Analysis On The Spatio-temporal Change Of Agro-climatic Resources And Its Impact On Major Crops In Eastern Gansu Nearly50Years

Agro-climatic resource is one of the important environmental resources foragricultural production, including the climatic factors such as heat, water and solar energyare closely related to agricultural production, their amount and conditions of spacecombination are vary from place to place, resulting in the regional differences of a widerange of light, heat, water resources in different degrees, and to some extent affected thestructure and layout of the local agricultural production, crop species and varieties andcultivation methods and so on. Therefore, it has a great significance that analysis on thetemporal and spatial variation of regional agro-climatic resources for the developmentstrategy formulation and long-term planning of regional agriculture. The study based ondaily meteorological data from1961to2010and integrated a variety of mathematicalstatistics methods of the climate trend rate, the Standardized Precipitation Index, thePenman-Monteith formula, the spatial interpolation of Inverse Distance Weighted, theelevation correction, the contour function, the empirical orthogonal function (EOF) androtated empirical orthogonal function (REOF), fast clustering analysis, correlation analysisand partial correlation analysis for quantitative study of the temporal and spatial variationof agro-climatic resources of heat, water and light energy in eastern Gansu, and analyzedthe impact of agricultural climate resources changes to the main crop acreage, plantingpattern, cooked zone and growth period in this area. The study drawed the followingconclusions：（1）Heat resource variation: The average annual temperature showed a rising trendoverall in eastern Gansu nearly50years. The temperature of winter and spring increasedsignificantly, which are the largest contribution to the continued warming in the area. Itmainly influenced by terrain that higher values of annual temperature and seasonaltemperature located in the southeast and the middle, and lower values located in thewestern. The first frost date postponed, the last frost date in advance and the frost-freeperiod extended in the vast majority of sites and mainly concentrated in the middle. Theactivity accumulated temperatures and duration days showed a significant upward trend;the negative accumulated temperature significantly increased, but the continuous days gradually reduced, particularly in the central, mainly due to topography and latitude factors.（2）Water resource variation: The average annual precipitation indicated a significantdecline trend in the area nearly50years and the instability of precipitation increased since1990s. Mainly due to the monsoon climate and terrain affect, the region’s precipitation wasdiminishing in southeast-northwest direction. The drought-flood situation of inter-annualand seasonal showed a drought evolution trend, and is divided into three drought-floodregions: the southeast waterlogged area, the mid-west drought-flood suitable area and thenorthern arid area. The average annual reference crop evapotranspiration (ET0) displayed adecreasing trend, and higher values lied in northern and central, but lower values located inwestern. The most sites ET0showed a significant increase trend and intensified drought inspring, but all sites ET0showed a decreasing trend in summer, which is the main cause ofthe decline of the average annual ET0. The change of autumn and winter ET0was notsignificant in various stations. The change trend of monthly ET0of each station wereconsistent single peak and reached the peak between June to July, mainly affected by theincreasing of sunshine hours and solar elevation angle.（3）light resource variation: The average annual sunshine hours overall indicated arising trend in the area nearly50years, the light resource was rich in1970s and was poor in1980s. The growing seasonal sunshine hours showed a fluctuant descending trend that wassignificant since1980s. Due to affected by the influence of slope aspect and altitude, lightresource was abundant in southeast and north, but the west was poor.（4）the impact of major crops: The wheat acreage significantly reduced anddiminishing by the south to the north in eastern Gansu nearly50years, but graduallyincreased in corn acreage and extended northward and westward. The wheat plantingpattern gradually shifted to the balanced planting pattern of three planting structure types.The wheat growing region westward moved and northward retreated; the other grain cropsplanted area eastward extended; the main growing region of wheat and other grain cropsgradually southward expanded. The cropping system area of triple cropping in two yearssignificantly moved northward and the multiple cropping index improved in the study area,but one cropping area reduced, especially since the21C. The growth and development ofmain crops were affected jointly by temperature, precipitation and light nearly30years. The sowing time of winter wheat postponed2~3d/10a and the regreening period advanced4d/10a, which caused overwintering stage and vegetative growth period of winter wheat areshortened. The flowering period advanced4~5d/10a, the maturity time advanced5~6d/10aand the whole growth period shortened to8~9d/10a, while the length of the reproductivestage was little change. In the past30years, the sowing time of corn ahead of2d, theseedling emergence stage ahead of3d, the jointing stage ahead of8d, the booting stageadvanced4d, the tasseling stage ahead of9d, the flowering period advanced8d, the silkingperiod ahead of7d and the maturity time advanced9d, while the vegetative stage shortened2~3d, the reproductive stage shortened4~5d and the whole growth period shortened6~7d.