15 research outputs found
Direct and indirect effects of climate on richness drive the latitudinal diversity gradient in forest trees
Data accessibility statement: Full census data are available upon reasonable request from the ForestGEO data portal, http://ctfs.si.edu/datarequest/ We thank Margie Mayfield, three anonymous reviewers and Jacob Weiner for constructive comments on the manuscript. This study was financially supported by the National Key R&D Program of China (2017YFC0506100), the National Natural Science Foundation of China (31622014 and 31570426), and the Fundamental Research Funds for the Central Universities (17lgzd24) to CC. XW was supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB3103). DS was supported by the Czech Science Foundation (grant no. 16-26369S). Yves Rosseel provided us valuable suggestions on using the lavaan package conducting SEM analyses. Funding and citation information for each forest plot is available in the Supplementary Information Text 1.Peer reviewedPostprin
Interactions between all pairs of neighboring trees in 16 forests worldwide reveal details of unique ecological processes in each forest, and provide windows into their evolutionary histories
When Darwin visited the Galapagos archipelago, he observed that, in spite of the islandsâ physical similarity, members of species that had dispersed to them recently were beginning to diverge from each other. He postulated that these divergences must have resulted primarily from interactions with sets of other species that had also diverged across these otherwise similar islands. By extrapolation, if Darwin is correct, such complex interactions must be driving species divergences across all ecosystems. However, many current general ecological theories that predict observed distributions of species in ecosystems do not take the details of between-species interactions into account. Here we quantify, in sixteen forest diversity plots (FDPs) worldwide, highly significant negative density-dependent (NDD) components of both conspecific and heterospecific between-tree interactions that affect the treesâ distributions, growth, recruitment, and mortality. These interactions decline smoothly in significance with increasing physical distance between trees. They also tend to decline in significance with increasing phylogenetic distance between the trees, but each FDP exhibits its own unique pattern of exceptions to this overall decline. Unique patterns of between-species interactions in ecosystems, of the general type that Darwin postulated, are likely to have contributed to the exceptions. We test the power of our null-model method by using a deliberately modified data set, and show that the method easily identifies the modifications. We examine how some of the exceptions, at the Wind River (USA) FDP, reveal new details of a known allelopathic effect of one of the Wind River gymnosperm species. Finally, we explore how similar analyses can be used to investigate details of many types of interactions in these complex ecosystems, and can provide clues to the evolution of these interactions
La survie des arbres dĂ©pend de la densitĂ© dans une ancienne forĂȘt tempĂ©rĂ©e du nordest de la Chine
Root-centric ÎČ diversity reveals functional homogeneity while phylogenetic heterogeneity in a subtropical forest
<p>Root-centric studies have revealed fast taxonomic turnover across root neighborhoods, but how such turnover is accompanied by changes in species functions and phylogeny (i.e. ÎČ diversity), which can reflect the degree of community-wide biotic homogenization, remains largely unknown, hindering better inference of below-ground assembly rules, community structuring, and ecosystem processes. We collected 2480 root segments from 625 0â30 cm soil profiles in a subtropical forest in China. Root segments were identified into 143 species with DNA-barcoding with six root morphological and architectural traits measured per species. By using the mean pairwise (Dpw) and mean nearest neighbor distance (Dnn) to quantify species ecological differences, we tested the non-random functional and phylogenetic turnover of root neighborhoods that would lend more support to deterministic over stochastic community assembly processes, examined the distance-decay pattern of ÎČ diversity, and finally partitioned ÎČ diversity into geographical and environmental components to infer their potential drivers of environmental filtering, dispersal limitation, and biotic interactions. We found that functional turnover was often lower than expected given the taxonomic turnover, whereas phylogenetic turnover was often higher than expected. Both functional and phylogenetic Dpw (e.g. interfamily species) turnover exhibited a distance-decay pattern, likely