Influence Decomposition Rates Research Articles

Winter Rye Cover Crop Seeding Rate and Termination Timing Effects on Cover Crop Biomass and Quality

ABSTRACT Winter rye (Secale cereale L.) biomass and chemical composition influences decomposition rates, nutrient cycling and effects on cash crop growth. Management that maintains rye biomass while lowering carbon (C) to nitrogen (N) ratios and concentrations of structural carbohydrates including hemicellulose, cellulose, and lignin could maintain some ecosystem services while accelerating nutrient cycling. Two independent studies examined (1) five rye seeding rates ranging from 0 to 90 kg ha−1 and (2) five termination dates ranging from April 19 to May 31 (585 to 1084 growing degree days) to understand management induced relationships between rye biomass, nutrient concentrations, and composition of hemicellulose, cellulose, and lignin. Rye biomass increased at seeding rates of 90 kg ha−1 as compared to the 22–67 kg ha−1 seeding rates while trends toward higher plant structural components were observed as seeding rate increased. Rye biomass accumulated rapidly beyond 819 (May 13) growing degree days while increasing rye C:N ratio and concentrations of hemicellulose and cellulose. Rye C:N ratio was strongly correlated to rye biomass (R2 = 0.80, p < .001) with a C:N ratio of 25 associated with 2000 kg ha−1 of rye biomass. Changes in rye residue quality were strongly influenced by biomass accumulation with delaying termination most significantly driving biomass changes. Trends toward lower C:N ratios and concentrations of structural carbohydrates were seen at the 22–67 kg ha−1 seeding rates even without differences in biomass suggesting lower seeding rates could cycle nutrients quicker without limiting biomass production potential.

Carbon acquisition ecological strategies to connect soil microbial biodiversity and carbon cycling

Soil carbon feedbacks to global change are uncertain, and the biological processes that govern soil organic matter decomposition are not resolved in current ecosystem models. Though it is recognized that microbial biodiversity influences decomposition rates, incorporating this relationship into ecosystem models is challenging because microbial communities are prohibitively diverse. It is likely necessary to distill microbial biodiversity by focusing on functional groups or ecological strategies. The ecological strategies that currently dominate the microbial ecology literature derive from macroecological theory, have clear weaknesses, and have had limited success when applied to predict soil carbon dynamics. Here, we present a new framework for soil microorganisms: Carbon Acquisition Ecological Strategies (CAES), and we outline a path toward incorporating microbial biodiversity into ecosystem models using this framework to enhance predictions of soil carbon feedbacks to global change. Because a microorganism's diet is central to its ecological niche and likely to covary with other ecologically significant traits, we posit that carbon acquisition may serve as a tractable foundation for developing ecological strategies. We describe four candidate ecological strategies for soil microorganisms: 1° decomposers that assimilate complex plant polymers, 2° decomposers that assimilate microbial necromass, passive consumers that assimilate dissolved organic carbon, and predatory microbes that assimilate live microbial biomass. These strategies are directly linked to soil carbon pools currently represented in ecosystem models and may provide a foundation for greater integration of microbial community dynamics into ecosystem models.

Uncovering Forensic Taphonomic Agents: Animal Scavenging in the European Context.

