Mixed Litter Research Articles

Aboveground macrodetritivores and belowground soil processes: Insights on species redundancy

Quantifying the level of overlap between species-specific effects in a given process – i.e. their functional redundancy–remains a central issue in predicting the shape of diversity-productivity or diversity-stability relationships. We compared the indirect effects of six aboveground macro-detritivores on two belowground processes, cellulose decay and nutrient mineralization, in single-species microcosms (n=5) containing standardized substratum, mixed litter, and four individuals of detritivores. In all microcosms, there was an overall increase in phosphate and decrease in nitrate and ammonium over four weeks. Cellulose decay was ≈30%. Compared to fauna-free controls, there were a few noticeable fauna effects: decay was higher in microcosms with Armadillidium vulgare and Porcellio scaber, nitrate immobilization was lower in Cylindroiulus caeruleocinctus microcosms, and ammonium immobilization was lower in A. vulgare and P. scaber microcosms. The multivariate effects were idiosyncratic and related to a high intraspecific variation. Contrary to our expectations, the most noticeable difference was between P. scaber and Trachelipus rathkii. Our results point to redundancy due to high intraspecific variation. It is postulated that, if redundancy arises from high intraspecific variation, upon the loss of species, large population sizes of remaining species from the same functional group might explain positive effects of redundancy on ecosystem resilience.

What is good for small piglets might not be good for big piglets: The consequences of cross-fostering and creep feed provision on performance to slaughter.

Major improvements in sow prolificacy have resulted in larger litters but, at the same time, increased the proportion of piglets born light weight. Different management strategies aim to enhance the performance of, and limit light-weight piglet contribution to, BW variation within a batch; however, consequences on heavy-weight littermates are often neglected. This study investigated the effects of different litter compositions, created through cross-fostering, and the provision of creep feed on preweaning behavior and short- and long-term performance of piglets born either light weight (≤1.25 kg) or heavy weight (1.50-2.00 kg). Piglets were cross-fostered at birth to create litters with only similar-sized piglets (light weight or heavy weight; UNIFORM litters) and litters with equal numbers of light-weight and heavy-weight piglets (MIXED litters); half of the litters were offered creep feed and the remaining were not. Piglet behavior during a suckling bout and at the creep feeder was assessed; a green dye was used to discern between consumers and nonconsumers of creep feed. The interaction between litter composition and birth weight (BiW) class influenced piglet BW at weaning ( < 0.001): piglets born light weight were lighter at weaning in MIXED litters than those in UNIFORM litters (6.93 vs. 7.37 kg); however, piglets born heavy weight performed considerably better in MIXED litters (8.93 vs. 7.96 kg). Total litter gain to weaning was not affected ( = 0.565) by litter composition. Teat position affected heavy-weight piglet performance by d 10 ( < 0.001), with heavy-weight piglets in UNIFORM litters being disadvantaged when suckling the middle and posterior teats. Creep feed provision did not affect BW at weaning ( > 0.05) for either BiW class. However, litter composition significantly affected daily creep feed consumption ( = 0.046) and fecal color ( = 0.022), with heavy-weight piglets in UNIFORM litters consuming the highest amount of creep feed and having the greenest feces. In addition, a lower number of heavy-weight piglets in UNIFORM litters were classified as nonconsumers ( = 0.002). The weight advantage heavy-weight and light-weight piglets had at weaning when reared in MIXED and UNIFORM litters, respectively, was sustained throughout the productive period. In conclusion, reducing BW variation within litter (UNIFORM litters) was beneficial for piglets born light weight but not for piglets born heavy weight; the latter were disadvantaged up to slaughter. Although heavy-weight piglets in UNIFORM litters consumed the greatest amount of creep feed, this was not able to overcome their growth disadvantage compared with heavy-weight piglets in MIXED litters.

