Understory vegetation response to mountain pine beetle disturbance in northern Colorado lodgepole pine forests
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Understory vegetation response to mountain pine beetle disturbance in northern Colorado lodgepole pine forests Gregory S. Pappas
. Daniel B. Tinker . Monique E. Rocca
Received: 17 April 2020 / Accepted: 16 September 2020 Ó Springer Nature B.V. 2020
Abstract 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.
Communicated by Kyle Palmquist.
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11258-020-01082-5) contains supplementary material, which is available to authorized users. G. S. Pappas (&) D. B. Tinker Department of Botany, University of Wyoming, Laramie, WY, USA e-mail: [email protected] D. B. Tinker Program in Ecology, University of Wyoming, Laramie, WY, USA
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. Keywords Understory plants Pinus contorta Tree regeneration Rocky mountains Bark beetles Vegetation dynamics
M. E. Rocca Department of Ecosystem Science and Sustainability, Colorado State University, Fort Collins, CO, USA
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Plant Ecol
Introduction Fire has historically been the primary natural disturbance agent in Rocky Mountain forests (Peet 2000), but native bark beetle outbreaks have been increasingly prevalent throughout the region over the past few decades (Meddens et al. 2012). Whereas bark beetle infestation is a natural forest-regulating proces
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