The role of microarthropods and nematodes in decomposition in a semi-arid ecosystem

Summary We sampled the soil microarthropod community monthly in the oak-mesquite sand hill ecosystem. Small fungiphagous prostigmated mites (pyemotids, lordalychids and tarsonemids) that dominated the soil fauna in winter were replaced by large predaceous mites (rhodacarids and laelapids) in summer and autumn.We compared organic matter loss and microarthropod and nematode populations in shinnery oak (Quercus harvardii) using insecticide and untreated litter in fiberglass litterbags.Microarthropods extracted from litterbags showed a seasonal pattern similar to the soil cores except that collembolans and psocopterans were abundant in the litter and not in the soil cores. Numbers of free living nematodes were consistently greater than from untreated litter. The ratio of non-stylet to stylet bearing nematodes extracted from litter decreased from 4:1 in one month bags to 0.8:1.0 in the one year bags. Laboratory experiments showed that rhodacarid mites fed voraciously on nematodes.Untreated litter exhibited higher rates of organic matter loss than the insecticide treated litter; 20% and 35% respectively.We suggest that the abundant mesostigmatid mites prey on free living nematodes and that eliminating the predators allows the nematodes to overgraze the fungi and bacteria. The soil modifies the microclimate in buried litter allowing for higher biological activity, hence higher rates of decomposition.     

Succession of fungi and fauna during decomposition of needles in a small area of Scots pine litter

During micromorphological investigations on Scots pine litter, several decomposition stages have been recognized on fallen pine needles, each being associated with the activity of animal and microbial organisms, both. To well-known fungal successions that have been so far described by mycologists we must add succession of animal groups such as nematodes, amoebae, enchytraeids, sciarid larvae, oribatid mites and earthworms. A bacterial development was observed in the L₂ layer, following penetration by microfauna (nematodes, amoebae). After that stage pine needles were actively tunnelled by enchytraeids, sciarid larvae and oribatid mites and at the same time were nibbled on by epigeic earthworms (L₂ and F₁ layers). When the fine root system of pine developed through accumulated old needles (F₁ layer), mycorrhizal fungi penetrated the needles and seemed to impede any further bacterial development. Pine foliar tissues were progressively incorporated into the fecal material of earthworms and other members of the soil fauna. A more realistic scheme was suggested for plant litter decomposition in moder humus.     

Oribatid mite (Acari: Oribatida) contribution to decomposition dynamic of leaf litter in primary forest, second growth, and polyculture in the Central Amazon.

We studied the contribution of oribatid mites in the dynamics of litter decomposition in an experiment using litterbags of three different mesh sizes (20 microns, 250 microns, and 1 cm). The experiment was carried out at a primary forest (FLO), a secondary forest (SEC), and at two polyculture systems (POA and POC). We compared the weight loss of the leaves of Vismia guianensis and the changes of the oribatid mite species community. We processed the samples after 26, 58, 111, 174, 278, and 350 days from the beginning of the experiment by using the Berlese-Tullgren to extract the animals. We hypothesized that: 1. the abundance and diversity of oribatid mites would exert an influence in the decomposition process; 2. there would be a successional changing of the species during decomposition; and 3. there would be differences in the colonization of species in relation to the mesh size of the litterbags. A total of 95 species of oribatid mites was found. The biomass data was the first registered for the Amazon region. The great dominance of oribatid mites did not exert an influence in the decomposition process. There was not a successional changing of the species during the course of the decomposition process, unlike those shown by results obtained in the temperate forest, because we found neither early colonizers nor species that prefer advanced decomposition stages. The oribatid mite community, which developed in the litterbags under tropical conditions, was atypical of the normal stages of leaf litter breakdown and decomposition. There were differences in the colonization of species in relation to the mesh size of the litterbags. These differences were very closely related to the specific habits and habitat of the dominant species.     

