Wetlands are important providers of ecosystem services and key regulators of climate change. They positively contribute to global warming through their greenhouse gas emissions, and negatively through the accumulation of organic material in histosols, particularly in peatlands. Our understanding of wetlands' services is currently constrained by limited knowledge on their distribution, extent, volume, interannual flood variability and disturbance levels. We present an expert system approach to estimate wetland and peatland areas, depths and volumes, which relies on three biophysical indices related to wetland and peat formation: (1) long-term water supply exceeding atmospheric water demand; (2) annually or seasonally water-logged soils;and (3) a geomorphological position where water is supplied and retained. Tropical and subtropical wetlands estimates reach 4.7 million km 2 (Mkm 2 ). In line with current understanding, the American continent is the major contributor (45%), and Brazil, with its Amazonian interfluvial region, contains the largest tropical wetland area (800,720 km 2 ). Our model suggests, however, unprecedented extents and volumes of peatland in the tropics (1.7 Mkm 2 and 7,268 (6,076-7,368) km 3 ), which more than threefold current estimates. Unlike current understanding, our estimates suggest that South America and not Asia contributes the most to tropical peatland area and volume (ca. 44% for both) partly related to some yet unaccounted extended deep deposits but mainly to extended but shallow peat in the Amazon Basin. Brazil leads the peatland area and volume contribution. Asia hosts 38% of both tropical peat area and volume with Indonesia as the main regional contributor and still the holder of the deepest and most extended peat areas in the tropics. Africa hosts more peat than previously reported but climatic and topographic contexts leave it as the least peat-forming continent. Our results suggest large biases in our current understanding of the distribution, area and volumes of tropical peat and their continental contributions.

The Amazon basin is covered by the most species-rich forests in the world and is considered to house many endemic tree species. Yet, most Amazonian ecosystems lack reliable estimates of their degree of endemism, and causes of tree diversity and endemism are intense matters of debate. We reviewed the spatial distribution of 658 of the most important floodtolerant Amazonian white-water (várzea) tree species across the entire Neotropics by using data from herbaria, floras, inventories and checklists. Our results show that 90% of the várzea tree species are partially or widely distributed across neotropical macro-regions and biomes. Chi-square analyses indicated that várzea species richness in non-várzea macro-regions was dependent on the flooding gradient and the longitudinal position. Cluster analysis combined with association tests indicated four significant patterns of várzea species distributions depending on species flood-tolerance (low vs high) and spatial distribution (restricted vs widespread). We predict that the predominance of Andean substrates is the most important factor that determines the distribution of várzea tree species within and beyond the Amazon basin and explains the high floristic similarity to the Orinoco floodplains. Distribution patterns in other extra-Amazonian macro-regions are more likely linked to climatic factors, with rainforest climates housing more várzea species than savanna climates. 130 tree species were restricted to South-American freshwater floodplains, and 68 ( 10%) were endemic to Amazonian várzea. We detected two centers of endemism, one in the western Amazon characterized by low and brief floods, and one in the central Amazon, characterized by high and prolonged floods. Differences in taxonomic composition of endemic centers in the western and central Amazon are the result of different abiotic factors (i.e. flood regimes), as well as the regional species pools from where the species are recruited from.We hypothesize that numerous morphological, physiological and biochemical adaptations permit survival of trees in flooded environments. Furthermore, these adaptations are independently derived across many taxa and result in a highly specialized flora. We attribute higher than expected levels of endemism to the great spatial extent and age of floodplain ecosystems in the Amazon basin, and highlight the role of Amazonian várzea as an potential driver in speciation and diversification processes.Freshwater floodplains cover an area of approximately 1.7 million square kilometres within the Amazon basin and include seasonally inundated forests, riparian zones, swamps, and high elevation bogs (Junk et al. 2011). Many Amazonian tree species are adapted to cope with permanently, seasonally or episodically waterlogged soils and associated disturbance, such as hypoxia or anoxia. The inundation of roots and/or aboveground organs of trees reduces oxygen supply to submerged tissues and thus is widely considered a potential stress factor (Armstrong et al. 1994). Trees subject to waterlogg...

This review presents the current knowledge regarding South American wetlands and summarizes major outcomes of the implementation of the Ramsar Convention on Wetlands of International Importance for the South American continent. South America is the wettest continent on Earth, with wetlands accounting for ∼20% of its area. Wetlands harbor an exceptional rich biodiversity also including many endemic plant and animal species. They provide numerous ecosystem services in terms of provisioning material goods, regulating biogeochemical cycles, providing habitat, sustaining cultural practices, and importantly, contributing to the maintenance and generation of regional biodiversity. Major threats to wetlands include agroindustrial expansion, deforestation, soil erosion, mining, pollution, inadequate resource use, and large infrastructural projects such as reservoir construction for hydropower. South American countries were slow in adopting definitions, delineations, and classifications of their wetlands and in inventorying wetlands according to their extent and ecological characteristics. However, Ramsar sites are increasing continuously in both numbers and extent, covering 113 sites, totaling an area of ∼373,000 km 2. Threats to wetlands and Ramsar sites are ongoing, mainly because of the lack of specific national wetland policies, limited financial and human resources, general lack of infrastructure, and limited monitoring capacity. The process of changing perceptions on the value of wetlands and their ecosystem services is improving, but it could be hastened by improved infrastructure and cooperation between Ramsar sites, wetland scientists, and local stakeholders. Outreach to raise awareness of societies, administrators, and governments of the critical importance of wetlands continues to be a major challenge for the conservation of South American wetlands.

Salvage logging and replanting reduce understory cover and Salvage logging and replanting reduce understory cover and richness compared to unsalvaged-unplanted sites at Mount St. richness compared to unsalvaged-unplanted sites at ABSTRACT.-The 1980 eruption of Mount St. Helens killed trees in a broad 600-km 2 swath north of the crater. Over most of the blast zone, dead trees were salvage logged and Abies procera was planted, except in areas within the Mount St. Helens National Volcanic Monument. We compared salvage-replanted sites and unsalvaged sites in 1 area of the blast zone where the sites were adjacent by using twenty-five 200-m 2 plots for each treatment. Salvaged-replanted plots had significantly lower herb and shrub cover, richness, diversity, litter depth, downed woody debris, nitrate, and phosphate. Salvaged-replanted sites also had significantly more stumps, bare area, and moss cover than unsalvaged plots. Soil organic matter and nonnative species cover did not differ. Nonnative species were not important components of any plots. Nitrate, total nitrogen, organic matter, and litter were correlated with the major patterns of species distribution in a canonical correspondence analysis of the salvaged-replanted plots. In the unsalvaged plots, slope, downed woody debris, and elevation were correlated with the major patterns of species distribution.

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