Litter Diversity Research Articles

Effects of plant litter diversity on soil enzyme activity and microbial community composition in a Mongolian pine plantation

Effects of plant litter diversity on soil enzyme activity and microbial community composition in a Mongolian pine plantation

Assessment of transboundary macro-litter on the remote island of Andaman and Nicobar: Unveiling the governing factors and risk assessment

The increasing occurrence of mismanaged plastic litter along India's coastline and the ominous challenges it poses to biodiversity and ecosystem health is a growing environmental concern. To address this issue, we comprehensively investigated the abundance, composition, and probable sources of marine litter on North Cinque Island, a remote uninhabited island in the Andaman and Nicobar archipelago, Bay of Bengal. This island is a designated wildlife sanctuary and serves as an important nesting site for Green, Hawksbill and Leatherback turtles. A total of 6227 litter items were enumerated, with an average concentration of 0.12 items/m2, representing 20 diverse litter types, with plastic dominating the litter composition (86 %). The cleanliness and environmental hazards of the coast due to the litter were assessed using different indices such as the Clean Coast Index (CCI), Plastic Accumulation Index (PAI), Hazardous Item Index (HII), and Clean Environment Index (CEI). CCI indicates the moderately clean-to-clean status of the surveyed sites. PAI points to low to moderate accumulation of plastic litter. HII of all five coasts fell in category II, suggesting a moderate abundance of hazardous items that can inflict injuries to the foraging turtle and their hatchlings. The CEI articulates the moderately clean to very clean status of the sites. Litter brand audit suggests a considerable amount of stranded litter on the coasts was transboundary and originated from six Indian Ocean Rim Countries (IORC), namely Thailand, Myanmar, Malaysia, Indonesia, Sri Lanka, and UAE. Joint solid waste management by the IORC is the need of the hour to avert litter accumulation on the pristine, remote islands.

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

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

Response of Soil Microbial Community Structure and Diversity to Mixed Proportions and Mixed Tree Species in Bamboo–Broad-Leaved Mixed Forests

Bamboo and broad-leaved mixed forests have been widely recognized for their advantages in maintaining ecological balance, improving soil fertility, and enhancing biodiversity. To understand the effects of mixed broad-leaved tree species and mixing ratios on soil microbial communities in bamboo and broad-leaved mixed forests, we quantified the structure and diversity responses of soil microbial communities to tree species and mixing ratios using high-throughput sequencing of the 16 S rRNA gene. Three bamboo and broad-leaved tree mixed forests were studied, including bamboo–Castanopsis chinensis Hance mixed forest (CCB), bamboo–Alniphyllum fortune (Hemsl.) Makino mixed forest (AFB), and bamboo–Choerospondias axillaris (Roxb.) B. L. Burtt & A. W. Hill mixed forest (CAB). We assessed the impact of tree species and mixing ratios on soil microbial communities by measuring soil properties and the diversity and composition of soil microbes. The results indicate that soil properties and the diversity and composition of microbial communities are highly dependent on broad-leaved tree species in mixed forests. The mixing ratios had a more pronounced effect on microbial diversity than on richness. In CAB, diversity peaked at mixing ratios of 10%–20% and 20%–40%. The presence of broad-leaved trees significantly altered the relationships among soil bacteria, with CAB showing the highest stability, likely due to the increased diversity and quantity of litter from Choerospondias axillaris. Our results show that the choice of broad-leaved tree species and their mixing ratios significantly influence soil microbial diversity and composition in bamboo–broad-leaf mixed forests. An optimal mixing ratio in CAB can maximize bacterial diversity and stability, providing insights for forest management and promoting ecosystem health and sustainability.

