Litter Chemical Traits Research Articles

Non-additive responses of litter decomposition, litter chemical traits, and soil C:N:P stoichiometry to mixing with Eucalyptus in plantation environments

Non-additive responses of litter decomposition, litter chemical traits, and soil C:N:P stoichiometry to mixing with Eucalyptus in plantation environments

High functional breadth of microbial communities decreases home-field advantage of litter decomposition

Home-field advantage (HFA) predicts that litter decomposes faster under its derived plant species. Growing evidence suggests that HFA depends on litter chemical traits and the microbiome's composition, but whether and how their interactions influence HFA effects has rarely been explored. Here, we conducted a reciprocal field transplantation experiment in a temperate forest to examine the effects of litter quality and microbial community composition on decomposition rates. We collected leaf litter from four dominant tree species (Pinus koraiensis, Tilla amurensis, Fraxinus mandshurica, and Acer mono) and utilized two mesh sizes (i.e., 0.5-μm and 35-μm) to manipulate the composition of decomposer communities (i.e., small-sized bacteria only or bacteria + fungi). We assessed the effects of HFA and the ability of decomposers to decay a wide range of litter, i.e., the functional breadth (FB). We found that HFA was stronger for recalcitrant litter in the fine-mesh litterbags. Low litter phosphorus (P) and nitrogen (N) content, explained the positive HFA effects when only small-sized bacteria were present during litter decomposition, but not when both bacteria and fungi were present. Soil parameters such as potassium content and dissolved organic carbon also significantly affected decomposer communities and contributed to the variability in HFA effects. Finally, the FB negatively correlated with HFA in coarse- and fine-mesh litterbags and accounted for 46 and 54% of the observed variation in HFA effects, respectively. Our results highlight that the interactive relationships between litter quality, soil properties, and the microbiome's composition, are central in understanding the functional abilities of microbes during litter decomposition, and suggest a tradeoff between the microbiome's capacity to degrade all litter efficiently and the specialization of decomposers toward their own litter. This further underscores the independent role of decomposers communities in litter decomposition rates, which should be considered when predicting biogeochemical cycling in forest ecosystems.

Alterations in litter chemical traits and soil environmental properties limit the litter decomposition of near-mature Robinia pseudoacacia plantations

Increases in stand age can significantly change litter and soil microenvironmental properties of plantations. However, how these factors change and by which pathways they act together to affect litter decomposition are not well understood. In this study, litters were collected from four Robinia pseudoacacia (Rp) plantations from a 10 ∼ 43-year sequence in the Loess Plateau (China) and used to conduct a 592-day in-situ decomposition experiment using litterbag method. The changes in litter chemical traits, soil physiochemical environment, and the litter and soil microbial community were detected. Then, the pathways of these changes affecting litter decomposition were analyzed based on partial least squares structural equation modeling. The results indicated that with increasing stand age, the increased litter substrate quality stimulated litter lignocellulase activity by affecting the fungal community structure in early and late stages of decomposition and the bacterial community structure in early decomposition, which tended to accelerate litter decomposition. However, the decrease in litter chemical diversity weakened the synergistic effects of mixed litter decomposition, and thus directly hindered the overall decomposition. On the other hand, increasing stand age caused excessive soil temperature and low soil moisture in early decomposition stage, which indirectly affected the litter microbial communities through changes in the soil fungal community, leading to decreases in litter lignocellulase activity and litter decomposition. Overall, changes in litter chemical traits with increasing stand age tended to cause dual effects, while those in the soil microenvironment tended to cause increasing negative effects. Together these changes finally affected litter decomposition by litter microbes and their enzymatic activities, leading to depressed litter decomposition and a risk of weakening material cycling in near-mature (33-year) Rp plantations.

