Litter Quality Research Articles

Chronic enhanced nitrogen deposition and elevated precipitation jointly benefit soil microbial community in a temperate forest

Global change profoundly impacts carbon and nitrogen (N) cycling processes in terrestrial ecosystems by altering soil microbial communities. However, how enhanced N deposition and elevated precipitation jointly affect soil microbes and the underlying mechanisms remain poorly understood, particularly in forest ecosystems. In a long-term field experiment conducted in a temperate forest in China, we added N and/or water above the forest canopy to investigate their effects on soil microbial communities. Our results showed that N addition led to a decrease in bacterial biomass while increasing fungal biomass, resulting in an alteration of soil microbial community structure. Conversely, water addition did not significantly impact soil microbial communities. However, when N and water were added together, both fungal and bacterial biomass notably increased, leading to alterations in the soil microbial community structure. These results suggested that the effect of N addition could be mediated by elevated precipitation. Precipitation increment amplified the positive impact of N deposition on soil fungi but shifted its impact on bacteria from negative to positive. Additionally, soil bacteria were affected by soil N availability and acidification, as well as litter quality, whereas fungi were regulated by litter quantity and soil organic carbon. This study provides crucial evidence that concurrent enhanced N deposition and elevated precipitation favor soil microbial communities in temperate forests. It highlights the potential of elevated precipitation to alleviate the negative impacts of enhanced N deposition on temperate forest ecosystems, thereby sustaining ecological stability under global change scenarios.

Effects of Leaf Size and Defensive Traits on the Contribution of Soil Fauna to Litter Decomposition

Leaf litter quality has been acknowledged as a crucial determinant affecting litter decomposition on broad spatial scales. However, the extent of the contribution of soil fauna to litter decomposability remains largely uncertain. Nor are the effects of leaf size and defensive traits on soil fauna regulating litter decomposability clear when compared to economics traits. Here, we performed a meta-analysis of 81 published articles on litterbag experiments to quantitatively evaluate the response ratio of soil fauna to litter decomposition at the global level. Our results revealed that soil fauna significantly affected litter mass loss across diverse climates, ecosystems, soil types, litter species, and decomposition stages. We observed significantly positive correlations between the response ratio of soil fauna and leaf length, width, and area, whereas the concentrations of cellulose, hemicellulose, total phenols, and condensed tannins were negatively correlated. Regarding economic traits, the response ratio of soil fauna showed no relationship with carbon and nitrogen concentrations but exhibited positive associations with phosphorus concentration and specific leaf area. The mean annual temperature and precipitation, and their interactions were identified as significant moderators of the effects of soil fauna on litter decomposition. We evidenced that the contribution of soil fauna to litter decomposability is expected to be crucial under climate change, and that trait trade-off strategies should be considered in modulating litter decomposition by soil fauna.

Reparameterizing Litter Decomposition Using a Simplified Monte Carlo Method Improves Litter Decay Simulated by a Microbial Model and Alters Bioenergy Soil Carbon Estimates

AbstractLitter decomposition determines soil organic matter (SOM) formation and plant‐available nutrient cycles. Therefore, accurate model representation of litter decomposition is critical to improving soil carbon (C) projections of bioenergy feedstocks. Soil C models that simulate microbial physiology (i.e., microbial models) are new to bioenergy agriculture, and their parameterization is often based on small datasets or manual calibration to reach benchmarks. Here, we reparameterized litter decomposition in a microbial soil C model (CORPSE ‐ Carbon, Organisms, Rhizosphere, and Protection in the Soil Environment) using the continental‐scale Long‐term Inter‐site Decomposition Experiment Team (LIDET) dataset which documents decomposition across a range of litter qualities over a decade. We conducted a simplified Monte Carlo simulation that constrained parameter values to reduce computational costs. The LIDET‐derived parameters improved modeled C and nitrogen (N) remaining, decomposition rates, and litter mean residence times as compared to Baseline parameters. We applied the LIDET litter decomposition parameters to a microbial bioenergy model (Fixation and Uptake of Nitrogen – Bioenergy Carbon, Rhizosphere, Organisms, and Protection) to examine soil C estimates generated by Baseline and LIDET parameters. LIDET parameters increased estimated soil C in bioenergy feedstocks, with even greater increases under elevated plant inputs (i.e., by increasing residue, N fertilization). This was due to the integrated effects of plant litter quantity, quality, and agricultural practices (tillage, fertilization). Collectively, we developed a simple framework for using large‐scale datasets to inform the parameterization of microbial models that impacts projections of soil C for bioenergy feedstocks.

