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Manganese (Mn) is a redox‐active micronutrient that has been shown to accelerate plant litter decomposition; however, the effect of Mn‐promoted decomposition on soil C storage is unclear. We present a novel biogeochemical model simulating how Mn bioavailability influences soil organic C (SOC) stocks in a soil profile (<50 cm) within a temperate forest. In our model, foliar Mn increased in response to increasing soluble Mn released through Mn‐oxide (birnessite) dissolution in mineral soil layers. The ensuing Mn enrichment in leaf litter redistributed Mn to the surface forest floor layer, promoted enzymatic oxidation of lignin, and decreased SOC stocks. Total SOC loss was partially mitigated by accumulation of lignin‐oxidation products as mineral‐associated organic C. We also explored how Mn‐driven changes to C storage interacted with effects of N deposition and warming. Nitrogen enrichment inhibited Mn‐dependent lignin degradation, increasing SOC stocks and weakening their dependence on Mn bioavailability. Warming stimulated decomposition and reduced C stocks but was less effective at low Mn bioavailability. Our model results suggest that SOC stocks are sensitive to Mn bioavailability because increased plant uptake redistributes Mn to surface soils where it can enhance litter decomposition. Based on our simulations, we predict that Mn becomes limiting to litter decomposition where Mn is poorly soluble. Depletion of bioavailable Mn or other cofactors that are critical to decomposition could limit the response of organic C stocks to warming over time, but quantitative projections of the role of Mn bioavailability in regulating decomposition requires additional measurements to constrain model uncertainties. Plain Language Summary: Carbon that is removed from the atmosphere by plants and stored in soils has the potential to partially offset greenhouse gas emissions and mitigate climate change. However, predictions of soil carbon storage are challenged by limited understanding of complex interactions between biological and geochemical processes that influence how quickly organic matter decomposes in the soil. We developed a novel model that simulates how cycling of the micronutrient manganese between soils and plants impacts carbon storage in a soil profile. Although it has been demonstrated that manganese is involved in breakdown of lignin, an important component of plant litter, its effects on soil carbon storage are unknown. We also explore how effects of manganese interact with two other major global perturbations: warming and nitrogen deposition to soils. From our model results, we determine that high levels of manganese uptake by plants ultimately generate manganese‐rich surface soils that promote litter decomposition and decrease soil carbon storage. Nitrogen deposition increased carbon storage by inhibiting effects of manganese on decomposition. Decomposition increased with warming but was inhibited by low manganese bioavailability. Our model provides a novel framework for simulating how soil properties that control micronutrient availability to plants can impact soil carbon dynamics. Key Points: We developed a biogeochemical model simulating how manganese bioavailability impacts soil carbon storage in temperate forestsManganese redistribution to surface soils by plants enhanced decomposition and decreased carbon storage in the soil profileOur model predicts that low manganese bioavailability may generate nutrient limitation that decreases warming effects on decomposition [ABSTRACT FROM AUTHOR]

Summary: A large fraction of plant litter comprises recalcitrant aromatic compounds (lignin and other phenolics). Quantifying the fate of aromatic compounds is difficult, because oxidative degradation of aromatic carbon (C) is a costly but necessary endeavor for microorganisms, and we do not know when gains from the decomposition of aromatic C outweigh energetic costs.To evaluate these tradeoffs, we developed a litter decomposition model in which the aromatic C decomposition rate is optimized dynamically to maximize microbial growth for the given costs of maintaining ligninolytic activity. We tested model performance against > 200 litter decomposition datasets collected from published literature and assessed the effects of climate and litter chemistry on litter decomposition.The model predicted a time‐varying ligninolytic oxidation rate, which was used to calculate the lag time before the decomposition of aromatic C is initiated. Warmer conditions increased decomposition rates, shortened the lag time of aromatic C oxidation, and improved microbial C‐use efficiency by decreasing the costs of oxidation. Moreover, a higher initial content of aromatic C promoted an earlier start of aromatic C decomposition under any climate.With this contribution, we highlight the application of eco‐evolutionary approaches based on optimized microbial life strategies as an alternative parametrization scheme for litter decomposition models. See also the Commentary on this article by Shao & Sulman, 243: 825–827. [ABSTRACT FROM AUTHOR]

The rewetting of long-term drained peatlands leads to the development of eutrophic shallow lakes, gradually inhabited by reed communities. These shallow lakes are characterized by significant nutrient and methane emissions. To comprehend the fate of organic compounds from decaying Phragmites australis litter in water and anaerobic soil layers, we conducted a 1.6-year decomposition experiment. The experiment employed bulk and lignin-derived phenol analysis, as well as Fourier-transform infrared spectroscopy. As anticipated, the highest level of decomposition was observed in the surface water body of the shallow lake, while the non-rooted degraded peat exhibited the lowest decay. The bulk mass loss of plant litter decreased with depth from 55 to 27% across the four decomposition environments. Analysis using infrared spectroscopy indicated that the decrease in mass loss was primarily driven by the breakdown of carbohydrates, which constitute a significant portion of plant litter. Interestingly, litter in the rooted degraded peat layer exhibited the highest degree of lignin decay. Furthermore, the study revealed a preferential loss of vanillin phenols and an accumulation of p-hydroxyl phenols. These findings suggest that the increased methane emissions in rewetted fens may be partially attributed to the demethoxylation of vanillin phenols and the subsequent formation of p-hydroxyl phenols. In conclusion, this study provides valuable insights into anaerobic lignin decomposition of plant litter and sheds light on potential mechanisms underlying elevated methane emissions in rewetted peatlands. Furthermore, the study's findings hold significant implications for both carbon cycling and sequestration within these ecosystems, thereby stimulating further research into the microbial community and its extended effects. [ABSTRACT FROM AUTHOR]

Purpose: The decomposition of litter and nutrient cycling in terrestrial ecosystems are significantly influenced by ultraviolet-B (UV-B) radiation. The direction and magnitude of this effect are largely regulated by the dry and wet conditions of the environment. The impact of UV-B radiation on the decomposition process of different litter types in arid desert regions under future precipitation changes remains poorly understood. Methods: A field experiment was conducted to investigate the impact of precipitation changes (natural precipitation, a 30% increase in precipitation, and a 30% reduction in precipitation) on the litter decomposition of Reaumuria soongarica and Salsola passerina under both natural and reduced UV-B radiation conditions. Results: The reduction in UV-B radiation significantly decreased mass loss and nutrient release. However, these adverse effects were counteracted by increased precipitation, with an average value of 4.17% for mass loss and 34.35% for nutrient release. Conversely, decreased precipitation intensified these negative effects. The ameliorating effects of increased precipitation were associated with improved soil properties, including higher soil moisture and lower soil temperature, as well as elevated soil enzyme activities such as higher CBH and POD. Moreover, these mitigating effects on mass loss and nutrient release were more pronounced in S. passerina litter than in R. soongarica. A structural equation model revealed that precipitation and UV-B radiation indirectly influenced mass loss by altering soil properties (ST and SM) and soil enzyme activities (CBH and POD). Conclusion: Our results suggest that changes in precipitation will modify the effects of reduced UV-B radiation on litter decomposition and nutrient cycling of various plant litters, particularly in plants with lower initial nitrogen content, under climate change. [ABSTRACT FROM AUTHOR]

Fire-derived charcoal (charcoal) is a stable byproduct of forest fires, which accumulates in the litter layer and soils of boreal forests. Therefore, the decomposition of litter and roots as one of the key processes in the carbon cycle in the soils of northern forests proceeds almost everywhere in the presence of charcoal. To date, the data on the influence of charcoal on the organic material decomposition in boreal forests are extremely scarce and most of them do not consider the cold period, which lasts on the average half a year in this zone. The goal of this work is to determine the seasonal influence of charcoal on the decomposition of plant litter of different qualities (larch needles, birch leaves, grasses, and mixtures of these litter types) on the soil surface and the roots of the same types in the soil. A field litterbag experiment demonstrates that charcoal accelerates the decomposition of litter in a species-specific manner. Charcoal accelerates the mass loss of recalcitrant aboveground litter (needles) and all types of roots during the cold season. As for the warm season, charcoal accelerates the decomposition of only needles and has no effect on the roots. Thus, our study shows a greater influence of charcoal on the subsoil decomposition especially in the cold season. The seasonal influence of charcoal is demonstrated for the first time and should be taken into account as an important factor of humus formation and carbon dynamics in the soils of boreal forests. [ABSTRACT FROM AUTHOR]