Forest plantation diversification with Leguminosae tree species: Consequences on litter decomposition and nutrient recycling

AbstractMixed tree plantations provide greater ecosystem services than monocultures. Leguminosae tree species can be appropriate complements to achieve a sustainable soil management target. A key aspect of species trait complementarity is the litter mixture effects in the litter decomposition process. We evaluated how the mixture of poplar litter (Populus deltoides Marsh.) with Leguminosae tree species modulated the litter decomposition process and C, N and P recycling, through changes driven by the Leguminosae litter chemical traits. Under field conditions, we compared poplar litter alone (monoculture) with its 50:50 mixture with Enterolobuim contortisiliquum (Vell.) Morong., or Peltophorum dubium (Spreng.). Compared to poplar litter, its mixture with E. contortisiliquum had a 25% lower C:N ratio and a similar N:P ratio, whereas mixture with P. dubium had a 9% lower C:N and a 29% lower N:P ratios. The mixture with E. contortisiliquum showed a 64% faster decomposition rate, and 55% and 203% faster C and N release rates, respectively, compared to poplar. In contrast, in the mixture with P. dubium, there was no difference in the litter, C and N decay rates with poplar litter alone. The mixture with P. dubium had a 37% lower P retention compared to poplar, whereas P was released rather than retained in the mixture with E. contortisiliquum. The mixture with E. contortisiliquum showed a net antagonistic effect in the litter decomposition rate. However, in the mixture, poplar litter decomposed 33% faster and the E. contotrtisiliquum litter decomposed 35% slower than species alone. The C:N and N:P ratios in the litter mixture were relevant traits shaping the magnitude and direction of litter decomposition and nutrient recycling processes. The incorporation of both Leguminosae to monospecific poplar plantations could contribute to counteract P limitation in this system and to improve soil fertility and functioning.

Litter chemical traits, microbial and soil stoichiometry regulate organic carbon accrual of particulate and mineral-associated organic matter

Litter chemical traits, microbial and soil stoichiometry regulate organic carbon accrual of particulate and mineral-associated organic matter

Plant litter chemistry drives long‐lasting changes in the catabolic capacities of soil microbial communities

Abstract 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.

Leaf litter chemistry and its effects on soil microorganisms in different ages of Zanthoxylum planispinum var. Dintanensis

BackgroundLeaf litter is the products of metabolism during the growth and development of plantation, and it is also an important component of nutrient cycling in plantation ecosystems. However, leaf litter chemistry and its effects on soil microorganisms in different ages, as well as the interactions between chemical components in leaf litter have been rarely reported. Based on this, this paper took Zanthoxylum planispinum var. dintanensis (hereafter Z. planispinum) plantations of 5–7, 10–12, 20–22, and 28–32 years old as the objects. By using one-way ANOVA, Pearson correlation analysis and redundancy analysis, we investigated leaf litter chemistry and its effects on soil microorganisms in different ages, and to reveal internal correlation of various chemical components in leaf litter, which can provide a scientific basis for the regulation of soil microbial activity in plantations.ResultsThe variation of organic carbon with plantation age was more stable compared to total nitrogen and phosphorus of leaf litter. Nitrogen resorption was stronger than phosphorus resorption efficiency in Z. planispinum, and resorption efficiencies of leaf nitrogen and phosphorus for different ages were lower than the global average. Total nitrogen was highly significantly positively correlated with lignin, and total potassium was significantly positively correlated with tannin, suggesting the increase of inorganic substances in leaf litter would promote the accumulation of secondary metabolites. The leaf litter chemical traits explained up to 72% of soil microorganisms, where lignin was positively correlated with fungi and negatively correlated with bacteria, indicating that fungi are able to decompose lower quality litter and can break down complex and stable organic compounds more rapidly than bacteria. The nutrient elements carbon and nitrogen in the leaf litter and their interrelationship also have a great impact on soil microorganisms, because carbon is not only the element that provides energy, but also the element with the largest content in the microbiota.ConclusionsThe sustained increase in inorganic nutrients of leaf litter did not favor the decomposition of secondary metabolites, but rather inhibited the degradation of leaf litter. The significant positive effect of the leaf litter chemistry on soil microorganisms indicates the important role of leaf litter in promoting nutrient cycling in Z. planispinum plantations.

