Litter Inputs Research Articles

Fertilization effects on soil organic matter chemistry

Despite the close interactions between carbon (C) and nutrients like nitrogen (N), phosphorus (P), and potassium (K), the consequences of N fertilization alone or in combination with P and K on soil organic matter (SOM) chemical composition remain unclear. Using solid-state 13C nuclear magnetic resonance spectroscopy data from 45 field studies, we meta-analyzed the effects of N alone and NPK fertilization on SOM content and chemical composition. Generally, mineral fertilization affects the SOM content and composition via three indirect processes: i) increasing litter input and rhizodeposition, ii) accelerating microbial decomposition of SOM, and iii) modifying the preservation of SOM by soil minerals. NPK fertilization (+12 %) increased organic C content more than N fertilization alone (+8.6 %). Alkyl and O-alkyl C increased at low-N rates (<50 kg N ha−1 yr−1) or after short-term (0–5 yrs) N fertilization alone, likely because improved N availability promoted bacterial residues rich in long-chain aliphatic C formation and carbohydrate-rich matter inputs. High-rate (>200 kg N ha−1 yr−1) or long-term (>25 yrs) NPK fertilization increased alkyl C but decreased aromatic C, likely due to reduced nutrient limitations and acidification. These factors promote aliphatic C-rich microbial biomass, accelerate the decomposition of stable compounds, and decrease the mineral protection of aromatic acids. The SOM chemical composition (excluding aromatic C) response to NPK fertilization decreased with increasing initial level. In contrast, the response of SOM raised with increasing initial content under N fertilization alone. The increase in organic C content was strongly linked to changes in SOM chemistry under NPK fertilization but not under N fertilization alone. In conclusion, NPK fertilization modified SOM chemistry and increased organic C accumulation more effectively than N fertilization alone, which was mediated by increasing plant growth, raising microbial biomass and activity, altering mineral protection, and initial soil C levels. Our findings provide critical insights for optimizing fertilization strategies to improve soil C sequestration capacity and fertility.

Key Soil Abiotic Factors Driving Soil Sickness in Lycium barbarum L. Under Long-Term Monocropping

Sustainable cultivation of Lycium barbarum L. (L. barbarum) in northwest China faces challenges due to soil sickness. While previous studies have explored variations in L. barbarum’s root-associated microbiota, the impact of soil properties on its growth performance and plant–soil feedback remains unclear. This study investigated changes in soil properties across topsoil (0–20 cm) and subsoil (20–40 cm) in primary L. barbarum cultivation regions of northwest China, evaluating seedling growth and plant–soil feedback through pot experiments. Results revealed significantly higher fresh shoot weights in seedlings cultivated in topsoil compared to subsoil, with plant–soil feedback showing an inverse trend. Redundancy analysis indicated positive correlations between both fresh weight and plant–soil feedback with electrical conductivity and dissolved nitrogen content, while negative correlations were observed with soil pH at both depths. Notably, dissolved organic carbon content negatively correlated with fresh weight and plant–soil feedback in topsoil, suggesting a potential relationship between continuous single-species plant litter input and soil sickness under monocropping conditions. These findings indicate that long-term input of a single plant litter type, rather than chemical fertilization, may primarily contribute to L. barbarum soil sickness in northwest China, providing valuable insights for developing sustainable cultivation practices for growing L. barbarum.

Independent effects of tree diversity on aboveground and soil carbon pools after six years of experimental afforestation.

Planting diverse forests has been proposed as a means to increase long-term carbon (C) sequestration while providing many co-benefits. Positive tree diversity-productivity relationships are well established, suggesting more diverse forests will lead to greater aboveground C sequestration. However, the effects of tree diversity on belowground C storage have the potential to either complement or offset aboveground gains, especially during early stages of afforestation when potential exists for large losses in soil C due to soil decomposition. Thus, experimental tests of the effects of planted tree biodiversity on changes in whole-ecosystem C balance are needed. Here, we present changes in above- and belowground C pools 6 years after the initiation of the Forests and Biodiversity experiment (FAB1), consisting of high-density plots of one, two, five, or 12 tree species planted in a common garden. The trees included a diverse range of native species, including both needle-leaf conifer and broadleaf angiosperm species, and both ectomycorrhizal and arbuscular mycorrhizal species. We quantified the effects of species richness, phylogenetic diversity, and functional diversity on aboveground woody C, as well as on mineral soil C accumulation, fine root C, and soil aggregation. Surprisingly, changes in aboveground woody C pools were uncorrelated to changes in mineral soil C pools, suggesting that variation in soil C accumulation was not driven by the quantity of plant litter inputs. Aboveground woody C accumulation was strongly driven by species and functional identity; however, plots with higher species richness and functional diversity accumulated more C in aboveground wood than expected based on monocultures. We also found weak but significant effects of tree species richness, identity, and mycorrhizal type on soil C accumulation. To assess the role of the microbial community in mediating these effects, we further compared changes in soil C pools to phospholipid fatty acid (PLFA) profiles. Soil C pools and accumulation were more strongly correlated with specific microbial clades than with total microbial biomass or plant diversity. Our results highlight rapidly emerging and microbially mediated effects of tree biodiversity on soil C storage in the early years of afforestation that are independent of gains in aboveground woody biomass.

