Landform type and topography are also important factors for vegetation distribution [16; 17]. In addition to change trends, significant spatial heterogeneity exists in the vegetation, and various settings have varied vegetation features [18; 19]. Meanwhile, it is not always the case that one factor has an independent effect on vegetation development [20; 21]. Geographical detectors can effectively identify the influencing factors of spatial differences in vegetation, as well as the importance of each factor and how those factors interact with one another [17; 22]. Geographical detectors have been successfully applied to identify the influencing factors of vegetation [23; 24]. Some studies based on geographical detectors focused on analyzing the causes of spatial heterogeneity of vegetation, but ignored the causes of vegetation change trends. A comprehensive analysis of the driving forces of vegetation growth from the aspects of spatial heterogeneity and change trends is conducive to obtaining more reliable results. The mountainous area of the Haihe River basin (MHRB) is an important ecological barrier and water source in North China. Vegetation increase in the MHRB is good for wind prevention, sand fixation, and the reduction of soil erosion. Additionally, vegetation is crucial for increasing carbon sinks in the MHRB and for enhancing the quality of the air, water, and soil. The Three-North Shelterbelt Development Program, the Greening Project of Taihang Mountain, and the Grain for Green Program have all been implemented in the MHRB to safeguard the ecological environment. One of the primary goals of ecological engineering implementation is to increase forests and vegetation coverage. A requirement for the successful use of ecological engineering is an understanding of the trend and underlying causes of vegetation fluctuations. A reference point for agricultural production in the MHRB can also be found in the identification of elements that impact vegetation, as changes in vegetation on cultivated land reflect the growing status of crops. The increasing trends of NDVI have been demonstrated during the periods of 2000-2013 and 2002-2018 in the Haihe River basin (HRB) [25; 26]. The increased net primary productivity of the MHRB has also been revealed from 2000 to 2020 [27]. Precipitation and NDVI correlate more strongly than temperature in the HRB [25]. Reforestation is a clear cause of NDVI change in the MHRB [26]. Runoff in the MHRB has declined over the past few decades [28; 29], while vegetation plays a crucial role in the eco-hydrological process [30; 31]. An adequate understanding of vegetation change is also a prerequisite for eco-hydrological research and water conservation in the MHRB. Most of the previous studies in the MHRB relied on a single vegetation indicator. Analysis based on different indicators is helpful to further understand the vegetation changes in the MHRB. LAI is a key index of vegetation greenness, as well as a basic variable for many ecological and hydrological models [1; 15]. GPP is an important indicator of terrestrial carbon sink [12]. The combined use of LAI and GPP can reliably reflect vegetation growth. In addition, the responses of LAI and GPP to climate change may be different [2]. Therefore, comparative analyses of LAI and GPP can obtain more comprehensive results. Temperature, precipitation, and solar radiation were employed to explore the relations between climatic elements and vegetation in the MHRB, while humidity index and VPD are infrequently taken into account. In addition, the interaction between various factors and the growth patterns of vegetation in different environments still needs to be further explored in the MHRB.