## 1 Introduction  
Land use and land cover change (LULC) is the primary driver for global change [1; 2; 3; 4]. In particular, intensive human activities have exerted far-reaching impacts on the structures and functions of ecosystems, which accordingly affect the capacity of ecosystems to provide goods and services [5; 6; 7; 8]. This is particularly true for the Agro-Pastoral Transitional Zone of Northern China (APTZNC), which acts as an important ecological barrier in north China, providing a range of ecosystem goods and services, such as food provision, carbon sequestration, culture heritage, and climate regulation [9]. Previous studies have focused on the consequences of land use and land cover (LULC) changes on ecological functions from the perspective of landscape components and patterns. At regional scales, different land use types will directly affect the vegetation types, and change the surface biophysical parameters, and spatial patterns of the ecosystem functions [10; 11; 12]. Conversion of native vegetation to land uses might result in the permanent and semi-permanent loss of biomass and fluxes of carbon from soils [13; 14; 15], an increase in soil erosion (ERO) [16], and a decline in soil nutrition [17]. On the other hand, reductions in land use intensity have the potential to increase carbon stocks and prevent land degradation, through biomass growth and nutrient accumulation in soil [18; 19]. Meanwhile, it should be noted that not only the landscape components but also the landscape spatial pattern could indirectly affect ecosystem functions via the changing ecosystem processes [20; 21; 22; 23; 24]. Hence, it is of great importance to emphasize the landscape spatial pattern. For example, [PERSON] et al. [25] studied Xilinhot city in northern China at the basin scale and found that the increasing grassland aggregation and concentrated afforestation can increase net primary production (NPP), and promote soil conservation and water retention, while reducing soil ERO. Therefore, we tried to focus on both the land use components and spatial patterns to analyze its impact on ecosystem functions. The ecological effects of LULC change can be simulated and analyzed by ecological models, which are considered powerful research tools [26; 27]. Their utilization is growing for the management of natural resources [28; 29; 30] and the prediction of the effects of disturbances, such as global change, by simulating ecological processes and mechanisms [31; 32; 33]. For example, the Carnegie Ames Stanford Approach (CASA) is widely adopted to generate NPP [34; 35; 36]. [PERSON] et al. (2007) completed the localization of CASA parameters in China. The revised wind erosion equation (RWEQ) was developed and matured based on field tests to simulate soil wind erosion [37; 38]. However, there are only a few quantitative studies on the intrinsic link between land use structure and ecological function based on process-based ecological models. For instance, the CENTURY model is used for northern China to simulate the dynamics of carbon and nitrogen in dryland in the northwest [39; 40; 41]. The Biome-BGC Carbon Model is often adopted to simulate and predict the carbon dynamics in a forest ecosystem [42; 43; 44; 45]. Therefore, it is necessary that a comprehensive and quantitative method is developed, in which an internally consistent set of fine-resolution LULC scenarios would drive process-based ecosystem models and identify the possible consequences and then develop practical mitigation and adaptation strategies in the APTZNC [46]. Information on future LULC is needed to identify the consequences of LULC on ecological functions. At present, the IPCC Special Report on Emissions Scenarios (SRES) framework, a standard for scenario studies, has been successfully employed to generate the evolution of land use under multiple drivers [47; 48; 49].