Contrasting Life-Form Influences Guam Ficus Foliar Nutrient Dynamics

Tropical trees that remain evergreen and exhibit leaf litterfall that is gradual over time coexist with trees that are seasonally deciduous and exhibit pulsed litterfall. The manner in which these trees acquire, store, and contribute nutrients to the biogeochemical cycle may differ. Green and senesced leaves from deciduous Ficus prolixa trees were compared with those from Ficus tinctoria on the island of Guam. The results enabled stoichiometry and resorption calculations. F. prolixa’s young green leaf nitrogen (N) and potassium (K) concentrations were double, and the phosphorus (P) concentration was triple, those of F. tinctoria. Concentrations converged as the leaves aged such that no differences in concentration occurred for senesced leaves, indicating that nutrient resorption proficiency did not differ between the two species. In contrast, the resorption efficiency was greater for F. prolixa than F. tinctoria for all three nutrients. The N:P values of 6–11 and K:P values of 5–7 were greater for young F. tinctoria leaves than young F. prolixa leaves. The N:K values were 1.1–1.6 and did not differ between the two species. No differences in pairwise stoichiometry occurred for senesced leaves for any of the nutrients. These Guam results conformed to global trends indicating that seasonally deciduous plants are more acquisitive and exhibit greater nutrient resorption efficiency. The differences in how these two native trees influence the community food web and nutrient cycling lies mostly in the volume and synchronicity of pulsed F. prolixa litter inputs, and not in differences in litter quality. These novel findings inform strategic foresight about sustaining ecosystem health in Guam’s heavily threatened forests.

Exotic mangrove Laguncularia racemosa litter input accelerates nutrient cycling in mangrove ecosystems.

Exotic plant litter presents different chemical and physical properties relative to native plant litter and alters ecosystem processes and functions that may facilitate exotic plant dispersal. However, these effects are largely unknown, especially within wetland ecosystems. This study examines whether introducing litter from theexotic mangrove Laguncularia racemosa could result in (1) accelerated community litter decomposition rates and increased nutrient cycling rates and (2)microbial community structure changes in the invaded areas. A single decomposition experiment using litterbags was conducted to examine the short-term effects of L. racemosa litter in the native mangrove forest ecosystem. The soil nutrients and microbial communities of Rhizophora stylosa, L. racemosa, and mixed forests were also compared to explore the long-term cumulative effects of L. racemosa litter in native ecosystems. The results indicated that L. racemosa has lower-quality leaf litter than R. stylosa and a significantly faster decomposition rate. This may result from changes in the soil microbial community structure caused by L. racemosa leaf litter input, which favors the decomposition of its own litter. Both the short-term and cumulative effect experiments demonstrated that L. racemosa leaf litter significantly increased the relative abundance of microbes related to litter decomposition, such as Proteobacteria and Bdellovibrionota, and enhanced the alpha diversity of soil fungi, thus creating a microbial environment conducive to L. racemosa leaf litter decomposition. Moreover, the accumulation of soil nutrients was lower under L. racemosa than under R. stylosa over several years. This may be related to the more rapid growth of L. racemosa, which causes soil nutrient absorption and storage within the plant tissues, thereby reducing the soil nutrient content. Inputting exotic mangrove L. racemosa leaf litter reduced the soil blue carbon content, potentially adversely affecting global climate change. L. racemosa may employ a unique strategy to lower soil nutrient levels in native mangroves based on its low-quality leaf litter, thereby weakening the competitive ability of native plants that are intolerant to low-nutrient conditions and enhancing its own competitive advantage to further spread into these areas. In summary, the input of exotic L. racemosa leaf litter accelerates nutrient cycling in local mangroves.

