Effects of long-term fertilization on r-K strategy microbial populations in farmland mollisol
长期施肥对农田黑土r-K策略菌群的影响

The microbial communities in agricultural soils are responsible for nutrient cycling,and thus,are the important indicators of soil fertility.In this paper,the effects of long-term fertilization on the r-K strategy populations and eco-physiological functional groups of bacteria and fungi in farmland Mollisol were investigated,and the results showed that fertilization decreased the evenness and richness of the fungal and bacterial populations,and the decrements of the bacterial and fungal eco-physiological(EP)indices were 0.019-0.106 and 0.023-0.185,respectively.The amounts of K strategy microbial populations in all treatments were higher than those of r strategy ones.Fertilization caused the increase of r strategy bacteria but the decrease of r strategy fungi.Compared with the control,applying medium amount of manure had the greatest increase of r-K strategy bacteria and K strategy fungi.The amounts of r-K strategy bacteria and K strategy fungi were higher under the combined application of chemical fertilizers and manure than under the application of chemical fertilizers.Under the conditions of K-strategists being predominant,the application of chemical fertilizers enhanced the r-strategy microbial proportion,while the combined application of chemical fertilizer and manure enhanced the ratio of K-strategists.Correlation analysis showed that K-strategy microbial populations had a significant positive correlation(P<0.01)with soil nitrogen content,suggesting that K-strategists might be the key microbial populations in soil nitrogen cycling.