PS 12-102 - This could be the start of something new: Jack Pine regeneration at Altona Flat Rock, NY

Background/Question/Methods

Disturbance is essential for shaping and maintaining ecosystems. For species with adaptations to a specific disturbance regime, changes in intensity, duration, and interval of the disturbance may have adverse effects on resilience and recovery. Pinus banksiana (jack pine) is a fire dependent species relying on fire to open its serotinous cones and release seed, and create seedbeds by exposing mineral soil and removing understory competition. The Altona Flat Rock in northern New York is home to a globally rare Jack Pine dominated barrens. In 2018 a wildfire burned ~200 hectares of the Flat Rock forest providing us the opportunity to study post-disturbance recovery of Jack Pine. The goal of this study was to track seedling survival and growth at very-fine spatial scales to determine how microsite conditions affected seedling success. We randomly established three sites, each with three 1 m² plots. Each plot was subset into a 10 cm² grid where we determined the rooting substrate and percent cover of competing vegetation, along with the number of seedlings. Seedlings were monitored each fall and spring since 2018 for survival and since fall 2019 for height. We used linear regression to determine the effects of measured variables on survival and height.

Results/Conclusions

Initial seedling densities in fall 2018 ranged from 353,000 to 1,070,000 seedlings/ha across the three sites. Continued germination through 2019 offset mortality and maintained the initial density at one site, however, significant mortality occurred at the other two sites, reducing densities by 40-75%. Following the 2019 growing season no new seedlings have germinated and densities have continued to decline at all three sites. Seedling densities as of fall 2021 ranged from 57,000 to 893,000 (reductions of 16-84%). Survival was highly correlated with soil depth, % rock and % grass. In 2019 average seedling height was 3.56 cm across the three sites. By 2021 average seedling height was 10.04 cm, with the tallest seedling being 32 cm. Height was strongly correlated with soil depth and %duff. These results help elucidate the ongoing successional process and how the forest is recovering back towards its pre-disturbance state.