Examining the Effects of Urbanization on Soil Characteristics in Portland, Oregon\u27s Forest Park

Studies by Dr. Nancy Broshot in Forest Park, an urban forest in Portland, Oregon, have shown high tree mortality and low concomitant recruitment. Lichen surveys conducted in 2013 revealed a shift in the lichen community to one typified by nitrogen-tolerant and nitrogen-thriving species. To ascertain if nitrogenous air pollution could be a cause of low recruitment, soil samples were collected from 32 previously established study sites in Forest Park and at 3 control sites established in 2014 in the Mount Hood National Forest, a rural forest in the Clackamas River Basin. At each site, the soil O horizon depth was measured, and soil samples were collected from the A horizon, which were subsequently dried and sieved. The resulting soil samples were analyzed at the Central Analytical Laboratory at OSU to determine carbon and nitrogen concentration, as well as carbon to nitrogen ratios. The results of the soil analysis show that soil samples from the control sites had significantly higher concentrations of carbon and a significantly higher carbon to nitrogen ratio than the sites in Forest Park. These findings are quite exciting and suggest a number of possible avenues for further research

Soil Nitrogen and Carbon in Urban and Rural Forests

Previous work by Dr. Nancy Broshot has revealed high tree mortality and low recruitment (new seedlings) in an urban forest (Forest Park in Portland, Oregon). A series of lichen surveys in 2013 showed the lichen community has shifted to one dominated by lichens tolerant of and thriving on high nitrogen levels. To ascertain if nitrogenous air pollution could be a cause of low recruitment, we measured the level of nitrogen and carbon in the soil at 32 sites in Forest Park (24 permanent sites and 8 conifer recruitment sites). We also added 3 control sites in the Mount Hood National Forest above Estacada along an apparent air pollution gradient. The plant community was measured at three transects at each control site and lichen surveys were conducted. Four soil samples were collected at each site, dried at 35oC until weight remained constant and sieved to reduce to fine soil particle size. The samples will be assessed using an elemental analyzer to determine total nitrogen and total carbon

Where Have All the Young Trees Gone? A Big Picture Look at the Lack of Seedlings and Saplings in Urban Forests

We take a big picture look at the lack of seedlings, saplings and young trees in urban forests using our research in Forest Park in Portland, Oregon. Broshot, who measured vegetation at 25 sites in Forest Park, recorded significantly fewer live seedlings, saplings and young trees and significantly more dead seedlings, saplings and young trees in 2003 than in 1993. The percent mortality of western red cedar seedlings that were planted at 9 sites in Forest Park in 2005 ranged from less than 5% to over 70%. Investigations into the cause of seedling death has discounted predation by deer, elk or invertebrates, leaf disease, soil moisture, site aspect, and light as factors. The site with the highest mortality is located directly above the St John’s Bridge, suggesting air pollution. More recent work with lichens has provided evidence that nitrogen deposition related to air pollution may be the cause. We outline our past work and report preliminary results from our 2012 lichen survey analysis to support our hypothesis that pollution is a cause of the lack of young trees

Air Pollution: The Trees Aren\u27t Lichen It

The Keck Summer Collaborative Research Program provides opportunities for Linfield College students and faculty to conduct research on issues related to the Pacific Northwest, and to bring the research findings back into the classroom within the subsequent academic year. Students partner with faculty to conduct research and present their work to other students, Linfield staff and faculty, and community members during a series of brown bag lunches. Wes Hanson, Leigh Hanson, Meghan Lockwood, and Morgan Yarber conducted research with Nancy Broshot and gave this presentation during the summer of 2013

Search for singly and pair-produced leptoquarks coupling to third-generation fermions in proton-proton collisions at root s=13 TeV

A search for leptoquarks produced singly and in pairs in proton-proton collisions is presented. We consider the leptoquark (LQ) to be a scalar particle of charge -1/3e coupling to a top quark plus a tau lepton (t tau) or a bottom quark plus a neutrino (b nu), or a vector particle of charge +2/3e, coupling to t nu or b tau. These choices are motivated by models that can explain a series of anomalies observed in the measurement of B meson decays. In this analysis the signatures t tau nu b and t tau nu are probed, using data recorded by the CMS experiment at the CERN LHC at root s = 13 TeV and that correspond to an integrated luminosity of 137 fb(-1). These signatures have not been previously explored in a dedicated search. The data are found to be in agreement with the standard model prediction. Lower limits at 95% confidence level are set on the LQ mass in the range 0.98-1.73 TeV, depending on the LQ spin and its coupling lambda to a lepton and a quark, and assuming equal couplings for the two LQ decay modes considered. These are the most stringent constraints to date on the existence of leptoquarks in this scenario. (C) 2021 The Author(s). Published by Elsevier B.V.Peer reviewe