Species‐specific effects of leaf litter leachate on the aquatic microbial community and the ratio of heterotrophic to autotrophic biomass

Abstract Dissolved organic carbon (DOC) released from submerged leaf litter is an important allochthonous carbon source for heterotrophic bacteria that enhances the detrital food chain in freshwater ecosystems. In contrast, nitrogen (N), phosphorus (P) and micronutrients released during the leaching process support primary production and enhance the grazing food chain in these ecosystems. This study investigated how DOC and dissolved N and P from the leaf litter of two temperate broadleaf and two coniferous tree species affect heterotrophic and autotrophic biomass by incubating the freshwater microbial community in the culture media prepared from the leaf litter leachate. The results showed that heterotrophic biomass, including bacteria, heterotrophic‐flagellated protists and fungal zoospores, was the highest in the leaf litter leachate, which contained the highest DOC concentration relative to dissolved N and P (Japanese hemlock). In contrast, autotrophic biomass, including small algae, autotrophic flagellated protists and cyanobacteria, was associated with concentrations of dissolved N and P in the leaf litter leachates. Amendment of basal nutrients other than N and P, including micronutrients, trace elements and vitamins, increased autotrophic biomass in two leaf litter leachates (oak, Siebold's beech), suggesting that some elements other than N and P were deficient relative to the requirements of autotrophic organisms. These results indicated that the elemental composition of leaf litter leachates influences microbial community structure and heterotrophic versus autotrophic biomass in freshwater ecosystems. More importantly, the present results suggest that changes in forest vegetation surrounding freshwater ecosystems alter detritus‐based heterotrophic production relative to autotrophic production through the changes in the elemental composition (i.e. stoichiometry) of leaf litter inputs.

Research advance in the effects of litter input on forest soil organic carbon transformation and stability.

The turnover and stabilization of soil organic carbon are tightly associated with the properties of litter input. Due to the complexity of litter decomposition and the high heterogeneity of forest soils, there are considerable uncertainties about how soil minerals, microorganisms, and environmental factors jointly regulate the transformation and stability of litter-derived soil organic carbon. Here, we present an overview of the "microbial efficiency-matrix stabilization" framework centered on microbial metabolism and organic carbon transformation, as well as the new "microbial carbon pump" and "mineral carbon pump" theories in forest soil organic carbon transformation and stabilization. We specifically highlighted a differential mechanism of "organo-organic interfaces" from the "organo-mineral interfaces" in the effects on soil organic carbon accumulation. We further expounded the transformation processes and stability of soil organic carbon based on the "carbon material cycling" and "energy fluxes", aiming to provide theoretical support for the research on carbon sequestration in forest soils.

Miscanthus litter additions induce a successional change in the soil micro-food web with apparent decreases in soil nitrogen

The rapid loss of soil carbon (C) from cultivated peatland soils is leading to the use of high lignin, C-rich litter amendments as a potential solution to slow C losses. These chemically recalcitrant litter inputs are expected to cause microbial nitrogen (N) immobilization as a result of changes in the soil micro-food web, but whether bioavailable N is altered by litter as it is decomposed by the micro-food web remains unclear. We monitored changes in the soil nematode, fungal, and bacterial communities over time and across space (the rhizosphere and bulk soil) after field-applying different types of ligneous litter from miscanthus, ash, willow, or larch to a cultivated peatland soil. We found that miscanthus grass (C:N = 118) induced succession from fast-growing nematodes (cp-1) to slower-growing, cp-3 and cp-4 nematodes and this corresponded to reduced N availability. This lower soil N was likely due to relatively higher microbial biomass we observed with miscanthus, combined with a decrease in fast-growing bacterivores, limiting N mineralization from nematode grazing. We did not observe strong effects on the soil micro-food web or microbial biomass N for the other woody litters that had much higher C:N. This indicates that the changes in nematode community composition following ligneous litter inputs and subsequent impacts on soil N depend on litter type but are independent of litter C:N. Miscanthus amendments also corresponded to the lowest lettuce yield of all the amendments and thus caution is raised when using miscanthus straw as a widely-applied litter. Our results provide a useful reference to predict the effect of litter amendments on cultivated peatland soils through soil micro-food web dynamics, and bioavailable N for the crop.

