科研之友
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摘要
The nitrate (NO3-) removal capacity of riparian zones is well documented, but information is lacking with regard to N2O emission from riparian ecosystems and factors controlling temporal dynamics of this potent greenhouse gas. We monitored N2O fluxes (static chambers) and measured denitrification (C2H2 block using soil cores) at six riparian sites along a fourth-order stretch of the White River (Indiana, USA) to assess the effect of flood regime, vegetation type, and forest maturity on these processes. The study sites included shrub/grass, aggrading (<15 yr-old), and mature (>80 yr) forests that were flooded either frequently (more than four to six times per year), occasionally (two to three times per year), or rarely (every 20 yr). While the effect of forest maturity and vegetation type (0.52 and 0.65 mg N2O-m(-2) d(-1) in adjacent grassed and forested sites) was not significant, analysis of variance (ANOVA) revealed a significant effect (P < 0.01) of flood regime on N2O emission. Among the mature forests, mean N2O flux was in this order: rarely flooded (0.33) < occasionally flooded (0.99) < frequently flooded (1.72). Large pulses of N2O emission (up to 80 mg N2O-m(-2) d(-1)) occurred after flood events, but the magnitude of the flux enhancement varied with flood event, being higher after short-duration than after long-duration floods. This pattern was consistent with the inverse relationship between soil moisture and mole fraction of N2O, and instances of N2O uptake near the river margin after flood events. These results highlight the complexity of N2O dynamics in riparian zones and suggest that detailed flood analysis (frequency and duration) is required to determine the contribution of riparian ecosystems to regional N2O budget.
- 出版日期2012-1
