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Ecology of Tropical Dry Forest
Abstract and Figures
Dry tropical forests occur in frost-free areas where the mean annual temperature is >17oC, mean annual rainfall is 250-2000 mm, and the annual ratio of potential evapotranspiration to precipitation exceeds unity. The seasonality and variability in the climate of such regions is indicted. There is rather little floristic overlap between dry and moist forests, and the former are structurally much simpler. Primary productivity and leaf turnover are linked with soil moisture. Nutrient cycling is characterised: low within-stand efficiency of N use seems to be common. Comments are made on variation in reproductive and vegetative phenology. Dry forests are more vulnerable to stress during succession than are moist forests, and succession itself is slower, but the simpler structure of many mature dry forests permits a more rapid recovery following disturbance, ie dry forests are more resilient. Uses of dry forests by man are described, with attention focusing on shifting agriculture and the impact of fire.-P.J.Jarvis
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... The low number of herbaceous species richness may be attributed to the closed canopy cover of the forest patches in the study area. According to Friis (1986) and Murphy and Lugo (1986), herbaceous species cover is usually inversely proportional to canopy cover. That is closed canopy sites of forests have poor herbaceous cover and vice versa depending the amount of light penetration. ...
... The total basal area of woody species is generally in the range provided for tropical and subtropical dry and wet forests of the world (Murphy and Lugo, 1986). Moreover, the range of the total basal area of woody species in the forest patches of the study area was comparable to that of Moist evergreen Afromontane ...
The study was undertaken with the general objective of investigating the composition, diversity and structure of six forest patches in northwestern Ethiopia. Vegetation data were collected from 154 sampling plots of each 400 m 2 (20 m × 20 m). Species frequency, density, basal area, dominance, importance value index and population structure of the forest patches were analyzed using descriptive statistical tools. Floristic diversity and evenness were computed using Shannon diversity and evenness indices, respectively. The variations of floristic richness, density and basal area among the forest patches was tested using One-Way ANOVA in PAST software Package. The results of the study revealed that the study area harbored 212 species (122 woody and 90 herbaceous) belonging to 169 genera and 79 families. The Shannon diversity index and evenness values of the study area were 3.7 and 0.8, respectively. The highest number of species were recorded in Khatasa forest, followed by Bradi, Askunabo, Ambiki, Kidamaja and Degera forests. The density, basal area and dominance of woody species were 2172.1 stems ha-1 , 41.2 m 2 ha-1 and 23.1 m 2 ha-1 , respectively. There were no significant variations of floristic richness, density and basal area among the forest patches. A number of tree species showed unhealthy population structure and were found to be at conservation risk. To reverse these changes, among other measures, undertaking restoration activities using locally threatened woody species is highly recommended.
... According to this fnding, the foristic compositions indicate the presence of high species diversity in the study area (239 vascular plant species which belong to 76 families in 187 genera). Te existence of high species diversity in the study area could be due to the heterogeneity existing in diferent vegetation patches within the vegetation community [28], disturbance [29], and edaphic properties [30] and diference in the range of altitude [31]. Results from the hierarchical cluster analysis showed that fve plant community types were identifed. ...
The aim of the study was to determine plant community types and species distribution patterns and their relationships with environmental variables in Dabena woodland in western Ethiopia. A systematic sampling design was used. Representative and relatively homogeneous vegetation units of sampling sites were selected on the basis of physiognomy. Vegetation and environmental data were collected from a total of 92 plots (each 20 m × 20 m) which were placed at intervals of 200 m along the established transect lines. All vascular plant species in the plots were recorded. Floristic richness, diversity, evenness indices, and similarity of the plant communities were analyzed using R Package 3.2. Classification and ordination methods were used to describe community types and to examine the relationship between community type and environmental variables. Five plant communities were identified in the vegetation of Dabena woodland, namely, Clerodendrum myricoides-Vernonia hymenolepis, Erythrina brucei-Entada abyssinica, Combretum molle-Gardenia ternifolia, Galiniera saxifraga-Flacourtia indica, and Dracaena afromontana-Landolphia buchananii. All community types showed a high diversity index. The highest similarity coefficient was 0.49 between community types two and three, reflecting 0.51 dissimilarity in their species richness. Disturbance, altitude, CEC, phosphorous, OC, clay, and TN are the environmental factors that most influenced the distribution of the plant communities. The CCA diagram revealed that disturbance and silt strongly influenced the distribution of species in Clerodendrum myricoides-Vernonia hymenolepis community, Combretum molle-Gardenia ternifolia community, and Erythrina brucei-Entada abyssinica community. Altitude, clay, and total nitrogen axes strongly influenced the distribution of species in Galiniera saxifraga-Flacourtia indica and Dracaena afromontana-Landolphia buchananii community. Therefore, it can be concluded that some other environmental variables may influence the distribution of the plant communities, which needs to be further investigated.
