Department of Forest Management, University of Montana, 32 Campus Drive, Missoula, Montana 59812, USA.
Ecol Appl. 2013 Sep;23(6):1243-9. doi: 10.1890/13-0066.1.
Ecological systems often exhibit resilient states that are maintained through negative feedbacks. In ponderosa pine forests, fire historically represented the negative feedback mechanism that maintained ecosystem resilience; fire exclusion reduced that resilience, predisposing the transition to an alternative ecosystem state upon reintroduction of fire. We evaluated the effects of reintroduced frequent wildfire in unlogged, fire-excluded, ponderosa pine forest in the Bob Marshall Wilderness, Montana, USA. Initial reintroduction of fire in 2003 reduced tree density and consumed surface fuels, but also stimulated establishment of a dense cohort of lodgepole pine, maintaining a trajectory toward an alternative state. Resumption of a frequent fire regime by a second fire in 2011 restored a low-density forest dominated by large-diameter ponderosa pine by eliminating many regenerating lodgepole pines and by continuing to remove surface fuels and small-diameter lodgepole pine and Douglas-fir that established during the fire suppression era. Our data demonstrate that some unlogged, fire-excluded, ponderosa pine forests possess latent resilience to reintroduced fire. A passive model of simply allowing lightning-ignited fires to burn appears to be a viable approach to restoration of such forests.
生态系统通常表现出具有弹性的状态，这种状态通过负反馈来维持。在落矶山松林中，火历来是维持生态系统弹性的负反馈机制；防火措施减少了这种弹性，使在重新引入火时更容易过渡到另一种生态系统状态。我们评估了在美国蒙大拿州鲍伯马歇尔荒野中未被采伐且防火的落矶山松林中重新引入频繁野火的效果。2003 年初始的火灾重新引入减少了树木密度并消耗了地表可燃物，但也刺激了黑云杉的密集生长，保持了向另一种状态的转变轨迹。2011 年的第二次火灾恢复了频繁的火灾模式，通过消除许多再生的黑云杉，并继续清除地表可燃物和在防火时代建立的小径云杉和花旗松，从而恢复了以大直径落矶山松为主的低密度森林。我们的数据表明，一些未被采伐且防火的落矶山松林中具有对重新引入的火灾的潜在弹性。简单地允许闪电引发的火灾燃烧的被动模式似乎是恢复此类森林的可行方法。