Tree species-mediated soil properties shape soil fauna community structure more strongly in the soil layer: Evidence from a common garden experiment

Soil fauna plays a crucial role in the soil biogeochemical cycles of forest ecosystems, with tree species composition regulating their diversity and functionality through alterations in habitat conditions and nutrient availability. However, identifying the impacts of tree species on soil faunal communities remains challenging due to the difficulty in distinguishing the effects of tree species-induced habitat changes from those of historical environmental conditions. Here, we conducted a field study in a common garden established in 2015, with consistent climate, soil, and land-use conditions to clarify the response of the soil faunal community to changes in tree species. After 5 years of plantation growth, we evaluated the differences in tree species identities and soil faunal community structures between the litter and soil layers in four closed-canopy broadleaf forests (Cinnamomum septentrionale, Cinnamomum camphora, Cinnamomum longepaniculatum and Toona sinensis). We found that the soil faunal communities differed significantly among the four broad-leaved tree species, with 18.7 % being dominated by Collembola and 67.2 % by Acari, with a relatively high proportion of microbivores (65.5 %). Compared with that of the other stands, the C. longepaniculatum stand had the most notable differences in taxa composition, while the T. sinensis stand exhibited the greatest soil biological quality, with a QBS value 1.25 times greater than that of other stands. The greatest total soil faunal abundance was observed in C. camphora, and this high abundance was due to a greater proportion of microbivores (75.4 %), whereas the detritivores, herbivores, and predators exhibited greater abundance in T. sinensis than in the other stands due to the high-quality litter input (low C/P and C/N ratios) and low tree biomass. The distribution of soil fauna across the habitat layers was significantly influenced by tree species changes, with the most pronounced differences occurring in the soil layer rather than in the litter layer. Finally, soil properties, rather than litter and plant conditions, were the primary factors explaining interspecific variations in total abundance and total diversity of the soil fauna and the QBS index, accounting for 61.6 %, 71.7 %, and 34.4 % of the variation, respectively. The results from the common garden experiment suggest that the change in the soil faunal community due to tree species identity was greater in the soil layer than in the litter layer, with the crucial determinant being tree-species-mediated soil properties. These insights enhance our understanding of the effect of tree species on soil faunal communities, which is essential for biodiversity conservation in artificial forests and for guiding tree species selection.

Effect of fire on microbial necromass carbon content is regulated by soil depth, time since fire, and plant litter input in subtropical forests

Effect of fire on microbial necromass carbon content is regulated by soil depth, time since fire, and plant litter input in subtropical forests

High-quality litter exerts a greater effect on soil carbon gain in unrestored than restored pine plantations

Vegetation restoration of degraded land affects litter quality by changing the composition of tree species, providing direct effects on regulating the dynamic of soil organic C (SOC) through the priming effect (PE). However, it is unclear how the combined effects caused by vegetation restoration and input of different quality litters on PE-related C loss and gain. Here, we collected soils from an unrestored site and a site restored for 20 years, adding 13C-labeled low-quality (with high C/nitrogen [N] and lignin/N) and high-quality (with low C/N and lignin/N) litters to the soil, respectively. Our results revealed that adding high- and low-quality litter in two sites produced positive PEs after 150-day laboratory-based incubation. The PE induced by high-quality litter was lower than that of low-quality in two sites, which can be interpreted as low-quality litter has higher C/N that aggravates the nutrient imbalance of microorganisms and enhances their demand for N, prompting microorganisms to accelerate the mineralization of SOC through the “N mining”. High-quality litter inputs can boost microbial C use efficiency and alleviate soil C loss due to PE in unrestored and restored pine forests. Moreover, high-quality litter input has a greater positive effect on SOC gain in unrestored lands than in restored lands, suggesting that litter with higher nutrient availability or fertilization is especially needed for the restoration of degraded soil fertility and C formation. Taken together, this study highlights the importance of tree species producing high-quality litter in mediating SOC decomposition and formation during degraded lands restoration, which is beneficial for the restoration of degraded lands and the enhancement of soil C sequestration.

