December 19, 2014

Horse Rock Ridge Assessment, Seed Collection, and Restoration

Denise E. L. Johnson |

This report describes actions taken in 2012 and 2013 as part of a multi-year project at Horse Rock Ridge Area of Critical Environmental Concern/Research Natural Area (ACEC/RNA).  Started in 2006,

This report describes actions taken in 2012 and 2013 as part of a multi-year project at Horse Rock Ridge Area of Critical Environmental Concern/Research Natural Area (ACEC/RNA).  Started in 2006, the purpose of this project is to assess the current condition of high-priority ecosystems at Horse Rock Ridge, prioritize native plant communities and invasive species for management action, collect seeds for restoration, and initiate site restoration.

This report discusses the preliminary results of weed removal efforts, experimentations with various treatment methods, as well as seeding and planting of native species.

Invasive Species

Several invasive species, including Cirsium ssp., Geranium dissectum, Sonchus asper, Rubus spp. and Tragopogon dubius were found only as scattered individuals or in small patches. After we identified and mapped these individuals, we either manually removed them by pulling and/or grubbing or removed all of their aboveground biomass in both spring and the fall.

Control of more ubiquitous invasive species including, Holcus lanatus, Hypochaeris radicata, Rumex acetosella, Hypericum perforatum and Leucanthemum vulgare were focused in; 1)areas of otherwise high quality, 2) in areas that were outplanted with bulbs, seeds or plugs, and 3) in areas where the offending species was found in isolated patches.

Seed Collection and Grow-out

We collected seed from native plant species in 2008, 2009, 2010, 2012 and 2013 for restoration in 2008 – 2014. Species were chosen to be representative of the flora in the mesic and xeric communities, with an emphasis on native grasses and “aggressive” forb species. Due to the large area needing restoration at Horse Rock Ridge and the relatively low amount of seeds available for restoration, we are focusing our efforts on creating ‘diversity islands’ that extend or connect medium and high quality patches of native plant species. Plants were either introduced as seeds, bulbs, or outplantings.

Experimental Treatment Plots

In 2008 plots were established to test the effects of restoration treatments in mesic (wet) and matrix (dry) meadow communities along Horse Rock Ridge. Treatments included seed addition, solarization plus seed addition, carbon + seed addition, and control.

Surviving plants in both mesic and matrix plots are generally thriving, increasing cover of native species and contributing to the native seed bank on the site.

Interim results indicate that in the mesic meadows all treatments resulted in increased cover of native grasses and decreases in invasive forbs over controls. In the mesic treatment plots survivorship from 2010-2013 is 44% (21% in control plots)

Interim results for the matrix plots indicate that seed addition is the most effective treatment at increasing native graminoid cover, however effects on native and invasive forb species is varied. In matrix (dry) islands, survivorship 4 years post-outplanting was 10% with some species as high as 25%.

Final results from this study will be reported in the 2014 final report, however preliminary results indicate that in both the mesic and xeric plots, there was a positive effect of just seed addition, suggesting that seed limitation may be the strongest factor limiting native plant cover in these meadows.