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Shade Trees (shade + tree)

Distribution by Scientific Domains

Life Sciences	63%
Earth and Environmental Science	27%

Selected Abstracts

Water use characteristics of cacao and Gliricidia trees in an agroforest in Central Sulawesi, Indonesia

ECOHYDROLOGY, Issue 4 2009
Michael Köhler
Abstract Water use characteristics of cacao (Theobroma cacao) and Gliricidia sepium shade trees were studied in an agroforest on Sulawesi, Indonesia. The objectives were: (1) to identify environmental and tree structural factors controlling water use, (2) to analyse the effect of shade tree cover on cacao water use and (3) to estimate stand level transpiration. Sap flux density was measured in up to 18 trees per species and described with a Jarvis-type model. Model parameters suggested a 49% higher maximum sap flux density in cacao than in Gliricidia and species differences in the response to vapour pressure deficit and radiation. Tree water use was positively related to tree diameter in both species, but this relationship tended to differ between species. In cacao trees maximal tree water use increased with decreasing canopy gap fraction above the trees (R2adj = 0·39, p = 0·04). This was paralleled by an increase of cacao stem diameter and leaf area with decreasing gap fraction. Maximum water use rate per unit crown area of cacao was 13% higher than that of Gliricidia. At the stand level the average transpiration rate was estimated at 1·5 mm day,1 per unit ground area, 70% of which was contributed to by cacao. We conclude that, in the given stand, species differed substantially in water use characteristics, while estimated stand transpiration is in line with findings from other studies for cacao stands. Shade trees may enhance stand transpiration through own water use and additionally by increasing water use rates of cacao trees. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Effects of Shade-Tree Species and Crop Structure on the Winter Arthropod and Bird Communities in a Jamaican Shade Coffee Plantation,

BIOTROPICA, Issue 1 2000
Matthew D. Johnson
ABSTRACT I examined the effects of two farm management variables, shade-tree species and crop structure, on the winter (dry season) arthropod and bird communities in a Jamaican shade coffee plantation. Birds and canopy arthropods were more abundant in areas of the plantation shaded by the tree Inga vera than by Pseudalbizia berteroana. The abundance of arthropods (potential pests) on the coffee crop, however, was unaffected by shade-tree species. Canopy arthropods, particularly psyllids (Homoptera), were especially abundant on Inga in late winter, when it was producing new leaves and nectar-rich flowers. Insectivorous and nectarivorous birds showed the strongest response to Inga; thus the concentration of birds in Inga may be a response to abundant food. Coffee-tree arthropod abundance was much lower than in the shade trees and was affected little by farm management variables, although arthropods tended to be more abundant in dense (unpruned) than open (recently pruned) areas of the plantation. Perhaps in response, leaf-gleaning insectivorous birds were more abundant in dense areas. These results underscore that although some shade coffee plantations may provide habitat for arthropod and bird communities, differences in farm management practices can significantly affect their abundances. Furthermore, this study provides evidence suggesting that bird communities in coffee respond to spatial variation in arthropod availability. I conclude that /. vera is a better shade tree than P. berteroana, but a choice in crop structures is less clear due to changing effects of prune management over time. [source]

Water use characteristics of cacao and Gliricidia trees in an agroforest in Central Sulawesi, Indonesia

Hydrological impacts of forest conversion to agriculture in a large river basin in northeast Thailand

HYDROLOGICAL PROCESSES, Issue 14 2001
J. Wilk
Abstract Small-scale experiments have demonstrated that forest clearance leads to an increase in water yield, but it is unclear if this result holds for larger river basins (>1000 km2). No widespread changes in rainfall totals and patterns were found in the 12 100 km2 Nam Pong catchment in northeast Thailand between 1957 and 1995, despite a reduction in the area classified as forest from 80% to 27% in the last three decades. Neither were any detectable changes found in any other water balance terms nor in the dynamics of the recession at the end of the rainy season. When a hydrological model calibrated against data from the period before the deforestation was applied for the last years of the study period (1987,1995), runoff generation was however underestimated by approximately 15%, indicating increased runoff generation after the deforestation. However, this was mainly due to the hydrological response during one single year in the first period, when the Q/P ratio was very low. When excluding this year, neither analysis based on the hydrological model could reveal any significant change of the water balance due to the deforestation. More detailed land-use analysis revealed that shade trees were left on agricultural plots as well as a number of abandoned areas where secondary growth can be expected, which is believed to account for the results. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Impact of shade on the spatial distribution of Sahlbergella singularis in traditional cocoa agroforests