The effect of mixing litter on decomposition has received considerable attention in terrestrial and aquatic (but rarely in both) ecosystems, with a striking lack of consensus in the obtained results. We studied the decomposition of a mixture of poplar and alder in three terrestrial: aquatic exposures to determine (1) if the effect of mixing litter on mass loss, associated decomposers (fungal biomass, sporulation rates, and richness), and detritivores (abundance, biomass, and richness of invertebrate shredders) differs between the stream (fully aquatic exposure) and when litter is exposed to a period of terrestrial exposure prior to immersion and (2) the effect of the mixture across exposure scenarios. The effect of the mixture was additive on mass loss and synergistic on decomposers and detritivores across exposure scenarios. Within scenarios, mass loss and decomposers showed synergistic effects only in the fully aquatic exposure, detritivores showed synergistic effects only when the period of terrestrial was shorter than the period of aquatic exposure, and when the period of terrestrial was equal to the period of aquatic exposure the effect of the mixture was additive on mass loss, decomposers, and detritivores. The species‐specific effects also differed among exposure scenarios. Alder affected poplar only when there was a period of terrestrial exposure, with increased sporulation rates and fungal richness in exposure 25:75, and increased mass loss in exposure 50:50. Poplar affected alder only under fully aquatic exposure, with increased mass loss. In conclusion, the synergistic effects of the mixture changed with a period of terrestrial exposure prior to immersion. These results provide a cross‐boundary perspective on the effect of mixing litter, showing a legacy effect of exposure to terrestrial decomposition on the fate of plant litter in aquatic ecosystems and highlighting the importance of also assessing the effect of mixing litter on the associated biota and not only on mass loss. [ABSTRACT FROM AUTHOR]

This document is a reply to a study published in Nature Communications that reported a decrease in global soil microbial biomass carbon (MBC) due to increasing temperatures. However, the authors of this reply conducted field experiments and found no consistent reductions in MBC in response to soil warming. They suggest that the decline predicted by the original study may be a result of spatial gradients rather than actual temporal changes. Further research is needed to understand the potential effects of climate change on MBC. The study was funded by the Chinese Academy of Sciences, the Second Tibetan Plateau Scientific Expedition and Research Program, and the National Natural Science Foundation of China. [Extracted from the article]

Litter decomposition is a key process of the carbon cycle in terrestrial and aquatic ecosystems. The dominant conceptual model of litter decomposition assumes that environmental conditions, litter traits, and decomposer composition control litter decomposition in a decreasing order, yet whether this hierarchical model applies to both invasive and native plant species is unknown. Here, by comparing a widespread invasive plant and its native counterpart in Chinese coastal saltmarshes, we aimed to examine whether the hierarchy of factors controlling litter decomposition varies with plant species in the face of plant invasions. Leaf litter of invasive Spartina alterniflora and native Phragmites australis was collected across an 18° latitudinal range to capture wide variation in litter traits. These leaf litter samples were transported to three saltmarsh sites of different latitudes and were incubated in litterbags varying in mesh size (0.1, 2, and 5 mm) to manipulate decomposer composition. After 90‐day incubation, we found a parallel latitudinal pattern in leaf litter decomposition rate (k) between S. alterniflora and P. australis regardless of saltmarsh site and mesh size. Nonetheless, the k value of S. alterniflora was 2.2‐fold higher than that of P. australis. Moreover, there was a shift in the hierarchy of factors controlling k values between S. alterniflora and P. australis: environmental conditions (climate and soil) dominated other factors in P. australis, whereas litter traits contributed more than environmental conditions in S. alterniflora. Overall, our findings show that leaf litter decomposition and its dominant controlling factors across broad geographical ranges can vary with plant invasions, having important implications for managing invasive plants in the context of conserving coastal blue carbon. [ABSTRACT FROM AUTHOR]

Wetland is a transitional area where terrestrial ecosystems and aquatic ecosystems interact and influence each other, and it is an important ecosystem on the Earth's surface. Due to the special characteristics of wetland ecology, the decomposition of wetland plant litter is slightly different from litter in forests, grasslands, and meadows and other traditional areas. The role of litter mineralization in the wetland ecological C cycle and the functional role of plant litter have been neglected. This study analyzes the decomposition mechanism and decomposition model of wetland litter material and focuses on the effects of the decomposition process of wetland litter material on the structure of the soil fauna community, decomposition of soil organic matter, sediment properties, and the dynamic changes in the C cycle of the biological system by combining domestic and international studies from recent years. Finally, we propose that the direction of future research on wetland litter decomposition should be to reveal the mechanism of wetland biodiversity and ecology, as well as the ecological correlation between aboveground and belowground biodiversity, with a view to providing a decision-making basis for wetland phytoremediation and wetland wastewater treatment. [ABSTRACT FROM AUTHOR]

Climate change drives a northward shift of biomes in high‐latitude regions. This might have consequences on the decomposition of plant litter entering the soil, including its lignin component, which is one of the most abundant components of vascular plants. In order to elucidate the combined effect of climate and soil characteristics on the decomposition pattern of lignin, we investigated lignin contents and its degree of oxidative decomposition within soil profiles along a climosequence in western Siberia. Soil samples were collected from organic topsoil to mineral subsoil at six sites along a 1500‐km latitudinal transect, stretching from tundra, through taiga and forest steppe to typical steppe. The stage of lignin degradation, as mirrored by decreasing organic carbon‐normalized lignin contents and increasing oxidative alteration of the remnant lignin (acid‐to‐aldehyde ratios of vanillyl‐ and syringyl‐units [(Ac/Al)V and (Ac/Al)S]) within soil horizons, increased from tundra to forest steppe and then decreased to the steppe. Principal component analysis, involving also climatic conditions such as mean annual temperature and aridity index, showed that the different states of lignin degradation between horizons related well to the activity of phenoloxidases and peroxidases, enzymes involved in lignin depolymerization that are produced primarily by fungi and less importantly by bacteria. The low microbial lignin decomposition in the tundra was likely due to low temperature and high soil moisture, which do not favour the fungi. Increasing temperature and decreasing soil moisture, facilitating a higher abundance of fungi, led to increased fungal lignin decomposition towards the forest‐steppe biome, while drought and high pH might be responsible for the reduced lignin decomposition in the steppe. We infer that a shift of biomes to the north, driven by climate change, might promote lignin decomposition in the northern parts, whereas in the south a further retardation might be likely. [ABSTRACT FROM AUTHOR]

Background and aims: Dioecy may subject females and males to contrasting selective pressures, leading to differences in adaptive traits associated with resource allocation and ecophysiology across sex. Such differences may then exert carry-over effects on the surrounding ecosystem. However, effect of different sex combinations over ecosystem biogeochemical cycles, via organic matter decomposition, has not yet been addressed. Here, we used different combinations of female and male Populus cathayana to elucidate the carry-over effects of dioecy on organic matter decomposition. Methods: 900 saplings were grown in field plots in either single-sex or mixed-sex treatments. Soil organic matter decomposition rates were estimated using the teabag index, and measurements of soil microbial respiration in vitro, and characterization of the rhizosphere microbial community, were done. Results: Different sex combinations variedly influenced plant growth, assimilation rates, and soil processes under field conditions. showed highest shoot length, stem diameter, photosynthetic rates, soil microbial respiration rates, litter decomposition rate, the extent of litter stabilization, and soil microbial structure were highest under the FM treatment. Bacterial abundance and diversity were highest in FF plots, while the highest abundance and diversity of classified fungi occurred in MM plots. Our piecewise structural equation model analysis results further confirmed that sex was a significant driver of photosynthesis, shoot dry weight, specific root length, microbe abundance and diversity, soil nutrient status, soil respiration, and organic matter decomposition. Conclusion: Our results indicate that sex plays a significant role in soil biogeochemical processes and provides novel insights relevant to dioecious plantations and biogeochemical modeling. [ABSTRACT FROM AUTHOR]

The organic carbon (C) in soil is mainly from plants via litter decomposition. Here, we developed a new litter decomposition submodel incorporating the microbial biomass effect on the decomposition rate based on the Michaelis‐Menten kinetics. This new submodel was coupled with the existing plant and soil submodels to simulate C cycling in natural ecosystems in the continental United States. The C transfer efficiency (EFF), defined as the percentage of C transferred to the next layer in the plant‐litter‐soil continuum, was quantified in different types of natural ecosystems. We estimated that on average 48.1% of gross primary productivity (GPP) was transferred from plant to litter and 15.1% of litterfall was transferred from litter to soil, meaning that the C that finally enters soil was on average approximately 7.3% of GPP. Ecosystems with a drier climate and lower GPP had higher EFF from plant to soil. The EFF concept we proposed provides an empirical proxy for diagnosing ecosystem C cycling and a framework for projecting the change of C fluxes and C pool sizes in response to climate change. If C transfer can represent energy transfer analogous to Lindeman Efficiency, our results suggest a pattern of resource and energy transfer in nature: higher resource or energy availability usually means lower resource or energy transfer efficiency. Plain Language Summary: Carbon sequestration by ecosystems is important for mitigating global warming. During the transfer of carbon from atmospheric CO2 to plants, then to litter, and then to soil, carbon is continuously lost to the atmosphere via CO2. Here, we adopted the idea of Lindeman Efficiency to express this efficiency of carbon transfer between different layers in the plant‐litter‐soil systems in the continental US. We found that ecosystems with higher productivity have lower carbon transfer efficiency, indicating the tradeoff between the two. Therefore, it is hard to find an ecosystem with both high productivity and high carbon transfer efficiency to soil for carbon sequestration. Our attempt to understand carbon transfer efficiency provides an intuitive proxy of C cycling and a framework for future research on ecosystem carbon sequestration and global warming. Key Points: The transfer of carbon from plant to litter than to soil is more efficient in ecosystems with higher productivityOur litter submodel can directly simulate carbon input fluxes into soil, has intermediate complexity, and shows good performanceThe C transfer efficiency concept we proposed provides an empirical proxy for diagnosing ecosystem C cycling [ABSTRACT FROM AUTHOR]