Utilizing the diversity of arbuscular mycorrhizal fungi and sweet potato leaf litter for the growth and production of andrographolide compounds in Andrographis paniculata

Utilizing the diversity of arbuscular mycorrhizal fungi and sweet potato leaf litter for the growth and production of andrographolide compounds in Andrographis paniculata

Shade tree trait diversity and functions in agroforestry systems: A review of which traits matter

Abstract Shade trees in agroforestry systems confer ecosystem services, such as enhanced soil fertility from diverse litter inputs, microclimate regulation via shade, and disease mitigation through trophic and abiotic interactions. With this thriving role of agroforestry in sustainable agriculture, particularly for tree crops, systematic and reliable methods to select shade trees for specific agroecosystem outcomes are crucial. Plant functional traits offer a framework to describe, select and manage shade trees. Over the last decade, shade tree leaf functional traits and whole plant traits have been assessed in agroforestry systems. Yet, we lack amalgamated information on (i) what we know about shade tree trait relationships with functions to achieve desired agroecosystem outcomes, (ii) how decades of shade tree selection by farmers impacts agroforests inter‐ and intraspecific trait diversity, and (iii) which shade tree traits should be considered for achieving farmer priorities. We consolidate literature on Coffea arabica (coffee) and Theobroma cacao (cocoa) agroforestry systems to summarize the role of shade tree functional traits in three key ecosystem functions: soil fertility, microclimate modification and crop productivity. We compile global and regional datasets on tree functional trait diversity to show the functional space of agroforestry tree species compared with the overall functional space observed in plants. Despite, or maybe because of, high shade tree diversity, shade tree trait characterization remains coarse and commonly measured at the community scale in the literature. Based on published trait data, we show that farmers adjust the functional composition of shade trees to increase the recycling of soil nutrients (high leaf nitrogen), the production of wood (skewing towards lower wood densities) and the production of fruits (tendency towards high seed size). Common shade trees in coffee and cocoa systems fall in the mid‐range of leaf acquisitive to conservative strategies, providing evidence that expanding shade tree portfolios can improve, or even accelerate, functions. Synthesis and applications: Based on the agroforestry literature and on trait‐environment relationships, we propose a matrix of shade tree traits that influence desirable agroecosystem outcomes for farmers, which can guide fine‐scale coordination of trait expression and agroforestry functions.

Environmental heterogeneity at two spatial scales affects litter diversity-decomposition relationships.

The effects of biodiversity on ecological processes have been experimentally evaluated mainly at the local scale under homogeneous conditions. To scale up experimentally based biodiversity-functioning relationships, there is an urgent need to understand how such relationships are affected by the environmental heterogeneity that characterizes larger spatial scales. Here, we tested the effects of an 800-m elevation gradient (a large-scale environmental factor) and forest habitat (a fine-scale factor) on litter diversity-decomposition relationships. To better understand local and landscape scale mechanisms, we partitioned net biodiversity effects into complementarity, selection, and insurance effects as applicable at each scale. We assembled different litter mixtures in aquatic microcosms that simulated natural tree holes, replicating mixtures across blocks nested within forest habitats (edge, interior) and elevations (low, mid, high). We found that net biodiversity and complementarity effects increased over the elevation gradient, with their strength modified by forest habitat and the identity of litter in mixtures. Complementarity effects at local and landscape scales were greatest for combinations of nutrient-rich and nutrient-poor litters, consistent with nutrient transfer mechanisms. By contrast, selection effects were consistently weak and negative at both scales. Selection effects at the landscape level were due mainly to nonrandom overyielding rather than spatial insurance effects. Our findings demonstrate that the mechanisms by which litter diversity affects decomposition are sensitive to environmental heterogeneity at multiple scales. This has implications for the scaling of biodiversity-ecosystem function relationships and suggests that future shifts in environmental conditions due to climate change or land use may impact the functioning of aquatic ecosystems.

