Root Litter Decomposition Research Articles

Differences in the regulation of soil carbon pool quality and stability by leaf-litter and root-litter decomposition

Litter plays a crucial role in soil ecosystems. However, the differences in decomposition between leaf-litter and root-litter and their relative contributions to soil carbon pools and stability are not yet clear. Therefore, we conducted a 450-day in situ decomposition experiment in a semi-arid grassland to investigate the effects of soil biophysical and chemical properties on litter decomposition and to elucidate the dynamics of soil carbon pools during the decomposition process. The results showed that the decomposition rate (K) of leaf-litter was significantly higher than that of root-litter, and litter quality was the most important factor affecting the K of leaf-litter (58%) and root-litter (63%). Leaf-litter decomposition was more effective in promoting the increase in soil leucine aminopeptidase and β-1,4-glucosidase activities, as well as the accumulation of microbial biomass carbon (MBC), particulate organic carbon (POC), and dissolved organic carbon (DOC), compared to root-litter. However, the difference in the impact of leaf-litter and root-litter on soil organic carbon (SOC) was not significant. The decomposition of leaf-litter contributed more significantly to enhancing the soil carbon pool management index (CPMI) compared to root-litter, with increases of 39% and 25%, respectively. In contrast, leaf-litter decomposition significantly reduced the mineral-associated organic carbon (MAOC) and the MAOC/POC ratio, while root-litter decomposition significantly increased the MAOC and MAOC/POC. Random forest, partial correlation, and path analysis indicated that the effects of leaf-litter and root-litter decomposition on CPMI were mainly regulated by decomposition time and soil carbon components, while the effects on MAOC/POC were mainly controlled by litter quality. The results demonstrate that both leaf-litter and root-litter can enhance soil carbon storage and CPMI, but root-litter may be more beneficial for soil carbon pool stability. These results further contribute to the understanding of the continuous system of litter-soil carbon pools.

Resolving the Intricate Effects of Multiple Global Change Drivers on Root Litter Decomposition.

Plant roots represent about a quarter of global plant biomass and constitute a primary source of soil organic carbon (C). Yet, considerable uncertainty persists regarding root litter decomposition and their responses to global change factors (GCFs). Much of this uncertainty stems from a limited understanding of the multifactorial effects of GCFs and it remains unclear how these effects are mediated by litter quality, soil conditions and microbial functionality. Using complementary field decomposition and laboratory incubation approaches, we assessed the relative controls of GCF-mediated changes in root litter traits and soil and microbial properties on fine-root decomposition under warming, nitrogen (N) enrichment, and precipitation alteration. We found that warming and N enrichment accelerated fine-root decomposition by over 10%, and their combination showed an additive effect, while precipitation reduction suppressed decomposition overall by 12%, with the suppressive effect being most significant under warming-alone and N enrichment-alone conditions. Significantly, changes in litter quality played a dominant role and accelerated fine-root decomposition by 15% ~ 18% under warming and N enrichment, while changes in soil and microbial properties were predominant and reduced decomposition by 7% ~ 10% under precipitation reduction and the combined warming and N enrichment. Examining only the decomposition environment or litter properties in isolation can distort global change effects on root decomposition, underestimating precipitation reduction impacts by 38% and overstating warming and N effects by up to 73%. These findings highlight that the net impact of GCFs on root litter decomposition hinges on the interplay between GCF-modulated root decomposability and decomposition environment, as well as on the synergistic or antagonistic relationships among GCFs themselves. Our study emphasizes that integrating the legacy effects of multiple GCFs on root traits, soil conditions and microbial functionality would improve our prediction of C and nutrient cycling under interactive global change scenarios.

Wheat cover crop accelerates the decomposition of cucumber root litter by altering the soil microbial community

Cover cropping is a diversifying agricultural practice that can improve soil structure and function by altering the underground litter diversity and soil microbial communities. Here, we tested how a wheat cover crop alters the decomposition of cucumber root litter. A three-year greenhouse litterbag decomposition experiment showed that a wheat cover crop accelerates the decomposition of cucumber root litter. A microcosm litterbag experiment further showed that wheat litter and the soil microbial community could improve cucumber root litter decomposition. Moreover, the wheat cover crop altered the abundances and diversities of soil bacterial and fungal communities, and enriched several putative keystone OTUs, such as Bacillus spp. OTU1837 and Mortierella spp. OTU1236, that were positively related to the mass loss of cucumber root litter. The representative bacterial and fungal strains B186 and M3 were isolated and cultured. In vitro decomposition tests demonstrated that both B186 and M3 had cucumber root litter decomposition activity and a stronger effect was found when they were co-incubated. Overall, a wheat cover crop accelerated cucumber root litter decomposition by altering the soil microbial communities, particularly by stimulating certain putative keystone taxa, which provides a theoretical basis for using cover crops to promote sustainable agricultural development.

