Forest health monitoring at Pictured Rocks National Lakeshore: 2017 field season

Sanders, Suzanne; Kirschbaum, Jessica

We initiated a comprehensive forest monitoring program at Pictured Rocks National Lakeshore in 2009 with the establishment of 59 permanent plots; we resampled these plots in 2017. Sampled and derived metrics included trees (density and basal area of live trees, seedlings, and snags), understory (frequency), browse (bite marks on woody species and presence and height of herbaceous species), species richness, and earthworm impacts. Our 59 permanent plots are divided between two management zones––43 plots are in the core zone where active management is minimal, while 16 are located in the inland buffer zone (IBZ). The IBZ is composed largely of private as well as state-owned land, and active timber harvesting occurs in this zone. In 2009, we classified sites into one of four broad forest types: Sugar Maple-Beech, Hemlock-Beech-Mixed Hardwood, Balsam Fir-Mixed Conifer, and Pine. Overall tree density in the core zone changed little within each of the forest types between the two sampling periods. However, in Hemlock-Beech-Mixed Hardwood forest in the core, Fagus grandifolia (American beech) density increased 32%, to 250 trees/ha between the sampling periods while at Sugar Maple-Beech sites in the core, F. grandifolia density increased 67% to 86 trees/ha. Like density, overall basal area changed little between the sampling periods. However, in Hemlock-Beech-Mixed Hardwood forests, basal area of Fagus grandifolia dropped 39% from 4.55 ± 0.05 m2/ha to 2.78 ± 0.06 m2/ha. In Sugar Maple-Beech forests, this dropped 57% from 2.13 ± 0.89 m2/ha to 0.91 ± 0.35 m2/ha. White-tailed deer browse was generally limited. We recorded bite makes directly visible on woody species within each of 30 browse circles per plot. This occurred in greater than 25% of circles for only three species: Taxus canadensis (Canada yew, 50%), Acer spicatum (mountain maple, 38%), and Sambucus racemosa var. racemosa (red elderberry, 28%). Browse on herbaceous species was assessed indirectly, by counting the frequency of presence in 30 quadrats per plot, for 14 preferred browse understory species. Collectively, the summed frequency of presence for all 14 species was similar within forest types between the two sampling periods. We also selected two preferred herbaceous taxa, Aralia nudicaulis (sarsaparilla) and Streptopus spp. (twistedstalk), on which to collect additional data. For both of these species, frequency of presence declined (17% and 35%, respectively), although maximum quadrat height increased slightly, by 2.15 cm for A. nudicaulis and 2.61% for Streptopus spp. The only broad-scale incidence of disease was beech bark disease (BBD), with signs and/or symptoms observed on 66% of F. grandifolia individuals. Generally, BBD impacts were not observed on individuals smaller than about 4 cm DBH. Of the 59 total plots, 11 did not show any evidence of earthworm invasion, while six were heavily invaded. Earthworm-free and minimally invaded plots tended to be located in the Kingston Sand Plain and in the areas immediately near the shore. Management recommendations focus on the beech resource. Currently, the most significant threat to PIRO forests is the impending impact of BBD. The park is engaged in a joint beech restoration effort with SLBE. While a small fraction (<1%) of naturally-occurring beech trees are resistant to the scale, the overarching goal of the program is to propagate and cross this material, so to that disease-resistant stock can be outplanted back into the forest. The park should make every effort to ensure continuity of this project, as this will be one of the most effective ways to promote overall forest integrity. The 59 permanent monitoring plots are scheduled to be resampled in 2026; trend assessments can be made at that time.

Forest health monitoring at Pictured Rocks National Lakeshore: 2017 field season

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