Analysis of the Variation Characteristics of Fine Root Biomass in Cunninghamia lanceolata Plantation Forest of Different Stand Ages

In order to understand the variation characteristics of fine root biomass in Cunninghamia lanceolata plantation forest with stand age and soil depth, the variation characteristics of fine root biomass within 60 cm soil layer of 7, 10, 23, 29 and 42-year-old Cunninghamia lanceolata plantation forest in Baisha State-owned Forest Farm of Longyan City in Fujian were studied. The results showed that: (1) The total biomass of fine roots of Cunninghamia lanceolata had no significant difference among the 10, 23, 29 and 42-year-old stands, and they were all significantly higher than that of the 7-year-old stand; (2) When the stand age was not distinguished, the average fine root biomass of 0-1 mm decreased with the increase of soil depth; while the average fine root biomass of 1-2 mm had no significant difference among various soil layers; (3) When the stand age was distinguished, the fine root biomass of Cunninghamia lanceolata had no significant difference among various soil layers at the 7-year-old stand, and the vertical distribution was relatively even; while at the 42-year-old stand, the fine root biomass in the 10-20 cm soil layer was the largest, but it was not significantly higher than that in the 0-10 cm soil layer; (4) The ratio of absorption root/transport root biomass had no significant difference among various soil layers at 7-year-old and 23-year-old stands, while it decreased with the increase of soil depth at 20, 29 and 42-year-old stands; (5) The ratio of absorption root/transport root biomass in the 0-10 cm soil layer was the largest at the 29-year-old stand, but it decreased slightly at the 42-year-old stand. In summary, in the later stage of stand development, the nutrient acquisition of fine roots of Cunninghamia lanceolata might be more conservative, but it needed to maintain a large biomass, which might be a factor leading to the productivity decline of Cunninghamia lanceolata in the later stage of development. This provided a scientific basis for revealing the possible reasons for the productivity decline of Cunninghamia lanceolata plantation forest.