Litter input promoted dissolved organic carbon migration in karst soil

Litter input is crucial for enhancing carbon sequestration in karst ecosystems. While previous studies have linked litter input to carbon storage in karst soils, the unique conditions of southwest China’s karst regions, characterized by high precipitation and rapid groundwater dynamics, pose challenges to understanding dissolved organic carbon (DOC) migration under litter cover. This study investigated how different litter types from karst-adapted vegetation affect DOC migration and loss in karst soils, addressing the gaps in carbon sequestration evaluations during vegetation restoration. Artificial soil columns were used to monitor the natural rainfall over one hydrological year. The results indicated that litter cover increased the soil carbon dioxide (CO2) concentration and enhanced DOC leaching and migration, with the highest DOC loss observed in the tree litter treatment (2614.50 mg) and the lowest in the shrub litter treatment (1844.13 mg). These differences were attributed to the synergistic interaction between rainfall and litter characteristics, which accounted for 29.94 % of the variation in soil DOC leaching after litter input. Regression analyses indicated that DOC leaching under litter cover was mainly affected by the soil CO2 concentration, temperature, humidity, rainfall, and litter decomposition duration. In summary, litter cover significantly intensified DOC migration and loss in karst soils. This study provides valuable insights into vegetation restoration and reconstruction, particularly in karst regions.

Enhanced crop yields as a potential mitigator of soil organic carbon losses under elevated temperature in erosional and depositional landscape

The dynamics of agricultural soil organic carbon storage have been considerably influenced by the evolution of crop species, offering promising opportunities for restoring soil organic carbon under elevated temperatures through yield improvements. However, the intricate interplay between climate change and surface erosion processes poses challenges in understanding agricultural soil carbon dynamics in hilly landscapes. This study aimed to address these challenges by assessing the effects of climate change on soil organic carbon dynamics under the Shared Socioeconomic Pathways 245 and 585. We utilized projections from 12 distinct global climate models, covering the period from 2015 to 2100. Additionally, we investigated the potential for improving soybean yields by 100 %, 200 %, and 300 % linearly by 2100 to offset the anticipated soil organic carbon losses. Using a coupled landscape and biogeochemical model, our analysis focused on a soybean field in Nenjiang County, China. Our findings revealed a distinct soil organic carbon profile in deposition areas, characterized by relatively low levels of soil organic carbon in surface layers, attributed to carbon influx from adjacent erosion areas with typically low carbon content. We modeled decreases in soil CO2 fluxes with escalating climate change, corresponding to expected decreases in soil organic carbon levels, despite concurrent rises in soil microbial activity linked to increasing temperatures. Erosion areas emerged as particularly vulnerable zones under elevated temperatures due to their higher proportion of soil CO2 fluxes relative to soil organic carbon levels compared to deposition areas. As a soil organic carbon restoration strategy, improvements in soybean yields showed promise in mitigating soil organic carbon losses through enhanced litter inputs and the cooling effects induced by shading the soil. This study underscored the potential for achieving the dual benefits of food security and soil organic carbon restoration in the coming decades through a unified approach to enhancing soybean yields.

Variations in source-specific soil organic matter components across 32 forest sites in China

Forest soils store substantial amounts of carbon in various soil organic matter (SOM) components due to high plant litter inputs and active microbial turnover. However, the variations in plant- and microbial-derived SOM components in surface and subsurface forest soils across a wide geographic scale remain poorly understood. This study investigated the SOM components from aboveground and belowground plant inputs and fungal and bacterial necromass in surface (soil0–5 cm) and subsurface (soil5–10 cm) soils across 32 forest sites in China and analyzed their relationships with climate and edaphic factors. Compared to soil0–5 cm, soil5–10 cm exhibited lower soil organic carbon content and cutin biomarker concentration but higher concentrations of fungal necromass carbon and lignin phenols. Higher mean annual precipitation led to higher concentrations of cutin and suberin biomarkers in soil0–5 cm and soil5–10 cm, respectively. Higher soil organic carbon content was associated with lower plant-derived lignin biomarkers, higher lignin oxidation degrees, and increased microbial necromass-derived amino sugars across sites, highlighting the pivotal role of microbial necromass in SOM stabilization. Additionally, both fungal and bacterial necromass decreased with increasing mineral weathering across sites. These insights improve the understanding of environmental drivers of source-specific carbon storage in forest soils.Graphical

The influence of shade tree species and coffee varieties on selected soil physicochemical properties in coffee-based farming system of southwestern Ethiopia