Simple SummaryIn forensic cases of exposed human bodies, vertebrate animals frequently pose challenges concerning remains recovery, identification, and the interpretation of circumstances of death. For instance, they can remove body parts, destroy skeletal features, and create “pseudo-lesions” that complicate trauma analysis. With this review, we highlight vertebrate scavengers in Europe that are of forensic relevance, including their typical behaviour and their inflicted lesions on bones and soft tissues. Here, we support forensic practitioners in recognising animal activity at the site of discovery and in interpreting the circumstances of death. Our review serves as a guide for the examination of animal-altered human remains and their found state by providing ecological backgrounds on various vertebrate species. In addition, this study provides an overview of the current state of research in the field of animal scavenging in forensics.Animal scavenging by vertebrates can significantly alter human bodies and their deposition site. For instance, vertebrate animals can cause postmortem modification to a body, alter perimortem trauma, influence decomposition rates, disarticulate and scatter body parts or evidence, and affect the identification of the deceased. Animal scavenging is a relatively common occurrence in forensic investigations. Even so, studies on the subject are scattered and rare, with most focussing on geographical areas outside of Europe. For that reason, we intend to collate the literature to provide an account of forensically relevant vertebrate scavengers in Europe, their impacts on human remains, and their implications for forensic investigations. Here, we provide an overview of forensic aspects where the knowledge of animal scavenging is crucial, as well as an account of potential scavengers of human remains in Europe and their typical alterations to soft tissue and, in particular, to bones. In addition, we are the first to provide a guide for forensic practitioners to identify the presence of vertebrate scavenging and subsequently inform outdoor search strategies for affected human remains.

Balancing litterfall and decomposition in cacao agroforestry systems

Backgrounds and aimsLitter protects the underlying soil, depending on litterfall and decomposition, but dynamics of the standing litter stock in agroforestry systems remain poorly understood. We aimed to unravel effects of litter quality, temporal patterns, microclimate, and a possible home-field advantage (HFA) on standing litter dynamics across a land-use gradient.MethodsWe quantified litterfall, the standing litter stock, and microclimate during a year in (remnant) forest, cacao-based simple and complex agroforestry, cacao monocultures, and annual crops in a cacao producing area in Indonesia. We conducted a reciprocal litter transfer experiment, and tested decomposition rates of pruning residues. Standing litter stocks during the year were estimated from monthly litterfall and decomposition rates.ResultsVariation in litter quality influenced decomposition rates more strongly than variation in microclimate or HFA. Lower litter quality in complex agroforestry and in the cacao monoculture decreased the decay rate compared to simple agroforestry systems; mean litter residence time was over a year. Mixing high- and low-quality material in pruning residues modified the decomposition rate, soil C and N changes, offering options for targeted management of soil protection and nutrient release.ConclusionsThe seasonal patterns of litterfall and relatively slow decomposition rates supported permanence of the litter layer in all cacao production systems, protecting the underlying soil.

Phylogenetic organization in the assimilation of chemically distinct substrates by soil bacteria.

Soils are among the most biodiverse habitats on earth and while the species composition of microbial communities can influence decomposition rates and pathways, the functional significance of many microbial species and phylogenetic groups remains unknown. If bacteria exhibit phylogenetic organization in their function, this could enable ecologically meaningful classification of bacterial clades. Here, we show non-random phylogenetic organization in the rates of relative carbon assimilation for both rapidly mineralized substrates (amino acids and glucose) assimilated by many microbial taxa and slowly mineralized substrates (lipids and cellulose) assimilated by relatively few microbial taxa. When mapped onto bacterial phylogeny using ancestral character estimation this phylogenetic organization enabled the identification of clades involved in the decomposition of specific soil organic matter substrates. Phylogenetic organization in substrate assimilation could provide a basis for predicting the functional attributes of uncharacterized microbial taxa and understanding the significance of microbial community composition for soil organic matter decomposition.

Effects of gamma irradiation on instream leaf litter decomposition

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

Assessing the Effect of Rubber (Hevea brasiliensis (Willd. ex A. Juss.) Muell. Arg.) Leaf Chemical Composition on Some Soil Properties of Differently Aged Rubber Tree Plantations

