Research On Forest Plant Diversity In The Three-Gorges Reservoir Area

Based on the investigated data of 132 temporal and 146 permanent plots and the data of national second-class forest resource investigation(1999-2003) in the Three Gorges Reservoir Area, species diversity of the forest communities in the area was mainly studied using the integration of quantitative and qualitative methods, especially quantitative analysis methods. Flora characteristics of seed plants, quantitative classification and ordination of plant communities and their environmental interpretations, plant species diversity and their responses to environment, and changes of soil nutrients along with community succession in the area were analyzed deeply together with the analysis of the community structure and species diversity, niche and interspecific association of under-story species of the main coniferous forest in the area. Current status, existing problems and conservation strategies of the rare and endangered species in the area were also analyzed finally. This study will be significance theoretically and practically of restoration, rehabilitation, and sustainable management for the degraded forest in the area.Areal types of genera of seed plants in the area were divided in 15 types according to the method for Areal types'study of Prof. Wu Zhengyi. The dominant type was tropical areal type, then temperate areal type, and the transitional feature was obvious. The origin of the flora was ancient and there were plenty of plant species, including 5688 seed plant species, accounting for 22% of total species in China. There were 56 rare and endangered plant species, belonging to 34 families and 48 genera, and accounting for 10% of the total number in China approximately. They had transitional, decentralized and endemic characteristics and have been disturbed by human activities seriously.Plant communities were divided into 33 types by the quantitative method TWINSPAN (TWo INdicator Species ANalysis) in the area. They were Form. Pinus henryi, Form. P. armandii, Form. P. massoniana, Form. Cunnighamia lanceolata, Form. Cupessus funebris, Form. Pinus massoniana+Quercus variabilis, Form. Pinus massoniana +Castanopsis fargesii, Form. Pinus massoniana+ Grdonia axillaris, Form. Cunnighamia lanceolata+Castamopsis fargesii, Form. Quercus glandulifera var. brevipetiolata, Form. Q. variabilis, Form. Q. albus, Form. Q. aliena+Q. variabilis, Form. Q. dentata var. oxyloba, Form. Fagus lucida, Form. Dendrobenthamia japonica var. chinensis, Form. Liquidambar taiwaniana, Form. Castanea seguinii, Form. Platycarya strobilacea, Form. Betaula albo-sinensis, Form. B. utilis, Form. Cerasus conrodinae+Quercus spinosa, Form. Cercidiphyllum japonicum+Padus obtusata, Form. Cornus controversa, Form. Celtis sinensis, Form. Lithocarpus cleistocarpus+Castanea henryi, Form. Platycarya strobilacea+Cyclobalanopsis oxyodon, Form. Lithocarpus glaber, Form. Castanopsis eyeri, Form. Ormosia henryi, Form. Machilus pingii, Form. Gordonia asillaris and Form. Quercus spinosa. Distribution of the plant communities and the relationships with the environmental factors were interpreted well by the result of DCA (Detrended Correspondence Analysis) ordination of the communities. Integration of temperature, elevation, soil water content of the community sites was reflected obviously by the DAC result. The main trend was that soil water content and temperature was decreasing with the elevation increasing, the vegetation types were evergreen broad- leaved forest, evergreen and deciduous broad-leaved mixed forest, deciduous broad-leaved forest, coniferous and board-leaved mixed forest, and coniferous forest respectively.Plant species richness index of shrub was the highest and that of herb was higher, but they were fluctuant in different communities. Because of the environmental heterogeneity and the strong artificial disturbance, there was no obvious trend of the diversity indices of the communities along with the elevation. With the positive succession of the vegetation, shrub—coniferous forest—coniferous and broad-leaved mixed forest—deciduous broad-leaved forest—evergreen broad-leaved forest in the area, soil pH value decreased gradually, organic matter and available phosphorus of the soil increased while hydrolysable nitrogen decreased gradually, though all of them distributed principally in surface layer.Coniferous forest occupied approximately 50% in the middle and low mountain area in the Three Gorges Reservoir Area, Pinus massoniana forest 34%, Cunnighamia lanceolata forest 10%, and Cupessus funebris forest 6%. The main trend of the species diversity of this three forest types was as same as that of the forest in the area. The niche breadths of the shrub species populations, Smilax davidiana,Myrsine Africana, Eurya japonica, Rosa cymosa, Pittosporum phillyraeoides, Glochidion puberum and Vaccinium serrulatum, and the herb species populations, Dicranopteris linearis, Miscanthus sinensis, Pteridium aquilinum, Imperata cylindrica, Arundinella anomala and Stenoloma chusanum, were higher, while that of the shrub species populations, Melastoma normale, Viburnum utile and Urena lobata, and the herb species populations, Cheilosoria chusana, Lophatherum gracile, Centotheca lappacea, Themeda japonica, Saccharum arunndinaceum, Phyllostachys heteroclada, Adiantum flabellulatum and Adiantum pedatum, was lower relatively in Pinus massoniana community. The niche overlaps between the shrub species populations of Eurya japonica and Rhododendron mucronulatum, Smilax glabra and Lindera glauca, Vitex negundo and Ficus tikoua, Vaccinium serrulatum and Pittosporum phillyraeoides, and herb species populations of Adiantum pedatum and Dryopteris championii, Stenoloma chusanum and Miscanthus nepalensis, Adiantum flabellulatum and Arundinella anomala, were higher in Pinus massoniana community. In addition, the overlaps among the species populations belonging to the same genus, Viburnum utile and V. erosum, Smilax davidiana, S. hypoglauca and S. glabra, Carex capilliformis, C. lanceolata, C. baccans and C. maubertiana, Adiantum pedatum and A. flabellulatum, Dicranopteris linearis and D. dichotoma, Parathelypteris glanduligera and P. japonica, were lower relatively. This could be helpful for the coexistence of the species in a small area.The interspecific association between the shrub species populations, Loropetalum chinense and Pittosporum phillyraeoides, was positive significantly, while the associations between the populations of Cotinus coggygria, Smilax glabra, Coriaria nepalensis and Melastoma normle were negative significantly in Pinus massoniana community. The interspecific association between the herb species populations, Dicranopteris linearis and Miscanthus sinensis, D. dichotoma and Dryopteris erythrosora, C. capilliformis and Mosla scabra, were positive significantly, while the associations between the populations of Cheilosoria chusana and Lophatherum gracile, Centotheca lappacea, Themeda japonica and Phyllostachys heteroclada, were negative significantly. Understory species of the Pinus massoniana community were divided into four ecological species groups based on their intrespecific association characteristics. The first group included Pittosporum phillyraeoides, Myrsine africana, Loropetalum chinense, Rosa cymosa, Dicranopteris linearis, Miscanthus sinensis, Arundinella anomala and Pteridium aquilinum etc.; the second included Myrsine semiserrata, Smilax hypoglauca, Ficus tikoua, Dicranopteris dichotoma, Woodwardia japonica, Carex capilliformis and Stenoloma chusanum etc.; the third included Smilax davidiana, Eurya japonica, Glochidion puberum, Cheilosoria chusana, Dryopteris erythrosora and Parathelypteris glanduligera etc.; and the fourth included Coriaria nepalensis, Viburnum utile, Rhododendron mucronulatum, Carex baccans, Paspalum orbiculare and Microstegium ciliatum etc..