Current practices of conducting forest management plans in the Amazon may risk the survival of timber species.

Measurement of the recovery of wood stocks in logging areas in the Amazon helps to understand the efficiency of policies for the use and conservation of native forests. This work evaluated the effects of logging on the dynamics and production of commercial species in the short and medium term in a conservation unit in the state of Rondônia. Structural patterns of the species as a function of mortality and recruitment rates, patterns of average increment in diameter, and estimates of forest production in the short and medium term were analyzed. The study was carried out in an area designated as Annual Production Unit 2 of Forest Management Unit III of Jamari National Forest. In addition to legalized harvesting, there are reports of illegal logging in the area as of 2015. Inventory data from 2011, 2015, and 2018 were used, considering trees of commercial value with a diameter at breast height (DBH) greater than 10 cm. Mortality rate, recruitment, periodic annual increment, absolute tree density, basal area, and commercial volume, by species and DBH classes, as well as the similarity of the species regarding the growth pattern. The population structure of species over the years was affected by tree mortality, mainly due to damage caused by illegal logging. Mean increment values varied by species and diameter classes, and six species represented 72% of the total volume of wood stock. It is important to review the criteria for sustainable forest production in the long term. Thus, it is necessary to promote species diversity and improve public authorities' capacity to enforce and of the private sector to comply with legislation. This, in turn, will enable the development of strategies to make the consumption of legal wood more rational.

Environmental filtering in the dry season and spatial structuring in the wet: different fish community assembly rules revealed in a large subtropical floodplain lake.

Although environmental filtering and spatial structuring are commonly regarded as two key factors shaping community dynamics, their relative contribution remains unknown for numerous aquatic ecosystems, particularly highly dynamic floodplain lakes. This issue is here addressed by examining the seasonal metacommunity dynamics of freshwater fishes in Lake Dongting, a large subtropical lake of the middle Chang-Jiang basin in southern China. Physicochemical variables and fish assemblages were recorded at 20 sampling sites during the wet, normal, and dry seasons. Distance-based redundancy analysis and associated variation partitioning were used to examine the relative role of environmental variables and spatial factors in fish community assembly in each season. Analysis results demonstrated that the relative contribution of environmental filtering and spatial structuring varied depending on environmental features and the extent of hydrological connectivity in different seasons. Intensified physicochemical parameters in the dry season convinced the enhanced environmental filtering, whereas high hydrological connectivity in the wet season favored the stronger spatial process. Specifically, the community assembly processes were temporally dynamic; spatial structuring (or mass effects), resulting from excessively high dispersal rates, was dominant during the flooding season, and environmental filtering was stronger than spatial structuring (or dispersal limitation) during the non-flooding season. These findings highlight the importance of conserving local habitats of Lake Dongting during the dry and normal seasons, and maintaining of the flood pulse of the lake and its natural variability during the wet season. Apparently, the construction of a water-level regulation project at the Chenglingji Channel, the outlet watercourse of Lake Dongting, is not supported because it will change the flood pulse of this lake and thus impact habitat heterogeneity or variability.

Efeito de fatores ambientais e espaciais sobre assembléias de peixes de pequeno porte em um rio tropica / Effect of environmental and spatial factors on small-sized fish assemblages in a tropical river