Leaf litter plays a major role in carbon and nutrient cycling, as well as in fueling food webs. The chemical composition of a leaf may directly and indirectly influence decomposition rates by influencing rates of biological reactions and by influencing the accumulation of soil organic carbon content, respectively. This study aimed to assess the impact of the chemical composition of rubber (Hevea brasiliensis (Willd. ex A. Juss.) Muell. Arg.) leaves on various soil properties of different ages of rubber (4–5, 11–12, and 22–23 year-old). Synchrotron-based Fourier transform infrared microspectroscopy (Sr-FTIR) was utilized for analyzing the chemical composition of plant leaves. The Sr-FTIR bands illustrated that the epidermis of rubber leaves from 4–5-year-old trees was found to contain a high quantity of polysaccharides while mesophyll from 22–23-year-old trees had a large number of polysaccharides. The change in soil properties in the older rubber plantation could be attributed to its chemical composition. The change in soil properties across all tree ages, i.e., increased litter and organic carbon content, was a relatively strong driver of soil biota evolution. The aliphatic of C-H in the leaves showed high correlation with soil organic carbon (SOC) and permanganate-oxidizable C (POXC) from 22–23 year-old trees. This study shows the differences in the organic chemical composition of leaves that are consequential to soil organic carbon.

Decomposition of Organic Matter in Caves

Decomposition of organic matter is a process, which includes mostly physical breakdown and biochemical transformation of complex organic molecules into simpler organic and inorganic molecules. The decomposition of organic matter is an important contributor to ecosystem respiration, which together with photosynthesis controls the net carbon emission from ecosystems. Subterranean ecosystems extend all over the subsurface of our planet. These lack light and consequently photosynthetic activity, and understanding the drivers that control the dynamics of the decomposition processes in the deep subterranean spaces is important. This is because they might differ from surface due to factors as low species diversity and abundance, low microbial biomass, nutrient poor conditions, less pronounced variation of temperature, and higher humidity inside cave. Here, we review the existing studies of organic matter decomposition in caves. Decomposition rates are known from only nine caves representing four biogeographic regions, including Europe, North and South America. Most of the studies were performed in the aquatic compartment of caves. The decay of nine different organic substrates were used and the incubation time varied from 36 to 439 days. From a cave located in Australia the mass loss of leaf material from three plant species were investigated after 90 days incubation in the terrestrial compartment of the cave. Based on these observations, litter quality seems to be an important driver of decomposition in caves and invertebrates have a stimulating effect on the decomposition within individual cave zones. The degree of connection to the surface do also influence decomposition rate inside the cave. The lack of standard data among the studies is currently the major impediment to evaluate how differently the process proceeds in the underground compared to the surface, and to clearly identify the main drivers of decomposition in caves across biomes. Improving our understanding of organic matter decomposition dynamics in caves across biomes will require standardization of protocols and evaluation of the process over time, and a better comprehension on how decomposition changes over latitudinal, altitudinal and depth gradients.

Leaf trait variation and decomposition in short-rotation woody biomass crops under agroforestry management

The integration of trees into agricultural landscapes has a strong influence on plant-soil interactions, with major impacts on rates of nutrient cycling across multiple spatial scales. Shifts in abiotic conditions owing to agroforestry practices, such as changes in soil nutrient and microclimatic conditions, are commonly identified as primary mechanisms for these changes. Yet agroforestry systems are also likely to influence litter decomposition rates through their influence on morphological and chemical traits of crop leaves and residues. However, explicit evaluations of how agroforestry management results in intraspecific leaf trait plasticity, and how this variation then links with litter decomposition, remain sparse. Using a 30-year-old agroforestry system intercropped with short-rotation willow (Salix dasyclados), we i) examined the effects of agroforestry management (i.e. N2-fixing trees vs. non N2-fixing trees vs. monoculture) and distance from tree row on key crop (willow) leaf morphological (i.e. leaf area, specific-leaf area [SLA]) and chemical (leaf carbon (C) and nitrogen (N) concentration) traits, and then assessed ii) how this intraspecific leaf trait variability influenced decomposition rates. Willow leaves within agroforestry treatments exhibited significantly greater leaf area (p = 0.01), SLA (p = 0.002), and leaf N (p = 0.001) than willow leaves in monoculture. Following a 56-day incubation, willow leaves from agroforestry treatments did not decompose more quickly than those in the monoculture. Our results indicate high intraspecific variation in willow leaf traits owing to agroforestry management. However, intraspecific variation in willow leaf traits did not correspond to statistically significant differences in decomposition rates. We show that variation in willow traits near tree rows in agroforestry systems translates into limited variability in agroecosystems processes such as litter decomposition (as compared to monoculture arrangements). Our results have implications for optimal nutrient management in agroforestry systems.

