Exotic Earthworms Research Articles

Disturbance intensity overwhelms propagule pressure and litter resource in controlling the success of Pontoscolex corethrurus invasion in the tropics

The mechanisms by which exotic earthworms invade new habitats are largely unknown. Previous research concluded that factors including habitat disturbance, propagule pressure and variation in the litter resource may significantly drive the establishment of exotic earthworms, however, these studies did not conduct manipulative experiments to compare the effects of these three factors. To fill this knowledge gap, we established a moderate disturbance experiment and a severe disturbance experiment in a tropical natural forest (Xishuangbanna, China) with the exotic earthworm Pontoscolex corethrurus. The former mesocosm experiment manipulated disturbance (no disturbance vs moderate disturbance) and propagule pressure as the independent factors, while the latter mesocosm experiment manipulated propagule pressure and litter resource (difference in quality and diversity) as the independent factors that affect the establishment of P. corethrurus. In the moderate disturbance experiment: disturbance and propagule pressure did not affect the final population size of P. corethrurus, i.e., populations in all treatments declined to the same size at the end of the experiment. In the severe disturbance experiment: the population size of P. corethrurus increased in all treatments, with larger population size observed under the treatments with higher propagule pressure; litter treatments with a higher C/N ratio slightly increased the population biomass. In conclusion, our results showed that disturbance (severe vs no or moderate disturbance) overwhelmed the effects of propagule pressure and litter resource on the establishment of P. corethrurus. We suggest that the protection of tropical natural forests from severe disturbance, e.g., slash-and-burn deforestation, is the key means to prevent earthworm invasion.

Interactive Effects of White-Tailed Deer, an Invasive Shrub, and Exotic Earthworms on Leaf Litter Decomposition

Herbivore overabundance and species invasions could alter decomposition rates in temperate forests, with consequent effects on carbon sequestration, nutrient retention, and other ecosystem processes. At local scales, herbivores, invasive plants, and soil macroinvertebrates can be important drivers of decomposition, but interactive effects among these different groups are unknown. We tested for the effects of white-tailed deer, Amur honeysuckle, and earthworm activity (manipulated via mesh exclusion) on litter decomposition rates and loss of litter nitrogen (N) in five hardwood forest sites in southwestern Ohio. Each site consisted of a 20 × 20-m deer exclosure paired with a deer access plot; honeysuckle was removed from half of each plot. Effects of earthworm activity were tested using paired litter boxes of fine mesh (0.25 mm; earthworms excluded) or coarse mesh (10 mm; earthworm access). Restriction of earthworm activity in fine mesh treatments slowed litter decomposition and increased retention of N in the litter layer compared to coarse mesh. Deer access interacted with mesh treatments, with faster decomposition occurring in deer access, coarse mesh treatments relative to others. Greater earthworm biomass in deer access plots relative to deer exclosure plots corresponded with more rapid litter decomposition. Honeysuckle presence did not affect litter decomposition, but did increase litter N retention. The interactions between deer and earthworm activity indicate that reductions in deer populations may slow litter decomposition rates, increasing complexity of habitat structure at the soil surface, which relates to habitat for plants and animals.

