Introduction Of Earthworms Research Articles

A comparison of the relative toxicity of bone meal and other P sources used as remedial treatments to the earthworm Eisenia fetida

Abstract It has been suggested that sources of P could be used to remediate metal-contaminated soil. The toxicity of four potential P sources, potassium hydrogen phosphate (PHP), triple superphosphate (TSP), rock phosphate (RP) and raw bone meal (RBM) to Eisenia fetida was determined. The concentration of P that is statistically likely to kill 50% of the population (LC50) for PHP, TSP and RBM was determined in OECD acute toxicity tests. 14 day LC50s expressed as bulk P concentration lay in the range 3319–4272 mg kg−1 for PHP, 3107–3590 mg kg−1 for TSP and 1782–2196 mg kg−1 for RBM (ranges present the 95% confidence intervals). For PHP and TSP mortality was significantly impacted by the electrical conductivity of the treated soils. No consistent relationship existed between mortality and electrical conductivity, soil pH and available (Olsen) P across the PHP, TSP and RBM amendment types. In RP toxicity tests mortality was low and it was not possible to determine a LC50 value. Incineration of bone meal at temperatures between 200 and 300 °C, pre-washing the bone meal, co-amendment with 5% green waste compost and delaying introduction of earthworms after bone meal amendments by 21 days or more led to significant reductions in the bone meal toxicity. These results are consistent with the toxicity being associated with the release and/or degradation of a soluble organic component present in raw bone meal. Bone meal can be used as an earthworm-friendly remedial amendment in metal-contaminated soils but initial additions may have a negative effect on any earthworms surviving in the contaminated soil before the organic component in the bone meal degrades in the soil.

Field margins and management affect settlement and spread of an introduced dew-worm (Lumbricus terrestris L.) population

Abstract To study the feasibility of earthworm introduction for increasing the macroporosity and permeability of arable heavy clay, deep-burrowing earthworms ( Lumbricus terrestris L.) were inoculated into a tile drained experimental field in Jokioinen, S-W Finland in autumn 1996. Inoculation with the Earthworm Inoculation Unit technique was at the up-slope end of the field, in the field margins under permanent grass, and inside the four 0.46 ha plots of the field. The experiment was monitored on three occasions. In 1998 the L. terrestris population had persisted in low numbers only in field and plot margins. By 2003, when the field had been under set-aside grass for three years, density had grown in the margins and L. terrestris were also found inside the field at a very low density. The third monitoring was in autumn 2009, after a further four years as set-aside and a subsequent division of the field into no-till and ploughing management, and looked at the effects of management (margins, no-till, ploughing), distance from the inoculation and sub-drainage on L. terrestris abundance. The abundance displayed a clear gradient over the field, declining from 14 ind. and 18 g m −2 at 5–9 m from inoculation, to 1 ind. and 2 g m −2 at 56–60 m distance. Margins had the highest abundances (16 ind. and 32 g m −2 ), followed by no-till (4 ind. and 4 g m −2 ) and ploughing (1 ind. and 1 g m −2 ). Abundances were significantly higher above the tiles than between them ( P

Carbon–mineral interactions along an earthworm invasion gradient at a Sugar Maple Forest in Northern Minnesota

The interactions of organic matter and minerals contribute to the capacity of soils to store C. Such interactions may be controlled by the processes that determine the availability of organic matter and minerals, and their physical contacts. One of these processes is bioturbation, and earthworms are the best known organisms that physically mix soils. Earthworms are not native species to areas previously glaciated, and the introduction of earthworms to these regions has been associated with often dramatic changes in soil structure and geochemical cycles. The authors are studying C mineral interaction along an approximately 200 m long earthworm invasion transect in a hardwood forest in northern Minnesota. This transect extends from the soils where earthworms are absent to soils that have been invaded by earthworms for nearly 30–40 years. Pre-invaded soils have an approximately 5 cm thick litter layer, thin (5 cm) A horizon, silt rich E horizon, and clay-rich Bt horizons. The A and E horizons formed from aeolian deposits, while the clay-rich Bt horizons probably developed from underlying glacial till. With the advent of earthworm invasion, the litter layer disappears and the A horizons thicken at the expense of the O and E horizons. In addition, organic C contents in the A horizons significantly increase with the arrival of earthworms. Simultaneously, measured mineral specific surface areas suggest that minerals’ capacities to complex the organic matter appear to be greater in soils with active earthworm populations. Based on the data from two end member soils along the transect, mineral specific surface areas in the A and E horizons are larger in the earthworm invaded soil than in the pre-invasion soil. Additionally, within < 5 a of earthworm invasions, A horizon materials are turned from single grain to a strong medium granular structure. While A horizon organic matter content and organic C-mineral complexation increase after earthworm invasion, they are also more vigorously mixed. This growing data set, when ultimately combined with ongoing measurements of (1) the population dynamics of earthworms along the invasion transect, (2) C-mineral association (via surface adsorption and physical collusion in mineral aggregates) and (3) dissolved organic C will show how and how much soil capacity to store C is affected by burrowing organisms, which are often the keystone species of given ecosystems.

