Aim Insects are the most species‐rich clade in the world, but the broad‐scale diversity pattern and the potential drivers have not been well documented for the clade as a whole. We aimed to examine the relative roles of contemporary and historical climate, niche conservatism, range overlapping, and other environmental factors on geographic patterns of species richness and phylogenetic structure, for insects across China. Location China. Methods We collected insect data from 184 nature reserves and examined geographic patterns of species richness and mean root distance (MRD, a metric of the evolutionary development of assemblages) for different biogeographic affinities (Palearctic, Oriental, and widespread species) and for clades originated during the warm and cold geohistorical periods (“warm clades” and “cold clades,” respectively). We related richness and MRD to contemporary and historical climate, area, habitat heterogeneity, and human disturbance to evaluate their relative importance. Results Total species richness revealed a hump‐shaped latitudinal pattern, peaking between 30°~35°N. Richness patterns differed markedly among evolutionary groups: Oriental species richness decreased significantly with higher latitude but Palearctic species increased, while other groups again peaked between 30°~35°N. The range overlapping of different biogeographic groups in midlatitudes may be an important contributor to humped latitudinal richness patterns. MRD was positively related to latitude and increased more rapidly for “warm clades” than “cold clades.” Historical climate factors (especially winter coldness) were among the strongest predictors for both richness and phylogenetic patterns, for each evolutionary group, suggesting the strong influence of niche conservatism. Conclusions The hump‐shaped latitudinal pattern of insect richness in China is mainly shaped by niche conservatism and range overlapping, supplemented by habitat heterogeneity and contemporary climate. The role of niche conservatism and range overlapping may have been overlooked if only total species richness was analyzed, suggesting the importance of examining different evolutionary groups separately.

Fine roots have been hypothesized to be ‘leaves underground' in terms of vascular network, but this hypothesis has rarely been tested within the framework of metabolic scaling theory (MST). We measured average fine‐root (diameter < 1 mm) mass (M), surface area (A), volume (V), diameter (D) and length (L) for 216 soil cores from 24 plots across four successional stages in tropical forests of Xishuangbanna (southwest China), and examined eight scaling relationships between these variables at the individual root scale. We tested whether fine‐root allometries conformed to MST's model for leaf (MSTl) or model (MSTw) for woody organs (e.g. trunk). We also assessed the relative effects of environmental factors, tree size, species composition and diversity, and stand structural factors on allometric relationships using structural equation models (SEMs). Our results showed that: 1) fine‐root scaling exponents rarely conformed to MSTl's predictions. 2) The scaling exponents between fine‐root M, A, V and D all conformed to MSTw's predictions in later successional forests, but showed greater deviation towards early successional stage. 3) The scaling exponents associated with fine‐root length differed markedly from MSTw's predictions. 4) Changes of some fine‐root scaling exponents across successional stage were mainly affected by tree size or soil fertility, and species composition affected allometry only indirectly via tree size. Our results suggested that the allometries of individual fine roots largely conform to the scaling rules governing woody organs instead of leaves, probably because leaves are nearly two‐dimensional objects while the other two are three‐dimensional. We showed that MSTw can well predict some fine‐root allometries in later successional forests, suggesting great potential of utilizing MSTw to better estimate fine‐root biomass and productivity. However, the present MSTw still needs to be improved for predicting the scaling relationships concerning fine‐root length, and also for better quantifying allometric exponents in earlier successional forests.

Aims Biodiversity is found to have a significant promotion effect on ecosystem functions in manipulation experiments on grassland communities. However, its relative role compared with stand factors or functional identity is still controversial in natural forests. Here we examined their relative effects on biomass and productivity during forest restoration. Methods We investigated stand biomass and productivity for 24 plots (600 m 2) across restoration stages in the subtropical forests of Mt. Shennongjia, central China. We measured five key functional traits and calculated functional diversity (functional richness, evenness, and dispersion) and community-weighted mean (CWM) of traits. We used general linear models (GLMs), variation partitioning methods to test the relative importance of stand factors (density, stand age, maximum height, etc.), functional identity, species and functional diversity on biomass and productivity. Important Findings Our results illustrated that stand biomass and productivity increased significantly as forest restoration, and that community species richness increased significantly, while functional dispersion decreased significantly. Variation partitioning analyses showed that diversity had no significant pure effects on biomass and productivity. However, diversity can affect biomass and productivity through the joint effect with stand factors and functional identity. Overall, we found that stand factors had the strongest effect on biomass and productivity, while functional identity significantly affects productivity but not biomass, suggesting that modulating stand structure and species identity are effective ways to enhance forest carbon storage and sequestrations potential in forest management.

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