A comparison of composting and vermicomposting for the disposal of poultry waste

Context Poultry products, mostly meat and eggs, provide affordable quality foodstuffs to human populations in Nepal. However, the poultry industry’s by-products, such as litter and offal, also generate potential environmental and human health issues and need a sustainable method of management. Aims The present study compared the effectiveness of vermicomposting by using an exotic earthworm species Eisenia fetida, or effective microorganism-based (EM) composting, of poultry litters in the Terai region of Nepal. Methods Four types of poultry litter, namely, broiler cage litter (parent stock litter), broiler deep litter, commercial layer cage litter and layer deep litter, each combined with earthworms (vermicompost) or effective microorganisms, were subjected to decomposition in beds. A completely randomised design in a 4 × 2 factorial arrangement (poultry litters by Eisenia fetida or effective microorganism) with three replicates per treatment was applied. Key results Macronutrient concentrations, and reduction of the carbon:nitrogen ratio were significantly greater in vermicompost than EM compost. In addition, reduction of the carbon:nitrogen ratio was more significant following vermicomposting for broiler and layer cage litter than in other treatments. The highest initial concentration of N was found in layer cage litter (2.1%) and the lowest in layer deep litter (1.3%) and these increased to 1.5–3.4% and 1.7–1.8% in vermicompost and EM compost respectively. Available phosphorus increased by two- to three-fold in most vermicomposted poultry litters in comparison to initial poultry litters, and a two-fold increase in potassium was likewise achieved. Consistent with these results, worm biomass was significantly higher in layer cage litter and broiler cage litter than in deep litter. More cocoons were evident in layer cage litter, and lowest numbers of cocoon formation were observed in broiler deep litter. Conclusions This comparative study showed that vermicomposting is superior to EM composting for bioconversion of poultry litters into value-added compost. Implications With the adoption of this result, the poultry industry in Nepal could become more sustainable.

Seasonal variations in exotic earthworm populations in wheat fields of the Inland Pacific Northwest, U.S.A.

Through their manipulation of soil physical and chemical properties, earthworms have the potential to increase nutrient mineralization and benefit crop production. However, this effect is dependent on numerous factors including earthworm densities and ecological strategies. In addition to impacting density, soil environmental conditions may limit earthworm activity to specific times during the growing season, moderating their effects on nutrient availability and crop growth. The purpose of this study was to determine the active period of earthworms to better assess their potential impact on crop productivity in dryland wheat production systems in the Palouse region of northern Idaho and eastern Washington, U.S.A. Earthworm community density, age structure, diversity, and soil moisture and soil temperature were monitored over a 14-month (April 2014–June 2015) period in six dryland wheat fields. All earthworms collected were exotic species, with the endogeic species, Aporrectodea trapezoides being predominant at all sites (87% of all adults identified). Allolobophora chlorotica, Lumbricus terrestris and Aporrectodea tuberculata were collected at lower frequencies (1.8–6.4% of adults). Mean densities ranged from 14 to 75 individuals m−2, and populations transitioned to aestivation beginning in mid-June of both years. All earthworms were active (no aestivating individuals) on 56.9% of the sampling dates in 2014 and 71% of the days in 2015. A short active period and average densities at most sites of less than 100 individuals per m2 suggest that the impact of earthworms on crop growth may be limited in conventional, dryland agricultural fields of this region.

Invasive shrub cover and tree species composition influence exotic earthworms

Forest ecosystems are often invaded by multiple exotic species that, when combined, may amplify negative impacts on native biodiversity and ecosystem functioning. These patterns are often determined from plot-level experiments, but it is less clear how interactions among native and exotic species vary across landscapes. Amur honeysuckle (Lonicera maackii) is an invasive understory shrub in eastern forests, observed to reduce understory plant diversity and alter litter decomposition rates. Exotic earthworms may aid this process by increasing decomposition rates and nutrient fluxes in forest soils. We hypothesized that honeysuckle increases exotic earthworm density and biomass in forest soils by providing a preferred litter resource and beneficial abiotic conditions. We established 15 transects, each 100-m long, in a stratified random design across a 245-ha deciduous forest in southwestern Ohio, USA. We measured honeysuckle shrub cover and canopy tree cover along the entire transect, and sampled earthworms and standing litter biomass at intervals along each transect. We found little evidence for Amur honeysuckle effects on earthworm density but found a strong positive effect of honeysuckle cover on earthworm biomass. We also recorded an effect of species composition of canopy trees on earthworm density and biomass. Moreover, multivariate analyses indicated a shift of earthworm community composition along an oak-elm gradient of tree species composition. Standing litter biomass was lowest in areas of high earthworm biomass and in the forest interior. Our results demonstrate that landscape-level variation in tree species composition and honeysuckle invasion drive exotic earthworm density and biomass. Our findings suggest invasion of exotic shrubs may facilitate invasion by nonnative earthworms.

Invasive earthworm and soil litter response to the experimental removal of white-tailed deer and an invasive shrub.

