Forest clearing

Another model, first introduced by Moore, et al. (2i), was used to examine the role of terrestrial vegetation and the global carbon cycle, but did not include an ocean component. This model depended on estimates of carbon pool size and rates of CO2 uptake and release. This model has been used to project the effect of forest clearing and land-use change on the global carbon cycle (22, 23, 24). 

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). 

Similar results were reported in deforested Amazonian rainforests (66). Within three years following forest clearing and burning, nutrient concentrations of soil leachates had returned to levels typical of primary forests of the area. A combination of high rates of immobilization and storage by successional vegetation, coupled with a decline in easily decomposable substrates, was attributed to the reduction in leaching losses. 

Table 5. Inorganic N concentrations, mineralization and nitrification rates, and turnover rates ofNH% and NOJ in a chronosequence before and after forest clearing at Nova Vida, Brazil (after Neill et al., 1999).

Answer 18.7 The effect of forest clearing. What is the observation What is the conclusion in this case ... 

TNA forms colorless to white to yellowish crystals, which are highly resistant to shock, heat, friction, and percussion. It isa powerful explosive with high thermal stability, and is used in the manufacture of specialty explosives charges for fighting oil wells, forest clearing, line charges, and for missile warheads. Thecostof TNA production is rather high, so its use in explosives is limited. ... 

Ross, S. M. 1992. Soil and litter nutrient losses in forest clearings close to a forest-savanna boundary on Marac4 island, Roraima, Brazil. Pages 119-143. in P. A. Furley, J Proctor, and J. A. Ratter, editors. Nature and Dynamics of Forest-Savanna Boundaries. Chapman and Hall, London. 

Brown, S., and A. E. Lugo. 1990. "Effects of forest clearing and succession on the carbon and nitrogen content of soils in Puerto Rico and U.S. Virgin Islands." Plant and SoU 124 53-64. 

Neill, C., J. M. Melillo, P. A. Steudler, C. C. Cerri, J. F. L. de Moreaes, M. C. Piccolo, and M. Brito. 1997. "Soil carbon and nitrogen stocks following forest clearing for pasture in the southwestern Brazilian Amazon. Ecological Applications 7 1216-1225. 

Carvalho, Jr., JA., J. M. Santos, J. C. Santos, M. M. Leitao, and N. Higudii. 1995. A tropical rain forest clearing experiment by biomass burning in the Manaus region. Atmospheric Environment 29(17) 2301-2309. 

To assess the potential need for deep soil nutrients we first evaluate the loss of aboveground nutrients during forest clearing. If through various mechanisms (i.e. soil surface charge) the nutrients from the primary forest were retained on site, no new nutrients would be required to regenerate a secondary forest of equal stature. Or similarly, if losses were small, surface soil might contribute a sufficient quantity of nutrient such that deep... 

Fearnside, P. M., P. M. L. A. Graga, and F. J. A. Rodrigues, nd-b. Burning of Amazonian rainforests Burning efficiency and charcoal formation in forest cleared for cattle pasture near Manaus, Brazil (in preparation). 

Van der Weert R., The influence of mechanical forest clearing on soil conditions and resulting effects on root growth. Trop. Agri. (Trinidad) , 51, 325-331 (1974). 

Quantifying the sources and rates of input of base cation nutrients (calcium, magnesium, potassium, and sodium) to forest ecosystems is an important goal in forest biogeochemistry, particularly when seeking to understand the recovery from environmental disturbances such as acid rain and forest clear-cutting. The earliest study to use isotopes as an indicator of atmospheric inputs to soils was by Dymond et al. (1974), who used strontium isotope measurements of micas in Hawaiian soils to determine that a significant proportion of the potassium input to Hawaiian soils was from deposition of dust transported... 

Increased erosion due to forest clear-cutting and widespread cultivation has increased riverine suspended matter concentrations, and thus increased the riverine particulate-P flux. Dams, in contrast, decrease sediment loads in rivers and therefore diminish the phosphorus flux to the oceans. However, increased erosion below dams... 

These expressions are sufficient to calculate wind speeds over hills for different clearcut options over alternative slope triangular hills. Meroney, 1993 [418] presented figures based using the above relations for effects of various size forest clear-cuts on hill top flowfields. These measurements were subsequently compared with windtunnel measurements of wind fields over various two-dimensional hill shapes covered with model forest canopies simulated by different depths of plastic indoor-outdoor carpeting, Meroney, et al., 1993 [419],... 

A long-exposure photograph of the giant snake in the forest clearly defines... 

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