reflecting limited dispersal or abiotic filtering that leads to the spatial aggregation of specific plant lineages. Conversely, phylogenetic Dnn (e.g. intrageneric species) exhibited an inverted distance-decay pattern, likely reflecting strong biotic interactions among spatially and phylogenetically close species leading to phylogenetic divergence. While the spatial distance was generally a better predictor of ÎČ diversity than environmental distance, the joint effect of environmental and spatial distance usually overrode their respective pure effects. These findings suggest that root neighborhood functional homogeneity may somewhat increase forest resilience after disturbance by exhibiting an insurance effect. Likewise, root neighborhood phylogenetic heterogeneity may enhance plant fitness by hindering the transmission of host-specific pathogens through root networks or by promoting interspecific niche complementarity not captured by species functions. Our study highlights the potential role of root-centric ÎČ diversity in mediating community structures and functions largely ignored in previous studies.</p><p>These datasets were collected in the Guangdong Heishiding Dynamic Forest Plot in Southern China (2016). Details for each dataset are provided in the README file.</p><p>Funding provided by: National Natural Science Foundation of China<br>Crossref Funder Registry ID: http://dx.doi.org/10.13039/501100001809<br>Award Number: 31925027</p><p>Funding provided by: China Postdoctoral Science Foundation<br>Crossref Funder Registry ID: http://dx.doi.org/10.13039/501100002858<br>Award Number: 2021M70375</p><p>Funding provided by: Basic and Applied Basic Research Foundation of Guangdong Province<br>Crossref Funder Registry ID: http://dx.doi.org/10.13039/501100021171<br>Award Number: 2021A1515110362</p><p>Funding provided by: National Natural Science Foundation of China<br>Crossref Funder Registry ID: http://dx.doi.org/10.13039/501100001809<br>Award Number: 32301341</p>
How does functional distinctiveness affect single species contribution to ÎČ diversity? Evidence from a subtropical forest plot in southern China
To biologically interpret ÎČ diversity patterns, in terms of species characteristics, needs to quantify how each individual species contributes to overall ÎČ diversity (SCBD). However, the lack of studies linking SCBD to functional traits hinders to explore the full potential of the approach in biodiversity conservation. Here, we combined census data, species functional traits, and environmental variables from a 50-ha stem-mapped forest plot in southern China, with the aim to disentangle the relationship among SCBD, species functional traits and niche properties. We used nine functional traits to estimate species functional distinctiveness, and eleven environmental variables were used to compute species niche properties (niche position and niche breadth). Structural equation modeling (SEM) was applied to analyze how functional distinctiveness and niche properties jointly influenced SCBD. Results found that species with more unique trait combinations (higher functional distinctiveness) occupied marginal niche position and maintained smaller niche breadths and thus contributed less to overall ÎČ diversity. Meanwhile, functional distinctiveness and niche properties jointly determined SCBD. In addition, we found a negative effect of functional distinctiveness on SCBD, which implies the urgency of developing better biodiversity conservation strategies by unravelling the linkage between SCBD and ecosystem multifunctionality. These findings contribute to a better understanding of how species characteristics affect ÎČ diversity and making SCBD more applicable in biodiversity conservation
Nonsignificant elevational trends of soil microbial respiration and temperature sensitivity in a subtropical forest
International audienceAbstract Soil carbon (C) cycling plays a critical role in regulating global C budget and atmospheric CO 2 concentrations. The ongoing global warming potentially accelerates soil C loss induced by microbial respiration (MR) and makes soil a large C source to the atmosphere. Quantifying the drivers of MR and its response to rising temperature (also called temperature sensitivity, Q 10 ) should be a high priority to improve the modeling and prediction of terrestrial C cycle under global warming. In this study, we applied a standardized soil sampling along nine gradients from 410 to 1080âm in a subtropical forest in southern China. All soil samples were incubated at varying temperature gradients (10â15â20â25â20â15°C) to measure MR and Q 10 every day for three weeks. Then all the measured MR was adjusted by the field temperature of each elevation gradient. Our objectives were to