Above-Ground Primary Production of Chalk Grassland Allowing for Leaf Death

Abstract

Measurements were made to determine the life-span of leaves of 5 common chalkland grasses: Arrhenatherum elatius, Dactylis glomerata, Festuca rubra, Helictotrichon pratense and H. pubescens. Survival time varied from 6 wk to 6 mo., depending on species and time of year. Probit transformation straightened the survivorship curves obtained from sets of leaves marked on the same occasion. Rates of leaf death could then be described as a function of temperature and the time to 50% death estimated for field conditions. Application of turnover time to harvest data raised the estimate of net aboveground production to 691 g m-2 yr-1 (13,320 kJ m-2 yr-1). This figure was less than the maximum recorded biomass, living and dead (773 g m-2 yr-1), but 2.1 times higher than the sum of species increase in living biomass (332 g m-2 yr-1). Results from other studies confirm that the determination of biomass turnover is necessary for the correct estimation of primary production by harvest methods.