Introduction
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Background & Rational
Mistletoes are an umbrella group of parasitic plants, attaching to the stem of tall shrubs, and coniferous and hardwood trees (Mathiasen et al., 2008, Pritchard et al. 2017). They are globally relevant, but most abundant and ecologically significant in North American conifer forests (Norton & Carpenter, 1998; Geils et al., 2002). Mistletoes absorb water and carbon nutrient from host trees, reducing their growth and productivity, increasing poor health indicators (dead wood, loose bark, decay cavities), and eliciting mortality in severe infections (Howel & Mathiasen, 2004; Mathiasen et al., 2008; Griebel et al., 2017).
Mistletoes are an umbrella group of parasitic plants, attaching to the stem of tall shrubs, and coniferous and hardwood trees (Mathiasen et al., 2008, Pritchard et al. 2017). They are globally relevant, but most abundant and ecologically significant in North American conifer forests (Norton & Carpenter, 1998; Geils et al., 2002). Mistletoes absorb water and carbon nutrient from host trees, reducing their growth and productivity, increasing poor health indicators (dead wood, loose bark, decay cavities), and eliciting mortality in severe infections (Howel & Mathiasen, 2004; Mathiasen et al., 2008; Griebel et al., 2017).
Paradoxically, mistletoe density is positively associated with insect and wildlife diversity by providing food, shelter, nesting, and structure (Aukema, 2003; Winter & Moller, 2008; Mellado et al., 2019). Birds are among the largest foragers and serve numerous ecological roles but suffer global habitat and diversity loss (Niemi et al. 1998). Oak dominated forests house a richness of migratory birds and species rare to conifer forests (Hagard & Stern, 2001; Oregon Conservation Strategy, n.d.) but have decreased ~97% since European settlement. For example, the Willamette Valley is such a place, now only offering 1% of the original oak habitat as a result of habitat loss and fragmentation (Noss et al., n.d.), can feature highly specialized species not found in the surrounding areas of coniferous forests (Altman & Stephens, 2012). Therefore, understanding microhabitat and preference complexities under mistletoe then allows a wider scope on ecosystem integrity and prioritization.
Mistletoe impacts are increasing under global climate change, where mistletoe adaptability and increasing eco-physiological tree stress accelerate mortality and lumber losses (Griebel et al. 2017). Consequently, foresters have focused on their eradication as pests (Geils et al., 2002) while ecologists favor biodiversity preservation (Shaw et al., 2004). The interactions of social, environmental, and economic pillars resulting from mistletoe forests formed the study rationale. A management regime that balances stakeholder interests could be formed, and site similarity offers insightful additions to existing Pritchard et al. (2017) data.
Mistletoe impacts are increasing under global climate change, where mistletoe adaptability and increasing eco-physiological tree stress accelerate mortality and lumber losses (Griebel et al. 2017). Consequently, foresters have focused on their eradication as pests (Geils et al., 2002) while ecologists favor biodiversity preservation (Shaw et al., 2004). The interactions of social, environmental, and economic pillars resulting from mistletoe forests formed the study rationale. A management regime that balances stakeholder interests could be formed, and site similarity offers insightful additions to existing Pritchard et al. (2017) data.
Research Objectives
We aim to pinpoint how oak infection levels alter microhabitat characteristics, and their resulting influences on bird presence or diversity. Therefore, research questions are: A) How does mistletoe infection levels influence microhabitats (i.e. tree characteristics) of the forest? B) How do changes in mistletoe infection levels alter bird presence and similarity? |
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Two treatment levels, thereafter referred to as infection levels (high/low), will be compared against microhabitat characteristics and bird species to identify trends or dissimilarities. Overall, this will decide between even and un-even age cutting, cut-block isolation (leaving uniform patches of mistletoe), sanitation thinning (removing particular trees, remove only near harvest sites), and prescribed burning.
Expected Results
1)We expect a positive, directly proportional relationship between high infection and levels of dead wood, loose bark, bark swelling, and cavities. Stunted growth effects would produce a negative relationship with canopy volume, tree height, and DBH.
2) Low infection levels undergo less water and nutrient stress, and would have a negative relationship with poor health indicators (dead wood, loose bark, etc.), while healthy indicators would be positively correlated.
3) Given forage and nesting abilities, we expect a positive relationship between mistletoe infection and bird diversity. There would also be a greater presence of mistletoe preferred birds in high infection sites.
4) The tradeoff of healthy indicators for unhealthy with increasing mistletoe infection produces dissimilar conditions.
Alternatively, high infection may neutrally influence microhabitats or enhance them, dead wood and other parameters may decrease or remain the same. Likewise, low mistletoe infection may possess equal or greater unhealthy indicators on avian diversity. Microhabitat and avian similarity may also exist between infection levels.
1)We expect a positive, directly proportional relationship between high infection and levels of dead wood, loose bark, bark swelling, and cavities. Stunted growth effects would produce a negative relationship with canopy volume, tree height, and DBH.
2) Low infection levels undergo less water and nutrient stress, and would have a negative relationship with poor health indicators (dead wood, loose bark, etc.), while healthy indicators would be positively correlated.
3) Given forage and nesting abilities, we expect a positive relationship between mistletoe infection and bird diversity. There would also be a greater presence of mistletoe preferred birds in high infection sites.
4) The tradeoff of healthy indicators for unhealthy with increasing mistletoe infection produces dissimilar conditions.
Alternatively, high infection may neutrally influence microhabitats or enhance them, dead wood and other parameters may decrease or remain the same. Likewise, low mistletoe infection may possess equal or greater unhealthy indicators on avian diversity. Microhabitat and avian similarity may also exist between infection levels.