Although microbial communities play an important role in explaining plant litter decomposition rates, whether and how litter chemistry may alter catabolic capacities of soil microbial communities remains poorly studied.During a 1‐year litter decomposition experiment of 12 herbaceous species with contrasting litter chemistry, we examined the effect of plant litter type (roots vs. leaves) and litter chemical traits on the resulting capacity of soil microbial communities to degrade a wide range of carbon substrates of variable complexity (MicroResp™ method).Litter chemistry impacted both the total catabolic activity as well as specific catabolic capacities of microbial communities. In the early stages of litter decomposition total catabolic activity was mainly influenced by the amount of C and N in litter leachates, and litter N, P and Mg, then, later, by lignin concentrations. Some specific catabolic capacities could also be related to litter initial chemistry. Overall, litter trait effects on soil microbial communities decreased over time and the relative importance of traits shifted during the decomposition process.Our results highlight that litter chemistry is a strong driver of catabolic capacities of microbial decomposers and, while its effect fades with time, it remains substantial throughout the litter decomposition process. These long‐lasting effects of litter chemistry suggest a persistent control on microbial catabolic capacities in ecosystems with recurrent litter production. Soil microbial catabolic activities were driven by broadly the same chemical traits across leaf and root litters.Synthesis. Such long‐lasting effects of litter chemistry on catabolic capacities of microbial communities may represent a substantial indirect driver of the decomposition process. Disentangling the relative importance of this overlooked effect of litter chemistry on decomposition represents the next challenge. We argue that such research line should open ground‐breaking perspectives for reconsidering our current understanding of the mechanistic links between litter traits and decomposition rate. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Background: Plants can directly affect litter decomposition by producing litter materials of different qualities. However, whether living plants have indirect effects on litter decomposition by affecting changes in forest microenvironments is presently unclear in plantation forests. Methods: We addressed this issue by studying the decomposition of the leaf litter and fine roots of Chinese fir [Cunninghamia lanceolata (Lamb.) Hook.], a timber species widely planted in China, in 113 non-neighboring quadrats of varying basal area of the dominant plant species (i.e., Chinese fir) and distinct basal areas and species richness of regenerated woody plants (i.e., species other than Chinese fir) in a subtropical Chinese fir forest. Results: Our results showed that fine roots decomposed significantly more rapidly than leaf litter possibly because fine roots were easier access to mineralized nutrients and microbes compared with leaf litter. Further analyses showed that leaf litter and fine root decomposition rates were significantly controlled by the plant community attributes. The decomposition of both leaf litter and fine roots was mainly controlled by woody species regenerated during stand development rather than by Chinese fir. Specifically, leaf litter and fine root decomposition rates decreased with increasing basal area of regenerated woody plants, possibly due to nutrient competition and/or reduced photodegradation. Conclusions: This study provides empirical evidence that woody species regenerated during stand development play a certain role in determining litter decomposition rates through plant-soil interactions in Chinese fir plantations. Regenerated woody plants should be considered in future studies on soil carbon and nutrient cycling in plantation forest. [ABSTRACT FROM AUTHOR]

Plant litter decomposition is a major source of soil organic carbon (OC); however, the quantitative differences in litter decomposition and carbon (C) release between herbaceous and woody plants are not well understood. In this study, we investigated the litter decomposition processes of the leaves of Carex brevicuspis (herbaceous plant) and the leaves and branches of Salix triandroides (woody plant) at soil depths of 0 and 5 cm from March–November in Dongting Lake. The litter of C. brevicuspis had a lower C concentration and C to nitrogen (N) ratio compared to that of S. triandroides. The decomposition and C release rates were higher in the litter of C. brevicuspis than those in the litter of S. triandroides. The higher release rate of OC from the decomposition of the litter of C. brevicuspis compared to that of S. triandroides contributed to the higher soil concentration of OC in the C. brevicuspis community compared to that of S. triandroides. Litter decomposition and release rates of OC changed over time and were higher during the non-flood period than during the flood period. Additionally, the rate of OC release from litter decomposition in the two investigated plants was correlated with the richness of Firmicutes, Bacteroidetes, Cyanobacteria, and Verrucomicrobia. Our results reveal that the differences in OC released during the decomposition of herbaceous and woody litters are related to the litter properties, nutrient concentrations in soil, flood period, and specific bacterial communities. This study reveals that the herbaceous plant C. brevicuspis has a stronger ability to improve soil OC than the woody plant S. triandroides. [ABSTRACT FROM AUTHOR]

Soil organic matter (SOM) is comprised of a diverse array of reactive carbon molecules, including hydrophilic and hydrophobic compounds, that impact rates of SOM formation and persistence. Despite clear importance to ecosystem science, little is known about broad-scale controls on SOM diversity and variability in soil. Here, we show that microbial decomposition drives significant variability in the molecular richness and diversity of SOM between soil horizons and across a continental-scale gradient in climate and ecosystem type (arid shrubs, coniferous, deciduous, and mixed forests, grasslands, and tundra sedges). The molecular dissimilarity of SOM was strongly influenced by ecosystem type (hydrophilic compounds: 17%, P < 0.001; hydrophobic compounds: 10%P < 0.001) and soil horizon (hydrophilic compounds: 17%, P < 0.001; hydrophobic compounds: 21%, P < 0.001), as assessed using metabolomic analysis of hydrophilic and hydrophobic metabolites. While the proportion of shared molecular features was significantly higher in the litter layer than subsoil C horizons across ecosystems (12 times and 4 times higher for hydrophilic and hydrophobic compounds, respectively), the proportion of site-specific molecular features nearly doubled from the litter layer to the subsoil horizon, suggesting greater differentiation of compounds after microbial decomposition within each ecosystem. Together, these results suggest that microbial decomposition of plant litter leads to a decrease in SOM a-molecular diversity, yet an increase in β-molecular diversity across ecosystems. The degree of microbial degradation, determined by the position in the soil profile, exerts a greater control on SOM molecular diversity than environmental factors, such as soil texture, moisture, and ecosystem type. [ABSTRACT FROM AUTHOR]

We believe that correcting for leaching in (terrestrial) litterbags studies such as the Tea Bag Index will result in more uncertainties than it resolves. That is, although shorter durations of leaching experiments increase the likelihood that they only quantify primary leaching, they result in a higher probability of missing events that contribute to primary leaching. Future litter decomposition and leaching studies will improve by careful interpretation of solid experiments, by being transparent about definitions used and by explaining the way in which leaching corrections were applied (if any). [Extracted from the article]

Aims: Soil fauna is one of the major drivers of plant litter decomposition. This study aims to assess how soil fauna density and diversity may affect litter decomposition. Also, we assessed whether faunal communities inside the litterbags that are used to control the access of faunal groups or communities in ambient soils are better for predicting their effects on litter decomposition, given that soil fauna frequently move into and out of such litterbags. Methods: To answer this question, we synthesized 5336 observations extracted from 46 publications to assess the effects of soil fauna communities, their density and diversity on the rate of litter decomposition (k) and litter mass loss. Results: Results showed that (1) the presence of soil fauna significantly increased k by an average of 33.0% and that the effects were mainly controlled by initial litter concentrations of phosphorus and magnesium, (2) the density and diversity of soil fauna in litterbags significantly affected k and/or mass loss, but ambient communities had limited effects, and (3) the effects of soil fauna in litterbags on k were most significant during the early stages of decomposition (0 − 30% mass loss). Conclusions: Our study clearly showed that litterbag communities were better for predicting the effects of soil fauna on litter decomposition, and that their effects were most significant during the early stages of decomposition. These results improve our ability to estimate the contribution of soil fauna in liter decomposition and the associated carbon and nutrient cycling. [ABSTRACT FROM AUTHOR]

Plant litter decomposition is critical for the carbon (C) balance and nutrient turnover in terrestrial ecosystems, and is sensitive to the ongoing anthropogenic biologically nitrogen (N) input. Previous studies evaluating the N effect on litter decomposition relied mostly on short-term experiments (<2 years), which may mask the real N effect on litter decomposition. Therefore, long-lasting experiments are imperative for the overall evaluation of the litter decomposition dynamics under N enrichment. We conducted a relative long-term (4-year) N-addition experiment with N levels ranging from 0 to 50 g N m−2 yr−1 to identify the potential abiotic and biotic factors in regulating the decomposition process of litterfall from the dominant species Leymus chinensis. The results showed a consistent decrease of decomposition rate with increasing N-addition rates, providing strong evidence in support of the inhibitory effect of N addition on decomposition. The N-induced alterations in soil environment (acidification and nutrient stoichiometry), microbial activity (microbial biomass and enzyme activity), changes of litter quality (residual lignin and nutrient content) and plant community (aboveground productivity and species richness) jointly contributed to the lowered decomposition. During the whole decomposition process, the changes of litter quality, including accumulation of lignin and the concentrations of nutrient, were mainly driven by the soil and microbial activity in this N-enriched environment. The findings help clarify how increasing N input rates affect long-term litter decomposition, and advance the mechanistic understanding of the linkages between ecosystem N enrichment and terrestrial C cycling. [ABSTRACT FROM AUTHOR]

