This research utilized tower-based eddy covariance to quantify the trends in net ecosystem mass (CO 2 and H 2 O vapor) and energy exchange of important land-cover types of NW Mato Grosso during the March-December 2002 seasonal transition. Measurements were made in a mature transitional (ecotonal) tropical forest near Sinop, Mato Grosso, and a cattle pasture near Cotriguaçú , Mato Grosso, located 500 km WNW of Sinop. Pasture net ecosystem CO 2 exchange (NEE) was considerably more variable than the forest NEE over the seasonal transition, and the pasture had significantly higher rates of maximum gross primary production in every season except the dry-wet season transition (September-October). The pasture also had significantly higher rates of whole-ecosystem dark respiration than the forest during the wetter times of the year. Average ( AE 95% CI) rates of total daily NEE during the March-December 2002 measurement period were 26 AE 15 mmol m À2 day À1 for the forest (positive values indicate net CO 2 loss by the ecosystem) and À38 AE 26 mmol m À2 day À1 for the pasture. While both ecosystems partitioned more net radiation (R n ) into latent heat flux (L e ), the forest had significantly higher rates of L e and lower rates of sensible heat flux (H) than the pasture; a trend that became more extreme during the onset of the dry season. Large differences in pasture and forest mass and energy exchange occurred even though seasonal variations in micrometeorology (air temperature, humidity, and radiation) were relatively similar for both ecosystems. While the short measurement period and lack of spatial replication limit the ability to generalize these results to pasture and forest regions of the Amazon Basin, these results suggest important differences in the magnitude and seasonal variation of NEE and energy partitioning for pasture and transitional tropical forest.
The photosynthetic light response of Amazonian semi-deciduous forest trees of the rain forest–savanna transition near Sinop Mato Grosso, Brazil was measured between July 2000 and September 2003 to test the hypothesis that the photosynthetic capacity of trees acclimated to different growth light environments will decline during the dry season. Maximum photosynthesis (Amax) and stomatal conductance (gmax) were significantly higher during the wet season; however, the physiological response to drought was not a clear function of growth light environment. For some species, such as Psychotria sp. growing in the mid-canopy, internal leaf CO2 concentration (Ci) was >30% lower during the dry season suggesting that declines in Amax were caused in part by stomatal limitations to CO2 diffusion. For other species, such as Brosimum lactescens growing at the top of the canopy, Tovomita schomburgkii growing in the mid-canopy, and Dinizia excelsa growing in the understorey, dry season Ci declined by <20% suggesting that factors independent of CO2 diffusion were more important in limiting Amax. Dry-season declines in gmax appeared to be important for maintaining a more consistent leaf water potential for some species (T. schomburgkii and D. excelsa) but not others (Psychotria sp.). These results indicate that while seasonal drought exerts an important limitation on the physiological capacity of semi-deciduous Amazonian forest trees, the mechanism of this limitation may differ between species.
Efeito temporal da cultura da soja nos atributos físico-químicos do solo no Estado do Mato Grosso Eduardo Jacusiel MirandaDissertação apresentada para obtenção do título de Mestre em Ecologia Aplicada Piracicaba 2007Eduardo Jacusiel Miranda Engenheiro Agrônomo Efeito temporal da cultura da soja nos atributos físico-químicos do solo no Estado do Mato GrossoOrientador: Prof. Dr. PLÍNIO BARBOSA DE CAMARGO Dissertação apresentada para obtenção do título de Mestre em Ecologia Aplicada Piracicaba 2007 Dados Internacionais de Catalogação na Publicação (CIP) DIVISÃO DE BIBLIOTECA E DOCUMENTAÇÃO -ESALQ/USP Miranda, Eduardo JacusielEfeito temporal da cultura da soja nos atributos físico-quimicos do solo no Estado do Mato Grosso / Eduardo Jacusiel Miranda. --Piracicaba, 2007. 86 Aos grandes parceiros, Netão, CV, Vadico e outros irmãos da rocha, fiéis companheiros que guardam a sua vida por um fio de 10,2 mm de espessura.As "Tias" do Rucas, sempre bem humoradas e prontas para alegrar o almoço com um sorriso verdadeiro.Aos antigos colegas e amigos da UFMT que cultivam o espírito infantil e "open up" da descoberta! E a todos aqueles que eu esqueci de mencionar, mas que com toda a certeza foram indispensáveis para que este momento chega-se, fica aqui o meu Muito Grande Obrigado.À Maria "Caçadora" companheira, amiga e amada perola (bem branquinha) aqui encontrada, palavras adequadas me faltam, mas por sorte, são completamente desnecessárias! Grande Abraço, Bons Ventos e obrigado por TudO Eduardo 6 Stages As every flower fades and as all youth Departs, so life at every stage, So every virtue, so our grasp of truth, Blooms in its day and may not last forever. Since life may summon us at every age Be ready, heart, for parting, new endeavor, Be ready bravely and without remorse To find new light that old ties cannot give. In all beginnings dwells a magic force For guarding us and helping us to live.Serenely let us move to distant places And let no sentiments of home detain us. The Cosmic Spirit seeks not to restrain us But lifts us stage by stage to wider spaces. If we accept a home of our own making, Familiar habit makes for indolence. We must prepare for parting and leave-taking Or else remain the slaves of permanence... Even the hour of our death may send Us speeding on to fresh and newer spaces, And life may summon us to newer races. So be it, heart: bid farewell without end. RESUMO Efeito temporal da cultura da soja nos atributos físico-químicos do solo no Estado do Mato GrossoA humanidade como conhecemos hoje é totalmente dependente da agricultura de grande escala. Estamos chegando próximo ao esgotamento de novas áreas para ampliação ou substituição de áreas agrícolas. Isso torna premente uma avaliação da sustentabilidade dos agroecossistemas a fim de averiguar se eles estão aptos a continuar sua função de prover alimentos a uma população crescente. Este trabalho tem como foco os aspectos físicos e químicos do solo com visão restrita aos processos internos do sistema produtivo, sem uma avaliação da sustentabilidade de tod...
The net effect of agriculture on soil carbon is not yet fully understood. While a number of studies on shallow profiles have been published, evidence suggests that carbon stock changes occur in deeper layers. In this study we analyzed the effect of agriculture in the Cerrado soil C looking at changes in seven different profile depths from 0 to 100 cm in a commercial grain farm. We also used isotopic techniques to distinguish between the original Cerrado C 3 carbon and the C 4 carbon derived from the grasses used in agriculture. At 0-5 cm depth C stocks significantly decreased with cultivation time. The C stock did not change significantly when it was calculated using the 0-10, 0-20, 0-30, 0-50 or 0-75 cm profile (p > 0·05) but increased with cultivation time when the profile considered was 0-100 cm (p < 0·05). A two-source isotope model revealed that there was a significant increase in carbon derived from C 4 grasses for all depths with cultivation time. Annual carbon sequestration rates for the upper 100 cm of soil were 1·1 Mg C ha À1 year À1 for total carbon and 0·8 Mg C 4 C ha À1 year À1 for C 4 carbon. The oldest area, with 23 years of cultivation, had a soil C stock increase compared to the native Cerrado soil of 17·6%. These findings suggest that commercial grain farms practices may increase soil C stock compared to native Cerrado soil, if a more complete soil profile down to 100 cm is used to assess C stocks.
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