Detrital traits affect substitutability of a range‐expanding foundation species across latitude

Climate‐driven range shifts of foundation species could alter ecosystem processes and community composition by providing different resources than resident foundation species. Along the US Atlantic coast, the northward expanding foundation species, black mangrove Avicennia germinans, is replacing the dominant salt marsh foundation species, marsh cordgrass Spartina alterniflora. These species have distinct detrital attributes that ostensibly provide different resources to epifauna. We experimentally examined how detritus of these species affects decomposition and community composition in different habitat contexts at regional and local scales. First, we manipulated detritus identity (Avicennia, Spartina) at 13 sites across a 5° latitudinal gradient spanning mangrove, mixed marsh‐mangrove and salt marsh habitats. Across latitude, we found that Avicennia detritus decomposed 2–4 times faster than Spartina detritus, suggesting that detrital turnover will increase with mangrove expansion. Epifaunal abundance and richness increased 2–7 times from south to north (mangrove to salt marsh) and were equivalent between Avicennia and Spartina detritus except for crabs, a dominant taxonomic group that preferred Spartina detritus. Second, to examine the whether changing habitat context affected regional patterns, we manipulated detritus identity and surrounding habitat type (mangrove, salt marsh) at a single mixed site, also including inert mimics to separate structural and nutritional roles of detritus. Epifaunal richness was similar between the two detrital types, but crabs were 2–7 times more abundant in Spartina detritus due to its structural attributes. Surrounding habitat type did not influence decomposition rate or community patterns, which suggests that latitudinal influences, not surrounding habitat, drove the regional community patterns in the first experiment. Overall, mangrove expansion could alter epifaunal communities due to the lower structural value and faster turnover of mangrove detritus. As species shift with changing climate, understanding foundation species substitutability is critical to predict community change, but we must account for concomitant environmental changes that also modify communities.

Differential responses of litter decomposition to climate between wetland and upland ecosystems in China

In upland ecosystems, climate and initial litter quality are the two major factors influencing decomposition rates regionally and globally. Litters are exposed to a different decomposition environment in wetlands than in upland ecosystems, but the driving factors of litter decomposition in wetlands at a large scale are still unclear. We established a comprehensive database of litter decomposition in China, including 249 datasets and 27 pairs of sites, to examine the controlling factors of decomposition in both wetland and upland ecosystems at the regional scale. Both ecosystems showed similar climatic conditions, but the average litter decomposition potential was higher in wetlands than in upland ecosystems, as indicated by a higher initial K content and lower initial carbon content. The average decomposition rate in wetlands was almost 3 times higher than that in upland ecosystems. In both ecosystems, the decomposition rate increased with the mean annual temperature, mean annual precipitation, and initial N content. However, linear regressions of these variables with the decomposition rate indicated steeper slopes in wetlands than in upland ecosystems. The litter decomposition rate responded to climate and initial N content in both ecosystem types, but these responses were more rapid in wetlands than upland ecosystems. Wetland ecosystems should be given more attention when studying the responses of litter dynamics to future climate changes.

Investigation of the energy (biogas) production from co-digestion of organic waste materials

