Query: litter

title: Resource ratio theory predicts mycorrhizal control of litter decomposition.
abstract: Ecosystems with ectomycorrhizal plants have high soil carbon:nitrogen ratios, but it is not clear why. The Gadgil effect, where competition between ectomycorrhizal and saprotrophic fungi for nitrogen slows litter decomposition, may increase soil carbon. However, experimental evidence for the Gadgil effect is equivocal. Here, we apply resource ratio theory to assess whether interguild fungal competition for different forms of organic nitrogen can affect litter decomposition. We focus on variation in resource input ratios and fungal resource use traits, and evaluate our model's predictions by synthesizing prior experimental literature examining ectomycorrhizal effects on litter decomposition. In our model, resource input ratios determined whether ectomycorrhizal fungi suppressed saprotrophic fungi. Recalcitrant litter inputs favored the former over the latter, allowing the Gadgil effect only when such inputs predominated. Though ectomycorrhizal fungi did not always hamper litter decomposition, ectomycorrhizal nitrogen uptake always increased carbon:nitrogen ratios in litter. Our meta analysis of empirical studies supports our theoretical results: ectomycorrhizal fungi appear to slow decomposition of leaf litter only in forests where litter inputs are highly recalcitrant. We thus find that the specific contribution of the Gadgil effect to high soil carbon:nitrogen ratios in ectomycorrhizal ecosystems may be smaller than previously predicted. This article is protected by copyright. All rights reserved.

title: Biodiversity of leaf litter fungi in streams along a latitudinal gradient.
abstract: Global patterns of biodiversity have emerged for soil microorganisms, plants and animals, and the extraordinary significance of microbial functions in ecosystems is also well established. Virtually unknown, however, are large scale patterns of microbial diversity in freshwaters, although these aquatic ecosystems are hotspots of biodiversity and biogeochemical processes. Here we report on the first large scale study of biodiversity of leaf litter fungi in streams along a latitudinal gradient unravelled by Illumina sequencing. The study is based on fungal communities colonizing standardized plant litter in 19 globally distributed stream locations between 69degN and 44degS. Fungal richness suggests a hump shaped distribution along the latitudinal gradient. Strikingly, community composition of fungi was more clearly related to thermal preferences than to biogeography. Our results suggest that identifying differences in key environmental drivers, such as temperature, among taxa and ecosystem types is critical to unravel the global patterns of aquatic fungal diversity.

title: Earthworm Cast Formation and Development: A Shift From Plant Litter to Mineral Associated Organic Matter
abstract: Earthworms play a major role in litter decomposition, in processing soil organic matter and driving soil structure formation. Earthworm casts represent hot spots for carbon turnover and formation of biogeochemical interfaces in soils. Due to the complex microscale architecture of casts, understanding the mechanisms of cast formation and development at a process relevant scale, i.e. within microaggregates and at the interface between plant residues, microorganisms and mineral particles, remains challenging. We used stable isotope enrichment to trace the fate of shoot and root litter in intact earthworm cast samples. Surface casts produced by epi anecic earthworms (Lumbricus terrestris) were collected after 8 and 54 weeks of soil incubation in mesocosms, in the presence of 13C labeled Ryegrass shoot or root litter deposited onto the soil surface. To study the alteration in the chemical composition from initial litter to particulate organic matter (POM) and mineral associated organic matter (MOM) in cast samples, we used solid state 13C Nuclear Magnetic Resonance spectroscopy (13C CPMAS NMR) and isotopic ratio mass spectrometry (EA IRMS) We used spectromicroscopic approach to identify plant tissues and microorganisms involved in plant decomposition within casts. A combination of transmission electron microscopy (TEM) and nano scale secondary ion mass spectrometry (NanoSIMS) was used to obtain the distribution of organic carbon and d13C within intact cast sample structures. We clearly demonstrate a different fate of shoot and root derived organic carbon in earthworm casts, with a higher abundance of less degraded root residues recovered as particulate organic matter on the short term (8 weeks) (73 mg.g 1 in Cast Root vs 44 mg.g 1 in Cast Shoot) At the early stages of litter decomposition, the chemical composition of the initial litter was the main factor controlling the composition and distribution of soil organic matter within casts. At later stages, we can demonstrate a clear reduction of structural and chemical differences in root and shoot derived organic products. After one year, MOM clearly dominated the casts (more than 85 of the total OC in the MOM fraction) We were able to highlight the shift from a system dominated by free plant residues to a system dominated by MOM during cast formation and development.

