Risk Evaluation Technology Research Of Spring Frost Injury In Southern Yangtze Tea Areas

Camelia sinensis, Genera Theaceae, tea genera, is the characteristic economic crops of china, with good economic and ecological benefits. Because of suitable rainfall, ample sunshine and abundant heat resource, Southern tea area has been becoming a major production base of green tea in our country. It is counted that, in recent 5 years, tea garden average planting areas, production and value has been respectively 720.27 million hectares,588,800 tons and 29.27 billion yuan in Southern Yangtze tea areas. However, in recent years, with global climate change, the main agro-meteorological disasters of tea garden, such as disaster of drought and high temperature, spring frost injury and frost damage of winter, were gradually increasing, which has brought a huge risk for the safe and stable production of green tea in southern tea areas. In recent years, with the adjustment of tea industrial structure, due to time to market early and high prices, the famous tea of spring has become the main way to farmers’ income in Southern Yangtze tea areas. However, low temperature frost of spring was often the main factor for limiting spring tea yield levels and quality of good or bad, at the same time, it was also an important factor for restricting tea planting range in the southern areas. Therefore, in this paper, a control experiments of spring frost was conducted by using artificial climate chamber, analyzing influence of spring frost for the physiological characteristics of tea and further found critical meteorological indicators for spring frost disaster. On this basis, temporal and spatial distribution characteristic, risk assessment and climate suitability were also analyzed。 The results provided important theoretical basis for spring tea meteorological disaster prevention and optimizing tea planting layout in Southern Yangtze tea areas. The main conclusions of this study were as follows:(1) The results showed that different low temperature frost process on tea leaf chlorophyll content, photosynthetic parameters, fluorescence parameters, protective enzyme activity, soluble protein content and relative conductivity were inequality. With the extension of low processing time, chlorophyll a, chlorophyll b, carotenoid content of tea leaves under different treatments gradually decreased. The light saturation point, the maximum net photosynthetic rate, apparent quantum efficiency, maximum carboxylation efficiency, potential photochemical efficiency, photochemical quenching, electron transfer efficiency of tea leaves decreased significantly under low temperature stress, and light compensation point, stomatal limitation, soluble protein content, MDA significantly increased. The activity of superoxide dismutase(SOD), peroxidase(POD) and catalase(CAT) showed a trend first and then decreased under different low temperatures treatment; it showed some cold tolerance and frost resistance. Hypothermia can alter cell membrane permeability of tea shoots and then lead to a large number of electrolyte extravasation. The study also indicated that with the low temperature stress enhancing and the days increasing, the protective enzyme activity decreased, the membrane lipid peroxidation increased gradually, the chlorophyll synthesis was inhibited. In this paper, based on the changes of cell injury rates resulting in the disaster of tea buds, the spring frost damage of tea tree was divided into mild, moderate, and severe three different levels in Southern Yangtze tea areas.(2) Using daily meteorological data from 1959 to 2012 were observed by evenly distributed 85 meteorological stations in Southern Yangtze tea areas and combined with critical meteorological indicators resulting in the spring frost damage of tea tree, and then number of occurrences over the years at different levels spring frost injury were counted. Temporal and spatial distribution and multi-time scale variation at different levels spring frost injury in Southern Yangtze tea areas were analyzed by using wavelet analysis, empirical orthogonal decomposition, Mann-Kendall, R/S and other methods. Studies suggested that, on the whole, different levels spring frost injury in Southern Yangtze tea areas existed obvious multi-scale characteristic features, possessed significant mutations regularity,and it will be still partial disasters in the next few years.(3) In this paper, risk assessment at different levels spring frost injury in Southern Yangtze tea areas were conducted by using information diffusion theory and then risk profile and spatial distribution for first four levels of risk under low-temperature damage was carried out by comprehensive comparative analysis,at the same time, the effects of altitude on total spring frost was analyzed. Studies suggested that tea tree for risk pressure of spring frost damage are larger in Southern Yangtze tea areas, the southern region was mild, moderate frost less prone areas. In addition to the northwest of Hubei, the southeastern Hunan and some regions of south Jiangxi, most of the region were still a severe frost prone areas. With increasing levels of risk, on the whole, risk probability values for different levels of spring frost showed a downward trend. Studies have shown that tea tree occurring frost damage influenced greatly by altitude, basically showing higher altitudes, the shorter the period of risk, the higher the rate of reproduction.(4) In this paper, based on the 1959-2012 daily weather from 85 meteorological stations data in southern tea areas, and by using fuzzy mathematics theory and spatial interpolation methods, temperature, precipitation, sunshine and climate suitability in Southern Yangtze tea areas were studied during growing of spring tea. Studies suggested that, during growing of spring tea, the optimum areas of precipitation, temperature and sunshine suitability in Southern Yangtze tea areas were concentrated in the central, northern, southern region. During whole growing of spring tea, precipitation and temperatures suitability were higher, however, sunshine Suitability was less and was the key climate factors affecting the growth of spring tea in Southern Yangtze tea areas. Analyzing the inter-annual variability of each meteorological factors indicated that global climate change was conducive to the growth of the spring tea in Southern Yangtze tea areas.