AIM: Variation in species composition among sites (β‐diversity) generally decreases with increasing latitude, but the underlying mechanisms are ambiguous. Although both local and large‐scale ...processes may drive this pattern, they act all through influencing species abundance distribution (SAD) and spatial pattern of species. A null model incorporating SAD is often used to calculate expected β‐diversity, which accounts for most variation in β‐diversity. However, a recent study has shown that the deviation of observed β‐diversity from expected values (β‐deviation) increases with latitude. The latitudinal gradients in β‐deviation may be related to both latitudinal differences in SADs and the degrees of spatial aggregation. Our study aims to (1) investigate how β‐deviation varies with SAD and spatial aggregation, and (2) separate the contributions of SAD and aggregation in explaining latitudinal gradients in β‐deviation. LOCATION: Global. METHODS: 197 forest plots (each containing 10 subplots) distributed along latitudinal gradients were used. Two β‐diversity models were derived for communities with randomly and nonrandomly distributed species. The two models were used to simulate relationships of β‐deviation with SAD and aggregation, and to separate the contributions of these two factors in explaining latitudinal gradients in β‐deviation. RESULTS: β‐deviation increased with the degree of aggregation and peaked at intermediate species abundance. The fraction of β‐deviation linked to SAD increased with latitude in global and regional analyses, whereas the fraction of β‐deviation linked to aggregation was only significantly correlated with latitude in New World south. The degree of aggregation increased with latitude in New World south, but not in global extent and New World north. MAIN CONCLUSIONS: The latitudinal gradients in β‐deviation are primarily explained by latitudinal differences in SADs. Additionally, the expected β‐diversity is determined solely by SAD. Therefore, we conclude that latitude‐β‐diversity gradients at local spatial scales appear to be explained by latitudinal differences in SADs.
Plot‐scale experiments indicate that functional diversity (FD) plays a pivotal role in sustaining ecosystem functions such as net primary productivity (NPP). However, the relationships between ...functional diversity and NPP across larger scale under varying climatic conditions are sparsely studied, despite its significance for understanding forest–atmosphere interactions and informing policy development. Hence, we examine the relationships of community‐weighted mean (CWM) and functional dispersion (FDis) of woody plant traits on NPP across China and if such relationships are modulated by climatic conditions at the national scale. Using comprehensive datasets of distribution, functional traits, and productivity for 9120 Chinese woody plant species, we evaluated the distribution pattern of community‐weighted mean and functional dispersion (including three orthogonal trait indicators: plant size, leaf morphology, and flower duration) and its relationships with NPP. Finally, we tested the effects of climatic conditions on community‐weighted mean/functional dispersion–NPP relationships. We first found overall functional diversity–NPP relationships, but also that the magnitude of these relationships was sensitive to climate, with plant size community‐weighted mean promoting NPP in warm regions and plant size functional dispersion promoting NPP in wet regions. Second, warm and wet conditions indirectly increased NPP by its positive effects on community‐weighted mean or functional dispersion, particularly through mean plant size and leaf morphology. Our study provides comprehensive evidence for the relationships between functional diversity and NPP under varying climates at a large scale. Importantly, our results indicate a broadening significance of multidimensional plant functional traits for woody vegetation NPP in response to rising temperatures and wetter climates. Restoration, reforestation actions and natural capital accounting need to carefully consider not only community‐weighted mean and functional dispersion but also their interactions with climate, to predict how functional diversity may promote ecosystem functioning under future climatic conditions.
The relationship between plant functional diversity and productivity is climatic sensitive. Our results emphasize the importance of considering the interaction between climate and functional diversity in restoration and reforestation actions.
Documenting the patterns and drivers of functional trait distributions at large spatial scales is key to our fundamental understanding of the composition of plant assemblages. However, ...phylogeographic patterns of fruit development time (FDT, the difference between flowering and fruiting dates) have remained unstudied. Here we compiled reproductive phenology (flowering and fruiting time) and species distribution data for 6838 angiosperm species in China to explore whether FDT is more phylogenetically conserved as latitude and elevation increase, whether the phylogenetic signal of FDT correlates with phylogenetic structure and potential climatic drivers across China, and whether the environmental determinants of phylogenetic signal of FDT differ between herbaceous and woody species.
China
We divided China into 268 200 × 200 km grid cells and calculated the phylogenetic signals of FDT in each grid cell using pagel’s λ. We then regressed the phylogenetic signals of FDT as a function of either latitude or elevation, individually. We examined the relationship between phylogenetic signals of FDT and climate variables using both ordinary and spatial linear regressions. We also examined the relationship between the phylogenetic signal of FDT and either net relatedness index (NRI) or clade age of each grid-cell.
