Thinning and prescribed burning increase shade-tolerant conifer regeneration in a fire excluded mixed-conifer forest

Fire exclusion and past management have altered the composition, structure, and function of frequent-fire forests throughout western North America. In mixed-conifer forests of the California Sierra Nevada, fire exclusion has exacerbated the effects of drought and endemic bark beetles, resulting in extensive mortality of fire-adapted pine species. Thinning and prescribed fire are widely used in these forests to reduce fuels, moderate fire behavior, and restore ecosystems. Tree regeneration influences future forest composition and structure, and therefore future resilience to disturbances, but long-term effects of thinning and prescribed burning on tree regeneration after prolonged fire exclusion are poorly understood. We measured tree regeneration one year prior to, and periodically for 16 years following thinning and prescribed burning in a mixed-conifer forest in the Sierra Nevada, California, USA. We asked three questions. How did the composition and density of tree regeneration chang...

火抑制（fire exclusion）与既往森林管理措施，已改变了遍布北美西部的常受火干扰森林的组成、结构与功能。在加利福尼亚内华达山脉的混合针叶林（mixed-conifer forests）中，火抑制加剧了干旱与本土树皮甲虫的危害，致使大量适应火干扰的松科树种大面积死亡。疏伐与计划火烧（prescribed fire）已在这类森林中广泛应用，用于降低可燃物载量、调控火行为并修复生态系统。树木更新（tree regeneration）会影响未来森林的组成与结构，进而决定其未来的抗干扰恢复力，但针对长期火抑制后，疏伐与计划火烧对树木更新的长期效应，目前学界对此仍知之甚少。本研究在美国加利福尼亚州内华达山脉的一片混合针叶林中，于疏伐与计划火烧实施前1年，以及之后的16年间定期监测树木更新情况。本研究提出三个核心问题：树木更新的组成与密度发生了何种变化……