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The purpose of this study is to clarify the fine distribution of climatic suitable area for apple planting in the northern extension area of Shaanxi province in the new climate period (1991−2020), and reveal the development potential of apple planting in this region. Based on the meteorological observation data, the digital elevation model data and the arable land confirmation data，the requirements for the climatic suitability and mountainous site conditions of apple planting in the northern expansion area of Shaanxi province were comprehensively analyzed. Seven factors, including annual average temperature, annual precipitation, average relative humidity from June to August, average minimum temperature from June to August, average temperature in January, aspect and slope, were selected as zoning indexes to divide the climatic suitability of apple planting in the research area. The multiple regression method was used to simulate and calculate the spatialization of every climatic factor. Then the suitability quantitative evaluation model of each single factor was constructed by fuzzy set linear membership function method. The climatic suitability regionalization of apple planting in the northern extension area of Shaanxi was developed by weighted comprehensive evaluation and set optimization methods. Finally, the distribution of dry land and irrigation area in the suitable planting area for apple of each district was extracted by using the arable land confirmation data. The results showed：(1) the northern boundary of the suitable area for apple planting in Shaanxi was from Wuqi county, the middle and south of Jingbian county to the northeast through the south of Hengshan county, Mizhi county to the middle and southern of Jiaxian county, whose terrain were mainly hilly and gully area along the sunny gentle slope, with a general altitude of 730-1660m. (2) The field investigation showed that the zoning result was about 80% consistent with the field planting distribution of apple orchard. (3) The refined spatial distribution of climatic appropriate areas for apple by county (district) based on the arable land confirmation data showed that the area of climatic suitable level above for apple could be developed in the northern expansion zone was about 276.9kha, accounting for 24.6% of the available arable land, among which the dry land area accounted for 96.3%, with rain-fed agriculture as mainstay. Compared with the statistical data of apple planting status in each county (district), it could be seen that there was still 4.9−28.5kha development space in most counties (districts) except Shenmu county and Fugu county in Yulin city, and Wuqi county in Yan’an city. The potential planting area of climatic suitable for apple in Zhidan county in Yan’an city had tended to be saturated. The results can provide reference for optimizing regional layout of apple industry under the background of climate change. [ABSTRACT FROM AUTHOR]

Winter injury is one of the main meteorological disasters that affect apple’s growing distribution and quality. Existing research mainly studies the injuries caused by extremely low temperatures during deep dormancy of apples, mostly using the mean temperature of the coldest month, the frequency of extreme minimum temperatures as indicators to assess the risk and divide the boundaries of apple’s distribution. However, cold resistance of fruit trees is different during different dormant phases, and is closely related with the cold- resistance exercises in fall. The probabilistic forecasting models of early winter injury and extreme winter cold injury are established with the binary Logistic regression, on basis of the data of 2 084 meteorological stations and the winter injuries happened during 1981- 2010. The space is divided into five risk’s degrees as very low, low, moderate, high and very high. The classification standard of the probability of winter injury was referred from the classification criteria in the IPCC report. The results show that: the probabilistic forecasting models of early winter injury and extreme winter cold injury passed the Hosmer-Losmer test, and the prediction accuracies of independent samples reached 83.6% and 91.4% respectively. Early winter injury depends mainly on time of the first frost day and the time interval between the first frost day and the first day that the lowest temperature is lower than - 15 ℃ . The extreme winter cold injury is affected by the average temperature of the coldest month and the cold accumulated temperature when the daily minimum temperature is lower than - 20 ℃ . The freezing injury caused by short- term extreme low temperature is of small occurrence probability and limited influence scope. The extreme low-temperature injury in winter is mainly caused by continuous intimidation of strong and low temperature. Early winter injury is the main freezing injury in apple-producing regions of China, which happens in most apple-producing regions except the ancient Yellow River region and Yunnan producing region. But extreme winter cold injuries mainly happen in high latitude or high altitude regions, including the northern Bohai Gulf, the northwest of the Loess Plateau and Northern Xinjiang. High risk areas of early winter injury and extreme winter cold injury are almost equal. Gansu is the province that has the largest area of risks with moderate degree and above, followed by Liaoning, Hebei and Shanxi. On the other hand, there are low risks of winter injury, especially for extreme winter cold injury, in Shaanxi and Shandong where there are the largest planting areas of apple. [ABSTRACT FROM AUTHOR]

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