... Los bosques secos son muy importantes, representan casi la mitad de los bosques tropicales y subtropicales del mundo, abarcan grandes áreas de África, América Latina y Asia Pacífico (Murphy & Lugo, 1986). Además, sustentan a millones de personas más pobres del mundo siendo la sabana boscosa africana la que proporciona medios de vida a más de 100 millones de personas de las áreas urbanas y rurales. ...
La investigación del enfoque espectral de las 86 especies vegetales del bosque seco en la región Piura, enriquece y contribuye significativamente el conocimiento que se tiene sobre el comportamiento de dichas especies vegetales de los ecosistemas de bosque seco en el norte del Perú, relacionado con el impacto del calentamiento global y eventos extremos en esta línea de investigación, contribuyendo en cierta medida con la información que se cuenta
actualmente. De manera especial, es importante resaltar la existencia de investigaciones preliminares en el tema, realizadas por importantes instituciones y organismos públicos y privados, entre las cuales se puede mencionar al Ministerio del Ambiente de Perú (MINAM), Servicio Nacional de Áreas Protegidas por el Estado (SERNANP), Servicio Nacional Forestal y de Fauna Silvestre (SERFOR), Servicio Nacional de Meteorología e Hidrología del Perú (SENAMHI), Ministerio de Desarrollo Agrario y Riego (MIDAGRI), entre otros; así como, los diferentes trabajos de investigación realizados en la academia, entre ellas la Universidad Nacional de Piura, Universidad Nacional de Lambayeque entre otras, los cuales han motivado al equipo de investigadores de la Universidad Nacional de Frontera (UNF) a asumir el reto y compromiso de convertirse en actores principales de investigaciones concernientes con la problemática del bosque seco especialmente en la región.
Finalmente, el presente trabajo sin lugar a duda contribuirá con información
fundamental para determinar la línea base en este tipo de problemática que afecta a los bosques secos en el norte del Perú; y, a partir de ahí, ampliar la perspectiva académica e investigativa para explicar la dinámica en el comportamiento de la cobertura espacial de las diferentes especies vegetales de los ecosistemas de bosque seco; de manera que ello, brinde herramientas necesarias y coadyuve en la toma de decisiones por parte de las autoridades involucradas en la propuesta de acciones de preservación, conservación y protección de dichos ecosistemas de bosque seco en la región Piura.
https://archivos.unf.edu.pe/uploads/Revista_Cientifica/Libro_BOSQUE_SECO.pdf
... They once made up 42% of the world's tropical regions, but currently only 2% of those forests remain (Buzzard et al., 2016). Across the tropics, the dry forest biome has attractive features for human use: they tend to be suitable areas for livestock and agriculture because their soils are often fertile and they possess a marked rainfall season, and they are favored for human development because the dry environment may reduce the risk of disease transmission (Murphy and Lugo, 1986;Portillo-Quintero et al., 2015). These global patterns hold true in Hawaiʻi; most original tropical dry forests in Hawaiʻi have been destroyed (Cordell and Sandquist, 2008) and they are continuously exposed to various threats, mainly due to human activity (Miles et al., 2006). ...
Premise
Competition from naturalized species and habitat loss are common threats to native biodiversity and may act synergistically to increase competition for decreasing habitat availability. We use Hawaiian dryland ferns as a model for the interactions between land‐use change and competition from naturalized species in determining habitat availability.
Methods
We used fine‐resolution climatic variables and carefully curated occurrence data from herbaria and community science repositories to estimate the distributions of Hawaiian dryland ferns. We quantified the degree to which naturalized ferns tend to occupy areas suitable for native species and mapped the remaining available habitat given land‐use change.
Results
Of all native species, Doryopteris angelica had the lowest percentage of occurrences of naturalized species in its suitable area while D. decora had the highest. However, all Doryopteris spp. had a higher percentage overlap, while Pellaea ternifolia had a lower percentage overlap, than expected by chance. Doryopteris decora and D. decipiens had the lowest proportions (<20%) of suitable area covering native habitat.
Discussion
Areas characterized by shared environmental preferences of native and naturalized ferns may decrease due to human development and fallowed agricultural lands. Our study demonstrates the value of place‐based application of a recently developed correlative ecological niche modeling approach for conservation risk assessment in a rapidly changing and urbanized island ecosystem.
