Ten Years of Monitoring Illustrates a Cascade of Effects of White Pine Blister Rust and Focuses Whitebark Pine Restoration in the Canadian Rocky and Columbia Mountains

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Abstract:Designer niches in which environmental variables are controlled are useful in forest restoration to enhance survival of planted tree seedlings. Here, we evaluate particular manipulated habitats, on site variables, and pre-seedling conditions hypothesized to improve the survival rate of whitebark pine (Pinus albicaulis) seedlings out-planted in Waterton Lakes National Park. The tree species is in peril due to blister rust and mountain pine beetle infestations in its range; and is a restoration priority in Waterton Lakes because populations in the park are highly infected with blister rust (up to 90%). At Summit Lake, 21 plots were set up and half of each was terra-torched; 1000 seedlings were planted in clusters of three, under four conditions: on burned areas in burned beargrass mats, in burned areas where beargrass mats were not present, in unburned areas where beargrass was present, and in unburned areas without beargrass. This study reports data for the seventh year after planting, and overall, survival was 53% for individual seedlings and at least one seedling survived in 60.8% of clusters. Planting in burned areas increased cluster survival (by 34.3%, p < 0.0001) and planting near microsites increased cluster survival (by 19.3%, p < 0.0001); the type of microsite did not make a difference. Planting in beargrass mats decreased survival, but not significantly (8.9%, p = 0.11) and this was true for burns, not unburned areas. Inoculation with native ectomycorrhizal fungi did not enhance survival most likely because controls on lightly terra-torched and unburned areas had access to local native fungi. This is the first study to report statistics on the planting of seedlings in clusters; the results need to be compared with studies where seedlings are planted individually.

Section: Discussionmentioning

confidence: 99%

Designer Niches Promote Seedling Survival in Forest Restoration: A 7-Year Study of Whitebark Pine (Pinus albicaulis) Seedlings in Waterton Lakes National Park

Cripps

Alger

Sissons

2018

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“…Our findings, although based on one study area, suggest that climate change may be increasing treeline regeneration, and that direct seeding may be a viable restoration option and climate change mitigation tool for whitebark pine. mortality that varies geographically but exceeds 90% in some locations [13,15,17,18]. Further, climate change is predicted to reduce climatically suitable areas for whitebark pine, shifting its distributional center up in elevation and northwards [19][20][21][22][23].…”

mentioning

confidence: 99%

Survival of Whitebark Pine Seedlings Grown from Direct Seeding: Implications for Regeneration and Restoration under Climate Change

Pansing

Tomback

2019

Whitebark pine populations are declining nearly range-wide, primarily from the exotic fungal pathogen that causes white pine blister rust (WPBR). Climate change is expected to exacerbate these declines by decreasing climatically suitable areas. Planting WPBR-resistant seedlings is a key restoration action, but it is costly, time consuming, and labor intensive. Direct seeding-sowing seeds rather than planting seedlings-may reduce costs and open remote areas to restoration; however, its efficacy remains largely unexplored. In this case study, we estimated the annual survival rates (ASR) of seedlings grown from directly sown seeds, and the effect of elevation zone and microsite type on survival. For five years we monitored 184 caches containing one or more seedlings within one study area in the Greater Yellowstone Ecosystem. Seed caches were originally stratified between subalpine forest and treeline and among three microsite types defined by a nurse object: Rocks, trees, and no object. To estimate ASR, we selected the most parsimonious model of a set using AICc. ASR was best described by elevation zone and year and ranged from 0.571 to 0.992. The odds of seedling survival were 2.62 times higher at treeline than in subalpine forest and were 4.6 to 36.2 times higher in 2016-2018 than 2014. We estimated the probability that a whitebark pine seed cache would contain one or more living seedlings six years after sowing to be 0.175 and 0.0584 for treeline and subalpine caches, respectively. We estimated that 1410 and 4229 caches ha −1 would need to be sown at treeline and in subalpine forest, respectively, to attain target restoration densities of 247 established trees ha −1 . Our findings, although based on one study area, suggest that climate change may be increasing treeline regeneration, and that direct seeding may be a viable restoration option and climate change mitigation tool for whitebark pine. mortality that varies geographically but exceeds 90% in some locations [13,15,17,18]. Further, climate change is predicted to reduce climatically suitable areas for whitebark pine, shifting its distributional center up in elevation and northwards [19][20][21][22][23]. Seed availability, successful seed dispersal by Clark's nutcracker (Nucifraga columbiana Wilson)-the primary seed disperser for whitebark pine-and increased regeneration in areas expected to become distributional centers will be necessary for whitebark pine to track suitable climates and claim newly available habitat [20,[24][25][26][27].Tree mortality and canopy kill from WPBR leads to declining seed availability, which is compounded by predispersal seed predation, especially of small cone crops [15,25,[28][29][30]. As a keystone and foundation species that facilitates plant establishment and growth, fosters community development, prevents erosion, protracts snow melt, and provides food and habitat for a variety of species [16,31,32], whitebark pine's decline has widespread consequences for entire ecosystems [25,33]. Conservation and restoration strategies a...

“…Notably, it would be advantageous to combine the results from a broader range of environmental conditions that could further refine suitable biophysical environment for establishment by including additional study sites that help to better characterize natural regeneration. We suggest future studies consider the role of blister rust in seedling mortality due to the potential of unknowable blister rust mortality events of seedlings at the planting sites prior to our sampling, even though probability has been found to be greater in larger trees [48].…”

Section: Opportunities and Limitationsmentioning

confidence: 99%

Biophysical Gradients and Performance of Whitebark Pine Plantings in the Greater Yellowstone Ecosystem

Laufenberg

Thoma

Hansen

et al. 2020

Research Highlights: The efficacy of planting for restoration is important for ecosystem managers. Planting efforts represent an opportunity for conserving and managing species during a population crisis. Background and Objectives: Federal agencies have been planting whitebark pine (WBP), an important subalpine species that is late to mature and long-lived, for three decades in the Greater Yellowstone Ecosystem (GYE). These efforts have been met with varying success, and they have not been evaluated beyond the first five years post-planting. Ecosystem managers will continue to plant WBP in the GYE for years to come, and this research helps to inform and identify higher quality habitat during a period of changing climate and high GYE WBP mortality rates. Materials and Methods: We use a combination of field sampling and a water balance model to investigate local biophysical gradients as explanatory variables for WBP performance at twenty-nine GYE planting sites. Results: We found that the WBP growth rate was positively correlated with actual evapotranspiration (AET) and was greatest when cumulative growing season AET was above 350 mm. Growth rate was not strongly affected by competition at the levels found in this study. However, site density change over time was negatively affected by mean growing season temperature and when more than five competitors were present within 3.59 m radius. Conclusions: If they make it to maturity, trees that are planted this season will not begin to produce cones until the latter half of this century. We recommend planting efforts that optimize AET for growth rate objectives, minimize water deficit (WD) that cause stress and mortality, and removing competitors if they exceed five within a short distance of seedlings.