Response of endemic and exotic earthworm communities to ecological restoration (original) (raw)
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Native and exotic earthworms and plants co-exist on the margins of agricultural land in New Zealand. Remnants of native vegetation support mixed assemblages of depleted populations of native Megascolecid earthworms together with apparently increasing invasive populations of introduced Lumbricidae. We question whether the survival and viability of these earthworm populations is a function of soil preference and whether there are significant differences in terms of how the two groups are influenced by and modify soil properties and plant growth. Choice chamber and mesocosm experiments, with and without plant rhizospheres, were used to study five species of native earthworms, two of which could be identified only by DNA barcoding, and four introduced exotic species. Both natives and exotics preferred agricultural soils to a plantation forest and a native forest soil. Earthworms also modified the physico-chemistry of soils and greenhouse gas emissions, with a marked interaction with root morphology of two native species of tea tree. Lesser differences were found between native and exotic earthworms than between functional groups. It is concluded that New Zealand’s production landscapes provide novel habitats with clear benefits both to threatened species conservation and to soil ecosystem services.
Caribbean Journal of …, 2006
Populations of some native earthworm species are decreasing or disappearing due to human activities like habitat disturbance and introduction of exotic earthworms. Habitat disturbance can cause changes in soil physical structure and nutrient cycling, which may reduce native earthworm populations prior to the invasion of exotic earthworms. Our purpose was 1) to investigate habitat disturbance as a key process in the decline or extirpation of native earthworms, and 2) to measure the ability of native earthworms to re-colonize disturbed areas. We hypothesized that habitat disturbance will reduce the population of native earthworms and impede their re-colonization in those perturbed areas. We set up 48 soil mesocosms in three field sites representing different degrees of disturbance (abandoned pasture, young and mature forests) in the Cayey Mountains of Puerto Rico. Three individuals of the native earthworm, Estherella spp., were inoculated into each soil core to evaluate their re-colonization ability by measuring survivorship, growth rates and reproduction. We found that, in the absence of exotic earthworm species, the survivorship and growth rates of Estherella spp. in the pasture was not significantly different than that from young and mature forests during the first six months of re-colonization process. Our results suggest that habitat disturbance (changes in vegetation and soil properties) may not have significant influences on native earthworm (Estherella spp.) populations. We propose that biotic factors, such as competitive exclusion of native earthworms by exotic earthworms, may have considerable effects on retarding their re-colonization and/or causing the disappearance of native earthworm population in disturbed areas.
Caribbean Journal of Science, 2006
Populations of some native earthworm species are decreasing or disappearing due to human activities like habitat disturbance and introduction of exotic earthworms. Habitat disturbance can cause changes in soil physical structure and nutrient cycling, which may reduce native earthworm populations prior to the invasion of exotic earthworms. Our purpose was 1) to investigate habitat disturbance as a key process in the decline or extirpation of native earthworms, and 2) to measure the ability of native earthworms to re-colonize disturbed areas. We hypothesized that habitat disturbance will reduce the population of native earthworms and impede their re-colonization in those perturbed areas. We set up 48 soil mesocosms in three field sites representing different degrees of disturbance (abandoned pasture, young and mature forests) in the Cayey Mountains of Puerto Rico. Three individuals of the native earthworm, Estherella spp., were inoculated into each soil core to evaluate their re-colonization ability by measuring survivorship, growth rates and reproduction. We found that, in the absence of exotic earthworm species, the survivorship and growth rates of Estherella spp. in the pasture was not significantly different than that from young and mature forests during the first six months of re-colonization process. Our results suggest that habitat disturbance (changes in vegetation and soil properties) may not have significant influences on native earthworm (Estherella spp.) populations. We propose that biotic factors, such as competitive exclusion of native earthworms by exotic earthworms, may have considerable effects on retarding their re-colonization and/or causing the disappearance of native earthworm population in disturbed areas.
Recovery of Native Earthworms in Abandoned Tropical Pastures
Conservation Biology, 2003
Regeneration of secondary forests is recognized as an important means for the recovery of native species biodiversity in human-disturbed tropical lands. Native earthworms are often replaced with exotic species after deforestation. We studied changes in earthworm diversity and community structure along a chronosequence of abandoned tropical pastures in the Cayey Mountains of Puerto Rico. This chronosequence consisted of active pastures, young secondary forests 25-40 years old, and mature secondary forests Ͼ 77 years old. Earthworm diversity increased along successional stages. The exotic soil-feeding earthworm Pontoscolex corethrurus dominated the pastures and young secondary forests. Five native earthworm species ( litter feeders Borgesia sedecimsetae , Estherella sp., Onychochaeta borincana , Neotrigaster rufa , and Trigaster longissimus ) were found in the mature forests, together with P. corethrurus . Earthworm density was highest in the active pastures (273 individuals/m 2 ), decreased as forest regeneration proceeded, and was lowest in the mature forests (88 individuals/m 2 ). Our results suggest that regeneration of mature secondary forests, and the consequent increase in litter biomass on the forest floor, can promote the recovery of earthworm diversity and native species of earthworms in old tropical pastures.
