1. Ecosystem functioning relies heavily on below-ground processes, which are largely regulated by plant fine-roots and their functional traits. However, our knowledge of fine-root trait distribution ...relies to date on local- and regional-scale studies with limited numbers of species, growth forms and environmental variation. 2. We compiled a world-wide fine-root trait dataset, featuring 1115 species from contrasting climatic areas, phylogeny and growth forms to test a series of hypotheses pertaining to the influence of plant functional types, soil and climate variables, and the degree of manipulation of plant growing conditions on species fine-root trait variation. Most particularly, we tested the competing hypotheses that fine-root traits typical of faster return on investment would be most strongly associated with conditions of limiting versus favourable soil resource availability. We accounted for both data source and species phylogenetic relatedness. 3. We demonstrate that: (i) Climate conditions promoting soil fertility relate negatively to fine-root traits favouring fast soil resource acquisition, with a particularly strong positive effect of temperature on fine-root diameter and negative effect on specific root length (SRL), and a negative effect of rainfall on root nitrogen concentration; (ii) Soil bulk density strongly influences species fine-root morphology, by favouring thicker, denser fine-roots; (iii) Fine-roots from herbaceous species are on average finer and have higher SRL than those of woody species, and N2-fixing capacity positively relates to root nitrogen; and (iv) Plants growing in pots have higher SRL than those grown in the field. 4. Synthesis. This study reveals both the large variation in fine-root traits encountered globally and the relevance of several key plant functional types and soil and climate variables for explaining a substantial part of this variation. Climate, particularly temperature, and plant functional types were the two strongest predictors of fine-root trait variation. High trait variation occurred at local scales, suggesting that wide-ranging below-ground resource economics strategies are viable within most climatic areas and soil conditions.
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1. Conceptual frameworks relating plant traits to ecosystem processes such as organic matter dynamics are progressively moving from a leaf-centred to a whole-plant perspective. Through the use of ...meta-analysis and global literature data, we quantified the relative roles of litters from above-and below-ground plant organs in ecosystem labile organic matter dynamics. 2. We found that decomposition rates of leaves, fine roots and fine stems were coordinated across species worldwide although less strongly within ecosystems. We also show that fine roots and stems had lower decomposition rates relative to leaves, with large differences between woody and herbaceous species. Further, we estimated that on average below-ground litter represents approximately 33 and 48% of annual litter inputs in grasslands and forests, respectively. 3. These results suggest a major role for below-ground litter as a driver of ecosystem organic matter dynamics. We also suggest that, given that fine stem and fine root litters decompose approximately 1.5 and 2.8 times slower, respectively, than leaf litter derived from the same species, cycling of labile organic matter is likely to be much slower than predicted by data from leaf litter decomposition only. 4. Synthesis. Our results provide evidence that within ecosystems, the relative inputs of above-versus belowground litter strongly control the overall quality of the litter entering the decomposition system. This in turn determines soil labile organic matter dynamics and associated nutrient release in the ecosystem, which potentially feeds back to the mineral nutrition of plants and therefore plant trait values and plant community composition.
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Predicting climate change impact on ecosystem structure and services is one of the most important challenges in ecology. Until now, plant species response to climate change has been described at the ...level of fixed plant functional types, an approach limited by its inflexibility as there is much interspecific functional variation within plant functional types. Considering a plant species as a set of functional traits greatly increases our possibilities for analysis of ecosystem functioning and carbon and nutrient fluxes associated therewith. Moreover, recently assembled large-scale databases hold comprehensive per-species data on plant functional traits, allowing a detailed functional description of many plant communities on Earth. Here, we show that plant functional traits can be used as predictors of vegetation response to climate warming, accounting in our test ecosystem (the species-rich alpine belt of Caucasus mountains, Russia) for 59% of variability in the per-species abundance relation to temperature. In this mountain belt, traits that promote conservative leaf water economy (higher leaf mass per area, thicker leaves) and large investments in belowground reserves to support next year’s shoot buds (root carbon content) were the best predictors of the species increase in abundance along with temperature increase. This finding demonstrates that plant functional traits constitute a highly useful concept for forecasting changes in plant communities, and their associated ecosystem services, in response to climate change.
