The plant economics spectrum integrates trade-offs and covariation in resource economic traits of different plant organs and their consequences for pivotal ecosystem processes, such as decomposition. ...However, in this concept stems are often considered as one unit ignoring the important functional differences between wood (xylem) and bark. These differences may not only affect the performance of woody plants during their lifetime, but may also have important “afterlife effects.” Specifically, bark quality may strongly affect deadwood decomposition of different woody species. We hypothesized that (1) bark quality strongly influences bark decomposability to microbial decomposers, and possibly amplifies the interspecific variation in decomposition by invertebrate consumption, especially termites; and (2) bark decomposition has secondary effects on xylem mass loss by providing access to decomposers including invertebrates such as termites. We tested these hypotheses across 34 subtropical woody species representing five common plant functional types, by conducting an in situ deadwood decomposition experiment over 12-month in two sites in subtropical evergreen broadleaved forest in China. We employed visual examination and surface density measurement to quantify termite consumption to both bark and the underlying xylem, respectively. Using principal component analysis, we synthesized seven bark traits to provide the first empirical evidence for a bark economics spectrum (BES), with high BES values (i.e., bark thickness, nitrogen, phosphorus, and cellulose contents) indicating a resource acquisitive strategy and low BES values (i.e., carbon, lignin, and dry matter contents) indicating a resource conservative strategy. The BES affected interspecific variation in bark mass loss and this relationship was strongly amplified by termites. The BES also explained nearly half of the interspecific variation in termite consumption to xylem, making it an important contributor to deadwood decomposition overall. Moreover, the above across-species relationships manifested also within plant functional types, highlighting the value of using continuous variation in bark traits rather than categorical plant functional types in carbon cycle modeling. Our findings demonstrate the potent role of the BES in influencing deadwood decomposition including positive invertebrate feedback thereon in warm-climate forests, with implications for the role of bark quality in carbon cycling in other woody biomes.
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Epixylic vegetation may be important in dead wood decay by altering the microenvironment and, thereby, microbial communities in logs. However, the interaction between epixylic vegetation and dead ...wood microbial communities remains poorly known. Therefore, repeated experimental epixylic (bryophyte-dominated) vegetation removal (ERM) from logs of the fir Abies faxoniana across a wide range of decay classes (I–V) was conducted on the eastern Tibetan Plateau. The dynamics of the microbial community were separately measured in heartwood, sapwood and bark using the phospholipid fatty acid analysis (PLFA) method. Our results showed that the effects of ERM on the microbial community depended greatly on the three log components and sampling seasons but less on decay class. (1) The absence of epixylic vegetation generally enhanced the total microbial biomass and Sørensen similarity in bark, whereas it had a more complicated effect on those in heartwood and sapwood. Specifically, the response to ERM became progressively stronger from winter until the late growing season. (2) ERM increased the total percentage of Gram-negative bacteria and fungi in heartwood and upper side sapwood and decreased their percentages in bark. (3) The moisture content and pH of the logs were good predictors and likely drivers of the dynamic patterns of the microbial community composition. Our findings demonstrate strong and partly consistent interactions between epixylic vegetation and microbial communities. Further in-depth research should reveal how these interactions feed back to the decomposition process of logs and thereby to carbon and nutrient cycles in the alpine forest ecosystem.
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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Summary
In the context of a recent massive increase in research on plant root functions and their impact on the environment, root ecologists currently face many important challenges to keep on ...generating cutting‐edge, meaningful and integrated knowledge. Consideration of the below‐ground components in plant and ecosystem studies has been consistently called for in recent decades, but methodology is disparate and sometimes inappropriate. This handbook, based on the collective effort of a large team of experts, will improve trait comparisons across studies and integration of information across databases by providing standardised methods and controlled vocabularies. It is meant to be used not only as starting point by students and scientists who desire working on below‐ground ecosystems, but also by experts for consolidating and broadening their views on multiple aspects of root ecology. Beyond the classical compilation of measurement protocols, we have synthesised recommendations from the literature to provide key background knowledge useful for: (1) defining below‐ground plant entities and giving keys for their meaningful dissection, classification and naming beyond the classical fine‐root vs coarse‐root approach; (2) considering the specificity of root research to produce sound laboratory and field data; (3) describing typical, but overlooked steps for studying roots (e.g. root handling, cleaning and storage); and (4) gathering metadata necessary for the interpretation of results and their reuse. Most importantly, all root traits have been introduced with some degree of ecological context that will be a foundation for understanding their ecological meaning, their typical use and uncertainties, and some methodological and conceptual perspectives for future research. Considering all of this, we urge readers not to solely extract protocol recommendations for trait measurements from this work, but to take a moment to read and reflect on the extensive information contained in this broader guide to root ecology, including sections I–VII and the many introductions to each section and root trait description. Finally, it is critical to understand that a major aim of this guide is to help break down barriers between the many subdisciplines of root ecology and ecophysiology, broaden researchers’ views on the multiple aspects of root study and create favourable conditions for the inception of comprehensive experiments on the role of roots in plant and ecosystem functioning.
