Patterns of fine root mortality in two sugar maple forests

Abstract

MUCH of the carbon assimilated by plants is allocated to fine root production^1–5, and the amount of carbon and nutrients subsequently returned to the soil from fine root turnover equals or surpasses that returned through leaf litter in many forests^6–9. Unfortunately, limitations in traditional methods of studying roots have prevented us from thoroughly understanding the dynamic nature of fine root mortality in most forests, and better measurements of fine root longevity are needed to quantify and model more accurately ecosystem carbon and nutrient budgets^8–11. We used minirhizotrons^12,13 to follow the mortality of contemporaneous fine root cohorts in two sugar maple (Acer saccharum Marsh.) forests located 80 km apart (north–south) during 1989 and 1990. We report here that roots in the northern forest consistently lived the longest, principally owing to greater rates of mortality early in the life of roots at the southern site. Differences in site factors suggest that warmer soil temperatures seem to be associated with the more rapid death of roots at the southern site.