Study On Underground Biomass In Evergreen Sbutropical Broad-Levaed Forest Of Gutianshan

Underground biomass is quite important in estimation of biomass and productivity of forest ecosystems. Compared with the aboveground biomass, however, only limited studies concerned the underground part due to complexity of roots systems and difficulties in root biomass measurement. Allometry equations of the three dominant species(Pinus massoniana, Schima superb, Castanopsis eyrei) of a subtropical evergreen broad-leaved forest in Gutianshan were established to measure the biomass of coarse roots of these three tree species under the background of snow disaster in 2008; The soil core method were also used to measure the biomass of roots in forests of three successional stages. This study will provide basic information on underground ecology of subtropical evergreen broad-leaved forest; in a long view, it will it have a positive influence on community ecology of substropical evergreen broad-leaved forest. The mean results are as follow:The allometry equations of three species We sampled normal growth trees and fallen trees after the snow disaster in 2008, and underground biomass and DBH of three dominant tree species were measured to establish the allometry equations. The allometry equations for young trees with DBH less than 8 cm (y represents the underground biomass and x represents DBH) of the three species are:P. massoniana: y=0.0096x2.6938 (R2=0.9837), S. superb:y=0.0667x2.2486 (R2=0.9632), C. eyrei: y=0.0639x2.1473 (R2=0.9717). When considering the big fallen trees in the snow disaster, the allometry equations can be shown as (y represents the underground biomass and x represents DBH):P. massoniana:y=0.1269x2.1649 (R2=0.9925), S. superb:y=0.2388x2.1071(R2=0.9791), C. eyrei:y=0.2298x2.0486(R2=0.9944). And the allometry equations for the whole biomass (y represents the whole biomass and x represents DBH) of three tree species are, P. massoniana:y=0.1367x2.2112 (R2 =0.9934), S. superb:y=0.3992x1.9404 (R2=0.9766), C. eyrei:y=0.3492x1.9305 (R2 =0.975).Root biomass of the three successional stages forests We used the soil core method to measure the root biomass of three successional stages (Early, Middle, Late) forests. The results showed that (1) the stand root biomass of forests in the three successional stages were 1725g/m2,1041.64g/m2 and 1663.46g/m2; (2) the live fine root biomass of forests in the three successional stages were 498.84g/m2,301.07g/m2 and 404.25g/m2; and (3) dead fine root biomass of forests in the three successional stages were 42.64g/m2,51.17g/m2 and 33.03g/m2. There was a significant difference of root biomass among three successional stages. Biomass of fine roots decreased with the increase of soil depth and about 85% fine roots distributed in the surface layer of the soil. The whole root biomass and fine root biomass of forests in the middle successional stage were significant lower than forests in the early and late successional stages.Based on the results of our study on underground biomass of the dominate tree species, we found that the growth of above-ground and under-ground parts of these trees were well matched and significantly correlated, which enable us to estimate the underground biomass using above-ground parameters such as DBH and height by the allometry. equations; Our results of the root biomass in forests of three successional stages indicate that significant changes of root biomass may occurs during vegetation succession, especially for the fine roots.