Impacts of epigeic, anecic and endogeic earthworms on metal and metalloid mobility and availability

The introduction of earthworms into soils contaminated with metals and metalloids has been suggested to aid restoration practices. Eisenia veneta (epigeic), Lumbricus terrestris (anecic) and Allolobophora chlorotica (endogeic) earthworms were cultivated in columns containing 900 g soil with 1130, 345, 113 and 131 mg kg(-1) of As, Cu, Pb and Zn, respectively, for up to 112 days, in parallel with earthworm-free columns. Leachate was produced by pouring water on the soil surface to saturate the soil and generate downflow. Ryegrass was grown on the top of columns to assess metal uptake into biota. Different ecological groups affected metals in the same way by increasing concentrations and free ion activities in leachate, but anecic L. terrestris had the greatest effect by increasing leachate concentrations of As by 267%, Cu by 393%, Pb by 190%, and Zn by 429% compared to earthworm-free columns. Ryegrass grown in earthworm-bearing soil accumulated more metal and the soil microbial community exhibited greater stress. Results are consistent with earthworm enhanced degradation of organic matter leading to release of organically bound elements. The degradation of organic matter also releases organic acids which decrease the soil pH. The earthworms do not appear to carry out a unique process, but increase the rate of a process that is already occurring. The impact of earthworms on metal mobility and availability should therefore be considered when inoculating earthworms into contaminated soils as new pathways to receptors may be created or the flow of metals and metalloids to receptors may be elevated.

Do non-native earthworms in Southeast Alaska use streams as invasional corridors in watersheds harvested for timber?

Exotic earthworms from Europe and Asia have invaded previously earthworm-free areas of North America where they consume leaf litter, mix soil horizons, and alter nutrient cycling. Primarily, earthworm introductions occur through human activities; we hypothesized that the combination of logging (i.e., road construction and soil disturbance) and stream transport (i.e., hydrochory) allows earthworms to invade new ecosystems and spread within watersheds. On Prince of Wales Island, AK, we surveyed riparian zones in 11 watersheds with varying timber harvest intensity for terrestrial oligochaetes. Additionally, common invasive earthworms were experimentally submerged in a local stream to test for tolerance to prolonged immersion: all taxa survived immersion for at least 6 days. Using principal components analysis, watershed and harvest variables describing the watersheds upstream of our sampled riparian areas were reduced to two principal components describing harvest intensity (PC1) and harvest style (PC2). Logistic models successfully predicted earthworm abundance (r2 = 0.70) from PC1, which indicated that watersheds with older, intense upstream timber harvest contained larger earthworm populations. Earthworm species richness was best predicted by PC2 (r2 = 0.39), which suggested that earthworm communities in watersheds containing large clear-cut stands were more species-rich. Collectively, these results suggest that (1) invasive earthworms may use streams for dispersal and (2) upstream introductions via timber harvest can initiate downstream earthworm invasions. Hydrochory would allow invasive earthworms to spread at rates (tens of km d−1) that are much greater than previously reported rates of terrestrial spread (5–10 m y−1). Effective control of exotic earthworms in riparian zones will require watershed-level management and surveillance.

