The Laoshan forest is the largest forest in Nanjing, and it plays an important role in water resource management in Nanjing. The objectives of this study are to determine if the temperature vegetation dryness index (TVDI) is suitable to estimate the soil moisture and if soil moisture is significantly affected by tree species in the Laoshan forest. This paper calculated the spatial distribution of TVDI using LANDSAT-5 TM data. Sixty-two observation points of in situ soil moisture measurements were selected to validate the effectiveness of the TVDI as an index for assessing soil moisture in the Laoshan forest. With the aid of the three different temporal patterns, which are 10 January 2011, 18 May 2011 and 23 September 2011, this paper used the TVDI to investigate the differences of soil moisture under four kinds of mono-species forests and two kinds of mixed forests. The results showed that there is a strong and significant negative correlation between the TVDI and the in situ measured soil moisture (R² = 0.15–0.8, SE = 0.015–0.041 cm³/cm³). This means that the TVDI can reflect the soil moisture status under different tree species in the Laoshan forest. The soil moisture under these six types of land cover from low to high is listed in the following order: Eucommia ulmoides, Quercus acutissima, broadleaf mixed forest, Cunninghamia lanceolata, coniferous and broadleaf mixed forest and Pinus massoniana.

With the intensification of human activities, the vulnerability of water, energy, food and ecology systems has become more and more prominent, and the research on the vulnerability of the water-energy-food-ecology (WEFE) nexus is significant to realizing regional sustainable development. This study aims to make a comprehensive measurement of the vulnerability of the WEFE nexus in the Yangtze River Economic Belt (YREB) from 2008 to 2019, clarify the evolutionary trend of its vulnerability, and predict the vulnerability of each province (municipality) in the future, to formulate policies to reduce vulnerability. This study firstly constructs a vulnerability evaluation index system of the WEFE nexus based on the VSD framework and uses the neighborhood rough set (NRS) to reduce the attributes. Then, the TOPSIS model is used to evaluate the vulnerability of the WEFE nexus. Finally, by comparing the training accuracy of the random forest, decision tree and support vector machine (SVM) model, the SVM model is selected to predict the vulnerability of the WEFE nexus under different scenarios in 2025. The results show that the vulnerability of the WEFE nexus in the YREB showed a fluctuating downward trend from 2008 to 2019. The decline is faster in the middle and upper reaches, and slower in the lower reaches. In 2025, under a strong resource management scenario, the vulnerability of the provinces (municipalities) in the YREB will decrease significantly, while the weak and moderate resource management scenarios are not conducive to reducing vulnerability and even worsening. Therefore, in the future, the provinces (municipalities) in the upper, middle and lower reaches should make reasonable use of the resource endowments, take measurements actively according to local conditions, and continuously strengthen the management of water, energy, food and ecological resources, thus promoting the continuous improvement of the vulnerability of the WEFE nexus.

The vulnerability of the water-energy-food-ecology nexus in the Yangtze River Economic Belt greatly impacts regional sustainable development. This study aimed to conduct a quantitative assessment and temporal and spatial evolution analysis of the vulnerability of the water-energy-foodecology nexus in the Yangtze River Economic Belt from 2008 to 2018 and diagnose the main factors that hinder the vulnerability reduction. Firstly, the vulnerability assessment index system was constructed according to the Vulnerability-Scoping-Diagram framework. Then, SPA-TOPSIS and ArcGIS10.7 were comprehensively used to evaluate the vulnerability of the water-energy-food-ecology nexus. Finally, the obstacle degree model was used to diagnose the main factors that hinder the vulnerability reduction of the water-energy-food-ecology nexus from the index and subsystem levels. The results showed that the vulnerability level of the water-energy-food-ecology nexus in the Yangtze River Economic Belt decreased from 2008 to 2018, and the overall trend was improved. The vulnerability level of the upstream region was generally lower than that of the middle and lower reaches. The main obstacles are the comprehensive utilization rate of solid waste, the primary industry energy consumption ratio, energy consumption intensity, water consumption per 10,000-yuan GDP, domestic water consumption per capita and fertilizer application per unit grain sowing area. The energy subsystem is the primary obstacle system, followed by the food, ecology, and water subsystem.

Under the background of the low-carbon economy, considering that manufacturers produce common products and low-carbon products simultaneously and the two products are substituting, three models are set up, namely, no government subsidy, subsidy based on the research and development (R&D) cost, and subsidy based on the production volume of low-carbon products. The Stackelberg game theory is used to analyze the optimal decision of the supply chain under the three methods of government subsidy, the influence of the correlation coefficient on optimal decision-making is discussed, and the effects of different government subsidy methods on the equilibrium solutions are compared and analyzed. Finally, the results are verified and illustrated by example analysis. The study found that the government subsidy reduces the sales volume of common products but increases the sales volume of low-carbon products, the emission reduction of unit low-carbon products, total emission reductions, and manufacturer’s profit. The unit emission reduction and total emission reductions are the highest when the government subsidies are according to the R&D cost, and the manufacturer’s profit is the highest when the government subsidies are according to the production volume of low-carbon products. Total emission reduction and supply members’ profit have a positive relationship with the subsidy coefficient and the sensitivity of consumers toward price difference and have a negative relationship with the R&D cost coefficient.