RESUMO -(Fitossociologia de uma floresta inundável monodominante de Vochysia divergens Pohl (Vochysiaceae), no Pantanal Norte, MT, Brasil). Cambarazais são formações florestais monodominantes de Vochysia divergens Pohl. O rápido espalhamento de cambarazais em campos sazonalmente inundados no Pantanal tem sido considerado um efeito de mudanças climáticas ocorridas em ciclos plurianuais. Realizado na RPPN SESC Pantanal, Barão de Melgaço, Mato Grosso (Brasil), o presente estudo, inserido no Programa de Pesquisas Ecológicas de Longa Duração (PELD), teve por objetivo analisar a estrutura do cambarazal presente na Reserva, ao longo de um gradiente hidro-topográfico. Os dados fitossociológicos foram coletados em quatro áreas de 1 ha (100×100 m). Todos os indivíduos com CAP (Circunferência à Altura do Peito) ≥ 5 cm foram identificados, medidos seus perímetros e estimadas suas alturas. Um total de 3.149 indivíduos foi amostrado nos quatro hectares e 83 espécies foram identificadas. A diversidade de espécies ao longo do gradiente mostrou relação inversa com a altura da lâmina de água da inundação. A parcela com menor nível de inundação (P1) obteve o maior índice de diversidade de espécies dentre as parcelas (H' = 2,9) e baixa densidade e dominância de V. divergens. As demais parcelas foram identificadas como formações monodominantes de V. divergens, devido à sua dominância de mais de 50% dentro de cada parcela.Palavras-chave: estrutura, cambarazal, planície de inundação, monodominância, pulso de inundação. . It aims to analyze structural and phytosociological data collected in four areas of one hectare each of "cambarazal" along a hydro-topographical gradient. All individuals with cbh (circumference at breast height) ≥ 5cm were identified, perimeters were measured and heights were estimated. In the entire sample area, 3,149 individuals belonging to 83 species were registered. Species diversity along the gradient showed an inverse relationship with floodwater levels. The plot with the lowest level of flooding (P1) had the highest species diversity index (H' = 2.91) of the sampled plots and the lowest values of V. divergens density and dominance. The other plots were considered to be V. divergens monodominant formations, since relative dominance of this species in these areas was greater than 50%. ABSTRACT -(Phytosociology of a monodominant flooded forest of Vochysia divergens

Abstract. In this study we use allometric models combined with tree ring analysis to estimate carbon stocks and sequestration in the aboveground coarse wood biomass (AGWB) of wetland forests in the Pantanal, located in central South America. In four 1-ha plots in stands characterized by the pioneer tree species Vochysia divergens Pohl (Vochysiaceae) forest inventories (trees ≥10 cm diameter at breast height, D) have been performed and converted to estimates of AGWB by two allometric models using three independent parameters (D, tree height H and wood density ρ). We perform a propagation of measurement errors to estimate uncertainties in the estimates of AGWB. Carbon stocks of AGWB vary from 7.8 ± 1.5 to 97.2 ± 14.4 Mg C ha −1 between the four stands. From models relating tree ages determined by dendrochronological techniques to C-stocks in AGWB we derived estimates for C-sequestration which differs from 0.50 ± 0.03 to 3.34 ± 0.31 Mg C ha −1 yr −1 . Maps based on geostatistic techniques indicate the heterogeneous spatial distribution of tree ages and C-stocks of the four studied stands. This distribution is the result of forest dynamics due to the colonizing and retreating of V. divergens and other species associated with pluriannual wet and dry episodes in the Pantanal, respectively. Such information is essential for the management of the cultural landscape of the Pantanal wetlands.

Abstract. Development of efficient methodologies for mapping wetland vegetation is of key importance to wetland conservation. Here we propose the integration of a number of statistical techniques, in particular cluster analysis, universal kriging and error propagation modelling, to integrate observations from remote sensing and field sampling for mapping vegetation communities and estimating uncertainty. The approach results in seven vegetation communities with a known floral composition that can be mapped over large areas using remotely sensed data. The relationship between remotely sensed data and vegetation patterns, captured in four factorial axes, were described using multiple linear regression models. There were then used in a universal kriging procedure to reduce the mapping uncertainty. Cross-validation procedures and Monte Carlo simulations were used to quantify the uncertainty in the resulting map. Cross-validation showed that accuracy in classification varies according with the community type, as a result of sampling density and configuration. A map of uncertainty derived from Monte Carlo simulations revealed significant spatial variation in classification, but this had little impact on the proportion and arrangement of the communities observed. These results suggested that mapping improvement could be achieved by increasing the number of field observations of those communities with a scattered and small patch size distribution; or by including a larger number of digital images as explanatory variables in the model. Comparison of the resulting plant community map with a flood duration map, revealed that flooding duraCorrespondence to: J. Arieira (juarieira@ufmt.br) tion is an important driver of vegetation zonation. This mapping approach is able to integrate field point data and highresolution remote-sensing images, providing a new basis to map wetland vegetation and allow its future application in habitat management, conservation assessment and long-term ecological monitoring in wetland landscapes.

