Ponderosa pine introduction methods following a high-severity stand-replacing fire to promote forest regeneration

Abstract

Abstract Background In July 2012, a lightning strike ignited the Arapaho Fire in the Laramie Mountains of Wyoming and burned approximately 39,700 ha. This high-severity fire resulted in 95% mortality of ponderosa pine (Pinus ponderosa P. & C. Lawson) at the University of Wyoming’s Rogers Research Site. Ponderosa pine recruitment post-high-severity wildfire is limited in semi-arid and mid-elevation forests in the Rocky Mountain region due to the reduction of seed supplies from living trees, warm temperatures, and limited precipitation. We used an experimental block design to determine management treatments that would increase ponderosa pine abundance, and we measured the impacts to the vegetation community, ground cover, and bare ground following a high-severity wildfire. Treatments included a combination of one pine introduction treatment (natural regeneration, broadcast seeding, and planted seedlings), one logging treatment (no logging, bole only removal, whole tree removal), and erosion control seeding (no erosion seeding and seeding with a native grass mix) in each plot within a block. Results Our results indicate that the pine introduction treatment “planted seedlings” was the most effective restoration treatment in semi-arid, mid-elevation sites, although the overall survival rate of seedlings from initial planting in 2015 to 2017 was only 6%. “Whole tree removal” had a weak positive effect on the “planted seedlings” ponderosa pine abundance. The estimated mean percent moss cover was higher in the “no logging” treatment, and this treatment resulted in a lower mean percent bare ground. Overall, 2 years after implementation, the management treatments did not result in different vegetation communities. Conclusions No difference in vegetation functional group cover among the pine introduction and logging treatments at the RRS is likely due to the large landscape heterogeneity with differing slopes and two different aspects coupled with the short time frame since the implementation of the treatments at the site. The direct implications of these findings suggest that hand planting ponderosa pine seedlings is an effective way for managers to reintroduce ponderosa pine 3 years following a high-severity wildfire in semi-arid and mid-elevation sites in the northern Rocky Mountains.