Trophic cascades within and across ecosystems: The role of anti-predatory defences, predator type and detritus quality.

Species in one ecosystem can indirectly affect multiple biodiversity components and ecosystem functions of adjacent ecosystems. The magnitude of these cross-ecosystem effects depends on the attributes of the organisms involved in the interactions, including traits of the predator, prey and basal resource. However, it is unclear how predators with cross-ecosystem habitat interact with predators with single-ecosystem habitat to affect their shared ecosystem. Also, unknown is how such complex top-down effects may be mediated by the anti-predatory traits of prey and quality of the basal resource. We used the aquatic invertebrate food webs in tank bromeliads as a model system to investigate these questions. We manipulated the presence of a strictly aquatic predator (damselfly larvae) and a predator with both terrestrial and aquatic habitats (spider), and examined effects on survival of prey (detritivores grouped by anti-predator defence), detrital decomposition (of two plant species differing in litter quality), nitrogen flux and host plant growth. To evaluate the direct and indirect effects each predator type on multiple detritivore groups and ultimately on multiple ecosystem processes, we used piecewise structural equation models. For each response variable, we isolated the contribution of different detritivore groups to overall effects by comparing alternate model formulations. Alone, damselfly larvae and spiders each directly decreased survival of detritivores and caused multiple indirect negative effects on detritus decomposition, nutrient cycling and host plant growth. However, when predators co-occurred, the spider caused a negative non-consumptive effect on the damselfly larva, diminishing the net direct and indirect top-down effects on the aquatic detritivore community and ecosystem functioning. Both detritivore traits and detritus quality modulated the strength and mechanism of these trophic cascades. Predator interference was mediated by undefended or partially defended detritivores as detritivores with anti-predatory defences evaded consumption by damselfly larvae but not spiders. Predators and detritivores affected ecosystem decomposition and nutrient cycling only in the presence of high-quality detritus, as the low-quality detritus was consumed more by microbes than invertebrates. The complex responses of this system to predators from both recipient and adjacent ecosystems highlight the critical role of maintaining biodiversity components across multiple ecosystems.

Effects of Soil Fauna on the Home-Field Advantage of Litter Total Phenol and Condensed Tannin Decomposition

Soil fauna play a vital role in contributing to the home-field advantage (HFA: litter decomposes faster in its natural habitat than elsewhere) during litter decomposition. Whether the presence of soil fauna affects the HFA of the decomposition of total phenols and condensed tannins, which are important components of litter, has rarely been investigated. In this study, litterbags with different mesh sizes were transplanted reciprocally, 0.04 mm (basically excluding soil fauna) and 3 mm (basically allowing all soil fauna to enter), in Lindera megaphylla and Cryptomeria fortunei forests. The results illustrated that the loss rates of total phenols and condensed tannins reached 64.07% to 84.49% and 69.67% to 88.37%, respectively, after 2 months of decomposition. Moreover, soil fauna positively contributed to the decomposition of condensed tannins in high-quality litter. After 2 months of decomposition, a significantly positive HFA (HFA index: 10.32) was found for total phenol decomposition in the coarse mesh, while a significantly negative HFA (HFA index: −1.81) was observed for condensed tannin decomposition in the fine mesh after 10 months of decomposition. Polyphenol oxidase (PPO) and peroxidase (POD) activities were significantly influenced by litter types. The loss rates of total phenols and condensed tannins were significantly negatively correlated with the initial N content, P content, N/P ratio, and POD activity and were positively related to the initial C content, total phenol content, condensed tannin content, C/P ratio, and C/N ratio. Only the loss of condensed tannins was negatively correlated with PPO activity (after 2 months’ decomposition). However, none of these correlations were observed after 10 months of decomposition. Our study illustrated that (1) soil fauna contributed to the decomposition of total phenols and condensed tannins but were influenced by litter type for condensed tannins. (2) The soil fauna had inconsistent effects on the HFA of total phenols and condensed tannins, possibly due to the combined regulatory effects of environmental context, litter quality, and rapid decomposition rates. In sum, the results indicated that soil fauna played an important role in the decomposition of condensed tannins and total phenols in litter, and additional studies on the effects of soil faunal abundance and class on HFA of condensed tannins and total phenols are needed.