examine the response of MR and Q 10 to the environmental change induced by elevational gradients in the subtropical forest and then quantify their main drivers. We totally collected 54 abiotic and biotic factors relative to the MR and Q 10 . Our results showed that the incubated MR increased from low to high elevation. However, a significant elevation trend of the adjusted MR was not examined after adjusting the field temperature of sampling sites, due to the tradeâoff between increasing soil C concentration and declining temperature as elevation increased. We further found that the elevational gradients did not cause significant change in Q 10 . The variation in Q 10 was negatively dominated by soil C quality, which declined nonlinearly along the elevation gradients. This study highlights the tradeâoff between environment and biotic factors in determining soil C decomposition along elevational gradients. The uncertainty of MR measurements caused by unifying incubated temperature should not be ignored in future model development
Habitat Conditions and Tree Species Shape Liana Distribution in a Subtropical Forest
Lianas are woody plants that require external support to reach the canopy. They are expanding in forests worldwide, possibly due to climate change and forest disturbance. Most studies on lianas have been conducted in tropical forests. Lianas are less explored in subtropical forests. We aimed to document the density and diversity of lianas, to test how habitat condition and the distribution of tree species affect the distributions of lianas based on data from a fully mapped 20 ha plot in subtropical China. We analyzed habitat association by fitting a generalized linear model with family-level liana abundance as response variable and family identity, and its interaction terms with topographic variables (slope, convexity, elevation, and sin(aspect)), as explanatory variables. We focused on the spatial associations of three liana species and 82 tree species with ≥100 individuals using the pair correlation function and redundancy analysis. We found a total of 1305 lianas, falling into 26 species, and 16 families, in the 20 ha plot. They accounted for 1.5% of individuals, 11.7% of species, and 0.4% of total basal area of woody plants in the plot. There were large variations in distributions of liana with respect to the four topographic variables among families, contrasting with former findings suggesting that lianas favor dry and hot habitats. The three most abundant liana species showed non-random associations with tree species, and they tended to positively associate with similar tree species but negatively associate with different tree species. The distribution of tree species explained 21.8% of variance in liana distribution. Our study suggested that both habitat conditions and tree composition intervene in determining liana distributions and that habitat heterogeneity may be a mechanism for liana diversity maintenance. Our study provides a basic understanding of liana diversity and distribution in this subtropical forest and contributes to future planning of liana studies and diversity conservation in subtropical forests under climate change
Density dependence on tree survival in an old-growth temperate forest in northeastern China
âą Density dependence is a major mechanism for shaping plant communities.
However, its role in regulating diverse, mixed natural tree communities is
less certain.
âą
In this study we investigated density-dependent effects in a large-scale (25
ha) old-growth temperate forest in northeastern China. Spatial patterns of
neighborhood distribution in the plot were analyzed using various methods
for inferring competition, including (1) pair correlation function to
determine spatial patterns of pre-mortality and post-mortality and (2)
neighborhood analysis of individuals to examine the extent to which tree
survival is correlated with other covariates.
âą
Results showed that, for common species, 3 of 5 canopy species and 3 of 8
midstory and understory species were random in mortality. Negative
density-dependent mortality was not found when trees reach 1 cm in DBH.
There was no significant correlation for canopy species between tree
survival and conspecific abundance, but largely positive correlations for
midstory and understory species. In contrast, tree survival was found to
negatively correlate with conspecific basal area for most species,
indicating strong intraspecific competition. No strong interspecific density
dependence was found in the forest.La survie des arbres dépend de la densité dans une ancienne
forĂȘt tempĂ©rĂ©e du nord-est de la Chine. âą La dĂ©pendance par rapport Ă la densitĂ© est un important
mécanisme pour la formation des communautés végétales.
