To explore the spatiotemporal evolution of carbon sinks in Shaanxi Province, and their impact mechanisms, this study used panel data from 107 counties (districts) in Shaanxi Province from 2000 to 2017. First, we conducted spatial distribution directional analysis and exploratory spatial data analysis (ESDA). Then, we constructed a geographic spatial weight matrix and used the spatial panel Durbin model to analyze the driving factors of carbon sink changes in Shaanxi Province, from the perspective of spatial effects. The results showed that: (1) The temporal evolution of carbon sinks during the study period showed an overall upward trend, but the carbon sinks of counties (districts) differed greatly, and the center of gravity of carbon sinks, as a whole, showed the characteristics of “south to north” migration. (2) The carbon sinks of Shaanxi Province have a significant positive global spatial autocorrelation in geographic space. The local spatial pattern was characterized by low-value agglomeration (low-low cluster) and high-value agglomeration (high-high cluster), supplemented by high-value bulge (high-low outlier) and low-value collapse (low-high outlier). (3) The result of the spatial measurement model proved that the spatial Durbin model, with dual fixed effects of time and space, should be selected. In the model results, factors such as population, per capita gross domestic product (GDP), local government general budget expenditure, and local government general budget revenue all reflect strong spatial spillover effects. Accordingly, in the process of promoting “carbon neutrality”, the government needs to comprehensively consider the existence of spatial spillover effects between neighboring counties (districts), and strengthen the linkage-management and control roles of counties (districts) in increasing carbon sinks.

The study of the ecological effects of the Sloping land conversion program (SLCP) has great significance for afforestation optimization policies based on cost-effectiveness. This paper uses the panel fixed effect model and the panel threshold model to study the ecological effects of fiscal investments in the SLCP at the county level in Shaanxi Province of China. The regional ecological performance indicated by the normalized difference vegetation index (NDVI) has improved after the implementation of the SLCP, but the vegetation suffers degradation risks due to the cessation of subsidies. The results demonstrate strong support for a time lag effect, an effect of diminishing marginal returns, and a threshold effect whereas a significant but negative direct effect of SLCP’s fiscal investments on the vegetation. Specifically, it takes approximately four years after fiscal investments for the NDVI to realize the greatest investment performance. The marginal contribution of fiscal investments to ecological performance reveals an increasing trend initially, followed by a decreasing trend. In addition, the ecological effects of fiscal investments in the SLCP are moderated negatively by ecological endowments. The results indicate that fiscal investments in the SLCP should consider its cost-effectiveness in policy design and improvements.

Determining the price of water yield service is the core of watershed compensation. This is necessary to establish a reasonable and scientific compensation mechanism and achieve the efficient management of water. Unlike previous studies, this study establishes a theoretical model of pricing and a compensation mechanism for achieving a balance between the supply and demand of water yield service. A panel threshold model is used to estimate the production elasticity of water for pricing water yield service. Then, we analyze the spatial and temporal changes of the price and the compensation amounts of water yield service in the Wei River basin, China. The results show that: (1) The water marginal contribution to regional GDP meets the law of diminishing marginal return in the form of the threshold effect. When water input amounts (logarithm) are on both sides of 9.449, the marginal contribution is significantly different. (2) The price of water yield service shows an increasing trend. It was CNY 47.27/m³ in 2015, increasing by 472.94% compared with 2000 (CNY 8.24/m³). The spatial distribution was “high in the southeast and low in the northwest”. (3) Total payment amounts increased from CNY 33.1955 billion in 2000 to CNY 227.1302 billion in 2015 and were mainly distributed in relatively developed areas. The acceptance areas were concentrated in relatively undeveloped areas. Total acceptance amounts increased from CNY 2922.2 million in 2000 to CNY 16,398.6 million in 2015. This study can provide scientific basis for ecological compensation practices and promote high-quality development of the socio-economy of the watershed.