西双版纳热带雨林凋落叶分解的生态过程.Ⅲ.酶活性动态

 该文通过野外试验和室内模拟相结合,系统研究了西双版纳热带雨林生态系统混合凋落叶分解过程中的酶活性动态。野外试验采用网袋法（1 mm和100μm网眼）限制土壤动物的出入,室内模拟试验采用灭菌-接种法控制生物组成,从而研究不同生物组成或食物链结构条件下,凋落叶分解过程中的酶活性变化,以及酶活性与分解进程之间的动态响应。研究结果表明,转化酶和淀粉酶在有机残体的最初分解阶段发挥重要作用,参与易分解成分的转化和分解,这些酶与凋落叶分解进程之间存在显著的负相关性,且参与分解的生物组成越简单（缩短食物链）,这些酶活性越高,是微生物在分解初期对底物加以利用的关键酶类; Cx酶、 β-葡萄糖苷酶、木聚糖酶活性均在分解中期达到高峰,多酚氧化酶在分解后期迅速上升,对凋落叶中、后期木质素的分解起到关键性的作用,这些酶与凋落叶分解进程之间存在显著的正相关性,且参与分解的生物组成越复杂（延长食物链）,这些酶活性越高,是微生物在分解后期对底物进一步利用的关键酶类;与C循环有关的酶类都可以作为有机物质分解进程的重要指标,与分解进程之间存在一定的动态响应,有机残体的分解过程实质上是一个酶解过程。     

Regional factors rather than forest type drive the community structure of soil living oribatid mites (Acari, Oribatida)

Most European forests are managed by humans. However, the manner and intensity of management vary. While the effect of forest management on above-ground communities has been investigated in detail, effects on the below-ground fauna remain poorly understood. Oribatid mites are abundant microarthropods in forest soil and important decomposers in terrestrial ecosystems. Here, we investigated the effect of four forest types (i.e., managed coniferous forests; 30 and 70 years old managed beech forests; natural beech forests) on the density, diversity and community structure of oribatid mites (Acari). The study was replicated at three regions in Germany: the Swabian Alb, the Hainich and the Schorfheide. To relate changes in oribatid mite community structure to environmental factors, litter mass, pH, C and N content of litter, fine roots and C content of soil were measured. Density of oribatid mites was highest in the coniferous forests and decreased in the order 30 years old, 70 years old, and natural beech forests. Mass of the litter layer and density of oribatid mites were strongly correlated indicating that the litter layer is an important factor regulating oribatid mite densities. Diversity of oribatid mites was little affected by forest type indicating that they harbor similar numbers of niches. Species composition differed between the forest types, suggesting different types of niches. The community structure of oribatid mites differed more strongly between the three regions than between the forest types indicating that regional factors are more important than effects associated with forest type.     

Secondary succession, soil formation and development of a diverse community of oribatids and saprophagous soil macro-invertebrates

Investigations into different stages of secondary succession (from a wheat field to a beechwood on Threstone; Northern Germany) demonstrated the formation of a carbon rich top soil in later successional stages. Parallel to changes in plant species and soil formation, there were also changes in species composition and diversity of saprophagous macro-invertebrates (Lumbricidae, Diplopoda, Isopoda) and oribatid mites (Acari: Oribatida). Diversity of diplopod and isopod species increased after cessation of cultivation, but in a late successional stage (ca 50 y-old fallow, ash-dominated wood) species number of diplopods and isopods declined strongly. In comparison with the other soil invertebrate groups, species composition of earthworms among the sites was more similar. Accumulation of soil C was assumed to be related to wood formation and occurrence of woody debris and recalcitrant leaf litter of beech trees. Incorporation of recalcitrant litter materials by earthworm species living in the upper mineral soil presumably contributed significantly to accumulation of soil C. Accumulation of soil C was accompanied by the development of an oribatid mite community rich in species. In early successional stages oribatids predominantly colonized the litter layer, while most oribatid mites of the beechwood inhabited the upper mineral soil. Maximum diversity of oribatid mites in the beechwood is assumed to be related to instability of the mineral soil caused by earthworm activity. Changes in species composition and diversity are discussed considering succession theory. Even soil invertebrates of similar trophic groups appear to respond very differently to successional changes. It is concluded that conservation strategies to maintain high diversity of soil invertebrates are most likely to be successful if a wide range of habitats of different successional stages is included.     