Impacts of plant domestication on soil microbial and nematode communities during litter decomposition

PurposePlant domestication altered leaf litter quality. Since litter traits relate to soil functions and organisms (i.e., litter decomposition and soil decomposer communities), in this study we explore if domestication-induced changes in litter quality have affected their decomposability, and bacterial, fungal, and nematode communities in the soil.MethodsWe collected leaf litter from herbaceous crops and their wild progenitors, and measured litter chemical and physical traits. Then, we performed a litter decomposition assay on a common soil. After three months of litter incubation, we measured mass loss, nematode richness and community composition in ten crops. We also measured soil bacterial and fungal richness and community composition in six crops.ResultsDomesticated litters had less carbon (C) and leaf dry matter content (LDMC), which accelerated decomposition in comparison to wild litters. Fungal richness was higher in microcosms incubated with domesticated litters, while the effects of domestication on bacterial richness differed among crops. Domestication did not affect nematode richness. The effects of domestication on bacterial and fungal community compositions differed among crops. Soils with domesticated litters tended to have nematode communities with a higher abundance of bacterial feeding nematodes, in comparison to soils fed with wild litters.ConclusionDomestication altered decomposition at different levels. Leaf litter decomposability increased with domestication, which might alter resource inputs into the soil. Feeding soils with domesticated litters had idiosyncratic effects on soil microbes, but consistent effects on soil nematodes. Overall, domestication altered the linkages between crop residues and soil communities differently for bacteria, fungi, and nematodes.

Asymmetric responses of leaf litter decomposition to precipitation changes in global terrestrial ecosystem

Climate change-induced alterations in precipitation regimes can substantially impact litter decomposition and consequently affect carbon (C) and nutrient cycling in terrestrial ecosystems. However, the response patterns of litter decomposition to precipitation changes and their controlling factors remain ambiguous. We conducted a global meta-analysis to examine the responses of leaf litter decomposition and their sensitivities to increased precipitation (IP) and decreased precipitation (DP) based on 68 publications with 2940 paired observations in field litterbag experiments. We further explored how responses of litter decomposition varied with the intensity and timing of precipitation changes, ecosystem type, climatic conditions, litter traits, decomposition duration, and soil fauna. Litter decomposition showed double-asymmetric responses to precipitation changes. On a global scale, IP enhanced litter decomposition on average by 16%, whereas DP reduced litter decomposition by 21%. Litter decomposition was more sensitive to IP than DP at low precipitation changes but exhibited a greater response to DP than IP at extreme precipitation changes. In addition, litter decomposition in forests showed a stronger response to precipitation changes than that in other ecosystems, and litter decomposition was more sensitive to precipitation change under warm and wet conditions. Compared to precipitation changes in the growing season, litter decomposition showed a stronger response to IP but exhibited no response to DP in the non-growing season. The impacts of precipitation change gradually decreased with ongoing litter decomposition. Moreover, the initial lignin concentration in litter primarily determined the responses of litter decomposition to precipitation changes, with litter mixture and soil fauna partially mitigating the precipitation change effects. Our meta-analysis extends the double asymmetry model regarding the responses of litter decomposition to precipitation changes, which vary with ecosystem type, climatic conditions, litter chemical traits, decomposition duration, and soil fauna. These findings improve our ability to project the responses of terrestrial C and nutrient cycling to global precipitation changes.

Effects of litter chemical traits and species richness on soil carbon cycling changed over time

Litter decomposition is the main driver of nutrient cycling process in terrestrial ecosystems. Afforestation completely altered vegetation composition and litter species, disrupting the long-term carbon balance in grassland ecosystem. However, there is a lack of understanding of how litter mixing effect (LME) affects soil carbon cycling in afforested ecosystem. Here, we investigated the effects of litter richness and quality of tree, shrub, and grass species and their litter mixture on soil CO2 fluxes. The results showed that cumulative soil CO2 flux in the early stage (1–28 days) was 1.75 times higher than that in the late stage (29–113 days), indicating litter decomposition was intensive at first and then decreased with time. Soil carbon flux changed with decomposition stages. In the early-stage of decomposition, soil CO2 flux increased with the concentrations of litter carbon, nitrogen and condense tannin. In the late phase of decomposition, all litter chemical traits were negatively related to the soil carbon flux. Additionally, plant litter richness was negatively correlated to early-stage soil CO2 flux, whereas it was positively related to late-stage soil carbon flux. Our results provide evidence that long-term carbon balance in grassland ecosystems was interrupted by afforestation, and the dominant litter chemical traits that controlling soil carbon cycling changed over time.

