtenida confirma la notable capacidad de los SAFT para resguardar la biodiversidad. Por otra parte, el número total de especies registradas en los sitios de selva seca y SAFT fue similar (98 y 101 especies, respectivamente), así como los números equivalentes de especies o comunidades estimados para la diversidad alfa (19.92 y 16.08 especies), beta (2.96 y 3.10 comunidades) y gamma (56.03 y 49.89 especies, respectivamente). Sin embargo, encontramos diferencias significativas en la abundancia de individuos (t = 3.414; p = 0.001), pues registramos en promedio casi el doble de individuos presentes en la selva seca (191) en comparación con los SAFT (101). El elevado recambio de especies (diversidad beta) que registramos tanto en la selva seca (72%) como en los SAFT (74%) tiene implicaciones muy relevantes para la conservación, sugiriendo que es necesario mantener varios sitios para conservar la diversidad regional de la vegetación silvestre. Aquí, la agricultura campesina ha resguardado la biodiversidad dentro de los SAFT. Por lo cual, consideramos que la justa valoración y el rescate del manejo campesino agroecológico podría formar parte primordial de las directrices de conservación. Además, identificamos que la obtención de múltiples contribuciones benéficas –que ayudan a satisfacer algunas necesidades fundamentales– representa el motivo principal de las y los campesinos para mantener componentes de la vegetación nativa –de selva seca– dentro de sus parcelas agrícolas. Estas contribuciones benéficas de la vegetación representaron la mayor parte de las contribuciones registradas (83%), mientras que solo un 17% fueron contribuciones perjudiciales. Sin embargo, estas últimas suelen tener una importancia notable para los campesinos, ya que pueden comprometer la producción agrícola (sobre todo al competir con sus cultivos por espacio, luz, agua y/o nutrientes). Al considerar que muchos campesinos viven en condiciones precarias, es razonable que las contribuciones perjudiciales de la vegetación puedan superar las contribuciones benéficas y generar una motivación determinante para eliminar la selva seca. Asimismo, dentro de las contribuciones benéficas encontramos que las contribuciones materiales son las más comunes (62%), en particular frutos comestibles, plantas medicinales, forraje y leña. Le siguen las contribuciones reguladoras (20%) como provisión de sombra, aporte de fertilidad al suelo, atracción de lluvia y mantenimiento de humedad; y las contribuciones inmateriales (18%) como fuente de sabores regionales e identitarios, plantas ornamentales, ceremoniales y rituales. Todas estas contribuciones de la vegetación al bienestar de las personas ayudan primordialmente a satisfacer necesidades fundamentales de subsistencia, protección e identidad, aunque también cubren en menor medida necesidades de afecto, entendimiento, creación, participación y ocio. Con lo cual podemos asumir que existe una relación directa entre el número de contribuciones benéficas y la posibilidad de satisfacer necesidades humanas fundamentales. En este contexto, los SAFT ilustran la importancia de valorar y mantener prácticas de manejo tradicional y relaciones sociedad-naturaleza más armónicas. Pues estas expresiones –de la agricultura campesina– son capaces de conservar la biodiversidad al mismo tiempo de satisfacer necesidades esenciales. Por ello, la continuidad, rescate, mejoramiento y promoción de los SAFT podría ser una alternativa viable para conciliar la conservación de diversidad biocultural, el bienestar humano y el cuidado de la naturaleza.
... Kenya National park from human disturbances such as logging, livestock grazing and wood fuel harvesting. The undisturbed plant community structure in these sites may reflect the influence of the natural, physical and chemical environment of the plant communities present as described by [35]. Tropical forests such as the Mt. ...