Root litter decomposition is suppressed in species mixtures and in the presence of living roots.

Plant species diversity and identity can significantly modify litter decomposition, but the underlying mechanisms remain elusive, particularly for root litter. Here, we aimed to disentangle the mechanisms by which plant species diversity alters root litter decomposition. We hypothesised that (1) interactions between species in mixed communities result in litter that decomposes faster than litter produced in monocultures; (2) litter decomposition is accelerated in the presence of living plants, especially when the litter and living plant identities are matched (known as home-field advantage).Monocultures and a mixture of four common grassland species were established to obtain individual litter and a 'natural' root litter mixture. An 'artificial' mixed litter was created using litter from monocultures, mixed in the same proportions as the species composition in the natural litter mixtures based on qPCR measurements. These six root litter types were incubated in four monocultures, a four-species mixture and an unplanted soil.Root decomposition was strongly affected by root litter identity and the presence, but not diversity, of living roots. Mixed-species litter decomposed slower than expected based on the decomposition of single-species litters. In addition, the presence of living roots suppressed decomposition independent of the match between litter and living plant identities. Decomposition was not significantly different between the 'natural' and 'artificial' root litter mixtures, indicating that root-root interactions in species mixtures did not affect root chemical quality. Synthesis. Suppressed decomposition in the presence of living roots indicates that interactions between microbial communities associated with living roots and root litter control root litter decomposition. As we found no support for the importance of home-field advantage or interspecific root interactions in modifying decomposition, suppressed decomposition of mixed-species litter seems to be primarily driven by chemical rather than biotic interactions.

Effects of Soil Arthropods on Non-Leaf Litter Decomposition: A Meta-Analysis

According to the widely accepted triangle model, global litter decomposition is collectively controlled by climate, litter initial quality, and decomposers. However, the specific contribution of soil arthropods to litter, especially the non-leaf litter, the decomposition of terrestrial ecosystems and its drivers are still unclear. We conducted a global meta-analysis based on 268 pairs of data to determine the contribution and pattern of soil arthropods to branch, stem, and root litter decomposition in farmlands, forests, and grasslands and analyzed the relationship of soil arthropods’ decomposition effect and potential drivers. Our results showed that: (1) soil arthropods increased global non-leaf litter mass loss by 32.3%; (2) the contribution varied with climate zone and ecosystem type, with a value of subtropical (53.3%) > temperate (18.7%) > tropical (14.7%) and of farmlands (40.6%) > grasslands (34.3%) > forests (0.6%), respectively; (3) the soil arthropods’ decomposition effect gradually decreased with decomposition time, and it was higher in litterbags with a mesh size of 1–2 mm (65.4%) and >2 mm (49.8%) than that of 0.5–1 mm (13.6%); (4) the soil arthropods’ decomposition effects were negatively correlated with the litter initial C/N ratio, mean annual precipitation (MAP; p < 0.001), and elevation and was positively correlated with litter weight. In conclusion, soil arthropod promoted global non-leaf litter decomposition, and the contribution varied with climate zone, ecosystem type, and decomposition time as well as litterbag mesh size. Overall, this study improves the understanding of soil arthropods driving global non-leaf litter decomposition.

