Changes In Litter Quality Research Articles

Indirect effects of soil warming on litter decomposition via changes in litter quality of dominant tree species in three cool-temperate forests

Indirect effects of soil warming on litter decomposition via changes in litter quality of dominant tree species in three cool-temperate forests

Resolving the Intricate Effects of Multiple Global Change Drivers on Root Litter Decomposition.

Plant roots represent about a quarter of global plant biomass and constitute a primary source of soil organic carbon (C). Yet, considerable uncertainty persists regarding root litter decomposition and their responses to global change factors (GCFs). Much of this uncertainty stems from a limited understanding of the multifactorial effects of GCFs and it remains unclear how these effects are mediated by litter quality, soil conditions and microbial functionality. Using complementary field decomposition and laboratory incubation approaches, we assessed the relative controls of GCF-mediated changes in root litter traits and soil and microbial properties on fine-root decomposition under warming, nitrogen (N) enrichment, and precipitation alteration. We found that warming and N enrichment accelerated fine-root decomposition by over 10%, and their combination showed an additive effect, while precipitation reduction suppressed decomposition overall by 12%, with the suppressive effect being most significant under warming-alone and N enrichment-alone conditions. Significantly, changes in litter quality played a dominant role and accelerated fine-root decomposition by 15% ~ 18% under warming and N enrichment, while changes in soil and microbial properties were predominant and reduced decomposition by 7% ~ 10% under precipitation reduction and the combined warming and N enrichment. Examining only the decomposition environment or litter properties in isolation can distort global change effects on root decomposition, underestimating precipitation reduction impacts by 38% and overstating warming and N effects by up to 73%. These findings highlight that the net impact of GCFs on root litter decomposition hinges on the interplay between GCF-modulated root decomposability and decomposition environment, as well as on the synergistic or antagonistic relationships among GCFs themselves. Our study emphasizes that integrating the legacy effects of multiple GCFs on root traits, soil conditions and microbial functionality would improve our prediction of C and nutrient cycling under interactive global change scenarios.

Shrub effects on the decomposition microenvironment and changes in litter quality have opposing effects on litter decomposition

Increasing abundance of tall deciduous shrubs has been shown to affect tundra soil properties, which may further affect carbon and nitrogen cycling in these soils, including through effects on litter decomposition. These tall deciduous shrubs produce a higher quantity of litter, and also a different quality of litter, than tundra species in non-shrub dominated tundra, both of which may affect community-wide decomposition rates. We examined how presence of tall deciduous shrubs, including resulting increases in litter quantity, affects litter decomposition through effects on both the decomposition environment and on litter composition. In a factorial experiment, we modified the decomposition environment by manipulating both the abundance of tall deciduous shrubs (present/absent) and their litter (absent, natural, and doubled). In each environment we decomposed litter of the tall deciduous shrub, Betula glandulosa and two other dominant species in our study area; Salix reticulata, a dwarf deciduous shrub, and Carex consimilis, a graminoid. We report that while tall Betula shrub presence reduced decomposition rates, decomposition was not affected by manipulations of litter quantity. Although litter decomposed slower under deciduous shrubs, B. glandulosa litter decomposed faster than the litter of the other dominant tundra plant species. However, the reduction in decomposition rates due to tall deciduous shrub presence and higher decomposition rates of B. glandulosa litter in comparison to other plant species were of the same magnitude and these opposing effects may result in little to no change of shrub encroachment on litter decomposition rate overall.

Variations in trophic niches of soil microarthropods with elevation in two distant mountain regions in Eurasia as indicated by stable isotopes (15N, 13C)

Knowledge on the trophic niche of animal species is important for understanding their coexistence and hence animal diversity. Trophic niches have been shown to vary with environmental conditions, but consequences of trophic niche shifts for food-web structure and functioning are little studied and this applies in particular for belowground communities. Here, using stable isotopes (15N, 13C), we investigated shifts in trophic niches of oribatid mites as model soil animal taxon along elevational gradients of two mountain ranges in Eurasia, the Alps in Austria and Changbai Mountain in China. The results showed pronounced differences in the use of basal resources (Δ13C values) and trophic positions (Δ15N values) between the two mountains due to the different parent rock with calcareous soils in the Alps and basalt bedrock on Changbai Mountain. Further, trophic positions changed with altitude, primarily related to changes in litter quality. Differences in trophic niches of oribatid mites between the two mountains were related to differences in functional traits such as body mass and reproductive mode. Generally, stable isotope values closely correlated with body mass underlining the importance of morphological characteristics as well as the parent rock for variations in trophic niches. Moreover, stable isotope values differed between parthenogenetic and sexual species, but this depended on mountain and parent rock, with higher trophic plasticity in parthenogenetic species on Changbai Mountain than in the Alps. Overall, our findings highlight the decisive role of parent rock in structuring montane soil food webs and provide novel insight into factors responsible for shifts in trophic niches in soil invertebrates.

