| Tropical rain forest are not only the global species gathering places and shelters,but also play important roles in carbon dioxide sequestration and ecological hydrologic cycle in the world.Whereas it was damaged by human disturbances.The recovery dynamic of the ecosystem service function in tropical secondary forests after disturbances has become a hot topic.Research on the subjects are the tropical secondary forests after shifting cultivation in Bawangling Natural Reserve and the tropical secondary forests after selective logging in Diaoluoshan Natural Reserve,located in Hainan,China.We established 8 and 9 plots(each 50m x 50m)respectively.According to the different recovery age,they were divided into young-aged forest(forest age ≈ 30 yrs),middle-aged forest(forest age ≈ 60 yrs)and old-growth forest(forest age>120 yrs)by the method of space instead of time.Species diversity,photosynthetic rate,water conservation of litter and soil were investigated and measured within the plots.Analysing the service function of species biodiversity conservat ion,carbon dioxide sequestration and oxygen release of plant,and water conservation of litter and soil in the two disturbance types and three forest stages.The main results are as follows:1)There were 192 species,belonging to 40 families,70 genera in the communities after shifting cultivation and 424 species,belonging to 64 families,184 genera in the communities after selecting logging.Communities in accordance with the size of the growth form were divided into ground layer,regeneration layer,succession layer and canopy layer in turn.We found that after shifting cultivation,species diversity increased across the three recovery stages for the overall and four vertical communities,and species abundance decreased for overall communities while changed inconsistently for the four vertical communities.After selective logging,however,there was generally little change in species diversity and abundance across the three forest stages,either overall or within the vertical communities.Non-Metric Multidimensional Scaling showed differences in species composition across the three stages after shifting cultivation,but no differences in those after selective logging.We also divided species dissimilarity coefficients into two parts which the variability indics of species composition and abundance among vertical communities under canopy and canopy communities,showing changes in species composition and abundance between the vertical communities under canopies and the canopy communities.We found that after shifting cultivation the coefficients between young and middle-aged forests and old-growth forests were more than 0.77&0.93,but that they did not differ after selective logging had occurred.2)In addition to communities in young-aged forest after shifting cultivation,canopy communities are the main contributor of the carbon dioxide sequestration and oxygen release function,and contribute more than 50%product of the relevant overall communities in other stages.There is no difference of communities after shifting cultivation and selecting logging in the same forest stages.After shifting cultivation,the carbon dioxide sequestration and oxygen release function of the overall communities,showed a trend of increased first and then decline with forest age increase,and those of the canopy communities showed a trend of increased first and then gently changing with forest age increase;After selecting logging the carbon dioxide sequestration and oxygen release function of the overall communities,showed a trend of decline with forest age increase,and no significant changes of vertical communities in different forest stages.3)The maximum water-holding ratio and natural water content of litter and soil after shifting cultivation were lower than those after selecting logging;the maximum water-holding ratio of litter decreased after disturbance,but natural water content did not differ among the three recovery stages.The maximum water-holding ratio of soil increased.However,the maximum water-holding ratio of 0-40 cm soil decreased and then increased after selecting logging.But it did not differ at the depth of 40-60 cm among the three recovery stages.The maximum water-holding ratio and natural water content of litter were greater than those of soil.In general.,the maximum water-holding ratio of shallower soil were higher than those of deeper soil,but the natural water content of soil in different depth did not differ.The maximum water-holding ratio of litter was negatively correlated with those of soil in different depth.The maximum water-holding ratio of soil in different depth were significantly correlated. |
