Fall 2022 CURE class project of MCC BIO 105 'Urban tree disparities in Mesa, Arizona'
Urban trees provide a number of ecological, economic, and social benefits. Trees provide shade, which is in short supply in the urban desert environment of Mesa, Arizona. They also filter air and water pollutants and reduce the effect of the urban heat island through evapotranspiration. Increased urban tree cover has been associated with greater mental and physical health among residents of cities, and even a reduction in crime. Studies have demonstrated racial and economic disparities in urban tree cover, with fewer trees present in parks and along streets in neighborhoods with low socioeconomic status (SES). For this project, researchers quantified urban trees along streets in 12 neighborhoods in Mesa, Arizona. Four of the neighborhoods had a median household income up to 150% of the federal poverty level (low income), four had a median household between 200% and 300% of the federal poverty level (high-middle income), and four neighborhoods had a median household income above 300% of the federal poverty level (high income). Researchers used Google Earth to perform virtual tree surveys along a 1-km stretch of road in each neighborhood, counting the number of trees planted near the road. There was a positive correlation between median household income and number of trees/km. However, the wealthiest neighborhood had a disproportionately high number of trees compared to the others. The correlation was much weaker when this outlier was removed. Further research in more neighborhoods will help determine the strength of the relationship between wealth and tree cover in Mesa neighborhoods.
Coleman, L. and Grimes, A. Ecosystem Services Provided by Mesa Community College Arboretum Trees
We performed this study to quantify ecosystem services provided for the trees at the Mesa Community College (MCC) Arboretum. This preliminary study surveyed 1129 trees, belonging to 99 unique taxa out of the estimated 1200 trees in the arboretum. The total height and diameter at breast height (DBH) were measured for each tree between 2017 and 2020. This data was analyzed using the i-Tree Eco program from the U.S. Forest Service. Ecosystem services reported include air pollutant removal, carbon storage and sequestration, oxygen production, and avoided stormwater runoff. The arboretum trees remove 185 kg of air pollutants per year. The pollutants reported include carbon monoxide (CO), nitrogen dioxide (NO2), ozone (O3), particulate matter <2.5 µm (PM2.5), and sulfur dioxide (SO2). The trees store 219.2 metric tons of carbon and sequester an additional 9.973 metric tons of carbon per year. The trees divert 153.2 m3 of stormwater per year. The replacement value of the MCC Arboretum trees is estimated to be $2.1 million. The ecosystem services quantified in this study will be used to guide planting decisions in the future as the MCC Arboretum develops.
Coleman, J. Analysis of the Impact of Campus Landscaping on Building Energy Efficiency
A large share of the energy used in buildings is dedicated to running air conditioning and heating systems. This energy use can be reduced by strategic placement of shade trees and other plants on the exterior of the buildings. This study will investigate the current energy use in a set of buildings on the Mesa Community College Southern and Dobson campus and will analyze how current landscaped plants affect the energy use in these buildings. Recommendations for new strategic plantings of trees and shrubs will be made.
Johnson ML - The Effects of Arbuscular Mycorrhizal Inoculant on Corn Growth
Arbuscular mycorrhizal fungi (AMF) live in a mutualistic symbiotic relationship with plants. The fungal partner colonizes the root cells of the plant host and provides numerous benefits by acquiring water and soil nutrients that are otherwise unavailable to the plant. In return, the plant provides the fungus with the sugars it requires for survival. The benefits of AMF to plants in natural and agricultural settings are well-documented, and several commercial inoculants are available as soil amendments to improve plant growth. We tested whether one of these commercial preparations, Mykos Mycorrhizal Inoculant from Xtreme Gardening, would improve the growth of corn in a greenhouse setting. Corn plants were grown in either unsterilized soil, sterilized soil, or sterilized soil with added Mykos inoculant (8 plants in each group). The height and dry weight of each plant was recorded after 6 weeks of growth. Root staining revealed that AMF colonization was present in the unsterilized and inoculated group, but absent in the sterilized group. On average, the plants in the unsterilized soil grew taller and weighed more than the sterilized + inoculated plants. However, plants in the sterilized soil were taller and more massive than the other two groups. We were able to confirm the presence of AMF in the inoculant, but it did not have a positive effect on plant growth. The presence of AMF inoculant actually hindered plant growth in this case.
Buchert S. - Population Genetics of Feral Cats on a College Campus
Mesa Community College is home to a small colony of feral cats (Felis domesticus). It is unknown whether the cats are all closely related or have immigrated to the campus from disparate populations. This study compared DNA sequences from the D-loop region of the mitochondria from 11 campus cats and one cat from a separate population in Phoenix, Arizona. A sequence from the sand cat (F. margarita), the closest relative of domestic cats, was used as an outgroup. D-loop sequences are highly variable and are useful in studying genetic differences at the population level, but are not able to resolve individual familial relationships. The campus cats were found to belong to four distinct populations, but they were all more similar to each other than to the cat from the Phoenix population. This indicates that MCC’s feral cats are somewhat closely related but are derived from distinct populations.
Nieveras, M. Diversity of Trees on the Mesa Community College Campus
Urban trees provide a number of economic, social, and ecological benefits. Studies have shown that these benefits increase as species diversity increases. This study was conducted to quantify the diversity of trees on the Mesa Community College Southern and Dobson campus. All individual trees on the campus were identified to species, recorded in a plant database, and mapped using GIS software. As of the time of the survey (Summer 2016), the campus was home to 1241 individual trees, belonging to 97 species in 24 plant families. The most common species was escarpment live oak (Quercus fusiformis). There were 20 species represented by only a single individual tree. This work will inform future decisions about tree selection and placement on the MCC campus.
Shade Tree Effects on Campus Energy Use: An Ecosystem Services Analysis
Building energy use in the Phoenix metropolitan area is greatly impacted by extreme radiant heat due to the urban heat island effect and limited green space. Urban trees provide a number of environmental and economic benefits, including a reduction in energy use for heating and cooling of buildings. Students at Mesa Community College have worked with the campus arboretum to collect measurements of the height and diameter at breast height (DBH) of campus trees for use in the analysis of campus sustainability. The authors contributed to this data set using standard field measurement tools and methods. In this study, the tree data were used to estimate the impact of tree shade on building energy use. We used ArcGIS to calculate the distance and direction from 470 trees to the nearest 44 campus buildings, for a maximum of three vectors per tree. We then used the open-source software package iTree Eco to model the interactions between trees and buildings. We will present the impact of tree shade on building energy use (MBTU and Mwh), effects on carbon emitted from energy generation, and the economic value associated with these changes.
