International audienceThe seasonal climate drivers of the carbon cycle in tropical forests remain poorly known, although these forests account for more carbon assimilation and storage than any other terrestrial ecosystem. Based on a unique combination of seasonal pan-tropical data sets from 89 experimental sites (68 include aboveground wood productivity measurements and 35 litter productivity measurements), their associated canopy photosynthetic capacity (enhanced vegetation index, EVI) and climate, we ask how carbon assimilation and aboveground allocation are related to climate seasonality in tropical forests and how they interact in the seasonal carbon cycle. We found that canopy photosynthetic capacity seasonality responds positively to precipitation when rainfall is < 2000 mm yr(-1) (water-limited forests) and to radiation otherwise (light-limited forests). On the other hand, independent of climate limitations, wood productivity and litterfall are driven by seasonal variation in precipitation and evapotranspiration, respectively. Consequently, light-limited forests present an asynchronism between canopy photosynthetic capacity and wood productivity. First-order control by precipitation likely indicates a decrease in tropical forest productivity in a drier climate in water-limited forest, and in current light-limited forest with future rainfall < 2000 mm yr(-1)

O objetivo deste trabalho foi estimar o tamanho ótimo de parcelas experimentais de Eucalyptus saligna Smith, aos 15 meses de idade e aos 5 anos e meio de idade. Os experimentos foram instalados no Horto Florestal Barba Negra em área de produqdo da empresa Riocell S/A, localizada no município de Barra do Ribeiro - RS. O método utilizado para determinação do tamanho ótimo de parcelas foi o de Pimentel Gomes - ESALQ/USP. Os resultados demonstram que o tamanho ótimo de parcelas para plantas com 5 anos e meio de idade é de 9 a 25 plantas úteis medidas, e para o experimento com 15 rneses de idade a parcela ideal é de 4 plantas.

RESUMOEste trabalho foi realizado na Floresta Nacional de São Francisco de Paula, RS, e teve como objetivo avaliar a periodicidade do crescimento das árvores de Araucaria angustifolia, correlacionando-a com variáveis meteorológicas. O comportamento do crescimento foi obtido partindo do acompanhamento quinzenal de periodicidade por meio da instalação de cintas dendrométricas à altura do peito de 48 árvores femininas e 48 árvores masculinas, avaliadas durante o período de agosto de 2003 a agosto de 2006. Os resultados deste trabalho permitiram concluir que o início do crescimento anual em diâmetro das árvores ocorre em setembro, tendo seu pico no mês de janeiro, começando a decrescer a partir de março. As variáveis meteorológicas, como temperatura e precipitação, estão diretamente correlacionadas com o incremento. O aumento da temperatura e da precipitação influi positivamente no incremento e a ocorrência de precipitação acompanhada de temperaturas baixas reduz o crescimento em diâmetro. Palavras-chave: incremento; diâmetro; cintas dendrométricas; fatores climáticos. ABSTRACTThis study was conducted at São Francisco de Paula National Forest, in the state of RS, Brazil, and had as its objective the evaluation of the periodicity growth of Araucaria angustifolia trees, and correlation with meteorological variables. Growth was measured biweekly in 48 female trees and 48 male trees using dendrometric bands installed at breast height. The results allowed us to conclude that the trees' annual growth in DBH starts in September, reaching its peak in January and starting to decrease in March, being almost null after the third week of April. Meteorological variables, such temperature and precipitation, were directly correlated with the increment. The increase in temperature and precipitation positively influence the increment and precipitation followed by low temperatures reduce growth in diameter.

RESUMOEste estudo teve por objetivo determinar o estoque de madeira por amostragem sistemática e pelas tecnologias de geoinformação a fim de elaborar mapas de produtividade florestal, como forma de pós-estratificação do inventário florestal. Foram alocadas 24 parcelas de 625 m 2 posicionadas a cada 70 m de distância. O mapa de produtividade foi gerado após seleção de um modelo para ajuste do semivariograma entre os volumes das parcelas. Estimou-se um volume total de 3.753,9 m 3 com o inventário florestal por amostragem sistemática, enquanto com o mapa de produtividade elaborado com técnicas de silvicultura de precisão determinou-se um volume total de 3.768,9 m 3 . A análise de variância comprovou que existe diferença significativa entre as médias dos estratos e a partir desta constatação as estimativas foram geradas por estrato, estimando-se então, um volume total de 3.772,9 m 3 . A técnica de silvicultura de precisão mostrou ser uma ferramenta eficiente na pós-estratificação de inventários florestais.Palavras-chave: variabilidade espacial, geoestatística, produtividade florestal. Forest Inventory Using Precision Forestry Techniques in Eucalyptus grandis Hill ex Maiden Stands ABSTRACTThis study aimed to determine the wood stock through systematic sampling and geoinformation technologies in order to elaborate maps of forest productivity as a forest post-stratification inventory. We positioned 24 plots of 625 m 2 each ina distance of 70 m from each other. The yield map was generated after selecting a model for semivariogram adjustment between volumes in the plots. A 3,753.9 m 3 total volume was estimated in the forest inventory through systematic sampling, while the yield map produced with precision forestry techniques showed a total volume of 3,768.9 m 3 . The analysis of variance showed that there is a significant difference between the means of the strata and based on this fact, the estimates were generated per stratum, then the total volume of 3,772.9 m 3 was estimated. The precision forestry technique proved to be an efficient tool in the post-stratification of forest inventories.

&lt;p&gt;&lt;strong&gt;Abstract.&lt;/strong&gt; The seasonal climate drivers of the carbon cycle in tropical forests remain poorly known, although these forests account for more carbon assimilation and storage than any other terrestrial ecosystem. Based on a unique combination of seasonal pan-tropical data sets from 89 experimental sites (68 include aboveground wood productivity measurements and 35 litter productivity measurements), their associate canopy photosynthetic capacity (enhanced vegetation index, EVI) and climate, we ask how carbon assimilation and aboveground allocation are related to climate seasonality in tropical forests and how they interact in the seasonal carbon cycle. We found that canopy photosynthetic capacity seasonality responds positively to precipitation when rainfall is &lt; 2000 mm.yr&lt;sup&gt;&amp;#8722;1&lt;/sup&gt; (water-limited forests) and to radiation otherwise (light-limited forests); on the other hand, independent of climate limitations, wood productivity and litterfall are driven by seasonal variation in precipitation and evapotranspiration respectively. Consequently, light-limited forests present an asynchronism between canopy photosynthetic capacity and wood productivity. Precipitation first-order control indicates an overall decrease in tropical forest productivity in a drier climate.&lt;/p&gt;