Biodiversity mitigates drought effects in the decomposer system across biomes

Multiple facets of global change affect the earth system interactively, with complex consequences for ecosystem functioning and stability. Simultaneous climate and biodiversity change are of particular concern, because biodiversity may contribute to ecosystem resistance and resilience and may mitigate climate change impacts. Yet, the extent and generality of how climate and biodiversity change interact remain insufficiently understood, especially for the decomposition of organic matter, a major determinant of the biosphere-atmosphere carbon feedbacks. With an inter-biome field experiment using large rainfall exclusion facilities, we tested how drought, a common prediction of climate change models for many parts of the world, and biodiversity in the decomposer system drive decomposition in forest ecosystems interactively. Decomposing leaf litter lost less carbon (C) and especially nitrogen (N) in five different forest biomes following partial rainfall exclusion compared to conditions without rainfall exclusion. An increasing complexity of the decomposer community alleviated drought effects, with full compensation when large-bodied invertebrates were present. Leaf litter mixing increased diversity effects, with increasing litter species richness, which contributed to counteracting drought effects on C and N loss, although to a much smaller degree than decomposer community complexity. Our results show at a relevant spatial scale covering distinct climate zones that both, the diversity of decomposer communities and plant litter in forest floors have a strong potential to mitigate drought effects on C and N dynamics during decomposition. Preserving biodiversity at multiple trophic levels contributes to ecosystem resistance and appears critical to maintain ecosystem processes under ongoing climate change.

Three novel species and new records of Kirschsteiniothelia (Kirschsteiniotheliales) from northern Thailand.

Kirschsteiniothelia (Kirschsteiniotheliales, Pleosporomycetidae) includes 39 saprobic species recorded from dead or decaying wood in terrestrial and freshwater habitats. This study focuses on exploring Kirschsteiniothelia diversity in woody litter in Thailand. Wood samples were collected from forest areas in Chiang Rai and Chiang Mai Provinces in Thailand and examined for fungal fructifications. Fungal isolates were obtained and their morphological and sequence data were characterised. Micromorphology associated with multilocus phylogeny of ITS, LSU and SSU sequence data identified three isolates as novel species (Kirschsteiniotheliainthanonensis, K.saprophytica and K.zizyphifolii) besides new host records for K.tectonae and K.xishuangbannaensis. The placement of the new taxa and records are supported by morphological illustrations, descriptions and molecular phylogenies and the implications of these findings are discussed. Our findings provide information for understanding Kirschsteiniothelia diversity and ecology.

Functional Diversity Accelerates the Decomposition of Litter Recalcitrant Carbon but Reduces the Decomposition of Labile Carbon in Subtropical Forests

The biodiversity of litter can regulate carbon and nutrient cycling during mixed decomposition. It is common knowledge that the decomposition rates of mixed litters frequently deviate from those predicted for these component litter species. However, the direction and magnitude of the nonadditive effects on the degradation of mixed litters remain difficult to predict. Previous studies have reported that the different carbon fractions of leaf litters responded to litter mixture differently, which may help to explain the ambiguous nonadditive effect of diversity on bulk litter decomposition. Therefore, we conducted decomposition experiments on 32 litter mixtures from seven common tree species to test the responses of different carbon fractions to litter diversity in subtropical forests. We found that the overall mass loss of the mixed litter was faster than that estimated from single species. The relative mixing effects (RMEs) of different carbon fractions exhibited different patterns to litter diversity and were driven by different aspects of litter functional dissimilarity. Soluble carbon fractions decomposed more slowly than expected from single species, while lignin fractions decayed more quickly. Moreover, we found that the RMEs of bulk litter decomposition may be determined by the lignin fraction decomposition. Our findings further support that distinguishing the response of different carbon fractions to litter diversity is important for elucidating the nonadditive effects of total litter decomposition.