Relationship between leaf litter decomposition and colonization of benthic macroinvertebrates during early frost period in a headwater stream in the Changbai Mountains, Northeast China

Annually, about 70% of the streams in the Changbai Mountains are frosted during November to April, with manifest seasonal freeze-thaw characters. By using monoculture and mixing leaf litters of Tilia amurensis, Acer mono and Quecus mongolica, this research attempted to disentangle the relationship between leaf litter decomposition and colonization of macroinvertebrates in the stream during early frost period. A 35-day investigation was carried out in a headwater stream of the Changbai Mountains. Nylon bags with two hole sizes (5 mm and 0.3 mm) were used to examine decomposition of the litters. The results showed that the mass losses were significantly different among the three kinds of leaf litters in monoculture, whose decomposition rates descended as A. mono, T. amurensis, and Q. mongolica, however, there existed no significant difference among the litter mixing. Mass losses in both mesh bags all showed little difference, except T. amurensis and the mixed litters. Litter mixing effects occurred in the coarse mesh bags with A. mono and Q. mongolica, but no mixture effects for others. Community structures of the macroinvertebrates colonizing in the litter bags differed with each other, but shredders' density had no significant difference among the three litters, and the mixing effects on shredders were poor. Our results implied that microbes play the major decomposers of leaf litters, and macroinvertebrates contribute little to the decomposition in the early frost period. Despite shredder's density is lower, they determine the mixing effects of litters. Macroinvertebrates are selective to food and habitats, however, due to the short term colonizing, and the influence of leaf litters on shredders is still unsure. Our results might contribute to understanding the cold season ecological processes and related management issues of headwater stream ecosystem.

Litter decomposition in peatlands is promoted by mixed plants

Purpose: The carbon sink function of peatlands is primarily driven by a higher production than decomposition of the litter Sphagnum mosses. The observed increase of vascular plants in peatlands could alter the decomposition rate and the carbon (C) cycle through a litter mixing effect, which is still poorly studied. Here, we examine the litter mixing effect of a peat moss (Sphagnum fallax) and two vascular plants (Pinus uncinata and Eriophorum vaginatum) in the field and laboratory-based experiment. Materials and methods: During the laboratory incubation, mass loss, CO2 production, and dissolved organic carbon concentration were periodically monitored during 51 days. The collected data were then processed in a C dynamics model. The calculated enzymatic activity was correlated to the measured β-glucosidase activity in the litter. In the field experiment, mass loss and CO2 production from litter bags were annually measured for 3 years. Results and discussion: Both laboratory and field experiments clearly show that the litter mixture, i.e., Sphagnum-Pinus-Eriophorum, had a synergistic effect on decomposition by enhancing the mass loss. Such enhanced mass loss increased the water extractable C and CO2 production in the litter mixture during the laboratory experiment. The synergistic effect was mainly controlled by the Sphagnum-Eriophorum mixture that significantly enhanced both mass loss and CO2 production. Although the β-glucosidase activity is often considered as a major driver of decomposition, mixing the litters did not cause any increase of the activity of this exo-enzyme in the laboratory experiment suggesting that other enzymes can play an important role in the observed effect. Conclusions: Mixing litters of graminoid and Sphagnum species led to a synergistic effect on litter decomposition. In a context of vegetation dynamics in response to environmental change, such a mixing effect could alter the C dynamics at a larger scale. Identifying the key mechanisms responsible for the synergistic effect on litter decomposition, with a specific focus on the enzymatic activities, is crucial to better predict the capacity of peatlands to act as C sinks.

Pure and mixed litters of Sphagnum and Carex exhibit a home-field advantage in Boreal peatlands

