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Abstract

Long term and large-scale ecological studies often require intensive sampling and replication. However, the inevitable impacts resulting from intensive researcher activity are often considered negligible and largely ignored in data analysis and interpretation of ecological data. This thesis study examines the impact of researcher trampling activity on the density and diversity of understory fern and woody seedling communities in a northern temperate forest research plot in Northern Wisconsin. I established thirty 1X1 m plots in heavily trampled, moderately trampled, and untrampled locations on and near the Wabikon Lake Forest Dynamics Plot. Fern and woody seedlings were identified to species, and fern species richness and Shannon’s diversity scores for woody seedlings analyzed for each plot and across trampling treatments. Fern and woody seedling diversity varied significantly with trampling intensity (ferns: Chi 2 = 9.772, df = 2, p = 0.008; woody seedlings: Chi 2 = 10.546, df = 2, p = 0.005). Decreases in fern density occurred between control and moderately trampled (MW = 269.000, WW = 734.000, p = 0.006) and between control and heavily trampled locations (MW = 283.500, WW = 784.500, p = 0.012), however moderately and heavily disturbed locations did not vary significantly in fern density (MW = 405.500, WW = 870.500, p = 0.485). Overall seedling density showed no significant variation between trampling treatments, however individual species assessments of Acer saccharum and Fraxinus americana seedlings indicate a significant decrease between trampling treatments for both species. Fraxinus americana seedling density decreased significantly control and moderately trampled (MW = 306.000, WW = 771.000, p = 0.031) and control and heavily trampled plots (MW = 317.500, WW = 782.500, p = 0.047), with no significant decrease between moderately and heavily trampled plots (MW = 436.000, WW = 901.000, p = 0.832). Conversely, Acer saccharum seedlings did not decrease significantly between control and moderately trampled plots (MW = 440.500, WW = 905.500, p = .874), but decreased significantly between control and heavily trampled (MW = 310.000, WW = 775.000, p = 0.008) and between moderately and heavily trampled locations (MW = 322.500, WW = 787.500, p = 0.013). Significant reductions in density and diversity of understory communities suggest that researcher activity can significantly alter a study ecosystem. This has both ecological and ethical implications, as researcher-induced alterations to understory composition may bias ecologists’ understanding of ecosystem dynamics and ecosystem response to environmental change.

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