Litter quality controls tradeoffs in soil carbon decomposition and replenishment in a subtropical forest

Abstract Species‐rich forests can produce litter of varying carbon (C) and nitrogen (N) composition (i.e. quality), which can affect decomposition and play a central role in long‐term soil organic carbon (SOC) accumulation. However, how differences in litter quality affect SOC decomposition and formation remains unclear over the full litter decomposition trajectory. We followed the in situ complete decomposition of added 13C‐labelled high‐ (low C:N) and low‐quality (high C:N) leaf‐litter and its effect on particulate organic matter (POM) and mineral‐associated organic matter (MAOM) fractions over 2 years in a natural subtropical forest. We found that during early stages of decomposition, low‐quality litter inputs decreased SOC via a positive priming effect (i.e. new C inputs favoured decomposition of native SOC), but these SOC losses were offset by SOC gains observed via a negative priming effect during decomposition of high‐quality litter. In contrast, this pattern reversed during late stages of decomposition—SOC losses via a positive priming effect induced by high‐quality litter were offset by SOC gains via a negative priming effect induced by low‐quality litter. Over the full decomposition of litter, both high‐ and low‐quality litter stimulated microbial breakdown of SOC tied to POM, but also replenished more persistent SOC that associated with soil minerals (MAOM). Altogether, we observed that low‐quality litter formed twice as much new SOC as high‐quality litter (24% vs. 12% of added litter‐C). We extend the notion of the priming effect from primarily a negative role promoting losses of native SOC, to a functional role that can replenish persistent SOC. Synthesis. Our measurements raise the possibility that, in species‐rich forests, high‐ and low‐quality litter decomposition play opposite but dynamically complementary roles in renewing POM—both by inducing its decomposition and formation—while exclusively favouring MAOM formation, which can help explain how differences in litter quality favour SOC accumulation and persistence. Global change factors that shift plant community composition may ultimately affect the fate of soil C, as changes in litter quality may force soil transitions from sinks to sources or sources to sinks of atmospheric CO2.

Investigating the response of soil nitrogen cycling to grass invasion

In heathlands, high mineral N input causes replacement of Calluna vulgaris, the dominant plant, by fast-growing grasses such as Molinia caerulea. The vegetation shift signifies altered litter quality from low- to high-quality litter due to differences in lignin content. Litter quality usually affects decomposition processes, which can, in turn, alter nutrient cycling. Therefore, the change in plant dominance in this ecosystem possibly alters soil carbon and nutrient cycles, and consequently, ecosystem services (e.g. biodiversity conservation, groundwater recharge, …). We hypothesise that, because of its higher litter quality, nutrient turnover becomes faster with grass encroachment. We tested this hypothesis in a field set-up consisting of 14 plots presenting a gradient of increasing grass dominance (from 0% to 100%). We measured nine soil parameters and assessed possible associations between grass dominance and the soil parameters using multivariate analysis and linear mixed models. We found that grass dominance significantly impacted net N mineralisation and the root biomass. Our results showed very low net N mineralisation rates (0.09 ± 0.04 mg N (kg soil)−1 day−1) and relative nitrification rates (1.99 ± 0.62%). At high grass levels, acid phosphatase activity was significantly lower than at lower grass percentages. These results show that grass encroachment has a minimal impact on heathland soil biochemistry at this point. Still, we consider that it may take many years to translate a change in litter quality and dynamics into a change in soil functioning.