Effect of earthworm on growth of late succession plant species in postmining sites under laboratory and field conditions

Earlier studies of postmining heaps near Sokolov, Czech Republic (0–46 years old) showed that massive changes in plant community composition occur around 23 year of succession when the heaps are colonized by the earthworms Lumbricus rubellus (Hoffm.) and Aporrectodea caliginosa (Savigny). The aim of the current study was to test the hypothesis that the introduction of earthworms into a postmining soil enhances growth of late succession plant species. In a laboratory experiment, earthworms significantly increased biomass of Festuca rubra and Trifolium hybridum grown in soil from a 17-year-old site. The biomass increase corresponded to a significant decrease in pH and an increase in oxidable C, total N, and exchangeable P, K, and Ca content. A second laboratory experiment showed higher biomass production of late successional plant community (Arrhenatherum elatius, Agrostis capillaris, Centaurea jacea, Plantago lanceolata, Lotus corniculatus, and Trifolium medium) in soil from late successional stage (46 years old); the introduction of earthworms into soil from an early successional stage (17 years old) increased biomass production. In a field experiment, introduction of L. rubellus to enclosures containing a 17-year-old soil not colonized by earthworms significantly increased the biomass of grasses after 1 year. The results support the hypothesis that colonization of postmining areas by earthworms can substantially modify soil properties and plant growth.

Human-facilitated invasion of exotic earthworms into northern boreal forests

Recreational and industrial development is rapidly expanding in the boreal forest of western Canada. Concerns exist that such activity is facilitating the introduction and spread of non-native species such as exotic earthworms. The mechanisms by which earthworms are introduced and spread in forested systems are not well understood. Given the poor intrinsic dispersal abilities of earthworms, we propose 4 major introduction mechanisms: 1) abandonment of worms brought as fishing bait; 2) dispersal via vehicles; 3) dispersal via vertebrate predators; or 4) dispersal via waterways. To test these hypotheses, we sampled earthworms in forest stands near boat launches, roads, seismic lines, forest interiors, and remote shorelines of lakes in the boreal forest of northern Alberta, Canada. Boat launches and roads had a significantly higher probability of earthworm occurrence (54% of plots occupied) compared with the other locations (13% of plots occupied). Species commonly used as fishing bait occurred more often near boat launches (18% of plots occupied) than near roads alone (1% of plots occupied). These results suggest that vehicle transport and bait abandonment may both be mechanisms of earthworm introduction. The consequences of these introductions remain unclear but suggest that reduced road construction and regulations prohibiting the discarding of bait need to be considered to slow earthworm invasions.

From Bait Shops to the Forest Floor: Earthworm Use and Disposal by Anglers

Nonindigenous earthworms are causing large and undesirable changes to forests across the U.S. Upper Midwest. Because earthworms have slow rates of natural spread, and because their distribution remains patchy in many areas, it would be possible to slow the rate of invasion if vectors of introduction can be identified and controlled. Earthworm populations are often found near lakes, and it has been suggested that anglers discarding unwanted bait are a vector for the establishment of new populations. Here, we have surveyed the bait trade and anglers to determine whether bait stores sell known invasive species and whether angler behavior is likely to lead to these species becoming introduced near lakes. All bait stores surveyed sold known invasive species and 44% of anglers who purchase bait dispose of unwanted bait on land or in trash. We conclude that the bait trade and subsequent disposal of worms by anglers constitute a major vector for earthworm introductions. Thus, slowing the spread of invasive earthworms will require efforts to change the species sold at bait stores and/or efforts to change angler behavior.

Does the activity of the earthworm Aporrectodea caliginosa modify the plant diversity effect on soil nematodes?

The effect of plant species richness and the presence of the earthworm species, Aporrectodea caliginosa on soil nematode abundance and community structure were studied in a field experiment. The purpose of the study was to see if 60 days of lasting activity of A. caliginosa could modify the plant diversity effect on soil nematodes. The experiment was established in the spring of 2004. Six hundred plastic containers (mesocosms) were placed into the ground and sown with grass. One half of the mesocosms were sown with the species ( Festuca rubra), and the second half were sown with a mixture of 8 grass species. One year later (after one growing season) 6 individual A. caliginosa were introduced into half of the mesocosms in each treatment—monoculture and mixture. The results are presented from two sampling dates: before earthworm introduction and 60 days after the introduction of A. caliginosa. At the beginning of the growing season, the total number of nematodes in the monoculture treatment was significantly lower than in the mixture treatment. The presence of earthworms did not influence the nematode density in the monoculture, while in the mixture treatment the total number of nematodes significantly increased. The presence of earthworms changed the vertical distribution of nematodes in both plant treatments, thus enhancing the penetration of deeper soil layers by nematodes. On each of the two sampling occasions the generic diversity of nematodes was lower in the monoculture than in the mixture treatment. In both plant treatments, nematode communities were more diverse in the presence of earthworms than in the same treatments without earthworms. Two trophic groups dominated nematode communities in all treatments: bacterial and plant feeders. Their proportions differed, however, between treatments and during different times in the experiment. After the introduction of the earthworms to the monoculture mesocosms, the proportion of bacterial feeders increased while the number of plant feeders decreased. In the mixture the opposite tendency was observed— the relative abundance of plant feeders increased while the number of bacterial feeders decreased.