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1. Litter drives a wide variety of important functions in both terrestrial and aquatic ecosystems. However, the role of litter in regulating community dynamics and ecosystem processes has mostly been ...studied in terms of litter presence or amount. Besides in biogeochemistry, we still do not know how litters from distinct plant species differ in their effects on other ecosystem processes and services including biodiversity support. 2. We briefly synthesize the multiple litter functions and services by using the afterlife legacy of interspecific variation in plant morphological, physical and chemical traits as a unifying tool. We do so by explicit reference to two highly distinct but possibly interacting 'trait spectra': the widely known Resource Economic Spectrum, and the Size and Shape Spectrum, a trait-based axis ranging from small and relatively simply shaped distal plant organs to large and more intricately shaped ones. 3. Synthesis. Ecosystem services provided by plant litter are driven by either one of the trait spectra or by both. In this way, the Size and Shape Spectrum-Resource Economic Spectrum concept is a promising tool for understanding and predicting the contributions of different plant species, through the afterlife effects of their litter traits, to various important services in different ecosystems and human contexts.
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•Whether CWD has a positive effect on C sequestration in forest soils remains to be debated.•We need a comparison of the role of C from CWD and from leafy litter in soil C stabilization.•To elucidate ...the contribution of CWD to stable soil C we need to trace individual compounds.•Management of CWD should also focus on increasing sequestration in stable C pools.
Worldwide, forests have absorbed around 30% of global anthropogenic emissions of carbon dioxide (CO2) annually, thereby acting as important carbon (C) sinks. It is proposed that leaving large fragments of dead wood, coarse woody debris (CWD), in forest ecosystems may contribute to the forest C sink strength. CWD may take years to centuries to degrade completely, and non-respired C from CWD may enter the forest soil directly or in the form of dissolved organic C. Although aboveground decomposition of CWD has been studied frequently, little is known about the relative size, composition and fate of different C fluxes from CWD to soils under various substrate-specific and environmental conditions. Thus, the exact contribution of C from CWD to C sequestration within forest soils is poorly understood and quantified, although understanding CWD degradation and stabilization processes is essential for effective forest C sink management. This review aims at providing insight into these processes on the interface of forest ecology and soil science, and identifies knowledge gaps that are critical to our understanding of the effects of CWD on the forest soil C sink. It may be seen as a “call-to-action” crossing disciplinary boundaries, which proposes the use of compound-specific analytical studies and manipulation studies to elucidate C fluxes from CWD. Carbon fluxes from decaying CWD can vary considerably due to interspecific and intraspecific differences in composition and different environmental conditions. These variations in C fluxes need to be studied in detail and related to recent advances in soil C sequestration research. Outcomes of this review show that the presence of CWD may enhance the abundance and diversity of the microbial community and constitute additional fluxes of C into the mineral soil by augmented leaching of dissolved organic carbon (DOC). Leached DOC and residues from organic matter (OM) from later decay stages have been shown to be relatively enriched in complex and microbial-derived compounds, which may also be true for CWD-derived OM. Emerging knowledge on soil C stabilization indicates that such complex compounds may be sorbed preferentially to the mineral soil. Moreover, increased abundance and diversity of decomposer organisms may increase the amount of substrate C being diverted into microbial biomass, which may contribute to stable C pools in the forest soil.
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Understanding the origins and evolutionary trajectories of symbiotic partnerships remains a major challenge. Why are some symbioses lost over evolutionary time whereas others become crucial for ...survival? Here, we use a quantitative trait reconstruction method to characterize different evolutionary stages in the ancient symbiosis between legumes (Fabaceae) and nitrogen-fixing bacteria, asking how labile is symbiosis across different host clades. We find that more than half of the 1,195 extant nodulating legumes analyzed have a high likelihood (>95%) of being in a state of high symbiotic persistence, meaning that they show a continued capacity to form the symbiosis over evolutionary time, even though the partnership has remained facultative and is not obligate. To explore patterns associated with the likelihood of loss and retention of the N₂-fixing symbiosis, we tested for correlations between symbiotic persistence and legume distribution, climate, soil and trait data. We found a strong latitudinal effect and demonstrated that low mean annual temperatures are associated with high symbiotic persistence in legumes. Although no significant correlations between soil variables and symbiotic persistence were found, nitrogen and phosphorus leaf contents were positively correlated with legumes in a state of high symbiotic persistence. This pattern suggests that highly demanding nutrient lifestyles are associated with more stable partnerships, potentially because they “lock” the hosts into symbiotic dependency. Quantitative reconstruction methods are emerging as a powerful comparative tool to study broad patterns of symbiont loss and retention across diverse partnerships.
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Aim
The interactions between plants and soil microbes play crucial roles in modulating the function and stability of terrestrial ecosystems. However, the relationships between plant and soil ...microbial diversity for different taxa have remained been elusive.
Location
Northern China.
Major taxa
Plant and soil microbes of grassland ecosystems.
Time period
2018 and 2019.