Biogas production rate was investigated from the co-digestion of 39 kg each of food waste, cow dung and water; 39 kg each of food waste, poultry droppings and water as well as 39 kg each of food waste, fruit waste and water in 43 litres plastic digester setup. Although organic waste mix ratios with higher moisture content can influence decomposition rate, HRT and biogas yield, 1:1:1 mix ratio was used in this investigation. The total rate of biogas produced from the co-digestion of food waste with poultry droppings and water (39 kg) in the ratio of 1:1:1 was 4120 g of raw biogas and 3700 g of purified biogas within with Hydraulic Retention Time 32 days, whereas, the co-digestion of food waste with cow dung and water (39 kg) in the same 1:1:1 ratio yielded a total raw biogas of 5830 g and 4920 g of purified biogas with HRT of 35 days. However, co-digestion of food waste with fruit waster and water (39 kg) in the same ratio yielded a total raw biogas of 5010 g and purified biogas 4330 g with HRT of 33 days. Raw biogas produced from each organic feedstock was channelled through a scrubbing unit comprising distilled water and Type B silica gel. After the raw biogas had passed through the distilled water stream, its pH dropped drastically from neutral range to ultra-acidic range (7-3.2), while it also had milky color and sour taste, indicating the presence of carbonic acid (H2CO3) as a result of carbon dioxide (content in the raw biogas) dissolution in the distilled water. Color of the Type B silica gel changed from crystal pink to crystal blue, indicating the absorption of water content in the biogas by silica gel particles. Organic waste is a renewable energy resource that can offset Nigeria’s increasing demand for energy if harnessed and processed into cooking gas and organic fertilizers before disposal, in which case can also prevent Green House Gas (GHG) emissions into the atmosphere.

UV-B radiation and shrub canopy effects on surface litter decomposition in a shrub-invaded dry grassland

Background & AimsWe assessed the joint role of shrub cover and UV-B on decomposition in a Sonoran Desert grassland. UV is considered an important driver of biogeochemistry in arid grasslands and shrub proliferation in these landscapes can alter both abiotic and biotic drivers of biogeochemistry. MethodsWe manipulated ambient solar UV-B exposure of Prosopis velutina leaf litter under and away from shrub canopies and assessed decomposition responses over 320 days. ResultsLeaf litter mass declined 40% during the first 50 days, but only an additional 10% during the remaining 270 days. Decomposition was slower under shrubs, where ground temperatures and total solar radiation were lower than locations away from shrubs. However, the presence/absence of UV-B radiation had no detectable influence on mass loss either under or away from shrubs. UV-B exposure decreased N immobilization suggesting UV-B photodegradation is facilitating microbial access to litter N. ConclusionsHigher decomposition of litter away from shrubs may reflect a combination of greater rates of thermal degradation and photodegradation. While UV-B did not directly influence decomposition rates, exposure may alter litter nutrient dynamics. Our study suggests landscape-scale decomposition could decline with increases in woody plant canopy cover owing to shrub-driven changes in microclimate.

Moisture absorption by plant residue in soil

Oil incorporated plant residues are an important source of carbon inputs and its decomposition defines magnitudes of many soil processes. While soil properties, especially soil moisture levels, influence decomposition rates, the moisture level of plant residue itself can differ from that of the surrounding soil due to the so called “sponge effect”-water absorption by plant residue from the surrounding soil. Our study explored whether water absorption by plant residue varies depending on soil moisture and matric potential levels; and how soil characteristics and characteristics of the plant residue itself affect the magnitude of this effect. We examined water retention of two types of plant residue materials, namely, corn and soybean leaves, in soil materials with three contrasting particle size distributions (PSD); and analyzed water distribution patterns in the soil adjacent to the residue using X-ray computed micro-tomography. The results demonstrated that the sponge effect was especially pronounced when soil moisture levels ranged from 0.15 to 0.40cm3cm−3 (~30–80% water filled pore space). The leaves were fully saturated with gravimetric water content levels exceeding 2.0gg−1 even when the soil moisture level was only 0.15cm3cm−3. Subsequent increase in residue moisture level was achieved due to vertical swelling of residue and reached 3.0–4.0gg−1 at soil moisture levels >0.30cm3cm−3. The sponge effect was greater in the coarse textured soil materials with lower soil water retention than in the fine textured soil material with high water retention; it was greater in soybean than in corn, possibly due to greater porosity of soybean leaves. Our results indicate that plant residue fragments incorporated into soil likely create moisture microenvironments for microbial decomposers that differ from those of the surrounding soil; and which, in relatively dry soil, can be more beneficial for plant decomposition than what can be inferred from the information on moisture levels of the soil itself.