The notion that plants are tightly coupled to their belowground environment so that decomposition occurs faster in their place of origin is now a widely tested hypothesis known as the home-field advantage (HFA). Microbial adaptation to the most prevalent plant litter is the hypothesis proposed to explain decomposition results in a number of HFA studies but fails to corroborate results of many others, highlighting the need for a more comprehensive understanding of decomposition dynamics at local scales. Boreal peatlands are important ecosystems for carbon storage that are expected to be significantly affected by climate change, thus understanding decomposition dynamics in Boreal peatland systems is of global relevance. We performed a reciprocal transplant experiment using pure and mixed litters of two dominant peatland plant types (Sphagnum moss and Carex sedge) present in differing densities at two sites differing in nutrient status in a Boreal peatland complex. Aboveground (temperature, relative humidity) and belowground (pH, moisture, available nitrogen) environmental characteristics were measured, and initial litter quality (C, N, S) was assessed with decomposition (mass loss) quantified after one year. We use linked HFA equations that help account for differences in litter quality and site conditions. While Carex lost greater overall mass than Sphagnum, both Carex and Sphagnum demonstrate a HFA, but only where they were the dominant plant of each site. This result held for both pure and mixed litters, suggesting microbial specificity to the most prevalent plant type, yet mixed litters moderated the strength of the HFA. While our results provide novel insights to plant-soil linkages and mixed litter interactions in Boreal peatlands, mechanisms underpinning microbial specificity to plant litter in these ecosystems requires further investigation.

Observations of Intraspecific Interactions of Bobcats (Lynx rufus) in the Southern High Plains of Texas

Bobcats (Lynx rufus) are solitary felines, having minimal interaction between individuals except for mating or rearing of kittens by females. We report observations of nonaggressive interactions observed and photographed among bobcats in an impacted landscape of the Southern High Plains of Texas. These included the temporary mixing of bobcat litters with at least one adult female present, interactions involving related females and a juvenile, a male bobcat in the presence of a nursing female and her kittens, and several adult bobcats accompanied by a juvenile.

Determining the absorption coefficients of decay pigments in decomposing monocots

Decomposition is an important biosphere process that recycles sequestered nutrients, plays a key role in carbon emissions, and accumulates compounds that exert negative feedbacks on primary production. In certain environments, litter comprises a considerable portion of the canopy, impeding the quantification of living biomass. Decomposition incurs physical changes and the genesis of decay pigments over time, causing the optical properties of litter to evolve in tandem. In order to simulate the spectral evolution of decaying leaves and relate the spectra to meaningful quantities of the biochemical compounds present, knowledge of the in-situ absorption properties of decay pigments is required. To determine the specific absorption coefficients of decay pigments in monocot leaf litter, we developed a spectral data set of multiple species at various decay stages concurrent with quantities of foliar compounds from fiber and humic acid analysis. Utilizing leaf humic acid content, the specific absorption coefficients for initial and advanced decay pigments were estimated using the PROSPECT model. For a 70-sample evaluation data set, simulated litter spectra closely matched the Reflectance, Transmittance, and Absorptance of measured leaves, with an average %RMSE (400–2500nm range) of 4.95. Inversion of the expanded PROSPECT model had a moderate relationship between measured gravimetric humic acid content and the model inverted sum of initial and advanced decay pigments, as indicated by the R2=0.62 and index of agreement=0.72 goodness of fit statistics. Integrating the specific absorption coefficients of decay pigments into the PROSAIL model permitted the canopy reflectance of grassland scenes of intertwined photosynthetic leaves and litter to be simulated. Model inversion results aligned well with changes in canopy chlorophyll and biomass, cumulating in an R2=0.69 between measured and predicted leaf area index. Sensitivity analysis further revealed that canopy level reflectance in the near infrared region for mixed green vegetation and litter scenes are driven mainly by advanced decay pigments. Hence, the inclusion of decay pigments' specific absorption coefficients are of high importance for accurate simulation of mixed vegetation scenes. Further, the derived specific absorption coefficients can be utilized to quantify humic acid content in monocotyledon leaves as a proxy for decay stage and the carbon quality of litter.

