| Evergreen broad-leaved forest is unique to the region of humid subtropical forest ecosystems, contains a wealth of resources and biodiversity. Phyllostachys edulis is a tall scattered tree-like clone plants, relying on a strong underground stem(rhizome) spread to the evergreen broad-leaved forest in order to achieve clonal expansion, resulting in evergreen broad-leaved forest succession formatting of bamboo evergreen broad-leaf mixed forest even pure P. edulis forests under human disturbance. Therefore, significant ecological function change in the new stand of formation from evergreen broadleaved forest succession process became a research hotspot. In this paper, the study object was 4 stands of P. edulis expansion varying degrees to evergreen broad-leaved forest: evergreen broad-leaved forest, 2:8 bamboo and broadleaf mixed forest, 8:2 bamboo and broadleaf mixed forest and pure P. edulis forest. Through plot investigation, laboratory test and statistical analysis, this paper studied communities structure, carbon sequestration, water conservation function and soil physicochemical properties. Based on the analysis mentioned above, the paper established comprehensive index evaluation system of significal ecological functions of evergreen broad-leaved forest in response to the expansion of P. edulis. The aim was to provide theoretical support to forest vegetation succession and ecological function changing in subtropical, at the same time, to abound ecological functions research in the P. edulis main distribution area in south of China, to provide foundation to forest scientific management in Dagangshan region, Jiangxi Province, P.R. China. The main conclusions are summarized as follows:1. The DBH and tree height of 4 kinds of investigated stands diameter class showed a normal scattered. In different stands, with P. edulis dilatation increased, evergreen broad-leaved forest DBH decreased, white P. edulis DBH increased. The order of M richness, Simpson index and Shannon index in 4 stands contains evergreen broadleaf forest(evergreen broad-leaved forest, 2:8 bamboo and broadleaf mixed forest and 8:2 bamboo and broadleaf mixed forest) was shrub layer> herb layer> arborous layer. In pure P. edulis forest, diversity index of arborous layer was lowest.2. The carbon storage of soil was higher than vegetation layer C. storage in 4 stands. In vegetation layer, evergreen broadleaf C. storage of aboveground was more than that of P. edulis, while underground part(root) C. stock was lower than P. edulis root and rhizome C. stock. The order of ecosystem carbon storage in 4 stands was: 8:2 bamboo and broadleaf mixed forest(264.85 t C·hm-2)﹥2:8 bamboo and broadleaf mixed forest(260.46 tC·hm-2)﹥pure P. edulis forest(217.33 tC·hm-2)﹥evergreen broad-leaved forest(206.05 tC·hm-2).3. Because evergreen broadleaved forest canopy development, canopy interception capability was better than that containing P. edulis stands. P. edulis developed root and rhizome enhanced its soil layer water conservation capacity. The order of annual average of LAI in 4 stands was: evergreen broad-leaved forest(3.56)﹥2:8 bamboo and broadleaf mixed forest(3.21)﹥pure P. edulis forest(2.97)﹥8:2 bamboo and broadleaf mixed forest(2.92). Annual rainfall of research area was 1809.33 mm, comprehensive analysis, the order of canopy interception was evergreen broad-leaved forest﹥2:8 bamboo and broadleaf mixed forest﹥8:2 bamboo and broadleaf mixed forest﹥pure P. edulis forest. In 4 text stands, the order of litter total reserves was pure P. edulis forest(7.56 t·hm-2)﹥8:2 bamboo and broadleaf mixed forest(6.93 t·hm-2)﹥2:8 bamboo and broadleaf mixed forest(6.86 t·hm-2)﹥evergreen broad-leaved forest(5.10 t·hm-2). The water-holding capacity of litter in different stands with various decomposition rate was consistent. The order of water-holding capacity of undecomposed litter was 2:8 bamboo and broadleaf mixed forest﹥pure P. edulis forest﹥8:2 bamboo and broadleaf mixed forest﹥evergreen broad-leaved forest, while the order of water-holding capacity of semi-decomposed litter was pure P. edulis forest﹥2:8 bamboo and broadleaf mixed forest﹥8:2 bamboo and broadleaf mixed forest ﹥ evergreen broad-leaved forest. Water-holding capacity of undecomposed litter increased rapidly within 4 hours, then rose slowly, while that of semi-decomposed litter was steady after 2 hours. Saturated water holding capacity and capillary water holding capacity of pure P. edulis forest showed best performance, non-capillary water holding capacity evergreen broadleaved forest is best. The order of existing water storage in 4 stands was pure P. edulis forest﹥8:2 bamboo and broadleaf mixed forest evergreen broad-leaved forest﹥2:8 bamboo and broadleaf mixed forest﹥, that of saturated water storage was pure P. edulis forest﹥evergreen broad-leaved forest﹥2:8 bamboo and broadleaf mixed forest﹥8:2 bamboo and broadleaf mixed forest.4. Soil quality of pure P. edulis forest was lower than evergreen broad-leaved forest. The order of comprehensive evaluation of soil in 4 stands was 2:8 bamboo and broadleaf mixed forest﹥evergreen broad-leaved forest﹥8:2 bamboo and broadleaf mixed forest﹥pure P. edulis forest, soil quality at beginning of degradation was best. In test 4 stands, PH value of soil was no significant difference, and physical properties of pure P. edulis forest significantly was superior to the stands contained evergreen broadleaf forest, soil nutrient decreased with depth. From statisticsing the content of organic matter, total nitrogen and alkaline hydrolysis nitrogen, total phosphorus and effective phosphorus, total potassium and available potassium, pure P. edulis forest was significantly lower than evergreen broad-leaved and mixed forests. The content of soil Ca element of pure P. edulis forest was lowest, while, the content of soil Mg of evergreen broad-leaved forest was highest.5. From comparison in major ecological functions comprehensive evaluation, the results showed that the significant ecological function score of evergreen broad-leaved forest was highest, 2:8 bamboo and broadleaf mixed forest was second, 8:2 bamboo and broadleaf mixed forest was third, while the last one was pure P. edulis forest. This indicated that comprehensive level of ecological function of was downward trend in the the process of P. edulis forest expanding to evergreen broad-leaved forest. To avoid P. edulis interference with evergreen broad-leaved forest ecosystems and maximize the ecological function of forest land, evergreen broadleaved forest should be proteced in order to reduce deforestation interference and replant in higher proportion of P. edulis forest during the business aspects of forest in subtropical area, designed to maximize the service functions of forest ecosystems. |
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