Accelerate Litter Decomposition Research Articles

Short-term responses of soil enzyme activities and stoichiometry to litter input in Castanopsis carlesii and Cunninghamia lanceolata plantations.

Litter input triggers the secretion of soil extracellular enzymes and facilitates the release of carbon (C), nitrogen (N), and phosphorus (P) from decomposing litter. However, how soil extracellular enzyme activities were controlled by litter input with various substrates is not fully understood. We examined the activities and stoichiometry of five enzymes including β-1,4-glucosidase, β-D-cellobiosidase, β-1,4-N-acetyl-glucosaminidase, leucine aminopeptidase and acidic phosphatase (AP) with and without litter input in 10-year-old Castanopsis carlesii and Cunninghamia lanceolata plantations monthly during April to August, in October, and in December 2021 by using an in situ microcosm experiment. The results showed that: 1) There was no significant effect of short-term litter input on soil enzyme activity, stoichiometry, and vector properties in C. carlesii plantation. In contrast, short-term litter input significantly increased the AP activity by 1.7% in May and decreased the enzymatic C/N ratio by 3.8% in August, and decreased enzymatic C/P and N/P ratios by 11.7% and 10.3%, respectively, in October in C. lanceolata plantation. Meanwhile, litter input increased the soil enzymatic vector angle to 53.8° in October in C. lanceolata plantations, suggesting a significant P limitation for soil microorganisms. 2) Results from partial least squares regression analyses showed that soil dissolved organic matter and microbial biomass C and N were the primary factors in explaining the responses of soil enzymatic activity to short-term litter input in both plantations. Overall, input of low-quality (high C/N) litter stimulates the secretion of soil extracellular enzymes and accelerates litter decomposition. There is a P limitation for soil microorganisms in the study area.

Deepened snow cover accelerates litter decomposition by stimulating microbial degradation

Changing precipitation patterns and global warming have greatly changed winter snow cover, which can affect litter decomposition process by altering soil microenvironment or microbial biomass and activity. However, it remains unknown how and to what extent snow cover affects litter decomposition during winter and over longer periods of time. Here, we conducted a meta-analysis to synthesize litter decomposition studies under different levels of snow cover. Overall, deepened snow significantly enhanced litter decomposition rate and mass loss by 17% and 3%, respectively. Deepened snow enhanced litter carbon loss by 7% but did not impact the loss of litter nitrogen or phosphorus. Deepened snow increased soil temperature, decreased the frequency of freeze-thaw cycles, and stimulated microbial biomass carbon and bacterial biomass during winter, but had no effect on these parameters in summer. The promoting effect of deepened snow cover on litter decomposition in winter is mainly due to its positive effect on microbial decomposition by increasing soil temperature and reducing freeze-thaw cycles exceeded its negative effect on physical fragmentation of litter by reducing freeze-thaw cycles. Our findings indicate that the changes in winter snow cover under global change scenarios can greatly impact winter litter decomposition and the associated carbon cycling, which should be taken into consideration when assessing the global carbon budget in modeling.

The effect of litter decomposition mostly depends on seasonal variation of ultraviolet radiation rather than species in a hyper-arid desert

Introduction: Ultraviolet (UV) radiation is believed to play a significant role in accelerating litter decomposition in water-limited ecosystems. Litter traits also influence the decomposition. However, the dominance of litter traits and ultraviolet radiation on litter decomposition in hyper-arid deserts (annual precipitation: potential evaporation < 0.05) with diverse species and seasonal variations remain unclear.Methods: To address this knowledge gap, we examined the decomposition of three dominant litter species (Karelinia caspia, Alhagi sparsifolia, and Populus euphratica) in the southern edge of the Taklimakan Desert, Northwest China.Results: Our results revealed that under UV radiation conditions, K. caspia, A. sparsifolia, and P. euphratica experienced mass losses of 45.4%, 39.8%, and 34.9%, respectively, and 20%, 22.2% and 17.4%, respectively under UV filtering treatment. Specifically, the loss rate of carbon and lignin under UV radiation, was 2.5 and 2.2 times higher than under UV filtering treatment, respectively.Conclusion: UV radiation did not dominate decomposition throughout the year in our study area, and the loss rate of litter traits was significantly higher in summer than in winter under UV radiation. Moreover, this photodegradation is related to the intensity of UV exposure, but not to precipitation or temperature. Surprisingly, species type had no significant effect on litter decomposition. However, when we applied a UV filtering treatment, we observed higher loss rates of nitrogen compared with the ambient treatment, suggesting the involvement of other spectra in the litter decomposition process. Overall, our findings elucidate that UV radiation is a crucial factor that affects litter mass loss. The magnitude of this effect mostly varies with the season rather than the species of litter.