Relationship between litter produced by Calamagrostis epigejos and seedling recruitment of mesic meadow species in mountain conditions

Calamagrostis epigejos produces a large amount of litter in patches dominated by this expansive species in degraded meadows. Two studies were carried out in the area of the Central Sudetes Mountains (SW Poland). The goals of these surveys were to address the following questions: How do active manipulations regarding the removal of necromass and C. epigejos tillers, as well as seeding of additional species, influence the meadow species seedling recruitment? How is the organic matter decomposed in the consecutive stages of mountain grassland degradation caused by C. epigejos expansion? How do environmental factors influence litter decomposition? The results of the research showed a significant influence of C. epigejos necromass on the recruitment of mesic meadow species. The influence is connected with the emergence of a mechanical barrier to seedlings, which impedes their sprouting. No relation was found between the degradation stage and the rate of necromass decomposition. The study showed the influence of some environmental factors on the rate of necromass decomposition – in the case of C. epigejos there was a negative impact of exchangeable magnesium forms, whereas in the case of mixed meadow plant litter there was a positive effect of nitrogen and C:N ratio, and negative correlations with Ellenberg’s light and soil humidity indices.

Species diversity and chemical properties of litter influence non-additive effects of litter mixtures on soil carbon and nitrogen cycling.

Decomposition of litter mixtures generally cannot be predicted from the component species incubated in isolation. Therefore, such non-additive effects of litter mixing on soil C and N dynamics remain poorly understood in terrestrial ecosystems. In this study, litters of Mongolian pine and three dominant understory species and soil were collected from a Mongolian pine plantation in Northeast China. In order to examine the effects of mixed-species litter on soil microbial biomass N, soil net N mineralization and soil respiration, four single litter species and their mixtures consisting of all possible 2-, 3- and 4-species combinations were added to soils, respectively. In most instances, species mixing produced synergistic non-additive effects on soil microbial biomass N and soil respiration, but antagonistic non-additive effects on net N mineralization. Species composition rather than species richness explained the non-additive effects of species mixing on soil microbial biomass N and net N mineralization, due to the interspecific differences in litter chemical composition. Both litter species composition and richness explained non-additive soil respiration responses to mixed-species litter, while litter chemical diversity and chemical composition did not. Our study indicated that litter mixtures promoted soil microbial biomass N and soil respiration, and inhibited net N mineralization. Soil N related processes rather than soil respiration were partly explained by litter chemical composition and chemical diversity, highlighting the importance of functional diversity of litter on soil N cycling.

The effect of mixing piglets after weaning on the occurrence of tail-biting during rearing

The aim of this study was to investigate the effects on tail-biting during rearing of housing piglets of the same litter compared to piglets from different litters. The treatments “litter-wise” (LW, n =240) and “mixed litters” (ML, n =238) were housed in five identical units. Each tail was scored regarding tail lesions and tail losses once per week with a four-point score (0= no damage/original length to 3= severe damage/total loss). The effect of week after weaning had highly significant influences on tail lesions (p<0.001). Tail-biting started in the second week after weaning, with an increasing severity during rearing. First tail losses were observed in the fourth week after weaning. The batch and the interaction between treatment and batch had highly significant influences on tail losses at the end of rearing (p<0.001). Depending on batch, piglets in the LW or ML treatment were more affected by tail-biting.

Fire enhances litter decomposition and reduces vegetation cover influences on decomposition in a dry woodland

Dry woodlands frequently experience fire, and the heterogeneous spatial patterning of vegetation cover and fire behavior in these systems can lead to interspersed burned and unburned patches of different vegetation cover types. Biogeochemical processes may differ due to fire and vegetation cover influences on biotic and abiotic conditions, but these persistent influences of fire in the months or years following fire are not as well understood as the immediate impacts of fire. In particular, leaf litter decomposition, a process controlling nutrient availability and soil organic matter accumulation, is poorly understood in drylands but may be sensitive to vegetation cover and fire history. Decomposition is responsive to changes in abiotic drivers or interactions between abiotic conditions and biotic drivers, suggesting that decomposition rates may differ with vegetation cover and fire. The objective of this study was to assess the role of vegetation cover and fire on leaf litter decomposition in a semi-arid pinyon-juniper woodland in southern New Mexico, USA, where prescribed fire is used to combat increasing woody cover. A spatially heterogeneous prescribed burn led to closely co-located but discrete burned and unburned patches of all three dominant vegetation cover types (grass, shrub, tree). Decomposition rates of leaf litter from two species were measured in mesh litterbags deployed in factorial combination of the three vegetation cover types and two fire treatments (burned and unburned patches). For both litter types, decomposition was lower for unburned trees than for unburned grass or shrubs, perhaps due to greater soil–litter mixing and solar radiation away from tree canopies. Fire enhanced litter mass loss under trees, making decomposition rates similarly rapid in burned patches of all three vegetation cover types. Understanding decomposition dynamics in spatially heterogeneous vegetation cover of dry woodlands is critical for understanding biogeochemical process responses to fire in these systems.

