Scotch broom (Cytisus scoparius) modifies microenvironment to promote nonnative plant communities
Scotch broom [Cytisus scoparius (L.) Link] is a globally important nitrogen (N)-fixing invasive plant species that has potential to alter soil water dynamics, soil chemistry, and plant communities. We evaluated the effects of Scotch broom on soil moisture, soil chemistry, soil temperature, photosynthetically active radiation (PAR), and vegetation communities over 4 years at a site recently harvested for timber. Treatments of Scotch broom (either present via planting or absent) and background vegetation (either present or absent via herbicide treatments) were applied to 4 m2 plots. Background vegetation was associated with the greatest decrease of soil water content (SWC) among treatments. During the driest year, Scotch broom showed some evidence of increased early-and late-season soil water usage, and, briefly, a high usage relative to background vegetation plots. On a percent cover basis, Scotch broom had a substantially greater negative influence on SWC than did background vegetation. Surprisingly, Scotch broom was not consistently associated with increases in total soil N, but there was evidence of increasing soil water N when Scotch broom was present. Scotch broom-only plots had greater concentrations of soil water magnesium (Mg2+) and calcium (Ca2+) than other treatments. On a percent cover basis, Scotch broom had a uniquely high demand for potassium (K+) relative to the background vegetation. Average soil temperature was slightly greater, and soil surface PAR lower, with Scotch broom present. Scotch broom-absent plots increased in species diversity and richness over time, while Scotch broom-present plots remained unchanged. Scotch broom presence was associated with an increase in cover of nonnative sweet vernalgrass (Anthoxanthum odoratum L.). Scotch broom generated positive feedbacks with resource conditions that favored its dominance and the establishment of nonnative grass.
KeywordsSoil properties Pacific Northwest Extended growing season Soil water
Financial support for this research was provided by the USDA National Institute for Food and Agriculture (Grants.gov number: GRANT 11325729). We wish to thank Green Diamond Resource Company for use of their land and logistical support. We would like to thank James Dollins for all of his efforts on this project.
- Dassonwille N, Vanderhoven S, Vanparys V, Hayez M, Gruber W, Meerts P (2008) Impacts of alien invasive plants on soil nutrients are correlated with initial site conditions in NW Europe. Oecologia 133:206–214Google Scholar
- Hardy RWF, Havelka UD (1976) Photosynthate as a major factor limiting nitrogen fixation by field-grown legumes with emphasis on soybeans. In: Numan PS (ed) Symbiotic nitrogen fixation in plants. Cambridge University Press, Cambridge, pp 421–439Google Scholar
- Henderson JA, Peter DH, Lesher RD, Shaw DC (1989) Forested plant associations of the Olympic National Forest. R6-ECOL-TP 001-88, U. S. Department of Agriculture, Forest Service, Pacific Northwest Region, PortlandGoogle Scholar
- Oksanen JF, Blanchet G, Friendly M, Kindt R, Legendre P, McGlinn D, Minchin PR, O’Hara RB, Simpson GL, Solymos P, Stevens MHH, Szoecs E, Wagner H (2017) Vegan: Community Ecology Package. R package version 2.4-5Google Scholar
- Parker IM, Harpole W, Dionne D (1997) Plant community diversity and invasion of exotic shrub Cytisus scoparius: testing hypotheses on invisibility and impact. In: Dunn PV, Ewing K (eds) Ecology and conservation of the Southern Puget Sound Prairie Landscape: the land conservancy. Nature Conservancy of Washington, Washington, pp 149–161Google Scholar
- Pinheiro J, Bates D, DebRoy S, Sarkar D, R Development Core Team (2013) nlme: linear and nonlinear mixed effects models. R package version 3.1-108Google Scholar
- PRISM Climate Group, Oregon State University. http://prism.oregonstate.edu. Created 4 Nov 2017
- R Core Team (2017) R: a language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. https://www.R-project.org/
- Richardson B, Whitehead D, McCracken IJ (2002) Root-zone water storage and growth of Pinus radiata in the presence of a broom understorey. NZ J For Sci 32(2):2008–2220Google Scholar
- Tutin TG, Heywood VH, Burges NA, Moore DM, Valentine DH, Walters SM, Webb DA (1968) Flora Europea, vol 2. Cambridge University Press, Cambridge, p 89Google Scholar
- Zhou T, Shi P, Hui D, Luo Y (2009) Global pattern of temperature sensitivity of soil heterotrophic respiration (Q10) and its implications for carbon-climate feedback. J Geophys Res 114:1–9Google Scholar