Invasion of exotic earthworms into ecosystems inhabited by native earthworms
Biological Invasions, 2006
The most conspicuous biological invasions in terrestrial ecosystems have been by exotic plants, insects and vertebrates. Invasions by exotic earthworms, although not as well studied, may be increasing with global commerce in agriculture, waste management and bioremediation. A number of cases has documented where invasive earthworms have caused significant changes in soil profiles, nutrient and organic matter dynamics, other soil organisms or plant communities. Most of these cases are in areas that have been disturbed (e.g., agricultural systems) or were previously devoid of earthworms (e.g., north of Pleistocene glacial margins). It is not clear that such effects are common in ecosystems inhabited by native earthworms, especially where soils are undisturbed. We explore the idea that indigenous earthworm fauna and/or characteristics of their
Forestry Research and Engineering: International Journal
Consequences of deforestation arise from site degradation leading to modification of soil properties this significantly affect both incidence and abundance of soil macro fauna. Earthworm communities are more directly altered by these changes. Endemic and exotic species co-existed in the study area following deforestation and intensive cultivation. That native species were dominant in the undisturbed sites and disturbance and degradations leads to invasion by the exotic species holds true in our study. The sites under study represented the degraded areas as none of the species reported from the present experimental plots were endemic to the region, all the species are either peregrine exotic or peregrine endemic to the area as many of the endemic species of this region probably exterminated during the last Quaternary Glaciation. The numbers of species present at our sites ranged between 2 to 5. The presence of litter layer and lower perturbation pressure resulted in the numerical dominance of Lennogaster pussilus in the Oak forest (OF) and the higher biomass of A. alexandri may be because of the larger size of the earthworm. B parvus, L. pussilus and P. excavatus are litter-associated taxa which were more directly affected by OF clearance and the resulting decrease in available litter, thus explaining their disappearance in the changed ecosystems, however improved soil moisture and temperature as well as input of organic matter in rehabilitated agricultural land (RAL) could probably be favourable factor for decolonization and dominance of L. pussilus. A. alexandri had wider ecological amplitude occurring under all land use types as reported in our studies, conversion of two other land use types resulted in lower species diversity. Our results show that the abandoned agriculture land (AAL) remains closer to the AL(T) than to the forest because in these land use types the overall vegetation diversity remains low corresponding to a low diversification of the organic resources thus explaining the similarity between the earthworm communities in land use types. Seasonal rhythmic pattern was exhibited by all the species identified.
Soil Biology and Biochemistry, 1992
Earthworms were surveyed in 113 pasture soils in the Mount Lofty Ranges, Fleurieu Peninsula, South Australia, in a region where annual rainfall is 600-1200 mm and the climate is mediterranean. The soils within these pastures included a variety of profile forms (e.g. sandy soils with yellow, brown or red clays in the B horizon; uniform coarse textured sands). The most widespread earthworm species were Aporrecrodea trapezoides (found at 95% of sites), Microscolex dubius (61%). Aporrectodea rosea (38%) and Aporrectodea culiginosu (36%). These are all introduced species. The total densities of earthworms varied from 0 to 608 me2 (mean = 169.2). At most sites (66%). densities were ~200 m-*. Native earthworms were present at 40 sites but their total densities exceeded 100 m-* at only 7 sites. The species richness and diversity of the earthworm communities were low; never more than 5 species were found in any one pasture (mean = 3.1). The abundance of the introduced species (all species combined) varied between soil prolile forms, being least in the uniform sands. No such variation was found for native species. Several significant, but weak, correlations were obtained between the numbers and weights of earthworms and other environmental variables (e.g. rainfall, depth of A horizon, % sand, clay. nitrogen and carbon). Stepwise multiple regression of the numbers and weights of introduced species against these environmental variables suggested that % clay was the most important regressor. The potential for increasing the abundance and diversity of earthworms in Australian soils is discussed.
EARTHWORM DIVERSITY AND ECOSYSTEM SERVICES UNDER THREAT
ABSTRACT Biodiversity affects human well-being and represents an essential determinant of ecosystem stability. However, the importance of below-ground biodiversity, and earthworm biodiversity in particular, has not received much attention. Earthworms represent the most important group of soil macrofauna. They play a crucial role in various biological processes in soil, and affect ecosystem services such as soil health and productivity, water regulation, restoration of degraded lands, and the balance of greenhouse gases. Anthropogenic activities can lead to a rapid reduction or loss of earthworm diversity, and threaten ecosystem services as well as human well-being. Therefore, conservation of earthworm diversity should receive urgent attention. Farmers need to be made aware of the importance of earthworm diversity conservation and its benefits. Local ecological knowledge is required for communication between scientists and farmers; moreover, efficient strategies for earthworm diversity conservation need to be developed. This paper intends to communicate the importance of earthworm diversity conservation. Development of conservation management to prevent earthworm diversity decline should be done wisely and involve all stakeholders. Keywords:Earthworm, Diversity, Ecosystem services, Threat
Diversity and abundance of earthworms across an agricultural land-use intensity gradient
Soil & Tillage Research, 2008
Understanding how communities of important soil invertebrates vary with land use may lead to the development of more sustainable land-use strategies. We assessed the abundance and species composition of earthworm communities across six replicated long-term experimental ecosystems that span a gradient in agricultural land-use intensity. The experimental systems include a conventional rowcrop agricultural system, two lower-intensity row-crop systems (no-till and tilled organic input), an early successional old-field system, a 40-60 years old coniferous forest plantation, and an old-growth deciduous forest system. Earthworm populations varied among systems; they were lowest in the most intensively managed row-crop system (107 m À2) and coniferous forest (160 m À2); intermediate in the old-field (273 m À2), no-till (328 m À2) and tilled organic (344 m À2) cropping systems; and highest in the old-growth deciduous forest system (701 m À2). Juvenile Aporrectodea species were the most common earthworms encountered in intensively managed systems; other species made up a larger proportion of the community in less intensively managed systems. Earthworm community biomass and species richness also varied and were lowest in the conventional row-crop system and greatest in the old-growth forest system. These results suggest that both land-use intensity and land-use type are strong drivers of the abundance and composition of earthworm communities in agricultural ecosystems.