The Effects of Sheep Stocking Intensity on the Abundance and Distribution of Mesofauna in Pastures

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Abstract
Collembola and Acarina populations in pastures that were grazed continuously with sheep at 3 stocking intensities were sampled at 6-wk intervals over 2 yr. Enchytraeids and nematodes were sampled on 4 occasions. Increased sheep numbers severely reduced the numbers of Collembola, particularly the surface dwellers (0-5 cm). Smaller stocking rate effects were observed for Acarina, enchytraeids and nematodes in that order. Changes in mesofaunal abundance were related to changes in herbage, litter, roots, soil pore space and soil temperature. Differences in soil temperature between the stocking treatments at any point of time were not sufficiently large to account for the large differences in mesofaunal numbers. It appears that these were related to biotic factors in the environment, such as the amount of living space in the soil and litter mat, shelter and food. Seasonal differences in abundance occurred for all groups. Consistent rhythms in numbers were observed for Collembola and Acarina; peak numbers occurred in late summer for Collembola and in winter for Acarina.