Abundance and Diversity of Leaf Litter and Subsoil Arthropods in Four Different Sites of Three Agroecological Zones of Northwest Part of Bangladesh

Leaf litter and subsoil arthropods are biotic factors of an ecosystem that play a significant role in nutrient cycling between soil and vegetation. The present study aimed to explore the abundance and diversity of leaf litter and subsoil arthropods in four different sites of three agroecological zones of the Northwest part of Bangladesh. A total of 1920 individuals belonging to 17 orders, 28 families and 34 species were found in the present study where 1099 individuals (14 orders, 23 families, 28 species) from Rajshahi University Campus (Site A), 259 individuals (6 orders, 7 families, 8 species) from Rajshahi Fruit Research Center (Site B), 354 individuals (7orders, 13 families, 13 species) from Kakon Hat Municipality (Site C) and 208 individuals (5 orders, 10 families, 10 species) from Chalan Beel (Site D) were collected during the period from November 2021 to October 2022. In this study, within the three agroecological zones, the highest number of individuals was recorded in Site A (n=1099, 57.24%) and the lowest number in Site D (n=208, 10.83%). Among 17 orders Coleoptera (624, 32.50%) was the first dominant order, Hymenoptera (414, 21.56%) was the second largest order, followed by Araneae (202, 10.52%) and the least dominant order was Metastigmata (8, 0.42%). Formicidae was the most dominant family among collected 28 families, sharing 376 individuals of the total captured individuals and Staphylinidae, sharing 198 individuals, was the second largest family, whereas Tenebrionidae (n=8), Psychodidae (n=8), and Laelapidae (n=8) were the minor dominant families in this study. Among the total of 34 species, Lasioderma sp. was the most dominant species, sharing 189 individuals with 9.84% of the total collected individuals whereas Alphitobius sp., Psychoda sp., and Hypoaspis sp. were least dominant species, and each species of these three comprised of only 8 members. In this study, 15 species were very common, 5 were common, 7 were fairly common, and 7 were rare. The values of Shannon diversity index (H'), Simpson’s diversity index (I-D), Margalef diversity index (DMg), Menhinick Richness index (DMn), Berger Parker dominance index (d) and Pielou’s evenness index (J') were 3.22, 0.95, 4.37, 0.78, 0.10, respectively. The study was the first attempt to examine the abundance and diversity of leaf litter and subsoil arthropods in four different sites of three agroecological zones in the northwest part of Bangladesh. Further study may be necessary for molecular identification of these species.

Sexual morph of Allophoma tropica and Didymella coffeae-arabicae (Didymellaceae, Pleosporales, Dothidiomycetes), including novel host records from leaf litter in Thailand

ABSTRACT Studying the taxonomy, diversity and host preference of leaf litter inhabiting microfungi contributes towards elucidating hidden taxa, their host affinities and recovering novel life modes dwelling inside forest ecosystems. Leaf litter-inhabiting microfungi also play a crucial role in forest ecosystems through decomposition and nutrient recycling. This study resulted in the introduction of saprobic Didymellaceae microfungi from Doi Tung Forest Reserve, Chiang Rai, northern Thailand. Fungal isolates were characterised based on morphology and molecular phylogeny of the nuclear ribosomal DNA (ITS, LSU) and protein-coding genes (tub2, rpb2). Allophoma tropica and Remotididymella ageratinae are recorded from dead leaves of Nayariophyton zizyphifolium (Malvaceae), and Didymella coffeae-arabicae from Dalbergia cultrata and Afzelia xylocarpa (Fabaceae). This study also reports the sexual morph of Allophoma tropica and Didymella coffeae-arabicae and provides molecular evidence for the first reports of sexual morphs from Thailand.

