Mixed Litter Research Articles

Leaf litter mixtures and neighbour effects: Low-nitrogen and high-lignin species increase decomposition rate of high-nitrogen and low-lignin neighbours

In natural ecosystems plant litter is typically a mixture of more than one species and the rate of decomposition can be faster (synergistic) or slower (antagonistic) than the average of its component species (non-additive effects). We analysed the decomposition rates of two-species mixtures to determine if there were consistent non-additive effects of litter mixing on decomposition and how do they compare with the effects of species identity on mixture decomposition. Then we tested if non-additive effects were consistently associated with the presence of particular species in the mixture, to the combination of Fast- or Slow-decomposing species, or to initial litter quality of mixtures. We found: (a) that species identity was the primary determinant of the decomposition rate of mixtures, and (b) we detected significant, but weak, non-additive effects which were consistently synergistic in the most chemically heterogeneous mixtures. However, slower decomposing species appeared to increase the decomposition rate of faster decomposing species (30 times out of 41 after 2 months of incubation, and 17 times out of 24 after 9 months of incubation). During the initial stages of decomposition, low-lignin mixtures showed mostly synergistic effects, whereas high-lignin mixtures showed antagonistic effects. At more advanced stages of decomposition, mixtures containing species with highest difference in initial N content had more synergistic effects, whereas those with similar initial N content showed both synergistic and antagonistic effects. Our results confirm previous findings about the importance of chemical heterogeneity of mixtures as a driver of decomposition rates of litter mixtures. We propose that mechanisms related to carbon priming may be related to synergistic effects in most heterogeneous mixtures, while nitrogen interaction with carbon may be resulting in antagonistic effects in homogeneous and Slow-decomposing species mixtures.

Influence of environmental parameters on litter decomposition in wetlands in West Virginia, USA

Plant litter decomposition varies by species and environmental conditions. To study environmental controls of decomposition, we measured plant litter decomposition rates in six wetlands located in West Virginia, USA. Four common wetland litter species were used: broadleaf cattail (Typha latifolia L.), common rush (Juncus effusus L.), brookside alder (Alnus serrulata (Ait.) Willd.), and reed canary grass (Phalaris arundinacea L.). A fifth litter type was created from a mix of common rush, brookside alder, and reed canary grass. Litter bags were collected over two years, from December 2007 to December 2009, and environmental variables near litter bags were measured every two weeks. Nine environmental parameters and one study parameter were then used to construct and test the ability of 22 a-priori models to predict the decomposition rate of each litter type. The environmental variables that most influenced and, therefore, best predicted decomposition rate varied among litter types. Brookside alder decomposition rate was best predicted by soil temperature (ST), water pH (WPH), and the number of transitions between flooded and exposed conditions (FET); reed canary grass decomposition rate was best predicted by air temperature (AT), WPH, and ST; common rush decomposition rates were best predicted by AT; broadleaf cattail decomposition rate was best predicted by hydroperiod (HP) and FET; and the mixed litter decomposition rate was best predicted by AT and WPH. Overall, AT, ST, and WPH were directly related to decomposition rate, while HP was inversely related. The FET was directly related to decomposition rates of common rush and broadleaf cattail and inversely related to the decomposition rate of brookside alder. The study of litter decomposition helps reveal the link between environmental conditions and wetland function.

Characterizing soil surface structure in a temperate tree-based intercropping system using X-ray computed tomography

The objective of this work was to characterize differences in the soil surface (top 3.5 cm) microstructure, as influenced by four tree species, within a temperate tree based intercropping (TBI) system. Soils adjacent to walnut (Juglans nigra), poplar (Populus spp.), red oak (Quercus rubra), Norway spruce (Picea abies), as well as three types of ground cover [row crop, willow (Salix spp.), and perennial grass tree rows] were analyzed. X-ray computed micro –tomography (µCT) was employed to evaluate soil void phase characteristics, as well as heterogeneity of soil matrix radiodensity. X-ray µCT identified void phase parameters were not affected by tree species due to confounding effects caused by perennial vegetation and mixed leaf litter inputs.. A positive correlation was found between traditionally measured soil bulk density and bulk X-ray radiodensity (rs = 0.53, p < 0.01) and a negative correlation between mean intra-aggregate X-ray radiodensity and soil organic carbon (rs = −0.48, p = 0.03). It was determined, through the use of geostatistics, that there were no distinct or consistent anisotropic structures, in directional semivariograms, evident for the various species. However, the semivariograms revealed greater variability, correlated with less directional anisotropy within the tree row as compared to cropping alley soils. It was interpreted that processes within soils in the tree rows were leading to a homogenous type of structure, and that soils under row crops exhibited a greater tendency for destruction of surface structure, leading to more directional anisotropy (trends).

