Nitrogen fertilization has minimal influence on rhizosphere effects of smooth crabgrass (Digitaria ischaemum) and bermudagrass (Cynodon dactylon)  

作　　者：Biao Zhu Kevin Panke-Buisse Jenny Kao-Kniffin 

机构地区：[1]Earth Sciences Division,Lawrence Berkeley National Laboratory,Cyclotron Road,Berkeley,CA 94720,USA [2]School of Integrative Plant Science,Cornell University,134 Plant Sciences Building,Ithaca,NY 14853,USA

出　　处：《Journal of Plant Ecology》2015年第4期390-400,共11页植物生态学报（英文版）

基　　金：United States Department of Agriculture National Institute of Food and Agriculture Hatch program(NYC-145403);the New York State Turfgrass Association and the US Department of Energy,Office of Science,Office of Biological and Environmental Research Terrestrial Ecosystem Science Program(DE-AC02-05CH11231).

摘　　要：Aims Plants generally respond to nitrogen(N)fertilization with increased growth,but N addition can also suppress rhizosphere effects,which consequently alters soil processes.We quantified the influence of N addition on rhizosphere effects of two C4 grasses:smooth crabgrass(Digitaria ischaemum)and bermudagrass(Cynodon dactylon).Methods Plants were grown in nutrient-poor soil for 80 days with either 20 or 120μg NH4No3-N g dry soil−1.N mineralization rates,microbial biomass,extracellular enzyme activities and bacterial community structure were measured on both rhizosphere and bulk(unplanted)soils after plant harvest.Important Findings Fertilization showed nominal differences in net N mineralization,extracellular enzyme activity and microbial biomass between the rhizosphere and bulk soils,indicating minimal influence of N on rhizosphere effects.Instead,the presence of plant roots showed the strongest impact(up to 80%)on rates of net N mineralization and activities of three soil enzymes indicative of N release from organic matter.Principal component analysis of terminal restriction fragment length polymorphism(t-rFlP)also reflected these trends by highlighting the importance of plant roots in structuring the soil bacterial community,followed by plant species and N fertilization(to a minor extent).overall,the results indicate minor contributions of short-term N fertilization to changes in the magnitude of rhizos-phere effects for both grass species.

关 键 词：rhizosphere effect N fertilization belowground carbon allocation microbial biomass extracellular enzyme net N mineralization microbial community composition 

分 类 号：S15[农业科学—土壤学]