... Lack of rainfall, high solar radiation, and low humidity are typical of the seasonal forests during the dry season, which cause changes in the physiognomy of the forest, a reduction in productivity and in the availability of resources for animals, resulting in a reduction of the biological activity (e.g.Pérez-García et al. 2012). As plant growth occurs mainly during the rainy season, the abundance and number of insect species increase during this period (Murphy and Lugo 1986;Pescador-Rubio et al. 2002). However, other vegetation processes, such as flowering, fructification, and seed dispersal occur in different periods during the year (Murphy and Lugo 1995;Pezzini et al. 2014). ...
We present the anatomical study of axes of the corystosperm Rhexoxylon piatnitzkyi and the interactions of this plant with wood-boring beetles. We used a CT scanner and thin sections to reconstruct the boring pattern inside the plant axes, as well as the tissues affected by the beetle. The galleries were abundant in the branch of R. piatnitzkyi, including both longitudinal and transverse borings, and less frequent in the trunks. The galleries are bored preferentially in the secondary phloem and in the pith. The position of the galleries as well as the cell and tissue composition of the frass indicates that the borer was mainly a corticophagous insect. The sample also presents evidence of white rot by lignivorous fungi, and fragments of tracheids can be recognised in the frass that fills the galleries, indicating that the borer had some capacity to feed on decayed wood. The anatomical features of the secondary xylem and phloem suggest that the plant deployed defence mechanisms against the fungal decay and/or the boring beetle. This is the first evidence of insect galleries in axes of corystosperms, a dominant group of plants during the Triassic in Gondwana, and the first possible record of cerambycid borings.
... Currently, less than 10% of SDTFs' original extent remains in the Americas and the Caribbean [11]. SDTFs are Plants 2024, 13, 1318 2 of 16 characterized by a strong seasonality consisting of two main seasons (rainy and dry); in some areas, the dry season could last up to six months and is tightly linked to its phenology [12][13][14][15]. This extreme seasonality plays a central role in modulating SDTF composition, structure, and function, making it an ecologically fascinating tropical ecosystem [11,16]. ...
Understanding the relationships between seed traits and germination responses is crucial for assessing natural regeneration, particularly in threatened ecosystems like the seasonally dry tropical forest (SDTF). This study explored links between seed traits (mass, volume, moisture content, and dispersal type), germination responses (germinability, germination speed (v¯), time to 50% of germination (T50), synchrony, and photoblastism), and physical dormancy (PY) in 65 SDTF species under experimental laboratory conditions. We found that species with smaller seeds (low mass and volume) had higher v¯ and reached T50 faster than species with larger seeds. For moisture content, species with lower moisture content had higher germinability and reached the T50 faster than seeds with high moisture content. Abiotic dispersed species germinated faster and reached the T50 in fewer days. Most of the SDTF species (60%) did not present PY, and the presence of PY was associated with seeds with lower moisture content. As for photoblastism (germination sensitivity to light), we classified the species into three ecological categories: generalists (42 species, non-photoblastic), heliophytes (18 species, positive photoblastic, germination inhibited by darkness), and sciadophytes (5 species, negative photoblastic, light inhibited germination). This study intends to be a baseline for the study of seed ecophysiology in the SDTF.
The life history aspects of dormancy of the weevil Anthonomus rufipennis LeConte (Coleoptera: Curculionidae) were studied a 57-month period in a seasonally dry tropical forest of central Mexico. Weevil populations and their physiological status were monitored on both the reproductive host tree, Senna polyantha (Collad.) H.S: Irwin & Barneby (Fabales: Fabaceae) and the highly favored refuge host, Tillandsia recurvata L. (Poales: Bromeliaceae) or “ball moss.” During the dry season, weevils were only found on the refuge host with a mean total density of 1.014 ± 2.532 individuals/ball moss (N = 1,681). Weevil densities on T. recurvata between early and late dry seasons were not significantly different, suggesting that dry season survival was relatively high. Weevils collected during these seasons revealed little reproductive development and relatively high-fat accumulation in both sexes. During 5 of 6 yr, densities of the weevils in T. recurvata dropped significantly during the early rainy seasons, when the reproductive host trees leafed out and began producing oviposition sites (flower buds). At this time, more males than females initially moved to vegetative trees and showed significant signs of reproductive development. Recolonization of ball moss by weevils began during the late rainy season when oviposition sites (flower buds) were still available. A proportion of the weevils remained on the reproductive host, suggesting that A. rufipennis is facultatively multivoltine. The methodologies and results of the study can serve as a model system for future studies of the dormancy of other insects in dry tropical forests and provide insight into the dormancy of other anthonomine weevils of economic importance.