Nitrogen transfer in litter mixture enhances decomposition rate, temperature sensitivity, and C quality changes

Litter decomposition is a critical process in terrestrial ecosystems and, since in natural conditions plant litter occurs in mixtures, understanding the interactive effects of mixed litter is of great ecological relevance. In this context, we test the hypothesis that N transfer between high quality litter to N-poor substrates are at the base of synergistic interactions, positively affecting litter decay rate, temperature sensitivity, and changes of organic C quality. We carried out a manipulative experiment using four organic substrates, encompassing a wide range of biochemical quality (Hedera helix and Quercus ilex leaf litter, cellulose strips and woody sticks), each decomposing either separately or in matched pair mixtures for 360 days. Organic substrates were characterized for mass loss, C and N content and by 13C CPMAS NMR to assess biochemical quality changes. Litter response to mixing was related to the biochemical quality of the components in the mixture: additive when substrates with similarly high (H. helix and Q. ilex) or low (cellulose and wood) N content were paired, but synergistic when substrates with contrasting N content were associated (either of the two leaf litters with either cellulose or wood). Overall, no antagonist effects were observed in this experiment. Interestingly, decomposition of cellulose and wood showed an higher temperature sensitivity, compared to monospecific substrates, when paired with N rich materials. Significant N transfer was found from N rich litter to N poor substrates and 13C CPMAS NMR showed rapid changes of C quality of cellulose and wood sticks only when paired with N rich litter. Our findings support the hypothesis that mixing litters of different quality, with quality expressed in terms of C/N ratio and N content, increases decomposition rate and temperature sensitivity of the lower quality substrates.

Non‐additive effects of invasive tree litter shift seasonal N release: a potential invasion feedback

Many invasive plant species strongly alter ecosystem processes by producing leaf litter that decomposes faster and releases N more quickly than that of native species. However, while most studies of invasive species litter impacts have only considered the decomposition of species in monoculture, forest litter layers typically contain litter from many species. Many litter mixtures decompose in a non‐additive manner, in which the mixture decomposes more quickly (synergistic effect) or more slowly (antagonistic effect) than would be expected based on decomposition of the component species’ litters in isolation. We investigated the potential for non‐additive effects of invasive species’ litter by conducting a one‐year litter bag experiment in which we mixed the litters of four native tree species with each of four invasive species. Litter mixtures frequently lost mass at non‐additive rates, although not at every loading ratio, and the presence, sign, and strength of effects depended on species composition. Non‐additive effects on N loss occurred in more litter combinations, and were almost always antagonistic at 90 days and synergistic at 365 days. Invasive species litter with lower C:N led to more strongly synergistic N loss with time. During the growing season, non‐additive patterns of N loss almost always resulted in increased N release – up to six times greater than would be expected based on single‐species decomposition. Consequently, we suggest that invasive species may further synchronize N release from the litter layer with plant N demand, enhancing any positive litter feedback to invasion. These results highlight the need to consider non‐additive effects of litter mixing in invaded forest communities, and suggest that estimates of invasive species’ impacts on ecosystem processes would be improved by considering these effects.

Management strategies to improve the performance of low birth weight pigs to weaning and their long-term consequences1,2