The effect of litter type and macrofauna community on litter decomposition and organic matter accumulation in post-mining sites

Field microcosms consisting of mineral soil (spoil substrate) and two types of litter taken either from an unreclaimed site with spontaneously developed vegetation (mostly Salix caprea) or from an alder plantation (a mixture of Alnus glutinosa and A. incana) were exposed in spontaneously developed or reclaimed sites at a post-mining heap near Sokolov (Czech Republic) for one year. The litter types differed remarkably in C:N ratio which was 29 for spontaneous litter and 14 for alder litter. The two microcosm types were either accessible or not accessible to soil macrofauna. The effect of macrofauna exclusion on soil mixing was complex and depended on litter quality and the site that determined soil fauna composition. In reclaimed sites where macrofauna was dominated by saprophags, mainly earthworms, the macrofauna access increased soil mixing. In sites where predators dominated, the macrofauna exclusion probably suppressed fragmentation and mixing activity of the mesofauna.     

Tree litter functional diversity and nitrogen concentration enhance litter decomposition via changes in earthworm communities

Biodiversity is a major driver of numerous ecosystem functions. However, consequences of changes in forest biodiversity remain difficult to predict because of limited knowledge about how tree diversity influences ecosystem functions. Litter decomposition is a key process affecting nutrient cycling, productivity, and carbon storage and can be influenced by plant biodiversity. Leaf litter species composition, environmental conditions, and the detritivore community are main components of the decomposition process, but their complex interactions are poorly understood. In this study, we tested the effect of tree functional diversity (FD) on litter decomposition in a field experiment manipulating tree diversity and partitioned the effects of litter physiochemical diversity and the detritivore community. We used litterbags with different mesh sizes to separate the effects of microorganisms and microfauna, mesofauna, and macrofauna and monitored soil fauna using pitfall traps and earthworm extractions. We hypothesized that higher tree litter FD accelerates litter decomposition due to the availability of complementary food components and higher activity of detritivores. Although we did not find direct effects of tree FD on litter decomposition, we identified key litter traits and macrodetritivores that explained part of the process. Litter mass loss was found to decrease with an increase in leaf litter carbon:nitrogen ratio. Moreover, litter mass loss increased with an increasing density of epigeic earthworms, with most pronounced effects in litterbags with a smaller mesh size, indicating indirect effects. Higher litter FD and litter nutrient content were found to increase the density of surface‐dwelling macrofauna and epigeic earthworm biomass. Based on structural equation modeling, we conclude that tree FD has a weak positive effect on soil surface litter decomposition by increasing the density of epigeic earthworms and that litter nitrogen‐related traits play a central role in tree composition effects on soil fauna and decomposition.     

Biodiversity of soil macrofauna in the New Forest: a benchmark study across a national park landscape

The New Forest National Park is a hotspot for biodiversity in the UK. A long history of grazing by ponies in the New Forest landscape has created a diverse mosaic of habitats that are of international significance. We investigated patterns of species diversity and composition across the New Forest landscape by sampling soil, leaf litter and ground macrofauna from woodland, grassland and heathland plots across the entire landscape. We used a spatially replicated design of hand sorted soil pits, Winkler extraction of leaf litter, and pitfall traps. We concentrated on diversity patterns of the following target groups: Coleoptera, Formicidae, Isopoda, Chilopoda, Diplopoda, Opiliones and Lumbricidae. The most striking difference in species assemblages is between wooded and open areas. Woodlands are the most diverse habitats and have a distinct assemblage, largely due to those leaf litter invertebrate species which are only present under a closed canopy. Open areas are less diverse, with diversity particularly low in the wet grasslands. However, the open areas do have a distinct fauna, especially in the wet and dry heaths which are home to a number of rare species, particularly of Formicidae. We discuss the potential conservation problems facing the New Forest and how these might affect soil macrofauna biodiversity in the future and conclude that climate change; over-grazing; and land use changes represent the largest threats. Although a relatively stable landscape which benefits from protection under UK law, changes in grazing intensity or management practices in the New Forest, particularly for some of the habitats of European importance (e.g. wet heathlands), could negatively affect soil macrofauna biodiversity. Climate change may also exacerbate biodiversity decline as a result of increased grazing intensity or changes in management.     