Interactive effects of microbial functional diversity and carbon availability on decomposition – A theoretical exploration

Microbial functional diversity in litter and soil has been hypothesized to affect the rate of decomposition of organic matter and other soil ecosystem functions. However, there are no clear theoretical expectations on how these effects might change with substrate availability, heterogeneity in the substrate chemistry, and different aspects of functional diversity itself (number of microbial groups vs. distribution of functional traits). To explore how these factors shape the decomposition-diversity relation, we carry out numerical experiments using a flexible reaction network comprising microbial processes and interactions with bioavailable carbon (extracellular degradation, uptake, respiration, growth, and mortality), and ecological processes (competition among the different groups). We also considered diverse carbon substrates, in terms of varying nominal oxidation state of carbon (NOSC). The reaction network was used to test the effects of (i) number of microbial groups, (ii) number of carbon pools, (iii) microbial functional diversity, and (iv) amount of bioavailable carbon. We found that the decomposition rate constant increases with increasing substrate concentration and heterogeneity, as well as with increasing microbial functional diversity or variance of microbial traits, albeit these biological factors are less important. The multivariate dependence of the decomposition rate constant (and other decomposition and microbial growth metrics) on substrate and microbial factors can be described using power laws with exponents lower than one, indicating that diversity effects on decomposition and microbial growth are reduced at high substrate concentration and heterogeneity, or at high microbial diversity.

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.

Assessment of bacterial diversity in the chicken litter: A potent risk to environmental health

Using chicken litter as an organic fertilizer on land is the most common, cheapest and environmentally safest way to manage the latter generated swiftly from the poultry industry. Raw chicken litter has been applied to field soils where various vegetables are cropped to increase yield or productivity. However, the chicken litter frequently come in contact with different environments, such as water, soil, microbes and vegetation. When chickens defecate, their litters, in a few countries, are particularly reused for the next flock, potentially causing cross-contamination. Due to various contact points in the environment, a high probability of bacterial transmission is predicted, which could lead to infection spread in animals and humans. Consumption of contaminated water, food, and meat could lead to the transmission of deadly infections. Microbes in the chicken litter also affect the grazing animals while feeding on fields duly applied with chicken litter as manure. The maximum permissible limits (MPLs) in the chicken litter for land application should not exceed 106-108 CFU/g for Coliform bacteria. Antibiotics are regularly mixed in the diet or drinking water of chicken grown in marketable poultry farms for treating bacterial diseases. Rampant usage of antimicrobials also results in resistant bacteria's survival in animal excreta. Herein, we surveyed the literature to identify the major bacterial genus harboured in the fields applied with chicken manure to increase soil fertility. Our detailed survey identified different bacterial pathogens from chicken litter samples from different investigations. Most studies showed the prevalence of Campylobacter, Salmonella, Enterococcus, E. coli, Bacillus, Comamonas, Proteus and Citrobacter, including many other bacterial species in the chicken litter samples. This article suggested that chicken litter does not meet the standard parameters for direct application as organic fertilizer in the fields. Before being applied to the ground, chicken litter should be treated to lessen the danger of polluting crops or water supplies by reducing the prevalence of harmful bacteria carrying antibiotic-resistance genes.

Agricultural land use weakens the relationship between biodiversity and ecosystem functioning

Leaf litter decomposition is a significant ecosystem process for streams' energy provisioning, while species‐specific decomposition rates often form a continuum from slow to fast decomposing species allowing for resources' availability to stream consumers over a longer time period after leaf fall. Leaf litter mixtures in streams typically comprise leaf species varying in their traits, allowing for litter diversity effects on decomposition. At the same time, agricultural land use, habitat characteristics, water quality and invertebrate composition modulate leaf litter decomposition. To identify leaf litter diversity effects and disentangle the roles of agricultural intensity, habitat characteristics, water quality and invertebrate composition for leaf litter processing in streams, we quantified leaf litter decomposition of three leaf species covering a gradient from slow to fast decomposing species, tested either individually or as a three‐species mixture. The study was conducted over 21 days across 18 streams with a gradient of agricultural intensity (percent agricultural land use) in their catchments. We found leaf litter diversity effects in terms of complementarity under low to intermediate agricultural intensity, given that slow decomposing leaf species decomposed almost twice as fast in the three‐species mixture compared to the observations on individual leaf species. This leaf litter diversity effect decreased with increasing agricultural intensity, suggesting that agriculture weakens the biodiversity–ecosystem functioning relationship. However, pathways by which agriculture affected decomposition differed between single‐species and mixed‐species scenarios. For the single‐species scenario, negative effects of agriculture appeared to be mediated through effects on the proportion of sensitive detritivore species and altered habitat characteristics. For the mixed‐species scenario, altered water quality negatively affected the proportion of sensitive detritivore species, in turn reducing the diversity effect on functioning. Our results suggest that the weakened biodiversity–ecosystem functioning relationship under increasing agricultural intensity might be a significant factor threatening carbon cycling and food web integrity in streams.