Recent studies have shown that complex species interactions can regulate above- and belowground processes in terrestrial systems. Ungulate herbivory and invasive species are known to have strong effects on plant communities in some systems, but their impacts on soil biota and belowground processes are lesser known. Growing evidence suggests white-tailed deer (Odocoileus virginianus) and invasive plants facilitate increased abundance of exotic earthworms in temperate forests of the eastern United States. We conducted an experimental study that manipulated deer access and the presence of an invasive understory shrub in an eastern deciduous forest of southwestern Ohio, USA, from 2013 to 2017. Earthworm density and biomass, and standing litter biomass were measured in five paired deer access and exclosure plots, each with a split-plot removal of Amur honeysuckle (Lonicera maackii). Earthworm density declined in response to the experimental exclusion of deer, with earthworm density decreasing over time in the deer exclosure plots relative to deer access plots. Deer exclusion produced greater variation in earthworm species composition relative to access plots. Multivariate analyses indicated that larger earthworms in the genus Lumbricus were associated with deer exclosure plots, while smaller endogeic species were ubiquitous in both treatments. Standing litter biomass decreased over time in the deer-access plots. In contrast, honeysuckle removal had little effect on earthworm density and standing litter biomass. There was an interaction between deer and honeysuckle treatments on earthworm biomass, with honeysuckle removal reducing earthworm biomass when deer were excluded. Our results demonstrate strong effects of herbivores on invasive earthworms and ecosystem processes, but indicate a weaker influence of invasive shrubs. Further, our findings suggest that the effects of deer overabundance in forest ecosystems are potentially reversible with long-term intervention.

Ecosystem responses to exotic earthworm invasion in northern North American forests.

Earth is experiencing a substantial loss of biodiversity at the global scale, while both species gains and losses are occurring at local and regional scales. The influence of these nonrandom changes in species distributions could profoundly affect the functioning of ecosystems and the essential services that they provide. However, few experimental tests have been conducted examining the influence of species invasions on ecosystem functioning. Even fewer have been conducted using invasive ecosystem engineers, which can have disproportionately strong influence on native ecosystems relative to their own biomass. The invasion of exotic earthworms is a prime example of an ecosystem engineer that is influencing many ecosystems around the world. In particular, European earthworm invasions of northern North American forests cause simultaneous species gains and losses with significant consequences for essential ecosystem processes like nutrient cycling and crucial services to humanity like soil erosion control and carbon sequestration. Exotic earthworms are expected to select for specific traits in communities of soil microorganisms (fast-growing bacteria species), soil fauna (promoting the bacterial energy channel), and plants (graminoids) through direct and indirect effects. This will accelerate some ecosystem processes and decelerate others, fundamentally altering how invaded forests function. This project aims to investigate ecosystem responses of northern North American forests to earthworm invasion. Using a novel, synthetic combination of field observations, field experiments, lab experiments, and meta-analyses, the proposed work will be the first systematic examination of earthworm effects on (1) plant communities and (2) soil food webs and processes. Further, (3) effects of a changing climate (warming and reduced summer precipitation) on earthworm performance will be investigated in a unique field experiment designed to predict the future spread and consequences of earthworm invasion in North America. By assessing the soil chemical and physical properties as well as the taxonomic (e.g., by the latest next-generation sequencing techniques) and functional composition of plant, soil microbial and animal communities and the processes they drive in four forests, work packages I-III take complementary approaches to derive a comprehensive and generalizable picture of how ecosystems change in response to earthworm invasion. Finally, in work package IV meta-analyses will be used to integrate the information from work packages I-III and existing literature to investigate if earthworms cause invasion waves, invasion meltdowns, habitat homogenization, and ecosystem state shifts. Global data will be synthesized to test if the relative magnitude of effects differs from place to place depending on the functional dissimilarity between native soil fauna and exotic earthworms. Moving from local to global scale, the present proposal examines the influence of earthworm invasions on biodiversity-ecosystem functioning relationships from an aboveground-belowground perspective in natural settings. This approach is highly innovative as it utilizes the invasion by exotic earthworms as an exciting model system that links invasion biology with trait-based community ecology, global change research, and ecosystem ecology, pioneering a new generation of biodiversity-ecosystem functioning research.

