Soil dwelling macro-invertebrates in intensively grazed dairy pastures in Pennsylvania, New York and Vermont

This study estimates the relative contributions of environment and farm man agement strategies in influencing soil faunal assemblages and attempts tl, identify the species with potential to affect sustainability of intensive g razing management systems in the north-eastern USA. it arises because of th e change from confinement feeding of daily cattle, consequent upon concerns about negative environmental effects, the rising costs for machinery and h ousing, and reduced profit margins, together with the absence of data from which the consequences of such change on thc soil fauna may be predicted. Macro-invertebrates we-re sampled in soil from seventy-eight grazed pasture s on twenty-one dairy farms in Pennsylvania, USA, in the spring of 1994. On five of these farms, macro-invertebrates were sampled (four pastures per f arm) in the spring, summer and autumn seasons of 1994, 1995 and 1996. In 19 97, macroinvertebrates were Sampled in sail during spring, summer and autum n from (four pastures per farm) on three farms in New York, and during spri ng and summer on three farms in Vermont. Species richness ranged from two t o twelve species (mean 6.4) per pasture site in Pennsylvania and Ave to eig hteen species (mean 10.7) in New York and Vermont. The communities were dom inated at most sites by earthworms. Earthworms were correlated with soil ba sal and substrate-induced respiration/carbon ratio, and soil moisture, bur were negatively correlated with cows per hectare and herbage biomass in Pen nsylvania. Sitona larvae were recorded at nineteen of the twenty-one farms during the spring of 1994 across Pennsylvania and occurred at populations > 5 m(-2) in 68% of the sampled pastures. Sitona larvae were less abundant in New York and Vermont. Elaterid larvae comprised a complex of seven species of which Aeolus melillus (Say) and Melanotus communis (Gyllenhal) comprise d 35% and 39%, respectively, of the elaterids collected in Pennsylvania. Ag riotes mancus (Say) and Ctenicera destructor (Brown) comprised 41% and 26%, respectively, of four species collected in New York and Vermont. Scarabaei d larvae, comprising a complex of fight species, were detected at only 27% of the seventy-eight pastures sampled in spring 1994 in Pennsylvania. Five species were collected in ten of the twelve New York pastures and lour spec ies in nine of the twelve Vermont pastures. Populations of scarabaeid larva e averaged <25 m(-2) in all three states, except in three Pennsylvania past ures in spring 1994. Detrended canonical correspondence analysis (DCCA) sho wed pasture standing biomass, legume diversity, pre-winter stubble height, white clover pasture content, and soil phosphorus levels influenced numbers of invertebrate species more than climatic factors, such as temperature, r ainfall, altitude, latitude and seasonal water table. DCCA also showed most pastures to be close to the average of environmental factors. The extremel y low density of herbivorous macro-invertebrates in soil and the absence of pest outbreaks may indicate a stable soil ecosystem.