蚯蚓在生态系统中的作用

蚯蚓能够对许多决定土壤肥力的过程产生重要影响, 被称为“生态系统工程师”。它通过取食、消化、排泄和掘穴等活动在其体内外形成众多的反应圈, 从而对生态系统的生物、化学和物理过程产生影响。蚯蚓在生态系统中既是消费者、分解者, 又是调节者, 它在生态系统中的功能具体表现在: (1) 对土壤中有机质分解和养分循环等关键过程的影响; (2) 对土壤理化性质的影响; (3) 与植物、微生物及其他动物的相互作用。蚯蚓活动及其在生态系统中的功能受蚯蚓生态类群、种群大小、植被、母岩、气候、时间尺度以及土地利用历史的综合控制。蚯蚓外来种入侵与生态系统的关系以及蚯蚓对全球变化的响应和影响是两个值得关注的问题。土壤本身的复杂性, 蚯蚓自然历史和生物地理学知识的缺乏, 野外控制蚯蚓群落方法的滞后等都限制了蚯蚓生态学的发展。其他新技术如研究养分循环的碳氮同位素分析和揭示土壤微结构的图像分析等技术的应用是蚯蚓生态功能研究的迫切需要。     

Earthworm populations in conventional and integrated farming systems in the LIFE Project (SW England) in 1990–2000

Dilute formalin was used to sample earthworm populations in a field experiment comparing conventional (CFS) and integrated (IFS) farming systems, at Long Ashton in SW England during 1990–2000. Crops in the CFS were established by ploughing. Those in the IFS treatments were established by non‐inversion tillage: in the first 5 yrs using a Dutzi cultivator or by direct drilling (IFS‐1); from 1994 onwards using either a Vaderstad cultivator (IFS‐2) or a Dutzi cultivator (IFS‐3). These treatments had little or no effect on earthworm populations over the first 3 yrs of the experiment, but after this time total earthworm numbers and biomass were generally greater in the IFS treatments than in the CFS. Individual earthworm species (determined from 1995 onwards) differed in their response to the different farming systems. Numbers of Allolobophora chlorotica, Lumbricus festivus, L. rubellus and L. terrestris averaged over all years were significantly greater in IFS‐3 than in CFS, with densities in IFS‐2 nearly always intermediate and not significantly different from either extreme. Average treatment differences for other species were not significant, although in most years numbers of Aporrectodea longa, Lumbricus castaneus and Octolasion spp. were greatest in IFS‐3, with IFS‐2 similar to or less than CFS. There were no consistent differences between treatments for Aporrectodea caliginosa and A. rosea. Tillage method and the number of crop establishment passes were probably the main factors affecting earthworm populations, although the abundance and distribution of some species may also have been influenced by the amount of soil organic matter. During the period 1995–2000,13 species of earthworms were recorded from the site with A. caliginosa and Al. chlorotica the dominant species. These and other species which normally live in temporary burrows close to the soil surface formed about 80% of the total earthworms extracted, with the larger deep burrowing species, such as A. longa and L. terrestris, representing <20% of the total catch. Species diversity was consistently greater in the Dutzi‐based integrated system (IFS‐3) than in either the Vaderstad‐based integrated system (IFS‐2) or the conventional system (CFS). It is suggested that knowledge of the species composition of earthworm communities is essential in order to properly anticipate the likely impact of modified farming practices on earthworm populations. Careful consideration of the specific machine(s) used for tillage operations may also be required.     