Performance of pigs from birth to slaughter is a result of a complex interaction of factors, with the early stages of a pig's life likely to affect lifetime performance. During the preweaning stage, piglets are reliant on the sow for nutrition, and sibling competition is likely to affect growth, in particular for low birth weight (LBiW) piglets. The objective of the experiment was to determine the effect of litter composition (littermate weight) and milk supplementation during lactation on the performance of LBiW pigs to weaning and the long-term consequences of treatment to slaughter. The experiment was a 2 × 2 factorial with littermate weight (normal or LBiW) and provision of supplementary milk from d 1 to 28 (yes or no) as factors. A total of 265 piglets were selected within 24 h of birth and cross-fostered to create 2 litter types (LOW = LBiW pigs [≤ 1.25 kg] only and MX = both LBiW and normal birth weight pigs [1.6 to 2.0 kg]); half of the litters within a type were supplemented with milk and the other half were not. The behavior of litters given milk was recorded to identify milk consumption patterns. Piglets were weaned at d 28 and kept in their litters until d 70 and then subsequently housed in mixed groups until slaughter. No difference was observed at any stage in the ADG of pigs given access to supplementary milk or not (P > 0.05) nor was there any significant interaction between milk provision and litter composition (P > 0.05). However, LOW litters drank significantly more supplementary milk than MX litters (P < 0.001). There was a significant effect of litter type on ADG from d 14 to 28, with LBiW pigs in LOW litters performing better than those in MX litters (0.252 versus 0.217 kg/d; P < 0.05). At weaning, LBiW piglets in LOW litters weighed over 500 g more than those in MX litters (P < 0.05). In MX litters there was a significant interaction between birth weight and supplementary milk on the CV of BW from d 14 to slaughter (P < 0.05). In conclusion, grouping LBiW piglets with similar sized littermates preweaning can improve preweaning performance by reducing competition from heavier littermates; however, this advantage does not persist after weaning. Although supplementary milk does not improve LBiW pig performance before or after weaning, it affects their drinking behavior and can reduce the variation in the BW of LBiW piglets in mixed litters to slaughter.

Non-Native Plant Litter Enhances Soil Carbon Dioxide Emissions in an Invaded Annual Grassland

Litter decomposition is a fundamental ecosystem process in which breakdown and decay of plant detritus releases carbon and nutrients. Invasive exotic plants may produce litter that differs from native plant litter in quality and quantity. Such differences may impact litter decomposition and soil respiration in ways that depend on whether exotic and native plant litters decompose in mixtures. However, few field experiments have examined how exotic plants affect soil respiration via litter decomposition. Here, we conducted an in situ study of litter decomposition of an annual native grass (Eragrostis pilosa), a perennial exotic forb (Alternanthera philoxeroides), and their mixtures in an annual grassland in China to examine potential invasion effects on soil respiration. Alternanthera litter decomposed faster than Eragrostis litter when each was incubated separately. Mass loss in litter mixes was more rapid than predicted from rates in single species bags (only 35% of predicted mass remained at 8 months) showing synergistic effects. Notably, exotic plant litter decomposition rate was unchanged but native plant litter decomposition rate was accelerated in mixtures (decay constant k = 0.20 month−1) compared to in isolation (k = 0.10 month−1). On average, every litter type increased soil respiration compared to bare soil from which litter was removed. However, the increases were larger for mixed litter (1.82 times) than for Alternanthera litter (1.58 times) or Eragrostis litter (1.30 times). Carbon released as CO2 relative to litter carbon input was also higher for mixed litter (3.34) than for Alternathera litter (2.29) or Eragrostis litter (1.19). Our results indicated that exotic Alternanthera produces rapidly decomposing litter which also accelerates the decomposition of native plant litter in litter mixtures and enhances soil respiration rates. Thus, this exotic invasive plant species will likely accelerate carbon cycling and increase soil respiration even at intermediate stages of invasion in these annual grasslands.

Applicability of Turmeric (Curcuma longa) for Minimizing Ammonia Emission Rates from Poultry Litter by Altering Some Physiochemical Properties

Turmeric(TM) is a natural antiseptic which shows antimicrobial activity against bacteria,fungi, viruses, yeast, and round worms. Objective of the study was to investigate theapplicability of TM to diminish ammonia emission rates from poultry litters by wiping outthe conditions favourable for microbes. Three months old paddy husk based layer litter wasthe subject for the study. A litter sample (2 kg) was taken using a spade and mixed by hand ina sealed black poly bag. From the mixed litter, samples were taken for the determination ofpH and moisture. Litter was mixed with TM powder in 5 different levels; 0%, 1%, 3%, 5%and 8% (w/w). After mixing with TM, 4 replicated samples (150 g each) were placed incontainers for all levels of mixed litter. Then samples were incubated for 5h, and the emittedNH3 was trapped with boric acid and then titrated with HCl to determine the NH3 emissions.The emission rate was calculated as milligrams of NH3 emitted/ /kilogram of fresh litter/hour.The pH was significantly (p &lt; 0.05) reduced with the increment of TM level showing thehighest (9.34) and the lowest (9.07) which is a considerable drop with control (0%) and 8%application level respectively. Moisture (%) was also significantly increased in 1% (44.53%)and 8% (45.18%) applications. There was a trend in reducing ammonia emission with allapplications but not significantly different among treatments. Application of TM (&gt;3%) waseffective in reducing pH (towards acidic) and the NH3 emission of poultry litter. It wasconcluded that by mixing TM powder with poultry litter, there is a possibility to reduceammonia emission by altering favourable conditions for microbes in the litter such as pH andmoisture.