Os ambientes serranos do semiárido do Brasil se mostram, em sua grande maioria, como ambientes de cobertura vegetal conservada ou em estágio de sucessão ecológica avançado, o que lhes confere uma maior diversidade florística e estrutural. Diante do contexto de complexidade fitogeográfica em que estes ambientes se associam, esta pesquisa teve como objetivo classificar as unidades fitoecológicas do maciço Serra João do Vale (RN/PB). A classificação dos usos e coberturas da terra foi realizada com auxílio do software Ecognition Developer (Trimble®), assim como com a coleta de dados primárias in situ, onde foram anotadas as espécies-chave que caracterizam cada unidade fitoecológica e descritos os padrões de distribuição da cobertura vegetal. Identificou-se que a área apresenta 02 fitofisionomias predominantes: caatinga e floresta tropical sazonalmente seca. As fitosionomias encontradas são condicionadas tanto por fatores ambientais como pela intervenção humana, gerando padrões complexos de distribuição, algumas vezes não havendo tendências, onde a aleatoriedade é proeminente. Foram identificadas 02 unidades fitoecológicas da caatinga e 04 da floresta, sendo esta última restrita a áreas com menor extensão nas zonas mais elevadas e cercadas por trechos de declividade acentuada.
Uraniferous Province of Lagoa Real is the most important monomineralic province in Brazil, located in the Center‐South Region of the State of Bahia and covering the municipalities of Caculé, Caetité, Lagoa Real, and Paramirim. Uranium is normally found in very low concentrations in rocks, soils, waters, and the atmosphere, but can occur in concentrations that pose a risk to human health. The dispersion of radionuclides in the environment is complex and occurs due to natural (leaching, erosion, and soil–plant–animal transfer) and anthropogenic factors, such as minings. The chapter discusses the importance of understanding biogeochemical processes, migration trajectories, and exposure routes of uranium and other radionuclides to plants, animals, and human populations, contextualizing regional radiometric anomalies and monitoring locus. A critical review of research carried out in the uranium province is carried out, proposing a conceptual map for carrying out integrated studies.
Environmental stress as a consequence of anthropic pressures can affect the physiological condition of animals and cause damage to their DNA. Multiple studies have shown genotoxic effects of different pollutants; however, to our knowledge, the impact of environmental stress on genetic damage has been scarce explored. In some stressful ecosystems, such as seasonally dry tropical forests, the combined effects of anthropogenic activities and ongoing global changes cause increased environmental stresses that could trigger physiological and genetic effects on biodiversity. In this study, we evaluated the changes in the prevalence of genotoxic damage to birds in three states of forest degradation in the Tumbesian Region of Western Ecuador. We used the blood samples of 52 bird species to determine the frequency of micronucleus and nuclear abnormalities in the erythrocytes. Our results showed a significant effect of forest degradation in the proportion of micronucleus and nuclear abnormalities at the community level, localities with higher degradation showed higher levels of abnormalities. However, when analyzing the dominant species, we found contrasting responses. While Amazilis amazilia and Lepidocolaptes souleyetii showed a reduction in the proportion of nuclear abnormalities from the natural to shrub-dominated localities, Troglodytes aedon and Polioptila plumbea showed an increase. We concluded that the degradation process of these tropical forests increases the stress on the bird community generating genotoxic damage to the bird community. Bird responses seem species-specific, which could explain the differences in changes in bird composition reported in other studies.
Dispersal influences many key aspects of plant ecology at both fine- and broad scales. However, dispersal events are challenging to quantify as they are difficult to observe and measure accurately, despite the importance of understanding species’ dispersal capacity. In this study, we quantified dispersal estimates for the dominant vascular flora of sub-Antarctic Marion Island, using a mechanistic model to estimate dispersal potential via anemochory and standardised experiments that simulate dispersal events via zoochory, human activity, and thalassochory, to test if dispersal capacity correlates to contemporary range expansion of the island’s native and alien species. Our results demonstrate the broad range of dispersal potential in the island’s flora and represent the first quantification of the dispersal potential (via multiple vectors) of the dominant vascular flora in the sub-Antarctic. Dispersal potential was not related to range expansion rates of native or alien species, suggesting that other mechanisms are responsible for the variation observed in species range expansion rates. Although this finding contradicts expectations and evidence from some other studies, it is consistent with research conducted in alpine regions (which may be climatically and physiognomically similar to this sub-Antarctic study site) where factors such as demography and competition are more important predictors of species range expansion than their dispersal ability, dispersal syndromes, or dispersal-related traits.