Plant litter chemistry controls coarse‐textured soil carbon dynamics

Abstract As soils store more carbon (C) than the Earth's atmosphere and terrestrial biomass together, the balance between soil C uptake in the form of soil organic matter (SOC) and release as CO2 upon its decomposition is a critical determinant in the global C cycle regulating our planet's climate. Although plant litter is the predominant source of C fuelling both soil C build‐up and losses, the issue of how litter chemistry influences this balance remains unresolved. As a contribution to solving that issue, we traced the fate of C during near‐complete decomposition of 13C‐labelled leaf and root litters from 12 plant species in a coarse‐textured soil. We separated the soil organic carbon into mineral‐associated organic matter (MAOM) and particulate organic matter (POM) pools, and investigated how 14 litter chemical traits affected novel SOC formation and native SOC mineralization (i.e. the priming effect) in these soil fractions. We observed an overall net increase in SOC due to the addition of litter, which was stronger for root than for leaf litters. The presumed stable MAOM‐C pool underwent both substantial stabilization and mineralization, whereas the presumably less stable POM‐C pool showed substantial stabilization and reduced mineralization. Overall, the initial increase in soil C mineralization was fully counterbalanced by a later decrease in native soil C mineralization. POM‐C formation as well as MAOM‐C formation and mineralization were positively related to the initial litter lignin concentration and negatively to that of the nitrogen leachates, whereas the opposite was observed for POM‐C mineralization. Synthesis. Our results highlight the importance of litter chemical traits for SOC formation, and stabilization, destabilization and mineralization. In our coarse‐textured soil, the amount of MAOM‐C did not change despite large C fluxes through this pool. The litter chemical traits that drove these processes differed from those frequently reported for fine‐textured soils far from mineral‐associated C saturation. To account for these discrepancies, we propose an integrative perspective in which litter quality and soil texture interactively control soil C fluxes by modulating several SOC stabilization and destabilization mechanisms. Irrespective, our results open new critical perspectives for managing soil C pools globally.

Forest Litter Chemical Traits and Microbial Stoichiometry Regulate the Formation and Stabilization of Soil Organic Matter

Forest Litter Chemical Traits and Microbial Stoichiometry Regulate the Formation and Stabilization of Soil Organic Matter

Forest degradation and short-term seasonal exclosure effects on biotic and abiotic factors linked to rangeland rehabilitation in semiarid Chaco, Argentina

In semiarid Chaco, wet season grazing exclosures allow a rapid grass recovery in mature and secondary forest patches, but not in the most degraded patches dominated by shrublands. In order to understand the causes of their dissimilar rehabilitation dynamics, we analyzed the effects of the forest-patch type (mature forest = MF, secondary forest = SF, and shrubland = S) and 4-year seasonal exclosures (vs continuous grazing) on biotic and abiotic factors (vegetation structure, incident radiation, grass seed bank, litter and soil traits) that could affect grass recovery. We found that vegetation structure, through determining litter quantity, controlled soil chemical traits. As forest degradation level increased, litter mass (MF = 6260, SF = 5410, S = 1220 kg DM/ha), total soil organic matter (MF = 5.1%, SF = 4.1%, S = 3.5%) and nitrogen (MF = 0.25%, SF = 0.22%, S = 0.18%) decreased, and the incident radiation at soil level rose (MF = 28%, SF = 41%, S = 52%). After 4 years of seasonal grazing rest, we found reduced soil bulk density (from 1.13 to 1.07 and 1.07 to 1 g/cm3) and increased total porosity (from 57 to 60 and 60 to 62%) at 0–10 and 10–30 cm depth, respectively, in all forest patch types. Exclosure also increased soil seed bank density (from 28 to 251 grass seeds/m2) both in the forests (with grass) and in the shrublands (even before grass recovery), which would receive seeds from the adjacent forest patches, which coexist in the same landscape matrix. Our results suggest that the low tree cover, litter, and soil chemical traits related to lower availability of water and nutrient in shrublands, could hamper grass recovery in recently established exclosures. However, improvements in the grass seed bank and soil physical traits related to higher water infiltration could favor its late recovery, which is triggered by an extremely wet cycle after several years of the seasonal exclosure. Exclosure is a promising management strategy for degraded areas involving intermingled patches of forests and shrublands.