Effects of topsoil removal,seed transfer with plant material and moderate grazing on restoration of riparian fen grasslands

Question: How do moderate grazing, topsoil removal and hay transfer affect species diversity and abundance on a eutrophic fen grassland site? Location: Northern Germany. Method: A three-factorial field experiment with the factors grazing, topsoil removal and hay transfer of diaspore-rich material was established in 2001. Soil nutrients and seed bank were analysed at the beginning of the experiment, species composition and vegetation development was monitored for four years (2002–2005). Results: Topsoil removal had a significant effect on the abundance of different plant species groups: resident vegetation of agricultural grasslands was suppressed, while clonal reed species were facilitated in recolonising the area. The establishment of regionally rare and endangered species of nutrient-poor fens and wet meadows introduced with hay was achieved mainly on plots with topsoil removal, with the exception of Rhinan-thus angustifolius, which also established on plots with intact topsoil. Effects of grazing after four years of experiments were of minor influence on species composition. Conclusion: The establishment of target plant species of nutrient-poor fens is most successful when both an adequate number of viable diaspores and suitable sites for germination and establishment are available. In our experiment this was achieved by the combination of topsoil removal and hay transfer. We recommend this combination, together with continuous management (grazing/cutting), for further restoration in fen grasslands.     

Differences in litter mass change mite assemblage structure on a deciduous forest floor

Few mechanisms that determine the assemblage structure of mites have been identified. Whilst the relative abundance of soil fauna is known to change with humus form, the degree to which the quantity of litter inputs play a part in these changes has not been investigated. We tested the response of oribatid and mesostigmatid mites in litter and soil layers to increasing levels of birch Betula pubescens litter to test whether litter mass could affect the mite assemblage. Six litter treatments (1, 2, 4, 8 and 12×natural litter mass and complete litter removal) were established in November 2004 and the soil and litter communities sampled in October 2005. Species composition of oribatids was distinct for the soil and litter. There was no apparent effect of increasing litter mass on the soil mite assemblage. In the litter layer, the number of oribatids g⁻¹ of litter showed a strong negative relationship with increasing litter mass whilst the number of mesostigmatids g⁻¹ of litter was unresponsive to litter mass. Hence, the relative abundance of these two groups altered with increasing litter mass. The response of the oribatid groups Oppiidae and Poronota followed this negative relationship with litter mass but Phthiracaridae appeared less affected. Consequently, there was a subtle shift in the relative abundance of these groups with increasing litter mass. Our results demonstrate that oribatids as a whole and within groups respond in a predictable manner to increases in litter mass whilst mesostigmatids are unresponsive. Whilst there are undoubtedly biological and physical aspects that vary with litter mass, litter mass itself, is able to explain some patterns in the assemblage of oribatid mites.     

The effect of herbivore faeces on the edaphic mite community: implications for tapeworm transmission

Oribatid mites may be of epidemiological and medical importance because several species have been shown to serve as intermediate hosts for anoplocephalid tapeworms of wild and domestic animals. Despite their economic and conservation significance, relatively few studies examined factors influencing the effective number of oribatid mites that can serve as intermediate hosts. We examined variation in the structure of the edaphic arthropod community in functionally different territory parts of the Alpine marmot (Marmota marmota latirostris), a known definitive host of a prevalent anoplocephalid tapeworm, Ctenotaenia marmotae. We used a field experiment to test whether the abundance of oribatid mites in marmot pastures is affected by the presence of fresh herbivore faeces. We found that the abundance of soil and litter dwelling oribatid mites in marmot pastures did not change shortly after faeces addition. In contrast, numbers of other predominant soil–litter and phoretic microarthropods increased after faeces addition. The abundance of the two predominant phoretic mites colonizing the faeces was inversely related to the abundance of oribatid mites. In contrast, the abundance of a ubiquitous soil–litter mesostigmatid mite was a positive function of oribatid numbers. Although absolute numbers of oribatid mites did not change after faeces addition, our study suggests that, depending on soil quality or type, the probability of tapeworm egg ingestion by oribatid mites can be reduced due to increased interspecific prey-predatory and trophic interactions. Latrine site selection in Alpine marmots is consistent with a reduced probability of tapeworm transmission by oribatids.     

