『Abstract
　In late-successional steady state ecosystems, plants and microbes compete for nutrients and nutrient retention efficiency is expected to decline when inputs exceed biotic demand. In carbon (C)-poor environments typical of early primary succession, nitrogen (N) uptake by C-limited microbes may be limited by inputs of detritus and exudates derived from contemporaneous plant production. If plants are N-limited in these environments, then this differential limitation may lead to positive relationships between N inputs and N retention efficiency. Further, the mechanisms of N removal may vary as a function of inputs if plant-derived C promotes denitrification. These hypotheses were tested using field surveys and greenhouse microcosms simulating the colonization of desert stream channel sediments by herbaceous vegetation. In field surveys of wetland (cienega（最初のeの頭に´）) and gravelbed habitat, plant biomass was positively correlated with nitrate (NO3^-) concentration. Manipulation of NO3^- in flow-through microcosms produced positive relationships among NO3^- supply, plant production, and tissue N content, and a negative relationship with root:shoot ratio. These results are consistent with N limitation of herbaceous vegetation in Sycamore Creek and suggest that N availability may influence transitions between and resilience of wetland and gravelbed stable states in desert streams. Increased biomass in high N treatments resulted in elevated rates of denitrification and shifts from co-limitation by C and NO3^- to limitation by NO3^- alone. Overall NO3^- retention efficiency and the relative importance of denitrification increased with increasing N inputs. Thus the coupling of plant growth and microbial processes in low C environments alters the relationship between N input and exports due to increased N removal under high input regimes that exceed assimilative demand.

Keywords: Denitrification; Uptake; Nutrient retention; Cienega（最初のeの頭に´）; Paspalum distichum; Regime shift』

Introduction
Methods
　Field surveys of N and plant abundance
　Experimental manipulation of N availability
　Data analyses
Results
Discussion
　Alternative states and interactions between biogeochemical and biogeomorphic processes
　Plant-microbe interactions and the fate of N inputs
Acknowledgments
References