Aim: Recent advances in the availability of species distributional and high-resolution environmental data have facilitated the investigation of species richness—environment relationships. However, ...even exhaustive distributional databases are prone to geographical sampling bias. We aim to quantify the inventory incompleteness of vascular plant data across 2377 Chinese counties and to test whether inventory incompleteness affects the analysis of richness—environment relationships and spatial predictions of species richness. Location: China. Methods: We used the most comprehensive database of Chinese vascular plants, which includes county-level occurrences for 29,012 native species derived from 4,236,768 specimen and literature records. For each county, we computed smoothed species accumulation curves and used the mean slope of the last 10% of the curves as a proxy for inventory incompleteness. We created a series of data subsets with different levels of inventory incompleteness by excluding successively more under-sampled counties from the full data set. We then applied spatial and non-spatial regression models to each of these subsets to investigate relationships between the species richness of subsets and environmental factors, and to predict spatial patterns of vascular plant species richness in China. Results: Log 10 -transformed numbers of records and documented species were strongly correlated (r = 0.97). In total, 91% of Chinese counties were identified as under-sampled. After controlling for inventory incompleteness, the overall explanatory power of environmental factors markedly increased, and the strongest predictor of species richness switched from elevational range to annual wet days. Environmental models calibrated with more complete inventories yielded better spatial predictions of species richness. Main conclusions: Our results indicate that inventory incompleteness strongly affects the explanatory power of environmental factors, the main determinants of species richness obtained from regression analyses, and the reliability of environment-based spatial predictions of species richness. We conclude that even large distributional databases are prone to geographical sampling bias, with far-reaching implications for the perception of and inferences about macroecological patterns.
Spatial patterns of biodiversity are inextricably linked to their collection methods, yet no synthesis of bias patterns or their consequences exists. As such, views of organismal distribution and the ...ecosystems they make up may be incorrect, undermining countless ecological and evolutionary studies. Using 742 million records of 374 900 species, we explore the global patterns and impacts of biases related to taxonomy, accessibility, ecotype and data type across terrestrial and marine systems. Pervasive sampling and observation biases exist across animals, with only 6.74% of the globe sampled, and disproportionately poor tropical sampling. High elevations and deep seas are particularly unknown. Over 50% of records in most groups account for under 2% of species and citizen‐science only exacerbates biases. Additional data will be needed to overcome many of these biases, but we must increasingly value data publication to bridge this gap and better represent species' distributions from more distant and inaccessible areas, and provide the necessary basis for conservation and management.
1. Ecologists have long recognized that plant performance is affected by the density and composition of neighbouring individuals. With the advent of highly resolved species-level phylogenies, it has ...become possible to test whether such density-dependent neighbourhood interactions are also phylogenetically dependent. Most studies of density dependence have focused on a single life stage; however, the relative importance of different neighbourhood interactions may shift over the lifetime of an individual. 2. We examined effects of conspecific neighbour density, heterospecific neighbour density and average phylogenetic relatedness of heterospecific neighbours on the survival of seedlings, saplings, juveniles and adult trees of 29 focal tree species using long-term, spatially explicit forest dynamics data and a highly resolved DNA barcode phylogeny from the tropical forest of Barro Colorado Island (BCI), Panama. 3. Our results show a decline in the strength of conspecific negative density dependence across life stages: strong negative conspecific neighbour effects at early life stages gave way to weak positive conspecific neighbour effects for adult trees. In contrast, the effect of heterospecific neighbour density on survival showed no clear trend with life stage. 4. We found evidence of phylogenetic density dependence in the BCI forest, with a significant negative impact of neighbourhood relatedness on focal tree survival, but only for later life stages. In contrast to studies from other tropical forests, neighbourhood relatedness had a significant positive effect on seedling survival. 5. Furthermore, we found that focal species varied much more widely in their sensitivity to conspecific neighbour density than in their reactions to heterospecific neighbour density or phylogenetic relatedness. 6. Synthesis. Overall, our results demonstrate that both conspecific density dependence and phylogenetic density dependence influence tropical tree survival, but that their relative importance varies with life stage and among species. Our study highlights the need to incorporate multiple life stages and multiple species when assessing the factors contributing to individual survival and species coexistence for long-lived organisms.
Forest ecosystems are an integral component of the global carbon cycle as they take up and release large amounts of C over short time periods (C flux) or accumulate it over longer time periods (C ...stock). However, there remains uncertainty about whether and in which direction C fluxes and in particular C stocks may differ between forests of high versus low species richness. Based on a comprehensive dataset derived from field-based measurements, we tested the effect of species richness (3-20 tree species) and stand age (22-116 years) on six compartments of above- and below-ground C stocks and four components of C fluxes in subtropical forests in southeast China. Across forest stands, total C stock was 149 ± 12 Mg ha
with richness explaining 28.5% and age explaining 29.4% of variation in this measure. Species-rich stands had higher C stocks and fluxes than stands with low richness; and, in addition, old stands had higher C stocks than young ones. Overall, for each additional tree species, the total C stock increased by 6.4%. Our results provide comprehensive evidence for diversity-mediated above- and below-ground C sequestration in species-rich subtropical forests in southeast China. Therefore, afforestation policies in this region and elsewhere should consider a change from the current focus on monocultures to multi-species plantations to increase C fixation and thus slow increasing atmospheric CO
concentrations and global warming.
