Facilitation Differentially Affects Competitive Responses of Aspen and Subalpine Fir Through Stages of Stand Development

Authors

Rebecca Lee Molinari, Brigham Young University - Provo
Matthew F. Bekker, Brigham Young University - Provo
Benjamin D. St. Clair, Brigham Young University - Provo
Jason Bartholomew, Brigham Young University - Provo
R. Justin DeRose, Utah State UniversityFollow
Stanley G. Kitchen, United States Department of Agriculture
Samuel B. St. Clair, Brigham Young University - Provo

Document Type

Article

Author ORCID Identifier

R. Justin DeRose https://orcid.org/0000-0002-4849-7744

Samuel B. St. Clair https://orcid.org/0000-0001-6612-0329

Journal/Book Title/Conference

Ecosphere

Volume

13

Issue

3

Publisher

Ecological Society of America

First Page

1

Last Page

11

Publication Date

3-7-2022

Creative Commons License

This work is licensed under a Creative Commons Attribution 4.0 License.

Abstract

Spatial interactions between trees influence forest community succession. The objective of this study was to investigate how shifts in forest composition and proximity between tree species affect stand development over time in mixed forest systems. At six locations across the Fishlake National Forest, Utah, USA, in stands where facilitation has been documented previously, tree-ring samples were collected from aspen and subalpine fir trees. Basal area increment was calculated to characterize the effects of the proximity of overstory trees on multidecadal growth responses of aspen and subalpine fir in aspen-dominant and mixed aspen–conifer stands. Subalpine fir seedlings were established next to aspen (within 10 cm) when aspen was between 15 and 120 years old with a mean age of 60 years. Aspen and subalpine fir growth rates were reduced with increasing conifer abundance. Aspen trees growing next to a proximate subalpine fir tree had slower growth rates over time than aspen trees growing independently. Growth rates of subalpine fir in aspen-dominated stands were similar when growing independently or near aspen trees. However, subalpine fir in conifer-dominated stands maintained higher growth rates when growing next to an aspen tree than when growing independently. The data suggest that as stand competition increases with conifer abundance, the proximity of overstory trees increases competitive exclusion of aspen while having a beneficial growth effect on subalpine fir. These results underscore the importance of maintaining natural fire regimes in forest systems that keep competitive interactions in balance.

Recommended Citation

Molinari, R. L., M. F. Bekker, B. D. St. Clair, J. Bartholomew, R. J. DeRose, S. G. Kitchen, and S. B. St. Clair. 2022. Facilitation differentially affects competitive responses of aspen and subalpine fir through stages of stand development. Ecosphere 13:e3957.