Leaf and root turnover of three ecologically contrasting grass species in relation to their performance along a productivity gradient

We tested the hypothesis that species characteristic of nutrient rich sites always grow faster than species from nutrient poor sites, but have a shorter organ life span. It has been suggested that this fast tissue turnover may limit their performance at nutrient poor sites. Three ecologically contrasting grasses were studied: Bromus erectus, characteristic of nutrient poor meadows, and Arrhenatherum elatius and Dactylis glomerata, characteristic of more nutrient rich grasslands. These species were grown at three meadows differing in nutrient availability and harvested 3, 7, 9.5 and 11 months after germination. D. glomerata produced at all sites the largest total biomass. B, erectus showed the lowest growth response to site conditions. D. glomerata and A. elatius had a faster leaf turnover than B, erectus. D, glomerata had a faster root turnover than B. erectus. Root turnover of A. elatius was probably also faster than that of B. erectus, but this was partially obscured by decomposition of dead roots. D. glomerata and A. elatius had a lower tissue density of leaves and roots than B. erectus. We conclude that there is a negative correlation between the plant's ability to increase its growth with increasing nutrient availability and the tissue life span. Nutrient losses due to fast tissue turnover may prevent the dominance of fast-growing species at nutrient poor sites, although these species are in general better at nutrient acquisition. The negative correlation between growth rate and tissue longevity is to a large extent a result of constraints caused by plant tissue structure.