Legacy Effect of Long-Term Elevated CO2 and Warming on Soil Properties Controls Soil Organic Matter Decomposition

Plant litter quality is one of the key factors that control soil organic matter (SOM) decomposition. Under climate change, although significant change in litter quality has been intensively reported, the effect of litter quality change on SOM decomposition is poorly understood. This limits our ability to model the dynamics of soil carbon under climate change. To determine the effect of litter quality and soil property change on SOM decomposition, we performed a controlled, reciprocal transplant and litter decomposition experiments. The soils and plant litters were collected from a long-term field experiment, where four treatments were designed, including: (1) the control without warming at ambient CO2; (2) elevated atmospheric CO2 up to 500 ppm (C); (3) warming plant canopy by 2 °C (T); (4) elevated CO2 plus warming (CT). We found that elevated CO2 and warming altered the litter quality significantly in terms of macronutrients’ content and their stoichiometry. Elevated CO2 decreased the concentration of N in rice and wheat straw, while warming decreased the concentration of N and K in wheat straw. However, the change in plant litter quality did not lead to a shift in SOM decomposition. On the contrary, the legacy effect of long-term elevated CO2 and warming on soil properties dominated the decomposition rate of SOM. Elevated atmospheric CO2 suppressed SOM decomposition mainly by increasing phosphorous availability and lowering the soil C/N, fungi/bacteria ratio, and N-acetyl-glucosaminidase activity, while warming or elevated CO2 plus warming had no effect on SOM decomposition. Our results demonstrated that the changes in soil property other than litter quality control the decomposition of SOM under climate change, and soil property change in respond to climate change should be considered in model developing to predict terrestrial soil carbon dynamics under elevated atmospheric CO2 and warming.

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

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

Plant above-ground biomass and litter quality drive soil microbial metabolic limitations during vegetation restoration of subtropical forests

Changes in litter quality (carbon:nitrogen, C:N) and above-ground biomass (AGB) following vegetation restoration significantly impact soil physicochemical properties, yet their effects on soil microbial metabolic limitations remain unclear. We measured litter quality, AGB, soil physicochemical properties, and extracellular enzyme activity (EEA) along a vegetation restoration gradient (7, 14, 49, 70 years, and nearly climax evergreen broadleaved forests) in southern China. We also evaluated soil microbial metabolic limitations by a vector analysis of the EEA. Results revealed the soil microbial metabolisms were co-limited by C and phosphorus (P). The microbial C limitation initially decreased (before 14 years) and then increased, while the microbial P limitation initially increased (before 49 years) and then decreased. Partial least squares path modeling (PLS-PM) showed that the microbial C limitation was mainly attributed to microbial C use efficiency induced by litter quality, suggesting that microorganisms may transfer cellular energy between microbial growth and C-acquiring enzyme production. The microbial P limitation was primarily correlated with AGB-driven change in soil elements and their stoichiometry, highlighting the importance of nutrient stoichiometry and balance in microbial metabolism. The shifts between microbial C and P limitations and the strong connections of plant-soil-microbe processes during vegetation restoration revealed here will provide us with helpful information for optimal management to achieve forest restoration success.

Amplified Drought Alters Leaf Litter Metabolome, Slows Down Litter Decomposition, and Modifies Home Field (Dis)Advantage in Three Mediterranean Forests.

In Mediterranean ecosystems, the projected rainfall reduction of up to 30% may alter plant–soil interactions, particularly litter decomposition and Home Field Advantage (HFA). We set up a litter transplant experiment in the three main forests encountered in the northern part of the Medi-terranean Basin (dominated by either Quercus ilex, Quercus pubescens, or Pinus halepensis) equipped with a rain exclusion device, allowing an increase in drought either throughout the year or concentrated in spring and summer. Senescent leaves and needles were collected under two precipitation treatments (natural and amplified drought plots) at their “home” forest and were left to decompose in the forest of origin and in other forests under both drought conditions. MS-based metabolomic analysis of litter extracts combined with multivariate data analysis enabled us to detect modifications in the composition of litter specialized metabolites, following amplified drought treatment. Amplified drought altered litter quality and metabolomes, directly slowed down litter decomposition, and induced a loss of home field (dis)advantage. No indirect effect mediated by a change in litter quality on decomposition was observed. These results may suggest major alterations of plant–soil interactions in Mediterranean forests under amplified drought conditions.

Warming and grazing enhance litter decomposition and nutrient release independent of litter quality in an alpine meadow

Abstract Warming and grazing, and litter quality jointly determine litter decomposition and nutrient releases in grazing ecosystems. However, their effects have previously been studied in isolation. We conducted a two factorial experiment with asymmetric warming using infrared heaters and moderate grazing in an alpine meadow. Litter samples were collected from all plots in each treatment, among which some subsamples were placed in their original plots and other samples were translocated to other treatment plots to test the relative effects of each treatment on litter decomposition and nutrient releases. We found that warming rather than grazing alone significantly increased total losses of litter mass, total organic carbon, total nitrogen (TN) and total phosphorus (TP) per unit area due to increases in both mass loss rates and litter biomass. However, grazing with warming did not affect their total mass losses because increased mass loss was offset by decreased litter biomass compared with the control. Seasonal mean soil temperature better predicted litter decomposition than litter lignin content or carbon to nitrogen ratio. There were interactions between warming and grazing, but there were no interactions between them and litter quality on litter decomposition. The temperature sensitivity of TN loss was higher than that of TP loss per unit area. Our results suggest that increased temperature has a greater effect on litter decomposition and nutrient release than change in litter quality, and that more N release from litter could result in greater P deficiency in the alpine meadow.

