中国农田生产力变化的空间格局及地形控制作用

中国政府高度重视粮食安全,采取一系列措施提高粮食生产并取得了一定的成效,但是20世纪90年代全球农业生产徘徊不前并不仅是一种由特定政策或市场因素导致的短期现象.因此,认识在长时间尺度上农田生产力变化的特征及其控制因素对保障国家粮食安全、制定农业政策及调节生态系统服务功能具有重要意义,研究稳定少动但对农田生产力形成有重要影响的地形因子对农田生产力变化的作用是其中的一项重要内容.生态系统生产力遥感机理模型能够清晰地表达国家尺度农田生产力的时空格局,应用1981～2000年的NOAA/AVHRR卫星遥感数据驱动GLO-PEM模型,以10年为时间尺度分析20世纪80年代到90年代农田生产力变化的空间格局特征.研究结果表明,在10年的时间尺度上,地形特征控制着农田生产力变化空间格局分异规律,农田生产力降低的几率随地形起伏度增大而增加,山区耕地发生生产力下降的可能性比平原耕地高10%～30%.在研究时期内尽管中国农田生产力总量增加,但仍有24%的农田发生农田生产力下降,其中71%在丘陵山地,尤其是地形起伏破碎的黄土高原及云贵高原地区.

Spatial Pattern and Topogr aphic Control of China's Agricultural Productivity Variability

Being home to one of every five people in the world, China always put the food security issue high on its agenda and has successfully provided adequate food for its people. However, the stagnation of global agricultural production during the 1990s is not a short-term phenomenon caused by policies or market. Therefore, it is significant for food security, agricultural policy making and ecosystem service functions adjustment to recognize the variability of agricultural productivity and its predominant controlling factors at decadal temporal scale. The effect of topography on agricultural productivity variation has been poorly understood due to the lack of spatially explicit agricultural productivity information. In this study, the agricultural productivity variation and its spatial heterogeneity between the 1980s and 1990s are analyzed using a satellite-based production efficiency model (GLO-PEM) driven with NOAA/AVHRR data. It is shown that spatial heterogeneity of agricultural productivity variability was predominantly controlled by the topographic conditions at decadal scale. The proportion of cropland area occurring in agricultural productivity reduction increased with the amplifying relief, and consequently, the probability of cropland in hilly areas suffering from agricultural productivity reduction was 10%-30% higher than cropland in plain areas. Although the total agricultural production had increased in each agricultural region of China during 1981-2000, there were parts of cropland area suffering from reduction of agricultural productivity, accounting for 24% of the total cropland area. In those croplands with decreased agricultural productivity, 71% were located at hilly areas, particularly on the Loess Plateau and Yunnan-Guizhou Plateau areas.