Understory plants are an important element of forests, having a considerable influence on ecosystem functioning and canopy-tree development following disturbance. Recent bark beetle outbreaks across western North American forests have caused extensive canopy mortality, creating new growing conditions that provide the opportunity for changes within the intact understory. Over a five-year period following peak mountain pine beetle (MPB) activity across lodgepole pine-dominated forests in Rocky Mountain National Park, Colorado, we measured the changes in plant diversity, cover, and dominance by lifeform and quantified tree regeneration rates. Average species richness and diversity increased, but overall plant cover did not change. Graminoids appeared to benefit the most, increasing in average cover, richness, and relative dominance. The rise in graminoid dominance was largely at the expense of shrubs, which showed little ability to benefit from overstory mortality within the first years following attack. Most plant responses were positively related to the total tree basal area lost since the peak of the outbreak, suggesting that increased resource availability following tree death may benefit understory plants. However, a negative relationship between several understory variables and tree sapling density provides evidence that understory plants compete with saplings for the newly available resources. Tree seedling density nearly doubled over the duration of the study, indicating a strong regeneration pulse. Among species, lodgepole pine displayed the greatest tree seedling establishment. This is one of the first studies to use repeated measurements to describe this often-overlooked component of forest change associated with MPB disturbance.

林下植物是森林的重要元素，对扰动后的生态系统功能和冠层树木发育具有相当大的影响。北美西部森林最近发生的树皮甲虫暴发已经造成了广泛的树冠死亡率，创造了新的生长条件，为完整的林下树木的变化提供了机会。在科罗拉多州洛矶山国家公园，在以松树为主的森林中，山松甲虫（MPB）达到峰值活动之后的五年内，我们通过生命形式和定量的树木再生速率来测量植物多样性，覆盖度和优势度的变化。平均物种丰富度和多样性有所增加，但总体植物覆盖率没有变化。类固醇似乎受益最大，其平均覆盖率，丰富度和相对优势度增加。类固醇优势的增加主要是以灌木为代价的，灌木在袭击后的头几年内几乎没有能力受益于过高的死亡率。自疫情爆发以来，大多数植物的反应都与树木总的基础面积减少呈正相关，这表明树木死亡后增加的资源利用率可能有益于林下植物。但是，一些林下变量与树苗密度之间的负相关关系提供了证据，表明林下植物与树苗竞争新的可用资源。在研究期间，树木的幼苗密度几乎翻了一番，这表明有很强的再生脉冲。在物种中，黑松显示出最大的树苗树立。