Spatio-temporal variations determine plant-microbe competition for inorganic nitrogen in an alpine m

• 作 者: Xingliang Xu Hua Ouyang Andreas Richter Wolfgang Wanek Guangmin Cao Yakov Kuzyakov
• 出 处: 第二届全国稳定同位素新技术开发与应用交流研讨会
• 发表日期: 2013年7期
• 关键词: 15N tracer alpine Kobresia meadow ammonium inorganic N nitrate plant-microbe com

　　1.Plant-microbe competition for available nitrogen (N) has been suggested to be an important mechanism controlling N limitation of plants in a variety of ecosystems.However, spatio-temporal patterns of competition between plants and microbes for soilNremain unclear.2.Short-term 15N tracer experiments were conducted during a growing season (July, August and September) in an alpine meadow on the Tibetan Plateau to unravel spatio-temporal patterns of plant-microbe competition for NH4+ and NO3-).3.Alpine plants were poorer competitors than soil microorganisms for inorganic N in July compared with August and September.Occupation of soil volume by roots and root density (high in August and September) played a greater role in plant-microbe competition than air temperature or precipitation (high in July).4.In topsoils (0 ~ 5 cm, highest root density), alpine plants effectively competed with soil microorganisms for N and showed a preference for 15NO3), while soil microorganisms that preferentially took up 15NH4+ out-competed plants below 5 cm soil depth (lower root density).Competition between plants and soil microorganisms for inorganic N strongly depended on root density (P < 0.0001, R2 =0.93, exponential decay model).5.Synthesis.Plant-microbe competition for inorganic N showed a clear spatio-temporal pattern in alpine meadows depending on (i) root density and therefore soil depth, (ii) inorganic N form, and (iii) different periods during the growing season.These findings have important implications for our understanding of above-ground-below-ground interactions and plant-microbial competition for available N.