Litter and soil biodiversity jointly drive ecosystem functions.

The decomposition of litter and the supply of nutrients into and from the soil are two fundamental processes through which the above- and belowground world interact. Microbial biodiversity, and especially that of decomposers, plays a key role in these processes by helping litter decomposition. Yet the relative contribution of litter diversity and soil biodiversity in supporting multiple ecosystem services remains virtually unknown. Here we conducted a mesocosm experiment where leaf litter and soil biodiversity were manipulated to investigate their influence on plant productivity, litter decomposition, soil respiration, and enzymatic activity in the littersphere. We showed that both leaf litter diversity and soil microbial diversity (richness and community composition) independently contributed to explain multiple ecosystem functions. Fungal saprobes community composition was especially important for supporting ecosystem multifunctionality (EMF), plant production, litter decomposition, and activity of soil phosphatase when compared with bacteria or other fungal functional groups and litter species richness. Moreover, leaf litter diversity and soil microbial diversity exerted previously undescribed and significantly interactive effects on EMF and multiple individual ecosystem functions, such as litter decomposition and plant production. Together, our work provides experimental evidence supporting the independent and interactive roles of litter and belowground soil biodiversity to maintain ecosystem functions and multiple services.

Soil carbon dynamics are linked to tree species growth strategy in a naturally regenerating tropical forest

Secondary tropical forests are increasingly important for their role in the global carbon (C) balance as they can rapidly accumulate aboveground biomass C during regrowth. Substantial amounts of plant-derived carbon are also incorporated into the soil through decomposition processes, but our understanding of soil C dynamics during forest regrowth is limited. Secondary succession is characterised by a shift in tree functional groups from light-demanding to shade-tolerant species over time, which can influence rates of C turnover via differences in litter quality and by modifying the decomposition environment. Changes in decomposition processes in turn affect the amount of organic C stored in the soil or released to the atmosphere as CO2. Consequently, understanding how tree functional composition influences C turnover during decomposition could help us predict soil C storage during tropical forest regrowth. We experimentally explored the relationship between tree functional groups and soil C dynamics (decomposition and respiration) by conducting a litter decomposition experiment across a successional gradient of naturally regenerating tropical forest. We created litter mixtures representing tree communities differing in their shade tolerance, as well as a functionally diverse litter mixture, and observed litter mass loss and soil respiration as measures of C turnover over a 6 month period. Litter from light-demanding species decomposed faster than litter from shade-tolerant species, which was reflected in the pattern of soil respiration. There were no clear patterns of increasing or decreasing rates of litter decay or soil respiration with increasing forest age, but there was an interaction between stand age and litter type which influenced both decomposition and soil respiration rates. Interestingly, soil respiration from the functionally diverse litter mixture was significantly higher in the younger than older forest stands, and the functionally diverse litter mixture decayed more rapidly than expected in one of the younger stands. Our findings highlight the potential importance of functionally diverse plant inputs, as well as the interaction between local environmental attributes and litter type, for soil C dynamics in tropical forests.

