| In2008, a large scale frozen disturbances struck the evergreen broad-leaved forest of south Asian subtropical in the south of China,caused severely damage. To carry out the studies for the structure and dynamic impaction of main species in evergreen broad-leaved forest under the large-scale frozen disturbances, and to reveal its response characteristic, will provide reference for biodiversity conservation and management, the recovery and reconstruction of damaged ecosystems of the evergreen broad-leaved forest. From April to May in2009, a plot(3.2hm2) was set up in the northeast canyon slope of Daming mountain National Nature Reserve,and conducted a survey at the same time,and to review the forest community of the plot in October of2010and November of2011,and the results showed that:(1) In the3.2hm2plot of Daming mountain evergreen broad-leaved forest, there are95families,202genera and384species vascular plant. The Community is composed of the Lauraceae, Theaceae, the Fagaceae, Symplocaceae, the Rosaceae, Rubiaceae, the Aquifoliaceae, Elaeocarpaceae, etc. as the dominant families, the Huodendronbiaristatum, the Diospyros morrisiana, the Litsea suberosa, the Machilus pauhoi Kanehira, the Stewartia gemmata, the Diospyros morrisiana, the Betula utilis, the Sloanea chingiana, the Alniphyllum fortune and the Lindera metcaljiana are as the dominant species and co-dominant variety. The tropical and subtropical elements (69.44%)are as the dominated position on the Flora, and the certain temperate elements is also being(26.85%). (2) There are some differences on the aspects of structural characteristics in different main species populations of evergreen broad-leaved forest in Darning mountain. The structure of population size for the Huodendron biaristatum is "inverted J type", the Machilus pauhoi Kanehira, the Litsea suberosa and the Diospyros morrisiana are "L type", while the Diospyros morrisiana, the Stewartia gemmata, the Betula utilis, the Sloanea chingiana are "hybrid"; eight tree species and their trail-level individuals at small scales are aggregated distribution; the large diameter and their trail-class individuals of the Huodendronbiaristatum and the Diospyros morrisiana on the small scale are as positive correlation, while rang from0to40m levels, the Acer fabri is negative; two species in total56species are as positive correlation in small scale. These preliminary findings revealed that the seed dispersal limitations and microhabitat heterogeneity of evergreen broad-leaved forest was the reason of the dominant species coexistence.(3) In the large scale catastrophic frozen disturbances of2008, brought about serious damage in the Daming mountain evergreen broad-leaved forest, the damage rate of the evergreen broad-leaved forest was as high as51.8%; Among them, the Damage crown rate was45.95%, the Bended rate was19.0%, the Broken truck rate was7.6%, the Uproot rate was1.4%. The damage rate of the main species was generally higher than the mean disaster rate of the stand, the conclusion was in accordance with the large DHB trees were more severely damaged than the small DBH trees, and the main forest layer trees suffered more serious destruction than the secondary forest crown.(4) There are some differences on the damage of the eight main species in Darning mountain evergreen broad-leaved forest. Classified according to the statistical results of diameter at breast height, the total average damage rat of eight main tree species was71.30%, the coefficient of variation was7.82%; which the average rat of crown damage was46.33%, and the coefficient of variation was9.57%, the Bended rate and coefficient of variation was respectively9.50%and31.85%; the Broken truck rate and coefficient of variation were respectively13.35%and31.77%; the Uproot rate was minimum, and the average rat was2.13%, but the coefficient of variation is maximum, and it is83.19%.The main damage were Damage crown and Broken truck etc.caused by large-scale catastrophic frozen disturbances in2008, but because of the persistent drought in2009and2010, leading to plenty of seedlings and saplings were withered as the main damage.(5) On two surveys from2010to2011,the new recorded of DHB≥1cm saplings were103species in the plot of3.2hm2of Daming mountain evergreen broad-leaved forest. In2010, the new recorded species (96species) were much more,but the individuals of trees (1537) were much less, contrarily, in2011, the new recorded species(86species) were much less but the new added individuals of trees(1605) were much more. On three surveys from2009to2011in eighty plots5m×5m,106species of DBH<1cm tree seedlings were recorded. While, in2009,96species were recorded,and the individuals was1201;42species were recorded in2010, and the individuals was1222; in2011only25species were recorded, and the individuals was782. According to the composite indicator of important value, the dominant species in the new recorded saplings and seedlings were the Lindera metcalfiana, the Machilus pauhoi Kanehira, the Cinnamomum jensenianum, the Engelhardtia roxburghiana, the Diospyros morrisiana, the Litsea suberosa, the Macropanax rosthornii, the Huodendron biaristatum, etc. while, in the new recorded seedlings, the increased rang of the Diplospora fruticosa, the Sloanea chingiana, and the Acer fabri were larger, but the Erythroxylum sinense, the Mallotus apelta, the Mallotus tenuifolius has much larger increased rang in the new recorded saplings. These were mainly determined by the species ecological characteristics and the forest gap dynamics. (6) There is superior fluctuations on species of seedlings and saplings existence in Daming mountain evergreen broad-leaved forest of3.2hm2plots. In2010, new recorded species of DBH≥lcm were96and the individuals was1537,86species and1605individuals were recorded in2011. Whether in2010or2011, the top10individuals of families that were new grown to DBH≥1cm was the Lauraceae, which was about11species, the individuals was rang from480to490, respectively occuupyed from11.46%to12.79%in the total species of the new recorded trees and from29.97%to32.14%in the new individuals. It follows that after the large-scale frozen disturbance, the seedlings of Lauraceae were growth rapid and soon became saplings. The plants of Lauraceae not only were with significant the advantage in the new saplings, and also showed a rapid response in seedling regeneration. On every survey of three years, the seedlings species of Lauraceae appeared rang from5to13in each year,the individuals were rang from230to790, respectively occuupyed from11.58%to25.00%in the total seedlings species and from19.40%to64.98%in individuals. However, the death seedlings species and individuals of Lauraceae were much more, the perannum death species and individuals were rang from9to12and from117to495, respectively occuupyed from13.04%to23.08%and from12.23%to64.12%in death species and individuals in the same period. Thus, the saplings and seedlings dynamic changes of Lauraceae will affect the species update dynamic in the evergreen broad-leaved forest.(7) In3.2hm2plots of Darning mountain evergreen broad-leaved forest, just exsited only one individual saplings species were generally rang from12to16, which exsited rang from2to9individuals were rang from43to45, which had occuupyed about64%in the total saplings species; Similarly, just exsited only one individual seedlings species were range from3to20, and species that were rang from2to9individuals were rang from11to44, and occuupyed from44%to67%in the total seedlings species. It is thus clear that, there was a larger portion of sparse saplings and seedlings individuals existed in evergreen broad-leaved forest of Daming mountain, although their individuals were quite a few, they were the major implication for saplings and seedling bank of understory in the evergreen broad-leaved forest,and which would play an important role in preserving species diversity and succession of community. |
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