Forests tropical

Human activity, particularly in the developing world, continues to make it more difficult to sustain the world s biomass growth areas. It has been estimated that tropical forests are disappearing at a rate of tens of thousands of hm per year. Satellite imaging and field surveys show that Brazil alone has a deforestation rate of approximately 8 x 10 hm /yr (5). At a mean net carbon yield for tropical rain forests of 9.90 t/hm yr (4) (4.42 short ton /acreyr), this rate of deforestation corresponds to a loss of 79.2 x 10 t/yr of net biomass carbon productivity. 

West Indies tropical forest, mixed ages 59.0 212 1.55... 

Freshwater with less than 500 ppm (or 0.05%) dissolved soHds is generally considered to be potable. Rain is the source of freshwater, and its precipitation of >1.3 x 10 m /d over the earth s surface averages about 1.05 m (depth) per year. Extremes range from almost 2ero ia North Chile s desert borderiag the Pacific Coast to > 25.4 m ia some tropical forests and on some high slopes where the high, cold mountains condense floods from the clouds. 

Land use changes in the tropics have resulted in a landscape characterized as a mosaic of logged forests, cleared fields, and successional forests. This results in the transformation from extremely fire resistant rainforest ecosystems to anthropogenic landscapes in which fire is a common event (16, 17), Fires occur in disturbed tropical forests because deforestation has a dramatic effect on microclimate. Deforestation results in lower relative humidities, increased wind speeds, and increased air temperatures. In addition, deforestation results in increased quantities of biomass that are susceptible to fire. This biomass may be in the form of forest slash, leaf litter, grasses, lianas or herbaceous species (16, 18). 

Negligible quantities of wood may be removed when tropical forests are cut for shifting cultivation or pasture conversion. In contrast to the temperate coniferous forests of the Northwest USA, only small quantities of wood are usually exported as a result of timber operations in tropical evergreen forests. In... 

The burning of slash following deforestation, whether intentional or unintentional, results in far greater direct and indirect losses of nutrients than deforestation alone. This is particularly true in many tropical forests where only a small fraction (if any) of the aboveground biomass is removed prior to burning. Carbon losses from slash fires in the tropical dry forest were 4-5 fold greater than C losses from wood export (Table IV) (55). Slash fires in tropical dry forests resulted in N losses of 428-500 kg ha whereas fuel wood export of the relatively N-poor coarse woody debris amounted to approximately 41 kg N ha" Losses of P increase with increasing fire severity. P losses of 10-77 kg ha" as a result of severe fires is not uncommon (Table TV) (53, 58, 60). 

Tropical forests and savannas are the primary source of C emissions that originate from biomass burning (73, 75). However, temperate forests are also sources of atmospheric carbon. Harmon et al. (77) reported that conversion of primary temperate forests to younger, second-growth forests lead to increases in atmospheric CO2 levels, due to losses in long-term carbon storage within these forests. They ascertained that timber exploitation of 5 million hectares of primaiy forests in the Pacific Northwest of North America during the past century has resulted in the addition of 1,500 Tg of C to the atmosphere. 

Earthquake-caused landslides A major disturbance to tropical forests. Science 205, 997-999. 

Simon, A., Larsen, M. C., and Hupp, C. R. (1990). The role of soil processes in determining mechanisms of slope failure and hillslope development in a humid-tropical forest, eastern Puerto Rico. Geomorphology 3, 263-286. 

Another family of feedbacks involving biota arise via the process of evapotranspiration in which the rate of water vapor is transferred from the land surface to the atmosphere is mediated by plants. Several consequences have been proposed that include influences of biota on the greenhouse effect of water vapor as well as relative humidity and clouds. Lovelock (1988) suggested that tropical forests might be kept cool by increasing cloud cover in response to higher relative humidity released through enhanced evapotranspiration (via the clouds influences on albedo). Yet another connection arises because tree-covered land has different turbulence properties above it than bare soil, which also influences the cloud cover above. 

Wet weight was recorded on site for LUV, HUV, and LI fractions. Dry weight was determined in the lab (registered after drying in an oven at 80°C until constant weight). The equation introduced by Cairns and coworkers [31], for tropical forest and lower latitudes than 25°, was used. The AGB fraction, also called as "biomass density" when expressed as tons of oven-dried... 

Brown S. Estimating biomass and biomass change of tropical forests. FAO Montes, 1997.134 pp. 1-55. 

Chave J, Andalo C, Brown S, Cairns M, Chambers J, Eamus D et al. Tree allometry and improved estimation of carbon stocks and balance in tropical forests. Oecologia, 2005.145 pp. 87-89. 

Brown S, Gillespie A, Lugo A. Biomass estimation methods for tropical forests with applications to forest inventory data. Forest Science, 1989. 35(4) pp. 381-902. 

Values of a soil fertility index (SFI, Moran et al. 2000) or a soil evaluation factor (SEF, Lu et al. 2002) were calculated to quantify the intensity of the land degradation. SFI showed the applicability to measuring soil quality and to predicting succession rate of secondaiy tropical forest (Moran et al. 2000). The following equation was used to calculate SFI values (Lu et al. 2002). 

Savanna, Tropical Forest Fivi-Plinticic Ferrasols, Fuvisols, Vertisols, Subtropical Rendzinas, Ferralitic Cambisols, Nitosols, Ferralitic Arenosols, Subtropical South Asian 0.3 1.00 0.3... 

The Seasonal Tropical Forest and Woody Savanna ecosystems are common in tropical regions with a short dry period. The characteristic features of soils from these ecosystems are the neutral reaction of soil solution and periodic leaching during wet season. The herbaceous species favor the formation of both sward and humus horizons. 

For instance, clearing tropical forests in the Amazon basin for pasture alters rates of soil nitrogen cycling (Table 5). 

The pattern of NH4+ and N03 concentrations, and net mineralization and net nitrification rates in soils before and after clearing and burning tropical forest indicate ... 

Vitousek, P. M., Sanford, R. L. (1986). Nutrient cycling in moist tropical forest. Annual Review... 

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