Different shade tree species are used in various coffee production systems across the world. Outside the benefits of biodiversity protection, temperature protection, and carbon sequestration shade trees can influence soil nutrient states through litter inputs and nitrogen fixation. However, little information is available in coffee plantations whether shade tree species and type of coffee variety planted under shade tree have an influence on soil physical properties and nutrient status in coffee-based farming systems of southwestern Ethiopia. Hence, the study was carried out to investigate the effect of shade tree species and coffee varieties in coffee plantation on the physicochemical properties of the soil. The study was conducted in Chora Botor district (Chalalaki coffee plantation), located in Jimma Zone, Oromia regional states of Ethiopia. The study was superimposed on coffee farm that has been established using four released coffee varieties (7440,744, F59 and 75227) under three recommended coffee shade trees (Albizia gummifera, Millettia feruginea and Acacia abyssinica). Soil physical properties and nutrient status were investigated in response to shade tree species, coffee varieties and their combination. The results indicated that the physical and chemical properties of the soil vary across the shade trees and coffee variety grown. The effect of shade tree species on soil depends on the type of coffee varieties grown under the shade tree species, Albizia gummifera and Acacia abyssinica trees enhanced more soil nutrient content and water-holding capacity of the soil than Millttia ferrugnia. Total nitrogen, organic matter, available phosphorous, exchangeable potassium, Cations Exchange Capacity, and bulk density were higher underneath Albizia gummifera than other coffee shade tree species. On the other hand, moisture content, available P, exchangeable K and CEC were higher beneath Acacia abyssinica than other coffee shade tree species. Soil pH was negatively correlated with Millettia ferruginia. Use of Acacia abysinica and Albizia gummifera shade tree species with compatible coffee varieties could be a viable option to augment soil fertility management practices in the coffee production systems of the southwest Ethiopia.

Drought effects on litter fraction and recovery in a subtropical forest

Litter input is a critical link between the circulation and flows of energy and matter in forest ecosystems. Drought events impact litter inputs, affecting forest ecosystems’ nutrient and energy cycles. To investigate the response of litter production to extreme drought, explore their recovery mechanism, and the difference between whole year, concurrent drought, non-drought period, rainy season, and dry season. We studied an extreme drought event in a subtropical evergreen broadleaved forest in the Ailao Mountain in 2009–2010. We used 10 years (2005–2014) of monthly litter production and climate data, including monthly average precipitation (MAP), soil water content (SWC), and monthly average temperature (MAT). The observation period was separated into pre-drought (2005–2008), during-drought (2009–2010), and post-drought (2011–2014) periods. We found that annual total litter production decreased by 12 % during the drought (p < 0. 05), similar to that in the drought period. Leaf litter production increased by 1 % during drought time, and other fraction decreased obviously. The contribution of water environmental factors to litter production was more evident after drought events. MAT, MAP, and SWC jointly affect litter input under extreme drought conditions, and the dominant factor is related to litter fraction and drought periods. Water environmental factors (MAP & SWC) contributed to litter input after drought events, while MAT mainly affected litter input during the non-drought and rainy seasons. Due to the growth and nutritional strategies of each fraction, the recovery time is branch < leaf < flower & fruit < moss < bark. The results further reveal litter production response to drought events and the importance of water factors in recovery.

Mechanisms of litter input changes on soil organic carbon dynamics: a microbial carbon use efficiency-based perspective

Plant litter is an important source of soil organic carbon (SOC) in terrestrial ecosystems, and the pattern of litter inputs is also influenced by global change and human activities. However, the current understanding of the impact of changes in litter inputs on SOC dynamics remains contentious, and the mechanisms by which changes in litter inputs affect SOC have rarely been investigated from the perspective of microbial carbon use efficiency (CUE). We conducted a 1-year experiment with litter treatments (no aboveground litter (NL), natural aboveground litter (CK), and double aboveground litter (DL)) in Robinia pseudoacacia plantation forest on the Loess Plateau. The objective was to assess how changes in litter input affect SOC accumulation in forest soils from the perspective of microbial CUE. Results showed that NL increased soil microbial C limitation by 77.11 % (0–10 cm) compared to CK, while it had a negligible effect on nitrogen and phosphorus limitation. In contrast, DL had no significant effect on soil microbial nutrient limitation. Furthermore, NL was found to significantly increase microbial CUE and decrease microbial metabolic quotient (QCO2), while the opposite was observed with DL. It is noteworthy that NL significantly contributed to an increase in SOC of 30.72 %, while DL had no significant effect on SOC. Correlation analysis showed that CUE was directly proportional to SOC and inversely proportional to QCO2. The partial least squares pathway model indicated that NL indirectly regulated the accumulation of SOC, mainly through two pathways: promoting microbial CUE increase and reducing QCO2. Overall, this study elucidates the mechanism and novel insights regarding SOC accumulation under changes in litter input from the perspective of microbial CUE. These findings are critical for further comprehension of soil carbon dynamics and the terrestrial C-cycle.

