Incorporation of (15)N from spiked cattle dung pats into soil under two moorland plant communities

The rate and depth of cattle dung incorporation into moorland soil may be an important factor influencing plant community dynamics through its effects on soil nutrient availability. This study traces the incorporation of (15)N-labelled dung into a moorland soil under two vegetation types in Dartmoor National Park, UK. Cores of treated and control soil 10 cm deep were collected at 2, 4, 8 and 16 week intervals and divided into 2 cm depth increments. Soil samples were freeze-dried, ground and analysed for atom% (15)N and %N content using continuous-flow isotope-ratio mass spectrometry. The contribution of dung N to the soil N pool was estimated by changes in atom% (15)N of the soil. The incorporation of dung dry matter into the soil was also calculated. The labile component of the dung N was incorporated deeper and more rapidly into soil under grass than under heather vegetation. The implications of these processes for the dynamics of upland plant communities are considered in relation to the ability of plants to compete for nutrients.