1,720,972 research outputs found
The Relationship between Fungi and Tree Recruitment in Urban Forests
No full textIn 1993, I began doing research at 25 permanent study plots in Forest Park in Portland, Oregon. In 2003 and 2013, I found high tree mortality in Forest Park including seedlings and saplings. I added three control sites in the Mount Hood National Forest in 2013, which showed significantly lower numbers of young trees (recruitment) in the urban forest than at rural sites. Soil analysis showed deeper O horizons, higher C/N ratios, and higher soil respiration at more rural sites. My hypothesis is that nitrogenous air pollution at urban sites is affecting mycorrhizal fungi that should be associated with trees. Last summer, two students and I collected and identified macrofungal fruiting bodies (i.e., mushrooms) at my sites, and we noted characteristics associated with them. We also set up an iNaturalist site so citizen scientists could become involved.
We identified 40 genera of mushrooms; citizen scientists using iNaturalist identified 48 (note they collected all year whereas we only collected in the summer). We found more mushrooms per site in the old growth and National Forest areas than in Forest Park; we also found the greatest percent of mycorrhizal mushrooms in the National Forest where there is less nitrogenous air pollution. Neither of these findings were significant, however we had a low sample size and only a few months of data collection. The data from iNaturalist showed similar trends. We intend to continue the study this coming summer to increase our sample size and to compare our mushroom results to soil chemistry data from 2019
Sabbatical Leave Report
No full textI have been examining the effects of urbanization on forested areas in the Portland, Oregon area since 1993. My early work focused on the plant and avian (bird) communities. That initial study showed changes that correlated with urbanization. A follow-up study in 2003 at my same sites showed higher than normal tree mortality, especially for seedlings and saplings. A lack of young trees (i.e., recruitment) combined with high tree mortality can dramatically change the structure and function of the future forest. In 2013, I did another complete inventory at my 25 sites in Forest Park and added three locations in the Mount Hood National Forest as control sites. Data from these sites has revealed the lack of seedlings to be an urban issue. I believe the changes I am seeing in forest structure are being driven by air pollution, mostly nitrogen oxides from transportation sources. Most of my research has been accomplished through the aid and assistance of many Linfield undergraduate students. My main goal for my sabbatical was to write a paper on the changes in the urban tree community. That paper is in an almost finished draft form; however, I realized I was lacking critical information for a solid paper and so focused last summer on collecting data that would make my paper much stronger
Seedling Growth and Survival Relative to Soil Characteristics
No full textIn previous work, I found that urban forests have few to no seedlings and saplings compared to more rural forests. To determine possible reasons for this finding, William McCuen helped me examine invasive earthworms and soil characteristics at my permanent research sites in Forest Park and control sites in the Mount Hood National Forest. Austen Bassler, an Oregon City high school student, and I collected earthworms and measured soil characteristics, as well as located and measured all living and dead seedlings and saplings at my permanent research sites. We measured the depth of the O horizon (the leaf litter) and measured 24-hour CO2 production from soil collected at the sites to determine respiration rates. We also examined seedling roots for the presence and/or absence of mycorrhizael fungi.
The earthworm data collected last summer, combined with that collected the previous summer, showed no correlation between worm density or biomass and urbanization, suggesting earthworms are not related to the loss of seedlings at urban sites. We found the depth of the O horizon and the amount of CO2 to be significantly higher at rural sites than in the urban forest. However, due to equipment failure, we did not get all the soil analyzed. We found the density, total diameter, and total height of seedlings and saplings to be significantly greater at the control sites than at any urban location in both 2013 and 2018. Although these variables appeared to be lower in 2018 than in 2013, the differences were not significant. The five-year time frame was not long enough to reveal significant changes. Our examination of previously collected seedling roots revealed the presence of mycorrhizae; however, our methods were not adequate to give precise quantitative data
Twenty Years of Change in the Tree Community in Forest Park
No full textIn 1993, 24 permanent sites were randomly located in Forest Park with one additional site in the Ancient Forest Preserve. Three 250-meter square quadrats were randomly located at each site. All trees within each quadrat were identified to species and the dbh (diameter at breast height) of each tree was measured. Data were initially collected in 1993, and measurements were repeated in 2003 and in 2013 using the Faculty-Student Summer Collaborative Research grant. We found significantly fewer live trees and live seedlings and saplings (treesdbh) in each decade, although the rate of loss appears to be slowing. When examined by section of the park (city, middle, far, old growth), the far section had significantly more live trees and saplings than did the city section, but there were significantly fewer live trees in all sections of Forest Park in 2013 as compared to 1993. Our findings suggest important information about tree mortality and recruitment that can help management of the park
The Effect of Urbanization on Breeding Birds, Seedling Growth and Survivorship, and Soil Nitrogen and Carbon
No full textThe second year of bird counts at all my sites in Forest Park was completed; after one additional year, I will be able to determine trends in population numbers over a 20-year time period. The 10-year trends showed interesting findings; I look forward to seeing whether those observed trends have continued into the subsequent decade. The limited study of seedling mortality and growth in the park provided evidence that (1) the tags I put on the seedlings in the summer of 2013 were still intact in 2014 and (2) that tree recruitment (as indicated by the number of new seedlings and saplings) in Forest Park continues to be depressed both in terms of the number of new seedlings and continued high mortality rate of existing seedlings. This became very apparent with the three new control sites, one of which had more seedlings than combined total for the rest of my 25 sites in Forest Park. The final data has yet to be fully analyzed statistically, but I expect interesting significant results.
