Fine root dynamics and turnover rate in an Asia white birch forest of Donglingshan Mountain, China

Abstract

Fine root dynamics and turnover rate were studied by sequential soil coring method in a 60-year-old Asia white birch ( Betula platyphylla) forest of Donglingshan Mountain, China. Biomass and necromass of both the finest (<1 mm) and very fine (1–2 mm) roots in 0–55 cm soil layer were determined every month from April to October 2006. The ratio of necromass to biomass, production, mortality, disappearance and turnover rate of both the finest and very fine roots in 0–55 cm soil layer were estimated. Some dynamics of biomass and production of both the finest and very fine roots were explained by meteorological conditions. Biomass, necromass, ratio of necromass to biomass, production, mortality and disappearance of both the finest and very fine roots greatly varied during the growing season. Biomass and production of both the finest and very fine roots decreased from May to June, probably due to the greater carbon investment in the aboveground parts of the trees in the period. Production of both the finest and very fine roots, and precipitation and air temperature were the highest in July, suggesting that the precipitation and air temperature in July are very propitious to root growth of Asia white birch and the plant has a highest potential for water and nutrient uptake in the period. Biomass, necromass, production, mortality, disappearance and turnover rate of the finest roots were significantly higher than those of very fine roots, whereas the ratio of necromass to biomass of the finest roots was significantly lower than that of very fine roots. Fine root mass, production, mortality, disappearance and turnover rate decreased, but ratio of necromass to biomass increased along soil depth for both the finest and very fine roots. The mean turnover rate of the finest roots, very fine roots and fine roots of the two size classes in the 0–55 cm soil layer were 0.63, 0.39 and 0.51 year −1, respectively.