Enhanced plant litter impacts nematode communities and carbon use efficiency in a mixed forest

Abstract Rising temperatures and higher atmospheric CO2 levels can potentially increase plant photosynthesis and boost forest productivity, thereby spurring litter inputs to soils on a global scale. Understanding the feedback loops between increased litter inputs and soil biota activity will allow for better prediction of organic matter and carbon (C) cycling in terrestrial ecosystems. Nematodes represent the full spectrum of trophic groups within the soil biota. Accordingly, we studied the link between nematode metabolic activities and plant litter input. For this, different litter input levels were manipulated in a temperate forest, including control zones without litter, natural litter input zones and zones with double, triple and quadruple amounts of natural litter input. Soil top layers (0–10 cm) were then collected to study the responses of nematode communities. Increased litter input positively influenced the abundance and diversity of nematodes, except for plant‐parasitic species. Higher litter input levels led to an enhancement in the ratio of bacterivores to the total of bacterivores and fungivores. More litter increased the K/r strategist ratio among bacterivores and the corresponding nematode metabolic footprints. More litter also stimulated nematode production and respiration components and improved the carbon use efficiency of bacterivores. Moreover, structural equation modelling revealed the crucial role of bacterivores in influencing soil organic C under increased litter input. In conclusion, our study shows that increased plant above‐ground litter input modifies the taxonomic and functional communities of soil nematodes, ultimately regulating carbon cycling in forest soils. Read the free Plain Language Summary for this article on the Journal blog.

Salix species and varieties affect the molecular composition and diversity of soil organic matter

Abstract Background and aims Most studies of the relationships between the composition of soil organic matter and plant cover have been carried out at the plant genera level. However, they have largely overlooked the potential effects that plant varieties, belonging to the same genus, can have on soil organic matter. Methods We investigated whether plant varieties belonging to different Salix species (S. dasyclados and S. viminalis) impacted the composition of organic matter using mid-infrared spectroscopy and pyrolysis GC/MS. Top-soils were taken from an 18 year-old long-term field trial where six Salix varieties were grown as short-rotation coppice under two fertilisation regimes. Results Significant differences in the molecular composition and diversity of the soil organic matter were observed in the fertilised plots. The effects were mostly visible at the species level, i.e. the organic matter in soil under S. dasyclados varieties had higher molecular diversity and lignin content than under S. viminalis, potentially due to differences in the amount and composition of their litter inputs. Smaller differences among varieties from the same species were also observed. No significant effects of Salix varieties were observed in the unfertilised plots. The relatively high degree of spatial variability of several soil properties found in these plots may have masked plant variety and/or species effects. Conclusion This study provides evidence that the identity of Salix species or varieties can affect the molecular composition and diversity of soil organic matter. The corresponding traits should be considered in breeding programmes to enhance soil organic C accumulation and persistence.

Leaf litter breakdown phenology in headwater stream networks is modulated by groundwater thermal regimes and litter type

AbstractLeaf litter dominates particulate organic carbon inputs to forest streams. Using data‐informed simulations, we explored how litter type (slow‐ vs. fast‐decomposing species), pulsed autumn litter inputs, groundwater‐mediated temperature regimes, and climate warming affect litter breakdown in a 3rd‐order stream network. We found that the time‐dependent interactions of these variables govern network‐scale litter breakdown phenology, with greater thermal sensitivity of slow‐decomposing litter for both current and future scenarios. Groundwater thermal inputs modified litter breakdown phenology by reducing spring and summer and elevating winter litter breakdown fluxes. Under future warming scenarios, the source depth of contributing groundwater influenced summer detrital resources; shallow groundwater‐fed streams had reduced summer resources compared to deep groundwater‐fed streams. Our results demonstrate that predicting in‐stream carbon cycling requires explicit consideration of the phenology of resource inputs and the seasonal timing of environmental factors, notably stream thermal regimes.