Picture: Fabrice Cahez as seen in https://tinyurl.com/2hvp5ptb
Summary
Mistletoes are parasitic plants infecting numerous North American woodlands, causing poor health and mortality to host plants. However, mistletoe infection encourages an increase in bird diversity through microhabitat structure and intertwining positive and negative effects which promote diverse perspectives on management. In this study, we attempt to inform management regimes, and examine the relationship between infection levels and microhabitats, their influence on bird presence, and the similarity in these parameters, in Oregon oak forests. Data was obtained from Pritchard, Hagar, and Shaw (2017) from within Willamette Valley in Oregon (USA). White Oregon trees (Quercus garryana) were measured for microhabitat characteristics along with oak mistletoe (Phoradendron villosum) for infection levels. Exploratory analysis consisted of Bray-Curtis distance matrix, multidimensional (ordination) scaling matrix, as well as boxplots, and bar graphs. Statistical testing consisted of pairwise comparisons (Tukey's significance test), permutational ANOVA, and linear regression. https://tinyurl.com/8bvcseky
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https://tinyurl.com/33mr8btv
Initial exploratory graphics results indicated that high mistletoe infection levels in forests show some similarities such as high deadwood, increased loose bark, high numbers of swellings, and high numbers of cavities. Additionally, results also indicated a positive relationship between bird species presence and these microhabitat characteristics. Birds common to high infection sites largely preferred mistletoe, although those most similar between all sites had a neutral preference. Mistletoe and species presence was overall not correlated with healthy indicators (DBH, height, canopy).
However, once statistical analyses were performed, percent of deadwood, amount of loose wood, and number of cavities, showed an increase in forests with high mistletoe infection levels. Although, the only microhabitat characteristic indicating significance was deadwood. Additionally, there was a significant relationship between the presence of avian species and high mistletoe infection sites over low infection sites. Nevertheless, there was no obvious relationship indicating a large number of avian species with strong similarities to microhabitat characteristics. From these results, the management method expected to preserve the most biodiversity of avian species and individuals, in these study areas, is prescribed burning. In addition to this, managers can use information to make informed decisions in forestry practices to ensure biodiversity of avian species within the area are not at risk of loss. |