Litter Mass Loss Research Articles

Fauna access outweighs litter mixture effect during leaf litter decomposition

Decomposition rates of litter mixtures reflect the combined effects of litter species diversity, litter quality, decomposers, their interactions with each other and with the environment. The outcomes of those interactions remain ambiguous and past studies have reported conflicting results (e.g., litter mixture richness effects). To date, how litter diversity and soil fauna interactions shape litter mixture decomposition remains poorly understood. Through a sixteen month long common garden litter decomposition experiment, we tested these interaction effects using litterbags of three mesh sizes (micromesh, mesomesh, and macromesh) to disentangle the contributions of different fauna groups categorized by their size at Wuhan botanical garden (subtropical climate). We examined the decomposition of five single commonly available species litters and their full 26 mixtures combination spanning from 2 to 5 species. In total, 2325 litterbags were incubated at the setup of the experiment and partly harvested after 1, 3, 6, 9, and 16 months after exposure to evaluate the mass loss and the combined effects of soil fauna and litter diversity. We predicted that litter mixture effects should increase with increased litter quality dissimilarity, and soil fauna should enhance litter (both single species litter and litter mixtures) decomposition rate. Litter mass loss ranged from 26.9 % to 87.3 %. Soil fauna access to litterbags accelerated mass loss by 29.8 % on average. The contribution of soil mesofauna did not differ from that of soil meso- and macrofauna. Incubation duration and its interactions with litter quality dissimilarities together with soil fauna determined the litter mixture effect. Furthermore, the litter mixture effect weakened as the decomposition progresses. Faunal contribution was broadly additive to the positive mixture effect irrespective of litter species richness or litter dissimilarity. This implies that combining the dissimilarity of mixture species and contributions of different soil fauna provides a more comprehensive understanding of mixed litter decomposition.

Species loss and nitrogen pollution alter litter decomposition dynamics in coastal salt marshes.

Litter decomposition is a central ecosystem function because dead plant biomass plays a critical role in carbon storage, the nitrogen (N) cycle, and as food/habitat for animals and microorganisms. In the face of global change, interactions between organisms that participate in litter decomposition are likely to change due to species loss and N pollution. To understand how these global change factors may interact to alter litter decomposition, we manipulated the detritivore community and N concentrations in a coastal salt marsh for 2 years. We chose to manipulate densities of a dominant, detritivorous snail (Melampus bidentatus) because its population size is expected to decline due to climate change, yet its impact on litter decomposition has not been tested in the field. We measured litter decomposition rates, detritivore densities, and the N concentrations of sediment and litter. We found that endogenous N enrichment (N added live plants before decomposition), exogenous N enrichment (N added to decomposing plants) and higher densities of Melampus increased litter decomposition rates. Linear mixed models further revealed that snails, other detritivores, and soil NH4+ were the best predictors of litter mass loss in the middle stages of decomposition. Notably, exogenous N added to litter already enriched with N further increased mass loss but did not increase litter %N. Our study reveals how global change in the form species loss and N pollution can have palpable impacts on carbon cycling and ecosystem function.

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

Plant litter decomposition is a key process in carbon and nutrient cycling. Among the factors determining litter decomposition rates, the role of soil biota in the decomposition of different plant litter types and its modification by variations in climatic conditions is not well understood. In this study, we used litterbags with different mesh sizes (45 µm, 1 mm and 4 mm) to investigate the effect of microorganisms and decomposer microarthropods on leaf and root litter decomposition along an altitudinal gradient of tropical montane rainforests in Ecuador. We examined decomposition rates, litter C and N concentrations, microbial biomass and activity, as well as decomposer microarthropod abundance over one year of exposure at three different altitudes (1,000, 2,000 and 3,000 m). Leaf litter mass loss did not differ between the 1,000 and 2,000 m sites, while root litter mass loss decreased with increasing altitude. Changes in microbial biomass and activity paralleled the changes in litter decomposition rates. Access of microarthropods to litterbags only increased root litter mass loss significantly at 3,000 m. The results suggest that the impacts of climatic conditions differentially affect the decomposition of leaf and root litter, and these modifications are modulated by the quality of the local litter material. The findings also highlight litter quality as the dominant force structuring detritivore communities. Overall, the results support the view that microorganisms mostly drive decomposition processes in tropical montane rainforests with soil microarthropods playing a more important role in decomposing low-quality litter material.

