| The Loess Plateau is the concentrated area of China's ecological problems and the key area of ecological restoration.Small watershed is the typical eco-economic unit and soil erosion control unit in Loess Plateau,and the Grain to Green Program(GTGP)combined with watershed management measures have effectively improved the ecosystem and environment in the Loess Plateau and enhanced the development of local society and economy.However,in the process of governance,there are some problems like the artificial forest and grassland degradation,over consumption of water,low economic efficiency et al and these problems have seriously affected the sustainability of program achievements and management of small watershed.So,in this study,5 typical small watersheds were selected from the Loess Hilly Region of northern Shaanxi(LHRS)-the core area of the Loess Plateau.By using system analysis,experimental research,social investigation and literature analysis method,the landscape mode status of typical small watershed was analyzed,and a evaluation model was construct to evaluate the comprehensive benefit of different landscape mode and to discover the problems in these agroforest landscape configuration scheme,at last the optimization measures for watershed and landscape element were put forward and been used to adjust the typical watersheds.The main research contents and results are as follows:(1)The watersheds in typical counties in LHRS were extracted and their morphological characteristics were studied by using the spatial analyze tools in ArcGIS software and the SWAT model.The morphological characteristics and current situation of landscape configuration scheme were studied and then the author summarized the typical landscape configuration mode in the study area.The results showed that the average area of small watersheds in LHRS is 357.45hm2-375.80 hm2,mostly they are long and narrow.The land with slope degree >15° are common in the study watersheds and most of the land use types in the watersheds are ecological service-oriented landscape(71.71%-97.23%).Based on the proportion of different kinds of landscape,the small watersheds configuration mode was summarized to five forms: comprehensive ecological governance mode,ecological governance and economic orchard mode,ecological governance and crop grow mode,ecological governance and orchard with crop grow mode,ecological governance and mixed farming mode.The agroforest landscape configuration scheme was jointly derived by different factors.(2)The ecological benefits of different restoration vegetation were studied through vegetation investigation and soil sampling in typical vegetation lands and building slope runoff field.The results indicated that the artificial vegetation restoration have significantly increased surface land cover,improved litter return and increased species diversity.The vegetation restoration also significantly promotes the accumulation of soil organic carbon,total nitrogen and total phosphorus,the increase of soil enzyme activity,the increase of soil microbial biomass and improvement of soil physics condition.In addition,the vegetation restoration land significantly decreased the surface runoff by 21.79%-69.65% and soil erosion by 31.28%-70.93% in different lands compared to cropland.The overall ecological benefits of vegetation restoration were ordered as arbor land> shrub land> grassland.(3)Farmers' socio-economic condition,attitude and behavior were investigated use social survey method,and the results were analyzed by the theory of planned behavior and binary Logistics model.The results showed that the implementation of GTGP decreased farmers crop land by 39.59%,but improved the land quality.The GTGP leads to grain productivity impairment and agricultural structure changes.The labors transfer to non-agriculturization work and the migrant workers average increased by 0.8 in each family.Moreover,the living condition and environment were significantly improved by GTGP.About 94.24% of the responded farmers support the GTGP,but there are also 46.63% of them intend to cultivated in the vegetation lands after the subsidy stopped.Farmers behaviors is significantly affect by their intention and their intention is jointly affected by their attitude towards behavior,the social norm and behavior perception.What's more,the implementation of GTGP significant increased farmers' household income and outcome by 190% and 359%.The proportion of agriculture in income and outcome are both decreased.The Engel coefficient and Gini coefficient are both declined and the labor production efficiency is enhanced greatly.(4)The emergy analysis method was used to study the input,output and sustainability of farming system in 3 typical configuration modes.The results showed that the 3 modes are all greatly depend on external resources and have limited utilization degree for local resource,especially for the mode main plant fruit tree,in which the local resource only accounted for 12.18% of the total input.The fruit and vegetables are the main emergy outputs in 3 modes with proportion of 59.70%-98.62%,and the grain followed.The large amount of external resources lead to enormous pressure to local environment.The sustainability of main plant fruit tree mode is the lowest,and the output efficiency of main plant grains is the lowest.Comparison of the three modes showed that planting both grains and fruit trees had better sustainability and high production efficiency,which is better than other two modes and suit to the LHRS.(5)Based on the related literature analysis,experiment determine,and social-economic survey,the evaluation index system to evaluate the typical agroforest landscape configuration scheme in GTGP watershed in LHRS was put forward by using frequency analysis and expert consultation methods.This index system includes 8 index factors(vegetation recovery,conservation of water and soil,carbon fixation and oxygen release,economic income,production efficiency,food security,industrial structure and social impact)and 19 indexes.The index weight was determined for two focus: focus on ecological restoration and focus on social-economic development,based on expert scoring method and analytic hierarchy process.In addition,the comprehensive index evaluation model and class partition table was built,and the 5 typical watershed configuration mode were evaluated and analyzed.Based on the evaluated results,the problems of configuration mode in study area were summarized,include lacking whole composition and scientific development planning,the ecological achievements and social-economic achievements are discordant,small proportion of productive cropland,population pressure lead to high pressure of source and environment in watershed,traditional agriculture influenced the integral development of watershed,the tree lack of manage and protect and then leads to low ecological benefits,labor transfer only have limited effect on local social-economic development.(6)By using several methods like literature analysis,field research,experimental study and expert consultation,based on the evaluate of typical watersheds,the author proposed 5 kinds of optimization methods for improve typical agroforest landscape configuration scheme in GTGP watershed in LHRS,like construct multi layer soil and water prevention engineering system,rational planning and adjustment of agricultural industrial structure.And 10 kinds of specific measures were put forward for optimize 4 kinds of landscape element,like inefficiency forest remould,convert abrupt slope and low yield economic orchard to vegetation land,remould barren and wasteland,and high yield farmland construction.Based on the above measures,the 5 typical watershed configuration mode were optimized and evaluated.The results showed that this measures have significantly improved the evaluation index score both in ecological and social-economic focus,and significantly enhanced the watershed integrated system services.(7)A software named “GTGP small watershed comprehensive benefit evaluate software V1.0” was design and developed.This software includes 5 functional modules: system management,data management,watershed evaluation,data query and decision making,which can be used evaluate the score of different index factors and comprehensive evaluation by input the basic information of watershed,and provide technical measures for watershed optimization.From analyzing the current configuration mode and propose the optimized model,the present research put forward systematic direction and approaches for evaluation and optimization of agroforest landscape configuration scheme in the LHRS through integrating multiple theories and methods.The results are likely to provide theoretical direction for comprehensive small watershed management in Loess Hilly Region,and be useful for guiding the evaluation and optimization of agroforest landscape configuration scheme in the Loess Plateau. |
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