Fine Root Biomass And Production In Four Subtropical Forests With Various Regeneration Methods

To investigate fine root biomass and production of forest stands regenerated with different approaches,the secondary forest of Castanopsis carlesii through natural regeneration(NR),the secondary forest of C.carlesii through natural regeneration with anthropogenic promotion(AR),C.carlesii plantation forest(MZ),and Pinus massoniana plantaion(PM),which were located at the same site at nature reserve of Castanopsis kawakamii and Chenda town,Sanming City,Fujian province,were selected.Fine root biomass,production,and root morphological and branching characteristics were measured by the combination of soil core and minirhizotron methods.The results showed that:Fine foot biomass in the MZ,AR and NR forests were(182.46± 10.81),(242.73± 17.85)and(353.11± 16.46)g·m-2,respectively,showing an increased tendency with increasing tree species diversity.However,there was no influence of tree species diversity on spatial niche segregation in fine roots and fine root morphological plasticity at the stand level showed no responses to tree species diversity.Root biomass,root surface area density and root length density all decreased with the increasing soil depth in the MZ,which were 1.5 times,1.2 times and 2.2 times higher than in the PM,respectively.The specific root length,root tissue density,specific root tip density and specific root forks density were higher,but in the average root diameter and specific root surface area were lower in the MZ stand than those in the PM stand.Fine root production of the three C.carlesii stands ranged from 51.8±10.4 g·m-2·yr-1(MZ)to 68.5±18.8 g·m-2·yr-1(AR)and 70.6± 17.7 g·m2·yr-1(NR).Total fine root length production and fine root biomass were highest in the NR stand but lowest in the MZ stand.The percentage of fine root production in 0-0.05 mm diameter was highest in NR and lowest in MZ.The higher tree species diversity is,the more rapidly fine root system recoved following soil disturbance.During the study period,fine root production of the three C.carlesii stands were all at the low level and had not reached the steady level yet.PM has higher fine root production(92.1±24.6 g·m-2·yr-1)and total fine root length production but slightly lower fine root biomass than MZ.There was no difference in the percentages of fine root production in 0-0.5 mm diameter between PM and MZ.Spring and summer were the main born seasons for fine roots of all the four stands.Our results indicated that fine root biomass and production in the four subtropical forests with various regeneration methods were not only postively correlated with tree species diversity,but also affected by the tree species identity.