Niche-structured assemblages of exotic earthworms in headwater streambanks in eastern New York State, USA

In eastern North America, most Lumbricid earthworms found today above the post-Wisconsin Glacial boundary are non-indigenous, some with marked potential as invasive and ecologically disruptive species. These earthworms tend to appear as assemblages, not solitary species. Among potential explanations are successional facilitation among taxa, anthropogenic dispersal mechanisms that promote multi-species introductions, or simply shared habitat determinants that lead to accumulations through various dispersal pathways. We examined headwater streambanks in higher elevation forests of eastern New York State, and found up to 15 lumbricid earthworm species per 50 m-long reach among 14 sites divided between two montane regions, the northern Catskill Mountains and the Helderberg Plateau of eastern New York State.After pooling six surveys per site taken over two years, we found consistent differences between the two regions. Although most species (14/18) were found in both regions, their relative abundances and assortment patterns differed. Eisenoides lonnbergi and Bimastos rubidus, two native species were more prevalent in the Catskills, and represented new records for both regions. Ordination (CCA) on a set of measured environmental parameters revealed that most species were distributed along a soil pH-tree composition gradient. At the site level, clustering was strongly regional, despite a relatively small distance (<25 km) separating the regions. In all, several determinants may be at work in shaping observed earthworm assemblages. However, we did not detect evidence for interspecific interactions as a structuring element. When tested with a null model simulation, observed pairwise species associations did not depart significantly from random expectations (z-tests, p > 0.30 for both regions). Furthermore, the riparian zones we surveyed are relatively dynamic settings, so the stability of these novel assemblages is uncertain. With other invasive earthworm species now spreading throughout New York State, that uncertainty may grow.

Studies on the toxic effects of agrochemical pesticide (Monocrotophos) on physiological and reproductive behavior of indigenous and exotic earthworm species

ABSTRACTEarthworms are an ideal biological model in toxicity assays and environmental monitoring studies. In the present study, the reproductive toxicity and histopathological effects of Monocrotophos pesticide on an exotic epigeic Eudrilus eugeniae and an indigenous epigeic Perionyx barotensis earthworm were studied. Earthworm species were exposed to different concentrations of pesticide like 450 ppm, 500 ppm, and 650 ppm for 45 days and the mortality rate and reproductive activity was recorded every 15 days of exposure. There was an increase in mortality and abnormal sperm (asthenospermia, necrospermia, and oligospermia) and defective cocoons in earthworms with increasing concentrations of the pesticide. Histopathological changes like rupture of chloragogenous tissue, longitudinal muscle, fused and extra-villous growth and necrotic cell rupture in earthworm’s body wall (epidermis, circular and longitudinal muscles) were observed. Fluorescent probes have detected cell death in pesticide-treated earthworms when compared to the control group after 45 days. The present findings show that Monocrotophos pesticide on exposure to epigeic earthworm species causes significant reproductive toxicity and histopathological abnormalities and these changes could be used as a tool in environmental risk assessment of pesticides.Abbreviations: DDT: Dichlorodiphenyltrichloroethane; MCP: Monocrotophos; EPA: Environment Protection Act; SL: Soluble Liquid; C: N (Carbon: Nitrogen); C: P (Carbon: Phosphorus); LC: Lethal Concentration; PBS: Phosphate Buffer Solution; WHO: World Health Organization; H&E: Hematoxylin and Eosin; SV: seminal vesicles; O: ovary; GP: genital papillae; Ch: chloragogenous tissue; EL: epithelial layer; CM: circular muscle; LM: longitudinal muscle; CD: cell debris

Invasive lumbricid earthworms in northeastern North American forests and consequences for leaf-litter fauna

