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Biodiversity and ecosystem-functioning theory suggest that litter mixtures composed of dissimilar leaf species can enhance decomposition due to species trait complementarity. Here we created a continuous gradient of litter chemistry trait variability within species mixtures to assess effects of litter dissimilarity on three related processes in a natural stream: litter decomposition, fungal biomass accrual in the litter, and nitrogen and phosphorus immobilization. Litter from a pool of eight leaf species was analyzed for chemistry traits affecting decomposition (lignin, nitrogen, and phosphorus) and assembled in all of the 28 possible two-species combinations. Litter dissimilarity was characterized in terms of a range of trait-diversity measures, using Euclidean and Gower distances and dendrogram-based indices. We found large differences in decomposition rates among leaf species, but no significant relationships between decomposition rate of individual leaf species and litter trait dissimilarity, irrespective of whether decomposition was mediated by microbes alone or by both microbes and litter-consuming invertebrates. Likewise, no effects of trait dissimilarity emerged on either fungal biomass accrual or changes during decomposition of nitrogen or phosphorus concentrations in individual leaf species. In line with recent meta-analyses, these results provide support for the contention that litter diversity effects on decomposition, at least in streams, are less pronounced than effects on terrestrial primary productivity.

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.

Aim Leaf litter decomposition in freshwater ecosystems is a vital process linking ecosystem nutrient cycling, energy transfer and trophic interactions. In comparison to terrestrial ecosystems, in which researchers find that litter traits predominantly regulate litter decomposition worldwide, the dominant factors controlling its decomposition in aquatic ecosystems are still debated, with global patterns not well documented. Here, we aimed to explore general patterns and key drivers (e.g., litter traits, climate and water characteristics) of leaf litter decomposition in streams worldwide. Location Global. Time period 1977–2018. Major taxa studied Leaf litter. Methods We synthesized 1,707 records of litter decomposition in streams from 275 studies. We explored variations in decomposition rates among climate zones and tree functional types and between mesh size groups. Regressions were performed to identify the factors that played dominant roles in litter decomposition globally. Results Litter decomposition rates did not differ among tropical, temperate and cold climate zones. Decomposition rates of litter from evergreen conifer trees were much lower than those of deciduous and evergreen broadleaf trees, attributed to the low quality of litter from evergreen conifers. No significant differences were found between decomposition rates of litter from deciduous and evergreen broadleaf trees. Additionally, litter decomposition rates were much higher in coarse‐ than in fine‐mesh bags, which controled the entrance of decomposers of different body sizes. Multiple regressions showed that litter traits (including lignin, C:N ratio) and elevation were the most important factors in regulating leaf litter decomposition. Main conclusions Litter traits predominantly control leaf litter decomposition in streams worldwide. Although further analyses are necessary to explore whether commonalities of the predominant role of litter traits in decomposition exist in both aquatic and terrestrial ecosystems, our findings could contribute to the use of trait‐based approaches in modelling the decomposition of litter in streams globally and exploring mechanisms of land–water–atmosphere carbon fluxes.

1. Leaf litter decomposition is a key component of global biogeochemical cycles that influence soil carbon storage, nutrient availability and plant productivity. Ongoing climate change will lead to warmer and drier conditions in many dryland regions, potentially affecting litter decomposition and nutrient dynamics. Climate change effects can be direct and/or indirect, for example, through changes in litter quality, yet their relative importance on litter decomposition remains unclear. 2. We conducted a manipulative study in a semi-arid shrubland to assess the effects of leaf litter quality, forecasted climate change, that is, +2.5°C warming (W), 30% rainfall reduction (RR) as well as their interaction (W + RR) to elucidate their relative effects on litter decomposition. 3. Climatic effects alone reduced decomposition of a homogeneous Control leaf litter collected from Helianthemum squamatum shrubs growing in unmanipulated plots by 23.4%, 18.1% and 29.8% in the W, RR and W + RR treatments respectively. Leaf litter quality was lower in shrubs that had been growing in warmed plots (W and W + RR), as they had lower nutrient concentrations (P, Fe) and higher C:N and C:P ratios than leaf litter produced under ambient (Control) conditions. Lignin concentration was significantly lower in litter from W + RR plots, yet when both climate and litter quality were considered simultaneously, decomposition rates were 32.0%, 26.3% and 39.9% lower in W, RR and W + RR plots compared to Controls. In addition, we found greater microbial N immobilization in leaf litter incubated within warmed (W and W + RR) than within non-warmed plots (Control and RR). Structural equation modelling showed that higher litter moisture and microbial biomass contents stimulated decomposition. Simulated climate change (W, RR and W + RR) reduced decomposition indirectly by negatively affecting litter moisture contents and litter microbial biomass. Microbial nitrogen immobilization was stimulated by the lower quality (i.e. high C:N ratios) of the leaf litter collected in shrubs from warmed plots (W and W + RR). 4. Synthesis. Our findings indicate that forecasted climate change conditions slow down C and N cycling in a dryland ecosystem, an effect that is further exacerbated by climate change-induced reductions in litter quality and related reductions in bacterial and fungal biomass in litter.