Root litter decomposition rates and impacts of drought are regulated by ecosystem legacy

In grassland ecosystems, about two-thirds of productivity is in roots, and therefore roots constitute a major soil organic matter input. However, influences on the rate of root litter decomposition remain unresolved, especially in the context of land-use conversion and climate change. Ecosystem legacy can affect root decomposition rates via impacts on substrate chemistry and soil environments, and this may manifest in responses of decomposition to changing temperature and moisture. Here we investigate the impacts of anthropogenic legacy effects and moderate drought on root litter decomposition rates in five “Land Use History Types”: crop fields, cow pastures, remnant tallgrass prairie, and prairie restored from crop fields and pastures. We measured root losses of mass, carbon, and nitrogen over 11 months. Soil bulk density was unimportant for decomposition, but soil moisture content and temperature were relevant for decomposition rates while time since disturbance predicted decomposition initiation times. Furthermore, soil moisture and temperature dynamics alone could not explain the responses of decomposition rates to drought, which were positively correlated to time since disturbance. Our findings suggest that anthropogenic legacy impacts decomposition rates in grasslands, especially when soil moisture and temperature dynamics are substantially altered, and mediates soil community responses to drought.

Pathways of glyphosate effects on litter decomposition in grasslands

AbstractGrasslands store a third of global terrestrial carbon but are vulnerable to carbon loss due to inappropriate livestock grazing. Grasslands management can be improved with a mechanistic understanding of biogeochemical processes that determine carbon storage, such as plant litter decomposition.Herbicides, such as glyphosate, are used to improve the quantity and quality of the forage. In the Flooding Pampa, the most extensive cattle grazed natural grassland and one of the few remnants' temperate grasslands in South America—glyphosate is applied to promoteLolium multiflorum, a forage grass associated with a fungal endophyte nontoxic for cattle.We studied five mechanistic pathways in which the application of glyphosate can alter litter decomposition. We grouped them into single application pathways, through effects on living plants (1), leaf litter (2) and bare soil (3), and repeated annual application pathways, through legacies on ecosystem properties (4) and through the growth of an annual forage grass with a fungal endophyte (5). Single application pathways were tested in a greenhouse experiment using leaf litter ofL. multiflorumand of a native dominant grass. Repeated annual application pathways were tested through a field experiment with 3‐year annual glyphosate application using leaf and root litter ofL. multiflorumwith and without endophyte association.Glyphosate application on living plants produced leaf litter with 70% higher nitrogen content and 140% higher decomposition constant than naturally senesced litter. In contrast, glyphosate application on naturally senesced leaf litter reduced decomposition constant by 20%. Glyphosate application on the soil did not affect the decomposition of naturally senesced leaf litter but accelerated the decomposition of the glyphosate‐killed plants even more.Legacies of repeated annual application of glyphosate resulted in a notable reduction in plant cover (45%) and potential soil respiration (57%), with a consistent acceleration of leaf (53%) and root (18%) litter decomposition. Furthermore, endophytes inL. multiflorumplants reduced leaf litter decomposition by 22%. On the contrary, endophytes did not alter root litter decomposition.Glyphosate application on living plants and legacies of repeated application on the ecosystem stimulate litter decomposition, which can result in a net carbon loss from grasslands. In other ecosystems, the net result on decomposition would depend on the relative cover of vegetation, above‐ground litter and bare soil. This study highlights that glyphosate application should be considered when evaluating sustainable management to preserve and enhance soil carbon storage in grasslands.Read the freePlain Language Summaryfor this article on the Journal blog.

Moso bamboo expansion reduced soil N2O emissions while accelerated fine root litter decomposition: contrasting non-additive effects

Moso bamboo expansion reduced soil N2O emissions while accelerated fine root litter decomposition: contrasting non-additive effects

Differences in leaf and root litter decomposition in tropical montane rainforests are mediated by soil microorganisms not by decomposer microarthropods.

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. In this study, we used litterbags with different mesh sizes (45 µm, 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). 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.

Contribution of Fine Roots to Soil Organic Carbon Accumulation in Different Desert Communities in the Sangong River Basin.