Avecennia marina is potential mangrove plant and it exhibits high CO 2 accumulation, rapid growth with high biomass and significant carbon storage in soil than other mangroves. The present study conducted to imply the carbon sequestration potential of mangrove along with their biomass and sediment characteristics for the year 2017. The study was conducted on natural stand of Avicennia marina at Pichavaram mangrove forest in Southeast coast of India. To highlight the significance of mangroves a comparative carbon stock assessment was made on natural stand of Avicennia marina , and with the non-mangrove barren habitat. The analysed parameters are leaf area index, net canopy photosynthesis, biomass, biomass carbon and soil characteristics such as, total organic carbon, total carbon, temperature, pore water salinity, moisture, bulk density, soil texture, nitrogen, phosphorous and potassium. The average measured value of leaf area index and net canopy photosynthesis were 1.66m ² /m ² , and 6.03 gC/m ² . The level of nitrogen, phosphorous, potassium (NPK) were higher in A. Marina when compared to non-mangrove barren site. One way ANOVA was conducted for the soil sediment characteristic observed for the both site and no significant variation was observed except particle density, soil clay, loss of ignition and available potassium and phosphorous. In correlation analyses significant positive correlation was observed with temperature and soil while soil silt had negative correlation with bulk density, pore space, soil sand and clay. Temperature and sand content was lower than that of barren habitat. Soil moisture, bulk density, particle density, pore space, pore water salinity, soil silt and clay content showed higher value in mangrove soil than that of barren habitat. The present investigation revealed the total organic carbon (TOC) and total carbon (TC) was 7 fold higher in A . marina when compared to barren habitat.
The spatial distribution of aquatic plants can be influenced by dispersal capacity, and local abiotic factors. In general, aquatic plants are widely distributed and have a large‐scale ability to disperse. However, some groups have narrower tolerance and are more sensitive to local environmental variations. Thus, we investigated which factors explain the spatial distribution of growth forms in different seasonal pools in the Brazilian semi‐arid region. We hypothesized that if dispersal limitation is absent and pools have similar abiotic conditions, all pools must have communities with the same growth form pattern that fit together in the water column. Conversely, if the abiotic factors among pools differ significantly, there will be a higher frequency of certain growth forms associated with the most striking local factors. We found no relationship between growth form composition in pools and geographic distance (rM = −0.004; P = 0.96), indicating high dispersal capacity. Nonetheless, the pool showed different growth forms proportions, indicating that different abiotic factors affect each local. Additionally, the variation explained by the abiotic factors was higher than the distance. Nitrate, ammonia, cation exchange capacity and redox potential were the main environmental variables related to the presence of growth forms. Helophytes and bottom‐rooted emergent hydrophytes were positively associated with nitrate and redox potential, whereas bottom‐rooted submerged hydrophytes were positively associated with ammonia. Unpredictably, free‐floating emergent hydrophytes were more frequent in pools with high cation exchange capacity. This association may come from a nutrient flux integrated system between soil and water. Our results suggest that the effect of abiotic factors is stronger than dispersal limitation on the growth forms composition in Brazilian semi‐arid pools, and the frequency of growth forms in each pool depends on the role most striking (or joint) of the local limnological and edaphic variables.
The genus Baccharis (Asteraceae) comprises over 440 species distributed along North and South America. Some species of this genus have remarkable invasiveness, and one of these species is the South American shrub Baccharis dracunculifolia DC. Most of the introductions of non-indigenous species are held indirectly through trade, so it is believed that this species could become invasive worldwide with a particular interest in the North American continent because of the increasing sale of products derived from honey to this continent. The resin extracted from B. dracunculifolia is the leading source for preparing the green propolis produced in Southeastern Brazil. Thus, the main objective of this work is to apply an approach based on distribution modeling to investigate possible areas of high environmental suitability for B. dracunculifolia in the North American continent and the potential to the entire globe using current and two future scenaries. Our results show many areas of environmental suitability for B. dracunculifolia. This species can invade over 33 countries distributed into five continents, including North America, some of the most critical parts of the southern USA, and large areas in Mexico. Since the best way of countering biological invasions is prevention, we propose that the introduction of this species should be monitored.