The Effectiveness of Utilizing Certain Ingredients that Enhance the Characteristics of the Old and Used Litter on the Productive Performance of Broilers

Research aims to determine if certain modifications can improve the quality of litter and the growth and health of broiler chickens. The trial used various litterimprovement agents selected for their antibacterial properties, moisture absorption, and ability to create a favorable environment for broilers. The study found that broilers raised on treated and reused litter performed considerably better than those raised on untreated litter. These additives reduced microbiological contamination and increased litter absorption, creating a cleaner environment for the broilers. Improved litter conditions also improved broiler development, feed efficiency, and health. Adding specific components to recycled litter may enhance broiler productivity. This benefits the poultry industry by providing a cost-effective and ecologically friendly way to maximize the use of aged and utilized litter and improve broiler performance. The research indicates that litter control is crucial for sustainable poultry production and the health and performance of broiler chickens.

Cover crops improve soil structure and change organic carbon distribution in macroaggregate fractions

Abstract. Soil structure is sensitive to intensive soil management. It can be ameliorated by a reduction in soil cultivation and stimulation of plant and microbial mediators for aggregate formation, with the latter being a prerequisite and measure for soil quality. Cover crops (CCs) are part of an integrated approach to stabilize or improve soil quality. Thereby, the incorporation of diverse CC mixtures is hypothesized to increase the positive effects of CC applications. This study entailed an investigation of the legacy effect of CCs on soil aggregates after three crop rotations in the second main crop (winter wheat) after the last CC treatment. Four CCs (mustard, phacelia, clover, and oat) cultivated in pure stands and with a fallow treatment were compared to a mixture of the four CC species (Mix4) and a highly diverse 12-plant-species mixture (Mix12) in a long-term field experiment in Germany. The organic carbon (OC) distribution within macroaggregate fractions (16–8, 8–4, 4–2, 2–1, and <1 mm) and their aggregate stability were measured by dry- and wet-sieving methods, and the mean weight diameter (MWD) was calculated from water-stable aggregates. The results showed that, compared to the fallow, all CCs increased the MWD between 10 % and 19 % in soil under the following main crop. The average MWD increase over the fallow was slightly higher for CC mixtures (16 %) than for single CCs (12 %). Most of the OC (67.9 % on average) was stored in the <1 mm aggregate fraction, highest in the topsoil and decreasing with soil depth. The intermediate fractions (8–4 mm, 4–2 mm, 2–1 mm) stored 8.5 %, 10.5 %, and 11.0 % of the total OC, while 2.1 % was stored in the 16–8 mm fraction. Higher MWD improvement at the 20–30 cm depth also indicates additional benefits from a reduction in the cultivation depth. Structural equation modelling (SEM) suggests that single CCs were more likely to increase OC storage in small macroaggregates <1 mm, while CC mixtures were more likely to increase OC in the largest fraction (8–16 mm). Different individual CC species or mixtures exhibited varying involvement in the formation of different aggregate fractions. We provide evidence that litter quality, root morphology, and rhizosphere input, which affect microbial mediators of aggregate formation, might be the main reasons for the observed differences between CC treatments. Cover crops are valuable multifunctional tools for sustainable soil management. Here, we showed that they contribute to structure amelioration in arable soils. Increasing the functional diversity of plant species in CC mixtures could be a strategy to further enhance the positive effects of CCs in agroecosystems.

Effects of Moso Bamboo (Phyllostachys pubescens) Expansion on the Stock and Nutrient Characteristics of the Litter Layer in Subtropical Coniferous and Broad-Leaved Mixed Forests, China

To reveal the changes on the stock of the litter layer and its nutrient storage capacity during Moso bamboo expansion in subtropical coniferous and broad-leaved forests, permanent plots were set up in the transitional zone in Wuxie National Park, Zhuji, Zhejiang, China. The plots contained conifer and broad-leaved forests (CFs), transition forests (TFs), and Moso bamboo forests (MFs), which represented three stages of the expansion of Moso bamboo to the surrounding forests. Litter samples were collected and analyzed by un-decomposed, semi-decomposed, and decomposed layers. The stock of the litter layer, the content and storage of the main nutrient elements, and their release rate were measured. It was revealed that the stock of the litter layer and each decomposition layer decreased as the bamboo expands. However, the litter decomposition rate exhibited a positive correlation with the expansion of Moso bamboo, which might be due to the change in the physical properties of the litter. Meanwhile, there were no significant differences in the un-decomposed and semi-decomposed layers of the litter contents of C, N, and P between the three forests, but the contents of C, N, and P in the decomposed layer gradually decreased with the expansion of Moso bamboo. There were no remarkable differences in the N content, C/N, C/P, and lignin/N values of the un-decomposed layer of the three forests, indicating that the litter quality was not the principal reason affecting the decomposition rate. The total nutrient storage in the litter layer decreased significantly with the bamboo expansion, and the release rate of nutrient elements increased, which was adverse to the accumulation and storage of the nutrients. The material cycle of the original forest ecosystem is likely to deteriorate gradually with the bamboo expansion.

