• Energy Research

Summary Consistent information on the current elemental composition of vegetation at global scale and the variables that determine it is lacking. To fill this gap, we gathered a total of 30 912 georeferenced records on woody plants foliar concentrations of nitrogen (N), phosphorus (P) and potassium (K) from published databases, and produced global maps of foliar N, P and K concentrations for woody plants using neural networks at a resolution of 1 km2. We used data for climate, atmospheric deposition, soil and morphoclimatic groups to train the neural networks. Foliar N, P and K do not follow clear global latitudinal patterns but are consistent with the hypothesis of soil substrate age. We additionally built generalized linear mixed models to investigate the evolutionary history effect together with the effects of environmental effects. In this comparison, evolutionary history effects explained most of the variability in all cases (mostly > 60%). These results emphasize the determinant role of evolutionary history in foliar elemental composition, which should be incorporated in upcoming dynamic global vegetation models.

This dataset presents data of the activities of soil enzymes involved in the mobilization of C, N and P in the soils of two different Mediterranean environments (Mediterranean xerophytic shrubland and Mediterranean holm-oak forest), subject to control conditions and warming, drought and N-deposition treatments in order to mimic some of the main drivers of Climate Change, for the years 2014 and 2015. Some files also contain soil physio-chemical parameters, soil extractable elements, microbial elements, microbial community composition, and plant ecophysiological parameters.

AbstractSoil enzymes are crucial in mediating ecosystems' responses to environmental drivers, so that the comprehension of their sensitivity to drivers of global change can help make predictions of future scenarios and design tailored interventions of biomanipulation. Drivers of global change usually act in combination of two or more, and indirect effects of one driver acting through modification of another one often occur, yet most of both manipulative and meta‐analysis studies available tend to focus on the direct effect of one single driver on the activity of specific soil enzymes. One of the biggest challenges is, therefore, represented by the difficulty in assessing the interactions between different drivers, due to the complexity of disentangling the single direct effects from the indirect and combined ones. In this review, after elucidating the general mechanisms of soil enzyme production and activity regulation, we display the state‐of‐the‐art knowledge on direct, indirect and combined effects of the main drivers of global change on soil enzyme activities, identify gaps in knowledge and challenges from research, plus we analyse how this can reverberate in the future of biomanipulation techniques for the improvement of ecosystem services. We conclude that qualitative but not quantitative outcomes can be predicted for some interactions such as warming + drought or warming + CO2, while for other ones, the results are controversial: future basic research will have to center on this holistic approach. A general trend toward the overall increase of soil enzyme activities and acceleration of biogeochemical cycles will persist, until an inflection will be caused by factors such as future shifts in microbial communities and changes in carbon use efficiency. Applied research will develop toward the refinement of “in situ” analytical systems for the study of soil enzyme activities and the support of bioengineering for the better tailoring of interventions of biomanipulation.

AbstractThe drivers of global change, including increases in atmospheric CO2concentrations, N and S deposition, and climate change, likely affect the nutritional status of forests. Here we show forest foliar concentrations of N, P, K, S and Mg decreased significantly in Europe by 5%, 11%, 8%, 6% and 7%, respectively during the last three decades. The decrease in nutritional status was especially large in Mediterranean and temperate forests. Increasing atmospheric CO2concentration was well correlated with the decreases in N, P, K, Mg, S concentrations and the increase of N:P ratio. Regional analyses indicated that increases in some foliar nutrient concentrations such as N, S and Ca in northern Europe occurred associated with increasingly favourable conditions of mean annual precipitation and temperature. Crucial changes in forest health, structure, functioning and services, including negative feedbacks on C capture can be expected if these trends are not reversed.

AbstractSoil enzymes are central in the response of terrestrial ecosystems to climate change, and their study can be crucial for the models’ implementation. We investigated for 1 year the effects of warming and seasonality on the potential activities of five soil extracellular enzymes and their relationships with soil moisture, phosphorus (P) concentration, and other soil parameters in a P‐limited Mediterranean semiarid shrubland. The site was continuously subjected to warming since 1999, and we compared data from this study to analogous data from 2004. Warming uniformly increased all enzymes activities, but only when a sufficient amount of soil water was available. Seasonality unevenly altered enzyme activities, thus affecting enzymatic stoichiometry. P deficiency affected enzymatic stoichiometry, favoring the activities of the phosphatases. The effect of warming was stronger in 2014 than 2004, excluding the hypothesis of acclimation of rhizospheric responses to higher temperatures and suggesting that further increases in extracellular enzymatic activities are to be expected if sufficient water is available. Climatic warming will likely generally stimulate soil enzymatic activities and accelerate nutrient mineralization and similar ecological processes such as the production and degradation of biomass and changes in community composition, but which will be limited by water availability, especially in Mediterranean soils in summer. Winters in such ecosystems will benefit from a general increase in activity and production, but biological activity could even decrease in summer, potentially leading to a negative overall balance of nutrient mineralization. This study suggests that a general increase in activity due to warming could lead to faster mineralization of soil organic matter and water consumption in colder climates, until one of these factors in turn becomes limiting. Such trade‐offs between water and temperature in relation with enzyme activity should be considered in biogeochemical models.