Toutefois, son rÎle dans la régulation de diverses communautés
mélangées d'arbre est moins certain.
âą
Dans cette Ă©tude, nous avons enquĂȘtĂ© sur les effets densitĂ©-dĂ©pendance Ă une grande Ă©chelle (25 ha) dans une ancienne
forĂȘt tempĂ©rĂ©e, dans le nord de la Chine. Les modes de
distribution spatiale de voisinage ont été analysés en utilisant
diverses méthodes pour estimer la concurrence, y compris: (1) des paires
de fonction de corrélation afin de déterminer les structures
spatiales de pré et post-mortalité et (2) l'analyse du voisinage des
individus pour examiner dans quelle mesure la survie de l'arbre survivant
est corrélée avec d'autres variables.
âą
Les résultats ont montré que, pour les espÚces communes, 3 des 5
espÚces de la canopée et 3 des 8 de l'étage moyen et du
sous-étage, la mortalité était aléatoire. Aucune
mortalité densité-dépendante négative n'a été
dĂ©tectĂ©e lorsque les arbres atteignent 1 cm de diamĂštre Ă
hauteur d'homme. Il n'y avait pas de corrélation significative pour les
espÚces de la canopée entre la survie des arbres et l'abondance
conspécifique, mais il y avait des corrélations
positives pour l'Ă©tage moyen et le sous-Ă©tage.
âą
En revanche, la survie des arbres Ă©tait corrĂ©lĂ©e nĂ©gativement avec la surface terriĂšre conspĂ©cifique pour la plupart des espĂšces, indiquant une forte concurrence intraspĂ©cifique. Aucune dĂ©pendance visible de la densitĂ© interspĂ©cifique n'a Ă©tĂ© dĂ©tectĂ©e dans la forĂȘt
Assembly of forest communities across East Asia - insights from phylogenetic community structure and species pool scaling
Local communities are assembled from larger-scale species pools via dispersal, environmental filtering, biotic interactions, and local stochastic demographic processes. The relative importance, scaling and interplay of these assembly processes can be elucidated by comparing local communities to variously circumscribed species pools. Here we present the first study applying this approach to forest tree communities across East Asia, focusing on community phylogenetic structure and using data from a global network of tropical, subtropical and temperate forest plots. We found that Net Relatedness Index (NRI) and Nearest Taxon Index (NTI) values were generally lower with geographically broad species pools (global and Asian species pools) than with an East Asian species pool, except that global species pool produced higher NTI than the East Asian species pool. The lower NRI for the global relative to the East Asian species pool may indicate an important role of intercontinental migration during the Neogene and Quaternary and climatic conservatism in shaping the deeper phylogenetic structure of tree communities in East Asia. In contrast, higher NTI for the global relative to the East Asian species pool is consistent with recent localized diversification determining the shallow phylogenetic structure
Large Single-Crystal Cu Foils with High-Index Facets by Strain-Engineered Anomalous Grain Growth
The rich and complex arrangements of metal atoms in high-index metal facets afford appealing physical and chemical properties, which attracts extensive research interest in material science for the applications in catalysis and surface chemistry. However, it is still a challenge to prepare large-area high-index single crystals in a controllable and cost-efficient manner. Herein, entire commercially available decimeter-sized polycrystalline Cu foils are successfully transformed into single crystals with a series of high-index facets, relying on a strain-engineered anomalous grain growth technique. The introduction of a moderate thermal-contact stress upon the Cu foil during the annealing leads to the formation of high-index grains dominated by the thermal strain of the Cu foils, rather than the (111) surface driven by the surface energy. Besides, the designed static gradient of the temperature enables the as-formed high-index grain seed to expand throughout the entire Cu foil. The as-received high-index Cu foils can serve as the templates for producing high-index single-crystal Cu-based alloys. This work provides an appealing material basis for the epitaxial growth of 2D materials, and the applications that require the unique surface structures of high-index metal foils and their alloys