O conceito de rio continuo prediz que mudanças graduais na geomorfologia e hidrologia de um rio podem causar mudanças longitudinais na estrutura de comunidades aquáticas. Nesse contexto, avaliamos como variáveis ambientais (condutividade elétrica, pH, transparência e velocidade da água), fatores espaciais (distância da cabeceira e Moran's eigen vector maps ­ MEMs) e presença de barragens afetam as assembleias de peixes de pequeno porte ao longo de um trecho de 105 km do alto Rio Branco, um tributário do Rio Madeira, bacia Amazônica, Brasil. Coletas com rede de arrasto foram realizadas em 15 pontos a jusante e montante de barragens durante a estação seca de 2019. Capturamos um total de 4.330 indivíduos, distribuídos em três ordens, nove famílias e 26 espécies (e um indivíduo híbrido). Condutividade elétrica e pH foram afetados significativamente pela presença de barragens e pela distância da cabeceira. A riqueza de espécies e a abundância não variaram em função das variáveis ambientais. Ao contrário da riqueza de espécies, que não variou ao longo do trecho amostrado, a abundância apresentou uma relação negativa com a distância da cabeceira. A composição de espécies variou significativamente em resposta ao pH, a fatores espaciais lineares e à presença de barragens. Nossos resultados sugerem que a mudanças na composição de espécies de peixes de pequeno porte no alto Rio Branco ocorre devido à variação em características da água, em função da limitação na dispersão inerente das espécies e em resposta à presença de barragens(AU)

A dimensão espacial e temporal da diversidade de peixes da zona litoral vegetada de lagoas marginais da planície de inundação do rio Cuiabá, Pantanal, Brasil / The spatial and temporal dimension of fish diversity of the vegetated littoral zone of marginal lagoons of the Cuiabá river floodplain, Pantanal, Brazil

O presente trabalho avaliou a distribuição espacial e temporal da riqueza de espécies de peixes da zona litoral vegetada de 15 lagoas marginais da planície de inundação do Rio Cuiabá, Pantanal. As lagoas foram amostradas em três períodos ao longo da sessão seca (junho, setembro e dezembro de 2005), por meio de nove lances de peneira, distribuídos sistematicamente a uma distância mínima de cinco metros um do outro. Capturamos 12.784 indivíduos pertencentes a sete ordens, 21 famílias e 98 espécies. A maioria das espécies capturadas foi rara e apresentou distribuição geográfica restrita. A intensificação da seca não afetou a distribuição espacial das espécies e a perda de espécies nas diferentes ordens, ao longo da seca, foi proporcional. Tanto a abundância total de indivíduos quanto a riqueza variou no tempo. As curvas de rarefação indicaram que a redução na riqueza foi um artefato da redução na abundância de indivíduos. Quando comparamos as riquezas estimadas sob um mesmo nível de abundância não encontramos diferença entre a riqueza de espécies no início e no final da seca. Os estimadores de riqueza de espécies indicaram que distribuir as amostras no tempo foi uma estratégia adequada para reduzir o problema das falsas ausências e melhorar a eficiência da amostragem. Assim, nossos resultados sugerem que para o delineamento de reservas no Pantanal, áreas com um grande número de lagoas com diferentes formas e tamanhos conservaria um maior contingente da diversidade regional de peixes, pois a maioria das espécies de pequeno porte apresenta distribuição restrita a poucas lagoas.

The present work has evaluated the spatial and temporal distribution of fish species richness of the vegetated littoral zone of 15 marginal lagoons in the floodplain of the Cuiabá River, Pantanal. The lagoons were sampled in three periods along of the dry season (June, September and December of 2005), through nine sieve throws distributed systematically at a minimum distance of five meters from each other. We caught 12,784 individuals belonging to seven orders, 21 families and 98 species of fish. Most of the captured species were rare and presented restricted geographical distribution. Drought intensification did not affect the spatial species distribution and the loss of species as dry season proceeded was proportional in the different orders. The total abundance of individuals as well as the richness varied with time. Rarefaction curves indicated that the reduction in richness was an artifact of the reduction in the abundance of individuals. When we compared the estimated richness under a same abundance level we did not find difference among the richness of species in the beginning and at the end of the dry season. Richness estimators indicated that to distribute the samples in the time was an appropriate strategy to reduce the problem of the false absences and to improve the efficiency of the sampling. Thus, our results suggest that for the design of reserves in the Pantanal, areas with a large number of lagoons of different forms and sizes would conserve the regional fish diversity, as the distribution of most small size species is restricted to a few lagoons.