Woodland restoration on agricultural land: long‐term impacts on soil quality

Woodland restoration is underway globally to counter the negative soil quality and ecological impacts of agricultural expansion and woodland fragmentation, and restore or enhance biodiversity, ecosystem functions and services. However, we lack information about the long‐term effects of woodland restoration on agricultural soils, particularly at temporal scales meaningful to woodland and soil development. This study utilized soil and earthworm sampling across a chronosequence of sites transitioning from “agricultural land” to “secondary woodland” (50–110 years) and “ancient woodland” (>400 years), with the goal of quantifying the effects of woodland restoration on agricultural land, on key soil quality parameters (soil bulk density, pH, carbon and nitrogen stocks, and earthworm abundance, biomass, species richness and diversity). Broad‐leaved woodland restoration led to significantly greater soil organic carbon (SOC) stocks compared to arable land, and young (50–60 years) secondary woodland increased earthworm species and functional diversity compared to both arable and pasture agricultural land. SOC stocks in secondary broad‐leaved woodlands (50–110 years) were comparable to those found in long‐term ancient woodlands (>400 years). Our findings show that broad‐leaved woodland restoration of agricultural land can lead to meaningful soil ecological improvement and gains in SOC within 50–110 years, and provide intel on how restoration activities may be best targeted to maximize soil quality and functions.     

Colonization and Recovery of Invertebrate Ecosystem Engineers during Prairie Restoration

Ants (Hymenoptera: Formicidae) and earthworms (Oligochaeta) are considered ecosystem engineers because they form biogenic structures in the soil that influence resource supply. The objectives of this study were to quantify recovery dynamics of these invertebrate groups across a chronosequence of restored prairies and elucidate whether changes in the abundance and biomass of ants and earthworms were related to key plant and ecosystem properties. We sampled ants and earthworms from cultivated fields, grasslands restored from 1 to 21 years, and native prairie. Ant abundance and biomass peaked between 5 and 8 years of restoration and abundance was 198 times greater than cultivated fields. Earthworm abundance increased linearly across the chronosequence and became representative of native prairie, but all earthworm populations were dominated by European species. Ant abundance and biomass were positively correlated with plant diversity and plant richness, whereas earthworm abundance biomass was only related to surface litter. These results demonstrate that earthworm abundance increases with time since cessation of cultivation and concomitant with prairie establishment, whereas the abundance and biomass of ants are more related to the structure of restored plant communities than time. The dominance of exotic earthworms in these restorations, coupled with their capacity to alter soil properties and processes may represent novel conditions for grassland development.     

Earthworm and enchytraeid activity under different arable farming systems,as exemplified by biogenic structures

A study was conducted in order to compare soil faunal activity in four experimental farming systems using different tillage, chemical input and crop rotation practices: A conventional system with deep-ploughing (CT), an integrated system with reduced tillage and minimum chemical input (IN), a system with reduced tillage and high chemical input (RT) and a system with minimum tillage and high chemical input (MT). In nine experimental fields with two sampling points each, earthworms were sampled and biogenic structures were identified and counted in topsoil profiles (0–14 cm depth). Components of these profiles were identified by morphological features. Quantitative analyses of these morphological features provided information about soil compaction, earthworm and enchytraeid activity and distribution of roots and crop residues in the soil matrix. The dominant species in the earthworm community was the endogeic Aporrectodea rosea. Earthworm densities were unexpectedly lowest under reduced tillage (6 specimens per m²), and highest under deep-ploughing (67 specimen per m²), the reverse effect being observed with enchytraeid worms, as ascertained by deposition of their faecal pellets in topsoil profiles. Strong very fine granular structure (STVFGR) was most frequent in the integrated farming system (IN). We concluded that in the studied site embracing four farming systems, enchytraeids play an important role in creating a stable soil structure and porosity at the low level of earthworm densities found in the integrated system (IN). This revised version was published online in June 2006 with corrections to the Cover Date.     

The wave towards a new steady state: effects of earthworm invasion on soil microbial functions

Earthworms are ecosystem engineers that cause a long cascade of ecological effects when they invade previously earthworm-free forests. However, the consequences of earthworm invasion for soil microbial functions are poorly understood. Here, we used two well-studied invasion fronts of European earthworms in northern North American hardwood forests previously devoid of earthworms in order to investigate three stages of earthworm invasion: uninvaded, the front of the leading edge of earthworm invasion and locations invaded at least 10 years previously. Soil microbial biomass, respiration and metabolic quotient were measured. Earthworms had marked effects on soil microbial biomass (−42%) and respiration (−32%). At both sites, impacts were most pronounced at the leading edge of the invasion front, significantly decreasing soil microbial C use efficiency. This was most likely due to the disturbance of the soil microbial community caused by water stress. Based on these results, we hypothesize that effects of earthworm invasion on native soil ecosystem functioning are most pronounced at the peak of the invasion wave. After experiencing this wave, ecosystems possibly enter a new steady state with altered biotic compositions and functions.     