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A significant fraction of carbon stored in the Earth's soil moves through arbuscular mycorrhiza (AM) and ectomycorrhiza (EM). The impacts of AM and EM on the soil carbon budget are poorly understood.
...We propose a method to quantify the mycorrhizal contribution to carbon cycling, explicitly accounting for the abundance of plant-associated and extraradical mycorrhizal mycelium. We discuss the need to acquire additional data to use our method, and present our new global database holding information on plant species-by-site intensity of root colonization by mycorrhizas. We demonstrate that the degree of mycorrhizal fungal colonization has globally consistent patterns across plant species. This suggests that the level of plant species-specific root colonization can be used as a plant trait.
To exemplify our method, we assessed the differential impacts of AM : EM ratio and EM shrub encroachment on carbon stocks in sub-arctic tundra. AM and EM affect tundra carbon stocks at different magnitudes, and via partly distinct dominant pathways: via extraradical mycelium (both EM and AM) and via mycorrhizal impacts on above- and belowground biomass carbon (mostly AM).
Our method provides a powerful tool for the quantitative assessment of mycorrhizal impact on local and global carbon cycling processes, paving the way towards an improved understanding of the role of mycorrhizas in the Earth's carbon cycle.
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Fungi are highly diverse organisms, which provide multiple ecosystem services. However, compared with charismatic animals and plants, the distribution patterns and conservation needs of fungi have ...been little explored. Here, we examined endemicity patterns, global change vulnerability and conservation priority areas for functional groups of soil fungi based on six global surveys using a high‐resolution, long‐read metabarcoding approach. We found that the endemicity of all fungi and most functional groups peaks in tropical habitats, including Amazonia, Yucatan, West‐Central Africa, Sri Lanka, and New Caledonia, with a negligible island effect compared with plants and animals. We also found that fungi are predominantly vulnerable to drought, heat and land‐cover change, particularly in dry tropical regions with high human population density. Fungal conservation areas of highest priority include herbaceous wetlands, tropical forests, and woodlands. We stress that more attention should be focused on the conservation of fungi, especially root symbiotic arbuscular mycorrhizal and ectomycorrhizal fungi in tropical regions as well as unicellular early‐diverging groups and macrofungi in general. Given the low overlap between the endemicity of fungi and macroorganisms, but high conservation needs in both groups, detailed analyses on distribution and conservation requirements are warranted for other microorganisms and soil organisms.
Using a long‐read metabarcoding approach, we found that the endemicity of all fungi and most functional groups peaks in tropical habitats, including Amazonia, Yucatan and West‐Central Africa, with a negligible island effect compared with plants and animals. Fungi are predominantly vulnerable to drought, heat and land cover change, particularly in dry tropical regions with high human population density. Fungal conservation areas of highest priority include herbaceous wetlands, tropical forests and woodlands.
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The alpine vegetation of Europe and the Caucasus has experienced substantial changes due to climate warming and reduced grazing. Exposed ridge communities, such as alpine heaths, are presumed to be ...less vulnerable to such processes. Herein, we analyze long-term dynamics (over 37 years) of an alpine lichen heath in the Teberda State Biosphere Reserve, Karachaevo-Cherkessian Republic, Russia. We counted the shoots of all vascular plants present on permanent plots. Autocorrelated linear regressions, a non-metric multidimensional scaling ordination, and a fourth-corner analysis were applied to characterize the relationships between shoot numbers, climate variables (temperatures and precipitation), functional traits, and species strategies. Nine species, including dominant Festuca ovina L. and Antennaria dioica (L.) Gaertn., increased their abundances, whereas Carex spp. were observed to decrease. The overall dynamics were mainly driven by increasing mean temperatures during the growing season (July and August). None of the changes observed in the selected traits were correlated with increasing or decreasing numbers of species; however, some traits (plant height, specific root length, specific leaf area, and leaf carbon content) were potentially associated with climate variables. The observed dynamics suggested an overall increase in the abundance of herbaceous plants. Generally, our results support “greening” effects in tundra and alpine biomes.
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Aim
Predictions of plant traits over space and time are increasingly used to improve our understanding of plant community responses to global environmental change. A necessary step forward is to ...assess the reliability of global trait predictions. In this study, we predict community mean plant traits at the global scale and present a systematic evaluation of their reliability in terms of the accuracy of the models, ecological realism and various sources of uncertainty.