This study explored the relationship between soil organic carbon (SOC) and root distribution, with the aim of evaluating the carbon stocks and sequestration potential under five plant communities (Alhagi sparsifolia, Tamarix ramosissima, Reaumuria soongorica, Haloxylon ammodendron, and Phragmites communis) in an arid region, the Sangong River watershed desert ecosystem. Root biomass, ecological factors, and SOC in different layers of a 0–100 cm soil profile were investigated. The results demonstrated that almost all living fine root biomass (11.78–34.41 g/m2) and dead fine root biomass (5.64–15.45 g/m2) levels were highest in the 10–20 cm layer, except for the P. communis community, which showed the highest living and dead fine root biomass at a depth of 60–70 cm. Fine root biomass showed strong seasonal dynamics in the five communities from June to October. The biomass levels of the A. sparsifolia (138.31 g/m2) and H. ammodendron (229.73 g/m2) communities were highest in August, whereas those of the T. ramosissima (87.76 g/m2), R. soongorica (66.29 g/m2), and P. communis (148.31 g/m2) communities were highest in September. The SOC of the five communities displayed strong changes with increasing soil depth. The mean SOC value across all five communities was 77.36% at 0–30 cm. The highest SOC values of the A. sparsifolia (3.08 g/kg), T. ramosissima (2.35 g/kg), and R. soongorica (2.34 g/kg) communities were found in June, and the highest value of the H. ammodendron (2.25 and 2.31 g/kg, p > 0.05) community was found in June and September. The highest SOC values of the P. communis (1.88 g/kg) community were found in July. Fine root production and turnover rate were 50.67–486.92 g/m2/year and 1.25–1.98 times per year. The relationships among SOC, fine root biomass, and ecological factors (soil water content and soil bulk density) were significant for all five communities. Based on the results, higher soil water content and soil conductivity favored the decomposition of root litter and increased fine root turnover, thereby facilitating SOC formation. Higher pH and bulk density levels are not conducive to soil biological activity and SOC mineralization, leading to increased SOC levels in desert regions.

Rhizodeposition and litter decomposition of Phragmites australis play important roles in composition and properties of soil dissolved organic matter

The dynamics of composition and properties of dissolved organic matter in soil depend on plant carbon inputs and microbial degradation. However, uncertainties remain regarding the relative contributions of different plant carbon inputs sources, i.e., from litter decomposition versus rhizodeposits, to soil dissolved organic matter, which may limit the understanding of soil carbon dynamics. In this study, effects of plant carbon inputs from either rhizodeposition or litter (leaf, stem, rhizome, and root litter) decomposition on composition and optical properties of soil dissolved organic matter were estimated. Rhizodeposition and litter decomposition of P. australis had significant effects on soil dissolved organic matter, and its variation was mainly associated with the third fluorescent component (C3). Effects of rhizodeposition on soil dissolved organic matter were significantly altered by soil salinity, exhibiting increased chromophoric dissolved organic matter and fulvic acid C3 under saline conditions. Effects of litter decomposition on soil chemistry and dissolved organic matter varied greatly among plant tissues. Compared with rhizome and root, leaf and stem decomposed more thoroughly and significantly increased the contents of fulvic acid C3. This was supported by increased aromaticity associated with leaf inputs and increased plant-derived dissolved organic matter associated with stem and leaf inputs. These findings highlight the significant influence of rhizodeposition and litter decomposition on soil dissolved organic matter, and suggest that the roles of salinization and plant tissue type merit consideration in further studies on plant–soil carbon cycling.

Grazing promoted plant litter decomposition and nutrient release: A meta-analysis

Grazing considerably affects ecosystem nutrient cycling and element stoichiometry at the regional and global levels according to synthesized studies. However, the effects of grazing, especially its intensity, on the plant litter decomposition stage of key processes in biogeochemical cycles are not clearly understood. Here, a meta-analysis of 65 published papers was undertaken to examine the responses of eight variables associated with litter decomposition to grazing or grazing intensity. We also explored whether experimental and environmental factors altered the effects of grazing on litter decomposition. Our results indicated that grazing significantly promoted litter decomposition when all the data was averaged, and that the magnitude of its effects on litter decomposition became weaker as grazing intensity increased. Grazing did not affect mixed root litter decomposition, but increased single root litter decomposition, and light grazing had a stronger positive effect. Specifically, grazing significantly accelerated litter C and P release, and significantly increased single N release by single above-ground litter, but not root or mixed aboveground litter. In addition, environmental factors (e.g., elevation, and mean annual precipitation) and experimental factors (e.g., experiment duration and litterbag size) affected the litter decomposition responses to grazing. These results suggest that the effects of grazing on litter decomposition and nutrient release depend on grazing intensity, litter type, and plant organs. Grazing alters terrestrial plant litter decomposition and grazing intensity plays an important role in regulating the magnitude of the effect during litter decomposition and nutrient cycling.

