Effects Of Continuous Cropping On The Biomass And Productivity In Sprout Forest Stands Of Eucalyptus Urophylla×E.Grandis

Based on the experimental sites and research of Forestry College, Guangxi University which was conducted at Dongmen Forest Farm, we carried out the research on the growth, volume, biomass and productivity between the first rotation sprout forest stand (Ⅰ sprout stand) and the second rotation sprout forest stand (Ⅱ sprout stand) of Eucalyptus urophylla×E. grandis, in order to understand the effects of continuous cropping on the biomass and productivity of Eucalyptus sprout forest stand and provide guidance to sustainable management of eucalypt forest plantation. The results showed that:a. The DBH, height and volume increment of II sprout stand was 10.39% and 4.66% and 22.19% higher than that of I sprout stand, respectively, the variance of analysis show that there was no significant difference in DBH and height between I sprout stand and II sprout stand (p=0.365-0.374), while was significant difference in volume increment (p=0.045).b. There was significant difference of the biomass between I sprout stand and II sprout stand (p=0.048), the result indicated that the biomass of II sprout stand (84.39t/ha) was significant higher than that of I sprout stand (68.68t/ha).c. The mean productivity both sprout stands was 13.77t/ha-a in II sprout stand,11.14 t/ha·a in I sprout stand, respectively. The variance of analysis show that there was no significant difference in both sprout stands (p=0.748).d. The size order of organic biomass in both sprout stands was similar, presented to ranging stem (62.33-62.98%)> root (23.48-24.28%)> bark (6.40-6.46%)> branch (5.07-5.25%)> leaf (1.85-1.90%).e. The productivity of stem, bark and root in II sprout stand was significant higher than that in I sprout stand (p<0.05), while branch and leaf was no significantly difference (p>0.05).f. The biomass of understory vegetation in I sprout stand (8.00t/ha) was significant higher than that in II sprout stand (5.44t/ha). The variance of analysis show that there was no significant difference of shrub biomass in both sprout stands (p=0.820) but had extremlly significant difference of herb biomass (p=0.002).g. The above results indicated that there was no significant effect of continuous cropping on the biomass and productivity in Eucalytus sprout stand, but there was a significant effect of continuous cropping on the biomass of understory vegetation.