Detritivores accelerate litter mixture decomposition effect via greater consumption of high quality litter.

To explore the mixing effect of litter decomposition and the role of detritivores, we conducted a laboratory-based microcosm experiment to study the influence of detritivores on litter mixture decomposition by using two litter species with contrasting quality, i.e., Cinnamomum camphora and Michelia × alba, and a detritivore (isopoda). After 100 days incubation, the decomposition rate of litter mixture was 52.1%, slower than that of M. alba (62.6%) and significantly faster than that of C. camphora (33.6%). The addition of isopods significantly increased litter decomposition rate, with C. camphora, M. alba, and the mixture increased by 14.4%, 20.1% and 22.1%, respectively. There was no significant mixing effect without isopods. Adding isopods significantly promoted the mixing effect of litter decomposition, with a value of the litter mixture decomposition effect of 8.6%. The detritivores increased litter decomposition rate and mixing effect through increasing consumption of litter with better quality.

Lignin and Cellulose Contents in Chinese Red Pine (Pinus tabuliformis Carr.) Plantations Varied in Stand Structure, Soil Property, and Regional Climate

The reserve of litter is expected to be reduced on the forest floors of pine plantations dually for the prevention of high risks of forest fires and with a more practical probability of reuse. Lignin and cellulose are the two key constitutive components in litter residues that account for the highest proportion of carbon but are the last to be fully decomposed. The existing trials started examining the mechanisms behind decomposing these two components in response to the combined driving forces of microclimatic factors, forest structure, and stand properties. However, the results were mostly limited to a local-scale ecosystem, and the evidence was reported to be highly scattered across varied conditions globally. Awareness about the combined effects of the driving forces behind the lignin and cellulose contents in the litter of plantations on a large scale is still scarce. In this study, a total of 60 Pinus tabuliformis Carr. plantations (40-year-old) were investigated for their litter quality, regional meteorological factors, soil properties, and stand structure in a provincial area across Liaoning, northeast China. High lignin (40%–43%) and cellulose contents (15%–20%) were found to be located mainly in stands around the biggest city of Shenyang. Rainfall was a key factor that determined the decomposition, but neither the forest structure nor soil nutrient content generated direct effects on the two litter components. The combined factors of low soil pH (~5.8) and high rainfall (~3.0 mm per day) together mainly accounted for the promotion of natural litter decomposition.

A walk through the broiler breeder life: how do footpad dermatitis and gait scores develop from rearing to slaughter?

ABSTRACT The two most common animal-based indicators used to evaluate leg health in broiler chickens are footpad dermatitis (FPD) and gait scoring, but these indicators are less explored in broiler breeders. This study is the first to investigate FPD and gait scoring in broiler breeders during their lifespan from rearing to end of life. In total, eight flocks were monitored (four Ross and four Hubbard) at five different timepoints, in rearing (5 and 15 weeks of age), during the production period (25 and 45 weeks of age) and at the end of the production period (approximately 60 weeks of age). At each visit, 50 hens and 25 roosters were gait scored (six-point scale) and footpads from another 50 hens and 25 roosters were evaluated (five-point scale) (total n = 3000 breeders, 2000 hens and 1000 roosters). Litter quality and air quality were measured at each visit. The results showed that the overall prevalence of FPD in rearing was low and that it increased towards the end of the production, with a mean FPD score of 2 out of a maximum 4 in the hens, indicating moderate lesions and 1.5 in the roosters. In all houses, the litter was dry and loose. FPD was not related to the litter quality, but to air quality, especially the ammonia concentration (P < 0.001). Overall, the gait score were good, and increased with age in both hens (P < 0.001) and roosters of both hybrids (P < 0.001).

