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TREE SPECIES FOR BIODIVERSITY CONSERVATION IN URBAN ZONES
Abstract
En México se registra alrededor del 10% de la diversidad biológica del mundo. Sin embargo, esta riqueza se ha reducido y deteriorado por el incremento de la población y actividades humanas, provocando un cambio de uso de la tierra; a través de la ocupación de hábitats naturales para el desarrollo de viviendas, industria, labores agrícolas y pecuarias de alto impacto. No obstante, una alternativa de conservación es el establecimiento de diversas especies a través de plantaciones en ambientes urbanos, que a su vez mejoren el clima local y produzcan bienestar social. El objetivo de este trabajo fue caracterizar especies arbóreas que actualmente son o no usadas en diferentes zonas de la Ciudad de México para conservar e incrementar áreas verdes, y mantener la biodiversidad en zonas urbanas. La determinación está basada en tres aspectos: (i) características biológicas de las especies, (ii) sitio de plantación de las especies y asociación con otras, y (iii) características y mantenimiento de la plantación. Se determinaron mediante una revisión bibliográfica los atributos de 39 especies potenciales para mantener la biodiversidad y mitigar impactos negativos de las zonas urbanas. Se sugiere ubicar las especies en sitios correctos con base en los aspectos reportados para favorecer el éxito de establecimiento. ABSTRACT Mexico has around 10% of the world biodiversity. However, this richness has been reduced and affected by population growth and human activities, generating land use change through the occupation of natural habitat for the establishment of houses, factories, and high-impact agricultural and livestock activities. Nevertheless, a conservation alternative is the establishment of diverse species in urban plantations, which improve local weather and promote social welfare. The aim of this work was to characterize tree species currently used or not used in different zones
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La Ciudad de México ha sufrido un deterioro ambiental debido al crecimiento desmedido de su población humana, por lo que es necesario mejorar sus áreas verdes e incrementar los servicios ambientales y la calidad de vida de sus pobladores. El Bosque de Chapultepec destaca por ser la de mayor extensión (686 ha), además de su relevancia histórica, cultural y recreativa. La 2a Sección ha sufrido una reducción de su dosel debido, principalmente, a la declinación del eucalipto, una de las especies de mayor frecuencia; sin embargo, con el fin de contar con nuevas opciones para su reforestación, se evaluó la respuesta de seis especies arbóreas nativas de México, mediante un ensayo con un diseño de tres bloques al azar con nueve plantas por especie en cada parcela, en las que se determinó su supervivencia, altura y diámetro basal cada tres meses durante un año. Hubo diferencias entre los porcentajes de supervivencia (100 – 77.78 %), aunque no estadísticamente significativos; sin embargo, en las tasas de crecimiento en diámetro y altura se presentaron diferencias, pues los valores más grandes se registraron en Thevethia thevetioides, Heliocarpus reticulatus, y Pinus greggii var. australis. Todas las especies, con excepción de Pinus cembroides, mostraron una buena respuesta a las condiciones ambientales de la 2a sección, por lo que pueden ser una buena alternativa para reforestar las áreas verdes de la Ciudad de México que reúnan condiciones ecológicas similares.
As urban areas expand, understanding how ecological processes function in cities has become increasingly important for conserving biodiversity. Urban green spaces are critical habitats to support biodiversity, but we still have a limited understanding of their ecology and how they function to conserve biodiversity at local and landscape scales across multiple taxa. Given this limited view, we discuss five key questions that need to be addressed to advance the ecology of urban green spaces for biodiversity conservation and restoration. Specifically, we discuss the need for research to understand how green space size, connectedness, and type influence the community, population, and life-history dynamics of multiple taxa in cities. A research framework based in landscape and metapopulation ecology will allow for a greater understanding of the ecological function of green spaces and thus allow for planning and management of green spaces to conserve biodiversity and aid in restoration activities.
The purpose of this paper is to underline the role of some wooden species in different units of green areas in Iasi municipality in improving the quality of the environment. By regular visits in the field, we have identified the wooden species frequent in different areas; based on the bibliography in the field, we underlined the ecological characteristics, the resistance to unfavourable climate factors, and the role of these species in improving the quality of the environment. Most species taken into account are resistant to extremely cold weather and to drought; are considered resistant (
The urban heat island (UHI) is mainly a nocturnal phenomenon but it also appears during the day in Mexico City. This UHI may affect the human thermal comfort which can influence human productivity and morbidity in the spring/summer period. A simple phenomenological model based on the energy balance was developed to generate theoretical support of the UHI mitigation in Mexico City focused on the latent heat flux change by increasing tree coverage to reduce sensible heat flux and air temperature. Half hourly data of the urban energy balance components were generated in a typical residential/commercial neighborhood of Mexico City, and then parameterized using easily measured variables (air temperature, humidity, pressure, visibility). Canopy conductance was estimated every hour in four tree species and transpiration was estimated using sap flow technique and parameterized by the envelope function method. Averaged values of net radiation, energy storage, sensible and latent heat flux were around 449, 224, 153 and 72 W m-2, respectively. Daily tree transpiration ranged 3.64─4.35 Ld-1. To reduce air temperature by 1 °C in the studied area, 63 large Eucaliptus camaldulensis would be required per hectare, whereas to reduce the air temperature by 2 °C only 24 large Liquidambar styraciflua trees would be required. This study suggests increasing tree canopy cover in the city cannot mitigate UHI adequately, but requires choosing the most appropriate tree species to solve this problem. Also it is imperative to include these types of studies in the tree selection and urban development planning to adequately mitigate UHI.