不同蚯蚓采样方法对比研究

蚯蚓种类组成和丰度变化是反映农业管理措施对土壤质量影响的重要指标。为研究利用芥末悬液等方法进行蚯蚓样品采集的有效性和准确性,寻求合理有效的蚯蚓种群特征调查方法,在我国东北玉米连作黑土上分别运用手拣法、福尔马林溶液驱赶法、芥末+水悬液及芥末+乙酸悬液驱赶法,以及驱虫剂与手拣法相结合的方法进行蚯蚓样品采集,将上述7种方法测得的蚯蚓丰度、生物量及年龄组成信息进行了系统分析。结果表明,福尔马林溶液驱赶法不结合手拣法使用时测得的蚯蚓丰度及生物量远远低于其他方法,尤其幼年蚯蚓比例偏低,并不能反映真实的蚯蚓种群特征。使用芥末悬液做驱虫剂有效性明显提高,尤其芥末+乙酸悬液,测得的蚯蚓丰度比手拣法高22.3%。福尔马林溶液结合手拣法后有效性大大提高,测得的蚯蚓丰度和生物量分别是其单独使用时的19.1和9.3倍,但相对其他驱虫剂方法仍高估了成年蚯蚓的比例;芥末+水悬液和芥末+乙酸悬液方法结合手拣法后收集到蚯蚓的数量分别提高了67.8%和89.1%,平均个体重量分别是原来的1.8和1.3倍,说明芥末悬液不会杀死小个体的幼年蚯蚓,但少部分大个体蚯蚓及洞穴不与地表相接的蚯蚓可能并不能被其驱赶至地表,结合手拣法后可以弥补这个缺陷。芥末+乙酸悬液结合手拣法收集到的成年及幼年蚯蚓数量和生物量均显著高于其他方法(P<0.05),既能有效地驱赶小个体和幼年蚯蚓,又可以收集到洞穴不与地表相接的土栖型蚯蚓,因此可以作为真实有效地反映蚯蚓种群特征的采样方法之一。     

The unseen invaders: introduced earthworms as drivers of change in plant communities in North American forests (a meta‐analysis)

Globally, biological invasions can have strong impacts on biodiversity as well as ecosystem functioning. While less conspicuous than introduced aboveground organisms, introduced belowground organisms may have similarly strong effects. Here, we synthesize for the first time the impacts of introduced earthworms on plant diversity and community composition in North American forests. We conducted a meta‐analysis using a total of 645 observations to quantify mean effect sizes of associations between introduced earthworm communities and plant diversity, cover of plant functional groups, and cover of native and non‐native plants. We found that plant diversity significantly declined with increasing richness of introduced earthworm ecological groups. While plant species richness or evenness did not change with earthworm invasion, our results indicate clear changes in plant community composition: cover of graminoids and non‐native plant species significantly increased, and cover of native plant species (of all functional groups) tended to decrease, with increasing earthworm biomass. Overall, these findings support the hypothesis that introduced earthworms facilitate particular plant species adapted to the abiotic conditions of earthworm‐invaded forests. Further, our study provides evidence that introduced earthworms are associated with declines in plant diversity in North American forests. Changing plant functional composition in these forests may have long‐lasting effects on ecosystem functioning.     

