Abstract
Recently, the impact of global warming has increased the intensity of climate extremes and the frequency of natural disasters nowadays. Typhoons are the most serious weather systems that threaten Taiwan annually, and they cause not only flooding in many areas but also debris flows in the areas of the downstream. A stable eco-environment has been destroyed by typhoons, which causes the decline of ecosystem functions, and it is hard to restore its productivity and environmental functions. According to our national policy, the area of the ecosystems and environment damage severely need to be restore rapidly. Due to the climate change forming degraded land, how to carry out ecological afforestation is worth discussing the issue. Therefore, we chose the degraded land on the floodplain that was flooded by Morrakot typhoon in 2009 in Taitung Taimalee. In order to solve the problem, we conducted a research about how to improve afforestation technologies and find what kind of trees which can grow better and quicker in degraded land. We planted Casuarina equisetifolia L., Acacia confuse Merr., Koelreuteria henryi Dummer, Fraxinus formosana Hayata, Terminalia catappa L., Pongamia pinnata (L.) Pierre ex Merr., Melia azedarach L., and Hibiscus tiliaceus L. in the area of the floodplain in Taimalee River, and we carried out a fertilization experiment to understand the effect of fertilizer on the growth performance of the experimental trees. According to the results of the soil analysis, the content of the organic matter, total N, P and K were lower than the standard value, showed that the soil on the floodplain is a nutrient-poor and unbalanced barren land that will hinder the growth of plants. According to the results of the afforestation 1.5 years later, comparing the average survival rate of the plantation trees on different treatments, 88% on fertilization treatment was higher than 83% on non-fertilization treatment. Comparing the overall growth performance of the plantation trees on different treatments, the average net basal growth were 2.9cm on Fertilization treatment and 2cm on non-fertilization treatment, the average net high growth were 109cm on Fertilization treatment and 66cm on non-fertilization treatment, and the average net crown diameter growth were 105cm on Fertilization treatment and 74cm on non-fertilization treatment. The growth performance on non-fertilization treatment, Casuarina equisetifolia L., Acacia confuse Merr., and Pongamia pinnata (L.) were greater than others, and they are well-adapted species in degraded land. Hibiscus tiliaceus L., Terminalia catappa L. and Melia azedarach L. are able to adapt to be potential species, and the growth of Fraxinus formosana Hayata and Koelreuteria henryi Dummer are almost stagnation and the average survival rate are less than 50%, and they are poorly adapted species.The growth increment of the plantation trees on fertilization treatment, Melia azedarach L., Terminalia catappa L., Acacia confuse Merr.and Hibiscus tiliaceus L. are greater than others, and they are well-adapted species in degraded land. According to the survey results, Casuarina equisetifolia L., Acacia confuse Merr., and Pongamia pinnata (L.) have mycorrhizae which can promote the absorption of the water and nutrients from soils increasing the trees growth, and they can be well-adapted species in the area of the floodplain without fertilization. Melia azedarach L., Terminalia catappa L. and Hibiscus tiliaceus L. can be well-adapted species in degraded land through fertilization. Floodplain is a barren land and belongs one of the area of the environmental stresses on the afforestation. Because afforestation conditions are harsh, plantation trees are better with mycorrhizal to plant as a priority, and there isn't mycorrhizal in plantation trees which can be fertilized as well-adapted species achieving the goal of the afforestation rapidly .