Fungal communities influence decomposition rates of plant litter from two dominant tree species

The home-field advantage hypothesis (HFA) predicts that plant litter decomposes faster than expected underneath the plant from which it originates. We tested this hypothesis in a decomposition experiment where litters were incubated reciprocally in neighbouring European beech and Norway spruce forests. We analysed fungal communities in the litter through DNA metabarcoding and evaluated the effect of mesofauna (mites and springtails) on litter mass loss by using different litter-bag mesh sizes. Accounting for general differences in decomposition between litter and forest types, we found a significant home field advantage of 24%. Litter decomposed faster in the beech forest but spruce litter decomposed faster than beech litter. Fungal communities showed a clear dependency on both forest and litter type. Mesofauna did not affect litter mass loss rates or microbial species composition.

Effects of fire frequency on litter decomposition as mediated by changes to litter chemistry and soil environmental conditions.

Litter quality and soil environmental conditions are well-studied drivers influencing decomposition rates, but the role played by disturbance legacy, such as fire history, in mediating these drivers is not well understood. Fire history may impact decomposition directly, through changes in soil conditions that impact microbial function, or indirectly, through shifts in plant community composition and litter chemistry. Here, we compared early-stage decomposition rates across longleaf pine forest blocks managed with varying fire frequencies (annual burns, triennial burns, fire-suppression). Using a reciprocal transplant design, we examined how litter chemistry and soil characteristics independently and jointly influenced litter decomposition. We found that both litter chemistry and soil environmental conditions influenced decomposition rates, but only the former was affected by historical fire frequency. Litter from annually burned sites had higher nitrogen content than litter from triennially burned and fire suppression sites, but this was correlated with only a modest increase in decomposition rates. Soil environmental conditions had a larger impact on decomposition than litter chemistry. Across the landscape, decomposition differed more along soil moisture gradients than across fire management regimes. These findings suggest that fire frequency has a limited effect on litter decomposition in this ecosystem, and encourage extending current decomposition frameworks into disturbed systems. However, litter from different species lost different masses due to fire, suggesting that fire may impact decomposition through the preferential combustion of some litter types. Overall, our findings also emphasize the important role of spatial variability in soil environmental conditions, which may be tied to fire frequency across large spatial scales, in driving decomposition rates in this system.

Seasonal and inter‐annual variability in litter decomposition and nitrogen availability in a mid‐Appalachian watershed

AbstractThe role that microclimates play on soil decomposition is poorly understood. Though litter decomposition is controlled by climate and substrate quality at coarse spatial scales, at the watershed scale, microclimates mediated by forest structure and landscape position can influence decomposition rates and in turn affect nitrogen cycling. To evaluate the effects of landscape position and vegetation heterogeneity on decomposition, we employed a two‐year litterbag study (2011–2013) using yellow birch leaf litter across the Weimer Run watershed, a cool, humid watershed located near Davis, West Virginia. From our results, we created a spatially explicit empirical model that we tested against both a single‐pool and three‐pool decomposition model, each based on climate and derived from the Long‐Term Intersite Decomposition Experiment Team. Initial litter decomposition varied by elevation, with greater rates of decomposition at locations lower in the watershed. Decomposition rates differed by elevation, except during the first winter of the study. No differences in decomposition rates were seen among elevation levels when snowfall was below average for the first winter (2011–2012). During the second winter (2012–2013), elevation levels showed separation in decomposition rates, with higher elevations exhibiting lower decomposition rate. This suggests important controls on decomposition exerted by the presence or absence of snow, inter‐annual climate variability, and the interaction of both with topography. Our empirical model showed greater rates of decomposition during early stages of decomposition (&lt;12 months), but converged with the three‐pool decomposition model after 20 months. Plant available nitrogen differed by vegetation cover, largely driven by greater availability of nitrate (NO3−) beneath areas of canopy closure in the forest. Controls on decomposition and nitrogen cycling within the Weimer Run watershed vary spatially by elevation and vegetation cover and are subject to complex interactions and differ from standard models of decomposition. The effect of the inter‐annual variance of snow depth on litter decomposition is of note and an important consideration moving forward. Climate‐based models of decomposition greatly underestimate initial rates of decomposition, potentially leading to under‐accounting and compounded uncertainty.

