Effects and Importance of Soil Wetness and Neighbor Vegetation on Solidago verna M. A. Curtis ex Torrey & A. Gray (Spring-flowering Goldenrod) [Asteraceae] Transplant Survivorship and Growth

Castanea, Dec 2007 by Fleming, Miranda M Stanton, Stucky, Jon M, Brownie, Cavell

ABSTRACT

Solidago verna M. A. Curtis ex Torrey & A. Gray (spring-flowering goldenrod) [Asteraceae] is threatened in North Carolina, a species of federal concern, endemic to fire-adapted longleaf pine flatwoods in the Carolinas, and is in the Center for Plant Conservation's National Collection of Endangered Plants. Highway construction threatens the largest known population of S. verna. We conducted a transplant study to provide information for the plan being developed to mitigate for the impact of the highway. Plants of the threatened population were transplanted into study plots on seven Coastal Plain soils varying in wetness. Half of the plots on each soil were controls with unclipped neighbor vegetation; the others were experimental plots with clipped vegetation. Soil was the most important factor affecting transplant survival. Survival was lowest on soils that experienced ponding or flooding. Neighbor vegetation clipping tended to improve survival, with the greatest improvement on soils of intermediate wetness. Soil wetness and vegetation treatment (clipped or unclipped) accounted for only 16% of transplant growth variation. We recommend establishing a mitigation transplant population on moderately well drained or somewhat poorly drained soils such as Craven or Lenoir. Managing the transplant population could utilize mowing during those periods when fire is not practical.

INTRODUCTION Spring-flowering golden-rod [Asteraceae], Solidago verna M. A. Curtis ex Torrey & A. Gray, is threatened in North Carolina, a spedes of federal concern (North Carolina Natural Heritage Program 2006), and is in the Center for Plant Conservation's National Collection of Endangered Plants (Center for Plant Conservation n. d.). This spedes is endemic to longleaf pine (Pinus palustris Miller) flatwoods in the southern Coastal Plain of North Carolina and the Sandhills of North and South Carolina (North Carolina Natural Heritage Program 2006, South Carolina Natural Heritage Trust 1993). Solidago verna is a rosette-forming perennial of the "fire following" herb guild that maintain their abundance in flatwoods under the historical regime of low intensity, ground-level fire every two to three years (Frost 1996, Frost et al. 1986, Lemon 1949, Viro 1974, Waldrop et al. 1992). Dedine in the abundance of this fire-adapted herb guild, including 5. verna, with less frequent fire has been related to increased shading from woody spedes (Brewer and Piatt 1994, Frost et al. 1986).

The primary threats to Solidago verna are habitat degradation by fire suppression and habitat loss (Leach and Givnish 1996). For example, highway construction through a portion of the Croatan National Forest on the outskirts of Havelock, North Carolina, currently threatens the largest known population of S. verna. A mitigation plan is being developed to move individuals from this threatened population to a secure site yet to be seleded from among several sites nearby. This plan would benefit from information concerning the performance of S. verna on the soil types at these several potential transplant sites.

Brewster (1995) suggested that soil wetness is an important fador affeding Solidago verna distribution. Soil wetness can shape species composition of fire-dependent, southeastern longleaf pine plant communities (Kirkman et al. 2001) and therefore, suitability of habitat for S. verna by altering the amount and schedule of litterfall (West et al. 2003), the effeds of litter (Xiong et al. 2003), and the soil properties of texture, drainage capacity (Goodwin 1989, West et al. 2003), and redoximorphic features (Buoi et al. 2003). Variation in soil wetness is typically accompanied by differences in microtopography (Goodwin 1989) and distance to drains (Daniels and Gamble 1967).

Competition is another factor that may influence goldenrod transplant success (Brewer 1998, Howard and Goldberg 2001). Stucky and Wright (1999) found the greatest S. verna seedling establishment in field experimental plots from which herbs and shrubs were removed by clipping. They and others (Brewer and Piatt 1994) attributed these and similar results to competition.

Solidago verna is part of a fire-adapted plant community; however, managing its populations with frequent burning is problematic when they are adjacent to human populations, as are the threatened population and candidate transplant sites. Previous studies of alternative plant management methods have concluded that mowing plus raking improves survival of individual rare species relative to unmowed controls (Brewer 1998, Luken 2005) or, more generally, that mowing plus raking is an adequate option during seasons when fire is not pradical (Norden and Kirkman 2004). However, other studies concluded that mowing was not an adequate substitute for fire (Kirkman et al. 1998, Rickey et al. 2004, Taylor et al. 1998). This study was conduded to assess S. verna survivorship and growth along a soil wetness gradient under unmowed control and artificially mowed (clipped) plus raked conditions. The specific objectives were to: (1) quantify the effeds of neighboring vegetation and soil moisture on S. verna transplant survivorship and growth; and, (2) recommend a soil type to which S. verna should be transplanted for establishing new populations.