Local-scale correlates of native and non-native earthworm distributions in juniper-encroached tallgrass prairie

European and Asian earthworms have invaded much of North America with profound impacts to soils, plant communities, and animal populations. However, few studies have assessed local-scale correlates of earthworm distributions, and most invasive earthworm research has occurred in northern forests. Additionally, despite several studies showing facilitative relationships between invasive earthworms and invasive plants, no research has assessed a potential facilitative interaction between earthworms and woody plants encroaching into prairies. We conducted the first assessment of factors influencing local-scale distributions of native and non-native earthworms for the U.S. Great Plains in a tallgrass prairie-woodland mosaic experiencing eastern redcedar (Juniperus virginiana) encroachment. We documented both native and non-native earthworms, including non-native species from Eurasia (Aporrectodea spp.) and South America (Family Ocnerodrilidae). Native and non-native earthworm distributions were strongly correlated, yet local-scale predictors of distribution also differed between the groups. Native earthworms were more likely to occur near roads and in areas with moist soils. Contrary to expectation, we found no evidence that non-native earthworms occurred more frequently in areas with eastern redcedar-encroachment; instead, non-native earthworms were most likely to occur in tallgrass prairie. Our results suggest that, within prairies and woodlands of the Great Plains, native and non-native earthworms occur most frequently near roadways and in locations with moist soil. Because the few approaches for controlling invasive earthworms are only likely to be feasible on a small scale, findings from such local-scale studies are important for directing management to reduce earthworm impacts on biodiversity and ecosystem services.     

Climate,duration, and N placement determine N2O emissions in reduced tillage systems: a meta‐analysis

No‐tillage and reduced tillage (NT/RT) management practices are being promoted in agroecosystems to reduce erosion, sequester additional soil C and reduce production costs. The impact of NT/RT on N₂O emissions, however, has been variable with both increases and decreases in emissions reported. Herein, we quantitatively synthesize studies on the short‐ and long‐term impact of NT/RT on N₂O emissions in humid and dry climatic zones with emissions expressed on both an area‐ and crop yield‐scaled basis. A meta‐analysis was conducted on 239 direct comparisons between conventional tillage (CT) and NT/RT. In contrast to earlier studies, averaged across all comparisons, NT/RT did not alter N₂O emissions compared with CT. However, NT/RT significantly reduced N₂O emissions in experiments >10 years, especially in dry climates. No significant correlation was found between soil texture and the effect of NT/RT on N₂O emissions. When fertilizer‐N was placed at ≥5 cm depth, NT/RT significantly reduced area‐scaled N₂O emissions, in particular under humid climatic conditions. Compared to CT under dry climatic conditions, yield‐scaled N₂O increased significantly (57%) when NT/RT was implemented <10 years, but decreased significantly (27%) after ≥10 years of NT/RT. There was a significant decrease in yield‐scaled N₂O emissions in humid climates when fertilizer‐N was placed at ≥5 cm depth. Therefore, in humid climates, deep placement of fertilizer‐N is recommended when implementing NT/RT. In addition, NT/RT practices need to be sustained for a prolonged time, particularly in dry climates, to become an effective mitigation strategy for reducing N₂O emissions.     

Ecosystem effects of non-native earthworms in Mid-Atlantic deciduous forests

In many mid-Atlantic forests where both native and non-native earthworms exist, it is the non-native species that are the dominant component of the soil macrofauna. Few earthworm ecology studies, however, focus attention on these forest systems in order to determine the relative ecological roles and potential interactions of the native and non-native earthworms. In a series of field samplings and experimental manipulations we collected data on the effects of earthworms on below-and aboveground ecosystem processes. Earthworm abundance and the ecological processes measured were dynamic in space and time across the range of study sites. Leaf litter decay rates doubled at sites that had abundant non-native earthworms. Earthworms also altered the abundance of soil fungi, the activity of extracellular enzymes, soil respiration, and the growth of tree seedlings but the effects varied among sites depending on differences in land-use history and forest age. Red oak seedling growth was less at sites that had abundant earthworms but tulip poplar and red maple seedlings grew equally well with and without abundant earthworms. These preliminary results suggest that non-native earthworms have significant ecosystem effects, even in forests where native earthworms still occur. Land use history, however, plays an important role in determining what those effects will be, and these effects are likely to be dynamic, depending on the abundance of non-native earthworms.     

