The soils of the Qinghai-Tibetan Plateau store a large amount of organic carbon, but the magnitude, spatial patterns and environmental controls of the storage are little investigated. In this study, using data of soil organic carbon (SOC) in 405 profiles collected from 135 sites across the plateau and a satellite-based dataset of enhanced vegetation index (EVI) during 2001-2004, we estimated storage and spatial patterns of SOC in the alpine grasslands. We also explored the relationships between SOC density (soil carbon storage per area) and climatic variables and soil texture. Our results indicated that SOC storage in the top 1 m in the alpine grasslands was estimated at 7.4 Pg C (1 Pg 5 10 15 g), with an average density of 6.5 kg m À2 . The density of SOC decreased from the southeastern to the northwestern areas, corresponding to the precipitation gradient. The SOC density increased significantly with soil moisture, clay and silt content, but weakly with mean annual temperature. These variables could together explain about 72% of total variation in SOC density, of which 54% was attributed to soil moisture, suggesting a key role of soil moisture in shaping spatial patterns of SOC density in the alpine grasslands.

China, one of the world's “megabiodiversity countries”, is home to more than 30 000 vascular plant and 6300 vertebrate species. Over thousands of years, however, cultivation has led to the disappearance of many of these species from the plains and lowland areas. The mountain regions still harbor large numbers of species, because there have been fewer human and natural disturbances and there are more diverse habitats. We used county level species distribution databases to explore patterns of biodiversity and to identify biodiversity hotspots within China. Ten hotspot ecoregions were identified, containing 3110 plant genera (92.0% of the country's total), 220 (90.5%) endemic plant genera, 366 (94.3%) endangered plants, and 254 (72.2%) endangered vertebrates, 427 (91.0%) terrestrial mammal species, and 65 (85.5%) endemic mammals. All 10 hotspot ecoregions are located in the mountainous areas of China. Although high richness of overall, endangered, and endemic plants and animals co‐occurred in many of the same hotspot ecoregions, they often occurred in different counties within these ecoregions and showed low spatial congruence. In conclusion, China's mountain regions are critical for protecting biodiversity and should be made conservation priorities in the future.

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Summary• Leaf mass per area (LMA), nitrogen concentration (on mass and area bases, N mass and N area , respectively), photosynthetic capacity ( A mass and A area ) and photosynthetic nitrogen use efficiency (PNUE) are key foliar traits, but few data are available from cold, high-altitude environments.• Here, we systematically measured these leaf traits in 74 species at 49 research sites on the Tibetan Plateau to examine how these traits, measured near the extremes of plant tolerance, compare with global patterns.• Overall, Tibetan species had higher leaf nitrogen concentrations and photosynthetic capacities compared with a global dataset, but they had a slightly lower A mass at a given N mass . These leaf trait relationships were consistent with those reported from the global dataset, with slopes of the standardized major axes A mass -LMA, N mass -LMA and A mass -N mass identical to those from the global dataset. Climate only weakly modulated leaf traits.• Our data indicate that covarying sets of leaf traits are consistent across environments and biogeographic regions. Our results demonstrate functional convergence of leaf trait relationships in an extreme environment.

Diversity‐manipulation experiments suggest a positive effect of biodiversity on ecosystem properties (EPs), but variable relationships between species richness and EPs have been reported in natural communities. An explanation for this discrepancy is that observed richness–EPs relationships in natural communities change with environment and species functional identities. But how the relationships change along broad‐scale climatic gradients has rarely been examined. In this paper, we sampled 848 plots of 20 × 30 m2 from boreal to tropical forests across China. We examined plot biomass with respect to environmental factors, tree species richness and functional group identity (FGI, i.e. evergreen vs deciduous, and coniferous vs broadleaf). Variation partitioning was used to evaluate the relative effects of the three classes of factors. We found that, most of the ‘effects’ (percentage of variation explained) of richness and FGI on forest biomass were shared with environmental factors, but species richness and FGI still revealed significant effects in addition to environment for plots across China. Richness and FGI explained biomass mainly through their shared effects instead of independent effects, suggesting that the positive biodiversity effect is closely associated with a sampling effect. The relative effects of richness, FGI and environment varied latitudinally: the independent effects of environment and richness decreased from boreal to subtropical forests, whereas the total effect of FGI increased. We also found that the slope of richness–biomass relationship decreased monotonically from boreal to subtropical forests, possibly because of decreasing complementarity and increasing competition with increasing productivity. Our results suggest that while species richness does have significant effects on forest biomass it is less important than environmental gradients and other biotic factors in shaping large‐scale biomass patterns. We suggest that understanding how and why the diversity–EPs relationships change along climatic gradient would be helpful for a better understanding of real biodiversity effects in natural communities.