Contrasting dynamics and factor controls in leaf compared with different-diameter fine root litter decomposition in secondary forests in the Qinling Mountains after 5 years of whole-tree harvesting

Plant litter decomposition is a crucial pathway for carbon (C) and nutrient cycling, and controls the net primary productivity in ecosystems worldwide. However, little is known about how multi-type litter (leaf and different diameter fine roots) decomposition rates and nutrient release change at the community level following whole-tree harvesting (WTH). In the present study, we followed decomposition of leaf and different diameter fine root (∅ < 0.5 mm, 0.5–1 mm, 1–2 mm) litters at plot level over 2 years in a secondary forest in the Qinling Mountains after 5 years of five different thinning treatments (0%, 15%, 30%, 45%, and 60%). Our results demonstrated that WTH had no effects on leaf and different diameter fine root litter decomposition at the plot level. Leaves had significantly higher decomposition rate than different diameter fine roots. There were significant positive correlations between decomposition rate of different diameter fine roots, but not related to leaf litter decomposition rate. WTH did not affect the nutrient release of leaf and different diameter fine root litters at the plot level. The nitrogen (N), phosphorous (P) and potassium (K) mass remaining in leaf litters were significantly higher than different diameter fine roots after 2 years decomposition, while different diameter fine roots had higher C mass remaining. Leaf and fine root litter decomposition rates were mainly influenced by stand and litter quality attributes. Nutrient release of leaf and fine root N, P and K were mainly predicted by litter quality characteristics, while there were no consistent driving factors for C release. Our results suggested that WTH had no effects on multi-type litter decomposition and nutrient release at plot level after 5 years of recovery. Moreover, leaf litters had excellent N, P and K nutrient preservation mechanisms, and C conservation in fine root litters.

Litter Mixing Alters Microbial Decomposer Community to Accelerate Tomato Root Litter Decomposition.

ABSTRACTMixing plant litters of multiple species can alter litter decomposition, a key driver of carbon and nutrient cycling in terrestrial ecosystems. Changes in microbial decomposer communities is proposed as one of the mechanisms explaining this litter-mixture effect, but the underlying mechanism is unclear. In a microcosm litterbag experiment, we found that, at the early stage of decomposition, litter mixing promoted tomato root litter decomposition, thus generating a synergistic nonadditive litter-mixture effect. The transplanting decomposer community experiment showed that changes in microbial decomposer communities contributed to the nonadditive litter-mixture effect on tomato root litter decomposition. Moreover, litter mixing altered the abundance and diversity of bacterial and fungal communities on tomato root litter. Litter mixing also stimulated several putative keystone operational taxonomic units (OTUs) in the microbial correlation network, such as Fusarium sp. fOTU761 and Microbacterium sp. bOTU6632. Then, we isolated and cultured representative isolates of these two taxa, named Fusarium sp. F13 and Microbacterium sp. B26. Subsequent in vitro tests found that F13, but not B26, had strong decomposing ability; moreover, these two isolates developed synergistic interaction, thus promoted litter decomposition in coculture. Addition of F13 or B26 both promoted the decomposing activity of the resident decomposer community on tomato root litter, confirming their importance for litter decomposition. Overall, litter mixing promoted tomato root litter decomposition through altering microbial decomposers, especially through stimulating certain putative keystone taxa.IMPORTANCE Microbial decomposer community plays a key role in litter decomposition, which is an important regulator of soil carbon and nutrient cycling. Though changes in decomposer communities has been proposed as one of the potential underlying mechanisms driving the litter-mixture effects, direct evidence is still lacking. Here, we demonstrated that litter mixing stimulated litter decomposition through altering microbial decomposers at the early stage of decomposition. Moreover, certain putative keystone taxa stimulated by litter mixing contributed to the nonadditive litter-mixture effect. In vitro culturing validated the role of these taxa in litter decomposition. This study also highlights the possibility of regulating litter decomposition through manipulating certain microbial taxa.