Moss removal facilitates decomposition and net nitrogen loss of monospecific and mixed-species litter in a boreal peatland

AbstractLitter decomposition plays an important role in biogeochemical cycling in boreal peatlands, where mosses, especially Sphagnum species, are a determinant. In recent decades, these peatlands have experienced a decline in moss cover due to abrupt climate warming and atmospheric nitrogen (N) deposition. To reveal the effect of the reduction in moss cover on litter decomposition, we adopted a field living moss removal experiment (with the senesced tissues remaining) in a Sphagnum-dominated boreal peatland, and investigated litter mass loss and net N loss of three deciduous woody species decomposing in monocultures and mixtures over 3 years. Based on the observed and predicted mass loss and net N loss of litter mixtures, we divided litter mixing effects into additive (no significant difference), synergistic (observed value greater than predicted value), and antagonistic (observed value lower than predicted value) effects. Across 3 years of decomposition, moss removal increased litter mass loss and net N loss, irrespective of single- or mixed-species compositions. Moss removal generally changed litter mixing effects on mass loss from antagonistic to additive effects in the initial 2 years, but from synergistic to additive effects after 3 years of decomposition. Regarding net N loss of litter mixtures, moss removal often resulted in a shift from additive to synergistic effects or from antagonistic to additive effects after 2 and 3 years of decomposition. Our observations suggest that the declines in living moss cover can accelerate litter decomposition and nutrient release, and highlight that living moss loss makes litter mixture decomposition predictable by reducing non-additive effects in boreal peatlands. Given the widespread occurrence of reduced moss cover in boreal peatlands, the mechanisms explaining living moss controls on litter decomposition and N cycling should receive significant attention in further studies.

Nitrogen addition accelerates litter decomposition and arsenic release of Pteris vittata in arsenic-contaminated soil from mine

The arsenic (As) release from litter decomposition of As-hyperaccumulator (Pteris vittata L.) in mine areas poses an ecological risk for metal dispersion into the soil. However, the effect of atmospheric nitrogen (N) deposition on the litter decomposition of As-hyperaccumulator in the tailing mine area remains poorly understood. In this study, we conducted a microcosm experiment to investigate the As release during the decomposition of P. vittata litter under four gradients of N addition (0, 5, 10, and 20 mg N g−1). The N10 treatment (10 mg N g−1) enhanced As release from P. vittata litter by 1.2–2.6 folds compared to control. Furthermore, Streptomyces, Pantoea, and Curtobacterium were found to primarily affect the As release during the litter decomposition process. Additionally, N addition decreased the soil pH, subsequently increased the microbial biomass, as well as hydrolase activities (NAG) which regulated N release. Thereby, N addition increased the As release from P. vittata litter and then transferred to the soil. Moreover, this process caused a transformation of non-labile As fractions into labile forms, resulting in an increase of available As concentration by 13.02–20.16% within the soil after a 90-day incubation period. Our findings provide valuable insights into assessing the ecological risk associated with As release from the decomposition of P. vittata litter towards the soil, particularly under elevated atmospheric N deposition.

