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Aim: Significant changes in species elevational ranges in mountains have been repeatedly documented, yet the direction, magnitude and drivers of these shifts remain controversial. Presently, there is still lacking evidence about the general nature of species elevational range shifts in eastern Eurasia in response to anthropogenic climate change. By using historical specimen records and recent field observations for 735 seed plant species across 29 China's mountains, we assessed changes in species' elevational centroids and their drivers. Location: China. Time Period: 1950–2018. Major Taxa Studied: Seed plant species. Methods: The elevation records of all sampled occurrences in each mountain during the two time periods were estimated, and the null models were developed to test the sampling bias. Ecological niche models (ENMs) were used to evaluate the relative importance of climate factors in constraining each species distribution. Generalized linear models (GLMs) to test the relationships between the centroid elevational range shifts of species and different divers. Results: We found that 54% of the species shifting upward and 46% downhill. However, species' elevational shifts significantly differed among species and mountains. Herbaceous and lowland species moved upward faster than woody and high‐elevation species. Species in temperate mountains and in mountains with taller elevational gradients moved upward, while species in subtropical mountains and in mountains with shorter elevational gradients moved downward. Precipitation changes experienced by species, species' climatic adaptations, several species' functional traits and mountain size all contributed to explain the magnitude of species' centroid elevational range shifts. Main Conclusions: Our results highlight complex biodiversity redistribution of seed plants across Chinese mountains, not necessarily conforming to the trend of species upward shifts in elevation. Changes in precipitation regimes may blur the simplistic assumption of isotherm tracking. This study fills an important geographic shortfall for our understanding of biodiversity redistribution under anthropogenic climate change. [ABSTRACT FROM AUTHOR]

Aim: Soil organic carbon (SOC) stabilization has become an important topic in recent years in the context of global climate change. Microbial residues represent a significant component of stabilized SOC pools. However, spatial variations in the contributions of bacterial and fungal residues to SOC and their determinants at a continental scale remain poorly understood. We aimed to evaluate the spatial variations and controls of the contributions of microbial residues to SOC in forest topsoil. Location: North–south transect in eastern China. Time period: 2014. Major taxa studied: Forest ecosystems. Methods: A total of 195 surface (0–10 cm) soils were sampled from 28 forest sites across tropical and boreal forests in eastern China from July to August to assess how biotic and abiotic factors govern the geographic patterns of the contributions of soil microbial residues (indicated by amino sugars) to SOC. Results: Fungal residues (30.0%) had a greater average contribution to SOC than bacterial residues (15.5%). The contributions of bacterial (CBR) and total microbial residues (CMR) to SOC showed negative latitudinal patterns and were positively correlated with mean annual temperature (MAT). In contrast, the contribution of fungal residues to SOC (CFR) showed no clear geographic or climatic patterns. On average, the CBR (9.7%), CFR (21.1%) and CMR (30.8%) were lower in boreal forests than in other biome forests. SOC concentration negatively mediated CBR, CFR and CMR. The piecewise structural equation model results showed that MAT was the primary driver of the geographic pattern of CBR, whereas SOC and soil carbon : nitrogen ratio were more directly associated with the CFR. Additionally, plant factors and microbial properties (i.e., microbial biomass and composition) played relatively little roles in regulating CBR, CFR and CMR. Main conclusions These findings advance the current knowledge of the different geographic patterns of CBR and CFR regulated by different potential mechanisms in forest ecosystems. This highlights that the dynamics of microbial residues could potentially have unexpected consequences for topsoil SOC stocks under climate change. [ABSTRACT FROM AUTHOR]