Plant litter decomposition figures importantly in the cycling of C and N pools in terrestrial ecosystems. We investigated how C and N fluxes changed during the decomposition of leguminous and non-leguminous leaf litters, and how these processes responded to different precipitation regimes. We used the dual-isotope tracing method to investigate differences in leaf and soil C and N, along with δ13C and δ15N, in the soil of the Loess Plateau in China. The δ15N and δ13C values were 3604‰ and 56‰ for Robinia pseudoacacia (Leguminosae) and 8115‰ and 452‰ for Populus tomentosa (Salicaceae) leaf litters. Through decomposition, δ13C decreased in all litters, and δ15N in the leguminous litter increased while it decreased in the non-leguminous litter. In the surface soil, the fraction of litter-derived N (14%) from the leguminous litter was significantly higher than that of the non-leguminous litter after 16 months. The C and N concentrations of both litters and soil always had a positive correlation during decomposition, and the responses of N to C changes in soil were reduced by the litter cover. Increased precipitation enhanced the litters' C and N correlation. The 600 mm precipitation treatment most benefited litter C's transformation to SOC, and drought conditions promoted the transformation of legume litter N to soil TN, but inhibited non-legume litter N. In the soil and both litters, C and N changes always had a positive correlation. After 16 months, the proportion of soil N from legumes was higher than that from non-legumes. Reduced precipitation could promote leguminous N in soil. Our results provide a scientific basis for accurately predicting the C and N cycles in terrestrial ecosystems. [ABSTRACT FROM AUTHOR]

Plant litter decomposition plays a crucial role in the flow of nutrients and energy in ecosystems. However, the mechanism of bacterial communities regulating litter decomposition under climate warming in temperate wetlands remains largely unknown. The objective of this study was to determine the influences of temperature on decomposition and the bacterial regulatory mechanism under climate warming in temperate wetlands. In this study, we conducted a 1.5-year litter decomposition warming experiment using dominant plant species in the temperate lake wetlands of the North China Plain. Our results showed that the decomposition rate (K) had a significant positive correlation with temperature, and the non-additive effects of litter decomposition could be clearly observed in the mixtures of Phragmites australis and Typha angustata, especially under warming conditions. Among the three types of litter, Phragmites australis had the highest temperature sensitivity (2.75), which meant that it would be most affected by climate change in the future. The concentrations of C and N showed a significant positive correlation with the decomposition rate and were mainly driven by Proteobacteria and Firmicutes, while the concentration of lignin and the lignin:N ratio had a highly significant negative correlation with the decomposition rate and were mainly driven by Bacteroidota and Actinobacteriota. Furthermore, the bacterial cooccurrence network revealed that the abundance of Firmicutes and Desulfobacterota increased significantly, and positive edges accounted for 67.81% ~ 71.14% under warming conditions. The bacterial networks of litter decomposition were mainly composed of symbiotic relationships, and warming was helpful for improving the positive correlations and symbiotic relationships of bacterial flora and sped up the litter decomposition process. These results will be helpful to further understand the mechanism of bacterial communities regulating litter decomposition under climate warming in temperate wetland ecosystems. [ABSTRACT FROM AUTHOR]

Plant litter decomposition stands at the intersection between carbon (C) loss and sequestration in terrestrial ecosystems. During this process organic matter experiences chemical and physical transformations that affect decomposition rates of distinct components with different transformation fates. However, most decomposition studies only fit one-pool models that consider organic matter in litter as a single homogenous pool and do not incorporate the dynamics of litter transformations and transfers into their framework. As an alternative, compartmental dynamical systems are sets of differential equations that serve to represent both the heterogeneity in decomposition rates of organic matter and the transformations it can undergo. This is achieved by including parameters for the initial proportion of mass in each compartment, their respective decomposition rates, and mass transfer coefficients between compartments. The number of compartments as well as their interactions, in turn, determine the model structure. For instance, a one-pool model can be considered a compartmental model with only one compartment. Models with two or more parameters, in turn, can have different structures, such as a parallel one if each compartment decomposes independently or in a series if there is mass transfer from one compartment to another. However because of these differences in model parameters, comparisons in model performance can be complicated. In this context we introduce the concept of transit time, a random variable defined as the age distribution of particles when they are released from a system, which can be used to compare models with different structures. In this study, we first asked what model structures are more appropriate to represent decomposition from a publicly available database of decomposition studies in arid lands: aridec. For this purpose, we fit one- and two-pool decomposition models with parallel and series structures, compared their performance using the bias-corrected Akaike information criterion (AICc) and used model averaging as a multi-model inference approach. We then asked what the potential ranges of the median transit times of litter mass in arid lands are and what their relationships with environmental variables are. Hence, we calculated a median transit time for those models and explored patterns in the data with respect to mean annual temperature and precipitation, solar radiation, and the global aridity index. The median transit time was 1.9 years for the one- and two-pool models with a parallel structure and 5 years for the two-pool series model. The information in our datasets supported all three models in a relatively similar way and thus our decision to use a multi-model inference approach. After model averaging, the median transit time had values of around 3 years for all datasets. Exploring patterns of transit time in relation to environmental variables yielded weak correlation coefficients, except for mean annual temperature, which was moderate and negative. Overall, our analysis suggests that current and historical litter decomposition studies often do not contain information on how litter quality changes over time or do not last long enough for litter to entirely decompose. This makes fitting accurate mechanistic models very difficult. Nevertheless, the multi-model inference framework proposed here can help to reconcile theoretical expectations with the information content from field studies and can further help to design field experiments that better represent the complexity of the litter decomposition process. [ABSTRACT FROM AUTHOR]

Understanding how genetic differences among soil microorganisms regulate spatial patterns in litter decay remains a persistent challenge in ecology. Despite fine root litter accounting for ~50% of total litter production in forest ecosystems, far less is known about the microbial decay of fine roots relative to aboveground litter. Here, we evaluated whether fine root decay occurred more rapidly where fungal communities have a greater genetic potential for litter decay. Additionally, we tested if linkages between decay and fungal genes can be adequately captured by delineating saprotrophic and ectomycorrhizal fungal functional groups based on whether they have genes encoding certain ligninolytic class II peroxidase enzymes, which oxidize lignin and polyphenolic compounds. To address these ideas, we used a litterbag study paired with fungal DNA barcoding to characterize fine root decay rates and fungal community composition at the landscape scale in northern temperate forests, and we estimated the genetic potential of fungal communities for litter decay using publicly available genomes. Fine root decay occurred more rapidly where fungal communities had a greater genetic potential for decay, especially of cellulose and hemicellulose. Fine root decay was positively correlated with ligninolytic saprotrophic fungi and negatively correlated with ECM fungi with ligninolytic peroxidases, likely because these saprotrophic and ectomycorrhizal functional groups had the highest and lowest genetic potentials for plant cell wall degradation, respectively. These fungal variables overwhelmed direct environmental controls, suggesting fungal community composition and genetic variation are primary controls over fine root decay in temperate forests at regional scales. [ABSTRACT FROM AUTHOR]

The decomposition of plant litter and animal dung is the key processes of nutrient cycling and has been studied in a wide range of grassland ecosystems. However, most studies focus on the separate processes of either plant litter or animal dung decomposition, while the interactions between these two processes, which occur in grazed grassland ecosystems, are rarely studied. We conducted an experiment in a semi-arid grassland in Central Inner Mongolia, to examine the mass loss rates and chemical composition changes of two plant litter species and three herbivore dung types separately or in combination over a 2-year period. Twenty litterbag treatments were used to represent 2 treatments of plant litter only, 6 treatments of herbivore dung only at two addition levels, and 12 treatments of litter and dung combinations. We found that horse dung had the biggest mass loss rate, followed by cattle dung and sheep dung, either separately or mixed with plant litter. Dung addition promoted the mass loss, nitrogen release and fiber fraction (hemicellulose, cellulose and lignin) loss of plant litter, and the promotion was strongest for cattle dung, weakest for sheep dung, and stronger at high dung addition levels and in the early stages. However, the effect of litter addition on dung decomposition, a negative effect, was significant only when the dung proportion was low in the litter and dung mixture (that is, in the treatment of 10 g litter + 6 g dung). Furthermore, a significant positive non-additive effect of mixing litter and dung on their total mass loss was detected for the mixture at a litter:dung ratio of 10:6, the ratio in the major grazing area of the grassland. Our findings suggest that mixture of herbivore dung with plant litter, as in actual grassland ecosystems, promotes litter decomposition, and the composition of the litter and dung in mixture, though it may inhibit dung decomposition, due to the changes in chemical stoichiometry of decomposing materials and biophysical microenvironment by the mixing. It is necessary to incorporate the non-additive effect of litter and dung mixture in modeling carbon and nutrient cycling of grassland ecosystems. [ABSTRACT FROM AUTHOR]