Abnormal Litter Induced by Typhoon Disturbances Had Higher Rates of Mass Loss and Carbon Release than Physiological Litter in Coastal Subtropical Urban Forest Ecosystems

The decomposition of abnormal litter caused by extreme weather events might play an increasingly important role in carbon and nutrient cycling in forest ecosystems under climate change scenarios, which needs to be fully investigated. In August 2020, the abnormal foliar litter of the goldenrain tree (Koelreuteria bipinnata var. Integrifoliola), the camphor tree (Cinnamomum camphora), and the weeping willow (Salix babylonica) after Typhoon Hagupit disturbance were collected and incubated on the soil surface at the Plant Ecology Research Base at Taizhou University, which is located on the eastern coast of China. Simultaneously, the physiological foliar litter of these three trees collected in the spring litter peak was incubated at the same site. The abnormal litter had higher concentrations of carbon (C), nitrogen (N), and phosphorus (P) and lower concentrations of lignin and cellulose than the physiological litter. The accumulative mass loss rates of abnormal litter in the goldenrain tree, the camphor tree, and the weeping willow during the incubation period increased by 7.72%, 29.78%, and 21.76% in comparison with physiological litter, and the corresponding carbon release increased by 9.10%, 24.15% and 19.55%, respectively. The autumn litter peak period and plum-rain season had higher rates of litter mass loss and carbon release, while the winter nongrowing season had lower rates. Accumulative mass loss, accumulative carbon release, daily mass loss and the daily carbon release of foliar litter were significantly and positively correlated with temperature and initial P concentrations, and significantly and negatively correlated with the initial C/P ratio, lignin/N ratio, and lignin/P ratio (p < 0.05). Compared with the physiological litter, abnormal litter had higher initial substrate quality, which may be the most important factor contributing to their high rates of mass loss and carbon release. The results imply that increasing tropical cyclones under climate change scenarios will facilitate carbon cycling in coastal urban forest ecosystems.

Disentangling drivers of litter decomposition in a multi-continent network of tree diversity experiments

Litter decomposition is a key ecosystem function in forests and varies in response to a range of climatic, edaphic, and local stand characteristics. Disentangling the relative contribution of these factors is challenging, especially along large environmental gradients. In particular, knowledge of the effect of management options, such as tree planting density and species composition, on litter decomposition would be highly valuable in forestry. In this study, we made use of 15 tree diversity experiments spread over eight countries and three continents within the global TreeDivNet network. We evaluated the effects of overstory composition (tree identity, species/mixture composition and species richness), plantation conditions (density and age), and climate (temperature and precipitation) on mass loss (after 3 months and 1 year) of two standardized litters: high-quality green tea and low-quality rooibos tea. Across continents, we found that early-stage decomposition of the low-quality rooibos tea was influenced locally by overstory tree identity. Mass loss of rooibos litter was higher under young gymnosperm overstories compared to angiosperm overstories, but this trend reversed with age of the experiment. Tree species richness did not influence decomposition and explained almost no variation in our multi-continent dataset. Hence, in the young plantations of our study, overstory composition effects on decomposition were mainly driven by tree species identity on decomposer communities and forest microclimates. After 12 months of incubation, mass loss of the high-quality green tea litter was mainly influenced by temperature whereas the low-quality rooibos tea litter decomposition showed stronger relationships with overstory composition and stand age. Our findings highlight that decomposition dynamics are not only affected by climate but also by management options, via litter quality of the identity of planted trees but also by overstory composition and structure.

