Fine Root Production,Mortality And Biomass At Early Stages Of Different Regeneration Methods In Subtropical Forests

The production,mortality and turnover of fine roots,the most active and dynamic part of root system,play a very important role in carbon allocation and nutrient cycling were determined by the combination of soil core and minirhizotron methods in three recently regenerated stands in terrestrial ecosystems.Fine root production,mortality and standing crop were determined by the combination of soil core and minirhizotron methods in three recently regenerated stands with different regeneration measures in Sanming City,Fujian province.These stands included:a young secondary forest of Castanopsis carlesii through natural regeneration with anthropogenic promotion(AR),a young C.carlesii plantation(CC),and a young Cunninghamia lanceolata plantation(CL),with the mature secondary forest of C.carlesii(CT)as a control.The results showed that annual fine root production of these stands were 284.0±15.3 g·m-2·yr-1(AR),163.9±4.3g·m-2·yr-1(CC),144.6±5.3g·m-2·yr-1(CL),and 15.4±2.0 g·m-2·yr-1(CT),respectively.Annual fine root mortality of the three young stands were 31.1±2.9g·m-2·yr-1(AR),14.0±4.1 g·m-2·yr-1(CC),and 7.3±1.1 g·m-2·yr-1(CL),respectively,but the mortality of NR was only 2.1±0.6 g·m-2·yr-1.Meanwhile,the fine root biomass in the four stands were 336.8±85.0 g·m-2(AR),186.4±65.5 g·m-2(CC),138±50.2 g·m-2(CL),and 159.1±4.8 g·m-2(CT),respectively.There existed seasonal differences in fine root production,mortality and biomass among the three young stands.Fine roots of AR and CC were mainly produced in spring,but those of CL in autumn.However,fine root mortality of the three young stands occurred mainly in summer and autumn.Fine root production,mortality,and biomass of the three young stands were mainly distributed in the soil layer of 20-40cm and in the diameter range of 0-1 mm.This study demonstrated that fine root biomass,production and mortality in the AR stand were all higher than those in the two young plantation stands,indicating that the natural regeneration method with anthropogenic promotion measures is more conducive to increase organic matter input to the soil and hence reduce net carbon source during the initial stage of forest regeneration.