We found that phylogenetic signals in FDT increased as elevation and latitude increased. The Pagel’s λ of FDT was negatively correlated with clade age but positively correlated with NRI. Precipitation in the wettest quarter was the primary variable affecting the phylogenetic signal for herbaceous species, while minimum temperature of the coldest month and temperature seasonality were the two most important climatic factors for woody species.
Strength of phylogenetic conservatism of FDT is greater at higher latitudes and elevations. The latitudinal and elevational patterns, where mean clade age of species lowers as temperature decreases, and angiosperm assemblages tend to be more phylogenetically clustered at higher elevations and higher latitudes, could be explained by the Tropical Niche Conservatism hypothesis. The phylogenetic signals of herbs and of woody plants are triggered by different climatic drivers. Our findings have important implications for the study of large-scale geographical gradients in plant species richness, phylogenetic diversity and community assembly.
With the development of biodiversity informatics, more and more data repositories have emerged, providing massive stores of open scientific data. The use of open data is increasingly valuable for ...scientific research and related decision making but little is known about which topics are addressed, especially in non-English publications. Further, how this data should be cited has been called into question. The Global Biodiversity Information Facility (GBIF) is the world’s largest and most widely-used open data access platform on the occurrence of species in nature. Here, we analyze the use of GBIF-mediated data in Chinese language publications. From 623 publications containing the word “GBIF”, we obtained 324 peer-reviewed publications. Among these publications, there were 237 journal papers, 17 doctoral theses, 66 master theses, and 4 conference papers. The publications came from 114 journals and 49 research institutes and universities. We found that the most common topics addressed by these publications were species distribution, climate change, biological invasion and medicinal plants. For data citation, multiple forms coexist. 295 publications (90% of publications) only cited the name of “GBIF” in the main text, without a Digital Object Identifier (DOI). Among the 29 publications that cited GBIF in the references, 17 cited the GBIF website, 8 publications listed the URL of a species page in GBIF, and only 4 publications cited a DOI, which is what GBIF recommends. Based on a discussion on the use of GBIF-mediated data and the resulting data citation issues, this study makes three suggestions to improve data citation practice, which are applicable to data citation practice in other non-English publications.
•Among 324 publications, multiple forms of data citation coexisted.•295 publications cited GBIF in the main text without DOIs, and only 4 publications cited data with the DOIs.•Suggested to draw on international experience to intensify the existing data policies.•Called for attention of data citation in other non-English publications.
The distribution and etching rate of flow pattern defects (FPDs) in germanium- doped Czochralski (GCZ) silicon (Si) wafers with light and heavy dopants—either boron (B) or phosphorus (P)—have been ...investigated. In the lightly doped (both B and P) Czochralski (CZ) Si crystals, the FPD densities in GCZ Si decrease with the increase of Ge concentration. In the heavily B-doped GCZ Si crystals, the FPDs are denser compared with the heavily B-doped CZ Si, whereas the reverse is true in the heavily P-doped GCZ Si and CZ Si crystals. It is also shown that the etching rates in the lightly doped CZ Si crystals can be slightly enlarged by the Ge doping. It is proposed that, in lightly doped GCZ Si, Ge doping could consume free vacancies and thus form high-density but small-sized voids, while the stress compensation induced by B and Ge atoms could increase the vacancy concentration in heavily B-doped GCZ Si, leading to sparse and large-sized voids.
Fruit type, an important reproductive trait, is closely related to reproduction strategy, community dynamics and biotic interactions. However, limited research has explored the geographic ...distribution of fruit type and the underlying abiotic factors influencing this on a large scale. Here we aim to study large-scale distribution patterns of fleshy-fruited plant species and the most important environmental drivers for different growth forms in utilizing the fruit type and distribution data for over 27000 plant species in China. Results indicated that the proportion of fleshy-fruited species was higher in southeast China, and this pattern was consistent between different growth forms. Overall, the proportion of fleshy-fruited species was higher in wet, warm, and stable environments. Notably, mean annual precipitation had the greatest predictive contribution to woody fleshy-fruited species distributions, but mean annual temperature best predicted the herbaceous fleshy-fruited species distributions. We provide the first map of a large-scale distribution of fleshy-fruited plant species for different growth forms in the northern hemisphere and show that these geographic patterns are mainly determined by contrasting climatic gradients. Recognizing that climate factors have different relationships with different growth forms of fleshy-fruited species advances our knowledge about fruit type and environment. This work contributes to predictions of the global distribution of fleshy-fruited species under future climate change scenarios and provides a reference for continued research on the complex interactions between plants, frugivores and the environment.