title: A State of the Art Compact Surface Drifter Reveals Pathways of Floating Marine Litter in the German Bight
abstract: Lagrangian observations are important for the understanding of complex transport patterns of floating macroscopic litter items at the ocean surface. Satellite tracked drifters and numerical models are an important source of information relevant to transport processes as well as distribution patterns of floating marine litter (FML) on a regional to global scale. Sub mesoscale processes in coastal and estuarine systems have an enormous impact on pathways and accumulation zones of FML and are yet to be fully understood. Here we present a state of the art, low cost and robust design of a satellite tracked low cost drifter applicable in studying complex pathways and sub mesoscale dynamics of floating litter in tidally influenced coastal and estuarine systems. It is compact, lightweight less than 5 kg, capable of refloating, easily recovered and modified. The drifter motion resolves currents of the ocean surface layer (top 0.5 m layer) taking into account wind induced motions. We further showcase findings from seven of our custom made drifters deployed from RV Heincke and RV Senckenberg in the German Bight during spring and autumn 2017. Drifter velocities were computed from high resolved drifter position data and compared to local wind field observations. It was noted that the net transport of the drifters in areas far away from the coast was dominated by wind driven surface currents, 1 of the wind speed, whereas the transport pattern in coastal areas was mainly overshadowed by local small scale processes like tidal jet currents, interactions with a complex shoreline and fronts generated by riverine freshwater plumes.

title: The Role of Plant Litter in Driving Plant Soil Feedbacks
abstract: Most studies focusing on plant soil feedbacks (PSFs) have considered direct interactions between plants, abiotic conditions (e. g. soil nutrients) and rhizosphere communities (e.g. pathogens, mutualists) However, few studies have addressed the role of indirect interactions mediated by plant litter inputs. This is problematic because it has left a major gap in our understanding of PSFs in natural ecosystems, where plant litter is a key component of feedback effects. Here, we propose a new conceptual framework that integrates rhizosphere and litter mediated PSF effects. Our framework provides insights into the relative contribution of direct effects mediated by interactions between plants and soil rhizosphere organisms, and indirect effects between plants and decomposer organisms mediated by plant root and shoot litter. We distinguish between three pathways through which senesced root and shoot litter may influence PSFs. Specifically, we examine: (1) physical effects of litter (layer) traits on seed germination, soil structure, and plant growth; (2) chemical effects of litter on concentrations of soil nutrients and secondary metabolites (e.g. allelopathic chemicals) and (3) biotic effects of saprotrophic soil communities that can perform different functional roles in the soil food web, or that may have specialized interactions with litter types, thereby altering soil nutrient cycling. We assess the role of litter in PSF effects via physical, chemical and biotic pathways to address how litter mediated feedbacks may play out relative to, and in interaction with, feedbacks mediated through the plant rhizosphere. We also present one of the first experimental studies to show the occurrence and species specificity of litter mediated feedbacks and we identify critical research gaps. By formally incorporating the plant litter feedback pathway into PSF experiments, we will further our understanding of PSFs under natural conditions.

title: How Safe is Chicken Litter for Land Application as an Organic Fertilizer? A Review
abstract: Chicken litter application on land as an organic fertilizer is the cheapest and most environmentally safe method of disposing of the volume generated from the rapidly expanding poultry industry worldwide. However, little is known about the safety of chicken litter for land application and general release into the environment. Bridging this knowledge gap is crucial for maximizing the benefits of chicken litter as an organic fertilizer and mitigating negative impacts on human and environmental health. The key safety concerns of chicken litter are its contamination with pathogens, including bacteria, fungi, helminthes, parasitic protozoa, and viruses; antibiotics and antibiotic resistant genes; growth hormones such as egg and meat boosters; heavy metals; and pesticides. Despite the paucity of literature about chicken litter safety for land application, the existing information was scattered and disjointed in various sources, thus making them not easily accessible and difficult to interpret. We consolidated scattered pieces of information about known contaminants found in chicken litter that are of potential risk to human, animal, and environmental health and how they are spread. This review tested the hypothesis that in its current form, chicken litter does not meet the minimum standards for application as organic fertilizer. The review entails a meta analysis of technical reports, conference proceedings, peer reviewed journal articles, and internet texts. Our findings indicate that direct land application of chicken litter could be harming animal, human, and environmental health. For example, counts of pathogenic strains of Eschericia coli (105 1010 CFU g 1) and Coliform bacteria (106 108 CFU g 1) exceeded the maximum permissible limits (MPLs) for land application. In Australia, 100% of broiler litter tested was contaminated with Actinobacillus and re used broiler litter was more contaminated with Salmonella than non re used broiler litter. Similarly, in the US, all (100% broiler litter was contaminated with Eschericia coli containing genes resistant to over seven antibiotics, particularly amoxicillin, ceftiofur, tetracycline, and sulfonamide. Chicken litter is also contaminated with a vast array of antibiotics and heavy metals. There are no standards set specifically for chicken litter for most of its known contaminants. Even where standards exist for related products such as compost, there is wide variation across countries and bodies mandated to set standards for safe disposal of organic wastes. More rigorous studies are needed to ascertain the level of contamination in chicken litter from both broilers and layers, especially in developing countries where there is hardly any data; set standards for all the contaminants; and standardize these standards across all agencies, for safe disposal of chicken litter on land.