Tree diversity effects on litter decomposition are mediated by litterfall and microbial processes

Forest ecosystems are critical for their carbon sequestration potential. Increasing tree diversity has been shown to enhance both forest productivity and litter decomposition. Litter diversity increases litter decomposability by increasing the diversity of substrates offered to decomposers. However, the relative importance of litter decomposability and decomposer community in mediating tree diversity effects on decomposition remains unknown. Moreover, tree diversity modulation of litterfall spatial distribution, and consequently litter decomposition, has rarely been tested. We studied tree diversity effects on leaf litter decomposition and its mediation by the amount of litterfall, litter species richness and decomposability, and soil microorganisms in a large‐scale tree diversity experiment in subtropical China. Furthermore, we examined how litter functional identity and diversity affect leaf litter decomposability. Finally, we tested how leaf functional traits, tree biomass, and forest spatial structure drive the litterfall spatial distribution. We found evidence that tree species richness increased litter decomposition by increasing litter species richness and the amount of litterfall. We showed that soil microorganisms in this subtropical forest perform 84–87% of litter decomposition. Moreover, changes in the amount of litterfall and microbial decomposition explained 19–37% of the decomposition variance. Additionally, up to 20% of the microbial decomposition variance was explained by litter decomposability, while litter decomposability itself was determined by litter functional identity, diversity, and species richness. Tree species richness increased litter species richness and the amount of litterfall (+200% from monoculture to eight‐species neighborhood). We further demonstrated that the amount of species‐specific litterfall increased with increasing tree proximity and biomass, and was modulated by leaf functional traits. These litterfall drivers increased the spatial heterogeneity of litter distribution, and thus litter decomposition. We highlighted multiple biomass‐ and diversity‐mediated effects of tree diversity on ecosystem properties driving forest nutrient cycling. We conclude that considering spatial variability in biotic properties will improve our mechanistic understanding of ecosystem functioning.

Combined addition of plant litter altered remediating effects on petroleum‐contaminated soil in Northern Shaanxi, China

AbstractIn the present study, we assessed whether the nonadditive effects of mixed litter decomposition on soil biological and chemical properties, which was usually recognized in clean soils, could be used to enhance the efficiency of petroleum‐contaminated soil necrophytoremediation. In particular, six common plant species from the petroleum production region of Northern Shaanxi, China were collected, forming nine mixture types. The single and mixed litters were used to treat petroleum‐contaminated soil with a proportion of 45 g kg−1 at 25°C and a constant humidity for 150 days. The possible nonadditive effects on the efficiency of removing contaminants and recovering the damaged soil traits caused by the mixed litter addition were then investigated. The results indicate that monospecific litter treatments significantly increased the degradation rates of petroleum contaminants, the available N and P contents, and the catalase and dehydrogenase activities by 36%–74%, 28%–455%, and 8%–102%, respectively (p &lt; 0.05). The mixed addition of the litters from Lespedeza davurica and Artemisia scoparia or those from Agropyron cristatum and Bromus inermis caused significant synergistic effects, enhancing the overall petroleum component removal, replenishing nutrients (particularly nitrogen) or stimulating enzymatic activities (especially for sucrase, phosphatase, catalase, and urease). The observed values of the corresponding indicators following mixed litter treatment were observed to significantly increase by 12%–18%, 23%–58%, and 9%–24% (p &lt; 0.05), relative to their predicted values, which were calculated based on the observed values from the monospecific litter treatments and the proportion of the litter in the mixture. However, other litter combinations may weaken the remediation effects of the litter addition. In general, a high content of nutrients, primary metabolites (e.g., soluble sugars and amino acids), and the potential bio‐surfactants and co‐metabolized substrates (including terpenoids and flavonoids) of mixed litters enhanced the remediation efficiency of mixed litters. Notably, an increase in the chemical diversity of mixed litter may weaken its synergistic effects on the degradation of petroleum components and the simulation of soil polyphenol oxidase activity. Our results demonstrate that appropriate litter mixing combinations can effectively enhance the efficiency of necrophytoremediation, thus providing new approaches for the more convenient and economical remediation of petroleum‐contaminated soil.