Measurement Of Ecotone Width Between Agro-forest Ecosystems Affected By Grain For Green Program

The definition of ecotone is that in ecosystems where ecological interface is formed between two or more material systems, energy systems and functional systems, and the Transition zone around the interface outward extension of the space domain. The important feature of ecotone is the edge effect. Currently, people have carried out a series of studies about the edge effect on the vegetation and community scale. An unresolved problem is how to determine the location and size of the core area and edge area of the ecosystem.The Grain for Green Program is China's largest ecological restoration and reconstruction projects, and also is one of the measures which could fundamentally prevent and cure increasingly serious environmental issues, e.g. Since the implementation of the program, Many scholars have carried out a series of studies For this program. But articles which about the change and process of spatial pattern that the program caused are rare.Significant biological diversity and the spatial and temporal dynamic of agro-forest ecosystems affected by Grain for Green Program have a very important practical significance. They can help us Understanding the interaction and ecological processes between adjacent ecosystems, they also can forecast the future trends in landscape and ecosystem restoration affected by Grain for Green Program. The study also rarely reported.In this study, attention is paid to the Mountain agro-ecosystem and natural ecosystem, and the moving split-window technique (MSWT) has been used. Diversity indices, e.g. Species richness, Cody, Dissimilarity coefficient ((βjand βs) and important value, have been selected. Squared Euclidean distances (SED), Bray-Curtis percent dissimilarity (PD) are utilized as the distance parameters. At last, based on the vegetation and soil data in the adjacent ecosystems, the best parameter and distance coefficient are obtained by comparison of Species composition and soil nutrient and the more precise eco-tone width is measured. The main results are as follows,1, Curves of Species richness, Dissimilarity coefficient (βj and βs) are basically consistent, and a maximum appears on the edge of the forest. From the rehabilitated land to the natural secondary forest land, regardless of species richness, the βj, βs and Cody index, the values in eco-tone are the largest, natural secondary forest land is the second, and the rehabilitated land is relatively small. This reflects the role of the edge effect which has the potential to increase species diversity.2, Based on the Species richness, Dissimilarity coefficient (βj and βs), Cody index and Importance value, distance coefficients of SED curves in the series of29m near the transect are the biggest, a peak value appears in each of these curves. This indicates that the heterogeneity in this position is the largest, and since the ecological patterns of the vegetation and community have changed sharply, as a result that this peak values appear. The curves show that change trends of Species richness are consistent with Dissimilarity coefficients and the homogeneity ranges are also quite obvious. These three parameters could be viewed as good parameters which are able to determine the community boundaries and width in the eco-tone transect. Moreover, they all are of ecological significance and have high practical value.3, The pH value, organic matter and total potassium content of the soil show obvious spatial distribution, the rehabilitated land displays the highest value. Along the rehabilitated land to a natural secondary forest, the pH value and potassium content gradually decrease, and natural secondary forest displays the lowest value. In contrast to the pH value and total potassium content, organic matter content of the rehabilitated land is the lowest and organic matter content gradually increases along the rehabilitated land to a natural secondary forest. Natural secondary forest has the highest organic matter content.4, Based on data of pH, organic matter content and available nitrogen-three soil indicators, SED curves in the series of29m near the transect are the biggest, a peak value appears in each of these curves. This indicates that the heterogeneity in this position is the largest, and since the ecological patterns of the vegetation and community have changed sharply, as a result that this peak values appear.5, To a certain extent, the species composition and soil nutrients can better reflect the width of the abandoned land influenced by the rehabilitated land-Yunnan pine forest eco-tone. In contrast with other soil parameters, available nitrogen is better indicators. However, there is an interference peak on the curve of available nitrogen around19m. And since soil indicators are more susceptible to the length of the eco-tone transect, in contrast with Species richness, Dissimilarity coefficient βj and βs, for the width of the abandoned land-Yunnan pine forest eco-tone, these three species diversity index have better classification results, the species composition has a greater advantage. 6, SED curve trend is generally consistent with the PD curve, and the respective peak value and the peak width have a good coincidence. The phenomenon represents that the classification results of the PD function are basically the same as ones of SED. The difference is that, compared with the SED, the PD function has a large fluctuation and is strongly affected by strong interference from the small peak when it is used to divide the homogeneous community area, and SED can reflect the ecotone biodiversity and soil nutrient variability better. In contrast, SED is able to better reflect the kurtosis changed with the environmental gradient of the eco-tone transect, this shows intuitively in transect series split-window distribution diagram.7, In this study, for the eco-tone of agricultural-forest ecosystems, we used moving-split window technique to measure the width. The better diversity indicates are at Species richness and diversity index (βj and βs), the better soil indicate is available nitrogen,the better distance coefficient is SED. The results show that the agro-forest's width is9m based on diversity index and is11m based on soil nutrient. Because the peak is sharp and narrow, we draw the conclusion that this eco-tone is a sharp type.