Aim: Mangrove forests are important coastal wetlands for the blue carbon budget and play a significant role in mitigating global climate change. However, spatial patterns of carbon stocks in mangrove forests on an island scale have not been quantified owing to methodological limitations and lack of understanding of controlling factors. We took the entire Hainan Island as a case study and aimed to carry out a comprehensive investigation of the spatial patterns and driving factors of carbon stocks in mangrove forests. Location: Southern China. Time period: 2017–2020. Major taxa studied: Mangrove forest. Methods: The upscaling method combined with field surveys and Sentinel‐2 imagery analysis were used to compare different models for optimization of mangrove ecosystem carbon stock estimations. We also used structural equation modelling (SEM) to evaluate the factors driving the distributional patterns of mangrove carbon stocks on an island scale. Results: The current total mangrove carbon stock of the entire Hainan Island was estimated to be 703,181 Mg C (with a mean density of 192 Mg C/ha), with the above‐ and below‐ground carbon stocks averaging at 44.7 and 147.3 Mg C/ha, respectively. The mangrove carbon storage in the north‐eastern region of the island was the highest and in the west region the lowest. Sediment nitrogen content and plant species diversity had the most positive driving effects on the distribution of total carbon stock for Hainan Island mangroves. Main conclusions: The combination of field surveys and Sentinel‐2 imagery analysis can be applied to regional‐scale estimations of carbon stocks for mangrove forests. Spatial pattens of mangrove carbon stocks vary among locations on Hainan Island, and soil nutrient (especially nitrogen) availability is the dominant factor regulating carbon stock variations along the land‐to‐sea gradient. Our findings have significant implications for better understanding the distribution of mangrove carbon stocks and quantification of the global blue carbon budget. [ABSTRACT FROM AUTHOR]

Aim: Marine biodiversity is increasingly threatened by overfishing and climate change, but it is still unclear how these drivers have shaped the functional diversity (FD) of marine fish. Here, we explore how the FD of commercial marine fish communities responds to climate change and fishing pressure. Major taxa studied: Marine fish. Location: China Seas. Time period: 1989–2018. Methods: We used a catch database of four individual species and 12 species groups that were reported continuously in China from 1989 to 2018. Seven traits were selected to calculate FD. We adopted generalized linear mixed models to analyse the complex relationship among climate change, fishing pressure and several metrics of marine fish FD. We identified the percentage change in diversity for communities to assess the relative contribution of each species or species group by removing individual species or a species group from the dataset. Results: Climate change and fishing pressure exerted statistically significant opposing effects on the functional evenness (FEve) and functional divergence (FDiv) of commercial fish communities. Increasing sea surface temperature had a significant positive effect on FEve but a negative effect on FDiv. In contrast, increasing fishing pressure had the opposite effects on FEve and FDiv. These results were driven by the significantly varying relative contributions of fish species or species groups to the functional space, whereby low‐trophic‐level pelagic fish species or species groups are closer to the boundaries of the functional trait space than high‐trophic‐level demersal fish species or species groups. Main conclusions: The FD of commercial marine fish communities responds significantly to climate warming and increasing fishing pressure, with opposite effects driven by different response patterns of fish species or species groups. Our results suggest that management actions should address the two issues simultaneously, because considering only one will unleash greater functional changes in the other. [ABSTRACT FROM AUTHOR]

ABSTRACT Aim Our aim was to address the potential effect of the geographical range size of species on the relationships between plant traits, soil and climate in Chinese grasslands. Previous analyses tended to examine plant-environment relationships across many species while ignoring that species with different range sizes may respond differently to the environment. Here we hypothesized that leaf traits of narrow-ranging species would be more strongly correlated with soil and climatic variables than those of wide-ranging species. Location Chinese grasslands. Methods Data on leaf traits, including nitrogen and phosphorus concentrations, carbon/nitrogen ratio, nitrogen/phosphorus ratio and specific leaf area, as well as species range sizes for 208 species distributed across 178 sites in Chinese grasslands were collected. Soil and climate information for each study site was also gathered. The effects of range size on leaf traits were tested using one-way ANOVA. Correlations between leaf traits, soil and climate were calculated for all species pooled together and for species partitioned into range size quartiles, from the first (narrowest- ranging 25%) to the fourth (widest-ranging 25%). Results Narrow-ranging species tended to occur at high altitude with lower temperature but higher soil nutrient concentrations compared with wide-ranging species. No direct link between leaf traits and species range sizes was detected. However, patterns of leaf-soil nutrient relationships changed significantly across levels of range size. Narrow-ranging species tended to be more sensitive to variation in soil nutrient availability than wide-ranging species, resulting in a shift from a positive leaf-soil nutrient relationship for narrow-ranging plants to no relationship for wide-ranging plants. Species responses to climatic variables were unrelated to their range sizes. Main conclusions The close relationship between leaf and soil nutrients indicates a specialization of narrow-ranging species to particular habitats whereas wide-ranging species may be able to better withstand changes in environment such as soil fertility over a large area. [ABSTRACT FROM AUTHOR]