Colonization of North America by exotic earthworms has been implicated in undesirable changes in soil structure, nutrient cycling, and biodiversity. Invasion by putative European earthworms has a long history in northeastern North America. Partly for this reason, factors that may be continuing to facilitate expansion of earthworm distributions and the consequences of earthworm spread in the Northeast get relatively little attention. We sampled earthworms and environmental attributes at 85 sites in central New York. We additionally sampled leaf-litter fauna at 25 of these sites. We detected no earthworms at 27 of 71 forested sites (38%). Forested sites without detectable earthworm populations were farther from the nearest road and had soils of lower pH than forested sites with earthworms. Proximity of the nearest road was strongly associated with earthworm diversity and abundance, and earthworm biomass was highest in low, moist areas. We found a strong, negative relationship between the biomass of earthworms and abundance of invertebrates in the litter layer. This association was likely mediated by the abundance of organic litter, which was lower at sites with high biomass of earthworms. Sites with only the putative native Bimastos (Dendrodrilus) rubidus had a high mass of leaf litter and large numbers of leaf litter animals despite high densities of this species. We believe that there is potential for further expansion of European earthworm taxa in the Northeast and strong evidence for negative consequences of this expansion. Additional regulations on activities that promote introduction may be necessary.

Exotic earthworms maintain soil biodiversity by altering bottom-up effects of plants on the composition of soil microbial groups and nematode communities.

Bottom-up effects of plants on soil communities can be modified by the activity of exotic earthworms, by altering resource availability for soil food webs through feeding, burrowing, and casting activities. The present study explored effects of plants (planting of shrubs) on soil micro-food webs (composition of soil microbial and nematode communities), and whether these effects were altered by the activity of exotic earthworms (exotic earthworms addition). Planted shrubs resulted in a non-significant increase of bacterial biomass and significantly increased the abundance of different nematode trophic groups and total nematode biomass, indicating that planted shrubs had significant bottom-up effects on soil bacteria and nematodes. Planted shrubs decreased nematode diversity, evenness, and richness, but increased nematode dominance in the plots where the abundance of exotic earthworms was not amended. By contrast, these effects of shrub presence on soil biodiversity were not found in the plots that received exotic earthworms. In addition, planted shrubs increased the total energy flux to the nematode community. By contrast, the elevated activity of exotic earthworms mitigated the increase in total energy flux to nematodes in the presence of shrubs, and increased the ratio of fungal to bacterial PLFAs. Both of these changes indicate reduced energy flux in the plots with added exotic earthworms. Nematode diversity decreased, while nematode dominance increased with increasing total energy flux to nematodes, probably because few species benefited from high energy flux. Our study indicates that exotic earthworms can maintain soil biodiversity by reducing the energy flux through soil food webs.

Nutrient recovery from pigeon dropping by using exotic earthworm Eisenia fetida

Pigeon dropping is a kind of organic waste which can be transformed easily into organic manure by vermicomposting with exotic earthworm Eisenia fetida. In the present study, a pigeon excreta was collected from roof tops. The pigeon excreta was mixed with cattle dung with the ratios as 10%, 20%, 30%, 40% and 50% respectively, in plastic containers; meanwhile, those proposal were name as C10, C20, C30, C40 and C50 respectively. Feed mixtures were allowed to decompose (pre-vermicomposting without earthworm) for 20–25 days. After decomposition, 20 hatchlings of E. fetida were put in each concentration after weighing. Cattle dung (without pigeon excreta) was kept as the control. The physico-chemical analysis of initial feed mixture and final product after vermicomposting was also done to measure the changes in the feed mixtures from the initial to the final states. There were increases in the content of N (52.35%), P (115.79%), K (39.97%) and EC (56.16%) but decrease in those of OC (-15.49%), OM (-15.49%), pH (-7.92%) and Ca (-39.62%) from the initial to the final product. The highest population size of earthworms and minimum mortality rate was observed in C30 feed mixture. Thus, the present study indicated that cattle dung mixed with 30% (w/w) pigeon excreta waste may be a good choice for vermicomposting.

Earthworm species in public parks in Curitiba, Paraná, Brazil.