Decoupled responses of leaf and root decomposition to nutrient deposition in a subtropical plantation

The decomposition of leaf and root litter plays an important role in the cycling of nutrients and carbon (C) in ecosystems. The long-term patterns of mass loss during leaf and root decomposition are well documented, but the long-term responses of mass loss and C quality during the decomposition of these two types of litter to the simultaneous deposition of exogenous nitrogen (N) and phosphorus (P) are not known. We compared the responses of the rate of mass loss, C quality, and the enzymatic and chemical properties of root and leaf litters in the early and late phases of decomposition to N and P addition in a subtropical plantation. N and P addition had delayed effects on root decomposition compared with leaf decomposition. The addition of N and P promoted leaf decomposition in the early phase likely by alleviating the P limitation of microorganisms, indicated by the higher P concentration and lower N/P ratio. The addition of N and P, however, stimulated the decomposition of root litter in the late phase, which was associated with increases in the concentrations of manganese and P in the root residues. The addition of N and P decreased the C quality of the leaf residue in the late phase but had little effect on the C quality of the root residue, even though N and P addition decreased the activity of acid phosphatase and increased the ratio of activities of β-glucosidase to acid phosphatase in the root residue. The decoupled responses of mass loss and C quality during leaf and root decomposition to N and P addition highlight the need to distinguish between leaf and root litter in the late phase of decomposition when evaluating the impact of atmospheric N and P deposition on the cycling of C and nutrients.

Mowing Facilitated Shoot and Root Litter Decomposition Compared with Grazing

Shoot and root litter are two major sources of soil organic carbon, and their decomposition is a crucial nutrient cycling process in the ecosystem. Altitude and land use could affect litter decomposition by changing the environment in mountain grassland ecosystems. However, few studies have investigated the effects of land use on litter decomposition in different altitudes. We examined how land-use type (mowing vs. grazing) affected shoot and root litter decomposition of a dominant grass (Bromus inermis) in mountain grasslands with two different altitudes in northwest China. Litterbags with 6 g of shoot or root were fixed in the plots to decompose for one year. The mass loss rate of the litter, and the environmental attributes related to decomposition, were measured. Litter decomposed faster in mowing than grazing plots, resulting from the higher plant cover and soil moisture but lower bulk density, which might promote soil microbial activities. Increased altitude promoted litter decomposition, and was positively correlated with soil moisture, soil organic carbon (SOC), and β-xylosidase activity. Our results highlight the diverse influences of land-use type on litter decomposition in different altitudes. The positive effects of mowing on shoot decomposition were stronger in lower than higher altitude compared to grazing due to the stronger responses of the plant (e.g., litter and aboveground biomass) and soil (e.g., soil moisture, soil bulk density, and SOC). Soil nutrients (e.g., SOC and soil total nitrogen) seemed to play essential roles in root decomposition, which was increased in mowing plots at lower altitude and vice versa at higher altitude. Therefore, grazing significantly decreased root mass loss at higher altitude, but slightly increased at lower altitude compared to mowing. Our results indicated that the land use might variously regulate the innate differences of the plant and edaphic conditions along an altitude gradient, exerting complex impacts in litter decomposition and further influencing carbon and nutrient cycling in mountain grasslands.

Stronger effect of litter quality than micro‐organisms on leaf and root litter C and N loss at different decomposition stages following a subtropical land use change

Abstract Litter decomposition contributes largely to global carbon (C) and nitrogen (N) cycling, and it is strongly determined by litter quality and microbial community composition in ways that are poorly understood. Here, we conducted a 2‐year field litter decomposition experiment by collecting leaf and root litter of crops (from cropland), shrubs (from shrubland) and wood (from woodland) and placing samples for decomposition in woodland soil in central China to investigate the effects of litter quality and microbial community composition on C and N losses of leaf and root litter of three species under different decomposition stages. Our results showed that the leaf litter C and N losses of shrubs were significantly higher than those of crops and wood, whereas the root litter C and N losses of crops were significantly higher than those of shrubs and wood. Generally, the leaf litter C and N losses of the three species were higher on average than those of fine root litter during the whole decomposition period. For the C loss of the three species, litter lignin and phosphorus as well as initial litter quality were predominant drivers of root litter decomposition, while litter lignin, cellulose and hemicellulose concentrations were dominant for leaf litter decomposition. For N loss, litter stoichiometry and litter quality directly governed leaf and root litter N loss, and the initial litter quality largely regulated N loss at the late decomposition stage. Unexpectedly, the effect of microbial community composition on litter C and N losses was relatively weak and only exhibited an effect on litter C and N losses during the early stage of decomposition. Thus, our results revealed the huge disparity in C and N loss of plant species and litter types at different decomposition stages, which should be considered jointly when evaluating their roles in plant–soil feedbacks under global land use change. A free Plain Language Summary can be found within the Supporting Information of this article.

