Presentation Type
Oral Presentation - Campus Access Only
Category
STEM (science, technology, engineering, mathematics)
Abstract/Artist Statement
Trees are dying prematurely across the globe at alarming rates, often due to drought and/or insects. Insect attacks can range in severity with some tree species surviving (e.g., the American beech and beech bark disease) and some species becoming essentially extinct (e.g., the American chestnut and the chestnut blight). Tree responses may also vary because of genetic differences among “families” of trees (i.e., intraspecific variation). It is thus hard to predict how tree species will respond to insect attacks. To this avail, we examined tree canopy dieback (leaf loss), drought stress, wound healing, and chemical defense responses of 44 families of white ash (Fraxinus americana) from across the species range to a recent emerald ash borer (Agrilus planipennis) outbreak in an arid common garden in Kansas. At our site, white ash families originally from drier, colder areas (northern USA) exhibited more canopy dieback than families from wetter, warmer regions (southern USA). We also found that tree families that were sensitive to drought and/or slower to heal bark wounds were more likely to show canopy dieback. Overall, we are the first to demonstrate significant intraspecific variation in white ash canopy dieback due to emerald ash borer and connect it to temperature and precipitation conditions of original seed sources. If this canopy dieback pattern holds for mortality, southern white ash may be suitable for reintroduction to the American north, where 99% of white ash has already died.
Mentor Name
Joy K. Ward
Personal Statement
Insect attacks are a major driver of tree mortality, and in combination with drought can decimate forests. The emerald ash borer (Agrilus planipennis; EAB) is one of the most ecologically destructive insects in North American history. EAB-induced biomass losses were 1.813 Tg Carbon (C) per year above background levels between 2002 and 2015 (Fei et al. 2019), an emission equivalent to 434,454 more passenger cars on the road (at a fuel economy of 22 mpg and 11,500 mi/year). These ash biomass losses are unsurprising as 99% of infested ash trees die within two years of EAB sightings, and all ash trees will likely be dead within six to fifteen years. Ash mortality is devastating to ecosystems and humanity. Many animals feed on ash trees: Birds and small mammals often feed on ash seed, and beavers, rabbits, and porcupines feed on ash bark. Humans are also affected by ash tree mortality. Ash trees often line streets and provide shade in parks. With EAB-induced mortality on the rise, homeowners and local communities are facing enormous quarantine and removal expenses for infected ash trees. Predicted annual costs to local governments is $1.7 billion, and homeowners are expected to pay $760 million/year (Aukema et al. 2011). Ash also used to be a major source of timber, particularly for baseball bats, but this is no longer the case. There is hope, however, that some ash trees may be less susceptible to EAB (i.e., intraspecific variation) despite limited evidence. While a study in Pennsylvania found that five families of white ash (F. americana) and 57 families of green ash (F. pennsylvanica) varied in EAB attack and canopy dieback (Steiner et al. 2019), others have found no differences (Rebek et al. 2008). This variation is crucial for reforestation efforts. If some families are also less likely to die, these families could be used to reforest areas with significant ash mortality (i.e., northern USA) In the present study, white ash trees originally from drier, colder areas (northern USA) exhibited more canopy dieback than families from wetter, warmer regions (southern USA). We also found that trees less sensitive to drought and/or quicker to heal bark wounds were less likely to die. We suggest that if these dieback patterns hold for mortality, white ash from the southern USA may be suitable for reforestation efforts in the northern USA. Our results are groundbreaking and promising in that ash trees may not go extinct in the USA from EAB invasion as claimed by most literature. We intend to submit this publication to Global Change Biology. In addition to the major publication, this project benefitted me professionally. I became a better scientist; I spent several meetings with my advisor discussing the logical steps needed to create scientific arguments. I also gained significant experience with statistics and data analysis, learning several new analyses and how to code in R. Lastly, and perhaps most significantly, I worked endlessly on fellowship and grant applications. With my advisor’s mentorship, I was awarded an NSF Graduate Research Fellowship ($130k), a University of Kansas Self Graduate Fellowship ($135k), and a University of Kansas research grant ($500). In all, this white ash and EAB project led to groundbreaking findings and I developed tremendously as a scientist in my scientific logic and data analysis skills. References Aukema, J. E., B. Leung, K. Kovacs, C. Chivers, K. O. Britton, J. Englin, S. J. Frankel, et al. 2011. Economic impacts of non-native forest insects in the continental United States. PLoS One 6: e24587. Fei, S., R. S. Morin, C. M. Oswalt, and A. M. Liebhold. 2019. Biomass losses resulting from insect and disease invasions in US forests. Proc Natl Acad Sci U S A 116: 17371-17376. Rebek, E. J., D. A. Herms, and D. R. Smitley. 2008. Interspecific variation in resistence to emerald ash borer (Coleoptera: Buprestidae) among North American and Asian ash (Fraxinus spp.). Environmental Entomology 37: 242-246.
White ash trees (Fraxinus americana) originally from colder, drier areas are more susceptible to emerald ash borer (Agrilus planipennis)
Trees are dying prematurely across the globe at alarming rates, often due to drought and/or insects. Insect attacks can range in severity with some tree species surviving (e.g., the American beech and beech bark disease) and some species becoming essentially extinct (e.g., the American chestnut and the chestnut blight). Tree responses may also vary because of genetic differences among “families” of trees (i.e., intraspecific variation). It is thus hard to predict how tree species will respond to insect attacks. To this avail, we examined tree canopy dieback (leaf loss), drought stress, wound healing, and chemical defense responses of 44 families of white ash (Fraxinus americana) from across the species range to a recent emerald ash borer (Agrilus planipennis) outbreak in an arid common garden in Kansas. At our site, white ash families originally from drier, colder areas (northern USA) exhibited more canopy dieback than families from wetter, warmer regions (southern USA). We also found that tree families that were sensitive to drought and/or slower to heal bark wounds were more likely to show canopy dieback. Overall, we are the first to demonstrate significant intraspecific variation in white ash canopy dieback due to emerald ash borer and connect it to temperature and precipitation conditions of original seed sources. If this canopy dieback pattern holds for mortality, southern white ash may be suitable for reintroduction to the American north, where 99% of white ash has already died.