To closely track the frontiers of earth sciences and to meet the requirements of national ecological construction, the hilly loess area was selected as a major study site to explore the theory and comprehensive integrated methods of sustainable land use assessment. On the basis of the study on relationship between different land use structures and their ecological processes and the effects of different land use structures on the ecological and socioeconomic results in the hilly loess area at different scales, this research had advanced the theory and comprehensive integrated methods of sustainable land use assessment. Some sustainable land use modes suited for the hilly loess area had been developed, which can be regarded as a scientific basis for the control of soil and water loss and the implementation of the “Grain for Green policy”.

(1) The systemic study on the relationship of land use structures and ecological processes was implemented by the pioneer integration of “Scale-Pattern-Process” paradigm, which can be regarded as a scientific basis for the rational land use.

The study of the relationship between land use structures and ecological processes had been carried out at three scales including single land use type, slope and small catchment. On the basis of field observation and sample analysis, the effects of land use pattern on soil moisture, soil nutrient and soil erosion had been studied in the hilly loess area. Achievements can be drawn as below: (a) The land use patterns, such as “forest-grassland-slop cropland” and “forest-grassland-terrace”, were the optimal land use pattern in the hilly loess area for its higher capability of soil nutrient conservation and lower moisture content in the early stage. (b) Factors including slope, land use types, vegetation coverage and characteristics of runoff in the slope land in the establishment of spatial distribution model of soil moisture of hilly loess slope land. The model can be used to the quantitative forecasting of spatial distribution of soil moisture in hilly loess slope land, which expands the moisture model from “ the vertical model” of “Soil-Plant-Atmosphere Continuum (SPAC)” to “horizontal model ” of slope land, which also filled the gap of spatial distribution model of soil moisture of the slope land in the loess hilly area. (c) The findings of land use change regulation and spatio-temporal variation of soil moisture. The major factors affecting the vertical distribution of soil moisture were land use, topographical feature, slope gradient, slope position and altitude. However, the major factors affecting the seasonal variation of soil moisture were precipitation, slope gradient, altitude, slope aspect and position. The results can be regarded as scientific basis for the effective use and conservation of soil moisture. (d) The simulation of the effect of soil and water loss under different land use and ‘grain for green’ policy scenarios at catchment level. The calculation and comparison of different scenarios showed that conversion of slope cropland(＞25°) to forest and grassland have a better environmental effect, that is, it decreased the velocity of flood runoff by 47.23%, the volumn of runoff by 40.03%, and the soil erosion by 48.68%, which can be regarded as the quantitative decission support data for the planning of the “Grain for Green project”.

The result of this study can be regarded as an important scientific basis for the sustainable land use in the hilly loess area, and it will be very useful for the implementation of the “Grain for Green project”. Meanwhile, this research was also selected and represented as the excellent scientific product of the National Foundation of Natural Sciences.

(2) The study had advanced the assessment theory and established the comprehensive assessment methods on sustainable land use.

On the basis of long-term systematic research, this study had advanced the assessment theory on sustainable land use, and also established the comprehensive integrated methods on sustainable land use. (a) During the assessment of sustainable land use, the most important thing should be considered was the integration of land suitability assessment with the relationship analysis of landscape pattern and ecological process. On the basis of land suitability assessment and through the correlation analysis of land use pattern and ecological process, this study had showed the effects of different land use patterns on matter, energy, water and organism under the change of socioeconomic and environmental factors, and some land use modes had been put forward for the hilly loess area. (b) The establishment of integrated assessment method including ecological assessment and socioeconomic assessment. In other words, the methods for the comprehensive assessment of sustainable land use were developed on the basis of the overall considering of ecological, economic and social factors and the integration of the major factors at different scales such as field, landscape and regional scale. Therefore, the methods established had a character of practicability and innovation. (c) There is a lack of process analysis and dynamic assessment in the method for intrinsic assessment of sustainable land use. To solve this problem, the method formulated in our study at the Quanjiagou catchment in northern Shannxi province had considered the assessment of land quality and soil erosion risk together and had made an advance in the land assessment system. The integration of process analysis and ecological effect analysis had been highlighted in this study. Our research results had got a high appraise from the national and international specialists after being published in the international journal. The experts on land assessment from USA and the United Kingdom think there is an innovation in theory and methods in our study, and the accuracy and applicability of land assessment were improved accordingly. In the case study of land use assessment at Danangou catchment in northern Shannxi province, the application of integrative assessment method including the comprehensive considering of ecological assessment, economic assessment and social assessment will help us setting a very useful scientific basis for the implementation of “Grain for Green project” at the catchment scale.