Litter chemical traits strongly drove the carbon fractions loss during decomposition across an alpine treeline ecotone

The decomposition of litter carbon (C) fraction is a major determinant of soil organic matter pool and nutrient cycling. However, knowledge of litter chemical traits regulate C fractions release is still relatively limited. A litterbag experiment was conducted using six plant functional litter types at two vegetation type (coniferous forest and alpine shrubland) in a treeline ecotone. We evaluated the relative importance of litter chemistry (i.e. Nutrient, C quality, and stoichiometry) on the loss of litter mass, non-polar extractables (NPE), water-soluble extractables (WSE), acid-hydrolyzable carbohydrates (ACID), and acid-unhydrolyzable residue (AUR) during decomposition. Litter nutrients contain nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), sodium (Na), magnesium (Mg), aluminium (Al), manganese (Mn), zinc (Zn), iron (Fe) and copper (Cu), litter C quality contains C, WSE, NPE, ACID, and AUR, and stoichiometry was defined by C:N, C:P; N:P, ACID:N, and AUR:N. The results showed single exponential model fitted decomposition rates of litter mass and C fractions better than double exponential or asymptotic decomposition, and the decomposition rates of C fractions were strongly correlated with initial litter nutrients, especially K, Na, Ca. Furthermore, the temporal dynamics of litter nutrients (Ca, Mg, Na, K, Zn, and Fe) strongly regulated C fractions loss during the decomposition process. Changes in litter C quality had an evident effect on the degradation of ACID and AUR, supporting the concept of “priming effect” of soluble carbon fraction. The significant differences were found in the release of NPE, WSE, and ACID rather than AUR among coniferous forest and alpine shrubland, and the vegetation type effects largely depend on the changes in litter stoichiometry, which is an important implication for the change in plant community abundance regulate decay. Collectively, elucidating the hierarchical drivers of litter chemistry on decomposition is critical to soil C sequestration in alpine ecosystems.

Liming of acidified forests changes leaf litter traits but does not improve leaf litter decomposability in forest streams

Liming, the spreading of Ca/MgCO3 on terrestrial ecosystems, is often used as a way to promote the recovery of terrestrial and aquatic ecosystems affected by anthropogenic acidification. When liming is applied to a watershed, surface waters may be improved directly through water chemistry changes but also indirectly through possible changes in the quality of terrestrial organic matter inputs to the stream. The aim of this study was to evaluate the effect of liming on leaf litter chemical and structural traits and their consequences on another trait, leaf litter decomposability, giving the potential for a leaf litter to be decomposed.Beech (Fagus sylvatica, L.) leaf litter was collected in forested sites on acid bedrock (granite and sandstone), limed (9 or 21 years ago) or not (controls), as well as on two calcareous reference sites. Several leaf litter traits were determined for each collection site: carbon (C), nitrogen (N), phosphorous (P), calcium (Ca), magnesium (Mg), potassium (K), lignin and cellulose content, and leaf mass area and toughness. To compare leaf litter decomposability in aquatic ecosystem, leaf litters from all sites were placed in a reference forested headwater stream over a 128-day period, in fine and coarse mesh litter bags, and leaf mass loss dynamic as well as fungal biomass were evaluated.Liming significantly increased leaf litter Ca and Mg contents and decreased K content while other measured traits remained unchanged. Leaf litters collected in limed sites exhibited significantly lower decomposition rates in coarse mesh bags but similar decomposition rates in fine mesh bags. Liming had no significant effect on fungal biomass. In contrast, leaf litter collected on the calcareous, reference sites, showed significantly different trait profiles (e.g. higher Ca, Mg, K and P contents), leading to up to twice higher decomposition rates and fungal development.Our study shows that under our experimental conditions, increases in Ca and Mg leaf litter contents arising from acidic forests liming did not improve leaf litter microbial decomposition and even tended to reduce macroinvertebrate mediated decomposability. Concomitant changes in other leaf litter traits might be necessary to stimulate leaf litter decomposition. Liming with Ca/MgCO3 might thus not improve functional recovery of stream ecosystems in forests affected by acidification through an increase of litter quality.

