Annual nitrous oxide flux and soil nitrogen characteristics in sagebrush steppe ecosystems

Abstract

Abstract. Soil nitrogen transformations and nitrous oxide fluxes were measured in a range of sagebrush steppe ecosystems in south-central Wyoming. Net nitrate production, measured in laboratory incubations, was highest in the ecosystem type dominated by Artemisia tridentata ssp. vaseyana, especially early in the growing season. Fluxes of nitrous oxide, measured in closed chambers and analyzed by gas chromatography, also tended to be higher in the same type, but only for short periods in the spring. Thereafter, all nitrous oxide fluxes were low and did not differ consistently among types. Estimated average annual fluxes for three Artemisia ecosystem types (dominated by Artemisia tridentata ssp. vaseyana, Artemisia tridentata ssp. wyomingensis, and Artemisia nova) were 0.32, 0.23 and 0.13 kg N,O-N ha-'y-r repsectively. Average annual flux, weighted by the areal extent of these and other vegetation types in the region, was approximately 0.21 kg N,O-N ha-'y-l. Assuming this landscape is representative of sagebrush steppe, we calculate a flux of 9.5 X lo9 g y-' of N,O-N from U.S. sagebrush steppe, and a flux of 1.1 X 10" g y-l of N,O-N from analogous desert and semi-desert shrublands of the world.

Plant productivity and nitrogen gas fluxes in a tallgrass prairie landscape

“…Our results offer strong support for the idea that there are inherent relationships between plant and microbial processes, including trace gas fluxes (Myrold et al 1989;Zak et al 1990;Matson et al 1991). Plant productivity and N gas fluxes were strongly correlated in tallgrass prairie because both are constrained by water and N availability (Knapp and Seastedt 1986;Hayes and Seastedt 1989;Schimel et al 1991b;Seastedt et al 1991).…”

“…A useful approach for evaluating microbial processes at landscape scales is to establish relationships between these processes and ecosystem properties that are easily estimated at large scales. Different ecosystems within a landscape are the integrated product of many site factors and exhibit distinctive patterns of vegetation, soils and biogeochemical processes (including trace gas emissions) in response to differences in water and nutrient availability (Matson et al , 1991Burke et al 1991;Groffman 1991;Schimel et al 1990Schimel et al , 1991aLauenroth et al 1993). Ecosystembased approaches to scaling can range from static, classification based techniques to more dynamic functional approaches, often based on simulation models Running 1990;Burke et al 1990).…”

Fluxes of nitrous oxide and methane from nitrogen-amended soils in a Colorado alpine ecosystem

“…Chamber rings remained in place for throughout the summer. We measured fluxes by sealing the chambers with 2.5 an ABS cover fitted with a single injection port and a second port to equalize pressure during sampling (Matson et al 1991).…”

Landslides Caused Deforestation

“…For these reasons alluvial fans at valley bottoms typically exhibit higher rates of most ecosystem processes than do ridges or shoulders of slopes. In brief, soils in lower slope positions have greater soil moisture, more soil organic matter content, and higher rates of nitrogen mineralization and gaseous losses than upslope soils (Matson et al 1991). Therefore, on geological timescales, landslides help produce stable land suitable for agricultural and habitation (for tropical islands, also tourism) and provide materials that form fertile plains and valleys, beaches, and barrier islands.…”