The biodiversity-productivity relationship (BPR) is foundational to our understanding of the global extinction crisis and its impacts on ecosystem functioning. Understanding BPR is critical for the accurate valuation and effective conservation of biodiversity. Using ground-sourced data from 777,126 permanent plots, spanning 44 countries and most terrestrial biomes, we reveal a globally consistent positive concave-down BPR, showing that continued biodiversity loss would result in an accelerating decline in forest productivity worldwide. The value of biodiversity in maintaining commercial forest productivity alone—US$166 billion to 490 billion per year according to our estimation—is more than twice what it would cost to implement effective global conservation. This highlights the need for a worldwide reassessment of biodiversity values, forest management strategies, and conservation priorities. (Résumé d'auteur

The importance of biodiversity in supporting ecosystem functioning is generally well accepted. However, most evidence comes from small-scale studies, and scaling-up patterns of biodiversity-ecosystem functioning (B-EF) remains challenging, in part because the importance of environmental factors in shaping B-EF relations is poorly understood. Using a forest research platform in which 26 ecosystem functions were measured along gradients of tree species richness in six regions across Europe, we investigated the extent and the potential drivers of context dependency of B-EF relations. Despite considerable variation in species richness effects across the continent, we found a tendency for stronger B-EF relations in drier climates as well as in areas with longer growing seasons and more functionally diverse tree species. The importance of water availability in driving context dependency suggests that as water limitation increases under climate change, biodiversity may become even more important to support high levels of functioning in European forests.

Climate models predict an increase in the intensity and frequency of drought episodes in the Northern Hemisphere. Among terrestrial ecosystems, forests will be profoundly impacted by drier climatic conditions, with drastic consequences for the functions and services they supply. Simultaneously, biodiversity is known to support a wide range of forest ecosystem functions and services. However, whether biodiversity also improves the resistance of these ecosystems to drought remains unclear. We compared soil drought exposure levels in a total of 160 forest stands within five major forest types across Europe along a gradient of tree species diversity. We assessed soil drought exposure in each forest stand by calculating the stand-level increase in carbon isotope composition of late wood from a wet to a dry year (Δδ 13 C S ). Δδ 13 C S exhibited a negative linear relationship with tree species diversity in two forest types, suggesting that species interactions in these forests diminished the drought exposure of the ecosystem. However, the other three forest types were unaffected by tree species diversity. We conclude that higher diversity enhances resistance to drought events only in drought-prone environments. Managing forest ecosystems for high tree species diversity does not necessarily assure improved adaptability to the more severe and frequent drought events predicted for the future.climate change | ecology | species interaction | carbon isotope composition | FundivEUROPE

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Associations between catchment characteristics (altitude, slope, proportion of peatland, site fertility, total stem volume, and its distribution among the main tree species), climatic drivers (temperature sum, latitude, precipitation and runoff) and atmospheric deposition and concentrations and export of C, N, P and Fe in 21 unmanaged boreal catchments (0.07 to 14 km 2 ) were examined in data sets spanning 3 to 32 years. In the entire data base including catchments from southernmost Finland to the Arctic Circle, N and P concentrations were associated with climatic drivers and deposition, while a catchment characteristic, peatland percentage, refl ecting topography and site fertility was the best predictor for TOC (total organic carbon) and total Fe concentrations and export. In a subgroup of 18 catchments located in similar climatic conditions and low N deposition in eastern Finland (<600 kg N km -2 yr -1 ), peatland percentage accounted for 52-75 % of the export of TOC, TN (total nitrogen), TON (total organic nitrogen), NH 4 -N and total Fe, while slope was the best predictor of TP (total phosphorus) export (r 2 = 0.56, p < 0.001). Furthermore, among these 18 catchments TOC export accounted for as much as 95 % of the variance in TON export, and 61-73 % of the variance in NH 4 -N, total Fe and TP export. Total stem volume of the tree stands and their distribution between tree species and vegetation types were not important predictors for concentrations/export. The peatland percentage of the 21 catchments ranged widely, from 0 to 88 %, with an average value of 34 % as in entire Finland. Consequently, among the 21 catchments there was also a large variability both in average TOC and pH, 1.2-30 mg l -1 and 4.2-7.1, respectively. The average annual TOC export was 6,200 kg km -2 yr -1 , signifi cantly lower values were recorded for the export of TN, TP and total Fe (130, 5 and 280 kg km -2 yr -1 , respectively). N and P export was mainly in an organic form. The TIN (total inorganic N) proportion averaged 13 % and elevated NO 3 -N export occurred only in fertile, high pH sites in southernmost Finland, where stream C/N ratio was lowest. On average, 97 % of the TOC, 94 % of the TN and 79 % of the TP was in a dissolved form.