资源环境科技发展态势分析平台

Prescribed fire is an important tool for rangeland management in sage-steppe ecosystems, yet the long-term effects of this practice on soil hydraulic properties are not well known. We explore interactions among site geomorphology, soil organic carbon (SOC) soil N, soil water repellency (SWR), and plant community type on infiltration properties before fire and 8 years thereafter in a semiarid research watershed. The objective was to assess the sustainability of rangeland burning in sage-steppe ecosystems. Many types of measurements were made in three plant communities to identify how differences in soil hydraulic properties are related to differences in plant cover and soil texture and to determine relationships among SOC, SWR, soil water contact angle, and infiltration properties. Measurements were made on transects in burned and unburned catchments. We found that severity and occurrence of surface SWR were substantially reduced 8 years after a fire within the area originally covered with mountain big sagebrush, where the fire intensity was greatest. Surface SWR was lowest in the sparsely vegetated low sagebrush, where SOC was also lowest. Unsaturated hydraulic conductivity (K-h) increased in each vegetation type over the 8-year period after burning and was not directly related to SWR. Spatial variability in K-h was primarily controlled by soil texture, whereas differences in sorptivity (S) were controlled by SWR and aridity. SOC is not well correlated to soil surface SWR. The decadal scale changes in K-h and associations between S and site characteristics indicate forms of resilience to fire across a moisture gradient.

Plain Language Summary Wildfire that removes vegetation can alter soil surfaces and result in erosion. Vegetation succession patterns in grazed lands can accelerate the rangeland fire cycle and alter soil properties including infiltration and organic carbon storage. This study investigated evolving interactions between soil properties and rangeland plant ecosystems from prefire conditions until 8-year postfire to clarify the changes in soil infiltration capacity. This information is intended to guide land managers who use prescribed fires to manage rangelands to limit the incidence of catastrophic fires and erosion. We found that the severity and presence of surface soil water repellency were greatly reduced 8 years after treatment in the Aspen stand, where the surface was manually burned. Although postfire decreases in soil water repellency were modest at in the big mountain sagebrush, the postfire infiltration capacity was at least twice as great as prior measurements. This indicates a positive long-term effect of prescribed fire control of big mountain sagebrush at the study site.