The urban heat island accelerates litter decomposition through microclimatic warming in temperate urban forests

The urban heat island accelerates litter decomposition through microclimatic warming in temperate urban forests

Climate warming enhances microbial network complexity by increasing bacterial diversity and fungal interaction strength in litter decomposition

Microbial communities are important drivers of plant litter decomposition; however, the mechanisms of microbial co-occurrence networks and their network interaction dynamics in response to climate warming in wetlands remain unclear. Here, we conducted a 1.5-year warming experiment on the bacterial and fungal communities involved in litter decomposition in a typical wetland. The results showed that warming accelerated the decomposition of litter and had a greater effect on the diversity of bacteria than on that of fungi. Dominant bacterial communities, such as Bacteroidia, Alphaproteobacteria, and Actinobacteria, and dominant fungal communities, such as Leotiomycetes and Sordariomycetes, showed significant positive correlations with lignin and cellulose. Co-occurrence networks revealed that the average path length and betweenness centrality under warming conditions increased in the bacterial community but decreased in the fungal community. Both bacterial and fungal networks in the 2.0 °C warming treatment had the highest ratio of positive links (58.53 % and 98.14 %), indicating that moderate warming can promote the positive correlations and symbiotic relationships observed in the microbial community. This also suggests that small-world characteristics and weak-link advantages accelerate diffusion, and scale-free features facilitate propagation in microbial communities in response to climate warming. Logistic growth and Lotka-Volterra competition models revealed that climate warming enhances microbial network complexity mainly by increasing bacterial diversity and fungal interaction strength in litter decomposition. However, the symbiotic relationship decreased slightly under 4.0 °C warming, indicating that climate warming is a random attack rather than a targeted attack, and the microbial network has strong resistance to random attack, as shown by the highly robust dynamic performance of the microbial network in litter decomposition. Overall, the microbial community in litter decomposition responded to climate warming and shifted its network interactions, leading to further changes in emergent network topology and dynamics, thus accelerating litter decomposition in wetlands.

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.

Contrasting Effects of Leaf Litter Quality and Diversity on Oviposition of Mosquitoes.

The quality and diversity of leaf litter are important variables in determining the availability of energy in detritus-based food webs. These factors can be represented by the stoichiometric proportion between carbon and multiple nutrients, and the mixture of litter from different taxonomic and/or functional origins. In aquatic ecosystems, factors that accelerate litter decomposition can influence the secondary productivity of planktonic microbiota, which act as a link between litter and higher trophic levels. This study aimed to analyze the influence of litter quality and diversity on the oviposition behavior of medically important mosquitoes. We hypothesized that both factors would have a positive effect on the attraction of female mosquitoes and would stimulate a greater amount of oviposition. To test this hypothesis, microcosms containing isolated leaf litter leachates from four plant species were used to manipulate gradients of litter quality, and microcosms with all leachates combined were used to test the effects of litter diversity. The results showed a positive effect of litter quality (p < 0.05) on mosquito oviposition rate, with lower C:P ratio litter species (high-quality litter) presenting higher oviposition rates than litter species with high C:P ratios (low-quality litter). However, contrary to our expectations, litter diversity had a negative effect (p = 0.002) on the magnitude of egg-laying by mosquitoes. Our results highlight the importance of litter quality and diversity for insect reproductive behavior. Our data shows that litter quality can serve as a crucial indicator of a suitable environment utilized by female mosquitoes for oviposition. This finding can enhance our ability to understand and develop effective methods for mitigating the reproduction of medically significant mosquitoes, whether by allowing us to predict, based on the composition of vegetation species, areas more prone to mosquito infestation, or by using high-quality litter in oviposition traps. Furthermore, maintaining vegetation diversity can help control mosquito reproduction.

Warming‐induced functional shifts in the decomposer community interact with plant community compositional shifts to impact litter decomposition