Suppression of savanna ants alters invertebrate composition and influences key ecosystem processes.

In almost every ecosystem, ants (Hymenoptera: Formicidae) are the dominant terrestrial invertebrate group. Their functional value was highlighted by Wilson (1987) who famously declared that invertebrates are the "little things that run the world." However, while it is generally accepted that ants fulfil important functions, few studies have tested these assumptions and demonstrated what happens in their absence. We report on a novel large-scale field experiment in undisturbed savanna habitat where we examined how ants influence the abundance of other invertebrate taxa in the system, and affect the key processes of decomposition and herbivory. Our experiment demonstrated that ants suppressed the abundance and activity of beetles, millipedes, and termites, and also influenced decomposition rates and levels of herbivory. Our study is the first to show that top-down control of termites by ants can have important ecosystem consequences. Further studies are needed to elucidate the effects ant communities have on other aspects of the ecosystem (e.g., soils, nutrient cycling, the microbial community) and how their relative importance for ecosystem function varies among ecosystem types (e.g., savanna vs. forest).

The decomposition rate of non-stem components of coarse woody debris (CWD) in European boreal forests mainly depends on site moisture and tree species

The decomposition rate of CWD is a key missing link for a quantitative understanding of forest ecosystem functioning. We examined factors influencing decomposition rates of bark, roots and branches from aspen (Populus tremula), birch (Betula pendula, B. pubescens), fir (Abies sibirica), spruce (Picea abies, P. obovata), Scots pine (Pinus sylvestris) and Siberian pine (Pinus sibirica) CWD in three primeval European boreal forests. The chronosequence approach with estimates of single exponential decomposition rate (k) based on calculation of mass loss was used. The k of non-stem parts increased in the order: branches (0.006 year−1 for P. sibirica and 0.020 year−1 for other species), roots in poorly drained sites (0.025 year−1), roots in well-drained sites (0.034 year−1) and bark (0.110 and 0.138 year−1 and 0.147 and 0.255 year−1 under poorly and well-drained conditions and from 1 to 3 m and >3 m above the root collar, respectively). Our results predict that the rate of decomposition of whole CWD pieces in European boreal forests is a function of vegetation zone, site conditions, tree species and size.

Decomposition drives convergence of forest litter nutrient stoichiometry following phosphorus addition

Nutrient levels in decomposing detritus and soil can influence decomposition rates and detrital nutrient dynamics in differing ways among various detrital components of forests. We assessed whether increased phosphorus (P) levels in litter and soil influenced decomposition rates and litter nutrient dynamics of foliage, fine roots, and twigs in nitrogen (N)-rich Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) forests in the Oregon Coast Range. We decomposed fresh foliage, fine root, and twig litter from Douglas-fir seedlings at three sites for two years. Half of the seedlings and half of the plots at each of the sites were fertilized with P resulting in a factorial design with the following treatments: control (no P fertilization), plant P (P-fertilized litter), soil P (P-fertilized soil), and plant P × soil P. Soil P fertilization slightly decreased foliage decomposition rates. Fertilization of seedlings increased litter P concentrations by an average of 250 % relative to controls, but did not alter litter decomposition rates. Litter fertilized with P mineralized P rapidly and early in the decomposition process compared to N. Litter P concentrations decreased over the 2 years for all treatments, whereas N concentrations increased. Decomposition rates and loss of N and P were strongly related to initial litter chemistry. Despite different initial litter C:N:P ratios in P fertilized seedlings, ratios of C:N, C:P and N:P converged to similar values across treatments within a given litter type over 2 years. We conclude that litter P concentrations and to some extent soil P may influence litter nutrient dynamics during decomposition, resulting in a convergence of element ratios that reflect the balance of substrate decomposition and microbial nutrient stoichiometry.