Earthworms are important macroinvertebrates that provide soil ecosystem services and are also useful environmental bioindicators. Urban areas around the world have major impacts on biodiversity and the objective of the present study was to assess the role of urban parks of Curitiba, Paraná State, in preserving native earthworm species. Earthworm populations were sampled in five parks (Barigui, Tingui, Barreirinha, Passaúna and the Botanic Garden), in two land use systems (grass lawns and secondary forest fragments) in two seasons, summer (November 2013) and winter (June 2014). A total of twelve earthworm species were identified, belonging to six families: Glossoscolex sp.1, Fimoscolex sp.1, sp.2 and sp.3 (Glossoscolecidae), Pontoscolex corethrurus (Rhinodrilidae), Eukerria tucumana (Ocnerodrilidae), Amynthas gracilis, Amynthas corticis, Metaphire californica (Megascolecidae), Aporrectodea rosea and Lumbricus rubellus (Lumbricidae), the latter being the first record for this species in Brazil. In addition, a single unidentified juvenile Dichogaster sp. (Acanthodrilidae) was found. Four new species were found and three out of five urban parks of Curitiba (especially the Botanic Garden) were able to preserve native species, though their abundance was low and exotic species (n=8) predominated, attributed to human disturbance that favors invasion and colonization of exotic earthworms.

Soil macrofauna diversity as a key element for building sustainable agriculture in Argentine Pampas

The agricultural activity in the Argentine Pampas, characterized by an important trend towards no-till soybean monocropping, has completely transformed the original Pampas landscape into a monotonous scenario with a continuous succession of farms of very low crop diversity. This process has led to soil physical, chemical and biological degradation in those systems. The increase of crop rotation rates in no-till and reduced tillage systems has been proposed as an alternative with reduced negative impact on soils in the context of conventional agriculture. On the other hand, extensive organic farming is also suggested as an alternative to high-input agriculture systems. In this article, we aim to explore how different variations of farming practices and systems impact soil macrofauna, along an edaphoclimatic gradient in the Pampas region. We studied the following systems: natural grassland (Gr) as indicator of the original community, extensive organic farming (Org), conventional agriculture with no-tillage and three crop rotation levels (Nt-R1, Nt-R2 and Nt-R3), and reduced tillage with two levels of crop rotation (Til and Til-R). We assessed soil macrofauna, with emphasis on earthworm, beetle and ant communities; and soil physical and chemical properties. Macrofaunal taxa composition was significantly affected by both management systems and edaphoclimatic conditions. The Gr community had pronounced differences from all the agricultural systems. The earthworm community from Gr had distinctive features from those of most agricultural systems, with Org and Nt-R3 being the most similar to Gr in native and exotic earthworm species, respectively. The beetle community in Org was the most different one, and the communities from the other systems did not show a pattern related to management. Ant community composition was not determined by management systems, but it was affected by edaphoclimatic conditions. All the studied macrofauna groups had a significant co-variation with soil physical and chemical properties, showing that both the characteristics of each soil relative to the geographic location and the effect of management on abiotic soil attributes have an important effect on soil macrofauna. This study confirms that biodiversity is being lost in Pampas soils, which implies a possible threat to the soil capacity to perform the processes that sustain soil functioning and hence plant productivity. Further considerations about the sustainability of the current agricultural model applied in the Argentine Pampas are needed.

Using DNA Metabarcoding to Examine Wild Pig (Sus scrofa) Diets in a Subtropical Agro-Ecosystem

