Do repeated wildfires promote restoration of oak woodlands in mixed-conifer landscapes?

FOREST ECOLOGY AND MANAGEMENT

卷:427

Article

Nemens, Deborah G.^1,2  Varner, J. Morgan²  Kidd, Kathryn R.³  Wing, Brian⁴ 

[1] Univ Washington, Sch Environm & Forest Sci, Seattle, WA 98195 USA

[2] US Forest Serv, Pacific Wildland Fire Sci Lab, USDA, Pacific Northwest Res Stn, Seattle, WA 98103 USA

[3] Stephen F Austin State Univ, Arthur Temple Coll Forestry & Agr, Nacogdoches, TX 75962 USA

[4] US Forest Serv, USDA, Pacific Southwest Res Stn, Redding, CA 96002 USA

关键词: Abies concolor;    Cascade Range;    Conifer encroachment;    Fire regime;    Positive feedbacks;    Pseudotsuga menziesii;    Quercus kelloggii;    Reburn;    Resprouting;    Topkill;   

DOI  :  10.1016/j.foreco.2018.05.023

来源: Elsevier

【 摘 要 】

Oak woodlands are dependent on frequent fire to maintain the low stem density and diverse understories that typify these ecosystems. Without this recurrent disturbance, fire-sensitive conifer competitors encroach on oaks, reducing their vigor, and diminishing habitat quality. In fire-excluded oak woodlands, stand-replacing wildfire can trigger shifts in canopy dominance from seed-generated conifers to oaks, which are capable of vigorous sprouting following topkill. We examined the occurrence and sprouting dynamics of California black oak (Quercus kelloggii Newb.) following repeated wildfires in the Lassen National Forest, California. We found that following reburn, changes in oak relative stand dominance, as well as oak sprout basal area and height, were each positively related to fire severity (P < 0.0001 for each analysis). While conifer regeneration suffered complete mortality at moderate and high reburn severities, 97% of topkilled oaks resprouted from surviving rootstocks, reinforcing oak dominance. Black oak resprouts that originated following topkill in the first wildfire were frequently topkilled in the second fire, including at lower burn severities survived by advance conifer regeneration. The results of this study indicate that while as individuals, black oaks are resilient to recurring wildfire, restoration of historic woodland structure and function is an unlikely outcome of these repeated disturbances. Management of post-wildfire regenerating oak stands in this region will require supplemental fuel reduction treatments, including prescribed burning.

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