Abstract Climate warming is altering plant and soil microbial communities, with important implications for ecosystem processes like litter decomposition. As warming alters plant community composition, the quality of litter will change. Further, shifts in microbial community activity and/or composition will alter microbial function. However, it is not yet completely understood how these shifts will interact to drive decomposition. We explored how changes in plant and microbial communities interact to influence litter decomposition using a 15‐year‐old grassland warming experiment. Previous studies within this system have shown that warming shifted the microbial community in ways that accelerate litter decomposition while simultaneously shifting the plant community in ways that may slow decomposition. Specifically, warming increased abundance of Sorghastrum nutans, while decreasing abundance of the previously dominant Schizachyrium scoparium. Using a series of lab‐based microcosm experiments, we examined the rate at which eight common grasses and, separately, varying abundances of S. nutans and S. scoparium decomposed. Using litter and soil from the warming experiment, we then incubated soils from warmed or control plots with different abundances of S. nutans and S. scoparium in a reciprocal design. We found S. nutans to be the slowest‐decomposing grass in our system. Further, decomposition slowed as S. nutans increased and S. scoparium decreased. When examining the interaction of plant and microbial communities, decomposition was generally greater early in our experiment as the relative abundance of S. scoparium increased. However, soil microbial community origin and litter composition interacted significantly. Specifically, decomposition increased with greater relative abundance of S. scoparium on soils derived from control plots, while litter composition did not shape rates of decomposition on soils from warmed plots. The influence of litter species on decomposition waned in the later stages of the experiment when decomposition was driven by microbial community origin. These results suggest that warming‐induced changes in microbial community function may interact with changes in plant litter composition to mitigate the impacts of warming on rates of decomposition. This emphasizes the importance of considering concurrent warming‐induced changes in both plant and microbial communities on ecosystem processes like decomposition. Read the free Plain Language Summary for this article on the Journal blog.

Litter decomposition and nutrient release in different land use systems in the Brazilian semi-arid region

Climate and litter quality change the dynamics of soil organic matter (SOM) in agricultural systems, directly influencing the soil biological activity and, consequently, energy and nutrient cycling. This work evaluated the dynamics of organic carbon decomposition and nutrient release in litter in three land use management systems. The study was carried out under semi-arid conditions in Minas Gerais State, Brazil, using decomposition bags arranged in a randomized block design and four replications. The treatments consisted of three land use systems (native forest, corn, and cocoa) and seven evaluation times: 0, 30, 90, 150, 210, 270, and 330 days. Was evaluated dry matter production, litter decomposition in polyamide bags, and nutrient release (N, P, K, S, Ca, and Mg). Systems with native forest, cocoa and maize had similar average monthly litter production, a fact linked to the climate conditions. While in the semi-arid climate, the full-sun cocoa system showed a sudden oscillation in relation to the organic carbon content up to 330 days, the native forest and corn systems were more balanced, whitout significant changes. The higher litter C/N ratio in relation to the native and corn systems favors the maintenance of organic C levels in the soil. K release has a similar behavior in cultivated soils and occurs more quickly when compared to the native system. Regarding the other macronutrients, the soil in the cocoa production system showed the highest mineralization. Periods of accumulated precipitation accelerate litter decomposition and macronutrient release. The results of this study give more insight into the carbon dynamics and nutrient release from litter as a function of land use systems in a semi-arid region.

Dead bamboo culms promote litter mass, carbon and nitrogen loss, but do not modulate the effect of soil fauna on litter decomposition

Bamboos contribute significantly to carbon cycling in many (sub)tropical and temperate forests. In East Asia, unmanaged Moso bamboo stands accumulate large amounts of dead culms. However, very little is known about the indirect effects of dead culms on biogeochemical cycling through changes in soil conditions and decomposer communities. We evaluated the interactive effects of dead culms and soil fauna on litter decomposition in an unmanaged Moso bamboo stand. We placed leaf litter beneath the dead culms and on the forest floor (control) and used litterbags with different mesh sizes (1 mm and 42 μm) to control the access of soil mesofauna to the litter. We hypothesized that dead culms and soil fauna synergistically accelerate litter decomposition mainly because dead culms influence soil conditions and alter the litter fauna assemblage. We found that litter decomposing under the dead culms had greater litter mass, carbon and nitrogen loss, and microbial respiration rates than the control. The presence of soil mesofauna decreased litter mass, carbon and nitrogen loss but had no effect on the microbial respiration rate. Soil moisture was consistently higher under the dead culms, but their effect on soil temperature was dependent on the season. The litter decomposing below the dead culms had relatively higher mesofauna abundance and order richness. However, the contribution of the mesofauna to litter mass and nutrient loss was not modulated by the dead culms, suggesting that soil fauna had essentially the same effect on litter decomposition irrespective of the presence of dead culms. We showed that dead bamboo culms influence litter nutrient dynamics and promote habitat heterogeneity for soil microarthropods. Our results further highlight the ecological role played by dead culms and have implications for Moso bamboo management. The removal of dead culms from the forest floor could have substantial impact on the soil biota and ecosystem processes in managed stands.

