Gaseous N fluxes in Mediterranean catchments: from low elevation chaparral to high elevation subalpine ecosystems
Abstract
Recent studies on gaseous N emissions from soils in semiarid ecosystems have highlighted the importance of these losses for terrestrial ecosystems. Losses tend to be relatively large during seasonal transitions where soil rewetting results in a “hot moment” of increased biological nitrification and gaseous N flux. To gain better understanding of chaparral N-dynamics, we measured NO and N2O emissions for one year in a chamise-dominated watershed located in the foothills of the Sierra Nevada (California) whose previous nitrogen budget suggested net N retention (i.e., N inputs from atmospheric deposition > hydrologic outputs). We are also making additional gas flux measurements along an elevational gradient (300 to 2800 m) to determine if NO and N2O fluxes vary across ecosystems (chaparral, mixed conifer, and subalpine) with varying capacity for assimilation of N deposition. Gaseous N fluxes measured at the chaparral site through the one-year period are in agreement with other studies of semiarid ecosystems showing a pulse of NO (as high as 100 ng N m-2 s-1) immediately after rewetting of dry soils. The hot moment decreases by about half 24-hours after rewetting and decreases in magnitude with increasing frequency of rewetting episodes during the winter rainy season. As with other studies in semiarid ecosystems, NO emissions decreased significantly with decreases in temperature averaging about 0.03 ng N m-2 s-1 and sometimes becoming negative during the cool winter. Measurements of the magnitude of the hot moment along the altitudinal gradient are in progress, and to the best of our knowledge, will be the first field measurement to include nitric oxide fluxes in subalpine ecosystems. Based on our current data, it is clear that gaseous N fluxes are an important component in N budgets for ecosystems experiencing a strong seasonal transition in soil physico-chemical conditions.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFM.B51H0447H
- Keywords:
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- 0414 BIOGEOSCIENCES / Biogeochemical cycles;
- processes;
- and modeling;
- 0469 BIOGEOSCIENCES / Nitrogen cycling;
- 0470 BIOGEOSCIENCES / Nutrients and nutrient cycling