Mixed leaf litter effects on decomposition rates and soil microarthropod communities in an oak–pine stand in Japan

Rates of decomposition, and soil faunal abundance and diversity associated with single-species and mixed-species litters were studied in a litter bag experiment in an oak–pine forest. We used two canopy species of leaf litter, pine and oak, and one shrub species, Sasa, and compared decomposition rates, and soil microarthropod abundance and community structure of oribatid mites in the litter bags. Mass loss of single species decreased in the order: oak > pine > Sasa. While the total mass loss rates of mixed litter were intermediate between those of the constituent species, enhancement of mass loss from the three-species mixture and from mixed slow-decomposing litters (pine and Sasa) was observed. Faunal abundance in litter bags was higher in mixed-species litter than in those with single-species litter, and species richness of oribatid mites was also higher in the three-species mixed litter. Faunal abundance in single-species litter bags was not correlated with mass loss, although enhancement of mass loss in mixed litter bags corresponded with higher microarthropod abundance. Habitat heterogeneity in mixed litter bags seemed to be responsible for the more abundant soil microarthropod community.     

Red oak litter promotes a microarthropod functional group that accelerates its decomposition

The contribution of microarthropod activity to litter decomposition varies widely but can be substantial. Oribatid mites are the most diverse and abundant of the microarthropod groups in forest litter. This experiment was designed to examine the effect of litter type and complexity on the diversity and species composition of oribatid mites, and to test whether alterations in species composition due to litter type affected litter decomposition. In an array of plots on a mixed-hardwood site in the mountains of North Carolina, I exposed microarthropod assemblages to a range of litter types: yellow birch, sugar maple, red oak and two mixed litters. Over several years, the litter types selected oribatid mite assemblages of different species composition. By comparing the decomposition of consecutive cohorts of litter, it was possible to detect differences in decomposition accompanying the shifts in the assemblage. A comparison of the mass loss rates between the two litter cohorts over eighteen months reveals similar trajectories for four litter types. In the oak litter, however, the second cohort disappeared significantly faster than the first. In both years, the litters came from the same trees and were nearly identical in initial carbon and nitrogen contents. Since the response was specific to oak litter, it is unlikely that differences in environmental factors are responsible for the faster mass loss of oak. A significant increase of endophagous oribatid mites, those that burrow into plant material, in the second cohort of oak may account for its accelerated decomposition. The woody petioles and thick leaf-planes of oak leaves provide microhabitats for burrowing mites. Endophage activity can accelerate the litter decomposition both through direct comminution of leaf material and by facilitating microbial growth. Because of their low population growth rates, oribatid populations that are reduced by disturbance are slow to recover and by disrupting these non-resilient populations, disturbance may have long-term repercussions for decomposition. This revised version was published online in June 2006 with corrections to the Cover Date.     

Are tree trunks habitats or highways? A comparison of oribatid mite assemblages from hoop-pine bark and litter