Home‐field advantages of litter decomposition increase with increasing N deposition rates: a litter and soil perspective

SummaryDifferences in litter quality and in soil microbial community composition can influence the litter decomposition and ‘home‐field advantage’ (HFA). However, our knowledge about the relative role of litter and soil characteristics on litter decomposition andHFAeffects is still limited, especially under long‐term N deposition.We collected soil and two types of litter (monospecific and mixed species litter) from five replicate plots from a long‐term N deposition field experiment with seven N addition treatments (0, 2, 5, 10, 15, 20, 50 g N m−2 year−1). We examined the effects of N addition on litter quality and soil characteristics. We then carried out a three‐pronged microcosm decomposition experiment with (i) litter from different N addition treatments decomposed on a standard field soil; (ii) standard litter decomposed on soils from the different N addition treatments; and (iii) litter decomposed on soil from the same N addition treatment plot.Decomposition of litter on standard soil was influenced strongly by the N addition treatment, but did not consistently decrease or increase with increasing N addition rates. Instead, decomposition of standard litter on soils collected from different N addition treatments decreased with increasing rates of N addition. Decomposition of litter on soil collected from the same plot increased with increasing N addition rates. Soil characteristics explained more of the variation in litter decomposition than litter characteristics.There was a clearHFAeffect for litter decomposition, both from a litter and from a soil perspective.HFAeffects increased when the dissimilarity in litter quality (N content and C : N ratio) increase among the different N addition treatments and the soil effect was strongest at high N addition rates.N addition influenced litter decomposition by changing both litter and soil characteristics. Importantly, N addition decreased the capability of soils to decompose litter and it increased the HFA effect indicating that soils decomposed local litter better than other litter, due to specialization in soil communities. Nitrogen deposition is an important threat to ecosystems worldwide and our study emphasizes that ecosystem functions such as decomposition can be greatly influenced by these global changes.Alay summaryis available for this article.

Contrasting mass‐ratio vs. niche complementarity effects on litter C and N loss during decomposition along a regional climatic gradient

Summary The mass‐ratio and niche complementarity mechanisms drive the influence of litter trait diversity on decomposition. However, the implications of these mechanisms remain poorly understood, as few studies have evaluated their importance relative to environmental conditions and soil decomposers when assessing different processes during decomposition (e.g. C dynamics and N transformations). We measured litter C and N losses during decomposition in 10 litter mixtures and calculated community‐weighted means (CWM) and dissimilarity (Rao's Q) of 13 litter traits as metrics of the mass‐ratio and niche complementarity mechanisms respectively. The 10 litter mixtures were incubated along a regional gradient (10 sites) in southern France over a year, where local environmental conditions (climate and soil parameters), and soil decomposers (microbes, nematodes, and macrofauna) were considered as drivers of decomposition. Sites and litter mixtures represented a wide range of environmental conditions, decomposers, and litter diversity. Litter mixture was the major factor affecting litter C and N loss. N was immobilized during the early decomposition stages (up to c. 40% mass loss), especially in mixtures of low N concentrations. Litter CWM traits were the key drivers of litter C and N loss, but litter trait dissimilarity emerged as a major driver of litter N loss. Macrofauna played a significant role on C and N loss, but environmental conditions exerted a minor influence. Our results highlight that distinct aspects of trait diversity in mixed species litter can play a more important role than environmental conditions and decomposers, which can affect the cycling of litter C and N at regional scales. Rather than opposing mass‐ratio and niche complementarity mechanisms, our study shows that both can play a critical role simultaneously in litter decomposition. Synthesis. Our study emphasizes that, in the current context of global biodiversity decline, the mass‐ratio and niche complementarity mechanisms should be considered to assess litter decomposition dynamics under global change. As litter diversity mechanisms distinctly affected the cycling of C and N, we recommend taking into account such element‐specific effects to improve the prediction of the impacts of biodiversity change on biogeochemical cycles.

