Effects of postwildfire mechanical seeding on soil properties in Wyoming big sagebrush communities

Authors: MORRA, BRIAN - University Of Nevada; Newingham, Beth; GANGULI, AMY - National Institute Of Food And Agriculture (NIFA); HOWARD, BRIAN - Former ARS Employee; SHAW, NANCY - Forest Service (FS)

Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/25/2024
Publication Date: 8/4/2024
Citation: Morra, B., Newingham, B.A., Ganguli, A., Howard, B., Shaw, N. 2024. Effects of postwildfire mechanical seeding on soil properties in Wyoming big sagebrush communities. Rangeland Ecology and Management. 96:163-172. https://doi.org/10.1016/j.rama.2024.06.011.
DOI: https://doi.org/10.1016/j.rama.2024.06.011

Interpretive Summary: Following the disturbance caused by wildfire, soil loss to wind erosion can be greatly increased. However, there is little documentation of the compounding effects of further disturbance following mechanical seeding commonly used in restoration efforts. In this submission we quantify the effects of wildfire and mechanical seeding on soil physical properties related to wind erosion in rangeland soils. To further the relevance of this work, we link these soil properties to plant cover responses to show how wind erosion can negatively impact plant growth. To our knowledge this is only the second effort to document the impact of post-fire seeding on site stability following Miller et al. (2012). This paper and its contrasting results to existing literature helps justify the importance of monitoring soils following post-fire restoration projects, as the magnitude of disturbance and recovery post-wildfire differed across sites. Furthermore, rangeland soils may be particularly vulnerable to the negative impacts of erosion as top soils are thin and form slowly. Therefore, as wildfires become larger and more frequent in rangelands, this work is of interest to ecologists and management practitioners interested in the role played by soils, plants, and seeding equipment in soil conservation of rangelands post-wildfire.

Technical Abstract: Reduction of vegetation following wildfire in rangelands of the western United States can result in invasion of exotic annual grasses and elevated soil loss to wind erosion. In response to these threats, various mechanical seeding methods (such as drill seeding and mechanical mixing of broadcast seeds) are commonly employed by restoration practitioners. Despite their common use, there is little information about how additional disturbance from mechanical seeding (following wildfire disturbance) may further contribute soil loss to wind erosion. Here we compared the effects of mechanical seeding techniques on soil properties following two wildfires occurring in similar climates with contrasting soil textures (silty loam and gravelly loam soils). Using either a rangeland or minimum-till drill to create furrows or mix broadcasted seeds into soils, we quantified wind erosion risk for unburned sites, burned non-seeded sites, and seeded sites according to soil aggregate stability, horizontal sediment flux, surface microtopography, and soil compaction. Effects of mechanical seeding were small relative to those created by wildfire. For burned areas, differences in site stability were greatest between sites. Following wildfire, the largest decrease in site stability occurred in fine textured soils, where horizontal sediment transport was increased by nearly five orders of magnitude relative to unburned areas. Despite these initial differences, site stability in fine textured soils may have improved to a greater degree than stability at the coarse textured site. Furthermore, we found minimal differences between drill types on site stability, but instead observed the largest differences in soil properties were created by furrow versus broadcast seeding. The different outcomes of rehabilitation on site stability found here, paired with the spatial extent to which wildfire affects landscapes highlights the importance of post-fire monitoring of site stability in more locations that vary by soil, plant, landscape, and climatic variables.