Access to water reserves in deep soil during drought periods determines whether ornot the tropical moist forests of Amazonia will be buffered from the deleterious effectsof water deficits. Changing climatic conditions are predicted to increase periods of droughtin Amazonian forests and may lead to increased tree mortality, changes in forestcomposition, or greater susceptibility to fire. A throughfall reduction experiment has beenestablished in the Tapajo ́s National Forest of east-central Amazonia (Brazil) to test thepotential effects of severe water stress during prolonged droughts. Using time domainreflectometry observations of water contents from this experiment, we have developed adynamic, one-dimensional, vertical flow model to enhance our understanding ofhydrologic processes within these tall-stature forests on well-drained, upland, deepOxisols and to simulate changes in the distribution of soil water. Simulations using960 days of data accurately captured mild soil water depletion near the surface afterthe first treatment year and decreasing soil moisture at depth during the second treatmentyear. The model is sensitive to the water retention and unsaturated flow equationparameters, specifically the van Genuchten parametersqs,qr, andn, but less sensitive toKsanda. The low root-mean-square error between observed and predicted volumetric soilwater content suggests that this vertical flow model captures the most importanthydrologic processes in the upper landscape position of this study site. The modelindicates that present rates of evapotranspiration within the exclusion plot have beensustained at the expense of soil water storage.
Caminhos para uma Agricultura Familiar sob Bases Ecológicas: Produzindo com Baixa Emissão de Carbono
Com o intuito de promover um diálogo qualificado sobre os caminhos da produção familiar rumo a uma produção de baixa emissão de carbono, o Instituto de Pesquisa Ambiental da Amazônia (IPAM), em parceria institucional com a Secretaria de Agricultura Familiar (SAF), o Núcleo de Estudos Agrários e Desenvolvimento Rural (NEAD), o Instituto Nacional de Colonização e Reforma Agrária (Incra - Ministério do Desenvolvimento Agrário), a Empresa Brasileira de Pesquisa Agropecuária (Embrapa) e o Ministério do Meio Ambiente (MMA), realizou um seminário, no dia 13 de junho de 2013, intitulado “Caminhos para uma Agricultura Familiar sob Bases Ecológicas: produzindo com Baixa Emissão de Carbono”. O livro traz os artigos escritos pelos especialistas que participaram do evento e foram elaborados com uma visão para a diversidade que permeia todos os biomas, divididos em eixos lógicos que procuraram responder aos desafios da agricultura familiar.