Long-term post-wildfire dynamics of coarse woody debris after salvage logging and implications for soil heating in dry forests of the eastern Cascades, Washington
Long-term post-wildfire dynamics of coarse woody debris after salvage logging and implications for soil heating in dry forests of the eastern Cascades, Washington
复制标题
抢救性伐木后野火后的长期动态以及对华盛顿州喀斯喀特东部干燥森林土壤加热的影响
DOI：
10.1016/j.foreco.2008.03.048
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发表时间：
2008
影响因子：
3.7
通讯作者：
J. Agee
中科院分区：
文献类型：
--
作者：
Philip G. Monsanto;J. Agee
在华盛顿州东部喀斯喀特的奥卡诺根-韦纳奇国家森林中，评估了四次林分置换火灾对粗木屑的长期影响，分别为1、11、17和35年。所有站点的总生物量平均约为60Mgha−1，尽管原木与障碍的比例随时间顺序而增加。除了最近被烧毁的地点，被回收的林分的原木生物量更高，被回收的林分的原木生物量低于未回收的林分。湿润面比干燥面原木生物量高。燃烧后回复密度随时间增加。在一项补充实验中，测量了土壤加热和燃烧原木引起的代根死亡率，以评估如果在这些森林中重新引入火灾可能对场地造成的损害。实验燃烧的原木产生致命的表面温度（60°C），延伸到原木以外的10厘米。晚季燃烧的原木表面温度高于早季燃烧的原木。埋深热电偶的平均最高温度随土壤深度呈指数递减。大圆木、腐烂的圆木和在季末燃烧的圆木比小圆木、完好的圆木和季初燃烧的圆木产生更高的土壤温度。埋在土壤里的小直径（~ 1.25cm）活的道格拉斯杉木树枝榫作为小根的替代品，表明形成层组织受损深度为10cm，距离被烧毁的原木附近为10cm。当从每根原木的10厘米处推算出致命土壤温度带时，最古老的火灾未抢救部分的致命覆盖度高达24.7%，几乎是抢救部分的致命覆盖度的两倍。在将规定的火引入20-30年的野火后森林的地方，通过在春季燃烧，至少在mesic站点上，阴燃的粗木屑的根部加热的影响将最小化。如果在野火后的早期阶段减少过多的粗木屑负荷，对管理者来说可能会有一些长期的好处。
Long-term effects of salvage logging on coarse woody debris were evaluated on four stand-replacing wildfires ages 1, 11, 17, and 35 years on the Okanogan-Wenatchee National Forest in the eastern Cascades of Washington. Total biomass averaged roughly 60Mgha−1across all sites, although the proportion of logs to snags increased over the chronosequence. Units that had been salvage logged had lower log biomass than unsalvaged units, except for the most recently burned site, where salvaged stands had higher log biomass. Mesic aspects had higher log biomass than dry aspects. Post-fire regeneration increased in density over time. In a complementary experiment, soils heating and surrogate-root mortality caused by burning of logs were measured to assess the potential site damage if fire was reintroduced in these forests. Experimentally burned logs produced lethal surface temperatures (60°C) extending up to 10cm laterally beyond the logs. Logs burned in late season produced higher surface temperatures than those burned in early season. Thermocouples buried at depth showed mean maximum temperatures exponentially declined with soil depth. Large logs, decayed logs, and those burned in late season caused higher soil temperatures than small logs, sound logs, and those burned in early season. Small diameter (∼1.25cm), live Douglas-fir branch dowels, buried in soil and used as surrogates for small roots, indicated that cambial tissue was damaged to 10cm depth and to 10cm distance adjacent to burned logs. When lethal soil temperature zones were projected out to 10cm from each log, lethal cover ranged up to 24.7% on unsalvaged portions of the oldest fire, almost twice the lethal cover on salvaged portions. Where prescribed fire is introduced to post-wildfire stands aged 20–30 years, effects of root heating from smoldering coarse woody debris will be minimized by burning in spring, at least on mesic sites. There may be some long-term advantages for managers if excessive coarse woody debris loads are reduced early in the post-wildfire period.