北方农牧交错区农业生态系统生产力对气候波动的响应——以准格尔旗为例

气候变化对区域生态系统结构和功能有重大影响。以中国北方农牧交错区的准格尔旗为例,利用气象和《统计年鉴》数据,采用数理统计方法分析准格尔旗1961—2009年降水量、平均气温的波动特征,计算出该地区1961—2009年农业生态系统NPP值和主要农作物的气候产量,论述了准格尔旗农业生态系统生产力对气候波动的响应。结果表明:(1)降水量和平均气温的年际、年内波动均显著。(2)准格尔旗农业生态系统生产力呈现阶段性地波动上升趋势。排除社会、科技等影响,气候生产力对气候波动表现出较强的敏感性,是作物气候生态适应的结果。(3)中国北方雨养旱作区,粮食气候产量受降水量年际波动(特别是7、8月)显著影响;谷子、糜黍、玉米、薯类、大豆和油料等农作物的气候产量与降水量年际波动呈显著正相关;谷子、糜黍的气候产量与生长季降水量年内波动呈显著负相关。集水型生态农业是北方农牧交错区生态环境友好的农业发展模式。(4)谷子、糜黍、薯类、大豆和油料等农作物的气候产量与6、7、8月平均气温年际波动呈显著负相关;生长季平均气温年内波动对谷子、糜黍、大豆和油料等农作物的气候产量有显著负面影响。因此,需要综合采取工程、生物和农业措施,将气候变化对主要农作物气候产量的不利影响降到最低。

The response of agro-ecosystem productivity to climatic fluctuations in the farming-pastoral ecotone of northern China: a case study in Zhunger County

Global climate change affects the structure and function of regional ecosystems. The response of agro-ecosystem productivity to fluctuations in climate continues to be a worthwhile research topic globally. Precipitation and average temperature during the growing season are the most important meteorological indicators affecting crop climatic yield. In the farming-pastoral ecotone of northern China, the effects of precipitation and temperature are very obvious. The objective of this study is to address two questions: (1) How does climatic fluctuation affect climatic impacts on crop yield? (2) Which crops have significant responses to fluctuations in precipitation or average temperature? Zhunger Counties in Inner Mongolia Autonomous Region was selected as a typical region in the farming-pastoral ecotone where the growing season of crops is mainly from May to September. Using long-term observational data collected by the Bureau of Meteorology during 1961-2009 in Dongsheng and Zhunger Counties of Inner Mongolia, and Hequ County of Shanxi Province, we found obvious inter-annual and intra-annual fluctuations in precipitation and average temperature. Net primary productivity (NPP) of agro-ecosystem is a comprehensive indicator reflecting the ability of crops to act as carbon sinks. Statistical Yearbook data, including crop yield and the extent of the area planted during 1961-2009, were used to evaluate NPP of agro-ecosystem using conversion formula. Results showed the rise of NPP had stages of volatility. During the first stage, NPP rose slowly from 1961 to 1981. During the second stage, 1982-1998, NPP rose obviously with the implementation of the household contract responsibility system, promotion of agricultural science and technology, and the application of large amounts of pesticides and fertilizer. The third stage, 1999 to 2009, was varied. During 1999-2001, NPP declined sharply in a period with less precipitation; after 2002, NPP rebounded slowly because some farmland was being converted into forest or grassland. If the effects of human society, science and technology are removed, climatic productivity was very consistent with climatic fluctuations during this time period. Based on crop yield and planting area, we calculated crop yield per unit area. To remove effects of society, science and technology on crop yield, we evaluated crop technological yield (trend yield) using linear or nonlinear models, and calculated crop climatic yield, which obviously reflected changes in crop yield caused by climatic fluctuation. We used SPSS13.0 to quantify the correlation between crop climatic yield and climatic fluctuation. Results showed grain climatic yield was affected by inter-annual fluctuations in precipitation in the semi-arid Loess Plateau of China. These effects were particularly obvious in July and August. Specifically, there was an obvious, positive correlation between crop climatic yield and inter-annual fluctuations in precipitation for millet, broomcorn millet, maize, potatoes, soybeans and oil crops. During the growing season, intra-annual fluctuations of precipitation negatively affected climatic yield of millet and broomcorn millet. So, developing water-harvesting ecological agriculture is very important for efforts to improve the crop response to changing conditions related to water, fertilizer and heat, and for enhancing the stability of agro-ecosystem in the farming-pastoral ecotone of northern China. Similarly, there was an obvious negative correlation between crop climatic yield and inter-annual fluctuations in average temperature for millet, broomcorn millet, potatoes, soybeans and oil crops. During the growing season, the intra-annual fluctuation of average temperature negatively affected climatic yield of millet, broomcorn millet, soybeans and oil crops. Since rainfall and heating occur in the same seasons, and temperatures show an increasing trend in Zhunger County, it is important to select crop varieties with longer growing periods or to take effective protective tillage measures such as using no-till methods with straw cover. In short, the effects of multi-scale climatic fluctuations on productivity were very different for different crops; the effect of monthly-scale changes was the most obvious. In Zhunger County, climatic fluctuations, superimposing natural driving forces and mankind's activities, would obviously affect the sensitive regional ecosystem and aggravate the degradation of land productivity. So, it is very necessary to reduce the adverse effects of climate change on crop yield by taking appropriate engineering, biological and agricultural measures.