Application of willows ( Salix viminalis) and earthworms ( Eisenia fetida) in sewage sludge treatment

The aim of the study was to verify the suitability of willows ( Salix viminalis) and earthworms ( Eisenia fetida) for sewage sludge management. The study was conducted in Tarnów city sewage plant. In April 2004, 81 pots were filled with concentrated sludge, 27 of which acted as controls, another 54 were planted with willows. In May, 20 mature earthworms were introduced to half (27) of the pots with willows. Every month the growth of willows was measured. The density of earthworms, size of willows, and the moisture content, and their chemical properties and structure of the sewage sludge were assessed in November 2004 when: (1) the moisture content of the sludge was lower in the pots with willows (49%) and with willows + earthworms (37%) than in the control (67%); (2) the mass increase of willow was higher by 38% for shoots and 41% for roots, in pots with earthworms; and (3) the introduction of willows and earthworms changed the structure of sludge. Willows and earthworms had no effect on the pH of the sludge, nor on its concentration of nutrients, heavy metals or forms of nitrogen.

REGIONAL EXTENT OF AN ECOSYSTEM ENGINEER: EARTHWORM INVASION IN NORTHERN HARDWOOD FORESTS

The invasion of exotic earthworms into northern temperate and boreal forests previously devoid of earthworms is an important driver of ecosystem change. Earthworm invasion can cause significant changes in soil structure and communities, nutrient cycles, and the diversity and abundance of herbaceous plants. However, the regional extent and patterns of this invasion are poorly known. We conducted a regional survey in the Chippewa and Chequamegon National Forests, in Minnesota and Wisconsin, U.S.A., respectively, to measure the extent and patterns of earthworm invasion and their relationship to potential earthworm introduction sites. We sampled earthworms, soils, and vegetation in 20 mature, sugar maple-dominated forest stands in each national forest and analyzed the relationship between the presence of five earthworm taxonomic groups, habitat variables, and distance to the nearest potential introduction site. Earthworm invasion was extensive but incomplete in the two national forests. Four of the six earthworm taxonomic groups occurred in 55-95% of transects; however 20% of all transects were invaded by only one taxonomic group that has relatively minor ecological effects. Earthworm taxonomic groups exhibited a similar sequence of invasion found in other studies: Dendrobaena > Aporrectodea = Lumbricus juveniles > L. rubellus > L. terrestris. Distance to the nearest road was the best predictor of earthworm invasion in Wisconsin while distance to the nearest cabin was the best predictor in Minnesota. These data allow us to make preliminary assessments of landscape patterns of earthworm invasion. As an example, we estimate that 82% of upland mesic hardwood stands in the Wisconsin region are likely invaded by most taxonomic groups while only 3% are unlikely to be invaded at present. Distance to roads and cabins provides a coarse-scale predictor of earthworm invasion to focus stand-level assessments that will help forest managers better understand current and potential forest conditions and identify uninvaded areas that could serve as important refugia for plant species threatened by earthworm invasion.

Policy and management responses to earthworm invasions in North America

The introduction, establishment and spread of non-native earthworm species in North America have been ongoing for centuries. These introductions have occurred across the continent and in some ecosystems have resulted in considerable modifications to ecosystem processes and functions associated with above- and belowground foodwebs. However, many areas of North America have either never been colonized by introduced earthworms, or have soils that are still inhabited exclusively by native earthworm fauna. Although several modes of transport and subsequent proliferation of non-native earthworms have been identified, little effort has been made to interrupt the flow of new species into new areas. Examples of major avenues for introduction of earthworms are the fish-bait, horticulture, and vermicomposting industries. In this paper we examine land management practices that influence the establishment of introduced species in several ecosystem types, and identify situations where land management may be useful in limiting the spread of introduced earthworm species. Finally, we discuss methods to regulate the importation of earthworms and earthworm-containing media so that introduction of new exotic species can be minimized or avoided. Although our focus in this paper is necessarily North American, many of the management and policy options presented here could be applicable to the problem of earthworm invasions in other parts of the world.

