| Land is a very special resource. It is not only the important carrier for generation and change of natural environmental element but also the material assurance for subsistence and reproduction of human being, in addition, as the community characterized by natural quality and social economic property, the land as valuable resource plays an important fundamental and strategic role in economic construction and social development. Utilization of land resource is the complex social economic process in natural reproduction and economic reproduction under the persistent or periodic intervention of human activity, while the optimum distribution of land resource should be an important means to mitigate contradiction between human and land and implement sustainable utilization of land resource.The paper presents the characteristic of space time discrepancy of land utilization in southern area and typical area on loess plateau from different time space scales, adopting interpretation results of TM image remote sensing in30years from1980,2000to2010through RS and GIS integration and mathematical model, spatial statistical analysis and field investigation, taking southern area and internal typical area on loess plateau as research object based on the research of natural region division on loess plateau and shows the quantitative analysis of the relationship between various land use types and their influencing factors in southern area and four typical areas on loess plateau through combination of spatial sampling with Binary Logistic regression model based on research of the characteristic and scale of land utilization.And according to the problems existing in land utilization in various typical areas to build evaluation model to perform dynamic evaluation on land bearing capacity in every typical area in qualitative and quantitative manner. Finally, the two schemes that are to combine the grey linear programming model (GLP) with CLUE-S model CA-Markov model respectively are put forward for different typical areas based on valley unit and based on urban economic zone so as to apply the optimum results to the spatial unit adopting the two schemes based on research and appraisal of land suitability as well as quantitative control and structure optimization in terms of land utilization in different typical areas and implement the ecology oriented optimum distribution scheme for land resource to maximize ecological service value and economic benefit of land resource system through research, experiment and comparison of different schemes in different typical areas. The research findings are as follow:(1) The land use types in southern area on loess plateau are relatively complete, with the largest percentage of arable land, its percentages in all periods are all more than40%; meadow and woodland are next to it in this respect. In general, the area of land use types for the past30years (1980-2010) in southern area on loess plateau has changed to a certain extent, of which the arable land and unused land area have been on the decrease, while the area of other land use types have been on the increase, of which the land used for building has been on sharp increase. The land use type that plays a leading role in structural changes of land use in southern area of loess plateau is arable land, land used for building and meadow. The analysis results of transition matrix for land use indicate that the most significant change in land use in southern area on loess plateau for the past30years has been in arable land, the quantitative change shows that there has been2577.72km2of arable land changed into other types, of which the land used for building accounts for the largest percentage, being up to1157.07km2; the expansion of land used for building, implementation of the policy on returning farmland to forest and grassland in ecologically fragile area and agricultural restructuring are the primary cause for reduction in arable area. It is observed from spatial distribution that Guanzhong Plain in Shaanxi, Fenhe River valley in Shanxi and northwest in Henan have changed markedly in arable land use utilization, with significant increase trend in land used for building in the past30years. The area of land used for building has increased by1275.73km2. The region with area of land used for building increased is less than the region with area of arable land decreased, indicating that some arable lands have been changed into woodland and grassland in the period and it is observed that the policy on returning farmland to forests or grassland (Especially returning farmland to grassland) have achieved remarkable results.(2) It is observed from the analysis of land use change in two typical areas selected that the change of land use in every typical area shows reduction in arable land and enlargement in land used for building, but the causes for reduction in arable land are different, the reduction in arable land in two typical areas based on valley unit are as a result of the policy on ecological environment improvement (Such as policy on returning farmland to forest or grassland), the second cause is the extension of land used for building, for example, the arable area in lower reach of Yehe River valley has reduced from1818.1932km2at the beginning of research to1739.5037km2in2010, its total area is similar to the meadow area in the corresponding period.The reduced arable area has become forest land, grassland and land used for building in turn, the area of forest land changed from arable land is40.9832km2, and area of grassland changed from arable land is36.851km2, while the reduced arable area in Qianhe River valley has become grassland, land used for building and forest land in turn; from1996to2010,34.34km2of arable land became grassland,6.07km2of arable land became land used for building; in contrast, the reduction in arable land in two urban economic zones has been due to the fast speed of increase in land used for building.The total area of the arable land in economic zone in the southeast of Shanxi decreased from10329.35km2in beginning period to10183.79km2in2010, the decreased arable land mainly became land used for building and woodland,93.87km2of arable area became the land used for building from2000to2010, accounting for0.91%of the initial arable area, and28.29km2of arable area became woodland. In addition, the total area of the arable land in the planned area of Xi'an decreased from6429.96km2at the beginning of research period to6347.80km2in2010. And the decreased arable land mainly became land used for building, grassland and woodland in turn. From 2000to2010,101.04km2of the arable land became the land used for building,82.18km2and39.64km2of the arable land became into the woodland and grassland respectively and accounting for1.28%and0.62%of the initial arable area respectively.