Soil mite communities structure (Acari, Mesostigmata) during litter decomposition of seven tree species in pure Scots pine stands (Pinus sylvestris L.) growing on a reclaimed post‐industrial area

AbstractOur knowledge about mites, including mesostigmatids, compared to their significant role in soil‐forming processes on post‐industrial areas, is currently insufficient. Therefore, our study aim was to analyze the succession of mesostigmatid communities in relation to litter decomposition of seven tree species [Acer pseudoplatanus L., Alnus glutinosa (L.) Gaertn., Fagus sylvatica L., Pinus sylvestris L., Prunus serotina Ehrh., Quercus rubra L., Robinia pseudoacacia L.] in pure Scots pine stands growing on a reclaimed spoil heap. In December 2011, 1439 litterbags were placed on plots and collected after ca. 3, 6, 9, 13, 19, 25, 31, 37 months since the experiment started. In total, we recorded 9653 mites classified into 67 taxa. The mesostigmatid abundance was affected by percentage initial litter mass loss. Interestingly, litter type shaped species richness and diversity, but not abundance. The highest abundance, almost two‐times higher compared to other tree species, was recorded in Prunus serotina litter (352.73 ± 105.22 ind.; calculated per 100 g of dry litter mass) and the lowest in Quercus rubra (81.23 ± 9.82 ind.). Furthermore, the lowest richness (2.39 ± 0.07; calculated per sample) and diversity (0.33 ± 0.02; calculated per sample) was recorded in Pinus sylvestris litter, therefore, our results are in contradiction to the home‐field advantage assumptions that the ‘home’ litter has a positive effect on soil fauna structure compared to the ‘foreign’ litter. Nevertheless, the greatest abundance share of Asca bicornis and Amblyseius tubae, the most numerous species, was recorded for Pinus sylvestris litter.

Environmental Impact of Triclopyr on Habitat Quality in Boreal Rights-of-Way.

The indirect effects of herbicides on habitat quality in boreal ecoregions remain poorly understood. Herbicides are commonly applied on boreal rights-of-way to control vegetation below power lines, where they can indirectly enter the soil ecosystem after leaf abscission. Key soil processes such as litter decomposition and soil nutrient cycling can be influenced by altering litter chemistry and/or impacting decomposer species. Disruption of these soil processes could lead to changes in ecosystem health of boreal systems. The indirect impacts of triclopyr on habitat quality of treated boreal rights-of-way were examined through litter mass loss and quality (carbon-to-nitrogen ratios) and the response of boreal invertebrates (Folsomia candida and Oppia nitens) in microcosms and avoidance tests. Litter breakdown rates were not significantly different within a year of treatment. However, we did observe nitrogen profile differences between field-treated and untreated samples, which likely resulted from triclopyr-induced repression of natural leaf senescence processes. At field application rates, there were no differences in survival and reproduction rates of F. candida, which is key in litter breakdown. The triclopyr concentrations that caused 50% of tested F. candida and O. nitens to avoid treated litter were above field application rates. Therefore, field application rates of triclopyr are not expected to impair habitat quality and ecosystem services of boreal ecoregions based on the parameters we evaluated. Our study improves understanding of the effects of herbicide application on habitat quality and is critical for responsible herbicide use on boreal rights-of-way. Environ Toxicol Chem 2022;41:2955-2967. © 2022 SETAC.

Effects of litter species and genetic diversity on plant litter decomposition in coastal wetland