Author(s): Anderson, Wesley M.; Boughton, Raoul K.; Wisely, Samantha W.; Merrill, Mary M.; Boughton, Elizabeth H.; Robeson, Michael S., II; Piaggio, Antoinette | Abstract: The wild pig is well known for its generalist diet, a contributing factor to its successful invasion around the globe. We used DNA metabarcoding analyses of scat to examine wild pig diet on a cow-calf operation in south-central Florida. This 4,249-ha ranch is comprised of improved pastures and semi-native pastures that contain a mosaic of vegetation types. Both pasture types contain numerous wetlands and ditches as well as oak-palm woodlands. Fecal sampling was conducted along transects from March 2016 to February 2017. The study site was divided into five sampling areas to ensure dispersed sampling across the ranch. At least five freshly deposited scats were collected every two months from each sampling area and frozen. Regions of multiple genes that targeted either animal or plant DNA (CO1, trnL, and 12S rRNA marker genes) were selected for high throughput sequencing. Sequences were identified using the GenBank reference database. Two hundred nineteen fecal samples were collected and 196 were analyzed. Consensus lineages were retained if they could be confidently identified to family and were likely intentionally consumed by a pig. Between the three marker genes, 66 plant, 68 animal, and 12 fungal families were identified. Plant species dominated the diet with oak, torpedograss, joyweed, Bahiagrass, dayflower, and other grasses occurring in over half the samples analyzed. Animals were present across a wide taxonomic breadth, but encountered less frequently than plants with the exception of an exotic earthworm. Cattle, house mouse, cotton mouse, raccoon, mole cricket, Virginia opossum, and six species of fly were recorded from over 10% of fecal samples. This represents the first study to employ DNA metabarcoding to examine the dietary composition of this invasive vertebrate across an entire year.

Cooperation of earthworm and arbuscular mycorrhizae enhanced plant N uptake by balancing absorption and supply of ammonia

Earthworms and arbuscular mycorrhizal fungi (AMF) interact to regulate plant nitrogen (N) supply, but the mechanisms through which they affect plant N uptake are unclear. We hypothesized that earthworms, plants and the associated AMF exhibit different preferences for different forms of inorganic N (NH4+ and NO3−), which could regulate the effect of earthworms and AMF interaction on plant N acquisition. We outlined three independent but complementary experiments to test this hypothesis in the context of exotic earthworm, Pontoscolex corethrurus. The earthworm is dominating the plantation forests in subtropical and tropical regions of China, which have their understory dominated by the fern Dicranopteris dichotoma. By employing an excised root 15N incubation experiment and a field in situ15N experiment, we found that the fern prefers to use NH4+ rather than NO3−. Then we did a 2 × 2 factorial microcosm experiment using AMF (Rhizophagus intraradices) and earthworms (P. corethrurus). The exotic earthworm increased soil NH4+ concentration but did not affect soil NO3− concentration, while the AMF decreased soil NH4+ concentration but had no effect on soil NO3− concentration. The increase in soil NH4+ induced by the earthworms was efficiently utilized by the AMF, and significantly increased the total N uptake by the fern. In contrast, the AMF alone increased the N concentration of leaves and coarse roots, but not the total plant N uptake, primarily due to the lower levels of available NH4+ compared with the earthworm treatments. The uninoculated fern did not benefit from the earthworm-induced increase in soil NH4+, suggesting that the root of the fern cannot access the ‘NH4+ hotspots’ created by the earthworms. Our work suggests that successful cooperation of earthworms and AMF on plant N uptake depends on the correct match in N-form.

Plant-facilitated effects of exotic earthworm Pontoscolex corethrurus on the soil carbon and nitrogen dynamics and soil microbial community in a subtropical field ecosystem.

Earthworms and plants greatly affect belowground properties; however, their combined effects are more attractive based on the ecosystem scale in the field condition. To address this point, we manipulated earthworms (exotic endogeic species Pontoscolex corethrurus) and plants (living plants [native tree species Evodia lepta] and artificial plants) to investigate their combined effects on soil microorganisms, soil nutrients, and soil respiration in a subtropical forest. The manipulation of artificial plants aimed to simulate the physical effects of plants (e.g., shading and interception of water) such that the biological effects of plants could be evaluated separately. We found that relative to the controls, living plants but not artificial plants significantly increased the ratio of fungal to bacterial phospholipid fatty acids (PLFAs) and fungal PLFAs. Furthermore, earthworms plus living plants significantly increased the soil respiration and decreased the soil NH 4 +‐N, which indicates that the earthworm effects on the associated carbon, and nitrogen processes were greatly affected by living plants. The permutational multivariate analysis of variance results also indicated that living plants but not earthworms or artificial plants significantly changed the soil microbial community. Our results suggest that the effects of plants on soil microbes and associated soil properties in this study were largely explained by their biological rather than their physical effects.