Effect of thinning intensity on natural regeneration of Larix principis-rupprechtii.

We analyzed the impacts of thinning intensity on the natural regeneration of Larix principis-rupprechtii in Shanxi Pangquangou Nature Reserve, with an experiment of five thinning intensities (5%, 25%, 45%, 65% and 85%). We constructed a structural equation model of thinning intensity-understory habitat-natural regeneration by using correlation analysis. The results showed that the regeneration index of moderate thinning (45%) and intensive thinning (85%) stand land was significantly higher than that of other thinning intensities. The constructed structural equation model had good adaptability. The effects of thinning intensity on each factor were as follows: soil alkali-hydrolyzable (-0.564) > regeneration index (0.548) > soil bulk density (-0.462) > average height of seed tree (-0.348) > herb coverage (-0.343) > soil organic matter (0.173) > undecomposed litter layer thickness (-0.146) > total soil nitrogen (0.110). Thinning intensity had a positive impact on the regeneration index, which was mainly through adjusting height of the seed tree, accelerating litter decomposition, improving soil physical and chemical properties, and thus indirectly promoting the natural regeneration of L. principis-rupprechtii. Tending thinning could effectively improve the survival environment of regeneration seedlings. From the perspective of natural regeneration of L. principis-rupprechtii, moderate thinning (45%) and intensive thinning (85%) were more reasonable in the follow-up forest management.

Effects of thinning intensities on litterfall characteristics and decomposition in the natural secondary lowland forests of Southeastern Taiwan

ABSTRACT Research Highlights: This study presented novel evidence of the optimal level of forest thinning to maintain nutrient cycling and achieve management objectives. Background and Objectives: Litter dynamics play a vital role in balancing forest nutritional dynamics, which may be related to forest productivity. This study aimed to examine the influence of thinning intensity on litter quantity and quality in a secondary forest (a natural tropical secondary forest in southeastern Taiwan). Materials and Methods: Five different thinning treatments were implemented, and forest dynamics were measured. The litterbag method was used to assess the initial status of litter decomposition. Results: The rate of litter accumulation without thinning ranged from 5.14 to 5.63 t ha−1 yr−1. Thinning altered the litter decomposition rate. A 20% thinning intensity resulted in the fastest litter decomposition, with an annual litter loss of 22.4% compared with the control area. However, at >60% thinning intensity, the rate of litter decomposition slowed down, and the annual loss increased to 42.5%. Conclusions: Thinning changes the litter decomposition rate mainly by influencing soil humidity and temperature. A thinning intensity of 20% in secondary forest thins the forest, improves litter status, accelerates litter decomposition, and promotes nutrient cycling.

Mixed-Species Plantation of Pinus massoniana Lamb. and Quercus variabilis Bl. and High Soil Nutrient Increase Litter Decomposition Rate

Changes in land use and forest planting have led to substantial changes in soil fertility and leaf litter input. The effects of mixed planting on the leaf litter decomposition rate in contrasting soil nutrient conditions are poorly understood. To elucidate the effects of litter composition and soil fertility on litter decomposition, we conducted a field litterbag-decomposition experiment with single (Pinus massoniana Lamb. or Quercus variabilis Bl.) and mixed (P. massoniana and Q. variabilis) litter treatments on soils of three nutrient levels (high, medium, and low). During the 3-year decomposition, at each decomposition stage and soil nutrient level, the mass-loss rate (MLR) was higher in mixed-litter than in the two single-litter treatments, with the exception of Q. variabilis, which recorded a higher MLR at 724 d in medium and high soil substrates. Between the two single-litter treatments, the MLR of Q. variabilis litter was higher than that of the P. massoniana litter; the MLR of the component litter of P. massoniana and Q. variabilis was higher than that of the corresponding two single-litter treatments. The k values over the 3-year-experiment period increased with the soil nutrient level for all litter treatments, as did microbial biomass carbon and nitrogen content. These findings suggest that mixed planting and high level of soil nutrient can accelerate litter decomposition.

