农田是以作物种群为主体的生态系统,是人类改造和利用自然资源,生产农产品的主要活动场所。由森林和草原的天然生态结构垦植为农田后,原有天然植物群落与土壤之间自养型的物质循环遭到破坏,其数十年,乃至数百年所积累的有机质,处于被分解、被消耗状态,且这种变化势态随着开 Cropland is an ecological system that is dominated by crop populations and is a major activity site for mankind to transform and utilize natural resources and produce agricultural products. After the natural ecological structure of forests and grasslands are reclaimed as farmland, the autotrophic material circulation between the original natural plant communities and the soil is destroyed. The organic matter accumulated for decades or even hundreds of years is decomposed , Was consumed state, and this change in the trend with the open