Increase in the Nitrogen Content of Soil by the Introduction of Earthworms into Soil

The contribution of an earthworm species (Amynthas vittatus) to the increase of the nitrogen content of soil was examined. Three specimens of adult earthworms were introduced into 300 g of soil (Gray Lowland soil, silty clay) supplemented with 1% carboxymethyl cellulose in a container and incubated for 32 d at 22°C in the dark. The contents of total-N, NH4-N and NO3-N, and the population of aerobic nitrogen-fixing bacteria in soil significantly increased after incubation with the earthworms, while the natural abundance of 15N (δ15N) in soil decreased. The amount of nitrogen in the earthworms did not decrease during the incubation in the microcosm. Both acetylene reduction activity of the microcosm and incorporation of 15N to soil from atmospheric 15N2 were significantly enhanced by the introduction of the earthworms into soil, though the observed increment of nitrogen in soil was much higher than the estimated one based on the nitrogen-fixing activity. The results obtained in the present study indicated that the earthworms increased the nitrogen content of soil, presumably due to the enhancement of the nitrogen-fixing activity of the soil from the microcosm by the earthworms.

Impact of tillage practices and burrows of a native Australian anecic earthworm on soil hydrology

Anecic earthworms are rare in Australian soils and potential benefits of introduction of exotic anecic earthworms have been suggested. The contribution of the native anecic earthworms to soil hydrology is unknown. The impact of tillage on the abundance and continuity of burrows formed by the native earthworm, Spenceriella hamiltoni (Fletcher) and consequent effect on hydrology were investigated in a red earth (Ultisol) in the Central Tablelands of New South Wales, Australia. On the permanent pasture site, the burrows occurred at a density of 157 (±65) m −2, had an average diameter of 6.0 mm (S.D.=1.6), and a predicated median length of 1.8 m. Dye infiltration studies showed that only 53% of the burrow openings were conducting and therefore available for infiltration under high rainfall conditions. It was estimated that a single burrow over an area of one square metre had an infiltration rate of 1.9 times that of the soil matrix (6.7 mm h −1 versus 3.6 mm h −1). Prediction using the rainfall characteristics of the region and the existing density of transmitting burrows under permanent pasture suggests that runoff should be a rare event (<once every 100 years). While earthworm burrow density under no-tillage (NT) cropping was similar to that found under permanent pasture, 3 years of conventional tillage (CT) involving discing reduced transmitting burrows by nearly 90% (to only 10 m −2) and this had the effect of a 8.3-fold reduction in maximum infiltration rate of the soil, thereby significantly increasing the likelihood of runoff and erosion.

Nutrient Mineralization and Leaf Litter Preference by the Earthworm Pontoscolex corethrurus on Iron Ore Mine Wastes

Abstract The effects of the earthworm Pontoscolex corethrurus (Muller) on the rate of mineralization of cattle dung‐amended iron (Fe2+) ore mine wastes and its preference for partially decomposed leaf litter with contrasting chemical composition were studied in pot trials. The growth and survival rates of earthworms showed significant positive correlations with percent of organic matter. During 96 days of exposure, the earthworms significantly increased exchangeable Ca2+, Mg2+, PO43− and NH4‐N. Iron ore mine wastes amended with 5–10% organic matter supported earthworm fauna better than mine wastes amended with 0–3% organic matter. The leaf litter preference shown by the earthworm was, in descending order, Phyllanthus reticulatus, Tamarindus indica, Anacardium occidentale, Casuarina equisetifolia, Acacia auriculiformis, and Eucalyptus camaldulensis. A significant positive correlation was observed between the survival and growth rates of earthworms and the nutrient contents of partially decomposed leaf litter. The first three plant species were significantly richer in nutrients, mainly organic carbon, calcium, phosphorus, and nitrogen, than the other two plant species. Acacia auriculiformis and E. camaldulensis litter were preferred less because of their high lignin and polyphenolic compounds, despite being rich in other macronutrients like nitrogen and phosphorus. It is concluded that the introduction of P. corethrurus to cattle dung‐amended (5–10%) iron ore mine wastes or revegetation of the sites with P. reticulatus, T. indica, and A. occidentale plant species should be attempted before earthworm introduction. The litter from these species acts as a source of food for earthworms, thereby hastening the process of restoration of abandoned iron ore mines of Goa, India.