Methods
We conducted a transect survey across grasslands to measure plant diversity, plant traits, and soil microbial diversity. High throughput sequencing was used to assess soil microbial diversity for bacterial 16S ribosomal RNA (16S) and fungal internal transcribed spacer (ITS) regions on an Illumina MiSeq. The random forest algorithm was used to determine the important spatial and environmental variables in predicting plant and microbial diversity, and structural equation modelling was used to examine the direct and indirect effects of climatic and edaphic variables on plant and microbial diversity.
Results
Plant diversity was positively correlated with the diversity of soil fungi, particularly for predicted arbuscular mycorrhizal fungi (AMF) and saprotrophic fungi, and they were positively related to soil nutrients and texture. However, the correlation between plant and bacterial diversity varied by phyla and functional guilds, resulting in decoupling between plant and soil bacterial diversity. Community weighted mean leaf C:N ratio indirectly decreased soil fungal diversity through a negative relationship with soil total nitrogen. Soil bacterial and fungal diversity increased with increasing functional richness of specific leaf area and stem density, respectively.
Main conclusions
These findings have contributed to unravelling the direct and indirect linkages between plant and soil fungal diversity, highlighting particularly strong linkages between plant diversity and predicted AMF and saprotrophic fungi diversity. However, we failed to detect an overall linkage between plant and soil bacterial diversity. Still, our findings suggest that integrating soil fungi into the framework of plant diversity conservation is conducive to biodiversity restoration in degraded grassland ecosystems.
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49.
Burn or rot Grootemaat, Saskia; Wright, Ian J.; van Bodegom, Peter M. ...
Functional ecology,
11/2015, Volume:
29, Issue:
11
Journal Article
Peer reviewed
Open access
Summary
In fireprone ecosystems, two important alternative fates for leaves are burning in a wildfire (when alive or as litter) or they get consumed (as litter) by decomposers. The influence of leaf ...traits on litter decomposition rate is reasonably well understood. In contrast, less is known about the influence of leaf traits on leaf and litter flammability. The aim of this study was twofold: (i) to determine which morphological and chemical leaf traits drive flammability and (ii) to determine whether different (combinations of) morphological and chemical leaf traits drive interspecific variation in decomposition and litter flammability and, in turn, help us understand the relationship between decomposability and flammability.
To explore the relationships between leaf traits and flammability of individual leaves, we used 32 evergreen perennial plant species from eastern Australia in standardized experimental burns on three types of leaf material (i.e. fresh, dried and senesced). Next, we compared these trait–flammability relationships to trait–decomposability relationships as obtained from a previous decomposition experiment (focusing on senesced leaves only).
Within the three parameters of leaf flammability that we measured, interspecific variation in time to ignition was mainly explained by specific leaf area and moisture content. Flame duration and smoulder duration were mostly explained by leaf dry mass and to a lesser degree by leaf chemistry, namely, nitrogen, phosphorus and tannin concentrations.
The variation in the decomposition constant across species was unrelated to our measures of flammability. Moreover, different combinations of morphological and chemical leaf properties underpinned the interspecific variation in decomposability and flammability. In contrast to litter flammability, decomposability was driven by lignin and phosphorus concentrations.
The decoupling of flammability and decomposability leads to three possible scenarios for species’ influence on litter fates: (i) fast‐decomposing species for which flammability is irrelevant because there will not be enough litter to support a fire; (ii) species with slow‐decomposing leaves and a high flammability; and (iii) species with slow‐decomposing leaves and a low flammability. We see potential for making use of the decoupled trait–decomposition–flammability relationships when modelling carbon and nutrient fluxes. Including information on leaf traits in models can improve the prediction of fire behaviour. We note that herbivory is another key fate for leaves, but this study was focused on fire and decomposition.
Lay Summary
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1. Carbon (C), nitrogen (N) and phosphorus (P) stoichiometries play critical roles in the function and structure of ecosystems by affecting important ecological processes. Yet, most studies to date ...have concentrated on foliar stoichiometry of phylogenetically distantly related species. 2. Here, we hypothesized that (i) plant stoichiometry of closely related species still shows biogeographic patterns because of the geographic patterns of abiotic environment at the regional scale and (ii) even related species still differ strongly in their stoichiometry owing to inherent differences in the absorption and retention of different elements. 3. To test the hypotheses, we analysed the C:N:P stoichiometry of 48 species of Artemisia and its close relatives from 65 sites across northern China. 4. Elemental concentrations and stoichiometry had no correlation with latitude or longitude but showed clear altitudinal trends. Climate had a weak effect on plant elemental concentrations and stoichiometry but not on C concentration. Soil chemistry had significant effects on C and P concentrations, C:P and N:P. Nested models revealed that species identity accounted for more than 30% of the total variance of all elemental concentrations and stoichiometric ratios, and different species responded differently to environmental gradients. 5. Synthesis. Our results highlight that even closely related species can vary importantly in plant elemental stoichiometry. This suggests that ecologists and global change researchers should be careful not to simply take a species' stoichiometry as representative of an entire taxonomic group for upscaling of plant chemical responses to climatic and edaphic variation in our fast changing world.
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