Effects of gamma irradiation on instream leaf litter decomposition

Leaf litter decomposition is a key process in stream ecosystems, the rates of which can vary with changes in litter quality or its colonization by microorganisms. Decomposition in streams is increasingly used to compare ecosystem functioning globally, often requiring the distribution of litter across countries. It is important to understand whether litter sterilization, which is required by some countries, can alter the rates of decomposition and associated processes. We examined whether litter sterilization with gamma irradiation (25 kGy) influenced decomposition rates, litter stoichiometry, and colonization by invertebrates after weeks of instream incubation within coarse-mesh and fine-mesh litterbags. We used nine plant species from three families that varied widely in litter chemistry but found mostly consistent responses, with no differences in decomposition rates or numbers of invertebrates found at the end of the incubation period. However, litter stoichiometry differed between irradiated and control litter, with greater nutrient losses (mostly phosphorus) in the former. Therefore, the effects of irradiation on litter chemistry should be taken into account in studies focused on stoichiometry but not necessarily in those focused on decomposition rates, at least within the experimental timescale considered here.

Ligustrum luciduminvasion decreases abundance and relative contribution of soil fauna to litter decomposition but increases decomposition rate in a subtropical montane forest of northwestern Argentina

Invasive plant species can alter litter decomposition rates through changes in litter quality, environment conditions, and decomposer organisms (microflora and soil fauna), but limited research has examined their direct impact on soil fauna. We assessed the abundance and relative contribution of soil meso- and macrofauna to litter decomposition in a forest invaded by Ligustrum lucidum W.T. Aiton and in a noninvaded forest in a subtropical mountain forest in northwestern Argentina, using litterbags (0.01, 2, and 6 mm mesh size). Additionally, we analyzed the litter quality and soil properties of both forest types. Soil fauna abundance was lower in the invaded forest than in the noninvaded forest. The contribution of soil macrofauna to litter decomposition was important in both forest types, but soil mesofauna contribution was significant only in noninvaded forest. Litter decomposition was significantly faster in the invaded forest, consistent with its higher quality litter compared with the uninvaded forest. Invaded forest had significantly lower litter accumulation, lower soil moisture, and greater soil pH than noninvaded forest. Our results showed that although soil fauna was less abundant and played a less pronounced role in litter decomposition in invaded forest, these changes did not translate into a reduced litter decomposition rate due to the higher quality of litter produced in the invaded forest.

Pedogenic Threshold in Acidity Explains Context-Dependent Tree Species Effects on Soil Carbon

Despite the general agreement that maximizing carbon storage and its persistence in forest soils are top priorities in the context of climate change mitigation, our knowledge on how to steer soil organic carbon (SOC) through forest management remains limited. For some soils, tree species selection based on litter quality has been shown a powerful measure to boost SOC stocks and stability, whereas on other locations similar efforts result in insignificant or even opposite effects. A better understanding of which mechanisms underpin such context-dependency is needed in order to focus and prioritize management efforts for carbon sequestration. Here we discuss the key role of acid buffering mechanisms in belowground ecosystem functioning and how threshold behavior in soil pH mediates tree species effects on carbon cycling. For most forests around the world, the threshold between the exchange buffer and the aluminum buffer around a pH-H2O of 4.5 is of particular relevance. When a shift between these buffer domains occurs, it triggers changes in multiple compartments in the soil, ultimately altering the way carbon is incorporated and transformed. Moreover, the impact of such a shift can be amplified by feedback loops between tree species, soil biota and cation exchange capacity (CEC). Hence, taking into account non-linearities related to acidity will allow more accurate predictions on the size and direction of the effect of litter quality changes on the way soil organic carbon is stored in forest soils. Consequently, this will allow developing more efficient, context-explicit management strategies to optimize SOC stocks and their stability.

