Growth and reproduction decline with willow (Salix sp.) clipping for ski trail maintenance

Background/Question/Methods

Cross country ski trails located in wetlands dominated by willows (Salix) require maintenance via annual willow clipping and continual grooming through the winter months. In order to determine the potential negative effects of cross country ski trail maintenance, we set up an experiment at the Breckenridge Nordic Center in CO. A total of 3 belt transects (20 X 2 meters) were established on a cross country ski trail where willows are cut annually to 18 inches in height in October and where snow grooming by large tractors occurs through the winter months. Three control belt transects were established 2 meters to the north of the experimental plots. The belt transects were then divided into 40 separate 1 m² quadrats of which 10 quadrats in each transect were chosen by a randomly for data collection.  In all quadrats, we counted catkin production and growth rate.

Results/Conclusions

In May 2008, the clipped plots averaged 0.63 catkins per plant, while the unclipped plots averaged 19.43 catkins per plant, which was significantly different as tested by a t-test (p = 0.002). Growth in plant height was greater in unclipped plants than in clipped plants as detected by a t-test (p = 0.0437). Growth for plant branch length also differed, but this difference was not statistically significant (p = 0.067). Soil compaction did not differ between clipped and unclipped transects. However, the snow compaction on the clipped plots from intensive ski grooming resulted in a difference in the timing of snow melting and thus likely played a role in the difference in catkin production. In addition, the clipping experiment also provides evidence to support reduced growth rate of willow after significant browsing.