CURSO DIÁRIO E SAZONAL DO POTENCIAL HÍDRICO FOLIAR DE MOGNO EM SISTEMAAGROFLORESTAL1

Este trabalho objetivou avaliar o curso diário e sazonal do potencial hídrico foliar de mogno (Swietenia macrophylla King) (Meliaceae) em sistema agroflorestal (SAF). O experimento foi realizado em árvores de S. macrophylla plantadas num sistema agroflorestal instalado no Campo Experimental da Embrapa Amazônia Ocidental, Manaus, AM. Avaliou-se o potencial hídrico foliar (Ψf) dos cursos diário e sazonal nos anos 2004 e 2005, por meio da utilização de bomba de pressão tipo Scholander. Os resultados indicaram que os valores do Ψf de S. macrophylla, de modo geral, foram superiores no início da manhã e no final da tarde, com redução acentuada ao meio-dia, e que, em relação à sazonalidade de precipitação, as menores taxas foram reportadas para a época menos chuvosa, variando de -26 bar em 2004 para -31bar em 2005. Verificou-se que o potencial hídrico de Swietenia macrophylla em sistema agroflorestal sofreu reduções significativas em razão dos baixos índices pluviométricos entre junho e outubro de 2005

Controls on methane emissions from <i>Alnus glutinosa</i> saplings

Recent studies have confirmed significant tree-mediated methane emissions in wetlands; however, conditions and processes controlling such emissions are unclear. Here we identify factors that control the emission of methane from Alnus glutinosa. Methane fluxes from the soil surface, tree stem surfaces, leaf surfaces and whole meso-cosms, pore water methane concentrations and physiological factors (assimilation rate, stomatal conductance and transpiration) were measured from 4-yr old A. glutinosa trees grown under two artificially controlled water-table positions. Up to 64% of methane emitted from the high water-table mesocosms was transported to the atmosphere through A. glutinosa. Stem emissions from 2 to 22 cm above the soil surface accounted for up to 42% of total tree-mediated methane emissions. Methane emissions were not detected from leaves and no relationship existed between leaf surface area and rates of tree-mediated methane emissions. Tree stem methane flux strength was controlled by the amount of methane dissolved in pore water and the density of stem lenticels. Our data show that stem surfaces dominate methane egress from A. glutinosa, suggesting that leaf area index is not a suitable approach for scaling tree-mediated methane emissions from all types of forested wetland

Ectomycorrhizal Colonization and Diversity in Relation to Tree Biomass and Nutrition in a Plantation of Transgenic Poplars with Modified Lignin Biosynthesis

Wood from biomass plantations with fast growing tree species such as poplars can be used as an alternative feedstock for production of biofuels. To facilitate utilization of lignocellulose for saccharification, transgenic poplars with modified or reduced lignin contents may be useful. However, the potential impact of poplars modified in the lignification pathway on ectomycorrhizal (EM) fungi, which play important roles for plant nutrition, is not known. The goal of this study was to investigate EM colonization and community composition in relation to biomass and nutrient status in wildtype (WT, Populus tremula6Populus alba) and transgenic poplar lines with suppressed activities of cinnamyl alcohol dehydrogenase, caffeate/ 5-hydroxyferulate O-methyltransferase, and cinnamoyl-CoA reductase in a biomass plantation. In different one-year-old poplar lines EM colonization varied from 58% to 86%, but the EM community composition of WT and transgenic poplars were indistinguishable. After two years, the colonization rate of all lines was increased to about 100%, but separation of EM communities between distinct transgenic poplar genotypes was observed. The differentiation of the EM assemblages was similar to that found between different genotypes of commercial clones of Populus6euramericana. The transgenic poplars exhibited significant growth and nutrient element differences in wood, with generally higher nutrient accumulation in stems of genotypes with lower than in those with higher biomass. A general linear mixed model simulated biomass of oneyear- old poplar stems with high accuracy (adjusted R2 = 97%) by two factors: EM colonization and inverse wood N concentration. These results imply a link between N allocation and EM colonization, which may be crucial for wood production in the establishment phase of poplar biomass plantations. Our data further support that multiple poplar genotypes regardless whether generated by transgenic approaches or conventional breeding increase the variation in EM community composition in biomass plantations.Open-Access-Publikationsfonds 2013peerReviewe