2017 Undergraduate Research Fellows

Meet the 2017 Undergraduate Research Fellows, check out their blog posts, and stop by later in the summer to view this year's Center for Tree Science - Undergraduate Research Symposium. We would like to thank Morton Salt, Inc. for their generous contribution to the 2017 fellowship program; other funding as noted.

 

2017 Research Fellow Amy Bryne in front of a beautiful Wintergreen Korean Boxwood shrub

Amy Byrne

University of Illinois at Urbana-Champaign

Title: Diversity mechanisms shape first year survivorship in a phylogenetic and functional diversity prairie restoration experiment

Advisor: Dr. Andrew Hipp

Funding provided by: National Science Foundation - Research Experiences for Undergraduates

Amy's Blog Posts

Abstract: Prairie restoration is an important tool for improving the ecosystem and the sustainability of a large, diverse group of animals, insects and plants. It has been hypothesized that phylogenetic and functional trait diversity may lead to more highly functioning and sustainable restored communities. This study investigated the effects of phylogenetic, trait and species diversity on survivorship of plugs planted approximately one year after establishing a prairie restoration experiment at The Morton Arboretum (Lisle, IL, U.S.A). We hypothesized that the level of phylogenetic diversity would correlate positively with plug survival but functional trait diversity would correlate negatively. The experiment comprised 326 4-m2 prairie plots of either 1 or 15 species each, drawn from a candidate set of 127 species. Plots ranged in phylogenetic diversity (high, medium, and low) and functional trait diversity (high, low) in a fully factorial experiment with six replicates in each of two super-blocks, for a total of 72 treatment plots. Species were planted as monocultures in each of the two super-blocks, for a total of 254 monocultures, which we used to tease out the effects of species selection and complementarity on diversity effects. Plants were rated at four levels (from dead to full health) based on physical appearance in both monocultures and treatment plots. Mean survivorship was then assessed at the plot level as a function of abiotic factors (soils); block; and trait, phylogenetic, and species  diversity (by comparison of expectation based on monocultures and observed survivorship in treatment plots).  A significant diversity effect was detected between blocks, but not among levels of phylogenetic and trait diversity. The significant diversity effect, however, suggests that species diversity has an effect on survivorship. Moreover, partitioning the diversity effect suggests that it is driven by species complementarity rather than species selection (increased probability of picking up a highly-performing species with higher species diversity). Stochastic factors such as, environmental fluctuations, soil quality or human interference may explain the observed differences between super-blocks. It remains to be seen whether the phylogenetic and functional diversity of plants in the experiment will explain restoration outcomes in future years. If so, the experiment will help us to understand the mechanisms underlying restoration success and sustainability, and thus, assist in making more successful restorations.

 

2017 Research Fellow Sara Desmond in front of a beautiful Wintergreen Korean Boxwood shrub

Sara Desmond

University of Illinois at Urbana-Champaign 

Title:  Latitude predicts leaf size in bur oak (Quercus macrocarpa)

Advisor: Dr. Andrew Hipp

Funding provided by: The Morton Arboretum Center for Tree Science

Sara's Blog Posts

Abstract: There are many factors that contribute to variation in leaf morphology in Quercus macrocarpa (bur oak), however little is known regarding the relative contributions of these factors to the total variation in leaf morphology. At the same time, leaf morphology influences several important plant functions such as water use efficiency, drought resistance, and freezing tolerance; therefore predicting which factors affect leaf morphology can help us determine how important leaf functions will change in response to a changing climate. This study examined the relative contributions of within-tree, among-tree, and among-site variation to the total variation in leaf morphology in bur oak trees, as well as the effects of varying climates and latitudes on specific leaf traits. This study also aimed to determine whether we can predict variation in leaf morphology based on latitude and climate. Samples were collected from five sites each at northern, central, and southern latitudes of the bur oak range. Ten leaf traits and seven ratios were measured using ImageJ and statistical analyses were conducted in R. Climate data was gathered from WorldClim database. Leaf blade length and leaf area were the most responsive traits to changes in latitude. Latitude and climate predict 73% of the variance in leaf morphology. The effect of site (F = 42.544) on total leaf morphology is greater than the effect of tree (F = 6.334), however both are significant.  The results of this study can improve current sampling methods, advance our understanding of  factors affecting leaf morphology, and help to determine if leaf morphology is an adaptive quality.