With the enhancement of carbon sink capacity and the intensification of biodiversity change in coastal wetlands, previous studies have well studied the relationship between species diversity and litter decomposition, a vital process of carbon cycling. However, previous studies ignored the importance of genetic diversity, which restricted our comprehensive understanding of the effects of biodiversity loss on ecosystem functions. Here, we manipulated different richness levels with litters of eight common species of coastal wetland plants and eight different genotypes of common reed (Phragmites australis) to explore the effects of species and genetic diversity on litter decomposition. We found the litter mass loss of mixtures was significantly lower than the average mass loss of single litters (ANOVA, p < 0.05), suggesting higher species and genetic diversity had negative effects on plant litter decomposition. The negative effects were also supported by the t-test that the observed mass loss was significantly lower than expected at both species and genetic diversity levels, which also identified that antagonistic effects occurred. In addition, the functional diversity of initial litter qualities, such as lignin content and the C/P ratio, had a significant correlation with the negative effects at species and genetic levels, whereas phylogenetic diversity did not reveal such a correlation, implying functional diversity might better predict the effects of diversity changes on litter decomposition in coastal wetlands at both species and genetic levels. Furthermore, the presence of specific species or genotype litters, such as Scorzonera mongolica, Imperata cylindrica and the common reed numbered CN2026, could also predict negative effects. In this study, we found that genetic diversity influenced litter decomposition as much as species diversity, and we provided significant implications for predicting the effect of wetland biodiversity loss or conservation on carbon sink capacity.

Experimental Precipitation Reduction Slows Down Litter Decomposition but Exhibits Weak to No Effect on Soil Organic Carbon and Nitrogen Stocks in Three Mediterranean Forests of Southern France

Forest ecosystems are some of the largest carbon (C) reservoirs on earth. Pinus halepensis Mill., Quercus ilex L. and Quercus pubescens Willd. represent the dominant tree cover in the Mediterranean forests of southern France. However, their contributions to the French and global forest C and nitrogen (N) stocks are frequently overlooked and inaccurately quantified and little is known about to what extent the ongoing climate change can alter these stocks. We quantified the soil organic C (SOC) and N (SN) stocks in Mediterranean forests dominated by these tree species and evaluated to what extent an experimental precipitation reduction (about −30% yearly) affects these stocks and the litter decomposition efficiency. Litter mass losses were 55.7, 49.8 and 45.7% after 24 months of decomposition in Q. ilex, Q. pubescens and P. halepensis forests, respectively, and were 19% lower under drier climatic conditions. The SOC stocks were 14.0, 16.7 and 18.5 Mg ha−1 and the SN stocks were 0.70, 0.93 and 0.88 Mg ha−1 in Q. ilex, Q. pubescens and P. halepensis forests, respectively. The shallowness and stoniness of these Mediterranean forests could explain these limited stocks. By distinguishing the organic from the organo–mineral layer, we showed 74% less SOC in the organic layer of the P. halepensis forest under drier conditions, while no difference was detected in the organo–mineral layer or in the two oak forests. This last finding deserves further investigation and points out the necessity to distinguish the organic from the organo–mineral layer to detect the first impacts of climate change on SOC stocks.

Soil warming delays leaf litter decomposition but exerts no effect on litter nutrient release in a subtropical natural forest over 450 days

Litter decomposition is a fundamental ecosystem process, influencing soil carbon storage, nutrient availability, and forest productivity. Climate change may affect litter decomposition and thus nutrient dynamics via altering plant phenology, litter quality, and the composition of soil microbial communities. However, the effects of climate change on litter decomposition are not well understood, especially in tropical and subtropical forest ecosystems, which are less temperature limited. We conducted a manipulative study to assess how soil warming affects litter decomposition rates and its relation to litter chemistry, extracellular enzyme activities, and microbial biomass in an evergreen broad-leaved forest in subtropical China. The temperature at 0–10 cm soil depth was experimentally increased by 4 °C, starting from June 2016 to October 2017. Soil warming did not affect litter mass loss during the initial stage (0–270 day), but reduced litter mass loss by 12.9 % at the later stages (days 350 to 450). Structural equation modeling showed that litter moisture content was reduced by warming, but this was not the main effector leading to the reduction in late-stage litter decomposition in the warming treatment. The model suggested that warming reduced litter decomposition rates likely indirectly, through its negative effects on extractable organic carbon and microbial biomass (e.g., microbial carbon and nitrogen), and on litter enzyme activities (a composite variable of β-glucosidase, cellobiohydrolase, acid phosphatase, and phenoloxidase). These results show that warming may slow down litter carbon cycling, but this subtropical forest ecosystem did not affect litter N and P cycling and soil nutrient availability.