Reciprocal interaction between plant and soil (plant–soil feedback, PSF) can determine plant community structure. Understanding which traits control interspecific variation of PSF strength is crucial for plant ecology. Studies have highlighted either plant‐mediated nutrient cycling (litter‐mediated PSF) or plant–microbe interaction (microbial‐mediated PSF) as important PSF mechanisms, each attributing PSF variation to different traits. However, this separation neglects the complex indirect interactions between the two mechanisms. We developed a model coupling litter‐ and microbial‐mediated PSFs to identify the relative importance of traits in controlling PSF strength, and its dependency on the composition of root‐associated microbes (i.e. pathogens and/or mycorrhizal fungi). Results showed that although plant carbon: nitrogen (C : N) ratio and microbial nutrient acquisition traits were consistently important, the importance of litter decomposability varied. Litter decomposability was not a major PSF determinant when pathogens are present. However, its importance increased with the relative abundance of mycorrhizal fungi as nutrient released from the mycorrhizal‐enhanced litter production to the nutrient‐depleted soils result in synergistic increase of soil nutrient and mycorrhizal abundance. Data compiled from empirical studies also supported our predictions. We propose that the importance of litter decomposability depends on the composition of root‐associated microbes. Our results provide new perspectives in plant invasion and trait‐based ecology.

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.

AIM: Recent meta‐analyses have revealed that plant traits and their phylogenetic history influence decay rates of dead wood and leaf litter, but it remains unknown if decay rates of wood and litter covary over a wide range of tree species and across ecosystems. We evaluated the relationships between species‐specific wood and leaf litter decomposability, as well as between wood and leaf traits that control their respective decomposability. LOCATION: Global. METHODS: We compiled data on rates of wood and leaf litter decomposition for 324 and 635 tree species, respectively, and data on six functional traits for both organs. We used hierarchical Bayesian meta‐analysis to estimate, for the first time, species‐specific values for wood and leaf litter decomposability standardized to reference conditions (k*wₒₒd and k*ₗₑₐf) across the globe. With these data, we evaluated the relationships: (1) between wood and leaf traits, (2) between each k* and the selected traits within and across organs, and (3) between wood and leaf k*. RESULTS: Across all species k*wₒₒd and k*ₗₑₐf were positively correlated, phylogenetically clustered and correlated with plant functional traits within and across organs. k* of both organs was usually better described as a function of within‐ and cross‐organ traits, than of within‐organ traits alone. When analysed for angiosperms and gymnosperms separately, wood and leaf k* were no longer significantly correlated, but each k* was still significantly correlated to the functional traits. MAIN CONCLUSIONS: We demonstrate important relationships among wood and leaf litter decomposability as after‐life effects of traits from the living plants. These functional traits influence the decomposability of senesced tissue which could potentially lead to alterations in the rates of biogeochemical cycling, depending on the phylogenetic structure of the species pool. These results provide crucial information for a better representation of decomposition rates in dynamic global vegetation models.

1. Recent evidence indicates tight control of plant resource economics over interspecific trait variation amongst species, both within and across organs, referred to as 'plant economics spectrum' (PES). Whether and how these coordinated whole-plant economics strategies can influence the decomposition system and thereby impact on ecosystem carbon and nutrient cycling are yet an open question. More specifically, it is yet unknown whether plant functional traits have consistent afterlife effects across different plant organs. 2. To answer those questions, we conducted a common-garden decomposition experiment bringing together leaves, fine stems, coarse stems, fine roots and reproductive parts from a wide range of subarctic plant types, clades and environments. We measured all plant parts for the same (green and litter) plant economics traits and identified a whole-plant axis of carbon and nutrient economics. 3. We demonstrated that our local 'PES' has important afterlife effects on carbon turnover by driving coordinated decomposition rates of different organs across species. All organ decomposabilities were consistently controlled by the same structure-related traits (lignin, C and dry matter content) whilst nutrient-related traits (N, P, pH, phenols) had more variable influence, likely due to their contrasting functions across organs. Nevertheless, consistent shifts in elevation of parallel trait-decomposition relationships between organs indicate that other variables, potentially related to organ dimensions, configuration or chemical contents, codetermine litter decomposition rates. 4. Whilst the coordinated litter decomposabilities across species organs imply a coordinated impact of plant above-ground and below-ground litters on plant–soil feedbacks, the contrasting decomposabilities between plant parts suggest a major role for the relative inputs of organ litter as driver of soil properties and ecosystem biogeochemistry. These relationships, underpinning the afterlife effects of the PES on whole-plant litter decomposability, will provide comprehensive input of vegetation composition feedback to soil carbon turnover.