Aim: Effort in collecting biodiversity information often varies strongly in space and may be driven by environmental, cultural and socio-economic factors. Understanding the constraints on collecting ...effort is crucial for identifying potential bias in distributional databases and for making future surveys more efficient. Here we test six competing hypotheses on drivers of geographical variation in collecting effort and identify the main factors shaping the geography of floristic collections in China. Location: China. Methods: We used the most comprehensive database of Chinese vascular plant distributions including 4,338,516 county-level occurrences derived from herbarium specimens and literature sources. Explanatory variables were assembled representing six different hypotheses: accessibility, human population density, the 'botanist effect', mountains, water availability and conservation priority. Ordinary least-squares models with eigenvector-based spatial filters were applied to investigate their effects on spatial patterns of two different facets of collecting effort, i.e. collection density and inventory incompleteness. Results: All hypotheses except accessibility and human population density received significant support. Elevational range was the strongest predictor with a positive effect on collection density. Inventory incompleteness in turn was best predicted by human population density, but unexpectedly showed a positive effect. In contrast to previous studies, collecting effort was only weakly and negatively related to road density. Counties with herbaria had significantly higher collecting effort, and the presence of herbaria had weakly positive effects on neighbouring counties. Main conclusions: Our results indicate that China's mountains are most intensively and completely collected, whereas densely populated areas are surprisingly under-sampled. Because densely populated areas are more seriously threatened by land-use change, our results show a need to increase biological collections in those areas for conservation assessment and monitoring. More generally, our study suggests that collecting effort and its environmental and socio-economic constraints have a strong region-specific component influenced by cultural context and by different botanical traditions.
In an era when global biodiversity is increasingly impacted by rapidly changing climate, efforts to conserve global biodiversity may be compromised if we do not consider the uneven distribution of ...climate-induced threats. Here, via a novel application of an aggregate Regional Climate Change Index (RCCI) that combines changes in mean annual temperature and precipitation with changes in their interannual variability, we assess multi-dimensional climate changes across the "Global 200" ecoregions - a set of priority ecoregions designed to "achieve the goal of saving a broad diversity of the Earth's ecosystems" - over the 21(st) century. Using an ensemble of 62 climate scenarios, our analyses show that, between 1991-2010 and 2081-2100, 96% of the ecoregions considered will be likely (more than 66% probability) to face moderate-to-pronounced climate changes, when compared to the magnitudes of change during the past five decades. Ecoregions at high northern latitudes are projected to experience most pronounced climate change, followed by those in the Mediterranean Basin, Amazon Basin, East Africa, and South Asia. Relatively modest RCCI signals are expected over ecoregions in Northwest South America, West Africa, and Southeast Asia, yet with considerable uncertainties. Although not indicative of climate-change impacts per se, the RCCI-based assessment can help policy-makers gain a quantitative and comprehensive overview of the unevenly distributed climate risks across the G200 ecoregions. Whether due to significant climate change signals or large uncertainties, the ecoregions highlighted in the assessment deserve special attention in more detailed impact assessments to inform effective conservation strategies under future climate change.
Background and aims
Home-field advantage (HFA) hypothesis predicts that plant litter decomposes faster beneath the plant species from which it was derived than beneath other plant species. However, ...it remains unclear, which groups of soil organisms drive HFA effects across a wide range of litter quality and forest types.
Methods
We set up a reciprocal transplant decomposition experiment to quantify the HFA effects of broadleaf, coniferous and bamboo litters. Litterbags of different mesh sizes and high-throughput pyrosequencing of microbial rRNA gene were used to test the contribution of different decomposer groups to HFA effect.
Results
The recalcitrant broadleaf litter and the labile bamboo litter exhibited HFA. Presence of meso-and macrofauna did not substantially change the HFA effects. Bacterial and fungal community composition on litters were significantly influenced by litter type. Bacterial community composition remained unchanged when the same litter was decomposed in different forest types, whereas fungal community composition on broadleaf and bamboo litters were significantly influenced by incubation site.
Conclusions
Our data demonstrate specific association between fungal community composition and faster litter decomposition in the home site, suggesting that fungi probably participate in driving the HFA effect of broadleaf and bamboo litters.
Development of long tree-ring records is an important task in paleoclimate studies. Here we presented a five-century long reconstruction of summer (June to August) temperature based on a tree ...ring-width chronology of
Picea brachytyla
var.
complanata
originating from the Hengduan Mountains of China. Climate-growth response analysis showed that summer temperature was the main climatic factor limiting tree-ring growth in the study area. The reconstructed summer temperature accounted for 47.6% of the variance in actual temperature during their common period A.D. 1958–2002. Analysis of the temperature reconstruction showed that major warm periods occurred in the A.D. 1710s–1750s, 1850s, 1920s–1950s and 1990s to present, whereas cold intervals occurred in the A.D. 1630s–1680s, 1790s–1800s, 1860s–1880s and 1950s–1980s, respectively. The low-frequency variation of the reconstruction agreed fairly well with tree-ring reconstructed temperature from nearby regions and with records of glacier fluctuations in the surrounding high mountains, suggesting that our reconstructed summer temperature was reliable, and could aid in the evaluation of regional climate variability.
Human-induced biodiversity change impairs ecosystem functions crucial to human well-being. However, the consequences of this change for ecosystem multifunctionality are poorly understood beyond ...effects of plant species loss, particularly in regions with high biodiversity across trophic levels. Here we adopt a multitrophic perspective to analyze how biodiversity affects multifunctionality in biodiverse subtropical forests. We consider 22 independent measurements of nine ecosystem functions central to energy and nutrient flow across trophic levels. We find that individual functions and multifunctionality are more strongly affected by the diversity of heterotrophs promoting decomposition and nutrient cycling, and by plant functional-trait diversity and composition, than by tree species richness. Moreover, cascading effects of higher trophic-level diversity on functions originating from lower trophic-level processes highlight that multitrophic biodiversity is key to understanding drivers of multifunctionality. A broader perspective on biodiversity-multifunctionality relationships is crucial for sustainable ecosystem management in light of non-random species loss and intensified biotic disturbances under future environmental change.
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