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We examine the potential of trait-based parameters of taxa for linking above-ground and belowground ecological networks (hereafter ‘green’ and ‘brown’ worlds) to understand and predict community dynamics. This synthesis considers carbon, nitrogen and phosphorus-related traits, the abundance of component species and their size-distribution across trophic levels under different forms of management. We have analyzed existing and novel databases on plants, microbes and invertebrates that combine physico-chemical and biological information from (agro)ecosystems spanning the globe. We found (1) evidence that traits from above-ground and below-ground systems may be integrated in the same model and (2) a much greater than expected stoichiometric plasticity of plants and microbes which has implications for the entire food-web mass-abundance scaling. Nitrogen and phosphorus are primary basal resources (hence, drivers) and more retranslocation of P than of N from leaves will lead to higher N:P in the litter and soil organic matter. Thus, under nutrient-rich conditions, higher foliar concentrations of N and P are reflected by lower N:P in the brown litter, suggesting less P retranslocated than N. This apparent stoichiometric dichotomy between green and brown could result in shifts in threshold elemental ratios critical for ecosystem functioning. It has important implications for a general food-web model, given that resource C:N:P ratios are generally assumed to reflect environmental C:N:P ratios. We also provide the first evidence for large-scale allometric changes according to the stoichiometry of agroecosystems. Finally, we discuss insights that can be gained from integrating carbon and nitrogen isotope data into trait-based approaches, and address the origin of changes in Δ13C and Δ15N fractionation values in relation to consumer-resource body-mass ratios

The high numbers of primary producers represent multiple sources of organic matter accumulating onto lake bottoms. The difficulty of distinguishing the relative contribution to the mixture presents considerable challenges to the analysis of these organic deposits. In this study, dual-stable isotope analysis and IsoSource model were used to identify allochthonous and autochthonous components of detritus deposits (Particulate Organic Matter: POM) at two different bottom slope sites of a volcanic lake (lake Bracciano). Experiments were carried out to calibrate IsoSource on constructed plant mixtures and assess changes in isotope ratios during plant decomposition. IsoSource satisfactorily discriminated the constructed mixture sources with a few exceptions. Changes in isotopic enrichment during decomposition were low, and thus did not represent a confounding variable in the isotopic analysis. By contrast, chemical and geological differences of the study sites were associated with differences in plant δ13C and δ15N values (more than 2‰ within single plant species). At both sites, the isotopic signals of POM fell between polygons delineated by source end members with an evident shift of δ13C toward allochthonous sources. POM amount and diversity were greater at the flatter bottom site, where allochthonous contributions were larger than at the other site. In particular, IsoSource ranked species contributions as follows: A. glutinosa > P. australis > A. donax > S. alba > P. nigra > the benthic macroalga Chara sp. at the first site, and A. glutinosa > P. nigra > the aquatic macrophyte C. demersum at the latter. The composition of littoral POM was determined by allochthonous sources in proportion to their relative abundances (as percent land cover) with differences between sites due to bottom slope.

Lake Titicaca is the largest freshwater lake in South America and one of the highest and oldest of the world's large lakes, but very little of its ecology is known. We report results from a study on the spatial variation of decomposition rate of Schoenoplectus tatora in Inner Puno Bay affected by direct wastewater discharges. The aims of the research were: (1) to evaluate the effect of benthos exclusion and the influence of other environmental factors on decomposition and (2) to map the decomposition rate in order to describe the spatial heterogeneity in the water body. We carried out the study at 21 sampling points using both fine-meshed and coarse-meshed litterbags to exclude and to allow detritivore action, respectively. Decomposition was on the average faster in the former than in the latter treatment. However, the difference decreased with increasing detritivore abundance, and reversed in the most densely populated waters of the bay. Coupled spatial dependence of the decomposition rate and temperature was observed. Both variables were related with the distance from the wastewater discharges, suggesting that thermal pollution constrains the decomposition rate within the inner bay. Detritivores did not change the general trend imposed by temperature, but their presence increased the spatial heterogeneity of the process