Enzyme kinetics inform about mechanistic changes in tea litter decomposition across gradients in land-use intensity in Central German grasslands.

Grassland ecosystems provide important ecosystem services such as nutrient cycling and primary production that are affected by land-use intensity. To assess the effects of land-use intensity, operational and sensitive ecological indicators that integrate effects of grassland management on ecosystem processes such as organic matter turnover are needed. Here, we investigated the suitability of measuring the mass loss of standardized tea litter together with extracellular enzyme kinetics as a proxy of litter decomposition in the topsoil of grasslands along a well-defined land-use intensity gradient (fertilization, mowing, grazing) in Central Germany. Tea bags containing either green tea (high-quality litter) or rooibos tea (low-quality litter) were buried in 5 cm soil depth. Litter mass loss was measured after three (early-stage decomposition) and 12 months (mid-stage decomposition). Based on the fluorescence measurement of the reaction product 4-methylumbelliferone, Michaelis-Menten enzyme kinetics (Vmax: potential maximum rate of activity; Km: substrate affinity) of five hydrolases involved in the carbon (C)-, nitrogen (N)- and phosphorus (P)-cycle (β-glucosidase (BG), cellobiohydrolase (CBH), cellotriohydrolase (CTH), 1,4-β-N-acetylglucosaminidase (NAG), and phosphatase (PH)) were determined in tea litter bags and in the surrounding soil. The land-use intensity index (LUI), summarizing fertilization, mowing, grazing, and in particular the frequency of mowing were identified as important drivers of early-stage tea litter decomposition. Mid-stage decomposition was influenced by grazing intensity. The higher the potential activity of all measured C-, N- and P-targeting enzymes, the higher was the decomposition of both tea litters in the early-phase. During mid-stage decomposition, individual enzyme parameters (Vmax of CTH and PH, Km of CBH) became more important. The tea bag method proved to be a suitable indicator which allows an easy and cost-effective assessment of land-use intensity effects on decay processes in manged grasslands. In combination with enzyme kinetics it is an appealing approach to identify mechanisms driving litter break down.

Effects of initial leaching for estimates of mass loss and microbial decomposition-Call for an increased nuance.

Decomposition is essential to carbon, nutrient, and energy cycling among and within ecosystems. Several methods have been proposed for studying litter decomposition by using a standardized and commercially available substrate. One of these methods is the Tea Bag Index (TBI) which uses tea bags (green and rooibos tea) incubated for ~90 days. The TBI is now applied all over the globe, but despite its usefulness and wide application, the TBI (as well as other methods) does not explicitly account for the differences in potential loss of litter mass due to initial leaching in habitats with large differences in moisture. We, therefore, studied the short‐term mass losses (3–4 h) due to initial leaching under field and laboratory conditions for green and rooibos tea using the TBI and contextualized our findings using existing long‐term mass loss (90 days) in the field for both aquatic and terrestrial environments. For both tea litter types, we found a fast initial leaching rate, which could be mistaken for decomposition through microbial activity. This initial leaching was higher than the hydrolyzable fraction given in the description of the TBI. We also found that leaching increased with increasing temperature and that leaching in terrestrial environments with high soil moisture (>90%) is almost as large as in aquatic environments. When comparing our findings to long‐term studies, we found that up to 30–50% of the mass loss of green tea reported as decomposition could be lost through leaching alone in high moisture environments (>90% soil moisture and submerged). Not accounting for such differences in initial leaching across habitats may lead to a systematic overestimation of the microbial decomposition in wet habitats. Future studies of microbial decomposition should adjust their methods depending on the habitat, and clearly specify the type of decomposition that the study focuses on.

