No abstract

The construction of hydroelectric dams causes changes in the diversity and floristic composition of floodplain forests due to the irregularity of the hydrological regime in rivers downstream from the dams. In the Amazon Basin, plans for the construction of dams are threatening the igapós, forests flooded by blackwater rivers. In these floodplains, the distribution of tree species is synchronized with periodic flood events of the topographic gradient. Previous studies on the Balbina Dam show an altered flood pulse downstream. This work discusses the potential long-term impacts on the diversity and floristic composition of an igapó downstream of the dam (Uatumã River) and compares it with an area unaffected by the dam (Abacate River). An evaluation of the vegetation strata-adults, saplings, and seedlings-showed that for all strata, diversity was greater in the high igapó (higher topographies) in the Uatumã area. This may be due to the near-total absence of flooding in the high igapó and to the extent of flooding in the low igapó (low topographies). Thus, in the Uatumã area, seeds of species typical of flooded areas cannot reach the high igapó by water and, thus, tend to be replaced by upland forest species (mainly seedlings). In the low igapó, the typical species have difficulty establishing. Therefore, the Uatumã vegetation forms two different communities, which does not occur in the Abacate area. These effects of the dam led to irreversible changes in the diversity and floristic composition across all strata throughout the entire topography in the downstream region.

Tropical peatlands are among the most carbon dense ecosystems but land-use change has led to the loss of large peatland areas, associated with substantial greenhouse gas emissions. In order to design effective conservation and restoration policies, maps of the location and carbon storage of tropical peatlands are vital. This is especially so in countries such as Peru where the distribution of its large, hydrologically intact peatlands is poorly known. Here, field and remote sensing data support model development of peatland extent and thickness for lowland Peruvian Amazonia. We estimate a peatland area of 62,714 (5th and 95th confidence interval percentiles 58,325-67,102 respectively) km 2 and carbon stock of 5.4 (2.6-10.6) Pg C, a value approaching the entire above-ground carbon stock of Peru but contained within just 5% of its land area. Combining the map of peatland extent with national land-cover data we reveal small but growing areas of deforestation and associated CO2 emissions from peat decomposition, due to conversion to mining, urban areas, and

Knowledge of the environmental correlates of species’ distributions is essential for understanding population dynamics, responses to environmental changes, biodiversity patterns, and the impacts of conservation plans. Here we examine how environment controls the distribution of the neotropical genus Montrichardia at regional and local spatial scales using species distribution models (SDMs) and logistic regression, respectively. Montrichardia is a genus of aquatic macrophytes with two species, Montrichardia linifera and Montrichardia arborescens, and is often an important component of flooded habitats. We find that for each species, altitude, precipitation and temperature of the driest month figure in the best performing SDMs as the most important factors controlling large-scale distributions, suggesting that the range limits of both species are climatically constrained by plant water-energy balance and cold intolerance. At small spatial scales, logistic regression models indicate the species partition types of aquatic habitat along local gradients of water pH, conductivity, and water transparency. In summary, a hierarchy of factors may control Montrichardia distribution from large to small spatial scales. While at large spatial scales, evolutionarily conserved climatic niches may control the range limits of the genus, at small spatial scales niche differentiation allows individual species to grow in environmentally distinct aquatic habitats

Minimal documentation exists for natural pollination in wild Vanilla spp., despite the economic importance of this genus, additionally commercial vanilla (V. planifolia Jacks.) is one of very few crops whose production depends entirely on artificial pollination. Flowering and fruiting phenology of Vanilla bicolor Lindl., a close relative of V. planifolia, was documented in a palm swamp in the Peruvian Amazon. V. bicolor was found to autofertilize via bagging experiments. This ecotype had an average fruit set per raceme of 42.50 ± 2.5%. Pollen removal experiments suggest that stigmatic leak may be the mechanism by which auto-pollination occurs in V. bicolor.

Wetlands harbor an important compliment of regional plant diversity, but in many regions data on wetland diversity and composition is still lacking, thus hindering our understanding of the processes that control it. While patterns of broad-scale terrestrial diversity and composition typically correlate with contemporary climate it is not clear to what extent patterns in wetlands are complimentary, or conflicting. To elucidate this, we consolidate data from wetland forest inventories in Brazil and examine patterns of diversity and composition along temperature and rainfall gradients spanning five biomes. We collated 196 floristic inventories covering an area >220 ha and including >260,000 woody individuals. We detected a total of 2,453 tree species, with the Amazon alone accounting for nearly half. Compositional patterns indicated differences in freshwater wetland floras among Brazilian biomes, although biomes with drier, more seasonal climates tended to have a larger proportion of more widely distributed species. Maximal alpha diversity increased with annual temperature, rainfall, and decreasing seasonality, patterns broadly consistent with upland vegetation communities. However, alpha diversity-climate relationships were only revealed at higher diversity values associated with the uppermost quantiles, and in most sites diversity varied irrespective of climate. Likewise, mean biome-level differences in alpha-diversity were unexpectedly modest, even in comparisons of savanna-area wetlands to those of nearby forested regions. We describe attenuated wetland climate-diversity relationships as a shifting balance of local and regional effects on species recruitment. Locally, excessive waterlogging strongly filters species able to colonize from regional pools. On the other hand, increased water availability can accommodate a rich community of drought-sensitive immigrant species that are able to track buffered wetland microclimates. We argue that environmental conditions in many wetlands are not homogeneous with respect to regional climate, and that responses of wetland tree communities to future climate change may lag behind that of non-wetland, terrestrial habitat.

No abstract

The large flood pulse of the Amazon basin is a principal driver of environmental heterogeneity with important implications for ecosystem function and the assembly of natural communities. Understanding species ecological response to the flood pulse is thus a key question with implications for theories of species coexistence, resource management, and conservation. Yet these remain largely undescribed for most species, and in particular for trees. The large flood pulse and high tree diversity of the Negro River floodplain makes it an ideal system to begin filling this knowledge gap. We merged historical hydrologic data with 41 forest inventories under variable flooding conditions distributed across the Negro River basin, comprising a total area of 34 ha, to (i) assess the importance of flood duration as a driver of compositional variation, (ii) model the response curve shapes of 111 of the most frequent tree species in function of flood duration, and (iii) derive their niche properties (optima and tolerance). We found that flood duration is a strong driver of compositional turnover, although the majority site-to-site variation in forest composition still remains unexplained. About 73% of species responded to the flood duration gradient, exhibiting a diversity of shapes, but most frequently skewed. About 29% of species were clearly favored by flood durations >120 days year–1, and 44% of species favored by shorter floods. The median niche breadth was 85 flood days year–1, corresponding to approximately 30% of the flood duration gradient. A significant subset of species (27%) did not respond to flooding, but rather exhibited wide tolerance to the flood gradient. The response models provided here offer valuable information regarding tree species differential capacity to grow, survive, and regenerate along an ecologically important gradient and are spatially valid for the Amazon Negro basin. These attributes make them an appealing tool with wide applicability for field and experimental studies in the region, as well as for vegetation monitoring and simulation models of floodplain forest change in the face of hydrologic alteration.