Abstract Oribatid mites (Acari: Oribatida) are among the most diverse and abundant inhabitants of forest soil and litter, but also have species-rich assemblages on bark and in the canopies of trees. It is unclear whether the trunk of a tree acts simply as a 'highway' for movement of mites into and out of the canopy, or whether the trunk has a distinctive acarofauna. We compare oribatid assemblages from the trunk bark of hoop pine ( Araucaria cunninghamii ) with those from litter collected beneath the same trees. A 1.0 by 0.5 m area of bark was sampled from three trees at each of five sites using a knockdown insecticide. A 1-L sample of leaf litter was collected as close as possible to the base of each sampled tree. Mites were extracted using Tullgren funnels, identified to genus and morphospecies, and counted. Assemblages were almost 100% distinct, with only one oribatid morphospecies ( Pseudotocepheus sp.) collected from both litter and bark. Litter had a higher taxon richness than bark in total and per sample, but oribatids made up a greater percentage of the acarofauna in the bark samples. We had expected that the more consistent physical substrate of bark would be reflected in greater similarity of oribatid faunas on trunks than in litter; however, the opposite proved to be the case. We conclude that hoop-pine trunks are habitats rather than highways for oribatid mites. Based on the observed higher turnover among bark faunas, tree trunks may represent habitat islands whose colonisation by particular oribatid species is more stochastic than that of the more continuous 'sea' of litter.     

Decomposing logs increase oribatid mite assemblage diversity in mixedwood boreal forest

The removal of timber during harvesting substantially reduces important invertebrate habitat, most noticeably microhabitats associated with fallen trees. Oribatid mite diversity in downed woody material (DWM) using species-level data has not been well studied. We investigated the influence of decaying logs on the spatial distribution of oribatid mites on the forest floor at the sylviculture et aménagement forestiers écosystémique (SAFE) research station in the Abitibi region in NW Québec. In June 2006, six aspen logs were selected for study, and samples were taken at three distances for each log: directly on top of the log (ON), directly beside the log (ADJ) and at least one metre away from the log and any other fallen wood (AWAY). Samples ON logs consisted of a litter layer sample, an upper wood sample and an inner wood sample. Samples at the ADJ and AWAY distances consisted of litter samples and soil cores. The highest species richness was collected ON logs, and logs harboured a distinct oribatid species composition compared to nearby forest floor. There were species-specific changes in abundance with increasing distance away from DWM, which indicates an influence of DWM in structuring oribatid assemblages on the forest floor. Additionally, each layer (litter, wood and soil) exhibited a unique species composition and hosted a different diversity of oribatid mites. This study further highlights the importance of DWM to forest biodiversity by creating habitat for unique assemblages of oribatid mites.     

热带季节雨林凋落叶分解过程中的中小型土壤节肢动物的群落结构及动态

2000年5月-2001年4月,采用尼龙网袋法,以西双版纳热带季节雨林混合凋落叶作为分解基质,在3个季节雨林样地开展分解实验,对实验过程中分解袋内的中小型土壤节肢动物(meso—microarthropod)进行取样调查。根据所获数据探讨了中小型土壤节肢动物群落在分解过程中的结构和动态。结果显示：(1)在季节雨林凋落叶分解过程中,中小型土壤节肢动物群落组成始终以弹尾目和蜱螨目相对数量较高(均在30％以上),成为优势类群。(2)分解中期,土壤节肢动物群落多样性指数,类群、个体及重要类群的数量均处于整个分解过程中的较高水平,分解初期和后期相对较低,且波动性大,其中分解初期各多样性指标在波动过程中呈逐步增长趋势,而后期逐步降低,其变化过程受凋落叶数量和质量、林地降雨量变化的影响。土壤动物群落类群和个体相对密度(每克凋落叶干重的类群数和个体数)的变化可在一定程度上反映土壤动物与凋落物质量的动态关系。(3)不同样地间,土壤节肢动物群落结构及动态差异在分解前期不明显,而分解后期差异有所增加,但3样地凋落叶分解物质损失率没有明显差异。     