Contrasting decomposition rates and nutrient release patterns in mixed vs singular species litter in agroforestry systems

Purpose The rate of litter decomposition can be affected by a suite of factors, including the diversity of litter type in the environment. The effect of mixing different litter types on decomposition rates is increasingly being studied but is still poorly understood. We investigated the effect of mixing either litter material with high nitrogen (N) and phosphorus (P) concentrations or those with low N and P concentrations on litter decomposition and nutrient release in the context of agroforestry systems.

Non-additive effects of litter-mixing on soil carbon dioxide efflux from poplar-based agroforestry systems in the warm temperate region of China

Poplar-based agroforestry systems are one of the most important farming systems on the temperate plains of China, but soil respiration in those systems has seldom been reported. In this study, poplar leaf litter and residues of the two main crops (wheat and peanut) grown in the agroforestry system were amended to form different litter mixing treatments in field experiments at two sites located in Jiangsu Province, China. We measured soil respiration and environmental factors in the different treatments. Soil respiration rates were increased by the addition of plant residues but were strongly influenced by residue quality. During the growing season, soil respiration was negatively related with C/N ratio, while positively related with the initial P concentration of residues (P < 0.05). Poplar leaf litter and crop residues showed non-additive effects on soil respiration when they were mixed. Both air and soil temperature at 10 cm depth explained more than 85 % of the variation of soil respiration at both sites with an exponential model. A significant linear relationship between soil respiration and soil water content at 10 cm depth (WS) was also observed. The percent of variation in soil respiration explained by a model based on air temperature and soil water content was greater than that explained by a model based on temperature alone. Thus, soil respiration in the studied poplar-based agroforestry systems was driven by both temperature and soil water content. Soil respiration was significantly different between the two sites that had different clay content and C/N ratios. Results from this study are important for us to understand how soil respiration responds to litter mixing or is influenced by biophysical factors in poplar-based agroforestry systems.

Litter decomposition in a temperate and a tropical stream: the effects of species mixing, litter quality and shredders

Summary The current rapid decline in biodiversity has led to concerns about the consequences for stream ecosystem processes, one of which is the decomposition of leaf litter derived from riparian vegetation. We conducted field experiments in a tropical and a temperate stream to test for the effects of mixing leaf species differing in resource quality on the decomposition of leaf litter and on the colonisation of the litter by leaf‐shredding invertebrates. The effects of litter mixing were minor compared with the effects of litter quality and the presence or absence of shredders. Low shredder abundance in the tropical stream and poor quality of the tropical leaf species, particularly in terms of phosphorus content and toughness, were associated with low decomposition rates in the tropical compared with the temperate stream. This is especially true when considering the 20 °C temperature differences between the two streams. In the presence of shredders, the decomposition rate of a standard litter type, leaves of Alnus glutinosa, was 2.6‐fold faster in the temperate stream, whereas rates were similar when shredders were absent. This indicates that differences in environmental conditions other than temperature had a strong effect. Differences in water chemistry, such as higher concentrations of dissolved nutrients in the temperate stream, might account for this effect. In conclusion, despite a lack of clear effects of litter mixing on decomposition, our results highlight the importance of litter identity and environmental conditions for both microbial and shredder‐mediated litter decomposition, suggesting that changes in riparian vegetation and other stream characteristics will affect stream ecosystems in the face of widespread environmental change.

Fungal diversity of saprotrophic litter fungi in a Mediterranean maquis environment

Monospecific and mixed-leaf litters from plant species of Mediterranean maquis (Quercus ilex, Phillyrea angustifolia, Pistacia lentiscus, Cistus spp.) in an undisturbed area in southern Italy were studied with respect to the structure and composition of their decomposer fungal community over an incubation period of 403 d. The data matrix structure was analyzed by means of detrended correspondence analysis (DCA), while indicator species analysis (ISA) was used to determine the preferential association of species with a substrate, a succession phase and monospecific/mixed experimental conditions. The ecological nature of the gradient expressed by the DCA axes was investigated by means of experimental and main chemical leaf-litter variables. The litter mixture had non-additive effects on the decomposition process even though the fungal species richness of the mixed litter was considerably higher than that of the monospecific litter. Our findings highlight the occurrence of shifts in the fungal community during decomposition in response to changes in the substrate, such as those related to the cellulose content and lignin/N ratio.