AGRICULTURAL AND FOREST ENTOMOLOGY, Issue 1 2010
Régis Babin
1Shade management is commonly considered to be an effective pest management strategy for cocoa mirids, yet shade management recommendations are not based on extensive knowledge of the mirid ecology in traditional cocoa agroforests. 2The main objectives of the present study were an assessment of the impact of shade on the spatial distribution of mirid populations and thus the evaluation of shade management strategies. 3Mirid densities were measured and shade was characterized for three plots located in three different agroecological zones in the Centre region of Cameroon. Mirid densities generally followed a negative binomial law. Geostatistical procedures were used to characterize spatial distribution of mirid density. Light conditions were assessed using hemispherical photography. 4Populations of Sahlbergella singularis were highly aggregated in the plots. Semivariance analysis and kriging visualized the spatial dependence of mirid densities. Clearly distinguishable mirid pockets of 20,30 adjacent infested cocoa trees were identified in two of the three plots. 5The high diversity of shade tree species and the large variability in density and size of shade trees resulted in a considerable heterogeneity of plot light conditions. Percentage transmitted light varied in the range 9.4,80.1% in the most heterogeneous plot. 6For two of the three plots, mirid pockets were aggregated in those areas where light transmission was highest. In the third plot, relatively high mirid densities and the presence of an alternative host resulted in a more homogeneous distribution. The importance of these findings for improved mirid control is discussed. [source]

Fusarium oxysporum: exploring the molecular arsenal of a vascular wilt fungus

MOLECULAR PLANT PATHOLOGY, Issue 5 2003
Antonio Di Pietro
SUMMARY Taxonomy: Vascular wilt fungus; Ascomycete although sexual stage is yet to be found. The most closely related teleomorphic group, Gibberella, is classified within the Pyrenomycetes. Host range: Very broad at the species level. More than 120 different formae speciales have been identified based on specificity to host species belonging to a wide range of plant families. Disease symptoms: Initial symptoms of vascular wilt include vein clearing and leaf epinasty, followed by stunting, yellowing of the lower leafs, progressive wilting of leaves and stem, defoliation and finally death of the plant. In cross-sections of the stem, a brown ring is evident in the area of the vascular bundles. Some formae speciales are not primarily vascular pathogens but cause foot- and rootrot or bulbrot. Economic importance: Causes severe losses on most vegetables and flowers, several field crops such as cotton and tobacco, plantation crops such as banana, plantain, coffee and sugarcane, and a few shade trees. Control: Use of resistant varieties is the only practical measure for controlling the disease in the field. Under greenhouse conditions, soil sterilization can be performed. Alternative control methods with potential for the future include soil solarization and biological control with antagonistic bacteria or fungi. Useful websites: http://www.fgsc.net/fus.htm, http://www-genome.wi.mit.edu/annotation/fungi/fusarium/, http://www.cbs.knaw.nl/fusarium/database.html [source]

The conservation value for birds of cacao plantations with diverse planted shade in Tabasco, Mexico