We investigated how ozone pollution and climate change/variability have interactively affected net primary productivity (NPP) and net carbon exchange (NCE) across China's forest ecosystem in the past half century. Continental China. Using the dynamic land ecosystem model (DLEM) in conjunction with 10-km-resolution gridded historical data sets (tropospheric O concentrations, climate variability/change, and other environmental factors such as land-cover/land-use change (LCLUC), increasing CO and nitrogen deposition), we conducted nine simulation experiments to: (1) investigate the temporo-spatial patterns of NPP and NCE in China's forest ecosystems from 1961-2005; and (2) quantify the effects of tropospheric O pollution alone or in combination with climate variability and other environmental stresses on forests' NPP and NCE. China's forests acted as a carbon sink during 1961-2005 as a result of the combined effects of O, climate, CO, nitrogen deposition and LCLUC. However, simulated results indicated that elevated O caused a 7.7% decrease in national carbon storage, with O-induced reductions in NCE (Pg C year) ranging from 0.4-43.1% among different forest types. Sensitivity experiments showed that climate change was the dominant factor in controlling changes in temporo-spatial patterns of annual NPP. The combined negative effects of O pollution and climate change on NPP and NCE could be largely offset by the positive fertilization effects of nitrogen deposition and CO. In the future, tropospheric O should be taken into account in order to fully understand the variations of carbon sequestration capacity of forests and assess the vulnerability of forest ecosystems to climate change and air pollution. Reducing air pollution in China is likely to increase the resilience of forests to climate change. This paper offers the first estimate of how prevention of air pollution can help to increase forest productivity and carbon sequestration in China's forested ecosystems. [ABSTRACT FROM AUTHOR]

Aim: Previous studies have found strikingly different geographical patterns of phylogenetic diversity of gymnosperms and angiosperms, which have been suggested to result, in part, from the greater age of the former. To assess the effects of clade age on phylogenetic structure, we assessed phylodiversity patterns of pteridophytes (lycophytes and ferns), which combine ancient and modern lineages, across China. Location: China. Time period: Present day. Taxon: Pteridophytes. Methods: We divided China into 66 regions and collated species lists of pteridophytes for each region. We then related taxonomic and phylogenetic diversity, and their related metrics, to six climatic variables for pteridophytes as a whole and for different evolutionary clades. We examined the effect of spatial autocorrelation among regional floras on the results. Results: We found that when all pteridophytes or ferns were considered, the patterns resembled those of gymnosperms, presumably reflecting the effects of several ancient global mass extinctions and the relict distribution of old families. In contrast, when we considered only the modern Polypodiales radiation, which accounts for three‐quarters of current fern diversity and is about as old as the angiosperm radiation, we found a pattern similar to that of angiosperms. This pattern is consistent with the tropical niche conservatism hypothesis and suggests that both major groups of land plants have a broadly similar evolutionary trajectory, with most families originating in tropical conditions and few families adapting to cold and arid conditions. Main conclusions: Our study shows that the phylogenetic structures of more recently evolved and diversified clades of pteridophytes are fairly consistent with the tropical niche conservatism hypothesis, suggesting that the age of the taxon, its physiological adaptations and the global climatic changes that it experienced during its evolutionary history are reflected in the composition of current plant assemblages. [ABSTRACT FROM AUTHOR]

