Environmental benefits evaluation of different agroforestry systems in Hoa Binh Hydropower Station Reservoir Area of Vietnam

Abstract: Nowadays, agroforestry farming is a major issue in Vietnamat midland and mountainous region as it has to satisfy the demand of forest production and ecosystem protection. Compared to some other types of forest, agroforest has demonstrated outstanding strength as it provides landowners with early and fast income generation. Therefore, developing agroforest becomes a trend when the research on land use gets much attention. However, environmental efficiency of agroforest is quite varied and closely reliable on the structure of the forest system. Taking into consideration of both environmental condition and the efficiency at the same time is significant not only in evaluating the current situation of the forest but also in improving its structure, thereby reaching environmental goals. Nevertheless, there is a shortage of research on above problem in Hoa Binh hydropower reservoir environment. Due to this restriction many agroforests were in failure to enhance their economic and protective functions and the forest also showed low stability. In order to have a part in solving the aforesaid inadequacies, this paper has been conducted.The environmental protection and soil conservation of vegetation have high requirements in hydropower station reservoir area. Finding a kind of land use pattern that can meet the interests of all parties is particularly important in the context that moving local residents out of the reservoir area is impossible. In the present study, the four main agroforestry system patterns (Acacia mangium - Zea mays; Acacia mangium - Manihot esculenta crantz; Eucalyptus camandulensis - Oryza sativa; Acacia mangium - Manihot esculenta crantz - Zea mays) were employed as the research subjects in two different areas (Thung Nai Commune, Cao Phong District and Vay Nua Commune, Da Bac District) of Hoa Binh hydropower station reservoir area in Vietnam. Multiple structural indicators such as plant species composition, morphemic structures, density and canopy of the plantation used, coverage of shrub layers as well as environmental indicators such as fertility retention, water use efficiency and soil conservation through prohibition of erosion were used to evaluate the four proposed agroforestry patterns employed in the study and to find out the most appropriate one. The results showed that among the four patterns, Acacia mangium - Manihot esculenta crantz - Zea mays pattern had the highest comprehensive environment benefit and soil conservation benefit; on the contrary, Eucalyptus camandulensis - Oraza sativa pattern scored lowest. So, the former planting area should be encouraged to increase, and the latter planting area should be reduced in the future practice. On the basis of Acacia mangium - Manihot esculenta crantz - Zea mays pattern, we put forward the Acacia mangium - Manihot esculenta crantz - Zea mays - Cinnamomum cassia pattern that has higher expectations of comprehensive environmental benefits. It's proposed as a better choice for the application of agroforestry system in Hoa Binh hydropower station reservoir area. And this research also provides a reference for the areas with similar climatic and environmental conditions with Hoa Binh hydropower station reservoir area.