Studies on primary production, nutrients and decomposition in a mown grassland ecosystem

Abstract

The effects of mowing intensity and cessation of mowing on ecosystem structure and function in a semi-permanent grassland are studied, with particular application to amenity grasslands. Intensive mowing leads to increased investment in below-ground plant components in the second year after commencement of mowing. Large production following cessation of mowing leads to large surface accumulations of litter which limit grasses but favour the proliferation of forbs. Litter decomposition rates are strongly influenced by a combination of repeated wetting and drying and faunal activity.
Seasonal biomass dynamics of vegetation components are examined. Fluctuations of N, P, K, Ca, Mg, Na, Mn and Zn concentrations vary between plant components and according to mowing regime and are related to dry matter fluctuations. Nutrients are poorly conserved by grass communities and less than 5% of total ecosystem nutrients are contained within the vegetation, and less than 1% per annum are removed by mowing.
Below-ground components are studied in detail, as roots, rhizomes and a detached root fraction. The root system is categorized and its turnover and contribution to the detritus is considered. Earthworm studies indicate that populations are not enhanced by surface litter accumulations, although their activities can decrease root production without impeding aerial production and affect breakdown of below-ground components.