Ongoing global warming is expected to alter temperature-dependent processes. Nevertheless, how co-occurring local drivers will influence temperature sensitivity of plant litter decomposition in lotic ecosystems remains uncertain. Here, we examined the temperature sensitivity of microbial-mediated decomposition, microbial respiration, fungal biomass and leaf nutrients of two plant species varying in litter quality. We also assessed whether the type of microbial community and stream water characteristics influence such responses to temperature. We incubated alder (Alnus glutinosa) and eucalypt (Eucalyptus globulus) litter discs in three streams differing in autumn–winter water temperature (range 4.6–8.9 °C). Simultaneously, in laboratory microcosms, litter discs microbially conditioned in these streams were incubated at 5, 10 and 15 °C with water from the conditioning stream and with a water control from an additional stream. Both in the field and in the laboratory, higher temperatures enhanced litter decomposition rates, except for eucalypt in the field. Leaf quality modified the response of decomposition to temperature in the field, with eucalypt leaf litter showing a lower increase, whereas it did not in the laboratory. The origin of microbial community only affected the decomposition rates in the laboratory, but it did not modify the response to temperature. Water quality only defined the phosphorus content of the leaf litter or the fungal biomass, but it did not modify the response to temperature. Our results suggest that the acceleration in decomposition by global warming will be shaped by local factors, mainly by leaf litter quality, in headwater streams. [ABSTRACT FROM AUTHOR]

Copyright of Acta Prataculturae Sinica is the property of Acta Prataculturae Sinica Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Phyllosphere microbes are essential in the mediation of plant–soil biogeochemical recycling during the decomposition of plant litter in wetland ecosystems. However, there are few studies into microbial community succession in phyllosphere microbial communities in wetlands, and their functional attributes across a full period of wetland plant litter decomposition remain unclear. Here, we collected leaf samples of Typha latifolia var. orientalis (C. Presl.) Rohrb., an emergent wetland plant, during various stages of decomposition (growing, standing, lodging, and submerging stages) to investigate fungal and bacterial assemblage succession in the phyllosphere. We then parsed these assemblages into specific fungal trophic modes and bacterial phenotypes. Over the litter decomposition period, both fungal and bacterial assemblages underwent distinct succession, with generally increasing alpha diversity, and the proportion of litter microbes originating from sediments increased with decomposition. Saprotrophic and pathotrophic fungi dominated the fungal assemblage in the early stages of decomposition, but their dominance was replaced by undefined fungi as decomposition progressed. Relative abundances of both pathotrophic fungi and potentially pathogenic bacteria increased from the growing to the standing stage, implying that there was a turning point in assemblage composition shortly after plant leaf death. Gram-positive and gram-negative bacteria had opposite trends in their relative abundances over successive decomposition stages. When plant litter entered the water, bacteria tolerant of oxidative stress gradually decreased in abundance, but anaerobic bacteria abundance increased. We also aimed to determine the relationships between predicted microbial functional traits and leaf litter physicochemical attributes. Lignin and N content were the predominant predictors of decomposer fungal trophic modes and bacterial phenotypes. These findings provide evidence that the complex litter decomposition seen in wetlands is accompanied by a dynamic cross-kingdom succession of phyllospheric microbial communities, coupled with distinct changes in the phenotypes of the microbes present. Insights into phyllospheric microbial functional traits have implications for better elucidating the plant litter cycle for wetland plants. [ABSTRACT FROM AUTHOR]

Photodegradation is an important mechanism that affects carbon and nutrient cycling; a significant amount of data has been reported previously. The present review includes the effect of a wider spectrum of solar radiation (sun light, UV, and visible light) on plant litter decay in terrestrial ecosystems. Although the positive effect of photodegradation on decomposition is most common, a substantial number of studies reports contrasting results. Litter from 148 plant species, from 41 families, have been used in photodegradation studies, representing functional groups of trees (33%), graminoids (30%), shrubs (23%), forbs (11%), and peat (1%). Although the majority of studies focused on mass loss, a growing number focuses on nutrient release. Positive effects on mass loss are most common across different climate regions and laboratory studies, whereas "positive" influence and "no effect" on nitrogen and lignin release are equally common in temperate and sub-tropical environments. This may potentially be due to other decomposition processes which increase in relevance with increasing moisture and can facilitate microbial activity, leaching, and fractioning by soil fauna. In addition to climate region, initial litter quality influences photodegradation. Field-based and laboratory experiments frequently obtain contrasting results, suggesting that the mechanisms controlling the responses are unclear and might be dependent on several interactions, and/or the differences in experimental approaches (such as UV filters), or coverage by particles. Future research should focus on interactions between different factors, and on conducting experiments that test specific relationships such as the potential interaction between photodegradation, soil moisture, microbial communities, soil fauna, and their effects on litter decomposition (both mass loss and nutrient release). Furthermore, the topic would benefit from international studies applying the same experimental approach, as has successfully been conducted in other fields. [ABSTRACT FROM AUTHOR]

The extramatrical mycelium of ectomycorrhizal fungi (EMF) is an important source of soil carbon and nitrogen. While the importance of recalcitrant compounds in the fungal cell wall has been explored earlier, the contribution of highly abundant but labile components, like glucans, and the role of their temporal dynamics during decomposition remains unknown. For the first time, we examined how the concentration of three main fungal cell wall components (chitin, melanin, glucans) in EMF necromass are related to necromass decomposition, over a period of 6 weeks. Although the initial concentrations of the three components were not good predictors of necromass loss, we found species–specific trends of chitin and glucans loss over time. The chitin concentration during decomposition was tightly linked to the weekly necromass degradation, with trends of chitin loss being dissimilar across fungal species. Chitin concentration was positively correlated with the mass loss in the first week, but in the remaining 5 weeks, it was found to be weakly negatively correlated with mass loss. The similarity in susceptibility to the decomposition of glucans and chitin likely compensates for the impacts of interspecific differences in their initial concentration, leading to overall similar decomposition patterns. Alternatively, other, non‐measured, components (e.g., glycoproteins, N content) may contribute to explaining similar decomposition patterns. Our results indicate that ectomycorrhizal necromass decomposition processes differ from those of plant litter decomposition with, unlike in plants, differences in initial concentrations of major structural carbohydrates (e.g., glucans) being unrelated to differences in decomposition rates. These findings indicate that the decomposition of fungal material cannot be inferred from assumptions based on data provided by studies of plant decomposition. Highlights: Necromass of different ectomycorrhizal species decomposes similarlyMain cell wall components show different decomposition patternsThe relationship between cell wall compounds and mass loss changes over timeMycorrhizal necromass decomposition differs substantially from that of plant litter. [ABSTRACT FROM AUTHOR]

The effect of soil moisture on plant litter decomposition is one of the major focuses of decomposition research. In this study, 150-day laboratory experiments were conducted with the simulated soil environment under different moisture levels. Three macrophytes, Phragmites australis, Miscanthus lutarioriparius, and Carex cinerascens, were selected. The dry biomass weight, and nutrient concentrations of plant samples were measured during the experiment, and a modified bi-exponential formula was used to investigate the effects of soil moisture on plant decomposition under non-submerged conditions. The litter decomposition process is considered as the simultaneous exponential decomposition of labile and refractory components. The relationship between the decomposition rates of the two components and soil moisture was found to be exponential. The results showed that the modified formula with moisture factor agreed well with the dry weight data (R2 > 0.97). The mass fractions of the labile component were 5.9%, 11.3%, and 6.7% for P. australis, M. lutarioriparius, and C. cinerascens, respectively. As moisture increased from 50 to 90%, the decomposition rate k1 of labile part increased from 0.05 to 0.12 day−1, and k2 of refractory part increased from about 0.0007 to 0.006 day−1. Higher quality plant (with high N content and low C content) decomposed faster. The effect of different moisture levels on the microbial community in the experiment was not significant. Furthermore, a longer humidification time in one cycle can promote the decomposition of both parts. The proposed bi-exponential formula of plant decomposition can be used to estimate vegetation decomposition in alternating wetting and drying surface waters. [ABSTRACT FROM AUTHOR]

A field experiment was carried out in plant litter decomposition at three sites of the Balaton System (Balaton — Kis Balaton wetland — Zala Mouth) differing in their environment type during winter 2019/2020. The largest freshwater shallow lake in Central Europe (Carpathian Basin) is the Balaton, with a surface area of about 600 km2 and an average depth of 3.25 m. Right around the lake, a nutrient filtering system, the Kis-Balaton wetland, is functioning to avoid water deterioration and eutrophication. The aim of the study was to investigate crop-weather relations in two sample species, the widely distributed native P. australis and the allied S. canadensis incubated beneath the water using leaf-bag technique to characterise plant organ decomposition. Based on our results, the most consistent meteorological variable regarding decomposition process was global radiation (r = − 0.62* to − 0.91**; r: correlation coefficient; * and ** mean that correlations are significant at the 0.05 and 0.01 levels), in each treatment. In modelling the decomposition process, out of eight meteorological variables, only the daily mean air temperatures and humidity were excluded from regression equations. On dominatingly windy days, with the increase in water temperature of the Zala Mouth, the sensitivity of the decomposition of S. canadensis litter tended to decrease as compared to P. australis. The remaining litter masses were in a Kis-Balaton > Balaton > Zala order, contrasting the water temperature gradient that decreased from the Zala to the Kis-Balaton wetland under wind-dominated conditions. Considering all sampling places in three aquatic ecosystems, there was a 2.2 and a 2.7% daily mean detritus mass loss in P. australis and S. canadensis, respectively. We concluded that the invasive S. canadensis litter decomposed more quickly than those of native P. australis, irrespective to sampling site. Increase in winter water temperature significantly promoted the litter decomposition of both plant species. The originality of the study is that it quantifies the litter decomposition for an Eastern European wetland, during wintertime. [ABSTRACT FROM AUTHOR]