Aim
Spatial patterns in resource supply drive variability in vegetation structure and function, yet quantification of this variability for tropical dry forests (TDFs) remains rudimentary. Several climate‐driven indices have been developed to classify and delineate TDFs globally, but there has not been a climo‐edaphic synthesis of these indices to assess and delineate the extent of TDFs. A statistical climo‐edaphic synthesis of these indices is therefore required.
Location
Pantropical.
Time period
Modern.
Major taxa studied
Vascular plants.
Methods
We assembled most known prior descriptions of TDFs into a single data layer and assessed statistically how the TDF biome, which we call tropical dry landscapes (TDLs) composed of forest and non‐forest vegetation, varied with respect to the normalized difference vegetation index (NDVI) sensed by MODIS (250 m pixel resolution). We examined how the NDVI varied with respect to mean annual temperature (MAT) and rainfall (MAR), precipitation regime, evapotranspiration and the physical, chemical and biological properties of TDL soils.
Results
Overall, the NDVI varied widely across TDLs, and we were able to identify five principal NDVI categories. A regression tree model captured 90% of NDVI variation across TDLs, with 14 climate and soil metrics as predictors. The model was then pruned to use only the three strongest metrics. These included the Lang aridity index, total evapotranspiration (ET) and MAT, which aligned with identified NDVI thresholds and accounted for 70% of the variation in NDVI. We found that across a global TDL distribution, ET was the strongest positive predictor and MAT the strongest negative predictor of the NDVI.
Main conclusions
The remote sensing‐based approach described here provides a comprehensive and quantitative biogeographical characterization of global TDL occurrence and the climatic and edaphic drivers of these landscapes.
Gene dispersal processes shape demographic and microevolutionary dynamics of tree species. Gene dispersal patterns can be studied by spatially explicit methods. Spatial genetic structure (SGS), summarized in the Sp statistic, provides indirect estimates of gene dispersal across generations for a known or assumed population effective density. Sp is modulated by exogenous and endogenous factors including the mating system that can be assessed using outcrossing rates (tm). Knowledge on tm and Sp are particularly important for the conservation of species in fragmented biomes such as seasonally dry tropical forests (SDTF). The main aim of this review was to evaluate putative drivers of Sp and tm, and their consequences for gene dispersal in tree species from SDTF. We reviewed 59 genetic studies on SDTF tree species published between 2000 and 2020 and extracted data on propagule dispersal, successional stages, seasonality, mating system, population density, landscape features, type of molecular markers, pairwise kinship in the first distance class (F1), Sp statistic, mean gene dispersal distance (σg), and multilocus outcrossing rates (tm). Sp was significantly associated with the mating system where Sp(outcrossing) > Sp(mixed-mating), and population density where Sp was higher in high-density populations. Outcrossing rate was significantly associated with the type of propagule dispersal, where tm was higher in populations of plants pollinated by wind, and in those with animal-mediated seed dispersal, tm(zoochory) > tm(anemochory) > tm(autochory), and with successional stage where tm(late-successional) > tm(pioneer). These factors are relevant to inform management actions in conservation and restoration projects. Thus, the knowledge on the determinants of gene dispersal processes can help to rescue SDTF through sustainable management.