Increasing Precipitation Interval Has More Impacts on Litter Mass Loss Than Decreasing Precipitation Amount in Desert Steppe

Litter mass loss and nutrient release are key links in the material cycling and energy flowing in ecosystems and of special ecological significance in maintaining ecosystem stability, improving soil structure and promoting vegetation restoration in the arid and semi-arid regions. Furthermore, litter mass loss could be affected by the change in precipitation patterns. However, currently, most studies on the response of litter mass loss to precipitation pattern change focus on the precipitation amount much more than the precipitation frequency. Therefore, we conducted a three-year manipulative research in a desert steppe to assess the effects of decreasing precipitation amount and increasing precipitation interval on the litter mass loss of Stipa klemenzii, and their relationships with litter chemical traits (contents of carbon (C), nitrogen (N), phosphorus (P), potassium (K), lignin and ash, C/N ratio and lignin/N ratio) and abiotic factors (light intensity and temperature and humidity of soil and air). The results showed that (1) both the treatments have negative effects on litter mass loss; (2) for abiotic factors, both the treatments only affected soil moisture; for biotic factors, both the treatments decreased the litter lignin contents, the increased precipitation interval treatment decreased the litter N and K contents while increased the litter C/N ratio and lignin/N ratio; (3) the main control of litter mass loss was due to our manipulation of drought regime and its effects on the soil decomposition environment, rather to other factors such as litter quality or light intensity; (4) compare to decreased precipitation amount, increased precipitation interval has more impact on litter mass loss, and this was caused by the increased litter C/N ratio in increased precipitation interval treatment. We speculated that increased precipitation interval was a harsher abiotic factor for the decomposer, and more research on this should be conducted in the future.

Short- and Long-Term Effects of Snow-Depth on Korean Pine and Mongolian Oak Litter Decomposition in Northeastern China

Changes in snow-depth induced by climate change can affect litter decomposition, but it remains unclear whether the effects of snow-depth on litter decomposition vary among seasons. Our aim was to assess the possible short- and long-term effects of snow-depth on foliar litter decomposition for Korean pine (Pinus koraiensis) and Mongolian oak (Quercus mongolica). A snow-depth manipulation experiment that included snow-removal, control and snow-addition treatments was conducted in northeastern China. All the snowfall was intercepted by transparent plexiglass in the snow-removal treatment and then transferred to the snow-addition treatment. Three replicate litterbags per species were buried in each treatment and sampled in the freezing onset, deep freezing and thawing stages and in the early, middle and late snow-free seasons from November 2014 to October 2015. Our results showed that the oak litter decomposed faster than the pine litter, but the magnitude of the effect of snow-depth was greater for the latter because of differences in litter chemical traits. Litter mass loss decreased with decreasing snow-depth in the snow-covered season but increased in the following snow-free season. The short-term effect resulting from the changes in soil environments affected litter decomposition during the snow-covered season, while the long-term effect due to litter chemical traits and the microbial biomass carbon concentration controlled the decomposition in the snow-free season. These results indicated that snow-depth significantly influences the foliar litter decomposition of the two tree species with contrasting initial qualities, but the effects differed between the snow-covered and snow-free seasons. These results deepen our understanding of biogeochemical cycling in cold regions.