Soil–litter mixing and microbial activity mediate decomposition and soil aggregate formation in a sandy shrub-invaded Chihuahuan Desert grassland

Drylands account globally for 30% of terrestrial net primary production and 20% of soil organic carbon. Present ecosystem models under predict litter decay in drylands, limiting assessments of biogeochemical cycling at multiple scales. Overlooked decomposition drivers, such as soil–litter mixing (SLM), may account for part of this model-measurement disconnect. We documented SLM and decomposition in relation to the formation of soil-microbial films and microbial extracellular enzyme activity (EEA) in the North American Chihuahuan Desert by placing mesh bags containing shrub (Prosopis glandulosa) foliar litter on the soil surface within contrasting vegetation microsites. Mass loss (in terms of k, the decay constant) was best described by the degree of SLM and soil-microbial film cover. EEA was greatest during periods of rapid litter decomposition and associated SLM. Soil-microbial film cover on litter surfaces increased over time and was greater in bare ground microsites (50% litter surface area covered) compared to shrub and grass microsites (37 and 33% covered, respectively). Soil aggregates that formed in association with decomposing leaf material had organic C and N concentrations 1.5–2× that of local surface soils. Micrographs of soil aggregates revealed a strong biotic component in their structure, suggesting that microbial decomposition facilitates aggregate formation and their C and N content. Decomposition drivers in arid lands fall into two major categories, abiotic and biotic, and it is challenging to ascertain their relative importance. The temporal synchrony between surface litter mass loss, EEA, biotic film development, and aggregate formation observed in this study supports the hypothesis that SLM enhances decomposition on detached litter by promoting conditions favorable for microbial processes. Inclusion of interactions between SLM and biological drivers will improve the ability of ecosystem models to predict decomposition rates and dynamics in drylands.

Plant litter mixture partly mitigates the negative effects of extended drought on soil biota and litter decomposition in a Mediterranean oak forest

SummaryA major challenge of current ecological research is to determine the responses of plant and animal communities and ecosystem processes to future environmental conditions. Ecosystems respond to climate change in complex ways, and the outcome may significantly depend on biodiversity.We studied the relative effects of enhanced drought and of plant species mixture on soil biota and on litter decomposition in a Mediterranean oak forest. We experimentally reduced precipitation, accounting for seasonal precipitation variability, and created a single‐species litter (Quercus pubescens), a two‐species litter mixture (Q. pubescens+Acer monspessulanum) and a three‐species litter mixture (Q. pubescens+A. monspessulanum+Cotinus coggygria).In general, drier conditions affected decomposers negatively, directly by reducing fungal biomass and detritivorous mesofauna, and also indirectly by increasing the predation pressure on detritivorous mesofauna by predatory mesofauna. This is reflected under drier conditions in that Collembola abundance decreased more strongly than Acari abundance. One Collembola group (i.e. Neelipleona) even disappeared completely.Increased drought strongly decreased litter decomposition rates. Mixed litter with two and three plant species positively affected soil biota communities and led to a more efficient litter decomposition process, probably through a greater litter quality. Faster decomposition in mixed litter can thus compensate slower decomposition rates under drier condition.Synthesis. Our results highlight that, within our study system, drier climate strongly impacts on soil biodiversity and hence litter decomposition. Species‐rich litter may mitigate such a decline in decomposition rates. Diverse plant communities should hence be maintained to reduce shifts in ecosystem functioning under climate change.

