THE DEMOGRAPHY OF FINE ROOTS IN A NORTHERN HARDWOOD FOREST

The production, development, and mortality of fine roots in a northern hardwood forest was monitored for 1 yr using minirhizotrons. Roots were divided into two strata based upon their depth in the soil, < 30 cm and > 30 cm. Cohort analyses of roots produced in the spring of 1989 revealed that while almost 50% of fine roots at both depths survived after 346 d, the number of white roots in each cohort declined very rapidly. Virtually all roots had turned brown after 346 d. The probability of a surviving white root turning brown was much greater than the probability that it would die at all times of the year, and the bulk of root mortality was accounted for by brown roots. Analysis of root length production and mortality showed that total annual length mortality at the < 30 cm depth was 76% of the initial standing crop and 110% at > 30 cm depth. Fine root production and mortality occurred simultaneously throughout the year, and production was slightly greater than mortality at both depths. Total root length peaked in the summer at both depths, and overwinter production and mortality was rather low. Production of white and brown root length indicated that roots near the soil surface were undergoing much more rapid rates of browning than deep roots. Loss of root length between sampling dates was largely due to roots that died and rapidly decayed or otherwise disappeared.