Dispersal patterns of oribatid mites across habitats and seasons

Oribatid mites are tiny arthropods that are common in all soils of the world; however, they also occur in microhabitats above the soil such as lichens, mosses, on the bark of trees and in suspended soils. For understanding oribatid mite community structure, it is important to know whether they are dispersal limited. The aim of this study was to investigate the importance of oribatid mite dispersal using Malaise traps to exclude sole passive wind-dispersal. Oribatid mite communities were collected over a 3-year period from five habitat types (coniferous forests, deciduous forests, mixed forests, meadows, bog/heathlands sites) and three seasons (spring, summer, autumn) in Sweden. Mites entered traps either by walking or by phoresy, i.e., by being attached to flying insects. We hypothesized (1) that oribatid mite communities in the traps differ between habitats, indicating habitat-limited dispersal, and (2) that oribatid mite communities differ among seasons suggesting that dispersal varies due to changing environmental conditions such as moisture or resource availability. The majority of the collected species were not typically soil-living species but rather from habitats such as trees, lichens and mosses (e.g., Carabodes labyrinthicus, Cymbaeremaeus cymba, Diapterobates humeralis and Phauloppia lucorum) indicating that walking into the traps or entering them via phoresy are of greater importance for aboveground than for soil-living species. Overall, oribatid mite communities collected in the traps likely originated from the surrounding local habitat suggesting that long distance dispersal of oribatid mites is scarce. Significant differences among seasons indicate higher dispersal during warm and dry periods of the year. Notably, 16 species of oribatid mites collected in our study were sampled for the first time in Sweden. This study also demonstrates that Malaise traps are a meaningful tool to investigate spatial and temporal patterns of oribatid mite communities.

     

Mass and temperature dependence of metabolic rate in litter and soil invertebrates

Metabolic scaling theory provides a framework for modeling the combined mass and temperature dependence of metabolic rate. The theory predicts that whole-organism metabolic rate should scale with body mass raised to the 3/4 power as a consequence of the physical characteristics of internal distribution networks. Metabolic rate is predicted to vary with absolute body temperature, T, according to the Boltzmann factor, e(-E/kT), where E is the apparent activation energy of biochemical reactions, 0.2-1.2 eV, and k is Boltzmann's constant. I evaluated those predictions, using a compilation of published data on the metabolic rates of litter- and soil-dwelling earthworms, isopods, oribatid mites, springtails, and spiders. Earthworms, oribatid mites, springtails, and spiders had mass-scaling exponents that were statistically indistinguishable from the expected value of 0.75. The scaling exponent for terrestrial isopods, 0.91, was significantly greater than expected. All taxa had apparent activation energies within the predicted range of 0.2-1.2 eV. Activation energies for isopods, oribatid mites, springtails, and spiders were not significantly different from the average expected value of 0.6 eV, while the activation energy for earthworms, 0.25 eV, was significantly lower than 0.6 eV. Updated equations for estimating metabolic rate from body mass and environmental temperature are given for investigations into the ecological energetics of litter and soil animals.     

Interacting effects of leaf litter species and macrofauna on decomposition in different litter environments

The leaf litter environment (single species versus mixed species), and interactions between litter diversity and macrofauna are thought to be important in influencing decomposition rates. However, the role of soil macrofauna in the breakdown of different species of leaf litter is poorly understood. In this study we examine the multiple biotic controls of decomposition – litter quality, soil macrofauna and litter environment and their interactions. The influence of soil macrofauna and litter environment on the decomposition of six deciduous tree species (Fraxinus excelsior L., Acer pseudoplatanus L., Acer campestre L., Corylus avellana L., Quercus robur L., Fagus sylvatica L.) was investigated in a temperate forest, Wytham Woods, Southern England. We used litterbags that selectively excluded macrofauna to assess the relative importance of macrofauna versus microbial, micro and mesofauna decomposition, and placed single species bags in either conspecific single species or mixed species litter environments. The study was designed to separate plant species composition effects on litter decomposition rates, allowing us to evaluate whether mixed species litter environments affect decomposition rates compared to single species litter environments, and if so whether the effects vary among litter species, over time, and with regard to the presence of soil macrofauna. All species had faster rates of decomposition when macrofauna were present, with 22–41% of the total mass loss attributed to macrofauna. Macrofauna were most important for easily decomposable species as soon as the leaves were placed on the ground, but were most important for recalcitrant species after nine months in the field. The mass loss rates did not differ between mixed and single species litter environments, indicating that observed differences between single species and mixed species litterbags in previous field studies are due to the direct contact of neighbouring species inside the litterbag rather than the litter environment in which they are placed.