The soil data has yet to be collected due to issues with my contact at PSU. I am hopeful that we will be able to get the samples analyzed for total nitrogen and carbon using the elemental analyzer this month. The results will be exceptionally interesting (regardless of the actual findings) and will provide us with valuable information
Effect of Urbanization on Soil: Structure, Chemistry, and Mycorrhizael Fungi
No full textTwo students (Tatiana Taylor and Hayden Cooksy) worked with me over the summer. We measured ambient light, soil moisture, soil electroconductivity (ECP), soil temperature, and soil pH along transects at my permanent research sites in Forest Park and at the control sites in the Mount Hood National Forest. At random sites, we dug soil pits to verify soil type and characteristics of each horizon including texture, nutrients, pH, and color. We used an app called “SoilWeb” to verify the soil characteristics and type. In addition, we measured 24 hours CO2 production in twelve containers at random sites to get an indication of soil respiration rates. We also harvested seedlings in order to quantify the amount of ECM (ectomycorrhizae) and AMF (arbuscular mycorrhizae) in the roots.
We found that almost all our sites in Forest Park have “Goble” soil; only two sites had “Wauld.” These two soil types are both Inceptisols found in wooded areas. There were no significant differences among site locations for soil pH, moisture, ECP, texture, or light levels. We did find significantly higher levels of CO2 produced in 24 hours at the control sites in the national forest than at sites in Forest Park. This is in accord with last year’s findings that the national forest sites had deeper O horizons and higher C/N ratios than the sites in Forest Park. The C/N ratio and the depth of the O horizon were both significantly positively correlated with the number of seedlings and saplings, but the level of soil respiration was not correlated with any other measured variables.
We are still analyzing the roots of the collected seedlings for mycorrhizae. When we harvested the plants at the control sites, we saw ectomycorrhizae on the roots. Unfortunately we only found two seedlings in Forest Park, which reinforces the lack of recruitment in the urban forest. We are working to quantify the amounts of ECM and AMF in the roots of the control site seedlings; the two seedlings we collected in Forest Park will probably not yield sufficient data for a comparative analysis
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
The Effect of Urbanization on Forest Mycorrhizae, Worms, and Soil Respiration
No full textIn previous work, I have found that urban forests tend to have few to no saplings compared to more rural forests. In an attempt to determine possible reasons for this finding, two students (William McCuen and Delaney Riggins) helped me examine worms and soil characteristics at my permanent research sites in Forest Park and at the control sites in the Mount Hood National Forest. We collected earthworms at 29 sites using a mustard extraction method, conducting three worm pulls at each site. The worms were returned to the lab where they were counted and weighed. We measured the depth of the O horizon at each earthworm collection location. Invasive earthworms have been shown to increase turnover rate of organic material in the soil, resulting in lower seedling survival. We also collected soil from each of my sites and measured 24-hour CO2 production in twelve containers to determine soil respiration rates. In addition, we harvested seedlings to quantify the amount of ECM (ectomycorrhizae) and AMF (arbuscular mycorrhizae) in the roots, another important factor for seedling survival.
We found the depth of the O horizon and the amount of CO2 were both significantly greater at rural control sites than in the urban forest. The number of worms collected per site ranged from 0 to 52, with a mean of 10.8. Neither the number of worms nor the biomass of worms was significantly different among locations. There was, however, a tendency of lower worm biomass at the control sites, and the depth of the O horizon was negatively correlated with the biomass of worms, although R2 was low. Worms are best collected in early spring, and because we collected worms in June and July, we feel the drier soil and warmer temperatures may have played a role in the absence of worms at some sites. We did find thinner O horizons in areas with a higher biomass of worms, although the relationship was weak. This preliminary study shows a potential negative impact of invasive worms on urban forest soils
Effect of Urbanization on the Avian Community and Tree Seedling Growth and Mortality in an Urban Forest, Forest Park in Portland, Oregon
No full textTwo students (Terran Sobel-Smith and Carli McCormick) worked with me over the summer. We completed three bird counts at each of my sites in Forest Park during the month of June. We collected data on growth, predation, and survival of western red cedar seedlings planted in 2005 at nine conifer recruitment sites in Forest Park. We also measured ambient light, soil moisture, soil electroconductivity (ECP), soil temperature, and soil pH around every seedling in an attempt to examine potential causes for differences in tree response. To determine whether the low number of seedlings in Forest Park was “normal”, we added three control sites in the Mount Hood National Forest above Estacada.
We found significantly more seedlings at the control sites than at any site in Forest Park. We found that seedlings grew significantly better (defined by increased height and basal diameter) in the middle and far sections of Forest Park than in the city section. We also found grazing by deer and elk to be significantly greater in the far section, meaning the reduced growth in the city section was not related to predation. Tree mortality was greatest in the middle section of the park. None of the abiotic factors we examined (e.g., light, soil moisture, soil ECP, soil temperature, and soil pH) correlated with seedling growth or mortality. Our results suggest air pollution may be related to the lack of seedlings in urban forests. Terran, Carli, and I presented our findings at the annual UERC (Urban Ecology Research Consortium) symposium on February 8, 2016 in Portland, Oregon. We are in the process of writing a paper we will submit to Quercus (and perhaps another refereed journal). Terran, Carli, and I will present a poster about our findings at the Linfield College Student Science and Creative Projects Symposium
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