| Evergreen broad-leaved forest is a typical vegetation type of subtropical zone. China's evergreen broad-leaved forest has unique characteristic, extensive distribution, abundant natural resources and high impacts of human disturbances. Succession dynamic plays an important role in the study of evergreen broad-leaved forest. The most important part of that is the succession process and mechanism of evergreen broad-leaved forest under natural and human disturbances. Recently, there are many studies about the succession of evergreen broad-leaved forests. A lot of experiences have been performed and some key findings have been achieved, including species physiological ecology and population ecology, the ecological restoration theory and ecological service function of evergreen broad-leaved forest.However, based on the field observations and experiments, most researches used the experimental ecological theories and methods to analysis the small-scale and short-term succession phenomenon and succession sequences of the evergreen broad-leaved forest. It's difficult to reflect large-scale and long-term forest community landscape changes. The impacts of forest natural succession and human or natural disturbance always occur in ten to hundreds of years of time scale and dozens to millions of hectares of space scale. Therefore, it needs to use the spatially explicit landscape model to simulate vegetation succession.In this study, the spatially explicit landscape model (LANDIS6.0PRO) was used to simulate the natural succession of evergreen broad-leaved forest in500years in Tiantong National Forest Park, Zhejiang Province, parameterized based on the long-term research and observation data of Tiantong National Station of Forest Ecosystem Observation and Research. The impacts of climate change on forest succession were further simulated. Spatial distributions of dominant species and major landscapes, and the species age structure were investigated to reveal the rule of evergreen broad-leaved forest succession. Results indicate that:(1) Species dynamic changes:Species alternate before the stage of evergreen broad-leaved forest. Pinus massoniana, Quercus fabri and Liquidambar formosana have a large proportion during the early succession, but gradually disappear along with the succession process. Schima superba and Castanopsis fargesii take the main advantage in late succession and develop to the climax community. Climate change has less impact on dominant species of climax community. Species of the early succession such as Quercus fabri and Platycarya strobilacea, are more susceptible to the impact of climate change. Their areas will increase along with climate change impacted succession. Some dominant species of non-climax communities, such as Symplocos sumuntia, Pinus massoniana, Lithocarpus harlandii and Symplocos stellaris, will advance their time points of species area becoming stable in the succession. In general, climate change has no significant impacts on the whole succession process of Tiantong vegetation. The direction of the community succession will still go to the evergreen broad-leaved forest as its climax.(2) Landscape distribution:As the main community types of Tiantong region, the evergreen broad-leaved forest has the stable area and species composition under the simulation of natural succession. The dominant species such as Schima superba and Castanopsis fargesii occupy the high area percentage in a long time. Deciduous forest and mixed forests have more species diversity and more obvious area changes. Some deciduous species such as Quercus fabri, Platycarya strobilacea, Liquidambar formosana, Carpinus viminea and some evergreen species such as Lithocarpus harlandii and Cunninghamia lanceolata dominate the communities. Shrubland as an early stage vegetation of natural succession has many shrubby species of Rhododendron simsii and Symplocos sumuntia and deciduous species of Quercus fabri and Platycarya strobilacea. Under the impact of climate change areas of most species will significantly increase. Some deciduous trees(Quercus fabri, Platycarya strobilacea and Carpinus viminea) and some shrubs(Rhododendron ovatum, Symplocos sumuntia and Symplocos stellaris) have the biggest changes of their areas. However, some dominant evergreen species of climax community, such as Castanopsis fargesii, Schima superba, Castanopsis sclerophylla and Lithocarpus glaber, don't have significant changes. From this point of view, climate change has stronger impact on deciduous trees rather than evergreen trees.(3) Age composition:Under natural succession, there are a large number of young species in the early succession and a great number of mature or over-mature species in the late succession, indicating less ability of regeneration of communities. Under the impact of climate change, areas of mature or over-mature species in the late succession have further increase compared with natural succession. Young species occupy much less proportion and therefore still benefit nothing to vegetation regeneration. Most of species have very slight or no changes in the age structure under climate change, but Quercus fabri and Liquidambar formosana have relatively obvious changes of age structure.The study indicated that the LANDIS model can be used in simulating landscape dynamics of evergreen broad-leaved forest in eastern China. However, the parameterization of LANDIS is difficult due to the complexity of species composition and attributes as well as the lack of adequate observation and experiment data of evergreen broad-leaved forest. Both model structure and parameters should be improved in the future research according to the complexity and diversity of subtropical evergreen broad-leaved forest. Thus LANDIS could be better used to simulate the succession of evergreen broad-leaved forest. Furthermore simulation research of disturbance and management of the forest should be strengthened. This will provide the theoretical basis and advice on evergreen broad-leaved forest management, sustainable development and the recovery of damaged ecosystem. |
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