Conifer expansion reduces the competitive ability and herbivore defense of aspen by modifying light environment and soil chemistry
Open Access
- 20 May 2011
- journal article
- research article
- Published by Oxford University Press (OUP) in Tree Physiology
- Vol. 31 (6), 582-591
- https://doi.org/10.1093/treephys/tpr041
Abstract
Disturbance patterns strongly influence plant community structure. What remains less clear, particularly at a mechanistic level, is how changes in disturbance cycles alter successional outcomes in plant communities. There is evidence that fire suppression is resulting in longer fire return intervals in subalpine forests and that these lengthened intervals increase competitive interactions between aspen and conifer species. We conducted a field and greenhouse study to compare photosynthesis, growth and defense responses of quaking aspen and subalpine fir regeneration under light reductions and shifts in soil chemistry that occur as conifers increase in dominance. The studies demonstrated that aspen regeneration was substantially more sensitive to light and soil resource limitations than that of subalpine fir. For aspen, light reductions and/or shifts in soil chemistry limited height growth, biomass gain, photosynthesis and the production of defense compounds (phenolic glycosides and condensed tannins). Biomass gain and phenolic glycoside concentrations were co-limited by light reduction and changes in soil chemistry. In contrast, subalpine fir seedlings tended to be more tolerant of low light conditions and showed no sensitivity to changes in soil chemistry. Unlike aspen, subalpine fir increased its root to shoot ratio on conifer soils, which may partially explain its maintenance of growth and defense. The results suggest that increasing dominance of conifers in subalpine forests alters light conditions and soil chemistry in a way that places greater physiological and growth constraints on aspen than subalpine fir, with a likely outcome being more successful recruitment of conifers and losses in aspen cover.Keywords
This publication has 34 references indexed in Scilit:
- Quantifying successional rates in western aspen woodlands: Current conditions, future predictionsForest Ecology and Management, 2009
- Fire history and the structure and dynamics of a mixed conifer forest landscape in the northern Sierra Nevada, Lake Tahoe Basin, California, USAForest Ecology and Management, 2007
- Genotype and environment determine allocation to and costs of resistance in quaking aspenOecologia, 2006
- EFFECTS OF CONIFERS AND ELK BROWSING ON QUAKING ASPEN FORESTS IN THE CENTRAL ROCKY MOUNTAINS, USAEcological Applications, 2005
- Twenty-year change in aspen dominance in pure aspen and mixed aspen/conifer stands on the Uncompahgre Plateau, Colorado, USAForest Ecology and Management, 2005
- A fire history from tree rings in a high-elevation forest of Rocky Mountain National ParkCanadian Journal of Forest Research, 2004
- VEGETATION DYNAMICS UNDER FIRE EXCLUSION AND LOGGING IN A ROCKY MOUNTAIN WATERSHED, 1856–1996Ecological Applications, 2003
- Biodiversity, disturbances, ecosystem function and management of European forestsForest Ecology and Management, 2000
- The disturbance of forest ecosystems: the ecological basis for conservative managementForest Ecology and Management, 1994
- On Distance Estimators of Density in Randomly Distributed ForestsPublished by JSTOR ,1971