The geochemistry of Amazonian peats

The chemical, physical and palaeobotanical composition of peat can be used to infer the history of a peatland and the processes presently operating within it. Here we present new data on the geochemistry of a peat sequence from a lowland palm swamp, Quistococha, in Peruvian Amazonia. We show, through comparison with subfossil pollen data from the same sequence, that changes in the depositional environment cause changes in peat properties including lignin content, C/N ratios, and the abundance of several metal cations, but that these properties are altered by post-depositional processes to a large extent. An upward trend in the top 1.5 m of the sequence in the concentrations of N, K, Ca, Mg and Na probably reflects nutrient uptake and cycling by the standing biomass. Upward trends in Mn and Fe concentrations suggest that limited oxygenation of the peat may occur to a similar depth. Comparison with other published records suggests that such deep biological alteration may be characteristic of tropical forested peats

Local hydrological conditions influence tree diversity and composition across the Amazon basin

Tree diversity and composition in Amazonia are known to be strongly determined by the water supplied by precipitation. Nevertheless, within the same climatic regime, water availability is modulated by local topography and soil characteristics (hereafter referred to as local hydrological conditions), varying from saturated and poorly drained to well-drained and potentially dry areas. While these conditions may be expected to influence species distribution, the impacts of local hydrological conditions on tree diversity and composition remain poorly understood at the whole Amazon basin scale. Using a dataset of 443 1-ha non-flooded forest plots distributed across the basin, we investigate how local hydrological conditions influence 1) tree alpha diversity, 2) the community-weighted wood density mean (CWM-wd) – a proxy for hydraulic resistance and 3) tree species composition. We find that the effect of local hydrological conditions on tree diversity depends on climate, being more evident in wetter forests, where diversity increases towards locations with well-drained soils. CWM-wd increased towards better drained soils in Southern and Western Amazonia. Tree species composition changed along local soil hydrological gradients in Central-Eastern, Western and Southern Amazonia, and those changes were correlated with changes in the mean wood density of plots. Our results suggest that local hydrological gradients filter species, influencing the diversity and composition of Amazonian forests. Overall, this study shows that the effect of local hydrological conditions is pervasive, extending over wide Amazonian regions, and reinforces the importance of accounting for local topography and hydrology to better understand the likely response and resilience of forests to increased frequency of extreme climate events and rising temperatures

A global reference dataset for remote sensing of forest biomass. The Forest Observation System approach

Forest biomass is an essential indicator for monitoring the Earth’s ecosystems and climate. It is a critical input to greenhouse gas accounting, estimation of carbon losses and forest degradation, assessment of renewable energy potential, and for developing climate change mitigation policies such as REDD+, among others. Wall-to-wall mapping of aboveground biomass (AGB) is now possible with satellite remote sensing (RS). However, RS methods require extant, up-to-date, reliable, representative and comparable in situ data for calibration and validation. Here, we present the Forest Observation System (FOS) initiative, an international cooperation to establish and maintain a global in situ forest biomass database. AGB and canopy height estimates with their associated uncertainties are derived at a 0.25ha scale from field measurements made in permanent research plots across the world's forests. All plot estimates are geolocated and have a size that allows for direct comparison with many RS measurements. The FOS offers the potential to improve the accuracy of RS-based biomass products while developing new synergies between the RS and ground-based ecosystem research communities. Live, most up-to-date dataset is available at https://forest-observation-system.net

Plot Data from "Diversity and carbon storage across the tropical forest biome."

Tropical forests are global centres of both biodiversity and carbon storage. Many tropical countries aspire to protect forest to fulfil biodiversity and climate mitigation policy targets, but the conservation strategies needed to achieve these two functions depend critically on the tropical forest diversity-carbon relationship and this remains largely unexplored. Attempts to assess and understand this relationship in tropical forest ecosystems have been hindered by the scarcity of inventories where carbon storage in aboveground biomass and species identifications have been simultaneously and robustly quantified. Here, we compile a unique pan-tropical dataset of 360 plots located in old-growth closed-canopy forest, surveyed using standardised methods, allowing a multi-scale evaluation of the relationship between carbon storage and tree diversity. We find strongly contrasting variation in diversity and carbon among continents. Thus, on average, African forests have high carbon storage but relatively low diversity, Amazonian forests have high diversity but less carbon, and Southeast Asian forests have both high diversity and high carbon storage. Carbon-diversity relationships among all plots across the tropics are absent, and within continents are either weak (Asia) or absent (Amazonia, Africa). Within 1 ha plots a weak positive relationship is detectable, indicating that diversity effects in tropical forests may be scale dependent. The absence of clear diversity-carbon relationships at scales relevant to most conservation planning means that carbon-centred conservation strategies alone would miss many high diversity ecosystems. As tropical forests can have any combination of tree diversity and carbon stocks both will require explicit consideration when optimising policies to manage tropical carbon and biodiversity