Environment-induced modifications to root longevity in Lolium perenne and Trifolium repens

Understanding how environmental factors affect the longevity of roots is es sential if root mortality linked nutrient cycling processes within ecosyste ms are to be understood, and the impact of natural and anthropogenic climat e change properly evaluated. In this study the longevity of roots at two ge ographically and climatically distinct sites were compared to identify the scale of change that can occur due to environmental differences. Minirhizot ron tubes were inserted into swards sown with the same variety of Lolium pe renne and Trifolium repens at sites in the UK and Italy. Roots were viewed using a video camera and digitized images of roots generated at intervals. From these images the life history of individual roots was determined and c ompared. There were few differences in patterns of longevity between differ ent species at the same site. Major differences, however, were observed bet ween roots of the same species at different sites. For example, 73% of Trif olium repens roots failed to survive for 21 d in Italy compared to only 29% at the UK site. Similarly, over 84% of Lolium perenne roots failed to surv ive for more than 21 d in Italy compared to 38% in the UK. These data sugge st that environmental factors can have a major impact on root longevity. (C ) 2000 Annals of Botany Company.