Effects of Forest Gaps on Abies faxoniana Rehd. Leaf Litter Mass Loss and Carbon Release along an Elevation Gradient in a Subalpine Forest

Changes in the microenvironment induced by forest gaps may affect litter decomposition, yet it is unclear how the gap effects respond to altitudinal and seasonal differences. Here, a four-year litterbag decomposition experiment along an elevation gradient (3000, 3300, 3600 m) was conducted in an Abies faxoniana Rehd. subalpine forest of southwestern China, to assess the potential seasonal effects of forest gaps (large: ≈250 m2, middle: ≈125 m2, small: ≈40 m2 vs. closed canopy) on litter mass loss and carbon release at different elevations. We found that the A. faxoniana litter mass loss and carbon release reached 50~53 and 58~64% after four years of decomposition, respectively. Non-growing seasons (November to April) had a greater decline than the growing seasons (May to October). Litter in the forest gaps exhibited significantly higher mass loss than that under the closed canopy, and the decomposition constant (k) exhibited a gradually declining trend from large gaps, middle gaps, small gaps to closed canopy. Moreover, more significant differences of gap on both carbon content and release were observed at the 3600 m site than the other two elevations. Our findings indicate that (i) a rather high mass loss and carbon release during the decomposition of A. faxoniana litter was observed at high elevations of the subalpine forest subjected to low temperatures in the non-growing seasons and (ii) there were stimulative effects of forest gaps on litter mass loss and carbon release in early decomposition, especially in the non-growing seasons, driven by fewer freeze–thaw cycles when compared to the closed canopy, which diminished at the end of the experiment. The results will provide crucial ecological data for further understanding how opening gaps as a main regeneration method would induce changes in carbon cycling in subalpine forest ecosystems.

Aridec: an open database of litter mass loss from aridlands worldwide with recommendations on suitable model applications

Abstract. Plant litter decomposition in terrestrial ecosystems involves the physical and chemical breakdown of organic matter. Development of databases is a promising tool for achieving a predictive understanding of organic matter degradation at regional and global scales. In this paper, we present aridec, a comprehensive open database containing litter mass loss data from aridlands across the world. We describe in detail the structure of the database and discuss general patterns in the data. Then, we explore what are the most appropriate model structures to integrate with data on litter decomposition from the database by conducting a collinearity analysis. The database includes 184 entries from aridlands across the world, representing a wide range of climates. For the majority of the data gathered in aridec, it is possible to fit models of litter decomposition that consider initial organic matter as a homogenous reservoir (one pool models), as well as models with two distinct types of organic compounds that decompose at different speeds (two pool models). Moreover, these two carbon pools can either decompose without interaction (parallel models) or with matter transfer from a labile pool to a slowly decomposing pool after transformation (series models). Although most entries in the database can be used to fit these models, we suggest that potential users of this database test identifiability for each individual case as well as the number of degrees of freedom. Other model applications that are not discussed in this publication might also be suitable for use with this database. Lastly, we give some recommendations for future decomposition studies to be potentially added to this database. The extent of the information included in aridec in addition to its open-science approach makes it a great platform for future collaborative efforts in the field of aridland biogeochemistry. The aridec version 1.0.2 is archived and publicly available at https://doi.org/10.5281/zenodo.6600345 (Sarquis et al., 2022), and the database is managed under a version-controlled system and centrally stored in GitHub (https://github.com/AgustinSarquis/aridec, last access: 31 May 2022).

The crucial role of blue light as a driver of litter photodegradation in terrestrial ecosystems

Background and aimWherever sunlight reaches litter, there is potential for photodegradation to contribute to decomposition. Although recent studies have weighed the contribution of short wavelength visible and ultraviolet (UV) radiation as drivers of photodegradation, the relative importance of each spectral region across biomes and plant communities remains uncertain.MethodsWe performed a systematic meta-analysis of studies that assessed photodegradation through spectrally selective attenuation of solar radiation, by synthesizing 30 published studies using field incubations of leaf litter from 110 plant species under ambient sunlight.ResultsGlobally, the full spectrum of sunlight significantly increased litter mass loss by 15.3% ± 1% across all studies compared to darkness. Blue light alone was responsible for most of this increase in mass loss (13.8% ± 1%), whereas neither UV radiation nor its individual constituents UV-B and UV-A radiation had significant effects at the global scale, being only important in specific environments. These waveband-dependent effects were modulated by climate and ecosystem type. Among initial litter traits, carbon content, lignin content, lignin to nitrogen ratio and SLA positively correlated with the rate of photodegradation. Global coverage of biomes and spectral regions was uneven across the meta-analysis potentially biasing the results, but also indicating where research in lacking.ConclusionsAcross studies attenuating spectral regions of sunlight, our meta-analysis confirms that photodegradation is a significant driver of decomposition, but this effect is highly dependent on the spectral region considered. Blue light was the predominant driver of photodegradation across biomes rather than UV radiation.