Production and Quality of Pill-Millipede Manure: A Microcosm Study

This study deals with the production of manure by two pill-millipedes (Arthrosphaera fumosa and A. magna) that harbour in the Western Ghat forests of India, from mixed leaf litter of three plant species (Lagerstroemia microcarpa, Pongamia pinnata and Terminalia paniculata) under laboratory microcosm incubation for 4 weeks. Comparison of feed (applied as mixed leaf litter; ratio, 1:1:1 w/w/w) and manure (faecal pellets) of both millipedes revealed significantly lower total phenolics, organic carbon and C/N ratio (p < 0.05) in the manure. On the other, the contents of total nitrogen and phosphorus were significantly enhanced (p < 0.05). Our studies further indicate the possibility of harvesting the manure, from pill-millipedes fed on mixed leaf litter, with increased contents of nitrogen and phosphorus over a short duration. Performance of both manures showed similar impact with higher biomass of root and shoot, and length of cowpea (Vigna unguiculata) and finger millet (Eleusine coracana). During the third week, cowpea showed root nodulation indicating the presence of plant growth-promoting rhizobia in the manure. Depending on the geographical and environmental conditions, suitable pill-millipedes could be employed for in situ and ex situ manure production for improving agricultural productivity.

Earthworm effects on the incorporation of litter C and N into soil organic matter in a sugar maple forest

To examine the mechanisms of earthworm effects on forest soil C and N, we double-labeled leaf litter with 13C and 15N, applied it to sugar maple forest plots with and without earthworms, and traced isotopes into soil pools. The experimental design included forest plots with different earthworm community composition (dominated by Lumbricus terrestris or L. rubellus). Soil carbon pools were 37% lower in earthworm-invaded plots largely because of the elimination of the forest floor horizons, and mineral soil C:N was lower in earthworm plots despite the mixing of high C:N organic matter into soil by earthworms. Litter disappearance over the first winter-spring was highest in the L. terrestris (T) plots, but during the warm season, rapid loss of litter was observed in both L. rubellus (R) and T plots. After two years, 22.0% +/- 5.4% of 13C released from litter was recovered in soil with no significant differences among plots. Total recovery of added 13C (decaying litter plus soil) was much higher in no-worm (NW) plots (61-68%) than in R and T plots (20-29%) as much of the litter remained in the former whereas it had disappeared in the latter. Much higher percentage recovery of 15N than 13C was observed, with significantly lower values for T than R and NW plots. Higher overwinter earthworm activity in T plots contributed to lower soil N recovery. In earthworm-invaded plots isotope enrichment was highest in macroaggregates and microaggregates whereas in NW plots silt plus clay fractions were most enriched. The net effect of litter mixing and priming of recalcitrant soil organic matter (SOM), stabilization of SOM in soil aggregates, and alteration of the soil microbial community by earthworm activity results in loss of SOM and lowering of the C:N ratio. We suggest that earthworm stoichiometry plays a fundamental role in regulating C and N dynamics of forest SOM.

Non-Additive effects on decomposition from mixing litter of the invasive Mikania micrantha H.B.K. with native plants.

A common hypothesis to explain the effect of litter mixing is based on the difference in litter N content between mixed species. Although many studies have shown that litter of invasive non-native plants typically has higher N content than that of native plants in the communities they invade, there has been surprisingly little study of mixing effects during plant invasions. We address this question in south China where Mikania micrantha H.B.K., a non-native vine, with high litter N content, has invaded many forested ecosystems. We were specifically interested in whether this invader accelerated decomposition and how the strength of the litter mixing effect changes with the degree of invasion and over time during litter decomposition. Using litterbags, we evaluated the effect of mixing litter of M. micrantha with the litter of 7 native resident plants, at 3 ratios: M1 (1∶4, = exotic:native litter), M2 (1∶1) and M3 (4∶1, = exotic:native litter) over three incubation periods. We compared mixed litter with unmixed litter of the native species to identify if a non-additive effect of mixing litter existed. We found that there were positive significant non-additive effects of litter mixing on both mass loss and nutrient release. These effects changed with native species identity, mixture ratio and decay times. Overall the greatest accelerations of mixture decay and N release tended to be in the highest degree of invasion (mix ratio M3) and during the middle and final measured stages of decomposition. Contrary to expectations, the initial difference in litter N did not explain species differences in the effect of mixing but overall it appears that invasion by M. micrantha is accelerating the decomposition of native species litter. This effect on a fundamental ecosystem process could contribute to higher rates of nutrient turnover in invaded ecosystems.