Axial parenchyma proliferation (non-lignified parenchyma) in wood has been characterized for only a few species. In the present study, we characterized the proliferation, ontogeny, and seasonal variation of wood axial parenchyma in Cochlospermum vitifolium (Bixaceae). This study included material from natural populations from different sites in Mexico. We analyzed the wood anatomy and development in stems of different ages, and monthly sampling of the main stem during the growing season. The results show that the wood anatomy of C. vitifolium is characterized by features associated with efficient water transport, such as wide vessels and low vessel frequency. The wood has a high storage and radial transport capacity. Axial parenchyma is abundant and constitutes the main cell type of the wood. Rays are wide and tall with a high starch content. Ontogenetic development of the wood showed that non-lignified axial parenchyma differentiates after secondary growth has been established. Parenchyma proliferation does not occur in an axially orderly fashion and the results suggest that there is a relationship between maximum proliferation and precipitation. We found high variation in wood parenchymatization between trees. The maximum parenchymatization and succulence was found in trees with larger stem diameter. The ecological and ontogenetic implications of wood parenchymatization are discussed.
Biotic and anthropogenic disturbances are mediating changes in species diversity and vegetation composition in different regions of the world. Such changes may affect plant biomass allocation patterns in different tree components and vegetation types. To assess the impact of anthropogenic disturbances such as grazing, lopping, harvesting of non-wood forest products, fuel wood and fodder collections on biomass allocation to different components of the vegetation, two study sites i.e., one undisturbed site and the other a disturbed site located in the Barnawapara Wildlife Sanctuary, Chhattisgarh were selected. Biomass allocation was measured by placing ten (10 m × 10 m) quadrats randomly, at both the forest sites (i.e., disturbed and undisturbed). Based on the regression equations relating tree circumference to dry weight of components (viz., bole, branch, leaf, and root), biomass of different vegetation components (i.e., above- and below-ground) was measured. Total biomass (above- and below-ground, including herbaceous shoots and litter mass) was significantly (P < 0.05) higher on the undisturbed site (360.38 t ha−1) compared to the disturbed site (113.99 t ha−1). Among different above-ground components, most of the biomass was allocated to branches followed by bole and leaf. Above-ground biomass ranged between 76.47 and 270.87 t ha−1 with higher value at undisturbed forest site and the lower at the disturbed forest site. The below-ground biomass varied between 37.52 and 89.51 t ha−1, and like above-ground biomass it was also higher at the undisturbed forest site and lower at the disturbed forest site. A higher (~ 8%) biomass allocation to below-ground component was observed at the disturbed site, compared to the undisturbed site. Moreover, the proportion of biomass in the herb layer was higher at the disturbed site compared to the undisturbed site. Based on the results of present study, it can be concluded that under the disturbed conditions plants allocate major portion of the biomass to the below-ground and herbaceous components in the tropical dry deciduous ecosystems.
A study was conducted for one year to record live fuel moisture contents (LFMC) of dominant tree species of tropical thorn forest ecosystem in Tirunelveli, Tamil Nadu. Standard methods and protocols were followed for the sample collection, processes and analyses. The mean live fuel moisture values showed that all the dominant tree species of the tropical thorn forests possess high fire behaviour (LFMC values ranged from 101% to 125%). The LFMC had relationships with environmental factors (rainfall, temperature, humidity, rainy days, hours of sunlight availability). The tree species had the uppermost LFMC in the wettest month and the lowermost in the peak summer. The needs for further studies has been emphasized.
The forests to be considered in this chapter are roughly located between 23° on either side of the equator and are climatically characterized by high total annual insolation >4.5·105 J cm-2, and thermal regimes in which daily temperature oscillations are frequently more pronounced than seasonal average monthly differences. The magnitude of the seasonal differences in temperature increases towards higher latitudes from a climatic equator, by definition the belt with more homogeneous climate in which weather is most predictable (UNESCO 1978). Near the equator, rainfall is generally high (> 2,000 mm per year) and evenly distributed during the year, with seasonality increasing with one or two annual dry periods towards higher latitudes. Total amount of rainfall varies greatly within the tropics, and because of predominantly high potential evapotranspiration, there exists a great diversity of forest ecosystems regulated by water availability during the year. Altitude modifies average temperature and water availability, because mountain ranges change incidence of insolation and rainfall regime.
The area of Africa where woodland is dominant covers 12.1 percent, or 3.8 × 106 km2, of the land area (Malaisse et al., 1972). The main part of this area corresponds closely to the Zambezian Domain (White, 1965). In the vicinity of Lubumbashi miombo woodland comprises over 90 percent of the country; Brachystegia spp. and Julbemardia paniculata (Benth.) Troupin are the most dominant trees.
Ranging from lowland evergreen rain forest to alpine tundra, the variety of terrestrial ecosystems lying within tropical latitudes exceeds that of any other region on earth. Our knowledge of net primary productivity (NPP) rates in tropical ecosystems must be described as fragmentary. The relatively few available data pertain to a diverse assortment of samples subject to different levels of precipitation and disturbance.