POTENSI CACING TANAH EKSOTIK ENDOGEIK Pontoscolex corethrurus UNTUK PRODUKSI VERMIKOMPOS GRANUL (VERMIGRAN) BERBASIS BAHAN ORGANIK LOKAL

&lt;p&gt;The potential of Exotic Earth worm Endogeik (Pontoscolex corethrurus) for Production Vermikompos granules (Vermigran) Local Organil-Based Materials. In 2011, total demand for organic fertilizer in Indonesia was 12.394 million tons and 2.601 million tons of new available. This requirement will continue to increase until 2015, so the opportunity to develop great organic fertilizer. One disadvantage of the use of organic fertilizers is very much in volume (bulky), it is necessary vermikompos manufacturing innovation in the form of granules to be more efficient in the applicationand transport. Research objectives are: (1) study the potential of earthworms in producing vermikompos Pontoscolex corethrurus of l ocal organic ingredients, and (2)produce quality vermikompos in the form of granules. The study was conducted in a greenhouse Fak. Agriculture and in the yard of a house in Ngesrep, Boyolali, in July-November 2011. The study design using a Completely Randomized Design, factorial,two factor. Factor 1 is composed of three types of worms cedar, and the second factoris the variation of the type of organic material, consisting of 7 cedar. The variablesmeasured were vermikompos nutrient quality and speed of the water solubility vermikompos granules. The results showed that Pontoscolex corethrurus high potentialto produce vermikompos that meet ISO quality compost. Cow pile, pile quail, water hyacinth can be used as a raw material vermikompos. Clay, starch, starch and claymixture (1:1) can be used as an adhesive vermikompos granules (vermigran) soluble in water at &amp;lt;48 hours. Production vermigran great potential for developmentas a high-quality organic fertilizer.&lt;/p&gt;

Exotic Earthworms Decrease Cd, Hg, and Pb Pools in Upland Forest Soils of Vermont and New Hampshire USA.

Exotic earthworms are present in the forests of northeastern USA, yet few studies have documented their effects on pollutant metals in soil. The objective of this study was to identify if Cd, Hg, and Pb strong-acid extractable concentrations and pools (bulk inventories) in forest soils decreased with the presence of exotic earthworms. We compared 'Low Earthworm Abundance' (LEA) sites (≤10g m-2 earthworms, n = 13) and 'High Earthworm Abundance' (HEA) (>10g m-2 earthworms, n = 17) sites at five watersheds across Vermont and New Hampshire. Organic horizon Cd, Hg, and Pb concentrations were lower at HEA than LEA sites. Organic horizon and total soil pools of Cd and Hg were negatively correlated with earthworm biomass. Soil profile Cd and Hg concentrations were lower at HEA than LEA sites. Our results suggest earthworms are decreasing accumulation of Cd, Hg, and Pb in forest soils, potentially via greater mobilization through organic matter disruption or bioaccumulation.

Exotic earthworm (Oligochaeta: Lumbricidae) assemblages on a landscape scale in central Canadian woodlands: importance of region and vegetation type

A growing understanding about the impacts of earthworms (Oligochaeta: Lumbricidae) on ecosystem processes and forest restoration necessitates an examination of their role in Canadian forests where they have become invasive. Little is known about the landscape-scale responses of earthworm populations to different regional characteristics and vegetation types within Canada’s central woodlands. We examined the regional variation of earthworm species richness, biomass, and assemblage composition across a range of four municipal regions (from south to north: Halton, Wellington, York, and Simcoe) and four habitat types (deciduous forest, mixed forest, tree plantation, and meadow) with varying soil characteristics in woodlands of south-central Ontario, Canada. In general, earthworm communities differed by region but not by habitat type. The most southern regions supported the highest earthworm species richness, biomass (i.e., Lumbricus and Octolasion), and density, and this was associated with a south–north gradient in soil characteristics. Assemblage composition differed by region but not by habitat type. The observed south–north gradient suggests an underlying effect of invasion spread associated with human settlement and density. Our results provide baseline information about earthworm communities in south-central Ontario forests and will enable managers to plan for the increasing role of earthworms in Canada’s future forests.