Cross‐ecosystem differences in lipid composition and growth limitation of a benthic generalist consumer

In a field study, we analyzed the fatty acid (FA) composition of the benthic generalist Asellus aquaticus collected from boreal lakes, ponds, and streams across gradients in ambient nutrient levels. In laboratory feeding experiments, we tested the diet‐quality and seasonal effects on somatic growth and FAs of spring‐ and autumn‐collected Asellus that were fed four different diets containing increasing concentrations of polyunsaturated FAs (PUFA): conditioned leaf litter, algal flakes, mixed litter and algal flakes (Mixed), or Mixed plus fish‐food flakes. Ambient nutrients were strong determinants of FA variation of field Asellus, explaining &gt; 44% in total. The ratios of eicosapentaenoic acid (EPA) to total FAs, EPA : ω3, and ω3 : ω6 of Asellus increased up to four times with increasing trophic state and decreasing humic matter content, likely because dietary ω3 FAs were more prevalent in benthic habitats of eutrophic than of oligotrophic systems. In the feeding trials, growth of Asellus collected in both seasons was markedly lower on leaf litter than on higher PUFA diets. However, autumn‐collected Asellus fed a Mixed or Mixed+fish‐food diet grew 3–10 times faster, but retained &lt; 50% EPA and PUFA than spring counterparts. Asellus optimized PUFA accumulation in spring but somatic growth in autumn. Our field survey suggests ambient nutrient concentrations modify dietary PUFA supply from basal resources, while laboratory studies show that growth response and PUFA accumulation of Asellus differ between seasons, likely due to its season‐specific physiological status and diet quality. An increase in nutrients will release benthic consumers from growth limitation and favor more efficient trophic transfer.

Litter mixing significantly affects decomposition in the Hulun Buir meadow steppe of Inner Mongolia, China†

Aims We explored the decomposition rates of single- and mixed-species litter, the litter-mixing effect and the effect of component litters in a mixture on decomposition. Methods In a litter bag experiment, shoot litters from two dominant grasses (Leymus chinensis and Stipa baicalensis) and one legume (Melissitus ruthenica) were decomposed separately and as a mixture from May 2010 to September 2011 in the Hulun Buir meadow steppe of Inner Mongolia, China. We separated the litter mixture into its individual component litters (i.e. the different single-species litters) and analyzed the changes in litter mass remaining and litter nitrogen (N) remaining during single-and mixed-species litter decomposition. Important Findings (i) Litter mixing had significant positive effects on litter decomposition. The litter-mixing effect was strongest for the mixture of S. baicalensis and L. chinensis litters, followed by the mixture of S. baicalensis and M. ruthenica litters. (ii) Single-species component litters decomposed faster in the mixtures than separately (positive effect), but these effects were not significant for legume species M. ruthenica litter. Relative to single-species litter decomposition, the decomposition rates of the two grass (S. baicalensis and L. chinensis) litters significantly increased when they were mixed with each other or with M. ruthenica litter. (iii) For each species litter type, the percentage of litter N remaining during decomposition (NR) differed between the single-species litter and mixed litter treatments. The NR of S. baicalensis litter was higher when it was decomposed in the mixture than in isolation. However, the NR of L. chinensis litter was lowest in its mixture with M. ruthenica among the treatments. Regardless of its decomposition in the mixture or in isolation, the NR of M. ruthenica litter varied little among treatments. There was a significant positive relationship between the NR and percentage of initial litter mass remaining in both the single litter and mixed litter treatments. These results suggest that N transfer may happen among component litters in mixture and further affect the decomposition.

