亚热带丛枝菌根与外生菌根森林对土壤氮循环的影响

菌根真菌能促进植物获取氮素从而调节土壤氮循环过程,但不同类型菌根影响土壤氮循环的特征尚待更多研究.本试验选择中国亚热带典型次生林植被,设置丛枝菌根(AM)和外生菌根(ECM)树种优势样地,对比分析两种菌根类型森林土壤氮状态的差异,以探究菌根类型影响土壤氮循环的可能作用机制.结果 表明,AM与ECM森林的土壤总氮和铵态氮...

Comparison of soil nitrogen cycling between arbuscular mycorrhizal and ectomycorrhizal forests in a subtropical region

Mycorrhizae can enhance plant nitrogen(N)acquisition and affect soil N cycling.Because tree species differ in mycorrhizae types they associated with,stand-scale soil N cycling could be influenced by tree species com-position via their association with different types of mycorrhizae.We investigated the effects of arbuscular mycorrhi-zal(AM)and ectomycorrhizal(ECM)forests on soil N cycling in subtropical forests.Total soil N and ammonium(NH₄⁺-N)contents did not differ between AM and ECM forests,whereas dissolved organic N(DON)and nitrate(NO₃^--N)were significantly higher in AM than in ECM forests(P<0.001).In particular,soil NO₃^--N was more than twice as high in AM as in ECM forests in both the organic horizon and mineral horizon.Soil NO₃^-∶NH₄⁺ratio was greater than 1 in AM forest soil but less than 1 in ECM forest soil,indicating that plant-available N was abun-dant in AM forest soil.Soil net nitrification was 2.2 times higher in the AM forest than in the ECM forest and posi-tively correlated with soil NO₃^--N content.The relatively fast soil N cycling in AM forests was attributed to the high-er aboveground litter quality,soil pH,and water contents.We found that more nitrate was leached in AM forests than ECM stands,suggesting that the“mycorrhizal-associated nutrient economy”framework can also apply to sub-tropical forests.These results will improve our prediction of soil N cycling,aid the development of soil N cycling models under global change,and facilitate forest restoration in this subtropical region.