Diversity Of Soil Invertebrates Research Articles

Changes in the community structure and diversity of soil invertebrates across the Franz Josef Glacier chronosequence

Following the creation of new land surfaces, there is an initial build-up phase of ecosystem development, but after a prolonged absence of major disturbance a retrogressive (decline) phase often follows due to reduced nutrient availability over time. Although many studies have considered how the soil community changes during the build-up phase, the response of this community to the retrogressive phase is poorly known. We measured litter and soil communities of microfauna and macrofauna along the Franz Josef Glacier chronosequence in New Zealand that spans ca. 120,000 years, and includes well-established build-up and retrogressive stages. We aimed to assess whether the abundances, community structure and diversity of these groups show the same pattern across the sequence as that for vegetation. With regard to microfaunal abundances, litter-dwelling microbe-feeding nematodes were most abundant in the first stage of the chronosequence, but several other groups of microfauna in both the soil and litter increased sharply during the first few stages and declined sharply during the last (retrogressive) stages. The ratios of bacterial- to fungal-feeding nematodes in both soil and litter were lowest for the final stages of the chronosequence, and (in the case of soil) for some of the early stages, pointing to domination by the fungal-based energy channel at those stages for which soil organic matter content or quality were lowest. This is consistent with the fungal-based energy channel being better adapted than the bacterial-based channel for resource-poor conditions. The main groups of macroinvertebrates typically had their lowest abundances at the very early and late stages of the chronosequence, although the relative abundances of different taxa differed during the intermediate stages. Taxonomic diversity of nematodes and macroinvertebrates in both litter and soil varied strongly with chronosequence stage but differed among taxa; diversity of only one group (macroinvertebrates in litter) declined significantly during retrogression. Diversity of nematodes and macroinvertebrates along the sequence did not closely match tree diversity or soil chemical properties, but community composition of these groups was often related to tree community composition and ratios of soil C to N, C to P and N to P. Different groups of soil invertebrates show contrasting responses to chronosequence stage, probably because they differ in their relative response to bottom-up and top-down controls. However, the abundance of most groups increased during the build-up phase and declined during retrogression. As such, the build-up and decline phases observed for plant communities and ecosystem processes across long-term chronosequences also apply to soil communities, pointing to the importance of resource availability as a major driver of soil biota during long-term ecosystem change.

Earthworm populations sampled using collection methods in atlantic forests with Araucaria angustifolia

Araucaria angustifolia, also known as the Paraná Pine is an endangered tree species in Brazil and little is known of the diversity of soil invertebrates inhabiting these forests. Therefore, the present study was set up to evaluate the biomass and diversity of earthworms in natural and reforested Araucaria plots, impacted or not by fire, and to identify the most efficient earthworm collection method. Four study areas included: native forest with Araucaria (NF); Araucaria reforestation (R); Araucaria reforestation submitted to an accidental fire (RF); and native grass pasture with native Araucaria and submitted to an intense accidental fire (NPF). Five soil samples containing the earthworm community were taken in a 0.3 ha area in each of the forest sites, close to five Araucaria trees selected at random. Three collection methods were tested: application of dilute Formol (0.5%) to the soil surface, handsorting of small (25 <FONT FACE=Symbol>´</FONT> 25 cm) or large (40<FONT FACE=Symbol>´</FONT> 40 cm) monoliths. Five earthworm species were found: the native Glossoscolex sp.1, Glossoscolex sp.2, Glossoscolex bondari and Urobenus brasiliensis (Glossoscolecidae), and the exotic Amynthas corticis (Megascolecidae). Formol was more efficient for collecting A. corticis, found in much higher abundance and biomass in NF than in the other areas. Larger handsorted samples were more efficient for capturing Glossoscolex species, mainly present in RF and NPF. For adequate characterization of earthworm abundance and biomass in these Araucaria forests, both the Formol and the larger monolith methods are recommended.

Invertebrate Diversity under Artificial Cover in Relation to Boreal Forest Habitat Characteristics

We investigated invertebrate diversity in boreal forests using an experimental design that consisted of counting soil invertebrates under artificial cover. The aim was to assess the utility of using soil invertebrate diversity as a measure of ecosystem health. The study area was grouped into five habitats: upland hardwood, lowland hardwood, conifer, shrub, and conifergrass. Simpson’s and Shannon’s indices of invertebrate diversity were negatively correlated with percent herbaceous cover. Number of recognizable taxonomic units (RTU richness) was negatively correlated with percent litter cover. The number of individual invertebrates was positively correlated with soil moisture and negatively correlated with percent conifer cover. Invertebrate diversity varied among habitat types, with conifer forests (spruce, fir, pine) having the highest diversity and regenerating conifer-grass forests having the lowest diversity, suggesting that successional stages affect diversity. The most productive sites, upland and lowland hardwood habitats, had the highest abundance of soil invertebrates, although intermediate diversity compared to the other five habitats. The results are consistent with the view that diversity increases and then decreases with productivity and disturbance over succession (ca. 50-100 yr). Hence, maintenance of soil invertebrate diversity in managed boreal forests requires the provision of a varied landscape with a mosaic of disturbance regimes.

Effects of Coarse Woody Debris and Soil Depth on the Density and Diversity of Soil Invertebrates on Clearcut and Forested Sites on the Olympic Peninsula, Washington

Arthropod density and species richness were determined using high-gradient extraction for soil on clearcut and late successional forests on the Olympic Peninsula, WA. Study objectives were to compare the effects of harvesting at different soil depths and distances from coarse woody debris. Canonical correspondence analysis (CCA) was used to determine the effects of soil moisture, CO2 evolution, and 0 and A horizon depth on species composition. Soil depth had a greater effect on changes in density than did distance to woody debris. Densities of Acari, as well as total species richness, were significantly higher at 0–5 cm depths than at 5–10 cm despite significantly lower moisture content at the soil surface. Density of Acari and Coleoptera and species richness were significantly higher on forested sites than on clearcuts. There was a trend toward higher Collembolan density on clearcuts, but the difference was not significant because of the very different responses on dry and wet clearcuts sites. The results of CCA suggests moisture and O and A horizon depths were the most important quantitative environmental factors we measured in determining differences in species composition. Clearcutting appeared to have site specific-effects on wet and dry site locations. Low moisture and temperature extremes did not appear to limit microarthropod density. High rainfall accentuated by clearcutting was associated with lower O and A horizon depths and appeared to decrease Collembola and Coleoptera density on the wet clearcut.

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

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