Overview

At Kikomun Creek Provincial Park and Yaq ̓itʔa·knuqⱡi’it, a combination of burning and herbicide application shows potential for reducing invasives and shrub cover, but there is also evidence that desirable native vegetation, particularly native forbs, could be damaged by herbicide application, while bunchgrasses may be negatively affected by burning.

Kikomun Creek Provincial Park: Needlegrass Sites

Overall, needlegrass (NG) sites were significantly more affected by treatments than the pinegrass sites. Bunchgrasses, shrubs, and both invasive species were all affected in some way by treatments (Figure 2). Bunchgrasses and shrubs both declined under burning, but did not significantly change under herbicide treatments. Both Hypericum perforatum and Potentilla inclinata were affected by spray, with Hypericum perforatum also affected by burning (Table 3). When compared to the control, application of HerbicideR and HerbicideC in burned plots caused a significant decrease in Hypericum perforatum cover. Potentilla inclinata declined under HerbicideR in both burned and unburned plots (Table 4).  

In burned plots, bunchgrasses declined more in burned plots than in unburned plots, as did shrubs. Spraying only affected invasive species. In burned plots that were not sprayed, Hypericum perforatum increased by 0.8%, while it declined in HerbicideC and HerbicideR plots (0.2%). Potentilla inclinata declined more in both burned HerbicideR plots (1.3%) and unburned HerbicideR plots (2.4%) compared to unburned control plots, where cover increased by 0.2% and burned control plots (1%) (Figure 2).

Yaq ̓itʔa·knuqⱡi’it

Overall, vegetation at sites at YFN were affected by both burning and spraying, with both native and invasive vegetation affected at p=0.05. Only annual invasive grasses were unaffected by treatment (Figure 3). Bunchgrasses were affected by burning and spraying but were not affected by the combination. Native forbs were only affected by herbicide application. Perennial invasive forbs were also only affected by herbicide application (Table 5). When compared to control perennial native forbs declined under all herbicide treatments in burned plots. Regardless of burning, invasive forbs were affected by both HerbicideR and the combination of HerbicideR and HerbicideP (Table 6).  

Native forbs declined under all herbicide treatments in burned plots. In unsprayed burn plots they increased by 2%, while they declined by 1.8% in HerbicideR plots, 0.3% in HerbicideP plots, and 0.7% in plots where both herbicides were combined. Invasive forbs were affected by herbicide regardless of burning. They increased under burning when no herbicide was applied (1%), while they declined either under HerbicideR alone (3.3%) or under the combination of HerbicideR and HerbicideP (2.5%). The pattern was similar in unburned plots (Figure 3).

Recommendations

Recommendations can be made based on the results from this research. Burning did not have positive effects on invasive species, but did reduce cover of shrubs, which indicates it has promise as a treatment for combatting shrub and tree encroachment. Herbicide also showed promise as a treatment, showing potential for decreasing invasive species cover at KCPP needlegrass sites and at YFN sites.

HerbicideP, the pre-emergent herbicide, did not show any significant effects on either broadleaf invasive species or invasive annual grasses, indicating it may not be a feasible treatment. However, both HerbicideR and HerbicideC, which are broadleaf herbicides, reduced invasive species at most sites, with HerbicideR showing slightly better results. HerbicideR also damaged native forbs at YFN.

At pinegrass type sites at KCPP, burning alone may be the most effective ecosystem restoration technique. At needlegrass type sites at KCPP, a combination of HerbicideR and burning are most effective for ecosystem restoration. At YFN, HerbicideR alone will control invasive species the most effectively, albeit at the cost of some native forbs.