This review provides a revised and expanded word-formula system of whole-seed primary dormancy classification that integrates the scheme of Nikolaeva with that of Baskin and Baskin. Notable changes include the following. (1) The number of named tiers (layers) in the classification hierarchy is increased from three to seven. (2) Formulae are provided for the known kinds of dormancy. (3) Seven subclasses of class morphological dormancy are designated: ‘dust seeds’ of mycoheterotrophs, holoparasites and autotrophs; diaspores of palms; and seeds with cryptogeal germination are new to the system. (4) Level non-deep physiological dormancy (PD) has been divided into two sublevels, each containing three types, and Type 6 is new to the system. (5) Subclass epicotyl PD with two levels, each with three types, has been added to class PD. (6) Level deep (regular) PD is divided into two types. (7) The simple and complex levels of class morphophysiological dormancy (MPD) have been expanded to 12 subclasses, 24 levels and 16 types. (8) Level non-deep simple epicotyl MPD with four types is added to the system. (9) Level deep simple regular epicotyl MPD is divided into four types. (10) Level deep simple double MPD is divided into two types. (11) Seeds with a water-impermeable seed coat in which the embryo-haustorium grows after germination ( Canna ) has been added to the class combinational dormancy. The hierarchical division of primary seed dormancy into many distinct categories highlights its great diversity and complexity at the whole-seed level, which can be expressed most accurately by dormancy formulae.
Tropical dry forests (TDFs) have experienced pronounced droughts and increased temperatures for the last century. To assess whether these climatic shifts have influenced dry forest vegetation and ecosystem functioning, we integrated ground observations from a Costa Rican long‐term forest dynamics monitoring plot with remotely sensed measures of forest productivity and canopy functioning from a diverse set of satellite data. Previously reported long‐term climate data (1921–1997) show a reduction in annual rainfall, but since 1980 there has been no directional change in mean annual precipitation. However, the 2015 El Niño Southern Oscillation (ENSO)‐induced drought was unprecedented. Temperatures have increased by 1.1°C since 1931. However, the Landsat wet season (1987–2017) Enhanced Vegetation Index (EVI) (canopy greenness) and the dry season (1985–2017) fraction of non‐photosynthetic canopy cover all indicate that TDFs have become more deciduous but also more productive during the wet season. These changes are consistent with a shift in the functional composition observed in the long‐term plot as more drought‐deciduous tree species have increased in abundance. Nonetheless, more continuous 16‐d MODIS (the Moderate Resolution Imaging Spectroradiometer) measures of the EVI over the past 17 yr (2001–2017) showed no change in the total annual forest productivity. Further, while the 2015 ENSO event temporarily reduced forest EVI, it did not cause a longer‐term impact on forest productivity. Instead, high spatial resolution Worldview‐2 satellite imagery showed that forest phenology shifted in the subsequent years even though the region returned to normal precipitation. Our results indicate that while the species composition of TDFs may be sensitive to the long‐term trend of gradually increasing temperatures and aridity, the annual forest functioning has so far been resilient to long‐term drying and a large episodic extreme drought event. This study demonstrates the feasibility of synthesizing satellite images of different characteristics to study the vegetation dynamics of a long‐term forest dynamics plot. Our synoptically sensed results show that the longer‐term changing climate has been and is currently shifting the ecological functioning, and also provide a baseline to assess the impacts of an extreme drought year on TDFs.
Seed viability is a crucial factor affecting the regeneration potential of seeds, but there is little information on how this trait varies across habitats, populations, species, and higher taxonomic units, as well as on the relative contributions of evolutionary history and environmental factors to this trait. Here we evaluate the relative contributions of climatic variability and phylogenetic history to seed viability in a group of species of Bursera that belong to two distinct lineages (sections Bursera and Bullockia). We analyzed 39 seed lots from 11 species, comprising several populations and 2 years, and estimated embryo presence and viability in each lot. We examined spatial and temporal variation in viability and analyzed the relationship between this trait and water availability using regression models; the amount of phylogenetic signal in seed viability was also estimated. Mean seed viability was consistently low in species of section Bursera (mean 29.7%) and substantially higher in species of section Bullockia (mean 79.6%). A high proportion of unviable seeds were embryoless. Spatial and temporal variation in seed viability was significant but usually low among populations and species. The relationship between water availability and seed viability was not significant, but the amount of phylogenetic signal in seed viability was high and significant (λ = 0.74). There is a clear difference in seed viability among the two sections of Bursera . During the split of the two sections in the middle Eocene, the reorganization of the genome may have involved changes in fruit morphology associated with differences in parthenocarpy among them.
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