Temporal patterns of ungulate herbivory and phenology of aspen regeneration and defense
- 137 Downloads
Ungulate herbivory can create strong top-down effects on forest recruitment, especially after fire. Defense strategies of tree species against ungulate herbivory include escape through vertical growth and resistance through the production of defense compounds. Using a four-way fence design and camera traps we characterized the differential impacts of ungulate herbivores (deer, elk, cattle) on aspen forest recruitment and plant defense responses and how they vary depending on the timing of herbivory. Aspen height growth was greatest between June and August and ungulate use of aspen was highest in July and August. Three years after fire, height of aspen differed among fence treatments with full ungulate exclusion > deer-only plots > native ungulate plots > fenceless plots: 108 ± 4 cm, 94 ± 4 cm, 89 ± 4 cm, and 65 ± 4 cm, respectively. Fenceless plots had the highest rates of removal of apical meristems by the end of 2014 and 2015 (61% and 53%, respectively). Native ungulate plots, and deer-only plots both had similar removal of apical meristems in 2014 (37% and 39%, respectively). The highest phenolic glycoside concentrations were associated with an 80% reduction in meristem removal and four-fold greater aspen height by the end of summer. Low nitrogen was associated with an 86% reduction in apical meristem removal and threefold greater aspen height. In conclusion, our study suggests that high ungulate abundance can have detrimental impacts on forest recruitment and that high aspen defense chemistry and lower leaf N deters ungulate herbivory, especially in the late summer.
KeywordsAspen Populus tremuloides Herbivory Growth Defense chemistry Ungulates Deer Elk Phenolic glycosides Condensed tannins
We acknowledge the important contributions of Tyson Nickel, Justin Taylor, Anson Call, and Kevin Ricks for assistance in the collection of data, leaf samples, and Emma Peterson for her assistance in the lab analysis of leaf chemistry.
Author contribution statement
ACR and SBS conceived and designed the experiments. ACR, JDM and SBS performed the experiments. ACR, and RTL analyzed the data. ACR, JDM, SBS, RTL wrote and revised the manuscript.
Funding was provided by the Utah Division of Wildlife Resources and the U.S. Forest Service.
- Barton K (2015) MuMIn: Multi-Model Inference. R package version 1.15.1. http://CRAN.R-project.org/package=MuMIn
- Bernales H, Hersey KR, Shannon J (2015) Utah big game annual report. Utah Department of Natural Resources, Salt LakeGoogle Scholar
- Campbell CR (1991) Plant analysis reference procedures for the southern region of the United States. In: Plank CO (ed) Southern cooperative series, vol 368. Determination of total nitrogen in plant tissue by combustion. University of Georgia, Athens, pp 21–23Google Scholar
- Jones DB (1941) Factors for converting percentages of nitrogen in foods and feeds into percentages of protein. US Department of Agriculture-Circ, Washington DC, p 183Google Scholar
- Jones BE, Burton D, Tate KW (2005) Effectiveness monitoring of aspen regeneration on managed rangelands—a monitoring method for determining if management objectives are being met in aspen communities R5–EM–TP–004. USDA, Forest Service, VallejoGoogle Scholar
- Olsen FW, Hansen RM (1977) Food relations of wild free-roaming horses to livestock and big game. Red desert, Wyoming. J Range Manag 31:105–110Google Scholar
- Peterson EB, Peterson NM (1992) Ecology, management and use of aspen and balsam poplar in the prairie provinces, Canada, vol 1. Northern Forestry Centre, Edmonton, p 252Google Scholar
- Pinheiro J, Bates D, DebRoy S, Sarkar D, R Development Core Team (2016). nlme: Linear and nonlinear mixed effects models. R package version 3.1-120, http://CRAN.R-project.org/package=nlme
- R Core Team (2016) R: A language and environment for statistical computing. R Foundation for statistical computing, Vienna, Austria. ISBN 3-900051-07-0, URL http://www.R-project.org/
- Singh B, Tripath KP (2007) Temporal variations of nutrient concentrations in leaf and twigs of Populous deltoides trees. Indian For 133:1207–1215Google Scholar