ANIMAL CONSERVATION, Issue 2 2000
Russell Greenberg
We surveyed birds in cacao (Theobroma cacao) plantations in the state of Tabasco, Mexico. The shade canopy was planted by farmers and consisted of approximately 60 species of trees with no single dominant species. Canopy height averaged 15 m and the structure was multi-storied. We conducted 220 ten minute, 25 m radius point counts for birds and detected 1550 individuals from 81 species. The average number of birds/point and the expected diversity in a fixed number of individuals within the cacao surveyed were well within the range of other lowland habitats, including agricultural sites, that we have surveyed previously in neighbouring Chiapas. In the Tabascan cacao, the migrant group was composed, in part, of forest species, and dimorphic species were represented primarily by males, which in other areas are known to dominate forest or forest-like habitats. In contrast to the composition of migrant species, we found few resident forest specialists in Tabascan cacao. Instead, the tropical resident group was composed of large-bodied generalist species that use small patches of trees in open habitats. These results (moderate diversity, low numbers of forest specialists) differ from the few studies completed in ,rustic' cacao systems located near large tracts of forest. The planted shade cacao agroecosystem , at least in the absence of nearby forest , may have a limited value for conserving lost tropical forest bird diversity, but it provides habitat for woodland-associated migratory species. Our results also indicate that the planted shade cacao plantations supported few small omnivorous or frugivorous species, probably because cacao itself, as well as the dominant shade trees, produce primarily mammal or wind dispersed fruit and seeds. [source]

Twig-Nesting Ants: The Hidden Predators of the Coffee Berry Borer in Chiapas, Mexico

BIOTROPICA, Issue 3 2010
Ashley Larsen
ABSTRACT Coffee is a globally important crop that is subject to numerous pest problems, many of which are partially controlled by predatory ants. Yet several studies have proposed that these ecosystem services may be reduced where agricultural systems are more intensively managed. Here we investigate the predatory ability of twig-nesting ants on the main pest of coffee, the coffee berry borer (Hypothenemus hampei) under different management systems in southwest Chiapas, Mexico. We conducted both laboratory and field experiments to examine which twig-nesting ant species, if any, can prey on free-living borers or can remove borers embedded in coffee fruits and whether the effects of the twig-nesting ant community differ with habitat type. Results indicate that several species of twig-nesting ants are effective predators of both free-living borers and those embedded in coffee fruits. In the lab, Pseudomyrmex ejectus, Pseudomyrmex simplex, and Pseudomyrmex PSW-53 effectively removed free-living and embedded borers. In the field, abundance, but not diversity, of twig-nesting ant colonies was influenced by shade management techniques, with the highest colony abundance present in the sites where shade trees were recently pruned. However, borer removal rates in the field were significant only in the shadiest site, but not in more intensively managed sites. This study provides evidence that twig-nesting ants can act as predators of the coffee berry borer and that the presence of twig-nesting ants may not be strongly linked to shade management intensity, as has been suggested for other arthropod predators of the borer. Abstract in Spanish is available at http://www.blackwell-synergy.com/loi/btp [source]

Conservation of Vascular Epiphyte Diversity in Shade Cacao Plantations in the Chocó Region of Ecuador

BIOTROPICA, Issue 4 2009
Xavier Haro-Carrión
ABSTRACT To assess the contributions of rustic shade cacao plantations to vascular epiphyte conservation, we compared epiphyte species richness, abundance, composition, and vertical distributions on shade trees and in the understories of six plantations and adjacent natural forests. On three phorophytes and three 10 × 10 m understory plots in each of the agroforestry plantations and natural forests, 54 and 77 species were observed, respectively. Individual-based rarefaction curves revealed that epiphyte species richness was significantly higher on forest phorophytes than on cacao farm shade trees; detailed analyses showed that the differences were confined to the inner and outer crown zones of the phorophytes. No differences in epiphyte species richness were found in understories. Araceae, Piperaceae, and Pteridophyta were less species-rich in plantations than in forests, while there were no differences in Orchidaceae and Bromeliaceae. Regression analysis revealed that epiphyte species richness on trunks varied with canopy cover, while abundance was more closely related to soil pH, canopy cover, and phorophyte height. For crown epiphytes, phorophyte diameter at breast height (dbh) explained much of the variation in species richness and abundance. There were also pronounced downward shifts in the vertical distributions of epiphyte species in agroforests relative to natural forests. The results confirm that epiphyte diversity, composition, and vertical distributions are useful indicators of human disturbance and showed that while the studied plantations serve to preserve portions of epiphyte diversity in the landscape, their presence does not fully compensate for the loss of forests. [source]