Nitrogen addition mediates monospecific and mixed litter decomposition in a boreal peatland

Litter decomposition is a key determinant of soil organic matter accumulation in boreal peatlands. Climate warming and atmospheric nitrogen (N) deposition have recently increased N availability in boreal peatlands. However, how increased N availability alters decomposition dynamics of plant litter is uncertain in these ecosystems, especially for litter mixtures. Here, we collected fresh litter of four common species (Betula fruticosa, Ledum palustre, Eriophorum vaginatum, and Sphagnum palustre) in a poor fen of northeast China, and established an N addition (6 g N m−2 year−1) experiment to assess the effect of increased N availability on monospecific and mixed litter decomposition in the hummocks and hollows after one and three years of decomposition. In both hummocks and hollows, N addition increased mass loss of four monospecific litter after one year of decomposition but only accelerated litter decomposition of E. vaginatum and S. palustre with low litter quality after three years of decomposition. Moreover, N addition effects on monospecific litter decomposition were negatively related to monospecific litter decomposition in the absence of N addition. Irrespective of decomposition position, additive effects were more frequent than synergistic effects during decomposition of litter mixtures. In addition, N addition generally changed synergistic effects to additive effects after one and three years of decomposition, and such changing trends were stronger in hummocks than in hollows. These observations suggest that litter quality mediates N addition effects on monospecific litter decomposition, and highlight that increased N availability will alter mixed litter decomposition by reducing synergistic effects in boreal peatlands.

Disruption of fungal hyphae suppressed litter-derived C retention in soil and N translocation to plants under drought-stressed temperate grassland

Litter decomposition often represents the largest carbon (C) and nitrogen (N) input into the soil and thereby supports soil nutrition cycling function. Common mycelial networks (CMNs) can promote soil C and N trades during the litter decomposition process. However, the degree to which this promotion depends on abiotic variables, such as drought, remains unresolved. Importantly, the influence of soil fungi mycelium on the turnover of litter-derived C and N could weaken under drought if disrupts fungal hyphae. Here, we used plant litter of stable isotope dual-labeling (13C and 15N), experimental drought (ambient, 30%, 50%, or 70% growing season precipitation reductions), and physical disruption to soil fungal hyphae (via soil core rotation) to investigate decomposition dynamics along the soil-plant-atmosphere continuum in a temperate grassland. On average, drought significantly slowed plant litter decomposition by up to 31.8%, but undisrupted fungal hyphae accelerated litter decomposition by up to 31.7% and promoted the release of C and N from plant litter. The intactness of fungal hyphae would have divergent effects on the allocation of litter-derived C and N during decomposition under drought conditions. Intact soil fungal hyphae contributed about 47% of litter-derived C transfer into soil microbial biomass after litter decomposition, but no significant effects in the soil, plant aboveground, or CO2 emissions, compared to hyphae disruption treatment. Undisrupted hyphae promoted approx. 82% of the turnover of litter-derived N from soil to plant and reduced content of litter-derived N in soil and N2O emission compared to hyphae disruption. We conclude that intact networks of soil fungal hyphae are essential to maintaining litter decomposition processes under drought conditions in temperate grassland ecosystems because the fungi promote releases of carbon and nitrogen from plant litter that facilitate carbon and nitrogen cycling.