Detecting Change in Forest Floor Carbon

Changes over time in forest soils are important to global C balance and to local ecosystem function. Detecting change in C storage in the forest floor is hampered by high variability and the use of study designs that are not adequate to statistically detect change. Using estimates of variability from previous forest floor studies, mostly conducted in the northern USA and Canada, we conducted statistical power analyses to assess the ability of such studies to detect various magnitudes of change in forest floor C. The studies we surveyed were unable to detect statistically significant changes in forest floor C or mass smaller than 15 to 20%. Studies that remeasure plots or sites (i.e., paired designs) have greater statistical power to detect changes than those in which experimental units are independently located for the two sampling dates. The causal mechanisms of forest floor change influence the magnitude of the change, and accordingly our ability to detect such changes. The direct effects of climate change may be too small to be detectable by current designs, but larger changes in forest floor mass resulting from forest management, changes in tree species, changes in fire regime, or the introduction of earthworms are more likely to be detectable. With paired resampling and more efficient allocation of sampling effort, it should be possible for future studies to detect smaller changes.

Nitrification and denitrification activities of zinc-treated soils worked by the earthworm Pheretima sp.

Little information is available on the roles of earthworms in N transformation and biological activities in heavy metal-contaminated soils. The purpose of the present paper is to examine the effects of earthworm on nitrifying and denitrifying enzyme activities of Zn-treated soils. ZnCl2 solution was added to soils at rates ranging from 0 to 400 mg Zn kg–1 and was allowed to fractionate and stabilize for 60 days. The Zn-tolerant earthworm Pheretima sp., which had been previously screened, was then introduced into Zn-treated soils and allowed to work for 40 days. Original soils without the addition of Zn and introduction of earthworms but incubated under the same conditions were used as controls. Zn-treated soils without the introduction of earthworms were also used as controls. Results showed that earthworm activity increased both nitrifying and denitrifying enzyme activities of the soils. These beneficial effects of earthworms were particularly evident in the treatments where Zn had an adverse effect. Zn added at a rate ≤200 mg Zn kg–1 generally had a stimulating effect on the enzyme activities measured. However, Zn added at a rate >200 mg Zn kg–1 had an adverse effect on nitrifying and denitrifying enzyme activities, which could be alleviated or even completely eliminated by earthworm activities.

Medium-term evaluation of a forest soil restoration trial combining tree species change, fertilisation and earthworm introductionThe 7th international symposium on earthworm ecology · Cardiff · Wales · 2002

A mixed stand of red oak (Quercus rubra) and common beech (Fagus sylvatica) on a compacted and acidified sandy loam soil was harvested and reforested with ash (Fraxinus excelsior) in 1992. The ecosystem restoration trial in this newly established ash plantation included 180 trees and was set up in a block design with 4 blocks, 3 experimental groups per block and 15 trees per experimental group. Experimental groups were: (1) application of P, K, Ca and Mg fertiliser to the planting pit; (2) combined application of fertiliser and earthworms to the planting pit; and (3) a control without additional restoration measures. Fertiliser application consisted of 500g dolomite, 100g Thomas slags and 100g kieserite; earthworm introduction consisted of 40 individuals, being 20 anecics ( Lumbricus terrestris L. and Nicodrilus longus Ude) and 20 endogeics ( Aporrectodea caliginosa Sav., Aporrectodea rosea Sav. and Allolobophora limicola Michaelsen). Tree growth was monitored annually. The control trees failed to grow and died after two years. Excellent growth was found for treated trees, and treatment-related growth patterns were observed: fertilised trees grew faster than fertilised trees with earthworms during the first two years, with the trend reversed from year 4 onwards. Although this trend suggested that introduced earthworms provided a more sustained response to fertiliser, this was not conclusively confirmed by an evaluation of 24 trees 10 years after planting (based on nutrient concentration in above-ground biomass and soil, litter biomass, earthworm biomass, and aggregate stability of organic particles in the soil); although statistically significant differences were found between treated and untreated plots, differences between fertilised plots with and without earthworms were not significant. Endogeic earthworms recolonised most fertilised plots, with or without earthworm introduction. Anecic earthworms did not colonize any plots. Although our findings suggest that earthworm introduction might contribute to a sustained fertiliser response in ash trees, more experiments are needed to demonstrate the precise role of earthworm introduction as part of integrated forest soil restoration.

