Evaluation of Tea Frost Risk in Zhejiang Province Based on GIS

Tea is one of the most important economic crops in Zhejiang Province, while it suffers the impact of frost disaster in spring. An evaluation of the risk of tea frost disaster would benefit crop management strategies that seek to enhance the sustainability of the tea industry. Based on the principles of natural disaster risk assessment, we have employed hazard, exposure, vulnerability and prevention capability, as indices of frost disaster risk assessment. The frequency of tea frost disaster was calculated based on the daily minimum temperature data of 71 meteorological stations from 1971 to 2017. The 500-m resolution DEM and slope data were used to represent the exposure. The annual tea yield and planting area of each county from 2011 to 2017 represent the vulnerability. The GDP per capita of each county from 2014 to 2017 was utilized as the indicator of prevention capability. Then the assessment model of tea frost risk was built using fuzzy mathematics and the synthetic weighted mark method and the natural disaster formation mechanism. The weight coefficients were determined by expert knowledge of the influence level, reflecting the relative seriousness of the disaster and its defense competence using an analytic hierarchy process (AHP). At last, the zoning map of tea frost disaster hazard and the risk were created by GIS technique. The results showed that the frequency value ranged from 2.5 to 18.9 per year. The region with high altitude and high latitude would meet with tea frost more often, such as the northwest and middle - north of Zhejiang. Meanwhile, the southern area confronted fewer times, namely Wenzhou and plat zone of Lishui city. The index of tea frost risk ranged from 0.01 to 0.70. Spatially, the north of Zhejiang Province is of higher tea frost risk, especially in the Anji and Linan counties located in the northwestern hills. A lower risk is observed in the north plain, though at a notable range. The risk in central mountainous area is the second highest in ranking, mostly in the Xinchang, Pan’ an and Tiantai counties. In the Jinhua and Quzhou basins, the risk index is distinguishably lower compared with surrounding areas. The southwestern hills consisting of Suichang, Wuyi and Taishun counties were mild risk regions. With respect to Wenzhou, the risk index decreased to the minimum value in Zhejiang Province. On the whole, the risk decreases due south, since the temperature was lower with higher latitude. Besides, areas of higher altitude have a larger potential impact of tea frost as the temperature drops lower. But the risk index in areas such as Ningbo and Shaoxing cities in the North was not much high due to their disaster resilience. Owing to the high risk index areas such as Anji, Changxing, Huzhou, Deqing, Lin’ an, Fuyang, Tonglu, Zhuji, Fenghua, Jiashan, Shenzhou, Xinchang, Pan’ an, Taishun and Suichang, it is highly recommended to conduct corresponding measures to prevent and decrease the damage of tea frost disaster. Field investigations would provide more scientific support for optimization of agricultural production.