Question The encroachment of woody species has been globally reported over much of arid and semi‐arid biomes, and has been associated with a decrease in cover and number of herbaceous species. How does the encroachment of a woody shrub affect herbaceous community structure and species composition in grasslands of a wetland ecosystem? Location Seasonally flooded grasslands in a Neotropical Hyperseasonal Savanna, the Pantanal wetland, Brazil. Methods We investigated the effect of the encroaching plant Combretum laxum on a herbaceous community from seasonally flooded grasslands in the Pantanal wetland using 29 vegetation samples representing encroachment at different spatio‐temporal stages. The point quadrat method was used to acquire vegetation data, as plant cover, species richness (S) and Shannon‐Wiener diversity index (H’). We evaluated the existence of stages of encroachment related to differences in vegetation structure and species composition using non‐metric multidimensional scaling ordination and analysis of similarity. The response of the herbaceous community to shrub advance was analysed using linear and quadratic polynomial regression models. Model fitness was tested using the ACI. Results The advance of the woody encroaching plant C. laxum over the seasonally flooded grassland occurs in three stages: grassland stage, shrub islands stage and shrubland stage. The initial advance of C. laxum over the grassland, represented by the shrub islands stage was correlated to an increase in species richness and a decrease in important native forage grasses. Critical changes in the herbaceous community were observed when the encroaching plant covered >30% of the periodically flooded grassland, when the richness of herbaceous species dropped from 22 to four. Conclusions Woody encroachment causes impoverishment and simplification of the herbaceous community. The shift from a grass‐ to a shrub‐dominated state is related to the reduction in important grassland‐obligate species, forage resources for herbivore livestock and wild animals, affecting the ecological dynamics and the economy of rangelands. Conservation of these grassland ecosystems depends on rangeland management practices guided by scientific knowledge on the causes and consequences of plant community changes.

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Vochysia divergens Pohl (cambará) ocorre em densos estandes monodominantes no Pantanal, denominadas cambarazais. O presente estudo, realizado na Reserva Particular do Patrimônio Natural (RPPN) SESC Pantanal, Barão de Melgaço, Mato Grosso (Brasil), visou caracterizar uma população de V. divergens, ao longo de um gradiente hidro-topográfico quanto à sua estrutura de tamanho (diâmetro e altura) e idade e ainda verificar as relações entre sua densidade e área basal com variáveis edáficas (pH, Al, carbono orgânico e teor de argila). O estudo foi realizado em quatro parcelas de 1ha (100m x 100m) (P1 a P4). Todos os indivíduos de cambará com CAP ≥ 5cm foram amostrados, seus perímetros medidos e alturas estimadas para obtenção dos parâmetros estruturais. Um total de 656 indivíduos de V. divergens foi contado nas quatro parcelas amostradas. Valores acima de 50% de dominância do cambará foram encontrados nas parcelas P2, P3 e P4, caracterizando a monodominância do cambará. O estande com a população mais velha de cambará (156 anos), localizado no centro do cambarazal (P3), parece funcionar como área central de espalhamento do cambará em direção às áreas adjacentes, P1 (48 anos), P2 (100 anos) e P4 (102 anos). O desenvolvimento sucessional desta floresta monodominante está associado ao aumento da concentração de indivíduos com maior altura (> 20m) e com diâmetro de tamanho intermediário (43,8 a 51,1cm). A verificação da influência dos fatores edáficos sobre a população foi feita no estande mais velho de cambará. Observou-se que solos mais ácidos foram encontrados sob áreas com maior dominância e densidade do cambará. O exemplo do cambará ilustrado neste trabalho mostrou que formações florestais sazonalmente inundáveis no Pantanal estão sujeitas a uma dinâmica populacional intensa associada a processos de expansão e retração de suas populações. Palavras-chave: espalhamento; gradiente hidro-topográfico; parâmetros estruturais; planície de inundação; solo. ABSTRACT POPULATION STRUCTURE OF CAMBARÁ (VOCHYSIA DIVERGENS POHL, VOCHYSIACE-AE), MONODOMINANT SPECIES IN FLOODABLE FOREST IN THE PANTANAL MATO-GROS-SENSE). Vochysia divergens Pohl (cambará) occurs in dense monodominant stands in the Pantanal, called cambarazal. The present study, carried out in the RPPN SESC Pantanal (Nature Patrimony Private Reserve-NPPR), Barão de Melgaço, Mato Grosso (Brazil) aimed mainly at characterizing the population of V. divergens along a hydro-topographical gradient with respect to its size (diameter and height) and age structure and still verifying the relations between population density and basal area with edaphic variables (pH, Al, organic carbon and clay content). The study was carried out in four plots (P1 to P4) of one hectare each (100m x 100m) established within a cambarazal. For this, all individuals of cambará with CBH (Circumference at Breast Height) ≥ 5 cm were sampled, their perimeter measured and height estimated to derive structural parameters. In total, 656 individuals of V. divergens were sampled in the four plots. Dominance valu...

Abstract. This is the first estimation on carbon dynamics in the aboveground coarse wood biomass (AGWB) of wetland forests in the Pantanal, located in Central Southern America. In four 1-ha plots in stands characterized by the pioneer species Vochysia divergens Pohl (Vochysiaceae) forest inventories (trees ≥10 cm diameter at breast height, DBH) have been performed and converted to predictions of AGWB by five different allometric models using two or three predicting parameters (DBH, tree height, wood density). Best prediction has been achieved using allometric equations with three independent variables. Carbon stocks (50% of AGWB) vary from 7.4 to 100.9 Mg C ha−1 between the four stands. Carbon sequestration differs 0.50–4.24 Mg C ha−1 yr−1 estimated by two growth models derived from tree-ring analysis describing the relationships between age and DBH for V. divergens and other tree species. We find a close correlation between estimated tree age and C-stock, C-sequestration and C-turnover (mean residence of C in AGWB).