Tree species composition alters the decomposition of mixed litter and the associated microbial community composition and function in subtropical plantations in China

Converting coniferous plantations to mixed plantations influences the microbial community composition and potential functions during litter decomposition. However, it is unclear how litter decomposition and associated microbial communities are interactively affected by litter mixing and environmental factors. Here, an in situ litter decomposition experiment was conducted to investigate the dynamics of microbial diversity in mixed litter (at a mass ratio of 1:1) from coniferous (Pinus massoniana) and broadleaf tree, including Bretschneidera sinensis, Manglietia chingii, Cercidiphyllum japonicum, Michelia maudiae, and Camellia oleifera. We found that the mass loss from mixed litter was higher than that of monospecific litter. The chemical characteristics of the broadleaf tree species included in the mixed litter significantly affected the microbial community composition and diversity, and those effects increased over time. Compared to the monospecific litter, the mixed litter had a higher relative abundance of saprotrophs and microbial functional groups related to carbon and nitrogen cycling. Moreover, litter chemistry (i.e., pH, lignin and cellulose content) and environmental factors (i.e., air temperature and soil moisture content) were the most crucial factors affecting the microbial decomposer community. Our results suggest that introducing broadleaf tree species with high litter quality to coniferous plantations changes the composition and function of microbial communities related to litter decomposition, which is conducive to accelerating litter decomposition in subtropical plantations.

Impacts of insect frass and cadavers on soil surface litter decomposition along a tropical forest temperature gradient.

Insect herbivores play important roles in shaping many ecosystem processes, but how climate change will alter the effects of insect herbivory are poorly understood. To address this knowledge gap, we quantified for the first time how insect frass and cadavers affected leaf litter decomposition rates and nutrient release along a highly constrained 4.3°C mean annual temperature (MAT) gradient in a Hawaiian montane tropical wet forest. We constructed litterbags of standardized locally sourced leaf litter, with some amended with insect frass + cadavers to produce treatments designed to simulate ambient (Control = no amendment), moderate (Amended‐Low = 2 × Control level), or severe (Amended‐High = 11 × Control level) insect outbreak events. Multiple sets of these litterbags were deployed across the MAT gradient, with individual litterbags collected periodically over one year to assess how rising MAT altered the effects of insect deposits on litter decomposition rates and nitrogen (N) release. Increased MAT and insect inputs additively increased litter decomposition rates and N immobilization rates, with effects being stronger for Amended‐High litterbags. However, the apparent temperature sensitivity (Q 10) of litter decomposition was not clearly affected by amendments. The effects of adding insect deposits in this study operated differently than the slower litter decomposition and greater N mobilization rates often observed in experiments which use chemical fertilizers (e.g., urea, ammonium nitrate). Further research is required to understand mechanistic differences between amendment types. Potential increases in outbreak‐related herbivore deposits coupled with climate warming will accelerate litter decomposition and nutrient cycling rates with short‐term consequences for nutrient cycling and carbon storage in tropical montane wet forests.

Enhanced release, export, and transport of diffuse nutrients from litter in forested watersheds with climate warming.

Variations in litter decomposition and nutrient migration are constraints to accurately estimate watershed diffuse forest pollution under the combined effects of topographic heterogeneity and climate change. In this study, remote sensing data, decomposition and leaching experiments, and the Soil and Water Assessment Tool (SWAT) were used to quantify the release, export, and transport characteristics of diffuse nutrients from forest litter under two climate scenarios (the current climate condition [S1] and the future warming and drying climate condition [S2]), and the impacts on aquatic environment were identified. The annual litter decomposition was 27.80 × 106 t in S2, which was 1.39 times that of S1. Additionally, the annual litter nutrient release in S2 (C, N, and P was 8.65 × 106, 3.31 × 105, and 1.57 × 104 t, respectively) also increased by 31.16%-45.62% compared with that of S1. The spatial patterns of nutrient export showed that the annual exports of C, N, and P in S1 were 109.77, 46.85, and 0.43 kg/ha, respectively. The annual nutrient export in S2 increased by 1.44 times, and S2 also had higher values of nutrient transport. In addition, variation trends of temperature and precipitation increased significantly with increasing altitude, which promoted differences in nutrient transport between S1 and S2 in the high-altitude areas. The response analysis of the diffuse nutrient in surface water also indicated that forest nutrient discharge load were critical factors affecting the aquatic environmental quality. This study indicated that climate warming accelerated litter decomposition and made litter a potential source of diffuse forest pollution, and watershed discharge load varied intensively with the terrestrial conditions. The combination of experiments and modeling can improve the accuracy of diffuse forest pollution simulation and provide valuable information for formulating watershed climate change adaptation strategies.