## 1 Introduction  
The terrestrial ecosystem plays a key role in climate change, and life support systems for human survival and development depend on it [1]. Due to the unrestricted exploitation and utilization, China's ecosystem shows a development tendency from structural damage to functional disorder [2], especially the vulnerable ecosystem in arid and semi-arid areas. The terrestrial vegetation, the primary producer in the ecosystem, refers to a vitally essential component of the terrestrial ecosystem [3]. Change in vegetation is sensitive to climate change and human activities as an indicator [3,4]. It is of great ecological significance to study the impacts of climate change and human activities on terrestrial ecosystems through vegetation [5]. Precipitation and temperature act as critical factors in controlling vegetation growth [6,7]. The growth period of vegetation and the composition and morphology of vegetation itself will be affected by climate change [8, 9, 10]. Studies have shown that the driving factors of climate on vegetation have gradually shifted to precipitation and temperature [11,12]. Therefore, precipitation and temperature, as the two most direct and significant factors, are usually selected to study the influence of climate factors on vegetation change [13]. [PERSON] et al. [14] showed that precipitation and temperature were the main factors affecting NDVI changes in northwest China. [PERSON] et al. [15] showed that precipitation had a more obvious effect on vegetation growth in arid areas of northwest China, and the influence of precipitation on grassland was much greater than that on the forest. [PERSON] et al. [16] showed that under the influence of climate change, vegetation in the Loess Plateau, North ChinaPlain, Qinghai, Inner Mongolia, and Liaoning border areas became green. Precipitation and temperature promoted vegetation growth, while wind speed inhibited it. In addition, the change of vegetation is also affected by human activities [17]. Human activities often show duality to vegetation growth, with vegetation changes more obvious in areas where human activities are more frequent and to a lesser extent in uninhabited areas and areas where human activities are less frequent [18]. The urban vegetation cover is often negatively affected by urbanization to a certain extent [19], but major ecological engineering projects will make vegetation cover develop in a positive direction [20]. Land use change is also often used as a means to examine the impact of human activities on vegetation change [21], and the impact trends of different land use situations on vegetation are different [22]. Land use change can have a positive effect through afforestation and grass planting [23] or negative effects through unsustainable agricultural practices and expansion of built-up areas [24]. [PERSON] et al. [25] found that the land use change induced by afforestation was the main factor in vegetation dynamics in semi-arid areas of northern China. [PERSON] et al. [26] studied the influence of human activities on vegetation in the Qinba Mountains through the change of afforestation area, and the results showed that land use change was an important factor leading to NDVI changes. Ordos City lies in a semiarid-arid farm pastoral region in north China. As an ecological security barrier and ecological vulnerable and sensitive region, desertification, induced by overgrazing, reclamation, mining, climatic change, and so on, has been a serious problem. In the past several decades, many ecological conservation and restoration programs have been put into effect [12]. Revealing the change of vegetation and terrestrial ecosystem further, and recognizing the attribution of influencing factors, including climate factors and human activities, are of great consequences to assessing the effect of the ecological programs.