O Pará no século XXI: oportunidades para o desenvolvimento sustentável / The State of Pará in twenty-first century: opportunities to sustainable development

Aborda questões críticas e emergentes sobre o uso da terra no Pará. Avalia a capacidade das instituições regionais em identificar e tratar essas questões. Analisa sete das principais formas de uso dos recursos naturais. Identifica necessidades que devem ser abordadas para apoiar cada uma dessas formas. Identifica áreas prioritárias para o trabalho futuro das instituições regionais do Pará. Analisa vinte e três instituições regionais, incluindo órgãos públicos e ONGs. Verifica que muitas das agências governamentais sofrem de falta de clareza em sua missão e de formas não-participativas de administração. Em contrapartida, muitas ONGs possuem uma missão bem definida e uma equipe profundamente motivada, porém atuam dentro de uma escala extremamente limitada. Explora as formas pelas quais as agências governamentais podem se tornar muito mais eficientes na definição e realização de suas missões e diminuir o impacto trágico do desmatamento na Amazônia Oriental.

Land-use in Amazonia and the cerrado of Brazil

The total area and annual rate of native vegetation clearing is greatest in the Cerrado region followed by the Brazilian states of Par , Mato Grosso, Maranhao and Rond"nia. Amazonian forest clearing proceeds most quickly where abundant natural resources (wood or land) are accessible by roads and close to markets. These regions are concentrated along the eastern and southern flanks of Amazonia, particularly in eastern Par , Cuiab and Rond"nia. There are still large discrepancies in estimates of annual deforestation; Landsat (Thematic Mapper-based) mapping of deforestation in the closed-canopy forests of Amazonia has not include non-Brazilian countries and is incomplete for the cerrado biome. Amazonian deforestation was last mapped in 1994. Current estimates of Amazonian forest clearing do not include most of the forests that are effected by logging each year, which is an area (about 7,000 Km2yr-1) more than half the size of the area of annual deforestation. Logging changes forest structure and increases forest flammability. The intensity of logging ranges from 1- to 100-species harvest, and averages 20 m3 of wood harvested per hectare. Logging may increase dramatically in the coming years. Fire affects large, but difficult to measure, areas of pastureland, logged forests, secondary forests and primary forests. Forest ground fires are particularly difficult to map from satellite data. Fire is more frequent where forest clearing is taking place, and where seasonal drough is most severe. The destiny of Amazonian forest land cleared for crops and cattle pasture is complex, and highly variable regionally. Areal estimates are needed for managed pasture, degraded pasture, cropland and secondary forests, for these ecosystems are functionally distinct. Most forest clearing is for pasture establishment, followed by shifting cultivation. Cattle pasture is the logical land-use for both small-scale and large-scale rural Amazonians because cattle are easily sold or traded, and they maintain their value during inflation. Cattle pastures help secure land claims and increase land value. In the Cerrado, there has been a shift from extesive cattle grazing of natural savannas to pastures planted with African forage grasses; mechanized soy bean production is the second most extensive land-use. Pastures are the most important land-cover for the LBA (Large-Scale Biosphere-Atmosphere experiment in Amazonia) science campaign. Brazilian Amazonia experiences reduced rainfall...

Transpiration rates for several woody successional species and for a pasture in the upper Amazon basin in Venezuela

Evapotranspiration rates for a eight month old tropical pasture were estimated using the Penman-Monteith equation. Transpiration rates for several woody secondary successional species and stump sprous in the pasture and conucos (farm sites) were measured using the tritiated water technique.The stuty area was located near the village of San Carlos de Rio Negro (1° 56' N, 67° 03' W) in southern Venezuela, near the confluence of the Casiquiare and the Rio Guania wich forms the Rio Negro. The terrain was gently rolling with the areas between the small ridges supporting Amazon caatina forests on spodosols, and higher never flooded areas (tierra firma) supporting a mixed species forest.Results indicated that for a one month period, ET loss (0.46 cm/day) from the pasture, including soil and root mat evaporation, was about 0.43 cm/day less than estimated from the adjacent undisturbed forest (0.89 cm/day). Pan A evaporation for the same time period was 0.64 cm/day. Transpiration rates for seed established species were significantly less (0.38 cm/day) than for stump sprouts (1.09 cm/day) of the primary forest in the pasture.

As taxas de evapotranspiração de uma pastagem de oito meses foram estimadas usando a equação Penman-Monteith. As taxas de transpiração de várias espécies lenhosas sucessionais e rebrotos na pastagem e canucos (fazendas) foram medidas com o uso de água radiada com tritio. O local de estudo estava localizado perto do vilarejo de São Casrlos do Rio Negro (1° 56' N, 67° 03' W) na parte sul da Venezuela, próximo a confluência do Casiquiare e Rio Gania, que formam o Rio Negro. O terreno era levemente ondulado com as áreas entre os pequenos cumes que sustentam uma mata de espécies mistas. Os resultados mostraram que durante o período de um mês, a perda de ET (0.46 cm/dia) da pastagem, incluindo a evaporação do solo e da camada das raízes, foi de cerca de 0.43 cm/dia menos que a estimada para a mata adjacente não-perturbada (0.89 cm/dia). A evaporação Pan A para o mesmo período foi de 0.64 cm/dia. As taxas de transpiração para as espécies estabelecidas através de sementes foram significativamente menores (0.38 cm/dia) do que para os rebrotos (1.09 cm/dia) das espécies da mata primária na pastagem.