Wetlands are important global carbon sinks, an increasingly important ecosystem service. Invasive plants can disrupt wetland carbon budgets, although efforts to suppress invasive plants may also have unintended effects. Invasive Phragmites australis subsp. australis (European common reed) produces extensive monocultures that displace resident plant communities. In Long Point (Ontario, Canada), a glyphosate-based herbicide was used to control over 900 ha of P. australis. We determined how this ongoing management, and different environmental conditions, influence net primary productivity and decomposition rates. We compared above- and below-ground biomass, belowground:aboveground biomass ratios, standing dead stems, and litter in un-treated P. australis stands, in herbicide-treated areas, and in reference vegetation. We also conducted a reciprocal transplant experiment to measure the decomposition rates of plant litter. One-year post-treatment, control efforts dramatically reduced aboveground biomass (122 g/m2 ± 133 SD) compared to un-treated P. australis (1254 g/m2 ± 449 SD) and reference habitat (821 g/m2 ± 335 SD). An interaction between the plant community of the site and water depth predicted litter decomposition rates, with litter loss ranging from 5.75 to 74.65% across all species, and submerged litter decomposing faster. These results emphasize that secondary treatment, such as rolling, burning, or cutting, encourages the decomposition of dead P. australis stems, opening up space for the recovery of native plants. While herbicide-treated sites had low biomass immediately following treatment, aquatic vegetation began rapidly colonizing treated areas, suggesting that plant community recovery may restore the wetland carbon uptake in subsequent years. [ABSTRACT FROM AUTHOR]

Coevolution has driven speciation and evolutionary novelty in functional traits across the Tree of Life. Classic coevolutionary syndromes such as plant–pollinator, plant–herbivore, and host–parasite have focused strongly on the fitness consequences during the lifetime of the interacting partners. Less is known about the consequences of coevolved traits for ecosystem-level processes, in particular their 'afterlife' legacies for litter decomposition, nutrient cycling, and the functional ecology of decomposers. We review the mechanisms by which traits resulting from coevolution between plants and their consumers, microbial symbionts, or humans, and between microbial decomposers and invertebrates, drive plant litter decomposition pathways and rates. This supports the idea that much of current global variation in the decomposition of plant material is a legacy of coevolution. Plant litter decomposition adds a different process and ecological context to the coevolution literature, which has thus far focused on the ecology of symbionts during their lifetimes. This context integrates the literature on how arms races between plants and their consumers (herbivores, pathogens) or mutualists (nitrogen-fixing bacteria, mycorrhizal fungi) drive the quality of plant tissue, with an important legacy for litter decomposability. We know little about recent coevolutionary decomposition legacies involving plant domestication by humans via farming, plant breeding, and modified landscapes with feedback to evolution of human brain, digestion, and dentition. How myriad coevolutionary links between invertebrates and microbial decomposers affect global carbon cycling needs further investigation. Overall, plant decomposition rates are largely the legacy of wide-ranging coevolutionary relationships. [ABSTRACT FROM AUTHOR]

Simple Summary: Global warming could affect Collembola and related decomposition processes within soil ecosystems in permafrost wetlands. Open top chambers (OTCs) were used to simulate climate warming in a cold temperate monsoon climate zone in the Great Hing'an Mountains of Northeast China. Collembola were captured using an aspirator after five years of simulated warming. We found that warming treatment increased the species richness and abundance of Collembola in most of the different seasons, except in May. Species composition differed significantly in the control and warming treatment in May and September. The Collembola species composition in permafrost wetlands was mainly determined by air humidity, indicating different responses of Collembola species to the indirect effect of warming on water availability. It is indicated that warming was the primary factor positively affecting the abundance of Collembola. An increase of Collembola abundance and community alteration to warming could have profound cascading effects on the microbes and plants they feed on in permafrost wetlands. The consideration of environmental factors has long been crucial to developing theories about the spatial variability of species diversity. However, the effects of global warming on Collembola, in permafrost wetlands, are largely unknown. Understanding how Collembola are affected by climate warming is important as they directly affect the community assembly and decomposition processes of plant litter within soil ecosystems. A peatland area in a cold temperate monsoon climate zone in the Great Hing'an Mountains of Northeast China was selected as the study area. Collembola were captured using an aspirator after five years of simulated warming using open top chambers (OTCs). Sampling in different growth seasons showed different characteristics in the control (CK) and warming (OTCs) treatment. Further, the results showed that (1) warming treatment increased the species richness and abundance of Collembola in the different seasons, except in May, (2) warming increased Collembola abundance in permafrost wetlands, and the warming effect was more significant during the cold season (about eight times in April), (3) species composition differed significantly in the control and warming treatment in May and September, and (4) the Collembola species composition in permafrost wetlands was mainly determined by air humidity, indicating different responses of Collembola species to the indirect effect of warming on water availability. We found that warming was the primary factor positively affecting the abundance of Collembola. An increase of Collembola abundance and community alteration to warming could have profound cascading effects on the microbes and plants they feed on in permafrost wetlands. [ABSTRACT FROM AUTHOR]

Copyright of Environmental Science & Technology (10036504) is the property of Editorial Board of Environmental Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Predicting and mitigating changes in soil carbon (C) stocks under global change requires a coherent understanding of the factors regulating soil organic matter (SOM) formation and persistence, including knowledge of the direct sources of SOM (plants vs. microbes). In recent years, conceptual models of SOM formation have emphasized the primacy of microbial‐derived organic matter inputs, proposing that microbial physiological traits (e.g., growth efficiency) are dominant controls on SOM quantity. However, recent quantitative studies have challenged this view, suggesting that plants make larger direct contributions to SOM than is currently recognized by this paradigm. In this review, we attempt to reconcile these perspectives by highlighting that variation across estimates of plant‐ versus microbial‐derived SOM may arise in part from methodological limitations. We show that all major methods used to estimate plant versus microbial contributions to SOM have substantial shortcomings, highlighting the uncertainty in our current quantitative estimates. We demonstrate that there is significant overlap in the chemical signatures of compounds produced by microbes, plant roots, and through the extracellular decomposition of plant litter, which introduces uncertainty into the use of common biomarkers for parsing plant‐ and microbial‐derived SOM, especially in the mineral‐associated organic matter (MAOM) fraction. Although the studies that we review have contributed to a deeper understanding of microbial contributions to SOM, limitations with current methods constrain quantitative estimates. In light of recent advances, we suggest that now is a critical time to re‐evaluate long‐standing methods, clearly define their limitations, and develop a strategic plan for improving the quantification of plant‐ and microbial‐derived SOM. From our synthesis, we outline key questions and challenges for future research on the mechanisms of SOM formation and stabilization from plant and microbial pathways. [ABSTRACT FROM AUTHOR]

Simple Summary: The addition of plant leaf litter to soils represents a critical component of the global carbon (C) and nitrogen (N) cycles. Tropical cyclones known at typhoons in the western Pacific islands transfer an enormous amount of green leaf litter from the forest canopy to the soil. We have shown on the island of Guam that this green litter releases carbon and nitrogen extremely rapidly compared with senesced leaf litter. Moreover, species such as Guam's native cycad Cycas micronesica produce slowly decomposing litter, while other species such as Guam's native angiosperm Morinda citrifolia produce rapidly decomposing litter. Soil priming is an important process in the global C cycle, and occurs when pre-existing organic matter releases more C as a result of new organic C additions. The green litter generated soil priming that was almost double that of the senesced litter. The release of N from the green litter into forms that are available to plants required only 14 d for the M. citrifolia litter but required more than 90 d for the C. micronesica litter. Scientists predict more frequent intense typhoons in the future, and we have shown one of the ecosystem-level processes that these typhoons will change. Plant leaf litter decomposition is directly influenced by the identity of the source plants and the leaf age. Defoliation of forests by tropical cyclones (TC) transfers copious amounts of high-quality green leaf litter to soils. We used a soil amendment approach with the incubated buried bag method to compare carbon (C) and nitrogen (N) mineralization dynamics of green and senesced leaf litter from cycad Cycas micronesica and angiosperm Morinda citrifolia trees on the island of Guam. Soil priming increased the decomposition of pre-existing organic C, and were greater for green leaf litter additions than senesced leaf litter additions. Available N content increased by day 14 and remained elevated for the entire 117-d incubation for soils amended with green M. citrifolia litter. In contrast, available N content increased above those in control soils by day 90 and above those in soils amended with senesced litter by day 117 for green C. micronesica litter. The net N mineralization rate was higher than control soils by 120% for the senesced litter treatments and 420% for the green litter treatments. The results reveal a complex but predictable interplay between TC defoliation and litter quality as defined by tree identity. We have illuminated one means by which increased frequency of intense TCs due to climate change may alter the global C and N cycles. [ABSTRACT FROM AUTHOR]

