Environmental variances in temperature, moisture, and soil fertility caused by elevation gradients affect tree growth. However, the variability in regional climate and differences in tree physiology give rise to much uncertainty regarding the effects of elevation on tree growth patterns and resource allocation. In order to clarify the growth-limiting factors and physiological mechanisms of trees at different elevations, we selected Picea crassifolia (Qinghai spruce) at high (3300 m), middle (2850 m) and low (2585 m) elevations to analyze the interannual trends of tree radial growth and the resource allocation trade-offs involving nonstructural carbohydrates (NSC). The results were as follows: 1) the limiting factor for the growth of Qinghai spruce changed from growth limitation to carbon limitation with an increase in elevation; this was supported by the higher concentrations of NSC and its components in the whole plant and all tissues at middle and low elevations compared to high elevation, while the basal area increment (BAI) showed a decreasing trend at middle and low elevations and an increasing trend at high elevation. 2) The greatest concentrations of NSC were found in the leaves and thick roots at all three elevations, but soluble sugar (SS) and starch (ST) mainly accumulated in overground tissues (leaves and trunks) and underground tissues (fine and thick roots), respectively. 3) The ratios of soluble sugar to starch (SS/ST) at high elevations were significantly greater than those at middle and low elevations, indicating that more carbon was used for growth at high elevations, while more carbon was used for long-term energy storage at middle and low elevations. The results elucidate the growth constraints of Qinghai spruce at different elevations and the resource allocation trade-off mechanism, and offer reference points for ecological adaptation theory and conservation measures for trees at different elevations.

A scientific measurement of the amount of tradable water rights forms the premise for reaching an agreement in water rights trading. However, the existing measurement methods, based on water saving potential, still have problems caused by large computation workload and difficult-to-control errors. Conflicts also easily emerge between transferor and transferee during the execution of transaction agreements. This paper proposes a new method for measuring tradable water rights from the perspective of an assessment of the risk of water shortage for the transferor. The following describes the basic idea: An index system is established for the assessment of the water shortage risk of the transferor to identify water shortage risk categories. The impact of the water rights transaction volume on the transferor’s water shortage risk category is analyzed under different incoming water frequencies. The transferor’s water shortage risk threshold is set and a simulated annealing algorithm is designed to calculate the theoretical value of tradable water rights. The following summarizes the innovation of the proposed method: The water resource shortage risk evaluation index of the transferor is constructed based on water resource endowment, water supply, water demand, and water ecological environment of the transferor; then, a risk classification evaluation model of water resource shortage is established and a measurement method of tradable water rights is introduced. Comprehensive analysis of a case analysis of Helan County in the Ningxia Autonomous Region, China, shows that the recommended value of tradable water rights of Helan County is 40 million m³. Various methods are used to calculate the weights of evaluation indexes, which are compared to the measured results of tradable water rights; moreover, the sensitivity of the results is analyzed. The obtained results show that the use of water-saving potential to measure the amount of tradable water rights is feasible.

To alleviate the contradiction between the increasing demand for water and the shortage of resources and to provide a favorable institutional environment for water rights trading, the Chinese government has strengthened the top-level design of water management system. However, the water-rich regions (southern regions of China) have good water resource endowment and a surplus of total water consumption indicators. Does this mean that there is no incentive and no need to conduct water rights trading in these regions? Through the investigation of water rights circulation cases in the Taihu Basin, a typical water-rich region of China, we established the existence of trading demand and some difficulties in conducting transactions. This paper argues that the needs of trading include alleviating the water gap in regional development, solving the water demand for large new projects, coordinating trans-jurisdiction water disputes. The plight of trading includes the lack of awareness, irregular process, excessive administrative intervention, and imperfect trading system.