Estimating Fine Root Production And Mortality In Subtropical Altingia Grlilipes And Castanopsis Carlesii Forests

The turnover of fine root, the most dynamic component of root system, play an important role in nutrient cycle and energy flow in forest ecosystems. Fine root production, mortality and biomass in two subtropical evergreen broadleaved forests, Altingia grlilipes forest (ALG) and Castanopsis carlesii forest (CAC), in Wanmulin Natural Reserve, Jian-ou, Fujian province, were monitored for more than three consecutive years by using both minirhizotrons and the exvacation methods. Annual fine root production in ALG (186.3±66.7g·m-2·yr-1) were slightly higher than those in CAC (170.5±82.9g·m-2·yr-1). While annual fine root mortality in ALG (153.0±64.2g·m-2·yr-1) were appreciably lower than those in CAC (164.1±84.6g·m-2·yr-1). The fine root biomass in ALG (122.6±52.4g·m-2) was higher than those in CAC (85.5±50.3g·m-2). The reason which caused the differences of fine root production, fine root mortality and fine root biomass between two forest communities was mainly in both tree species and environmental factors. Fine root production, mortality, and biomass were all seasonal dynamics, that fine root production was mainly in spring and fine root mortality was mainly in spring and autumn in both two communities. The fine root production and mortality of these two forest communities appeared mainly in the top soil layer (0-40cm), accounting for above90%of the total production, respectively. From which distribution in root diameter were mainly in0-1mm, and first root order was all higher than those of the higher order in both two communites. The turnover rate of fine root in ALG was1.38a-1, which was lower than that of CAC (1.96a-1). Root turnover rate was maximum in the first year (2008-2009) and similar in the latter two year in both two communites. With the soil depth increased, fine root turnover rate decreased in CAC, while that had no corresponding tendency in ALG which the most quickly of fine root turnover rate appeared in surface layer and the most slowly of that was in soil depth20-40cm. Among0-1mm root diameter, with the root diameter increased, root turnover rate was decreased in CAC, and root turnover rate in ALG was0.3-0.6mm>0-0.3mm>0.6-lmm.