The Effects of Removing Sheep Grazing on Soil Chemistry, Above-Ground Nutrient Distribution, and Selected Aspects of Soil Fertility in Long-Term Experiments at Moor House National Nature Reserve

Abstract

(1) Selected aspects of soil chemistry and the distribution of nutrients in above-ground vegetation were measured in grazed and ungrazed plots in eight long-term experiments at Moor House N.N.R. Soil fertility was also estimated by measuring growth and nutrient uptake of test species under standard conditions, and by measuring under laboratory conditions the uptake of 32P by roots of selected species excavated from these plots. (2) There were no consistent trends in soil chemistry between grazed and ungrazed plots, with some ungrazed plots becoming more acidic, and others less so. (3) An increase in both dry matter and nutrient content of the litter component was found at most sites. Principal component analysis of these data showed that at some sites the litter had much smaller amounts of calcium and phosphorus in ungrazed plots, suggesting differential mechanisms of element cycling at these sites. (4) Plant growth bioassays showed differences between sites, but not between grazed and ungrazed plots. Plant growth was correlated with phosphorus rather than nitrogen or potassium uptake. (5) The 32P root uptake bioassays generally showed an inverse ranking with site productivity, although there were two exceptions. Only four out of twelve grazed vs. ungrazed contrasts gave significant results, three having a lower and one a greater phosphorus supply in the ungrazed plots. This technique showed some promise for rapid productivity assessment of upland areas. (6) Generally, most measures ranked sites in order of both productivity and grazing pressure, and differences between grazed and ungrazed plots were greatest on productive sites.