蚯蚓在植物修复芘污染土壤中的作用

采用盆栽试验法,研究了蚯蚓(Pheretima hupeiensis)在植物修复芘污染土壤中的作用。结果显示,试验浓度(20.24-321.42 mg/kg) 范围内,蚯蚓活动促进了芘污染土壤中修复植物黑麦草(Lolium multiforum)黑麦草的生长,其根冠比明显增大。添加蚯蚓72 d后,种植黑麦草的土壤中芘的去除率高达60.01%-86.26%,其平均去除率(74.66%)比无蚯蚓活动的土壤-植物系统(64.55%)提高10.11%,比无植物对照组(18.24%)提高56.42%。各种生物、非生物修复因子中,植物-微生物交互作用对芘去除的平均贡献率(51.75%)最为突出,比无蚯蚓活动时(44.94%)提高6.81%。说明蚯蚓活动可强化土壤-植物系统对土壤芘污染的修复作用。     

Working with UK farmers to investigate anecic earthworm middens and soil biophysical properties

The conversion from conventional tillage to no-tillage soil management practices is generally associated with an improvement in aggregate stability and anecic earthworm populations. We worked with UK farmers who measured Lumbricus terrestris midden area (%) and earthworm numbers associated with middens compared to the general soil. They found that middens covered up to 42% of the soil surface. Middened soil (i.e., soil underlying the middens) was associated with significantly more earthworms than the general soil (i.e., non-middened soil) in agreement with research from scientific field trials. We compared the biophysical properties of middened soil to general soil across an experimental field trial recently converted to no-tillage soil management practices. We measured water-stable aggregation, soil porosity at scales relevant to water storage and gas diffusion and invertebrate feeding activity. Middened areas covered up to 13% of the field trial and were associated with significantly improved aggregate stability and porosity compared to the general soil. Our findings highlight the importance of considering middens when surveying soil quality and health in arable systems.     

Exotic earthworms dispersion through protected forest areas and their potential impacts on nitrous oxide production

It is generally accepted that human activities are responsible for the dispersal of exotic earthworms in northeastern North America. We know little, however, about the relative effects of concurrent human activities on the structure of these earthworm communities in protected forest areas, nor on their impacts on soil biological activities. Our first objective was to infer the relative importance of recreational fishing and road traffic on the structure of Lumbricidae communities in Mont-Tremblant National Park, the oldest conservation area in the province of Quebec, Canada. Our second objective was to test the relationship between earthworm species abundances and soil properties related to microbial and nitrogen dynamics. We sampled earthworm communities around 61 lakes, which included 23 heavily-fished lakes and 20 non-fished lakes located near roads, as well as 18 non-fished lakes located in remote areas of the park. Our results revealed that fishing and proximity to roads both have a positive effect on the abundance of earthworms, as does the soil pH. Fishing activities had a greater effect than road proximity on the abundance and diversity of earthworm communities, notably on the abundance of the anecic species Lumbricus terrestris. To assess at a finer scale the effects of earthworm community structure on soil microbial and nitrogen dynamics, we collected and analyzed soils from 47 sampling points around two lakes with high earthworm densities. Exploratory redundancy analysis found a negative correlation between epigeic and anecic earthworm species, with the former correlating positively to microbial biomass and the latter correlating positively to nitrification and denitrification. Confirmatory path analysis established a positive indirect effect of Lumbricus terrestris, the preferred fishing bait, on potential soil nitrous oxide emissions. We conclude that the human-mediated dispersion of earthworms in the most pristine ecosystems of Quebec affects ecosystem functioning and thus requires a review of current policies regarding the use of live-bait by fishermen.     