title: Grazing Management and Buffer Strip Impact on Nitrogen Runoff from Pastures Fertilized with Poultry Litter.
abstract: Nitrogen runoff from pastures fertilized with animal manure, such as poultry litter, can result in accelerated eutrophication. The objective of this study was to evaluate the long term effects of grazing management and buffer strips on N runoff from pastures fertilized with poultry litter. A 12 yr study was conducted on 15 small watersheds in Booneville, AR, using five management practices: continuous grazing, haying, rotational grazing, rotational grazing with an unfertilized buffer strip, and rotational grazing with a fenced unfertilized riparian buffer. Poultry litter was applied annually at a rate of 5.6 Mg ha. Concentrations and loads of total N, NO N, NH N, organic N, and total organic C in runoff varied intra and interannually and coincided with precipitation trends. Overall, the greatest component of total N in runoff was organic N. Rotational grazing resulted in the highest concentrations and loads of all forms of N in runoff compared with other treatments, including the continuously grazed paddocks, which were grazed almost twice as much. Total organic C concentrations and loads in runoff were also higher from rotationally grazed watersheds than other treatments. Rotational grazing is considered a best management practice that typically reduces soil erosion; hence, the mechanism by which it caused higher N and C runoff is unclear. Nitrogen runoff losses from rotationally grazed pastures were reduced by 44% with unfertilized buffer strips, by 54% with fenced unfertilized riparian buffers, and by 52% by converting pastures to hayfields.

title: One plus one is greater than two: mixing litter types accelerates decomposition of low quality alpine dwarf shrub litter
abstract: AimsLitter decomposition patterns, non additive effects, and spectral data of abundant alpine leaf litters were assessed in litterbag experiments containing single species and mixtures. We tested if low quality shrub litter decomposes faster in mixtures with high quality litter and if predictions on decomposed litter using spectral data are feasible.MethodsChemical and physical traits and near infrared reflectance (NIR) spectra of six alpine freshly fallen litter types were measured. A litterbag experiment (0.1 mm mesh size) with single and 2 and 3 species mixtures was conducted with three species from three functional groups (shrub, grass, forb) Decomposition rates, litter mass loss, non additive effects, and NIR spectra were recorded after 6, 12, and 24 months.ResultsThe six freshly fallen litter types differed significantly in leaf litter traits and NIR spectra. Decomposition rates steadily slowed during the 24 months, with shrub litter having the lowest on all sampling dates. In litter mixtures, shrub and grass litter showed higher decomposition rates after 12 and 24 months compared with the single species treatments.DiscussionThe accelerated decomposition in litter mixtures indicates stimulating interactions between low and high quality litter types, most probably mediated by their associated microbiomes. By using NIR spectra, we successfully predicted all initial litter traits, but only total carbon content along the entire decomposition period.

title: Higher soil fauna abundance accelerates litter carbon release across an alpine forest tundra ecotone
abstract: Upward shifts of alpine treelines and shrub expansion are occurring under climate change, and Abies faxoniana (AF) and Rhododendron lapponicum (RL) may become distributed at higher altitudes. How do abiotic factors and litter quality modulate the effects of soil fauna on carbon release in this context? A field decomposition experiment involving the foliar litter of AF and RL was conducted along an elevation gradient encompassing coniferous forest, alpine shrubland and alpine meadow by using litterbags with different mesh sizes (3 and 0.04 mm) The objective was to determine the influences of soil fauna, litter quality and abiotic factors on species specific carbon release and their contributions during litter decomposition. Our findings demonstrated that higher soil fauna abundance and diversity facilitated litter carbon release. The contribution rates of soil fauna to carbon release (Cfau) decreased with elevation increasing and decomposition time. Cfau are influenced by soil faunal diversity, dominant fauna groups (Collembola, Oribatida, Mesostigmata) and abiotic factors (temperature) Soil fauna significantly and directly regulated carbon release, abiotic factors indirectly regulated carbon release via altering soil fauna community composition and litter quality. This study improve our understanding in the mechanisms of decomposer contributions to carbon cycling in the context of global climate change.

title: Visual observations of floating macro litter around Italy (Mediterranean Sea)
abstract: We report the results of a visual survey of floating natural (NML) and anthropogenic (AML) macro litter >2.5 cm) performed in the central part of the Mediterranean Sea during a dual use campaign onboard the Italian Navy tall ship "Amerigo Vespucci" which circumnavigated the Italian peninsula during May June 2016. The distribution, abundance and composition of floating marine litter were assessed using a 10 m fixed width strip transect method. Over 88 h of transect counts were performed, for a total of 168 transects, covering an overall survey length of 1026.35 km. 4756 anthropogenic litter items were counted during the transects, 96.9 of which were classified as plastic items. Floating litter was found throughout the entire study area with densities ranging from 0 to 9205 items/km2 and with a mean abundance of 492 AML items/km2 and 77 NML items/km2 across all surveyed locations. Maximum AML densities >3500 items/km2) were recorded in the Adriatic Sea, while the lowest densities <50 items/km2) were found along the coastline of Sardinia and in the Strait of Messina. Our results document the ubiquitous presence of floating plastic litter around the Italian peninsula and underline the need to expand our knowledge about the main sources, transport, accumulation and fate of marine litter in the entire Mediterranean region.