Location
Global.
Time period
Present.
Major taxa studied
Vascular plants.
Methods
We predicted global distributions of community mean specific leaf area, leaf nitrogen concentration, plant height and wood density with an ensemble modelling approach based on georeferenced, locally measured trait data representative of the plant community. We assessed the predictive performance of the models, the plausibility of predicted trait combinations, the influence of data quality, and the uncertainty across geographical space attributed to spatial extrapolation and diverging model predictions.
Results
Ensemble predictions of community mean plant height, specific leaf area and wood density resulted in ecologically plausible trait–environment relationships and trait–trait combinations. Leaf nitrogen concentration, however, could not be predicted reliably. The ensemble approach was better at predicting community trait means than any of the individual modelling techniques, which varied greatly in predictive performance and led to divergent predictions, mostly in African deserts and the Arctic, where predictions were also extrapolated. High data quality (i.e., including intraspecific variability and a representative species sample) increased model performance by 28%.
Main conclusions
Plant community traits can be predicted reliably at the global scale when using an ensemble approach and high‐quality data for traits that mostly respond to large‐scale environmental factors. We recommend applying ensemble forecasting to account for model uncertainty, using representative trait data, and more routinely assessing the reliability of trait predictions.
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Questions: Festuca varia grasslands occupy extensive areas in the alpine belt of the Caucasus. In the Teberda Reserve the dominant, narrow-leaved grasses Festuca varia and Nardus stricta contribute ...up to 56% and 22%, respectively, to the total biomass of the community. How does community composition and structure change after removal of the dominant, and is any species able to replace dominants in abundance and function? Location: Teberda State Biosphere Reserve, northwestern Caucasus, Russia. Methods: We experimentally removed F. varia and N. stricta (as single dominants and both together). After 20 yr of treatment we compared the expected increase in species richness per plot, above-ground phytomass, community biomass-weighted mean SLA and leaf DMC, as well as the inter-annual dynamics of functional groups and the most abundant species. Results: Dominant removal led to a decrease in litter after removal of F. varia and of both dominants, and a decrease in total phytomass after removal of both dominants. Biomass of dominants did not respond to the treatments, however N. stricta increased shoot number after F. varia removal. Non-dominant narrow-leaved grasses increased in all the treatments, both in biomass and shoot number. Community biomass-weighted SLA increased in all the treatments, and leaf DMC decreased. Conclusions: Dominants play a key role in alpine F. varia grasslands and determine the functional structure and composition of the community. Species from other functional groups and, remarkably, species from the same group, are not able to completely replace them. Traits of F. varia, as the main dominant, control community-weighted leaf traits and litter accumulation.
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The effects of non-flooded plastic film mulching cultivation (PM) and polymer-coated urea (PCU) on rice yield, soil properties, and weed diversity were investigated in experimental plots of rice ...monoculture in Lanxi, China. The combination of PM and PCU increased rice yield. Compared with traditional flooded cultivation, under PM, soil pH remained higher, but decreased soil organic matter, total nitrogen, available phosphorus, and exchangeable potassium in the 0- to 10-cm soil layer. Soil fertility influenced winter weed communities, with hairy bittercress, Asian mazus, and shortawn foxtail being the most abundant species. Multivariate analysis indicated that changes in the winter weed species diversity were primarily due to exchangeable potassium. PCU had no significant influence on weed diversity, while plots without nitrogen fertilizer had higher spring-germinating weed density.
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Plants are subject to trade‐offs among growth strategies such that adaptations for optimal growth in one condition can preclude optimal growth in another. Thus, we predicted that a plant species that ...responds positively to one global change treatment would be less likely than average to respond positively to another treatment, particularly for pairs of treatments that favor distinct traits. We examined plant species’ abundances in 39 global change experiments manipulating two or more of the following: CO2, nitrogen, phosphorus, water, temperature, or disturbance. Overall, the directional response of a species to one treatment was 13% more likely than expected to oppose its response to a another single‐factor treatment. This tendency was detectable across the global data set, but held little predictive power for individual treatment combinations or within individual experiments. Although trade‐offs in the ability to respond to different global change treatments exert discernible global effects, other forces obscure their influence in local communities.
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