Assessing the temperature risk to longan in South China based on ecological suitability theory

Being an important subtropical fruit, longan temperature risk is very sensitive to climate change. Based on previous researches, selecting observed daily temperature data from 60 stations of South China from 1960 to 2005, the article established the longan temperature suitability model and the temperature risk dynamic assessment model to calculate the temperature suitability and risk of longan, to evaluate the temporal and spatial differences and also to predict the temperature suitability and risk of longan. Firstly, the article analyzes the temperature suitability of longan at different growth stages, and the result shows that temperature changes has a great impact on the temperature suitability of dormancy stage, physiologic differentiation of flower bud stage and morphologic differentiation of flower bud stage. All these have low suitability and high variability, while the other three stages have high suitability and low variability. In addition, the inter-annual change of temperature suitability at different growth stages is analyzed, and the result shows all the growth stages except for fruit growth and maturity stage and treetop growth stage have a decreasing trend in the future. This is caused by the temperature differences between growth stages. Further study indicates that it is hot damage in winter and spring rather than cold damage that plays an important role in longan production in South China. Secondly, based on probability distributions of the longan temperature suitability degree of different reduction rates of yield, the article divided South China into three regions: the low risk region, the medium risk region and the high risk. At the same time, a comparative analysis was done on the longan temperature risk among different periods in South China. The result shows that there is difference in the changing trend of longan temperature risk: in the aspect of spatial distribution, the temperature risk degree decreases with increasing latitude in South - - China; in the aspect of temporal distribution, the temperature risk of longan has a gradual increasing trend with the elapse of time. Finally, the responses of longan growth stages to climate warming in South China were analyzed.