Effects of Litter Evenness, Nitrogen Enrichment and Temperature on Short-Term Litter Decomposition in Freshwater Marshes of Northeast China

Knowledge about the effects of global change factors on litter decomposition is critical for accurate prediction of future carbon (C) and nutrient cycles in terrestrial ecosystems. Here, we collected Deyeuxia angustifolia and Carex lasiocarpa litters from freshwater marshes in Northeast China, and conducted an incubation study to examine the effects of nitrogen (N) enrichment (0 and 25 mg N g−1 litter), temperature (5, 15, and 25 °C), and litter evenness on litter mixing effect and decomposition. Non-additive effects were more common than additive effects during decomposition of litter mixtures, and synergistic effect was detected in two thirds of the litter mixtures. Moreover, litter mixing effects on decomposition varied with N enrichment, incubation temperature, and litter evenness. Both increased proportions of D. angustifolia in litter assemblages and elevated temperature generally accelerated litter decomposition. However, N enrichment slowed litter decomposition at 5 and 15 °C, but had positive or neutral effect at 25 °C. Our results highlight the importance of the interactive effects of N enrichment, temperature, and plant community structure on litter mixing effects during decomposition, and suggest that accelerated litter decomposition induced by climate warming and altered vegetation community would be modulated by N enrichment in freshwater marshes of Northeast China.

Mixing of Aleppo pine and Holm oak litter increases biochemical diversity and alleviates N limitations of microbial activity

Soil N availability is a primary limitation for plants and microbes in Mediterranean ecosystems. Few studies have examined the role of secondary compounds (e.g. polyphenols and volatile organic compounds) in mixed litter in Mediterranean ecosystems. Here, we ask whether the natural mixing of Aleppo pine and Holm oak litter decreases the inhibitory effect of secondary compounds and increases microbial activities involved in C cycling. In situ N fertilisation was used to demonstrate the limiting role of N to soil microbial activities, particularly in pure pine stands, and we hypothesised that these inhibitory effects would be alleviated in mixed litter. We examined the concentrations, structure and diversity of biochemical compounds in litter from single-species or mixed stands of pine and oak, along with associated microbial activities (i.e. net ammonification and nitrification, cellulase, fluorescein diacetate hydrolase (FDAse) and phenol oxidase activities). We tested the relationships between biochemical compounds and microbial activities with co-inertia analyses. Pine litter clearly shaped the biochemical composition of mixed litter in the organic litter horizon, and this mixed litter was dominated by high molecular weight compounds (total phenols, sesqui- and diterpenes). In contrast, oak litter was dominated by small compounds such as monoterpenes and hydro-soluble phenols. Pine litter clearly affected microbial activities (i.e. antagonistic effect) in unfertilised mixed litter. We demonstrated by co-inertia analysis that this antagonistic effect was related to N availability. Mixed litter had the highest VOC (volatile organic compounds) richness and evenness, along with the highest enzyme activities (i.e. synergistic effect), and N availability did not constrain microbial activities. However, an apparent nitrification limitation suggested greater microbial specialisation and efficiency of N recovery in mixed litter. Our results highlight how mixing two recalcitrant litters can alleviate N limitation and could explain transition in Mediterranean forest secondary succession.

Long‐term responses of leaf litter decomposition to temperature, litter quality and litter mixing in plateau wetlands

SummaryDecomposition of plant litter is a key process in the flow of energy and nutrients in ecosystems. The extent and mechanisms towards which climate warming will affect litter decomposition in plateau wetlands remains largely unknown.We conducted a two‐year litter decomposition experiment along an elevation gradient from 1891 to 3260 m in China using litter from two dominant species of plateau wetland plants to determine the influences of temperature, litter quality and litter mixing on decomposition.The decomposition rate was significantly correlated with water temperature during the plant growing seasons and with litter quality during the winters. The temperature sensitivity of litter decomposition (Q10) wasc. 3.02 along the elevation gradient, but mixed litter was more sensitive to temperature than the litter of eitherScirpus tabernaemontani(grey club‐rush: Cyperaceae) orZizania caduciflora(wild rice: Gramineae) alone.The concentration of nitrogen (N) and the ratio of N:P (phosphorus) had positive effects but the concentration of carbon (C) and the ratios of C:N and lignin:N had negative effects on the decomposition rate, especially during the winter. In addition, N concentration and the ratio of C:N were more significantly correlated with decomposition rate during the first winter, while the ratio of lignin:N was more significantly correlated with decomposition during the second winter.Consequently, climate warming may significantly impact biogeochemical cycling of plateau wetlands, notably C storage.

