Vulnerability of soil invertebrate communities to the influences of livestock in three grasslands

Soil invertebrates are coming under increasing pressure as pastoral agriculture is intensified. Grazing livestock affects the soil invertebrate community by impacting on the physical habitat through treading, and on nutrient cycling through dung and urine return. In this study the sensitivity of soil invertebrates to livestock was examined by quantifying the abundance and diversity of invertebrates in the grazed pasture and comparing it with those under adjacent permanent fence lines on three different soil types at three locations. Resilience of the invertebrate communities was also explored by sampling mown, fertilised and irrigated plots within grazed pastures, where livestock had been excluded for the previous three years.Of the soil invertebrates the predatory and omnivorous nematodes, Oribatida and predatory macrofauna were the most sensitive to grazing livestock. In comparison, earthworms with their higher mobility and ability to burrow were more resistant to livestock. The combined effect of removing treading pressure and moisture stress in the fenced plots appeared to be the major factors influencing invertebrate recovery, rather than the quantity and quality of food entering the soil food-web as influenced by fertiliser application. Earthworms, exhibited the greatest resilience, doubling in abundance in the mown and irrigated plots. Nematodes were more resilient than the larger and longer-lived Oribatida. The oribatid community in the irrigated and mown plots were limited in both diversity and abundance in comparison to the community under the fence line. That the vulnerability of soil invertebrates to livestock treading was consistent at all three sites would suggest that organism characteristics (i.e., life-history and ability to move through the soil) and trophic interactions are important in structuring the biological community.

► Invertebrates sensitive to livestock treading included predatory and omnivorous nematodes, Oribatida and predatory macrofauna.
► Earthworms, with their ability to burrow, appeared more resistant to treading pressure and exhibited the greatest resilience.
► The vulnerability of soil invertebrates to livestock treading was consistent at all three sites.