Root Litter Decomposition Rates and Impacts of Drought are Regulated by Ecosystem Legacy

Root Litter Decomposition Rates and Impacts of Drought are Regulated by Ecosystem Legacy

Grazing directly or indirectly affect shoot and root litter decomposition in different decomposition stage by changing soil properties

Grazing can affect the grassland microclimate, soil properties, and litter quality, thereby affecting litter decomposition. However, it is still unclear which grazing intensity provides the most suitable environment for litter decomposition, and which factors play the dominant role in shoot and root litter decomposition. To investigate the effect of grazing on shoot and root litter decomposition, and the dominant factors in each decomposition period, we conducted a 17-month (from May 2016 to September 2017) litter bag experiment under five grazing intensities (control, light grazing, medium grazing, heavy grazing, and extremely heavy grazing, based on local grazing pressure standard) in a temperate grassland in Inner Mongolia, China. We divided the litter decomposition process into three stages according to the seasons. In the first growing season, the decomposition rate of shoot litter was faster under light grazing, probably because better soil environment was beneficial for microbes, and the high precipitation promoted leaching loss of soluble components. In the non-growing season, snow cover played an important role in litter decomposition. In the second growing season, the accumulation of macroelements (nitrogen, N; phosphorus, P) and microelements (magnesium, Mg; manganese, Mn) accelerated litter decomposition. Heavy and extremely heavy grazing intensities promoted the breakdown of cellulose in shoot litter. Medium grazing intensity could promote refractory substances decomposition in root litter. But the mass loss rate of root litter was inhibited by grazing, which was regulated by MBC/MBN. Our results indicate that different grazing intensities had different effects on the decomposition of shoot and root litter. At each stage of decomposition, the dominant factors of shoot and root litter decomposition were different and directly or indirectly affected by grazing and season.

Effects of sulfuric, nitric, and mixed acid rain on the decomposition of fine root litter in Southern China

BackgroundChina has been increasingly subject to significant acid rain, which has negative impacts on forest ecosystems. Recently, the concentrations of NO3− in acid rain have increased in conjunction with the rapid rise of nitrogen deposition, which makes it difficult to precisely quantify the impacts of acid rain on forest ecosystems.MethodsFor this study, mesocosm experiments employed a random block design, comprised of ten treatments involving 120 discrete plots (0.6 m × 2.0 m). The decomposition of fine roots and dynamics of nutrient loss were evaluated under the stress of three acid rain analogues (e.g., sulfuric (SO42−/NO3− 5:1), nitric (1:5), and mixed (1:1)). Furthermore, the influences of soil properties (e.g., soil pH, soil total carbon, nitrogen, C/N ratio, available phosphorus, available potassium, and enzyme activity) on the decomposition of fine roots were analyzed.ResultsThe soil pH and decomposition rate of fine root litter decreased when exposed to simulated acid rain with lower pH levels and higher NO3− concentrations. The activities of soil enzymes were significantly reduced when subjected to acid rain with higher acidity. The activities of soil urease were more sensitive to the effects of the SO42−/NO3− (S/N) ratio of acid rain than other soil enzyme activities over four decomposition time periods. Furthermore, the acid rain pH significantly influenced the total carbon (TC) of fine roots during decomposition. However, the S/N ratio of acid rain had significant impacts on the total nitrogen (TN). In addition, the pH and S/N ratio of the acid rain had greater impacts on the metal elements (K, Ca, and Al) of fine roots than did TC, TN, and total phosphorus. Structural equation modeling results revealed that the acid rain pH had a stronger indirect impact (0.757) on the decomposition rate of fine roots (via altered soil pH and enzyme activities) than direct effects. However, the indirect effects of the acid rain S/N ratio (0.265) on the fine root decomposition rate through changes in soil urease activities and the content of litter elements were lower than the pH of acid rain.ConclusionsOur results suggested that the acid rain S/N ratio exacerbates the inhibitory effects of acid rain pH on the decomposition of fine root litter.