Cascading Effects of Climate Change on Forest Ecosystems: Biogeochemical Links Between Trees and Moose in the Northeast USA
- 728 Downloads
The relationship between herbivores, plants and nutrient dynamics, has been investigated in many systems; however, how these relationships are influenced by changing climate has had much less attention. In the northeastern USA, both moose populations and winter climate have been changing. Moose, once extirpated from the region, have made a comeback; while locally, snow depth and duration of snow cover have declined. There is considerable uncertainty in how these changes will interact to influence forested systems. We used small experimental plots and transects along with snow removal (to elicit soil freezing and expose potential forage plants), mechanical browsing, and fecal additions (labeled with 15N) to examine ecosystem responses. We found that snow removal changed moose browsing behavior, with balsam fir more heavily browsed than sugar maple or Viburnum under low snow conditions. Soil freezing alone did not significantly alter N dynamics or selected plant responses, but there were significant interactions with moose activity. The combined effects of moose fecal additions, mechanical browsing, and soil freezing resulted in higher levels of NO3 − leaching under fir and maple, whereas Viburnum had essentially no response to these multiple factors. Our results suggest that declines in snow depth can initiate a cascade of ecosystem responses, beginning with exposure of plants to increased browsing that then triggers a series of responses that can lead to higher N losses, precipitated by decreased N demand in plants compromised by soil freezing damage. Balsam fir may be particularly susceptible to this cascade of multiple stresses.
Key wordsclimate change snow pack depth soil freezing N cycling herbivores moose 15N stable isotopes
We would like to thank Lisa Martel and Jackie Wilson for extensive assistance in both the field and laboratory. We would also like to thank John Pastor and an anonymous reviewer for helpful comments that have significantly improved this paper. This project was funded by National Science Foundation (NSF) through Grant DEB 00-75387 (Ecosystem Studies) and Grant DEB 98-10221 (Long Term Ecological Research). This research was conducted at the HBEF, which is owned and operated by the Northeastern Research Station, USDA Forest Service. This paper is a contribution to the Hubbard Brook Ecosystem Study.
- Aber JD, Melillo JM. 1980. Litter decomposition: measuring relative contributions of organic matter and nitrogen to forest soils. Can J Bot 58:416–21.Google Scholar
- Bohlen PJ, Groffman PM, Driscoll CT, Fahey TJ, Siccama TG. 2001. Plant–soil–microbial interactions in a northern hardwood forest. Ecology 82:965–78.Google Scholar
- Bontaites K. 2003. Personal communication. New Hampshire Fish and Game Department—Moose Project.Google Scholar
- Campbell JL, Rustad LE, Boyer EW, Christopher SF, Driscoll CT, Fernandez IJ, Groffman PM, Houle D, Kiekbusch J, Magill AH, Mitchell MJ, Ollinger SV. 2009. Consequences of climate change for biogeochemical cycling in forests of northeastern North America. Can J For Res 39:264–84.CrossRefGoogle Scholar
- Campbell JL, Ollinger SV, Flerchinger GN, Wicklein H, Hayhoe K, Bailey AS. 2010. Past and projected future changes in snowpack and soil frost at the Hubbard Brook Experimental Forest, New Hampshire, USA. Hydrol Process 24:2465–80.Google Scholar
- Carter MR, Ed. 1993. Soil sampling and methods of analysis. Boca Raton: Lewis Publishers.Google Scholar
- Christenson LM. 2007. The biogeochemistry of moose and soil freezing: multiple interactions influence on nitrogen cycling in a Northern Hardwood Forest. PhD Dissertation. SUNY ESF, Syracuse, p. 152.Google Scholar
- Christenson LM, Mitchell MJ, Groffman PM, Lovett GM. 2010. Winter climate change implications for decomposition in Northeastern forests: comparisons of sugar maple litter to herbivore fecal inputs. Glob Change Biol 16:2589–601.Google Scholar
- Finzi AC, Van Breemen N, Canham CD. 1998. Canopy tree–soil interactions within temperate forests: species effects on soil carbon and nitrogen. Ecol Appl 8:440–6.Google Scholar
- Frazer GW, Canham CD, Lertzman KP. 1999. Gap Light Analyzer (GLA) Version 2.0; Imaging software to extract canopy structure and gap light transmission indices from true-colour fisheye photographs, users manual and program documentation. Copy right, 1999. Millbrook: Simon Fraser University, Burnaby, British Columbia, and the Institute of Ecosystem Studies.Google Scholar
- Groffman PM, Rustad LE, Templer PH, Campbell JL, Christenson LM, Lany NK, Socci AM, Vadeboncouer MA et al. 2012. Long-term integrated studies show complex and surprising effects of climate change in the northern hardwood forest. Bioscience 62:1056–66. doi: 10.1525/bio.2012.62.12.7.CrossRefGoogle Scholar
- Krefting LW. 1974. The ecology of the Isle Royale moose with special reference to the habitat. Technical Bulletin 297–1974. Forestry Series 15. Agricultural Experiment Station, University of Minnesota.Google Scholar
- Lachat Instruments. 2012. Methods lists for automated ion analyzers. Loveland: Lachat Instruments.Google Scholar
- Mitchell MJ, McGee G, McHale P, Weathers KC. 2001. Experimental design and instrumentation for analyzing solute concentrations and fluxes for quantifying biogeochemical processes in watersheds. Methodology paper series of the 4th International Conference on ILTER in East Asia and Pacific Region, Ulaanbaatar-Hatgal, Mongolia, pp. 15–21.Google Scholar
- Pastor JB, Dewey R, Moen DJ, Mladenoff M, White , Cohen Y. 1998. Spatial patterns in the moose-forest-soil ecosystem on Isle Royale, Michigan, USA. Ecol Appl 8(2):411–24.Google Scholar
- Prasad AM, Iverson LR. 1999–ongoing. A climate change atlas for 80 forest tree species of the Eastern United States [database]. Northeastern Research Station, USDA Forest Service, Delaware, OH. http://www.fs.fed.us/ne/delaware/atlas/index.html.
- Ricard JA, Tobiasson W, Greatorex A. 1976. The field assembled frost gage. USA CRREL Technical Note, Hanover, p. 7.Google Scholar
- SAS 8.2. (2000). SAS Institute, Cary, NC, USA.Google Scholar