Leaf Litter Mixtures Alter Microbial Community Development: Mechanisms for Non-Additive Effects in Litter Decomposition

To what extent microbial community composition can explain variability in ecosystem processes remains an open question in ecology. Microbial decomposer communities can change during litter decomposition due to biotic interactions and shifting substrate availability. Though relative abundance of decomposers may change due to mixing leaf litter, linking these shifts to the non-additive patterns often recorded in mixed species litter decomposition rates has been elusive, and links community composition to ecosystem function. We extracted phospholipid fatty acids (PLFAs) from single species and mixed species leaf litterbags after 10 and 27 months of decomposition in a mixed conifer forest. Total PLFA concentrations were 70% higher on litter mixtures than single litter types after 10 months, but were only 20% higher after 27 months. Similarly, fungal-to-bacterial ratios differed between mixed and single litter types after 10 months of decomposition, but equalized over time. Microbial community composition, as indicated by principal components analyses, differed due to both litter mixing and stage of litter decomposition. PLFA biomarkers a15∶0 and cy17∶0, which indicate gram-positive and gram-negative bacteria respectively, in particular drove these shifts. Total PLFA correlated significantly with single litter mass loss early in decomposition but not at later stages. We conclude that litter mixing alters microbial community development, which can contribute to synergisms in litter decomposition. These findings advance our understanding of how changing forest biodiversity can alter microbial communities and the ecosystem processes they mediate.

Time and litter species composition affect litter-mixing effects on decomposition rates

Purpose Litter decomposition is a fundamental process of biogeochemical cycles. Mixing litter of different species can induce non-additive effect (NAE) on decomposition processes. A better understanding of the factors influencing the direction and magnitude of NAE is important for quantification of ecosystem carbon and nutrient cycling. Methods Litter mixing effects on leaf litter decomposition were examined using two parallel experiments (each with leaf litter of four tree species combined into four diversity levels) conducted in Chinese temperate forests for 2 years. Results A significant diversity effect in both experiments demonstrated NAEs of litter mixing on the mass remaining. Separating the diversity effect into species richness and composition showed that composition was statistically significant in both experiments whereas an effect of species richness was only detected in Experiment 2. In both experiments, the NAE on decomposition changed with incubation time and showed a declining trend during decomposition process. However, a slight difference of the NAE in the two experiments was observed in our study. Decomposition in the litter mixtures differed from the predictions based on single species, and the presence/absence of poplar, pine and oak in the litter mixture significantly influenced the direction and magnitude of the NAE. Presence of coniferous species litter significantly reduced decomposition rates even within the same species richness level. The coefficient of variation of remaining litter mass was lower in the treatments with higher number of litter species. Conclusions Our findings showing of changes in the direction and magnitude of NAE with decomposition time and litter species composition indicate that tree species composition and decomposition duration should be considered in predicting biodiversity effect on biogeochemical cycling in temperate forests.

Effect of litter substrate quality and soil nutrients on forest litter decomposition: A review

Forest litter plays an important role in determining nutrient cycling, balance and maintaining ecosystem function of forest ecosystems. Studies have shown that litter substrate quality is one of the most important factors affecting litter decomposition in a given area. It is, hence, important to understand the factors controlling litter decomposition in the late decomposition stage and determining organic matter changes over the duration of litter decomposition. Decomposition rate of mixed litter may differ with that of a single specie litter. Supply of soil nutrients is an important factor controlling litter decomposition rate, because the essential nutrients in soil or litter material influence community and activity of decomposers (soil organisms). There were clear relationships among soil nutrient, litter substrate quality, and decomposition. Soil nutrient contents were positively correlated with litter substrate quality, showing that higher contents of soil nutrient were accompanied with good quality of litter substrate, and lower soil nutrients with poor litter quality. The effects of soil fertility on litter decomposition rate varied with environmental conditions. It was reported that litter quality regulates the early stage of carbon decomposition and its accumulation in soil, however, it could not predict the long-term dynamics of soil organic carbon. Hence, the formation and stabilization of soil organic carbon are controlled by the quantity of litter input and its interaction with the soil circumstances rather than by the litter quality. The present paper reviewed the research findings about litter decomposition related to litter substrate quality and soil nutrients, including short-term and long-term litter decomposition, decomposition of single-species vs. mixed-litter decomposition and litter nutrients release. The present paper aimed to clarify the relationship between soil nutrients and litter decomposition, which will help to understand forest succession, forest water conservation and soil re-production capacity.