Abstract:  Water overabundance or shortage both affect apple growth and fruit quality. Precipitation is the main water source in apple production in Northern China. Thus, analysis on the spatial and temporal variations in precipitation in main apple producing provinces of Northern China under the setting of climate change is of great significance to guide the rational layout of apple industry. Based on the daily precipitation data measured at 210 meteorological stations from 1970 to 2017 and the digital elevation model of 1km resolution in seven major apple producing provinces (Liaoning, Hebei, Shandong, Shanxi, Henan, Shaanxi and Gansu) and their surrounding areas within 100 kilometers in China, the professional meteorological interpolation software ANUSPLIN, which is based on spline interpolation method, was used to interpolate precipitation data. Then, the refined meteorological grid data of 0.02°×0.02°resolution were obtained. Combined with the geographic information system software ArcGIS and related mathematical statistics methods (e.g., the variation coefficient and climate tendency rate), the calculation and spatial expression of various statistics were carried out on the basis of grid data to analyze the spatial-temporal distribution characteristics of precipitation in major apple producing provinces. The suitable precipitation in the key growth periods of apple were explored according to the annual precipitation range (500.0-800.0mm) which is suitable for apple cultivation and to the distribution of precipitation in the main apple producing areas. The results showed that both the average annual precipitation in the main apple producing provinces and the average precipitation in the key growth periods had the same spatial distribution, i.e. high in the south and low in the north, and high in the east and low in the west. The annual precipitation in about 51.7% of the interest area was between 500.0-800.0mm, and the precipitation in the main apple producing areas was basically 500.0-800.0mm. There were about 55.2%, 51.2% and 40.9% of the study area in the wet year, the normal year and the dry year respectively, where the annual precipitation was between 500.0-800.0mm. The contribution rates of the average precipitation in germination and young fruit period, fruit expanding period and coloring and maturity period to the annual average precipitation were 0.114-0.385, 0.428-0.712 and 0.000-0.270, respectively. The precipitation in fruit expanding period is more than that in other two periods. And the contribution rate of precipitation in coloring and maturity period was higher than that in germination and young fruit period in most areas. The distribution of precipitation time was consistent with apple water requirement. But the variation coefficient of precipitation was generally above 0.15. In terms of climate tendency rate, the precipitation variation trends were not obvious in most regions, except for the coloring and maturity period where 6.3% and 7.9% of the study region showed a significant increase (P<0.05) and a significant decrease (P<0.05), less than 1.0% of the study region passed the 0.05 level significance test in other growth periods. Combined with the temporal and spatial distribution of precipitation in each growth period in main apple producing area and annual precipitation values that was suitable for apple cultivation, it was preliminarily determined that the suitable precipitation ranges of apple in the germination and young fruit period, fruit expanding period and coloring and maturity period of apple were 66.2-170.2mm, 238.4-527.9mm and 69.0-200.8mm, respectively. There were some differences in the precipitation range of main apple producing areas in each province, but they were basically within the above-mentioned precipitation range.

Key words:  Apple, Precipitation, Suitable precipitation, Fruit expanding period, ANUSPLIN