Variação espacial e temporal da biomassa arbórea viva em 64 km² de floresta de terra-firme na Amazônia Central

A variação espacial e temporal nas estimativas de biomassa arbórea viva acima do solo (AGLB) e suas relações com solo e topografia (altitude e inclinação do terreno) foram investigadas em parcelas permanentes distribuídas sistematicamente sobre 64 km², na Reserva Florestal Adolpho Ducke, Manaus, Amazonas. No total, foram instaladas 72 parcelas compridas (250 m) e estreitas (40 m), que seguiram as curvas de nível, cobrindo toda a variação de solo e topografia existente na Reserva. Indivíduos com diâmetro à altura do peito (DAP) = 30 cm foram amostrados em uma área de 1 ha e sub­amostras de 0,5 e 0,1 ha foram utilizadas para indivíduos com 10 cm = DAP 30 cm e 1 cm = DAP 10 cm, respectivamente. Análises químicas e físicas do solo foram feitas em amostras coletadas abaixo do horizonte Ah (0-5 cm de profundidade), em cada parcela. As medidas de altitude de cada parcela foram obtidas por um topógrafo profissional. A inclinação de cada parcela representa uma média de cinco medidas, feitas a cada 50 m, ao longo do maior eixo da parcela. O peso seco das árvores foi obtido a partir de uma combinação de equações alométricas utilizando o DAP de árvores = 1 cm. A AGLB variou de 215-421 Mg/ha, sendo a média 321,8 Mg/ha (IC95% = 10,4). Uma Análise de Componentes Principais a partir das variáveis edáficas revelou um gradiente principal na estrutura do solo relacionado com a proporção de argila. Regressões múltiplas utilizando os eixos do PCA com variáveis do solo mineral ou do solo total (solo mineral + compostos orgânicos) e a inclinação do terreno explicaram cerca de 30% da variação espacial das estimativas de biomassa. A AGLB foi positivamente relacionada com um gradiente de textura do solo (eixo 1 do PCA) e negativamente relacionada à inclinação do terreno. Um modelo utilizando somente as variáveis topográficas (altitude e inclinação) explicou 29% da variação encontrada nas estimativas de AGLB. A AGLB aumentou com a altitude e decresceu com o aumento da inclinação. As mesmas análises utilizando parcelas de 1 ha em projeção horizontal revelaram que a biomassa arbórea não foi afetada pela inclinação do terreno, indicando que um limite de área horizontal, como a área da copa, pode ser mais importante do que a quantidade de chão disponível para as árvores. A variação temporal nas estimativas de biomassa arbórea foi avaliada após um perlodo de 2 anos. Todos os indivíduos de 37 parcelas foram re-medidos para calcular a taxa de mudança de biomassa arbórea viva (crescimento + recrutamento ­mortalidade). A biomassa arbórea nas parcelas analisadas aumentou no período de estudo (teste t pareado: t = 3,15; P = 0,003), confirmando a tendência de aumento em biomassa nas florestas amazônicas. As taxas de mudança de biomassa também foram relacionadas com as características do solo, com parcelas localizadas em solos arenosos apresentando geralmente taxas negativas. O uso de garras, para coleta de material botânico, não afetou o crescimento ou sobrevivência das árvores escaladas, após um período mínimo de 1 ano e meio; portanto, as taxas de mudança não podem ser atribuídas ao efeito da metodologia utilizada. Os resultados obtidos para Reserva Ducke indicam que o poder preditivo das variáveis edáficas e topográficas, na variação espacial e temporal da biomassa arbórea, poderá ser utilizado para melhorar as estimativas de carbono estocado em florestas amazônicas

Decomposition rates of coarse woody debris in undisturbed Amazonian seasonally flooded and unflooded forests in the Rio Negro-Rio Branco Basin in Roraima, Brazil

Estimates of carbon-stock changes in forest ecosystems require information on dead wood decomposition rates. In the Amazon, the lack of data is dramatic due to the small number of studies and the large range of forest types. The aim of this study was to estimate the decomposition rate of coarse woody debris (CWD) in two oligotrophic undisturbed forest formations of the northern Brazilian Amazon: seasonally flooded and unflooded. We analyzed 20 arboreal individuals (11 tree species and 3 palm species) with distinct wood-density categories. The mean annual decomposition rate of all samples independent of forest formation ranged from 0.044 to 0.963 yr−1, considering two observation periods (12 and 24 months). The highest rate (0.732 ± 0.206 [SD] yr−1) was observed for the lowest wood-density class of palms, whereas the lowest rate (0.119 ± 0.101 yr−1) was determined for trees with high wood density. In terms of forest formation, the rates values differ when weighted by the wood-density classes, indicating that unflooded forest (0.181 ± 0.083 [SE] yr−1; mean decay time 11–30 years) has a decomposition rate ∼19% higher than the seasonally flooded formations (0.152 ± 0.072 yr−1; 13–37 years). This result reflects the dominance of species with high wood density in seasonally flooded formations. In both formations 95% of the dead wood is expected to disappear within 30–40 years. Based on our results, we conclude that the CWD decomposition in the studied area is slower in forests on nutrient-poor seasonally flooded soils, where structure and species composition result in ∼40% of the aboveground biomass being in tree species with high wood density. Thus, it is estimated that CWD in seasonally flooded forest formations has longer residence time and slower carbon release by decomposition (respiration) than in unflooded forests. These results improve our ability to model stocks and fluxes of carbon derived from decomposition of dead wood in undisturbed oligotrophic forests in the Rio Negro-Rio Branco Basin, northern Brazilian Amazon. © 2017 The Author

