Studies On Community Characteristics And Ice-snow Damage Of Subtropical Evergreen Broad-leaved Forest In Jiulianshan Mountain

The south of China suffered heavy ice-snow disturbance in 2008, more than 800 Natural Reserve were badly damaged, and ecological environment was seriously disturbed. How to accurately obtain damage degree information, identify representative evaluation factors and indexes are urgent work to restoration of Forest Ecosystem and preservation of Biodiversity. Besides, as the transition zone, studies on community characteristics of subtropical evergreen broad-leaved Forest in Jiulianshan Mountain are important to the researches on national subtropical evergreen broad-leaved Forest and Biodiversity. Based on the large fixed monitoring plot of subtropical evergreen broad-leaved Forest in Jiulianshan Mountain, the community characteristics and herb seasonal dynamics were studied in this article. The influences of ice-snow distubance on different tree-layers was demonstrated, and then the influences of Dbh, abundance, aspect and slope on damage degree were analyzed. In order to understand the resistance to ice-snow disturbance of different dominant species, the damage degree of dominant species were compared. At last, according to the death information after one year, the effects of ice-snow disturbance on community composition and structure were researched and related restoration measures were suggested. The brief results are as follows:1 Community characteristics of subtropical evergreen broad-leaved forest in Jiulianshan MountainThere are rich species in Forest, including 58 families,108 genera and 221 species. Evergreen species of Castanopsis take the absolutely dominant position, accompanying by the evergreen species of Lauraceae, Theaceae, Ebenaceae, and Alniphyllum fortunei, Liquidambar formosana, Pinus massoniana have certain number. The vertical structure was apparently divided into 5 layers. The Dbh class structures of dominant species mostly are stable growth type. Castanopsis lamontii, C.fabri, C.carlesii, C.fargesil, D.morrisiana and Eurya loquaiana tend to have aggregated spatial distribution at different scales.2 Species diversities and seasonal dynamics of herbs There are 75 herbs in plot, including 36 ferns. Herbs respectively belong to 61 genera and 39 families. Death of Lophatherum gracile, Oplismenus undulatifolius in winter had certain influence on species composition, but the influence was not significant. Woodwardia japonica and Plagiogyria distinctissima had highest SDR in different seasons. Species diversity in winter was lowest, and other seasons were similar. Abundance structure was uneven, and the individual number of 1?16 abundance class in different seasons was the most. In vertical structure, the individual number below 30cm was the most. Areas of low-slope and near water had the most number of species and individuals.3 Influence of ice-snow disturbance on different tree layersDamage situation of plants were different among three tree-layers. Plants in under-layer were mostly in damaged modes of bending, plants in mid-layer were subjected to trunk breakage, top breakage and bending, and plants in upper-layer mostly suffered top breakage. In whole forest, Individual numbers of different damage classes were significantly negative correlation with Dbh classes; uprooting rate, trunk breakage rate were significantly negative correlation with Dbh classes; however top breakage rate, MDI were significantly positive correlation with Dbh classes. In different tree-layers, the number of damaged individuals of different damage modes were significantly positive correlation with abundance, however the damage rates were no significant correlation with abundance. Uprooting number, trunk breakage number, uprooting rate, trunk breakage rate, MDI of plants in mid-layer were significantly positive correlation with MDI of plants in upper-layer. Uprooting number, trunk breakage number, bending number, uprooting rate, trunk breakage rate, bending rate, and MDI of plants in under-layer were significantly positive correlation with MDI of plants in upper and mid-layer. Totally, aspect had significant effect on damage number and rates of different damage modes in different tree-layers. Plants under N-NE aspect suffered most serious damage. Except for trunk breakage rate of plants in mid-layer, slope had no significant effect on other damage rates in different tree-layers. Slope had significant effect on trunk breakage number in mid-layer, bending number in under-layer and whole forest, trunk breakage and top breakage number in whole forest. Dbh and aspect can be selected as valuable factors on numbers and rates of damage, abundance can be selected as valuable factors on numbers of damage. MDI value was the best valuable index on numbers and rates of damage.4 Comparison of dominant species damage degree The damage degree among dominant species (Iv?5% ) had significant difference. In upper-layer, MDI of Neolitsea chuii, Myrica rubra, Castanopsis carlesii and Pinus massoniana were above 180%, however Neolitsea aurata var.chekiangensis and Rhododendron westlandii were below 80%. In mid-layer, MDI of C.carlesii, Schima superba and C.lamontii were above 150%, but N.aurata var.chekiangensis, Photinia parvifolia, R.championae, Ternstroemia gymnanthera, R.westlandii, E.tetragonoclada and Litsea elongate were below 100%. In under-layer, MDI of C.fabri, C.carlesii, E.distichophylla and Machilus thunbergii were above 70%, on the contrary, Tricalysia dubia, M.grijsii, Daphniphyllum oldhami, E.loquaiana and Camellia cordifolia were below 50%. In the whole, C. carlesii and N.chuii suffered more serious damage, and Neolitsea aurata var.chekiangensis and Rhododendron westlandii had strong resistence to ice-snow disaster.5 Influence of ice-snow disturbance on forest composition and structureDeath rate of plants after one year was about 12%. The influence of ice-snow disturbance on species composition, dominant composition and species diversities in short time were little. The important value of A.fortunei and P.massoniana respectively decreased 19.0% and 16.8% , but changes of other dominant species were less than 10% . Individual number in 0-5m height class increased to 11 times after one year, and number in other height classes decreased to certain extent. Number of individuals in different Dbh of dominant species decreased after one year, however the Dbh class structure have no change. Ice-snow disturbance had little influence on species composition and community structure of subtropical evergreen broad-leaved forest in Jiulianshan Mountain, and growth trend of dominant species had no change, so the natural restoration was suggested to local forest recovery.