Decomposition of plant litter is a fundamental ecological process, integral to soil formation, soil organic matter chemistry, and biogeochemical cycling. However, much of our understanding of decay dynamics focuses on rates of litter mass loss and therefore carbon dynamics, with relatively less exploration of the chemical nature of litter decomposition during which the degradation of litter structural and metabolic compounds into fragments are either metabolized or ultimately incorporated into soil humus. Our understanding of the patterns of changes in litter chemistry throughout decomposition is incomplete, as few studies have measured chemical content beyond initial litter chemistry and throughout decay, and particularly not chemistry beyond carbon and nitrogen. The existing literature also reports idiosyncratic instances of litter chemical convergence and divergence. We used archived litter decomposition samples and data from across the U.S. Long-Term Ecological Research Network to investigate the trajectory of a comprehensive array of litter chemistry, including nutrient, structural, and metabolic parameters, across a wide variety of plant functional types and ecosystems, throughout the first 70% of mass loss. Our results do not yield a universally common pattern of litter chemical trajectories across all functional types and regions, and very limited evidence of convergence or divergence in chemistry over time, mostly within the nutrient elements. We provide details about the behavior of individual chemical parameters to functional type and region over decay. Changes in plant communities driven by global change may alter nutrient cycling and SOM formation through persistence or divergence on litter chemistry inputs. [ABSTRACT FROM AUTHOR]

Plant litter decomposition is a key process in the biogeochemical cycles of terrestrial ecosystems. The main goal of this work is to determine the impact of current climate change on the decomposition process of the litter of Palo Laziale Wood (Rome, Italy), one of the last remnants of the Tyrrhenian lowland forest. A time-dependent simulation of leaf litter decay was previously performed on a dynamic semi-empirical model based on Olson's model (1963). It was also assumed that microbial activity depended on optimal temperature and moisture conditions simulated by Climatic Decomposition Index (CDI). The comparison between the observed and simulated leaf litter biomass reduction over time (t = −0.127, p = 0.901) highlighted the adequacy of CDI in reproducing biomass trends under limiting climatic conditions (high temperature and low precipitation). However, the decomposition model used here was not able to simulate the reduction of recalcitrant compounds (lignin) in strongly limiting conditions of water availability in the Palo Laziale Wood. These climatic conditions were attributable to climate change, which made the year 2020 representative of future years increasingly characterized by limiting climatic conditions. Therefore, it is necessary to carefully calibrate the CDI in order to consider the current and future changes in temperature and water availability in the Mediterranean area, and to, therefore, perform a better model-based foreseeing for leaf litter decomposition. [ABSTRACT FROM AUTHOR]

Plant litter decomposition is a key ecosystem process in carbon and nutrient cycling, and is heavily affected by changing climate. While the direct effects of drought on decomposition are widely studied, in order to better predict the overall drought effect, indirect effects associated with various drought‐induced changes in ecosystems should also be quantified. We studied the effect of an extreme (5‐month) experimental drought on decomposition, and if this effect varies with two dominant perennial grasses, plant parts (leaves vs. roots), and soil depths (0–5 cm vs. 10–15 cm) in a semi‐arid temperate grassland. After 12 months, the average litter mass loss was 43.5% in the control plots, while only 25.7% in the drought plots. Overall, mass loss was greater for leaves (44.3%) compared to roots (24.9%), and for Festuca vaginata (38.6%) compared to Stipa borysthenica (30.5%). This variation was consistent with the observed differences in nitrogen and lignin content between plant parts and species. Mass loss was greater for deep soil (42.8%) than for shallow soil (26.4%). Collectively, these differences in decomposition between the two species, plant parts, and soil depths were similar in magnitude to direct drought effect. Drought induces multiple changes in ecosystems, and our results highlight that these changes may in turn modify decomposition. We conclude that for a reliable estimate of decomposition rates in an altered climate, not only direct but also indirect climatic effects should be considered, such as those arising from changing species dominance, root‐to‐shoot ratio, and rooting depth. [ABSTRACT FROM AUTHOR]

Purpose: In long-term global change experiments, while cumulative treatment effects on soil and plant responses can emerge over time, comparisons between short and long-term responses can potentially be confounded with interannual variability in the environment. We added new nitrogen addition and warming plots to a pre-existing nitrogen and warming field experiment in a grass-dominated field to compare the short-term (1–2 year; new plots) versus long-term (14–15 year; old plots) treatment effects on soil microbial activity and plant litter decomposition, while controlling for the effects of interannual environmental variability. Methods: We assessed microbial activity by assaying the potential activities of five soil extracellular enzymes: three hydrolase enzymes (N-acetyl-glucosaminidase, phosphatase and β-glucosidase) and two oxidase enzymes (phenol oxidase and peroxidase). We measured mass loss from litter bags to assess the decomposition of grass and forb litter. Results: Warming interacted with plot age, with increased hydrolase activity in spring in response to warming only occurring in the long-term plots; increases in peroxidase activity with nitrogen addition in spring occurred for all plots. By summer, there were no significant interactions between the treatments and plot age for enzyme activity. Decreased decomposition with warming, observed for forb litter, only occurred in the long-term plots, but increased decomposition with nitrogen addition, observed for grass litter, occurred in both the long-term and short-term plots. Conclusions: Our results confirm an intensification of treatment effects on enzyme activity and litter decomposition over time for warming, but no interactions with plot age for nitrogen addition. [ABSTRACT FROM AUTHOR]

Purpose: Winter snow cover is a key control over soil biogeochemical cycles in cold biomes but has decreased with climate warming, particularly in high-latitude and high-altitude areas. Previous studies have found a decline in carbon (C) release from decomposing litter without snow cover, yet partitioning what C fractions respond to snow removal remains not fully understood. Methods: Here we incubated fir and birch litter in microcosms over two years of decomposition in an alpine forest to assess the release of various C fractions with and without snow cover using 13C nuclear magnetic resonance (NMR). Results: We found that 51% and 61% of total organic C was lost from fir and birch litter, respectively, after two years of decomposition, and 59% and 60% of this C was decomposed during winter. More C was lost from both fir and birch litter under snow cover, and the decomposition rate of birch litter C was decreased by 50% after snow removal. However, only O-alkyl C (particularly carbohydrate C) release was reduced with snow removal, and the release of other C fractions (i.e., alkyl C, aromatic C and carbonyl C) did not change significantly after removing snow cover. Delayed O-alkyl C release from fir and birch litter was in accordance with the declines in soil dissolved organic C and microbial respiration rate under removed snow plots, but this delay induced by snow removal did not carry over to the following growing season. Conclusion: We conclude that a reduction in winter snow cover regulates early decomposition of plant litter by controlling the rapid release of more labile C fractions (i.e., carbohydrates) in seasonally snow-covered ecosystems. [ABSTRACT FROM AUTHOR]

Plant leaf litter decomposition provides a source of energy and nutrients in forest ecosystems. In addition to traditional environmental factors, the degradation process of litter is also affected by plant functional traits and litter quality. However, at the community level, it is still unclear whether the relative importance of plant traits and litter quality on the litter decomposition rate is consistent. A year-long mixed leaf litter decomposition experiment in a similar environment was implemented by using the litterbag method in seven typical forest types in Dongling Mountain, Beijing, North China, including six monodominant communities dominated by Juglans mandshurica , Populus cathayana , Betula dahurica , Betula platyphylla , Pinus tabuliformis and Larix gmelinii var. principis-rupprechtii and one codominant community dominated by Fraxinus rhynchophylla , Quercus mongolica and Tilia mongolica. The results showed that there were considerable differences in the litter decomposition rate (k -rate) among the different forest types. The community weighted mean (CWM) traits of green leaves and litter quality explained 35.60% and 9.05% of the k -rate variations, respectively, and the interpretation rate of their interaction was 23.37%, indicating that the CWM traits and their interaction with litter quality are the main factors affecting the k-rate variations. In the recommended daily allowance, leaf nitrogen content, leaf dry matter content, leaf tannin content and specific leaf area were the main factors affecting the k -rate variations. Therefore, we suggest that future studies should focus on the effects of the CWM traits of green leaves on litter decomposition at the community level. [ABSTRACT FROM AUTHOR]

To assess how the presence of an invasive plant and different-sized decomposers affect plant litter decomposition under different seasonal conditions, we allocated leaves of native Ficus virens Aiton into four different mesh sizes (0.025, 0.042, 0.5 and 5 mm) with and without invasive Alternanthera philoxeroides (Mart.) Griseb. We incubated them for 65 days in an eutrophic lake in summer and winter respectively. The average decomposition rate was significantly higher in summer than in winter, and was significantly higher in mixtures than in F. virens monocultures in both seasons. The presence of A. philoxeroides in the mixture significantly increased invertebrate density and microbial respiration rates in summer but not in winter. Furthermore, contribution of invertebrates to decomposition was higher in the early stage of decomposition and lower in the late stage in summer, yet that of microbes was relatively constant in winter. Contribution of microinvertebrates increased in summer but that of meio-, macroinvertebrates increased in winter. Our findings indicate that the presence of an invasive plant altered litter decomposition, which may depend on seasonal variations, invertebrate density and decomposition stages. [ABSTRACT FROM AUTHOR]