Seasonal changes of arbuscular mycorrhizal fungi as affected by tillage practices and fertilization : Hyphal density and mycorrhizal root colonization

The influence of tillage practices on native arbuscular mycorrhizal fungi (AMF) was studied in two, consecutive years in eastern Canada, in two 11 year-old long-term tillage-fertilizer experimental field soils, a sandy loam and a clay, growing corn in monoculture. The three tillage practices were: 1) conventional tillage (CT; fall plowing plus spring disking), reduced tillage (RT; spring disking) and no-till (NT). The corn crop received either inorganic (N and K) or organic (liquid dairy manure) fertilizers. Mycorrhizal hyphal density was estimated from soil samples obtained in early spring (before disking), at the 12–14 leaf stage, at silking, and at harvest. The percentage of corn root colonization by AMF at the 12–14 leaf stage, at silking and at harvest was also determined. The sandy loam was sampled over two consecutive seasons and the clay soil over one season.Densities of total and metabolically active soil hyphae, and mycorrhizal root colonization were significantly lower in CT soil than in RT and NT soil. Lowest soil hyphal densities were observed in early spring. The levels of intra- and extraradical fungal colonization always increased from spring to silking and decreased thereafter. Spring disking had only a small and transient negative effect on hyphal abundance in soil. Fertilization did not influence mycorrhizal colonization of corn or abundance of soil hyphae in the sandy loam soil, but in the clay soil metabolically active hyphae were more abundant with manure application than with mineral fertilization. In 1992, in both soils different tillage systems had same grain yield, however, in 1993, corn yield was higher in NT compared to CT system.     

The influence of invasive earthworms on indigenous fauna in ecosystems previously uninhabited by earthworms

Recent studies on earthworm invasion of North American soils report dramatic changes in soil structure, nutrient dynamics and plant communities in ecosystems historically free of earthworms. However, the direct and indirect impacts of earthworm invasions on animals have been largely ignored. This paper summarizes the current knowledge on the impact of earthworm invasion on other soil fauna, vertebrates as well as invertebrates.Earthworm invasions can have positive effects on the abundance of other soil invertebrates, but such effects are often small, transient, and restricted to habitats with harsh climates or a long history of earthworm co-occurrence with other soil invertebrates. Middens and burrows can increase soil heterogeneity and create microhabitats with a larger pore size, high microbial biomass, and microclimates that are attractive to micro- and mesofauna. Under harsh climatic conditions, the aggregates formed by earthworms may increase the stability of soil microclimates. Positive effects can also be seen when comminution and mucus secretion increase the palatability of unpalatable organic material for microorganisms which are the main food of most micro- and mesofaunal groups. For larger invertebrates or small vertebrates, invasive earthworms may become important prey, with the potential to increase resource availability. In the longer-term, the activity of invading earthworms can have a strong negative impact on indigenous faunal groups across multiple trophic levels. Evidence from field and laboratory studies indicates that the restructuring of soil layers, particularly the loss of organic horizons, physical disturbance to the soil, alteration of understory vegetation, and direct competition for food resources, lead directly and indirectly to significant declines in the abundance of soil micro- and mesofauna. Though studies of invasive earthworm impacts on the abundance of larger invertebrates or vertebrates are generally lacking, recent evidence suggests that reduced abundance of small soil fauna and alteration of soil microclimates may be contributing to declines in vertebrate fauna such as terrestrial salamanders. Preliminary evidence also suggests the potential for earthworm invasions to interact with other factors such as soil pollution, to negatively affect vertebrate populations.     

Earthworm invasions of ecosystems devoid of earthworms: effects on soil microbes

Recent studies document North American earthworm invasions and their profound effects on the structure of the soil profile, which is the habitat for soil microorganisms (mainly fungi and bacteria). Dramatic alterations made to these layers during earthworm invasion significantly change microbial community structure and therefore microbial activities such as C transformations. Understanding the impacts of earthworm invasion on the microbes themselves will give insight into earthworm effects on microbial activities. Bacterial and actinomycete communities in earthworm guts and casts have not been studied in environments recently invaded by earthworms. Earthworm invasion tended to decrease fungal species density and fungal species diversity and richness. The presence of earthworms decreased zygomycete species abundance probably due to disruption of fungal hyphae. Physical disruption of hyphae may also explain decreased mycorrhizal colonization rates, decreased mycorrhizal abundance and altered mycorrhizal morphology in the presence of earthworms. Mixing of organic layers into mineral soil during earthworm invasion tended to decrease microbial biomass in forest floor materials while increasing it in mineral soil. In newly invaded forest soils, microbial respiration and the metabolic quotient tended to decline. In forests where either the microbial community has had time to adapt to earthworm activities, or where the destruction of the forest floor is complete, as in invasions by the Asian Amynthas hawayanus, the presence of earthworms tends to increase the metabolic quotient indicating a shift to a smaller, more active microbial community.     