Litter quality and stream physicochemical properties drive global invertebrate effects on instream litter decomposition

Plant litter is the major source of energy and nutrients in stream ecosystems and its decomposition is vital for ecosystem nutrient cycling and functioning. Invertebrates are key contributors to instream litter decomposition, yet quantification of their effects and drivers at the global scale remains lacking. Here, we systematically synthesized data comprising 2707 observations from 141 studies of stream litter decomposition to assess the contribution and drivers of invertebrates to the decomposition process across the globe. We found that (1) the presence of invertebrates enhanced instream litter decomposition globally by an average of 74%; (2) initial litter quality and stream water physicochemical properties were equal drivers of invertebrate effects on litter decomposition, while invertebrate effects on litter decomposition were not affected by climatic region, mesh size of coarse-mesh bags or mycorrhizal association of plants providing leaf litter; and (3) the contribution of invertebrates to litter decomposition was greatest during the early stages of litter mass loss (0-20%). Our results, besides quantitatively synthesizing the global pattern of invertebrate contribution to instream litter decomposition, highlight the most significant effects of invertebrates on litter decomposition at early rather than middle or late decomposition stages, providing support for the inclusion of invertebrates in global dynamic models of litter decomposition in streams to explore mechanisms and impacts of terrestrial, aquatic, and atmospheric carbon fluxes.

LEAF LITTER WITH CONTRASTING CHEMICAL TRAITS AND DECOMPOSITION PROMOTE SIMILAR BENTHIC MACROINVERTEBRATES COMMUNITIES

In aquatic ecosystems, allochthonous inputs of leaf litter are common substrates for the invertebrates communities. The quality and physical structure of these substrates are expected to strongly determine benthic invertebrates structure and functioning. Therefore, we carried out an experiment to evaluate the association between these organisms and the chemical traits of leaf litter from 16 restinga plant species in Jurubatiba lagoon, a coastal aquatic ecosystem at Restinga de Jurubatiba National Park. After 123 days, litter mass loss varied from 14 - 30%, indicating that decomposition was in the initial stage for most species. Litter converged to have a similar nutritional quality after this time submerged. Initial K concentration positively affected, whereas initial lignin and C concentration negatively affected species richness and diversity. It indicates that nutrients attract whereas structural compounds limit benthic species colonization. Chemical compounds such as C, nutrients (N, P, K and Na), lignin and cellulose tended to be positively associated with the dominant taxa (Chironominae n.i. and Heleobia australis) and functional feeding groups (scrapers and collector-gatherers). However, no significant associations were detected by the redundancy analyses. We may conclude that litter quality affect benthic structure, but not community composition nor FFG distribution at Jurubatiba lagoon. The benthic composition and FFG may be randomly distributed among litter substrates or may be better explained by some other litter aspect(s) different from those considered in this study. Future studies may also consider the temporal dynamic of litter colonization to better elucidate the relationship between litter traits and invertebrate community.

Invasive Plants and Species Richness Impact Litter Decomposition in Riparian Zones.

