Evaluating The Potential Productivity And Its Responses To Climate Change In The Loess Plateau Of China

Climate change is the most direct factor which effect on the agricultural development. The climate change of the Loess Plateau has important effect on crop productivity. The characteristics of the climatic potential productivity and its relationship with the actual productivity were analyzed as to provide the agricultural development and planning with scientific basis. To achieve this goal, this study takes the climatic and actual productivity as the object on basis of meteorology and ecology theory.The statistical analysis method and model simulation analysis were used to analysis the distribution and changes characteristics of the main climatic factors（light, temperature, precipitation, etc.） in recent 50 years（1960²011）. The climatic potential productivity, distribution characteristics, sensitivity and its change characteristics were evaluated on basis of the Miami and Thornthwaite Memorial model and analyzed to discuss the space of the actual productivity increasing. Besides, the Changwu tableland regional crop production for case analysis as to discuss the effective means of agricultural productivity of the Loess Plateau. To achieve this goal, these datasets, including meteorological observation data（hourly datasets of the temperature, precipitation and the radiation） and crop growth data（grain yield, there is no irrigation in the whole crops growth period.） were collected over the past 15 years（from 1999 to 2014）. Climate potential productivity of winter wheat and spring maize were calculated through environmental factor correction method.It is of great significance to study the climate limiting factors and improvement approach on the basis of the climatic potential productivity as to reasonable utilization of climate resources, give full play to the climatic potential productivity, to improve the level of productivity and to guid the agricultural production.The main conclusions of this paper are as follows:（1） The main climatic factors（light, temperature, precipitation, etc.） showed different time scales of cyclical, periodic, volatility and obvious spatial heterogeneity characteristics. The annual average temperature of the Loess Plateau is between 7.39 ℃ and 9.93 ℃, its climate change arate is 0.39 ℃/10 a, and the winter warming in the most significant. The annual average precipitation is between 322.26 mm and 663.93 mm, its climate change rate is-9.43mm/10 a, and the autumn precipitation reducing as the most significant. The annual average sunshine hours are between 2334 h and 2853 h, its climate change is 34.93 h/10 a, and the summer sunshine hours reducing as the most significant. The annual average temperature shows a trend on the space distribution as high in the south than in the north, high in the east than in the west and shows a decreasing from sourtheast to northwest. Influenced by altitude and terrain, the temperature rise in most of the Inner Mongolia, the northeast of Ningxia, Wutai Mountain in Shanxi, Northern Shaanxi and the eastern part of Gansu province as the main areas is larger. The annual average precipitation shows a trend as high in the south than in the north, high in the east than in the west on the space distribution. The precipitation is less than 200 mm in the Inner Mongolia hetao area which belongs to arid regions. The annual average precipitation is between 200 mm and 400 mm in the most north region of line of Meander-Yulin-Guyuan-Linxia which belongs to semi-arid areas, the annual average precipitation is between 400 mm and 800 mm in the sourth region of this line which belongs to humid areas. From the distribution of annual average precipitation climate tendency rate, the semi-humid and the humid regions are showed a south domestication as a whole. The annual average sunshine hours shows a trend high in the north than in the south, high in the west than the east, and the west of the Loess Plateau as the main area decreasing in significant.（2） The climatic potential productivity was limited by the change of climate and its sensitivity to future climate change is enhanced, and this will impact on agricultural production planning of the Loess Plateau.The climatic potential productivity of the loess plateau is between 6379 kg·hm^-2·a^-1 and 9143 kg·hm^-2·a^-1. For many years, on average is 7755 kg·hm^-2·a^-1, its climate change rate is 1.4kg·hm^-2·10a^-1, and make mutations near 1992. The climatic potential productivity shows a trend on the space distribution as high in the south than in the north significantly. The precipitation is the most key factor limiting the regional climatic potential productivity, and then the temperature. According to the regression equation, the climatic potential productivity will increase 213.67 kg·hm^-2·a^-1 as the temperature increases（or reduces） 1℃, and will increases（or reduces） 9.03 kg·hm^-2·a^-1 as the precipitation increases（or reduces） 1mm.（3） There was a large difference between the climatic potential productivity. The application of new technologies is an important mean to increase the agricultural production of the Loess Plateau. The results of the evaluate of the potential and actual productivity of typical crops in Changwu Tableland shows that the temperature requirement rates of the winter wheat and the spring maize were 0.37 and 0.39, respectively. In addition, the moisture requirement rates of the winter wheat and the spring maize were 0.43 and 0.68, respectively. Secondly, the realization rates（actual productivity v.s. climate potential productivity） of winter wheat and spring maize were 71% and 80%, respectively. There was still a large difference between the actual productivity and the climatic potential productivity although realization rates of the climate potential productivity were rather high. Therefore, it is important to explore climate potential productivity as to increase actual productivity, for example, the water-saving irrigation and plastic film mulching measures should be promoted in Changwu tableland, especially for the winter wheat production.