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United States Department of Agriculture

Agricultural Research Service

Title: Spatial and Temporal Variability of N2o Flux Rates from a Shrub Steppe Ecosystem

Authors
item Smith, Jeffrey
item Mummey, Daniel - BATTELLE PACIFIC NW
item Bolton, Harvey - BATTELLE PACIFIC NW

Submitted to: Journal of Soil Biology and Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 6, 1994
Publication Date: N/A

Interpretive Summary: In light of the increasing concern over greenhouse gases destroying ozone and contributing to global warming natural undisturbed ecosystems are being studied. These ecosystems are thought to produce significant amounts of greenhouse gases on a yearly basis and are the least studied contributors of global warming. Nitrous oxide is a greenhouse gas and is known to be produced in shrub-steppe ecosystems from microbial processes. Quantification of this gas is difficult in this system because its production is influenced by plants and they are scattered randomly over the landscape. In this study we have shown how to use geostatistical methods to estimate gas production over the landscape while taking into consideration areas of high and low gas production. In addition this is the first study which has shown that nitrous oxide production is significantly influenced by precipitation events and that production within 24 h after rainfall can contribute over 25% of the total yearly production. This study will significantly impact N2O flux estimates from these types of ecosystems.

Technical Abstract: This study was conducted to examine the spatial and temporal characteristics of N2) flux from an undisturbed shrub-steppe ecosystem having spatially heterogeneous plant cover. Over one year we periodically measured N2O flux from the soil surface and soil NH4+ and NO3- concentrations from 44 points on 2.4 m2 sample grids centered on individual A. tridentata shrubs. Spatial data were analyzed using univariate and bivariant statistics and geostatistical methods. Our results show that spatial and temporal variations can significantly affect estimates of ecosystem N2O flux. N2O flux is spatially associated with vegetation only at times when substantial N2O flux occurs which is strongly associated with vegetation. Nitrous oxide flux occurring within 48 hours after warm season precipitation events was estimated to account for 21% of the total annual N2O flux to the atmosphere from this ecosystem. Based on periodic measurements the annual N2O flux from this shrub-steppe ecosystem was estimated to be 0.15 Kg N2O-N ha-1 yr.

Last Modified: 9/29/2014
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