Natural ecosystems generally include litter decomposition as part of the natural cycle since the material properties and the environment greatly influence the decomposition rate. The invasion of exotic plants alters the species diversity and growth characteristics of plant communities, but its impact on litter decomposition is unknown in the riparian zone. This study examines how invasive plants affect the early stages of litter decomposition and how species richness impacts them. This experiment involved a random litter mixture of exotic (Alternanthera philoxeroides and Bidens pilosa) and native species in the riparian zone of the Three Gorges Dam Reservoir in China. There were 43 species mixture types, with various species richness ranging from 1 to 6. Litterbags were placed in the hydro-fluctuation zone and terrestrial zone, where they decomposed over the course of 55 days. Invasive plants decompose rapidly compared to native plants (35.71% of the remaining mass of the invasive plant). The invasive plant A. philoxeroides has the potential to accelerate native plant decomposition (0.29 of non-added synergetic effect), but Bidens pilosa cannot. Nonetheless, species richness had little effect on the decomposition rate. These effects are dependent upon differences in chemical functional characteristics among the species. The initial traits of the plants, specifically C, N, and C/N, were significantly and linearly correlated with the loss of mixed litter mass and mixing effect strength (P < 0.01). In addition, submergence decomposition conditions reduce the disturbance of invasive plants and predict decomposition rates based on litter characteristics. Invasive plants can therefore impact the material cycle of an ecosystem. There is a need to examine decomposition time, which may also involve considering other factors.

The influence of increased precipitation and nitrogen deposition on the litter decomposition and soil microbial community structure in a semiarid grassland

Litter decomposition is a major method in which nutrients are recycled, especially carbon and nitrogen elements, in terrestrial ecosystems. However, how the responses of litter quality and soil microbial communities to global changes alter litter decomposition remains unclear. A 4-year field manipulative experiment based on the litterbag method was conducted in a typical temperate semiarid grassland in China to explore how increased precipitation and nitrogen deposition affect decomposition processes via litter quality and soil microbial communities. Our results showed that water and nitrogen addition treatments could accelerate litter carbon release and promote mass loss through different pathways. Water addition had a direct positive effect on litter decomposition. However, nitrogen addition could indirectly promote litter decomposition by improving litter quality and increasing the bacterial and fungal ratios. The water addition treatment increased litter mass loss by 7.37 %, and the N addition treatments increased litter mass loss by 5.83 %–16.93 %. Moreover, water and nitrogen additions had antagonistic effects on litter decomposition. These findings revealed that litter quality and the soil bacterial to fungal ratio were the factors controlling litter decomposition. The changes in precipitation and nitrogen deposition will impact ecosystem carbon and nitrogen cycling by altering litter decomposition processes in semiarid grassland ecosystems under the context of climate change.

The role of Collembola for litter decomposition under minimum and conventional tillage

AbstractBackgroundThe role of soil mesofauna in decomposition processes still is debated and this applies in particular to arable systems.AimThis study investigates the role of Collembola in decomposition processes of crop residues in two different tillage systems.MethodsWe conducted a litterbag experiment in a long‐term field site in Germany managed by conventional tillage (CT; mouldboard ploughing) and minimum tillage (MT). Litterbags filled with maize leaf litter of two mesh sizes (2 mm and 48 μm) were used. Litterbags were buried at 23 cm (CT) and 5–8 cm (MT), and retrieved after 2, 5 and 7 months. Litter mass, concentrations of carbon and nitrogen, litter C/N ratio as well as the abundance and community structure of Collembola and the incorporation of maize‐derived carbon into Collembola were investigated.ResultsMesofauna enhanced the loss of litter carbon, while litter mass loss was reduced. Litter C/N ratio in MT was generally lower than that in CT and decreased faster in litterbags with coarse mesh size. Abundance of Collembola in litterbags in CT exceeded that in MT, but species composition remained unaffected by tillage. Overall, Collembola effectively colonised the litter irrespective of tillage system, but benefited in particular from translocation deeper into the soil by conventional tillage.ConclusionsMesofauna accelerates litter carbon loss and increases litter nitrogen accumulation irrespective of tillage system. This may reduce nitrogen losses due to leaching in winter and facilitate nitrogen capture from decomposing litter material by crops in the following season, thereby contributing to the sustainable management of arable systems.