Abstract
BackgroundCoarse woody debris has numerous functions in forest ecosystems, including wildlife habitat, fuel loading, and nutrient cycling. Standing dead trees, or snags, are particularly important resources for wildlife, and guidelines for snag recruitment and retention are integral parts of forest management. However, snag persistence is not well understood and existing models are poorly validated. We monitored fire-killed conifer snag persistence after four California wildfires and one prescribed fire. Species sampled included white fir (Abies concolor [Gord. & Glend.] Lindl. ex Hildebr.), incense-cedar (Calocedrus decurrens [Torr.] Florin), Jeffrey pine (Pinus jeffreyi [Balf.]), sugar pine (Pinus lambertiana Douglas), and ponderosa pine (Pinus ponderosa Lawson & C. Lawson var. ponderosa C. Lawson).ResultsFire-injured trees that survived at least one year post fire were monitored for 10 years after they died. We developed two sets of species-specific snag persistence rates: a simplified model based only on time since death, and a full model that included tree characteristics. The primary factors affecting persistence rates in all models were snag age (years since death) and species. Secondary factors included diameter at breast height, time between fire and tree death, and crown injury. Snag persistence rates decreased with snag age. Yellow pine snags (a combined group of ponderosa pine and Jeffrey pine) fell significantly faster than any other species. Larger-diameter snags persisted longer than smaller-diameter snags for all species. Incense-cedar trees that survived longer post fire persisted longer as snags.ConclusionsThis study provides land managers with guidance on snag longevity, which can aid in planning for long-term wildlife habitat, fuel loading estimates, and forest structural diversity.
Highlights
Coarse woody debris has numerous functions in forest ecosystems, including wildlife habitat, fuel loading, and nutrient cycling
A total of 1140 snags were followed for 10 years after death: 96 incense-cedar, 189 sugar pine, 308 white fir, and 547 yellow pine
Conclusions and management implications Snags and downed logs are essential to forest ecosystems, providing numerous ecosystem benefits, and contributing to fuel loading (Dunn and Bailey 2015)
Summary
Coarse woody debris has numerous functions in forest ecosystems, including wildlife habitat, fuel loading, and nutrient cycling. Either as standing snags or downed logs, they play vital roles in nutrient cycling and in carbon sequestration (Harmon et al 1986; Krankina and Harmon 1995; Brais and Paré 2006). They provide habitat and foraging sites for vertebrates and invertebrates, as well as growth sites for fungi, lichen, and bryophytes (Thomas 1979; Harmon et al 1986; Bunnell and Kremsater 1990; Bull and Parks 1997). Larger snags can support more wildlife species, though a diversity of snags with varying DBH, height, decay class, and species is important to manage for a wide variety of wildlife (Raphael and White 1984; Bunnell 2013)
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