Journal
ECOHYDROLOGY
Volume 7, Issue 2, Pages 453-477Publisher
WILEY
DOI: 10.1002/eco.1364
Keywords
ecohydrologic resilience; infiltration; runoff; sagebrush steppe; soil erosion feedback; thresholds; western juniper; woodland encroachment
Categories
Funding
- US Joint Fire Science Program
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Woody plant encroachment on water-limited lands can induce a shift from biotic (plant)-controlled resource retention to abiotic (physical)-driven losses of critical soil resources. The biotic-to-abiotic shift occurs where encroachment propagates connectivity of runoff processes and amplified cross-scale erosion that, in-turn, promote ecohydrologic resilience of the post-encroachment community. We investigated these relationships for woodland-encroached sagebrush steppe in the Great Basin, USA, and evaluated wildfire as a mechanism to reverse the post-encroachment soil erosion feedback. We measured vegetation, soil properties, and runoff/erosion from experimental plots on burned and unburned areas of a late-succession woodland 1 and 2years post-fire. Our findings suggest that the biotic-to-abiotic shift and amplified cross-scale erosion occur where encroachment-induced bare ground exceeds 50-60% and bare gaps between plant bases frequently extend beyond 1m. The trigger for amplified cross-scale erosion is formation of concentrated flow within the degraded intercanopy between trees. Burning in this study decreased ecohydrologic resilience of the late-succession woodland through herbaceous recruitment 2years post-fire. Increased intercanopy herbaceous productivity decreased connectivity of bare ground, improved infiltration, and reduced erosion, but the study site remained vulnerable to runoff and erosion from high-intensity rainfall. We conclude that burning can reduce woodland ecohydrologic resilience and that woodland encroachment-induced structural and functional ecohydrologic attributes may persist during high-intensity storms for an undetermined period post-fire. We cannot conclude whether wildfire reverses the woodland-induced soil erosion feedback on sagebrush rangelands. However, our results suggest that wildfire may provide a restoration pathway for sagebrush steppe by reducing woodland ecohydrologic resilience over time. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.
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