关键词: 森林演替, 人为影响, 气候变化

Abstract: Experimental results show that:with a trace content of 10ppm N,the plant biomass isincreased by 30%,and nitrogenase activity by 30—100%.There is no nodule formed with50ppm N application.With 500ppm P and K and 10ppm trace element fertilizers,noduleformation can be promoted and plant biomass increased.The optimum range of pH for thegrowth of symbiotic system is from 6 to 7.When it is close to 8,plant biomass and nitro-genase activity are reduced.Illumination intensity and seasonal variation also affect theactivity of nitrogenase,which is high from July to September and is inhibited in October.

Key words: Forest succession, Human activity, Climate change