Tropical and subtropical forest ecosystems play an important role in the global carbon regulation. Despite increasing evidence for effects of biodiversity (species diversity, functional diversity and ...functional dominance), stand structural attributes, stand age and environmental conditions (climate and topography) on tree carbon storage, the relative importance of these drivers at large scale is poorly understood. It is also still unclear whether biodiversity effects on tree carbon storage work through niche complementarity (i.e. increased tree carbon storage due to interspecific resource partitioning) or through the mass-ratio effect (tree carbon storage regulated by dominant traits within communities). Here we analyze tree carbon storage and its drivers using data of 480 plots sampled across subtropical forests in China. We use multiple regression models to test the relative effects of biodiversity, stand structural attributes, stand age and environmental conditions on tree carbon storage, and use a partial least squares path model to test how these variables directly and/or indirectly affect tree carbon storage. Our results show that tree carbon storage is most strongly affected by stand age, followed by climate, biodiversity and stand structural attributes. Stand age and climate had both direct and indirect (through species diversity, functional dominance and stand structural attributes) effects. We find that tree carbon storage correlates with both species diversity and functional dominance after stand age and environmental drivers are accounted for. Our results suggest that niche complementarity and the mass-ratio effect, not necessarily mutually exclusive, both play a role in maintaining ecosystem functioning. Our results further indicate that biodiversity conservation might be an effective way for enhancing tree carbon storage in natural, species-rich forest ecosystems.
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•Biodiversity enhances tree carbon storage in subtropical forests.•Niche complementarity and mass-ratio effect both play a role in maintaining ecosystem functioning.•Stand age, stand structure and environmental conditions all affect tree carbon storage.
Ongoing habitat loss and fragmentation caused by human activities represent one of the greatest causes of biodiversity loss. However, the effects of habitat loss and fragmentation are not felt ...equally among species. Here, we examined how habitat loss influenced the diversity and abundance of species from different trophic levels, with different traits, by taking advantage of an inadvertent experiment that created habitat islands from a once continuous forest via the creation of the Thousand Island Lake, a large reservoir in China. On 28 of these islands with more than a 9000‐fold difference in their area (0.12–1154 ha), we sampled plants, herbivorous insects, and predatory insects using effort‐controlled sampling and analyses. This allowed us to discern whether any observed differences in species diversity were due to passive sampling alone or to demographic effects that disproportionately influenced some species relative to others. We found that while most metrics of sampling effort‐controlled diversity increased with island area, the strength of the effect was exacerbated for species in higher trophic levels. When we more explicitly examined differences in species composition among islands, we found that the pairwise difference in species composition among islands was dominated by species turnover but that nestedness increased with differences in island area, indicating that some species are more likely to be absent from smaller islands. Furthermore, by examining trends of several dispersal‐related traits of species, we found that species with lower dispersal propensity tended to be those that were lost from smaller islands, which was observed for herbivorous and predatory insects. Our results emphasize the importance of incorporating within‐patch demographic effects, as well as the taxa and traits of species when understanding the influence of habitat loss on biodiversity.
•Species diversity enhanced soil organic carbon storage in subtropical forests.•Soil organic carbon storage decreased with MAT and MAP in subtropical forests.•Soil organic carbon storage was closely ...related to leaf litter C/N and root biomass.
Tropical and subtropical forest ecosystems play an important role in the global carbon regulation. Although positive relationships between biodiversity and soil organic carbon (SOC) storage have been found in experimental grasslands, biodiversity effects on SOC storage in natural forests remain debated. Based on a large dataset from 523 forest inventory plots across subtropical forests in China, we tested the relationship between biodiversity and SOC storage and examined whether environmental conditions (temperature, precipitation, soil properties) and litter quantity (leaf litter and root biomass) and quality (leaf litter carbon to nitrogen ratio leaf litter C/N) had effects on SOC storage. Furthermore, we used linear mixed-effects models to test the relative effects of biodiversity, environmental conditions, and litter quantity and quality on SOC storage. We used structural equation models to test how these variables directly or indirectly affected SOC storage. We found that species diversity, together with climatic factors (mean annual temperature and mean annual precipitation), leaf litter C/N and root biomass determined SOC storage in subtropical forests at a large spatial scale. SOC storage was most strongly affected by climatic factors, followed by leaf litter C/N. Species diversity had both direct and indirect (through root biomass and leaf litter C/N) effects on SOC storage after accounting for environmental conditions. We also found that the positive diversity–SOC storage relationships were stronger in low and medium mean annual precipitation. Our findings highlight that higher species diversity can lead to higher SOC storage and therefore the conservation of biodiversity could play an important role in climate change mitigation.
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