ATLANTIC-CAMTRAPS: a dataset of medium and large terrestrial mammal communities in the Atlantic Forest of South America

Our understanding of mammal ecology has always been hindered by the difficulties of observing species in closed tropical forests. Camera trapping has become a major advance for monitoring terrestrial mammals in biodiversity rich ecosystems. Here we compiled one of the largest datasets of inventories of terrestrial mammal communities for the Neotropical region based on camera trapping studies. The dataset comprises 170 surveys of medium to large terrestrial mammals using camera traps conducted in 144 areas by 74 studies, covering six vegetation types of tropical and subtropical Atlantic Forest of South America (Brazil and Argentina), and present data on species composition and richness. The complete dataset comprises 53,438 independent records of 83 species of mammals, includes 10 species of marsupials, 15 rodents, 20 carnivores, eight ungulates and six armadillos. Species richness averaged 13 species (±6.07 SD) per site. Only six species occurred in more than 50% of the sites: the domestic dog Canis familiaris, crab-eating fox Cerdocyon thous, tayra Eira barbara, south American coati Nasua nasua, crab-eating raccoon Procyon cancrivorus and the nine-banded armadillo Dasypus novemcinctus. The information contained in this dataset can be used to understand macroecological patterns of biodiversity, community, and population structure, but also to evaluate the ecological consequences of fragmentation, defaunation, and trophic interactions. © 2017 by the Ecological Society of Americ

MASTREE+: Time-series of plant reproductive effort from six continents.

Significant gaps remain in understanding the response of plant reproduction to environmental change. This is partly because measuring reproduction in long-lived plants requires direct observation over many years and such datasets have rarely been made publicly available. Here we introduce MASTREE+, a data set that collates reproductive time-series data from across the globe and makes these data freely available to the community. MASTREE+ includes 73,828 georeferenced observations of annual reproduction (e.g. seed and fruit counts) in perennial plant populations worldwide. These observations consist of 5971 population-level time-series from 974 species in 66 countries. The mean and median time-series length is 12.4 and 10 years respectively, and the data set includes 1122 series that extend over at least two decades (≥20 years of observations). For a subset of well-studied species, MASTREE+ includes extensive replication of time-series across geographical and climatic gradients. Here we describe the open-access data set, available as a.csv file, and we introduce an associated web-based app for data exploration. MASTREE+ will provide the basis for improved understanding of the response of long-lived plant reproduction to environmental change. Additionally, MASTREE+ will enable investigation of the ecology and evolution of reproductive strategies in perennial plants, and the role of plant reproduction as a driver of ecosystem dynamics

Climate seasonality limits leaf carbon assimilation and wood productivity in tropical forests

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 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

Averting biodiversity collapse in tropical forest protected areas

The rapid disruption of tropical forests probably imperils global biodiversity more than any other contemporary phenomenon¹⁻³. With deforestation advancing quickly, protected areas are increasingly becoming final refuges for threatened species and natural ecosystem processes. However, many protected areas in the tropics are themselves vulnerable to human encroachment and other environmental stresses⁴⁻⁹. As pressures mount, it is vital to know whether existing reserves can sustain their biodiversity. A critical constraint in addressing this question has been that data describing a broad array of biodiversity groups have been unavailable for a sufficiently large and representative sample of reserves. Here we present a uniquely comprehensive data set on changes over the past 20 to 30 years in 31 functional groups of species and 21 potential drivers of environmental change, for 60 protected areas stratified across the world’s major tropical regions. Our analysis reveals great variation in reserve ‘health’: about half of all reserves have been effective or performed passably, but the rest are experiencing an erosion of biodiversity that is often alarmingly widespread taxonomically and functionally. Habitat disruption, hunting and forest-product exploitation were the strongest predictors of declining reserve health. Crucially, environmental changes immediately outside reserves seemed nearly as important as those inside in determining their ecological fate, with changes inside reserves strongly mirroring those occurring around them. These findings suggest that tropical protected areas are often intimately linked ecologically to their surrounding habitats, and that a failure to stem broad-scale loss and degradation of such habitats could sharply increase the likelihood of serious biodiversity declines.Keywords: Ecology, Environmental scienc

Uma abordagem baseada em regras heuristicas para construcao de especificacoes diagramaticas de requisitos

Este trabalho apresenta uma abordagem para elicitação e especificação de requisitos com o uso de ferramentas automatizadas baseadas em conhecimento. As especificações geradas são representadas em notações diagramáticas (diagramas), e as bases de conhecimento contêm regras heurísticas coletadas através de estudos de casos e análise de procedimentos. A vantagem do uso de conhecimento declarativo (representado pelas regras heurísticas) é que as tarefas referentes ao processo de Engenharia de Requisitos dificilmente poderiam ser realizadas automaticamente através de processos algorítmicos. Neste artigo, são discutidos dois experimentos de especificação segundo a abordagem (um deles gera um diagrama E-R e outro, um DFD).This work presents an approach to requirements elicitation and specification through the use of automatic tools and knowledge bases. Specifications are represented in diagramatic notations and knowledge bases use heuristic rules. The main benefit to the Requirements Engineering process is the use of declarative knowledge instead of procedural one. In this article, experiments that generate an E-R Model and a Data Flow Diagrarri are discussed