Soil burial has a greater effect on litter decomposition rate than nitrogen enrichment in alpine grasslands

AbstractAimsLitter is frequently buried in the soil in alpine grasslands due to grassland degradation, serious rodent infestation and frequent strong winds. However, the effects of various litter positions on litter decomposition rates and nutrient dynamics under nitrogen (N) enrichment in such areas remain unknown.MethodsA field experiment was performed in the alpine grasslands of northwest China to investigate the influence of litter position (surface, buried in the soil and standing) and N enrichment on litter decomposition, using data from two dominant grass species (Festuca ovina and Leymus tianschanicus) in control and N-enriched plots.Important FindingsLitter decomposition rates were much faster in buried litter and slower in standing litter than in surface litter. N enrichment significantly affected litter quality and then influenced decomposition. But no significant differences in litter mass remaining were observed between control and N-enriched soil burial. These results indicated that N enrichment significantly affected litter decomposition by changes in litter quality. In addition, all litter exhibited net carbon (C) and phosphorus (P) release regardless of treatments. Litter exhibited net N accumulation for litter from the control plots but showed N release for litter from N enrichment plots. These suggested that litter decomposition can be limited by N and N enrichment influenced N cycling of litter. Current study presented direct evidence that soil buried litter exhibited faster mass loss and C release, and that soil burial can be a candidate explanation why litter decomposes faster than expected in dryland.

Shrub encroachment affects tundra ecosystem properties through their living canopy rather than increased litter inputs

Deciduous shrub encroachment in tundra ecosystems affects the soil microclimate and, in turn, could affect soil nutrients and microbial processes. Although numerous effects of shrubs on tundra ecosystem properties have been described, there has been little focus on the mechanisms through which they impact tundra functioning. In alpine tundra of northern Canada, we examined 1) the effects of the living shrub canopy and separated them from 2) the effects of increases in litter quantity and quality. In this 4-year study we experimentally manipulated shrub presence (shrub present or removed) and litter quantity (none, natural abundance, and 2x natural abundance) in a fully factorial design. Shrub presence affected soil temperatures by increasing winter and decreased summer soil surface temperatures by about 0.8 °C and 0.6 °C respectively, and also decreased mid-summer soil moisture. Shrub presence also affected both nutrient cycling and microbial processes including decreased summer available nitrogen (N), increased N-immobilization, increased microbial biomass as well as variable effects on potential exoenzyme activity. Increased litter inputs had few significant effects on tundra ecosystems, although additional litter increased both soil C:N ratios and microbial biomass. Our results indicate that shrub encroachment is likely to affect tundra soil properties primarily through mechanisms associated with the presence of the living shrub rather than from the accompanied changing litter quality and quantity. Because of opposing effects of shrubs between seasons and years, we encourage an increased focus on the mechanisms through which shrubs may affect tundra ecosystem functions and year round assessments of these processes.

Deer slow down litter decomposition by reducing litter quality in a temperate forest

Litter decomposition is a key process that allows the recycling of nutrients within ecosystems. In temperate forests, the role of large herbivores in litter decomposition remains a subject of debate. To address this question, we used two litterbag experiments in a quasiexperimental situation resulting from the introduction of Sitka black-tailed deer Odocoileus hemionus sitkensis on forested islands of Haida Gwaii (Canada). We investigated the two main pathways by which deer could modify litter decomposition: change in litter quality and modification of decomposer communities. We found that deer presence significantly reduced litter mass loss after 1 yr, mainly through a reduction in litter quality. This mass loss reflected a 30 and 28% lower loss of carbon (C) and nitrogen (N), respectively. The presence of deer also reduced the ability of decomposers to break down carbon, but not nitrogen. Indeed, litter placed on an island with deer lost 5% less carbon after 1 yr of decomposition than did litter decomposing on an island without deer. This loss in ability to decompose litter in the presence of deer was outweighed by the differences in mass loss associated with the effect of deer on litter quality. Additional effects of feces deposition by deer on the decomposition process were also significant but minor. These results suggest that the effects dramatic continental-scale increases in deer populations may have on broad-scale patterns of C and N cycling deserve closer attention.