Aim The long-term cyclical patterns of China's geopolitical shifts are of great interest to scholars and the public, but to date there has been no satisfactory explanation for the alternating occupancy patterns of the country's pastoral and agrarian polities. We fill this gap by differentiating the agroecological settings of these polities over time and quantitatively analysing the relationships between climate change and historical geopolitical variations. Location China. Methods Our dataset comprised 38 palaeohydroclimate reconstructions, the historical boundaries of China's empire and the changes in its size, and 1028 wars and 2737 battle locations over the past 2300 years. China-wide precipitation during the period was reconstructed using the 'weighted composite plus scale' method. Time-series analyses were performed to identify the strength of the associations between climate change and the geopolitical variables. Granger causality analysis and wavelet analysis were performed to verify the hypothesized causal links. Wavelet analysis was also used to identify the possible interactions (i.e. frequencies, significance, consistency and synchrony) between the signal components of the climatic and geopolitical variables at different temporal scales. Results China's mean precipitation fell into three multicentennial cycles. The geopolitical variables corresponded to those cycles in the imperial era. The spatial-temporal frequencies of the boundaries and size of the agriculturalist empires and its frontiers with pastoralist empires were regulated by the long-term (low-frequency) precipitation fluctuations at the multicentennial scale. Wars of aggression were an important explanatory factor driving the land-occupancy patterns of the two ecoempires under climate change, and caused most of the territorial shifts. Short-term (high-frequency) geopolitical changes were not associated with climate change. Main conclusions Precipitation-induced ecological change was an important factor governing the macrogeopolitical cycles in imperial China. Long-term territorial expansion favoured the polity (agriculturalist or pastoralist) that was better adapted to the changing ecological conditions in the country's heartland. [ABSTRACT FROM AUTHOR]

Aim Plant roots are crucial for water and nutrient absorption, but large-scale patterns and underlying mechanisms of root trait variation and evolution are poorly understood. Here we quantify the degree of variation in functional traits for the first-order roots across large geographical scales and examine the potential mechanisms underlying these patterns. Location China. Methods We collected first-order roots (stream-based ordering system) and leaf samples of 65 tree species in six forests from subtropical to temperate zones and determined the key morphological, architectural and chemical traits. Results We found wider variation in root morphology in the subtropical zone, where species with very thick and very thin first-order roots coexisted, in contrast with narrower variation among species in the temperate zone. Inconsistent with the predictions of trait economics spectrum, root nitrogen concentration was uncorrelated with root morphology. Furthermore, average root diameter at the plant family level decreased markedly with their divergence time in both piecewise and phylogenetic independent contrast regression analyses. Main conclusions Higher variation in root morphology in the subtropical zone appears to result from the coexistence of tree species with thick and thin roots, probably because of a more favourable water supply. Patterns of root evolution towards thinner roots were driven by both phylogeny and possible adaptation of newly diverged species to drier habitats from mid to late Cretaceous. Our findings reveal contrasting selection pressures at the root and leaf level in different climatic zones during plant evolution, and suggest that a single vector of variation linking morphology to resource acquisition or life span ('trait economics') remains elusive in roots. [ABSTRACT FROM AUTHOR]

1 We model the potential vegetation and annual net primary production (NPP) of China on a 10′ grid under the present climate using the processed-based equilibrium terrestrial biosphere model BIOME3. The simulated distribution of the vegetation was in general in good agreement with the potential natural vegetation based on a numerical comparison between the two maps using the ΔV statistic (ΔV = 0.23). Predicted and measured NPP were also similar, especially in terms of biome-averages. 2 A coupled ocean-atmosphere general circulation model including sulphate aerosols was used to drive a double greenhouse gas scenario for 2070-2099. Simulated vegetation maps from two different CO[sub 2] scenarios (340 and 500 p.p.m.v.) were compared to the baseline biome map using ΔV. Climate change alone produced a large reduction in desert, alpine tundra and ice/polar desert, and a general pole-ward shift of the boreal, temperate deciduous, warm-temperate evergreen and tropical forest belts, a decline in boreal deciduous forest and the appearance of tropical deciduous forest. The inclusion of CO[sub 2] physiological effects led to a marked decrease in moist savannas and desert, a general decrease for grasslands and steppe, and disappearance of xeric woodland/scrub. Temperate deciduous broadleaved forest, however, shifted north to occupy nearly half the area of previously temperate mixed forest. 3 The impact of climate change and increasing CO[sub 2] is not only on biogeography, but also on potential NPP. The NPP values for most of the biomes in the scenarios with CO[sub 2] set at 340 p.p.m.v. and 500 p.p.m.v. are greater than those under the current climate, except for the temperate deciduous forest, temperate evergreen broadleaved forest, tropical rain forest, tropical seasonal forest, and xeric woodland/scrub biomes. Total vegetation and total carbon is simulated to increase significantly in the future climate scenario, both with and without the CO[sub... [ABSTRACT FROM AUTHOR]