Study on the regionalization of optimum areas for‘Dongzao’growing in Shaanxi province

Abstract:【Objective】The study aims at clarifying the geographical distribution characteristics of the high-quality‘Dongzao’growing zones in Shaanxi province.【Methods】Based on the daily data with 98 national meteorological stations in the whole province from 1981 to 2018, the biological characteristics of‘Dongzao’were combined with eight key comprehensive climatic factors including negative accu- mulated temperature, annual maximum temperature, frost-free period, average temperature from March to May, sunshine hours from June to August, precipitation in September, sunshine hours in September, accumulated temperature during the whole growth period, which may influence the growth and develop- ment of‘Dongzao’in the whole province, so that they served as the optimum zoning index. The mem- bership function of each region index was established by fuzzy mathematics method and the weight was determined by analytic hierarchy process. In addition, three-dimensional quadratic trend surface method was used to set up the index model for each region (northern Shaanxi, southern Shaanxi and central Shaanxi) and GIS method was used to draw the single-factor sub-grid layer of the whole province’s‘Dongzao’zoning index. Finally, the whole province was divided into four zones including optimum zone, suitable zone sub- suitable zone and unsuitable zone. The optimum climatic zoning map for  ‘Dongzao’was obtained by fuzzy comprehensive evaluation.【Results】The optimum zone and e suit- able zone were distributed along the Yellow River in Northern Shaanxi and the middle and eastern parts of Guanzhong area. The annual average temperature in the optimum zone for‘Dongzao’growing was 10-14 °C, the average temperature from the blooming to the young fruit set stage was 12-15 °C, the frost-free period was 200-220 d and the annual precipitation was 400-600 mm. It was the optimum zone that developed‘Dongzao’industry in Shaanxi province with the aid of well matched water and heat re- sources, the gentle terrain, fertile soil and good site conditions. Secondly, some parts in the eastern part of the county along the Yellow River in northern Shaanxi and some parts in southern Shaanxi, the Yel- low River coastal areas and the low hill areas with an elevation less than 800 m were also the optimum zone for‘Dongzao’growing. The suitable zone for‘Dongzao’growing was mainly distributed in the shallow mountain belt with an elevation less than 900 m along the Yellow River counties including west part of Fugu county, Shenmu county, Yulin city, Jiaxian county, Mizhi county, Wubao county, Suide county, Zizhou county, Qingjian county, Yanchuan county, Yanchang county, Hengshan county, etc. in northern Shaanxi. In these areas, the average temperature was 9-10 °C, the average temperature from bud break to blooming was 11-13 °C, the frost-free period was 170-190 d, and the annual precipitation was between 400-440 mm, the fertile soil and the well matched climate resources were very suitable for‘Dongzao’growing. The unsuitable areas for‘Dongzao’growing were mainly distributed in the western part of northern Shaanxi, the higher elevation areas along the Qinling Mountains as well as the mountainous areas, and the woodland and gully areas. In these areas, the terrain was complex, the alti- tude was high and the slope was abrupt, which was not suitable for‘Dongzao’growing【. Conclusion】The optimum and suitable areas for‘Dongzao’growing in Shaanxi province were mainly located in the low-altitude areas like Weinan city, Yanliang district，Lintong district, the north of Chang’an dis- trict, Huxian county, Sanyuan county, Jingyang county, Lantian county, the north of Zhouzhi county, Fugu county, Shenmu county, Jiaxian county, Mizhi county, Suide county, Wubao county and Qingjian county, the optimum zones had flat terrain, fertile soil and obvious advantages in climate resource allo- cation, which was suitable for large-scale planting. It was suggested to give priority to the development of‘Dongzao’growing industry in these areas. In addition, the main meteorological disasters that affect- ed the growth of‘Dongzao’in this area included the continuous overcast rains and autumn shower during the fruit ripening period, which should give more concern. From the meteorological point of view, combed with the altitude, the climatic optimum zone for‘Dongzao’growing was obtained and it was also a prerequisite for trees to live and grow into forests with high quality and stable yield. Due to the lack of the introduction and cultivation efficacy by soil fertility factors and land usage status, the physio- logical and biochemical indexes of trees as well as soil and social factors should be combined to further enrich the results of the climatic optimum zones for‘Dongzao’growing, so as to make it more valu- able for guiding introduction and cultivation in the future.