Ecological Effect Of Casuarina Equisetifolia Protection Forest System Under Disturbance

The coastal projection is an artificial ecosystem, which is an important part of the construction of ecosystem. Also, it is the systems engineering that can return with tremendous ecological, economic and social benefits. The ecosystem it constructs can not only provide human with a large mount of wood and non-wood forest products, but also plays a irreplaceable role in the maintenance of ecological security as well as the basic living conditions for human. It becomes the major problem to current coastal protections on preparing the effective solution for forest management on coastal sand, building a composite artificial ecosystem with sustainable management, maintaining and improving the soil fertility for casuarina forest as well as ensuring the effectiveness of the protection forest. This paper is based on research work on four casuarina protection forest samples with different coastal gradients and another four with different anthropogenic intervenes, which are all located in Chishan farm, Dongshan town, Fujian province, in order for investigating and comparing on the community compositions, structures and biodiversities among forest samples with different gradients, and on the wind disturbance to the casuarina protection forests under the same elevation, and the physicochemical properties of the soil of casuarina protection forests with different anthropogenic intervenes. Finally, key conclusions are listed below after comprehensive investigation and analysis:(1). It was noticed after investigating on community compositions and structures of casuarina coastal forsest samples of different gradients that the environmental conditions, such as the improvement of soil fertility, the decrease of wind interference and the complexity of ecosystems, vary depending on gradients under certain degree as the different distance away from the coast. The species of plant most closed to the sea is less than other area, which indicates that the environment is not suitable for the growth of plants, due to the closer distance from the coast. In the other hand, it also indicates the improvement of the protection forest on projecting the ecological envionment on certain degree. As the distance to the coast increases, the proportion of plant species in shrub layer shows the trend of increasing then decreasing gradually. Herbaceous species don't vary much, as the vine species show decreasing trends.Species of the community composition and other key data differ much among casuarina protection forests of different coastal gradients. The dominant species in sample A are casuarina, acanthus and ipomoea pescaprae; In sample B, they are acacia, ageratum and sageretia; In sample C, they are casuarina, ageratum and coptosapelta; In sample D, they are casuarina, lantana, ageratum, commelina and rubus parvifolius.The same species in all four plots are casuarina and lantana, the importance value of casualina are 254.00, 62.50, 239.10 and 116.00, which shows the trend of first decreasing, then increasing, and then decreasing, which is because of the artificial acacia plantings in sample B, as well as the natural growth of litsea glutinosa, celtis nervosa, radix Wikstroemiae, etc. and the species diversity of the correspoinding community, which forces the space becoming narrow for casuarina growth. The importance values of lantana are 46.00, 59.30, 52.60 and 116.50. Importance value in plot B is higher than plot A. Meanwhile, the growing space for lantana among plot A, C and D becomes larger as the increasing distance from the coast. Besides casuarina and lantana, the major species in farmland protection forest in plot D also include large areas of litsea glutinosa, one of the native species, which has become the third most importan shrub species community. It shows that species beome rich as the distance increases from the coast. The impotance value of litsea glutinosa increases gradually, while the value for casuarina decreases some, the natural recovery ability of native plants among protection forest becomes stronger and stronger.There are totally three types of herbaceous plants among the four plots, which are ageratum, panicum repens and Erigeron annuus. The importance values of ageratum are 31.70, 106.10, 117.80 and 93.60. As an exotic species, ageratum has become the dominant species in plot B, C and D among the undergrowth plants. On the other hand, the exotic species has strong occupational trends. Therefore, they become the serious thread to diversity and stability of the ecosystem to the local species among the protection forest. The importance values of panicum repens are 67.60, 87.50, 32.20 and 4.00. Due to the closed distance to the coast, Plot B sufftered from more wind influence, which caused more gaps and species diversity, where the amount panicum repens is more than plot A. while comparing plot Awith plot C and D, its amount become decreasing. It indicates that the living space for panicum repens becomes narrower gradually as the distance increases from the coast. Commelina, the native plant, was not found in plot A. While its importance values among B, C and D are 5.80, 72.00 and 93.40, which shows a trend of increasing. It indicates that as the increase of the climax water level grows, the living space for commelina become larger, and the natural recovery ability for the undergrowth plants among protection forest grows, as well.Casuarina coastal protection forests of different gradients have different community diversities. As the increasing water level of the climax, the Simpson's diversity index, Shannon-Wiener's diversity index and McIntosh diversity index of gradients are showing uprising in different degrees.(2). The community among casuarina coastal protextion forests of different gradients suffer wind disturbance of different degrees. After disturbance by typhoon, as the increasing distance from the sea, the wind disturbance to the protection forest reduces, and the growth of the casuarina gets better, death rate gets lower significantly, and both the average DBH and height increased gradually. The density of stand also affects the protection forests by the wind disturbance to some extent.(3). The physical properties of the four plots of different human disturbance tend to be the same, in the soil layer between 0~20cm, the soil capacity of thinning areas and protected areas is smaller than harvesting area. Among field capacity, capillary porosity and gross porosity, the thinning areas and protected areas are both larger than human-affected areas and litter collection area. Index varies a bit among soil layers between 20~40cm and 40~60cm. As to the soil PH, same trend happen among the four sample plots, which are all the litter collection area < logging < thinning area < protected area. As the PH value grows, the soil acid decreases.As to the soil fertility, solid organic matter in the four plots between soil layers in 0~20cm, 20~40cm and 40～60cm gradually reduced. In other words, as the soil depth increases, the organic matter become less. The amount of available N, P, K, as well as total N, P and K in the soil layer between 0~20cm showed the same variation among thinning areas and protected areas are all higher than logging areas and litter collection areas. While between layers of 20~40cm and 40~60cm variation shows a bit, which may be connected with the nutrients that are continuously generated from the litter decomposition, and nutrient are continuously absorbed by plants.It is concluded from single correlation analysis that each index among the physical and chemical properties of soil are significantly correlated, which indicates that all the physical and chemical factors in the soil are not separated, but mutually influenced, and have sort of connection. After principal component analysis, the first principal component contains the variation information for soil organic matter, available N, P and K, as well as total N, P and K. The second principal component contains variation information for soil bulk density, gross porosity and capillary porosity. The third principal component contains the variation information for soil water content, soil PH and available P. The cumulative variance of the first principal component is the most, which therefore plays an important role to the soil fertility. Soil organic matter, available N and K, as well as total N, P and K reflects the physical and chemical properties of the soil, which can be noticed that the chemical properties of the soil plays an important role to the plant.