The 3-year Chicago Urban Forest Climate Project examined how trees affect these components of the regional urban ecosystem. The region`s tree cover has increased from a presettlement level of about 13 percent to nearly 20 percent today. There are an estimated 50.8 million trees in the region; 66 percent in good or excellent condition. The trees tend to be small; 77 percent less than 15 cm d.b.h. Street trees are only 10 percent of the city`s trees, but 24 percent of leaf surface area because they are typically larger than off-street trees. During 1991, the region`s trees removed an estimated 6,145 tons of air pollutants, providing air cleansing worth $9.2 million. Each year they sequester an estimated 315,800 metric tons of carbon and provide residential heating and cooling energy savings that, in turn, reduce carbon emissions from power plants by 12,600 tons annually. Increasing tree cover 10 percent or planting about three trees per building lot is estimated to save annual heating and cooling costs by $50 to $90 per dwelling unit once the trees mature. The net present value of services trees provide is estimated as $38 million, or $402 per planted tree. The present value of long-term benefits are more than twice the present value of costs.
Urban and suburban parks can play an important role in the conservation of biodiversity, especially in a strongly urbanised region like Flanders (Belgium). A previously developed method for monitoring biodiversity was applied to 15 parks in Flanders. This method took both habitat and species diversity into account and resulted in 13 biodiversity indicators. The results show that urban and suburban parks can have a high species richness, especially if they consist of different more or less semi-natural habitats. The relationships between the biodiversity indicators and the ecological factors affecting the biodiversity were examined using multivariate analyses and correlation techniques. Park area was the main factor explaining the variation in biodiversity indicators, so larger parks could contribute more to the conservation of biodiversity than small ones. A biodiversity score based on habitat diversity and species richness was proposed to summarise and evaluate the biodiversity. This score is not correlated with the park area and is therefore considered as a reliable indicator for comparing biodiversity in parks of different area.
Spatial climate models were developed for México and its periphery (southern USA, Cuba, Belize and Guatemala) for monthly
normals (1961–1990) of average, maximum and minimum temperature and precipitation using thin plate smoothing splines of ANUSPLIN
software on ca. 3,800 observations. The fit of the model was generally good: the signal was considerably less than one-half
of the number of observations, and reasonable standard errors for the surfaces would be less than 1°C for temperature and
10–15% for precipitation. Monthly normals were updated for three time periods according to three General Circulation Models
and three emission scenarios. On average, mean annual temperature would increase 1.5°C by year 2030, 2.3°C by year 2060 and
3.7°C by year 2090; annual precipitation would decrease −6.7% by year 2030, −9.0% by year 2060 and −18.2% by year 2090. By
converting monthly means into a series of variables relevant to biology (e. g., degree-days > 5°C, aridity index), the models
are directly suited for inferring plant–climate relationships and, therefore, in assessing impact of and developing programs
for accommodating global warming. Programs are outlined for (a) assisting migration of four commercially important species
of pine distributed in altitudinal sequence in Michoacán State (b) developing conservation programs in the floristically diverse
Tehuacán Valley, and (c) perpetuating Pinus chiapensis, a threatened endemic. Climate surfaces, point or gridded climatic estimates and maps are available at http://forest.moscowfsl.wsu.edu/climate/.
The aim of this study is to know the effect of urbanization and human activities on the ant species richness in the city of Coatepec, Veracruz, Mexico. On the base of 100 random sample points, we conducted a study on five different habitats: urban streets, coffee plantations, suggar cane plantations, secondary roads, and suburban vacant lots. We registered a total of 40 ant species. The richest habitats in species were suburban vacant lots with an average of 9.5 species. In contrast, urban streets registered only an average of 4.8 species. The number of introduced species was 14 (35%) and the remaining 26 species (65%) were native of Mexico. Regarding their foraging behavior, we registered five different guilds: omnivorous species (14 species), carnivorous species (10 species), insect and honeydew feeders (10 species), fungus growing ants (3 species) and granivorous species (3 species). According to a linear regression between the species richness and the area covered by cement, we found a negative correlation (r=-0.47 p < 0.05). This means that species richness diminishes with the increasing of urbanization. The result of the analysis of numerical classification shows the formation of two large clusters. One related with typical urban environment, and the other associated with a more natural environment located in the suburbs like the coffee plantations. In general, the influence of urbanization and human activity has a negative effect on the ant species richness.
Efforts at mitigating global biodiversity loss have often focused on preserving large, intact natural habitats. However, preserving biodiversity should also be an important goal in the urban environment, especially in highly urbanized areas where little natural habitat remains. Increasingly, research at the city/county scale as well as at the landscape scale reveals that urban areas can contain relatively high levels of biodiversity. Important percentages of species found in the surrounding natural habitat, including endangered species, have been found in the urban forest.This contribution concisely highlights some examples of urban biodiversity research from various areas of the world. Key issues involved in understanding the patterns and processes that affect urban biodiversity, such as the urban–rural gradient and biotic homogenization, are addressed. The potential for urban areas to harbor considerable amounts of biodiversity needs to be recognized by city planners and urban foresters so that management practices that preserve and promote that diversity can be pursued. Management options should focus on increasing biodiversity in all aspects of the urban forest, from street trees to urban parks and woodlots.