Decomposition time, chemical traits and climatic factors determine litter-mixing effects on decomposition in an alpine steppe ecosystem in Northern Tibet

In the context of rapid species diversity loss, whether and how species diversity affects litter decomposition in alpine ecosystems remain unclear. Here, we aimed to assess the impact of litter mixing on decomposition and the influencing factors of such litter-mixing effects (LMEs). We incubated the litter of four alpine steppe species in monocultures and all possible litter combinations and analysed the mass remaining over three years. Litter mixing showed more frequent antagonistic effects than synergistic effects in the early stage of the experiment; however, the LME might change from antagonistic to synergistic at the latter stage of incubation. The magnitude of the LMEs increased as decomposition progressed. The four-species mixture resulted in more antagonistic effects, while the magnitude of the non-additive effects showed no relationship with species richness. Litter chemical traits and climatic factors affected the direction and magnitude of the non-additive effects, but these influences were time-dependent. Additionally, the fast-decomposing and slow-decomposing litter species had negative and positive responses to the litter mixture, respectively. Our results demonstrate that the LME was determined by decomposition time, chemical traits and climatic factors and suggest that assessing the relative individual performances of the litter components in a mixture is an important way to examine the mechanisms underlying LMEs.

Litter carbon and nutrient chemistry control the magnitude of soil priming effect

Abstract Plant litter inputs can promote the decomposition of soil organic matter (OM) through the priming effect (PE). However, whereas leaf litter chemistry has long been identified as the primary driver of litter decomposition within biomes world‐wide, little is known about how litter chemical traits influence the occurrence and strength of the PE. Here, we studied the effects of 15 co‐occurring C3 leaf litters of contrasting chemistry on C4 soil respiration by analysing changes in 13C natural abundance during early and later stages of litter decomposition (up to 125 days). Besides an apparent PE of 16% in the first 3 days, soil C respiration was increased by 24% on average with leaf litter addition in the initial stage of decomposition (4–26 days) and by 8% at later stages (27–125 days). Most interestingly, soil PE related well to initial litter chemistry and the dominant factors influencing the magnitude of the PE changed with decomposition stage. In the early stage of decomposition, litter leachate C content and litter hemicellulose concentration were positively correlated with the strength of the PE, whereas tannin concentration was negatively associated with soil PE. Together, tannin and hemicellulose explained half of the observed variation in the PE (R2 = 0.58). In the later phase of decomposition, lignin and lignin:N ratios were negatively related to the PE, whereas Ca, K and Mg concentrations were positively related to the PE; lignin alone gave the best prediction of the PE (R2 = 0.58) at later decomposition stages. Our findings provide evidence that the magnitude and direction of the PE is influenced by the chemistry of OM inputs and suggest that, as decomposition proceeds differently among litter of contrasting chemistry, litters can also have variable effect on soil PE through time. The predictive power of litter chemical traits on soil PE opens new perspectives for improving our mechanistic understanding of soil PE and improving our abilities to model soil C dynamics at variable scales. A plain language summary is available for this article.

Soil C and N dynamics and their non-additive responses to litter mixture under different moisture conditions from an alpine steppe soil, Northern Tibet

Although there is a strong consensus that biodiversity can influence ecosystem functioning, how litter diversity affects soil ecological processes in different climatic contexts has been rarely studied. Here, we employed a mixed-litters’ experiment to examine how mixed-litters decomposition affects soil carbon (C) and nitrogen (N) dynamics under different moisture conditions from an alpine steppe soil in Northern Tibet. Litter of alpine steppe species, in monoculture or combination, were mixed with soil in 20%, 30% and 40% water holding capacities (WHC) in microcosms. During each microcosm incubation, we measured CO2 emissions, soluble organic carbon (SOC), total inorganic N (TIN) and microbial biomass C (MBC). Our results showed that CO2, SOC, TIN and MBC differed significantly among litter treatments and soil moisture. In the litter mixture, frequent and unsystematic non-additive effects could be found in CO2, SOC, TIN and MBC, and the non-additivities could be explained by the litter chemical traits. Higher soil moisture strengthened the synergistic effects of litter-mixing on CO2 and antagonistic effects on TIN, while weaken the synergistic effect on SOC and the antagonistic effects on MBC. This result indicated that, under multiple litter species decomposition, a changing soil moisture from dry to wet generally accelerate CO2 emission and increase MBC, while decrease the accumulation of SOC and TIN. Our work demonstrated that soil C and N dynamics and their non-additive responses to litter mixture were climatic context dependent. Soil moisture condition should be considered in understanding the effects of litter diversity on soil C and N processes.