Synchronic shifts in phenolic compounds and fungal communities during litter decomposition in boreal forests

Phenolic compounds in plant litter influence decomposition process both directly by their own degree of decomposability and indirectly by affecting decomposer processes. While phenolic characteristics of aboveground plant biomass are well-known, the fate of litter phenolics and their regulatory effects on belowground decomposition remain unclear. We conducted a two-year decomposition experiment distributing litterbags of spruce, pine, and bilberry along a gradient from mesic spruce-dominated to xeric pine-dominated forests. Litter material was analysed for mass loss, low molecular weight phenolic compounds, condensed tannins, fungal biomass, and fungal community composition (using DNA metabarcoding). Bilberry litter initially decayed more rapidly than the conifer litter, but the remaining mass of bilberry litter was the same as for pine and higher than that of spruce litter after two years. The concentration and composition of phenolic compounds decreased with time, with mainly MeOH-insoluble condensed tannins remaining at the end of the experiment. Correspondingly, fungal biomass increased in the first year, while all litter types underwent rapid changes in fungal community composition. The species-specific pattern of temporal change in mass loss, as well as in the synchronic shift in composition of phenolic compounds and fungal community, give new insights in the importance of litter quality for the decomposition process.

Litter quality controls the contribution of microbial carbon to main microbial groups and soil organic carbon during its decomposition

Litter quality controls the contribution of microbial carbon to main microbial groups and soil organic carbon during its decomposition

Decentralized Forest Governance and Resource Management: Assessing Community Dependence and Conservation Effectiveness in Broad-Leaved and Coniferous Forest Stands

Globally decentralized forest governance is being promoted to conserve and sustainably manage forest resources along with meeting local livelihoods. In the Central Himalayan region of India, it came into existence in 1931, long before the time when the concept of decentralized forest governance became popular globally, and the aim was to accomplish the subsistence needs of the smallholders in the region. This article discusses whether the species types (broadleaved and coniferous) affect biophysical conditions, species richness, and conservation effectiveness of community-owned forests (locally called Van Panchayat forests), and what could be done to improve their management in the near future. The findings are based on a household survey covering 16 villages as well as a biophysical assessment of 18 community forest stands (9 per forest type) covering an area of 1778 ha and 341 ha in both forest categories. It was found that farmers across the villages are intricately dependent on forest resources to support their livelihoods that are governed by a village institution (Van Panchayat) to maintain equity of benefit-sharing among all stakeholders. Both forest categories exhibited high dependence, however, there was a considerable difference in resource quality, viz. quality of fodder, fuel, and litter in broadleaved forests, therefore the community has more preference for such stands. The broadleaved Banj-oak stands revealed better biophysical status in terms of species diversity, tree density, total basal area, and regeneration than the coniferous Chir-pine stands. Although the local government has taken up selective policy initiatives to encourage decentralized forest governance, more needs to be done to strengthen it on the ground level, particularly in Chir-pine stands. It is suggested that the community management of forests needs to be improved in relation to leadership development, rationale use of bio-resources, and adopting site-specific management strategies. In areas with Chir-pine forests community need to be educated to reduce forest fire and promote the plantation of broad-leaved species. Also, the scope of community forests needs to be broadened by adopting and involving smallholders in various forest enterprise development and climate action programs. For this, developing proper alliances of village institutions with civil society groups and other partner institutions along with virtuous support from local government can lead to enhance social and environmental resilience of communities.

Soil extracellular enzyme stoichiometry reveals the nutrient limitations in soil microbial metabolism under different carbon input manipulations