(3) Quantitative analysis of land use and influencing factor shows that the natural and human factors associated with different land use types in southern area on loess plateau include landform slope and population density, indicating that the human factor in land use in the area is strong; human activity has been an important cause for the accelerating change rate of the land resource and ecological system, while the landform slope in natural factor is also an important factor related to land use; different land use type, especially the agricultural land and land used for building in urban area show the obvious negative correlation, indicating that landform slope is the restriction condition for land development and utilization. For different typical areas, the factor associated with the probability of occurrence of various land use types and spatial distribution is slope. It shows positive correlation with woodland and grassland in typical area by and large but presents negative correlation with other land types such as arable land and land used for building and water area. In addition, for the economic zone and Yanhe River valley in the southeast of Shanxi, population density is also a factor of influence with a larger contribution rate in land use change. The factors associated with probability of occurrence and spatial distribution in land use type in Qianhe River valley also include temperature condition besides slope, including average temperature and accumulated temperature more than or equal to10℃, especially for land for construction in research area; temperature condition is mainly related to climatic suitability for land for construction in the research area.(4) According to the evaluation results of time space change of land bearing capacity based on the typical area, from2000to2010, for the areas lacking of land bearing capacity in all districts and counties in different typical areas, some areas are stable with a slight decline, some areas are aggravating, while, for the areas with margin in land bearing capacity, some areas are on the decline in bearing capacity level, and some areas with margin in the bearing capacity are on the increase in bearing capacity. Generally, the land bearing capacity in all lands in four typical areas shows polarization differently, but displaying the same trend in general, indicating that the land bearing capacity in research area is on the decline, thus, the efficient and reasonable and scientific land optimization is needed to improve land bearing capacity. As to the polarization in the research area, the areas with margin in land bearing capacity should transfer their grain to the areas lacking of land bearing capacity on the premise of steady development of the economy in areas with margin in land bearing capacity so as to ensure the balance of the land bearing capacity in the research area.(5) Research of the ecology oriented scheme of optimum distribution of land based on CLUE-S shows that the Kappa index of the two simulated typical areas are on the high side, of which the economic zone in the southeast of Shanxi is82.16, while the lower reach of Yanhe River valley is79.37; the simulated effect of the economic zone in the southeast in Shanxi is better than that of the lower reach in Yanhe River valley in typical area. It is observed from the land use demand and structure based on GLP mode and the spatial distribution of land use from2011to2020in economic zone and Yanhe River valley in the southeast of Shanxi simulated by CLUE-S model that the land for construction in two typical areas are sharply increased while the arable lands therein are on the decrease. But the land for construction in economic zone in the southeast in Shanxi increased more. And all arable lands are on the decrease, indicating that the potential for regional economic development and urbanization is superior to that for the lower reach of Yanhe River valley. The water area in two typical areas is on the slight increase, with enlargement of woodland and grassland to varying degrees due largely to the policy on tree planting and returning farmland to forest land and grassland so as to achieve improvement in ecological environment.(6) Research of the optimum distribution scheme based on combination of land suitability with CA-Markov model shows that the main land sections in the current situation of land utilization in the research area of two typical areas need adjustment, of which the arable land in the planned area of Xi'an lies in the north foot of Qinling Mountain, including Zhouzhi County, Huxian County and the south of Chang'an District as well as part of Lantian County, in addition, there is a few of land in the north border between Sanyuan County and Fuping County is to be adjusted. It is observed from the land adjustment that the location unsuitable for arable land shall be adjusted into woodland and grassland, while the arable lands to be adjusted in Qianhe River valley are concentrated in Qianyang County in the southeast of the River Valley, including the middle northeast and southwest of Qianyang County near to Baojing. The lands in border between Fengxiang County and Qianyang County are also to be adjusted. In addition, the lands in Long County in upper reach of the river valley are to be adjusted.The research has made innovation and improvement in the following aspects:①The main meteorological elements on loess plateau about longitude and latitude and mathematical model as well as comprehensive index model are built based on prediction model as theoretical basis, based on which the natural area is subject to division and the division results have been tested. Based on the natural area division on loess plateau, the borderline on the southern area on loess plateau based on natural area division and administrative unit has been presented.②The land use change process for the past30years has been subjected to systemic and comprehensive analysis in the southern area on the loess plateau as research object, and the characteristic and time space discrepancy in land use change in different natural environment and social economic development within the research area have been analyzed by contrastive analysis in typical area.③Quantitative analysis of the character, scale and time space discrepancy of various land use types within research area have been conducted by Binary Logistic regression analysis in the research, in addition, in order to prevent the auto correlation influence of land use types in space, the spatial sampling is introduced to Binary Logistic regression analysis, the new scheme to perform quantitative analysis on the land use change and its influencing factor based on spatial restriction Logistic has been established.④The two schemes that are to combine the grey linear programming model (GLP) with CLUE-S model CA-Markov model respectively are put forward for different typical areas based on valley unit and based on urban economic zone so as to apply the optimum results to the spatial unit adopting the two schemes based on research and appraisal of land suitability based on the quantitative control and structure optimization. The ecology oriented land resource optimum distribution scheme to maximize the ecological service value and economic benefit in the land resource system has been put forward to offer the uniform research idea for development and utilization of land resource, protection of ecological environment and social and economic development.
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