Medium-term evaluation of a forest soil restoration trial combining tree species change, fertilisation and earthworm introduction: The 7th international symposium on earthworm ecology · Cardiff · Wales · 2002

A mixed stand of red oak (Quercus rubra) and common beech (Fagus sylvatica) on a compacted and acidified sandy loam soil was harvested and reforested with ash (Fraxinus excelsior) in 1992. The ecosystem restoration trial in this newly established ash plantation included 180 trees and was set up in a block design with 4 blocks, 3 experimental groups per block and 15 trees per experimental group. Experimental groups were: (1) application of P, K, Ca and Mg fertiliser to the planting pit; (2) combined application of fertiliser and earthworms to the planting pit; and (3) a control without additional restoration measures. Fertiliser application consisted of 500g dolomite, 100g Thomas slags and 100g kieserite; earthworm introduction consisted of 40 individuals, being 20 anecics ( Lumbricus terrestris L. and Nicodrilus longus Ude) and 20 endogeics ( Aporrectodea caliginosa Sav., Aporrectodea rosea Sav. and Allolobophora limicola Michaelsen). Tree growth was monitored annually. The control trees failed to grow and died after two years. Excellent growth was found for treated trees, and treatment-related growth patterns were observed: fertilised trees grew faster than fertilised trees with earthworms during the first two years, with the trend reversed from year 4 onwards. Although this trend suggested that introduced earthworms provided a more sustained response to fertiliser, this was not conclusively confirmed by an evaluation of 24 trees 10 years after planting (based on nutrient concentration in above-ground biomass and soil, litter biomass, earthworm biomass, and aggregate stability of organic particles in the soil); although statistically significant differences were found between treated and untreated plots, differences between fertilised plots with and without earthworms were not significant. Endogeic earthworms recolonised most fertilised plots, with or without earthworm introduction. Anecic earthworms did not colonize any plots. Although our findings suggest that earthworm introduction might contribute to a sustained fertiliser response in ash trees, more experiments are needed to demonstrate the precise role of earthworm introduction as part of integrated forest soil restoration.

Grassland Management and Conversion into Grassland: Effects on Soil Carbon

Grasslands are heavily relied upon for food and forage production. A key component for sustaining production in grassland ecosystems is the maintenance of soil organic matter (SOM), which can be strongly influenced by management. Many management techniques intended to increase forage production may potentially increase SOM, thus sequestering atmospheric carbon (C). Further, conversion from either cultivation or native vegetation into grassland could also sequester atmospheric carbon. We reviewed studies examining the influence of improved grassland management practices and conversion into grasslands on soil C worldwide to assess the potential for C sequestration. Results from 115 studies containing over 300 data points were analyzed. Management improvements included fertilization (39%), improved grazing management (24%), conversion from cultivation (15%) and native vegetation (15%), sowing of legumes (4%) and grasses (2%), earthworm introduction (1%), and irrigation (1%). Soil C content and concentration increased with improved management in 74% of the studies, and mean soil C increased with all types of improvement. Carbon sequestration rates were highest during the first 40 yr after treatments began and tended to be greatest in the top 10 cm of soil. Impacts were greater in woodland and grassland biomes than in forest, desert, rain forest, or shrubland biomes. Conversion from cultivation, the introduction of earthworms, and irrigation resulted in the largest increases. Rates of C sequestration by type of improvement ranged from 0.11 3.04 Mg C.ha(-1) yr(-1), with a mean of 0.54 Mg C.ha(-1).yr(-1) and were highly influenced by biome type and climate. We conclude that grasslands can act as a significant carbon sink with the implementation of improved management.