Changes in the quality and quantity of litter and root inputs due to climate change and human activities can influence below-ground biogeochemical processes in forest ecosystems. However, it is unclear whether and how much aboveground litter and root inputs affect soil microbial metabolism and nutrient limitation mechanisms. In this study, according to a 4-years field manipulation experiment, litter and root manipulations (control (CK), double litter input (DL), no litter (NL), no root (NR), and no inputs (NI)) were set up to analyze the extracellular enzyme activities and stoichiometric ratios characteristics of 0–10 cm and 10–20 cm soils, explore the metabolic limitations of microorganisms, and clarify the main driving factors restricting nutrient limitation. The results showed that the enzyme activities associated with the C cycling (β-1,4-glucosidase (BG), cellulose disaccharide hydrolase (CBH)) and N cycling (β-1,4-N-acetylglucosaminidase (NAG), leucine aminopeptidase (LAP)) in DL treatment were significantly higher than those in NR treatment. Moreover, enzyme activities related to P cycling are significantly higher in comparison to other treatments. The acid phosphatase (AP), which is related to the P cycle, showed the highest activity under NR treatment. In addition, there was no significant difference in soil microbial metabolic limitation by the different carbon inputs, which did not change the original nutrient limitation pattern. The main drivers of microbial nutrient metabolic limitation included soil physicochemical properties, soil total nutrients, and available nutrients, among which soil SWC and pH presented the greatest influence on microbial C limitation and soil total nutrients showed the greatest influence on microbial N limitation. Changes in soil carbon input altered soil extracellular enzyme activities and their stoichiometric ratios by affecting soil physicochemical properties, total nutrients. This study provides data for the understanding of material cycling in forest ecosystems under environmental change.

Influence of using perforated plastic flooring beneath the waterline on animal distribution of broiler chickens correlated with litter quality

Influence of using perforated plastic flooring beneath the waterline on animal distribution of broiler chickens correlated with litter quality

Leaf litter nutrient content reveals benefits to traditional cropping systems in the Amazon

Soil fertility in the Amazon rainforest is very dependent to litter decomposition as a source of organic carbon and nutrients. Thus, land use that promote high litter decomposition might play a positive influence on soil chemical properties. The present study aimed to quantify the nutritional content of litter in anthropized and natural environments in Southern Amazonas. The study was conducted on two properties in the municipality of Canutama, in four areas: native forest, annatto, cupuassu, and guarana. In each area, 10 conical collectors (0.21 m²) were installed at a height of 0.3 m from the ground. The samples collected in each area for each month were dried in a forced circulation oven at 60ºC until reaching constant mass and weighed. Macro- and micronutrient content analyses were performed by sulfuric solubilization (N), nitric perchloric solubilization (Ca, Mg, P, K, Na, S, Cu, Fe, Mn, and Zn) and incineration (B). Variance analysis and comparison of means by Tukey test at the 5% probability level were applied to the data obtained, along with a multivariate analysis. This comparison was carried out by evaluating the overall average of a whole year of litter formation, as well as for formation within each month evaluated. Sulfur (S) was the only macronutrient that did not differ between environments (0.1 and 0.2 g kg-1). Macronutrients and micronutrient contents of litter (N: 16.92; Mg: 1.08; Cu: 16.00; Zn: 31.70; B: 104.40; g kg-1) were significantly highest in the annatto area. Annato also presents higher K (9.92 g kg-1) and P (0.70 g kg-1) contents. The litter of natural forest and guarana are richer in P (0.88 g kg-1) and Ca (g kg-1), respectively. Cupuassu litter showed lower nutritional contents, especially in macronutrients contents (N: 9.04; P: 0.51; K: 0.28; Ca: 0.76; Mg: 0.44; g kg-1). This indicates that traditional Amazonian agroecosystems may positively to improve quality of litter and impact nutrient cycling in soils highly weathered in the region.

Effects of grain-based pecking blocks on productivity and welfare indicators in commercial broiler chickens.

This experiment was conducted to investigate the effect of grain-based pecking blocks on productivity and welfare status at two commercial broiler welfare-certified farms. Production and welfare indicators were assessed at two farms (designated Farm A and B). Both farms had two windowless houses with forced tunnel-type ventilation and housed broilers at stocking densities of approximately 16.7 birds/m2 (Farm A) and 16.8 birds/m2 (Farm B). Each house was divided into two or three equal sections and was provided with or without pecking blocks. Grain-based pecking blocks, measuring 25 × 25 × 25 cm, were given to broilers in both farms at 1 block per 1,000 birds. Various parameters including productivity (body weight and flock uniformity), corticosterone levels (in fecal droppings and feathers), footpad dermatitis, hock burn, feather dirtiness, gait score, litter quality, body surface temperature, and volatile fatty acids in fecal samples were assessed at 26 days of age, whereas litter quality was analyzed at 13 and 26 days of age. There were no significant effects of providing pecking blocks on productivity (body weight and uniformity), fecal and feather corticosterone, welfare indicators (i.e., footpad dermatitis, hock burn, feather cleanliness, and gait score), and litter quality (i.e., moisture, nitrogen, and pH). No differences in body surface temperature between the control and enrichment treatments were noted in Farm B, but body surface temperatures of the head (p = 0.029) and legs (p = 0.011) in the enrichment vs. control group were elevated in Farm A. Butyrate concentration in the enrichment vs control group was higher in Farm B (p = 0.023), but this effect was not detected in Farm A. It is concluded that grain-based pecking blocks did not affect performance and welfare indicators. Further studies are warranted to elucidate the potential impact of grain-based pecking blocks on gut health indicators.

