期刊
JOURNAL OF PLANT ECOLOGY
卷 8, 期 4, 页码 390-400出版社
OXFORD UNIV PRESS
DOI: 10.1093/jpe/rtu034
关键词
rhizosphere effect; N fertilization; belowground carbon allocation; microbial biomass; extracellular enzyme; net N mineralization; microbial community composition
资金
- United States Department of Agriculture National Institute of Food and Agriculture [NYC-145403]
- New York State Turfgrass Association
- US Department of Energy, Office of Science, Office of Biological and Environmental Research Terrestrial Ecosystem Science Program [DE-AC02-05CH11231]
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 C-4 grasses: smooth crabgrass (Digitaria ischaemum) and bermudagrass (Cynodon dactylon). Methods Plants were grown in nutrient-poor soil for 80 days with either 20 or 120 mu g 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 rhizosphere effects for both grass species.
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