(1) Background: Plant litter decomposition and its effect on soil nutrients are important parts of the ecosystem material cycle, and understanding these processes is key for species selection and allocation, to promote the effective use of litter in ecological tea gardens. (2) Methods: In situ decomposition was used in this study Changes in decomposition rate, element release, and soil properties during the decomposition of the mixed plant residues were measured. (3) Results: The decomposition rate (k) of the CCG (Camellia sinensis + Cinnamomum glanduliferum) mixed plant residue was significantly higher than that of the CS (Camellia sinensis) residue. The decomposition of the CCG, CPM (C. sinensis + Pinus massoniana), and CBL (C. sinensis + Betula luminifera) mixed plant residues showed an additive effect, whereas that of the CCL residue showed an antagonistic effect. The CBL mixed plant residue promoted the release of N; the decomposition of the CCG, CPM, CCL (C. sinensis + Cunninghamia lanceolata), and CBL residues promoted the release of TC (total carbon); and the decomposition of the CCG residue promoted the release of cellulose. After 428 d of decomposition, the four mixed plant residues had improved the soil nutrient contents to some extent. CCG and CBL residue decomposition resulted in greater improvements in soil nutrients. (4) Conclusions: The application of the mixture of material obtained by pruning C. glanduliferum, B. luminifera, and C. sinensis in an ecological tea garden accelerated the decomposition and nutrient release rates, increased soil nutrient contents, shortened the decomposition turnover period of plant residues, and accelerated the nutrient cycle of plant residues in the ecological tea garden. [ABSTRACT FROM AUTHOR]

Background. Plant litter decomposition is a key process in carbon and nutrient cycling. Among the factors determining litter decomposition rates, the role of soil biota in the decomposition of different plant litter types and its modification by variations in climatic conditions is not well understood. Methods. In this study, we used litterbags with different mesh sizes (45 mm, 1 mm and 4 mm) to investigate the effect of microorganisms and decomposer microarthropods on leaf and root litter decomposition along an altitudinal gradient of tropical montane rainforests in Ecuador. We examined decomposition rates, litter C and N concentrations, microbial biomass and activity, as well as decomposer microarthropod abundance over one year of exposure at three different altitudes (1,000, 2,000 and 3,000 m). Results. Leaf litter mass loss did not differ between the 1,000 and 2,000 m sites, while root litter mass loss decreased with increasing altitude. Changes in microbial biomass and activity paralleled the changes in litter decomposition rates. Access of microarthropods to litterbags only increased root litter mass loss significantly at 3,000 m. The results suggest that the impacts of climatic conditions differentially affect the decomposition of leaf and root litter, and these modifications are modulated by the quality of the local litter material. The findings also highlight litter quality as the dominant force structuring detritivore communities. Overall, the results support the view that microorganisms mostly drive decomposition processes in tropical montane rainforests with soil microarthropods playing a more important role in decomposing low-quality litter material. [ABSTRACT FROM AUTHOR]

Application of organic soil amendments is commonplace in horticulture to improve soil fertility. Whether this practice can also augment the soil carbon (C) pool has been of increasing interest in recent years. We used a controlled field experiment that has received annual applications of six different horticultural soil amendments for seven consecutive years. Each amendment was examined in terms of its contribution to bulk C and the distribution of C between theoretical pools, as defined by physical fractionation. Physical fractionation was combined with 13C nuclear magnetic resonance spectroscopy with cross-polarization and magic angle spinning (CPMAS NMR) analysis. Results indicated that the difference in total C concentration between treatments resulted from an increase in unprotected, free, particulate organic matter (fOM), rather than an increase in soil organic matter being occluded in aggregates or in organo-mineral complexes, and that C persisted in the fOM fraction as a result of accumulation in the alkyl C region. Unlike fresh litter or plant residues, organic amendments have undergone decomposition during the composting process (or during formation in the case of peat), in the absence of mineral soil components. This ex situ decomposition (and possible stabilization through acquired recalcitrance) could reduce the opportunity to become physically or chemically protected through association with the soil mineral phase following addition to soil. Carbon:Nitrogen (C:N) of amendment material likely influenced the rate of amendment decomposition. In addition, C:N determines the decomposition of plant litter inputs, as determined by the tea bag index. [ABSTRACT FROM AUTHOR]

Arbuscular mycorrhizal fungi (AMF) play an important role on litter decomposition, which is the keyways for nutrients returning to natural ecosystems. Although having no known saprotrophic abilities like ectomycorizal and ericoid fungi, AMF can affect litter decomposition by releasing low molecular compounds such as sugar, amino acids and organic acids through extraradical mycorrhizal hyphae, or deposit dead hypha fragments as nutrient (e.g., carbon) input and to stimulate microbial decomposers, i.e., priming effect. Besides, interactions of AMF with saprotrophic microorganisms through ways such as niche competition, synergistic cooperation, specific microorganisms recruitment and by soil nutrient removal that can influence litter decomposition. Under different microenvironments, AMF display various nutrient acquisition strategies, which also affects this process. The magnitude and direction of AMF effects on litter decomposition depend on plant communities, litter quality, soil and litter nutrient dynamics, soil physical and chemical properties (mainly, physical structure, temperature, humidity, pH and nutrient content). The exacerbation of global changes (drought, chemical fertilization and soil acidification) is exerting pervasive impacts on ecosystem processes and functions mediated by AMF. In this review, we explore the current state of knowledge about the impacts of AMF on litter decomposition from microenvironment perspective. The summary of the potential influence of various microsite abiotic and biotic factors on this process in order to provide theoretical reference for comprehensive analysis of ecosystem functions of AMF is made. [ABSTRACT FROM AUTHOR]

Acute resource pulses can have dramatic legacies for organismal growth, but the legacy effects of resource pulses on broader aspects of community structure and ecosystem processes are less understood. Mass emergence of periodical cicadas (Magicicada spp.) provides an excellent opportunity to shed light on the influence of resource pulses on community and ecosystem dynamics: the adults emerge every 13 or 17 years in vast numbers over much of eastern North America, with a smaller but still significant number becoming incorporated into forest food webs. To study the potential effects of such arthropod resource pulse on primary production and belowground food webs, we added adult cicada bodies to the soil surface surrounding sycamore trees and assessed soil carbon and nitrogen concentrations, plant‐available nutrients, abundance and community composition of soil fauna occupying various trophic levels, decomposition rate of plant litter after 50 and 100 days, and tree performance for 4 years. Contrary to previous studies, we did not find significant cicada effects on tree performance despite observing higher plant‐available nutrient levels on cicada addition plots. Cicada addition did change the community composition of soil nematodes and increased the abundance of bacterial‐ and fungal‐feeding nematodes, while plant feeders, omnivores, and predators were not influenced. Altogether, acute resource pulses from decomposing cicadas propagated belowground to soil microbial‐feeding invertebrates and stimulated nutrient mineralization in the soil, but these effects did not transfer up to affect tree performance. We conclude that, despite their influence on soil food web and processes they carry out, even massive resource pulses from arthropods do not necessarily translate to NPP, supporting the view that ephemeral nutrient pulses can be attenuated relatively quickly despite being relatively large in magnitude. [ABSTRACT FROM AUTHOR]

Plant litter decomposition is a biogeochemical process underlying the carbon cycle in terrestrial ecosystems and between the biosphere and the atmosphere. For the latter, it serves as one of the most important sources of not only carbon dioxide but also volatile organic compounds (VOCs), which have not yet been taken into account in atmospheric models for various purposes and scales, from local to regional and global. This review owes its appearance to the growing interest in decaying leaf litter and living forest floor cover as a hitherto unaccounted for source of photochemically active components of the Earth's atmosphere. This interest is understandable if we take into account the size of this source: for terrestrial ecosystems, the global production of litter is 10 × 10 16 g dry matter. The living vegetation cover of the soil on the forest floor, mainly comprising mosses and small shrubs, should also be regarded as a potentially significant source of atmospheric VOCs, as its total biomass may be comparable to or even exceed that of canopy foliage, which is considered the main source of these compounds. This implies a need to integrate these sources into biogenic VOC emission models, which in turn requires extensive research on these sources to understand the conditions and factors that influence VOC emissions. The decomposition of leaf litter, accompanied by the release of VOCs, is a very complex process that depends on a number of biological, chemical and physical environmental factors, but little information is currently available on the role each plays. Equally limited is information on the chemical composition and emission rates of VOCs from these sources. The review focuses on the main gaps in our knowledge of the sources of biogenic VOCs under the forest canopy, and we are confident that filling them will make a significant contribution to solving such an important task as closing the global organic carbon budget. [ABSTRACT FROM AUTHOR]