The Effect of Biochar and Its Interaction with the Earthworm Pontoscolex corethrurus on Soil Microbial Community Structure in Tropical Soils

Biochar effects on soil microbial abundance and community structure are keys for understanding the biogeochemical cycling of nutrients and organic matter turnover, but are poorly understood, in particular in tropical areas. We conducted a greenhouse experiment in which we added biochars produced from four different feedstocks [sewage sludge (B1), deinking sewage sludge (B2), Miscanthus (B3) and pine wood (B4)] at a rate of 3% (w/w) to two tropical soils (an Acrisol and a Ferralsol) planted with proso millet (Panicum milliaceum L.). The interactive effect of the addition of earthworms was also addressed. For this purpose we utilized soil samples from pots with or without the earthworm Pontoscolex corethrurus, which is a ubiquitous earthworm in tropical soils. Phospholipid fatty acid (PLFA) measurements showed that biochar type, soil type and the presence of earthworms significantly affected soil microbial community size and structure. In general, biochar addition affected fungal but not bacterial populations. Overall, biochars rich in ash (B1 and B2) resulted in a marked increase in the fungi to bacteria ratio, while this ratio was unaltered after addition of biochars with a high fixed carbon content (B3 and B4). Our study remarked the contrasting effect that both, biochar prepared from different materials and macrofauna, can have on soil microbial community. Such changes might end up with ecosystem-level effects.     

Distribution, prevalence and intensity of earthworm populations in arable land and grassland in Scotland

The earthworms of arable and pasture fields from 100 randomly chosen arable farms were identified and counted and their relationship with soil factors examined. Thirteen species of earthworm were recorded including Lumbricus friendi from Scotland for the first time. The most prevalent and numerous species were Aporrectodea longa, Aporrectodea caliginosa and Lumbricus terrestris. All earthworm species had cosmopolitan distributions apart from Aporrectodea nocturna and Lumbricus festivus which were confined to southern/central Scotland. Four soil characteristics (% moisture, % sand, % organic matter and pH) shared no relationship with species recorded but tillage may have had a detrimental effect on species composition and size of population. It is suggested that the magnitudes of the earthworm populations found, particularly in permanent pasture, were important in maintaining soil structure and fertility, and the spread of the New Zealand flatworm (Artioposthia triangulata), an obligate predator of earthworms, could have a considerable impact on agricultural productivity and wildlife in Scotland.     

Concordance of N bio-indicators: Dandelion and earthworms in a rotational pasture

Earthworms are important soil metabionts indicative of N enrichment in pastures. A rotational pasture in central Nova Scotia was tested for earthworms using chemical extraction followed by excavation and hand sorting in 28 paired micro plots placed in areas with low versus high proportion of the N indicator plant species dandelion (Taraxacum officinale). Species richness was low with five earthworm species of the Lumbricidae recovered in the following order of abundance: Lumbricus rubellus, Lumbricus terrestris, Aporrectodea turgida, Aporrectodea tuberculata, and Aporrectodea trapezoides. All species occurred at high constancy except the rare A. trapezoides. The inventory revealed spatial differentiation of earthworm abundance and community structure at the field level. High proportion of dandelion reduced pasture sward biomass while abundance of L. rubellus and A. tuberculata significantly (p < 0.05) increased with a concomitant increase in epigeic earthworm dominance at the expense of the anecic L. terrestris. Thus, low cost and non-destructive floristic surveys of N indicators, such as dandelion, allow for concordant inferences about the environmental impact of intensive cow pasture on earthworms and ecosystem function. High earthworm counts may run contrary to the notion of ecological integrity depending on specific earthworm abundances. Reduced earthworm benefits due to any de-intensification of rotational pasture must be assessed against increased risks of N-leaching in intensive pastures with high proportion of dandelion.