Net Methane Production Predicted by Patch Characteristics in a Freshwater Wetland

AbstractMethane (CH4) dynamics in wetlands are spatially variable and difficult to estimate at ecosystem scales. Patches with different plant functional types (PFT) represent discrete units within wetlands that may help characterize patterns in CH4 variability. We investigate dissolved porewater CH4 concentrations, a representation of net CH4 production and potential source of atmospheric flux, in five wetland patches characterized by a dominant PFT or lack of plants. Using soil, porewater, and plant variables we hypothesized to influence CH4, we used three modeling approaches—Classification and regression tree, AIC model selection, and Structural Equation Modeling—to identify direct and indirect influences on porewater CH4 dynamics. Across all three models, dissolved porewater CO2 concentration was the dominant driver of CH4 concentrations, partly through the influence of PFT patches. Plants in each patch type likely had variable influence on CH4 via root exudates (a substrate for methanogens), capacity to transport gas (both O2 from and CH4 to the atmosphere), and plant litter quality which impacted soil respiration and production of CO2 in the porewater. We attribute the importance of CO2 to the dominant methanogenic pathway we identified, which uses CO2 as a terminal electron acceptor. We propose a mechanistic relationship between PFT patches and porewater CH4 dynamics which, when combined with sources of CH4 loss including methanotrophy, oxidation, or plant‐mediated transport, can provide patch‐scale estimates of CH4 flux. Combining these estimates with the distribution of PFTs can improve ecosystem CH4 flux estimates in heterogenous wetlands and improve global CH4 budgets.

Soil organic matter turnover: Global implications from δ13C and δ15N signatures

The turnover and residence time of carbon (C) and nitrogen (N) in soil is a fundamental parameter reflecting the rates of soil organic matter (SOM) transformation and the contribution of soils to greenhouse gases fluxes. Based on the global database of the stable isotope composition of C (δ13C) and N (δ15N) depending on soil depth (171 profiles), we assessed С and N turnover and related them to climate, biome types and soil properties. The 13C and 15N discrimination between the litter horizon and mineral soil was evaluated to explain the key processes of litter transformation. The 13C and 15N discrimination by microbial utilization of litter and SOM, as well as the continuous increase of δ13C and δ15N with depth, enabled to assess C and N turnover within SOM. N turnover was two times faster than that of C, which reflects i) repeated N recycling by microorganisms accelerating N turnover, ii) C loss as CO2 and input of new C atoms to cycling, which reduces the C turnover within soil, and iii) generally slower turnover of N free persistent organic compounds (e.g. lignin, suberin, cellulose) compared to the N containing compounds (e.g. amino acids, ribonucleic acids). An increase in temperature and precipitation accelerated C and N turnover because: i) higher microbial activity and SOM decomposition rate, ii) larger soil moisture and fast diffusion of dissolved organics towards exoenzymes, iii) downward transport of 13C-enriched organic matter (e.g. sugars, amino acids), and iii) leaching of 15N-depleted nitrates from the topsoil into subsoil and losses from the whole soil profile. Temperature accelerates SOM turnover stronger than precipitation. The temperature increase by 10 °C accelerates the C and N turnover for 40 %. SOM turnover is boosted by decreasing C/N ratio because: i) SOM with a high C/N ratio originated from litter is converted to microbially-derived SOM in mineral soil characterized by a low C/N ratio; ii) litter with a low C/N ratio is decomposed faster than litter with a high C/N; iii) microbial carbon-use efficiency increases with N availability. The biome type affects SOM decomposition by i) climate: slower turnover under wet and cold conditions, and ii) by litter quality: faster utilization of leaves than needles. Thus, the fastest C turnover is common under evergreen forests and the lowest under mixed and coniferous ones, whereas temperature and C/N ratio are the main factors controlling SOM turnover. Concluding, the assessment of SOM turnover by δ13C and δ15N approach showed two times faster N turnover compared to C, and specifics of SOM turnover depending on the biomes as well as climate conditions.