Flower litters of alpine plants affect soil nitrogen and phosphorus rapidly in the eastern Tibetan Plateau

Abstract. Litters of reproductive organs have rarely been studied despite their role in allocating nutrients for offspring reproduction. This study determines the mechanism through which flower litters efficiently increase the available soil nutrient pool. Field experiments were conducted to collect plant litters and calculate biomass production in an alpine meadow of the eastern Tibetan Plateau. C, N, P, lignin, cellulose content, and their relevant ratios of litters were analyzed to identify their decomposition features. A pot experiment was performed to determine the effects of litter addition on the soil nutrition pool by comparing the treated and control samples. The litter-bag method was used to verify decomposition rates. The flower litters of phanerophyte plants were comparable with non-flower litters. Biomass partitioning of other herbaceous species accounted for 10–40 % of the aboveground biomass. Flower litter possessed significantly higher N and P levels but less C ∕ N, N ∕ P, lignin ∕ N, and lignin and cellulose concentrations than leaf litter. The litter-bag experiment confirmed that the flower litters of Rhododendron przewalskii and Meconopsis integrifolia decompose approximately 3 times faster than mixed litters within 50 days. Pot experiment findings indicated that flower litter addition significantly increased the available nutrient pool and soil microbial productivity. The time of litter fall significantly influenced soil available N and P, and soil microbial biomass. Flower litters fed the soil nutrition pool and influenced nutrition cycling in alpine ecosystems more efficiently because of their non-ignorable production, faster decomposition rate, and higher nutrient contents compared with non-flower litters. The underlying mechanism can enrich nutrients, which return to the soil, and non-structural carbohydrates, which feed and enhance the transitions of soil microorganisms.

A quality enhancement green strategy for broiler meat by application of turmeric (Curcuma longa) powder as litter amendment to affect microbes, ammonia emission, pH and moisture

In multi-cultural Sri Lankan conditions, poultry meat is paramount importance in ensuring food security and improving nutrition. Issues as contact dermatitis and ammonia emission in broiler industry which caused by diminished litter parameters cause reduction of meat quality, profits and environmental conditions. Therefore use of Turmeric (Curcuma longa) (TM) powder as an antiseptic litter amendment at several application levels to enhance litter parameters with microbial demolition was attempted. Three months old broiler litter (2 kg) sample was taken and initial pH and moisture was determined. Turmeric was used to mix at levels of 0%, 1%, 3%, 5% and 8% (w/w). After mixing, 150 g of mixed litter was placed in container for each level of the 4 replicates, incubated for 5h and analyzed for Total Plate Count (TPC), Yeast and Mold Count (YMC), total Nematode Count (NC), ammonia emission, pH and moisture. Significant reduction (p &lt;0.05) of total bacteria was seen (20%, 46%, 95% and 96%) when 1%, 3%, 5% and 8% applications of TM. The YMC reduction was also significant (p &lt;0.05) (34%, 41%, 55% and 65%). Total nematode reduction (p &lt;0.05) was 22%, 45%, 62.5% and 70%. A significant (p &lt;0.05) pH reduction with increment of TM also seen (0.1, 2, 3 and 3%). Moisture (%) was increased (p &lt;0.05) (6, 0.78, 19 and 1%). Ammonia emission was significantly decreased (p &lt;0.05) by increased TM (64, 68, 73 and 84%) against control. It was concluded that the bacterial, fungal, nematode counts, pH and Ammonia emission of broiler litter can be significantly reduced with the application of 8% (w/w) of turmeric powder.