BackgroundClonal plants spread laterally by spacers between their ramets (shoot–root units); these spacers can transport and store resources. While much is known about how clonality promotes plant fitness, we know little about how different clonal plants influence ecosystem functions related to carbon, nutrient and water cycling.ApproachThe response–effect trait framework is used to formulate hypotheses about the impact of clonality on ecosystems. Central to this framework is the degree of correspondence between interspecific variation in clonal ‘response traits’ that promote plant fitness and interspecific variation in ‘effect traits’, which define a plant's potential effect on ecosystem functions. The main example presented to illustrate this concept concerns clonal traits of vascular plant species that determine their lateral extension patterns. In combination with the different degrees of decomposability of litter derived from their spacers, leaves, roots and stems, these clonal traits should determine associated spatial and temporal patterns in soil organic matter accumulation, nutrient availability and water retention.ConclusionsThis review gives some concrete pointers as to how to implement this new research agenda through a combination of (1) standardized screening of predominant species in ecosystems for clonal response traits and for effect traits related to carbon, nutrient and water cycling; (2) analysing the overlap between variation in these response traits and effect traits across species; (3) linking spatial and temporal patterns of clonal species in the field to those for soil properties related to carbon, nutrient and water stocks and dynamics; and (4) studying the effects of biotic interactions and feedbacks between resource heterogeneity and clonality. Linking these to environmental changes may help us to better understand and predict the role of clonal plants in modulating impacts of climate change and human activities on ecosystem functions.

In many terrestrial ecosystems, detritivorous soil organisms ingest large amounts of leaf litter returning most of it to the soil as faeces. Such conversion of leaf litter into faeces may stimulate decomposition by increasing the surface area available for microbial colonisation. Yet, experimental support for either the outcome or the mechanism of these conversion effects is lacking. Based on the hypothesis that the identity of plant species from which leaf litter is transformed into faeces has a critical role in how faeces decomposition proceeds, we collected faeces of the widely abundant millipede Glomeris marginata fed with leaf litter from seven distinct tree species. We compared the physical and chemical characteristics and the rates of carbon (C) and nitrogen (N) loss between litter and faeces. We found that after 100 days of exposure under controlled conditions, C loss was on average higher in faeces (40.0%) than that in litter (26.6%), with a significant increase for six of the seven species. Concurrently, N dynamics switched from a net immobilisation (7.7%) in litter to a net release (14.6%) in faeces, with a significant increase for five of the seven species. Litter conversion into faeces generally homogenised differences in physical and chemical characteristics among species. Despite such homogenisation, variability in rates of faeces C and N loss among species was similar compared to leaf litter, but correlated with a different set of traits. Specifically, faecal pellet C loss was positively related to compaction (decreased specific area and increased density of faecal pellets), and both C and N loss from faecal pellets were positively related to fragmentation (increased specific area and perimeter of particles within faecal pellets). We conclude that litter fragmentation and compaction into detritivore faecal pellets lead to substantially enhanced decomposition, with a particularly strong impact on N dynamics that changed from immobilisation to net release depending on litter species. Moreover, litter quality control on decomposition is reshuffled by litter conversion into faeces. In ecosystems with high detritivore abundance, this so far largely overlooked pathway of organic matter turnover may strongly affect ecosystem C and N cycling. A plain language summary is available for this article. Résumé Dans de nombreux écosystèmes, la macrofaune du sol ingère de grandes quantités de feuilles mortes et en restitue la majeure partie sous forme de boulettes fécales. Il est communément admis que cette transformation des feuilles mortes en boulettes stimule la décomposition en augmentant la surface exposée aux microorganismes. Cependant, les preuves expérimentales corroborant cette théorie font encore défaut. Nous avons collecté des boulettes fécales de Glomeris marginata nourris à partir de litières de sept espèces d'arbres, en faisant l'hypothèse que l'identité de l'espèce végétale dont proviennent les litières ingérées détermine la vitesse de décomposition des boulettes. Nous avons comparé les caractéristiques physiques et chimiques ainsi que le devenir du carbone et de l'azote dans les litières et les boulettes. Après 100 jours de décomposition en conditions contrôlées, les pertes en carbone ont été en moyenne plus importantes dans les boulettes (40.0%) que dans les litières (26.6%). Une tendance similaire a été observée pour l'azote, avec le passage d'une immobilisation de l'azote dans les litières (7.7%) à une perte nette dans les boulettes (14.6%). Malgré une homogénéisation des caractéristiques physiques et chimiques observée dans les boulettes, la variabilité des pertes en carbone et azote était aussi importante dans les litières que dans les boulettes. Cependant la décomposition des litières n’était pas corrélée aux mêmes traits que la décomposition des boulettes. La perte en carbone dans les boulettes était corrélée à la compaction (augmentation de la densité et diminution de la surface spécifique) et les pertes en carbone et azote dans les boulettes étaient corrélés positivement à la fragmentation (augmentation de la surface spécifique et du périmètre des particules contenues dans les boulettes). Nous concluons que la fragmentation et la compaction des litières en boulettes fécales mène à une augmentation de la décomposition, avec un impact important sur l'azote qui passe d'une immobilisation à une perte nette. De plus, cette transformation modifie la hiérarchie des traits contrôlant le processus de décomposition. Dans les écosystèmes où les détritivores sont abondants, cette transformation peut ainsi avoir d'importantes conséquences pour le recyclage du carbone et de l'azote. Plain Language Summary