 

2017 Research Fellow Alyssa Gao in front of a beautiful Wintergreen Korean Boxwood shrub

Alyssa Gao

Dartmouth College

Title: Examining the Effects of Bacterial Leaf Scorch on the Leaves of Quercus mongolica trees within The Morton Arboretum Collection

Advisor: Dr. Chuck Cannon

Funding provided by: Morton Salt, Inc. and The Morton Arboretum Center for Tree Science

Alyssa's Blog Posts

Abstract: Understanding the physiology of trees and how they are affected by factors like disease is a critical component in assessing the ecosystem processes we rely on. Nutrients, which are essential for plant growth and survival, enter the plants through the roots and are transported to the leaves of plants via the upward flow through the xylem. Diseases, such as bacterial leaf scorch (BLS) infect these water and nutrient conducting tissues in trees and threaten their health. The economic and aesthetic value is also compromised, particularly in urban environments. My project examined whether the leaves of Mongolian Oaks affected by BLS differ substantially from the leaves of healthy Mongolian Oaks. To diagnose trees, I collected four twig cookies, one from each cardinal direction, from eleven trees across the Morton Arboretum. I also collected leaf samples from these branches and measured moisture content, leaf area, and foliar nitrogen. I hypothesized that leaves from the unhealthy Mongolian Oaks would have lower moisture content than leaves from the healthy oaks. I also predicted that the amount of N absorbed by the leaves of the unhealthy Mongolian Oaks will be lower than the amount of N present in leaves from the healthy oaks. Comparing leaf morphological traits between diseased trees and healthy trees will provide insight into the physiological responses of urban trees to decline and improve our ability to diagnose trees in the future.

 

2017 Research Fellow Taskeen Khan in front of a beautiful Wintergreen Korean Boxwood shrub

Taskeen Khan

University of Illinois at Urbana-Champaign

Title: The Impact of Injury on Sap Flow in Quercus palustris 

Advisor: Dr. Chuck Cannon

Funding provided by: Morton Salt, Inc. and The Morton Arboretum Center for Tree Science

Taskeen's Blog Posts

Abstract:  Understanding the physiology of trees and how they respond to injury is key to providing trees beneficial post-injury care, such as pruning. Trees respond to injury by compartmentalizing the affected area. Post-injury compartmentalization may also result in changes in sapwood, and therefore potentially sap flow. Sap flow is the movement of water and nutrients from a tree’s roots to its canopy through the xylem. It is vital to providing leaves with the nutrients they need to function. Sap flow is influenced by factors including air temperature, soil moisture, soil temperature, and humidity. Transpiration drives sap flow and follows diurnal patterns. We studied sap flow in Pin oaks before and after an injury. The injuries extended from the bark to heart wood, preventing sap flow through them. We used four SFM1 Sap Flow Meters positioned at different locations on the stem in relation to the injury to compare sap flow rates before and after the injury. These results will provide a better understanding of the extent of the injury’s impact on sapwood, compartmentalization, and directionality of sap flow. The results indicate that sap flow decreases immediately above an injury, but is not greatly impacted to the side of the injury or 90 degrees from the injury. Long term study is needed to understand how compartmentalization and recovery influence sap flow.

 

2017 Research Fellow Sierra Lopezalles in front of a beautiful Wintergreen Korean Boxwood shrub

Sierra Lopezalles

California Institute of Technology

Title: Effects of prescribed burn regime on the growth of mature trees in Midwest oak forests

Advisor: Dr. Christy Rollinson

Funding provided by: Morton Salt, Inc. and The Morton Arboretum Center for Tree Science

Sierra's Blog Posts

Abstract: Controlled burning is a common management technique used in eastern deciduous forests to control invasive understory plants and promote oak regeneration. Though there is much evidence showing that prescribed burns increase oak recruitment, studies have yet to clearly define how burning affects the already established trees. We evaluated the growth rates of mature trees in response to varying fire regimes over a 15 year period in order to determine the long term effects of prescribed burns. We found that all species of oaks (Quercus spp.), as well as sugar maples (Acer saccharum) showed a decline in growth following prescribed burns. Tilia (Tilia americana) were the only species that responded to fire with any increase in growth. Overall, we found that controlled burns caused a decrease in growth rates. These results show that fire can have negative effects on the growth of mature trees, which is important to consider when predicting the benefits of prescribed burning. A better understanding of how forests respond to fire will allow for better management practices and healthier forests. 