Mangrove Encroachment Alters Decomposition Rate in Saltmarsh Through Changes in Litter Quality

Global climate change is driving the expansion of mangroves into saltmarsh habitat, which may alter the rate and magnitude of organic matter decomposition and nutrient cycling due to differences in the structural complexity, litter quality, and other ecophysiological traits of foundation species. This work quantified and compared aboveground litter decomposition of the range-expanding mangrove, Avicennia germinans, and resident saltmarsh cordgrass, Spartina alterniflora, and decomposition of a standard substrate belowground, in the saltmarsh and saltmarsh-mangrove ecotone habitat along the Atlantic coast of Florida, USA. Plant and soil fractions were tested for natural abundances of δ13C and δ15N stable isotopes to elucidate soil nutrient sources. Although aboveground decomposition rates differed between marsh and mangrove species due to differences in litter quality, decomposition rates did not vary between saltmarsh and ecotonal habitats. Decay rates were higher for A. germinans leaf litter (0.007 ± 0.0003 k day−1) than for S. alterniflora (0.004 ± 0.0003 k day−1) regardless of habitat, which suggests that increasing inputs of A. germinans litter with encroachment may increase nutrient availability through rapid turnover. Furthermore, belowground decomposition was similar between habitats (0.015 ± 0.0008 k day−1), whereas soil δ13C and δ15N stable isotopes differed significantly. Collectively, these results suggest that mangrove encroachment may not modify the environmental factors driving decomposition, but alterations in foundation plant species may ultimately alter nutrient cycling within habitats through shifts in litter quality.

Dominance by Spartina densiflora slows salt marsh litter decomposition

AbstractQuestionsCoastal vegetated systems are known to play a fundamental role in climate change mitigation as a result of their efficiency sequestering and storing atmospheric CO2. While most of the work evaluating carbon sequestration capacity has focused on global change factors that can affect carbon release from plant litter decomposition through changes in (large‐scale) environmental conditions, less is known about the possible effects of the loss (or replacement) of dominant species. We hypothesized that dominant marsh plants can influence decomposition not only through changes in litter quality but also through changes in (microscale) soil environmental conditions such as humidity, soil temperature or solar radiation.LocationWe performed a field manipulative experiment in a southwestern (SW) Atlantic salt marsh in Argentina.MethodsWe simulate a selective disturbance (i.e., removal of the dominant grass species Spartina densiflora) thus allowing removal plots to develop an alternative plant community. To evaluate the effect of the dominant grass species on litter decomposition, in an experiment we performed a litterbag approach three years after the establishment of the removal plots.ResultsResults showed that the presence of S. densiflora significantly decreased litter decomposition directly by producing less labile litter, but also by effects that seem to be related to its structure as standing dominant vegetation. The experimental removal of S. densiflora led to an alternative plant community, formed by otherwise subordinate species, which is less densely packed, allowing higher radiation incidence on the soil and elevated midday soil temperature.ConclusionsOur results suggest that salt marsh litter decomposition, and thus C sequestration, is determined in part by the identity of the dominant plant, not only because of the quality of the produced litter but also as a consequence of the vegetation structure . Changes in species diversity, above all changes in the dominant species in these coastal systems, could have large impacts on the carbon turnover and mitigation capacity of these ecosystems.

Nonadditive effects of decomposing mixed foliar litter on the release of several metallic elements in a Pinus massoniana Lamb. forest

The mixture of decomposing litter from three predominant tree species in a Masson pine ( Pinus massoniana Lamb.) forest showed advantages in elemental cycling, and the species component identities were found to be an important driver for the release of several metallic elements. Although mixed forests have long been considered essential to sustainable forestry management, little information is available regarding the effects of the mixed planting of predominant afforestation species on several metallic elements during litter decomposition in the Three Gorges Reservoir region, China. The objectives of this study were to investigate the potential nonadditive effects on element loss from decomposing litter and to estimate the relationship between the mixing effect and the change in litter quality with environmental hydrothermal dynamics. Treatments with one, two, or three species of pine, oak (Quercus variabilis Bl.) and cypress (Cupressus funebris Endl.) based on equal litter mass proportions were used in a field litter bag experiment, and the release of potassium, calcium, magnesium, manganese, iron, copper, zinc, and sodium was measured. Over the 360-day incubation period, most elements decayed faster in oak litter than in the other single-species treatments. A comparison of the litter mixtures revealed that most elements displayed their slowest decay in the pine+cypress combination, whereas the decay values obtained with the cypress+oak or pine+oak combinations were generally greater than those obtained with the pine+cypress+oak combination. Increases in the nonadditive effect on the release of metallic elements, with the exception of calcium, magnesium, and copper, were found in the different phases compared with the incubation time. Changes in elemental traits and environmental hydrothermal dynamics can regulate mixing effects on elemental decay in litter mixtures. The mixing of the studied tree species can alter elemental cycling in plantations, and mixed planting with oak appears to strengthen the cycling process.