 

2017 Research Fellow Katie McGee in front of a beautiful Wintergreen Korean Boxwood shrub

Kathryn (Katie) McGee

James Madison University

Title: The Effect of Prescribed Fire Regimes on Seedling Regeneration and Nitrogen Dynamics in an Oak Forest

Advisor: Dr. Silvia Alvarez Clare

Funding provided by: Morton Salt, Inc. and The Morton Arboretum Center for Tree Science

Katie's Blog Posts

Abstract: Fire is a common management tool used to encourage oak regeneration throughout the Midwestern and Eastern United States. However, we do not fully understand how fire induced changes in the biogeochemical cycles affect the tree community within oak-dominated forests. The goal of this study was to determine how available soil nitrogen (N) within different fire management regimes affected seedling populations and foliar carbon (C) and N ratios in adult trees. We found that annual burning significantly reduced soil N availability by lowering total inorganic N levels and lowering both mineralization and nitrification rates. After one recent burn, N mineralization and nitrification rates were not significantly different from areas rarely burned; however, total inorganic N was higher in the recent burn area than both rarely burned and annually burned. Foliar N and C:N ratio, were not significantly affected by burn treatment across all species tested. Foliar C:N ratio did have a significant negative relationship with soil N mineralization due to the slight increase in foliar percent N with mineralization; however, this relationship was not visible at the burn treatment level. In addition, we found the seedling population of the fire-intolerant species Acer saccharum was nearly absent with annual burning, present but weak after one recent burn, and dominant in areas rarely burned. Oaks, (Quercus spp.), had the highest population in the annual burns. Our findings show that different fire management regimes affect multiple aspects of oak-forests through both N cycling as well as altering seedling populations.

 

2017 Research Fellow Samantha Panock in front of a beautiful Wintergreen Korean Boxwood shrub

Samantha Panock

Loyola University Chicago

Title: Uncovering belowground properties of urban forests: The relationship between root systems, soil characteristics, and fungal communities in deciduous and evergreen trees at The Morton Arboretum

Advisor: Dr. Meghan Midgley

Funding provided by: Morton Salt, Inc. and The Morton Arboretum Center for Tree Science

Samantha's Blog Posts

Abstract: For the summer of 2017, the soil ecology department in the Center of Tree Science at The Morton Arboretum in Lisle, IL, attempted to take a phylogenetic approach to characterize variations in tree root effects on soil biogeochemistry. The research project was conducted within the Undergraduate Research Fellowship program. The objective of this study was to evaluate relationships between root traits and soil functions, to assess whether these traits and functions vary between trees with different leaf habits (deciduous vs. evergreen) and root fungal associations (arbuscular (AM) vs. ectomycorrhizal fungi (ECM)), and to determine if the effects of roots on soils are altered by leaf litter inputs. We hypothesized that variation in root and microbial traits would predict differences in the magnitudes of rhizosphere effects on soil biogeochemistry. These traits and effects would be tightly linked to tree phylogeny, and leaf litter effects on soil organic matter properties would mediate root and microbial traits. A total of eight tree species were selected and divided into four categories (ECM deciduous, ECM evergreen, AM deciduous, and AM evergreen) in order to compare and contrast the data across our multiple variables. Furthermore, each tree species had three collection locations (meaning absence of leaf litter) and three forestry locations (presence of leaf litter) in order to assess the contributions of leaf litter as well. The null hypothesis was rejected. Rhizosphere effects tended to have an inverse relationship to bulk soil properties. Root exudates were greater in evergreen trees than deciduous. Moreover, root exudates were greater for AM fungal communities in collection locations, whereas ECM fungal communities had higher root exudates in the forestry plot locations. Enzyme activity also differed in relationship to leaf type and fungal community, but did not show observational differences in relationship to leaf litter presence or absence. This research is a critical contribution to the understanding of root and soil relationships. Underground processes are important indicators of ecosystem health and adaptation capabilities of ecosystems.