This page has an overview of the five main research focal areas of my earlier career and a brief mention of their significance. It also includes a brief discussion of my most recent research. I also posted a blog that tells a story of my early research career). This is a PowerPoint presentation of my research career.
Biogeochemical cycling of mercury
My most recent research grants focus on the biogeochemical cycling of mercury in response to different silvicultural practices aimed at restoring longleaf pine ecosystems. You can see a narrated PowerPoint of our May 2022 presentation “How does mercury methylation respond to intensive forest management and the creation of anoxia in floodplain soils?” . Also see our first peer reviewed paper: here
This research team in my lab is actually led by a former UNCG professor, Martin Tsz-Ki.Tsui who left for the School of Life Sciences, The Chinese University of Hong Kong. Other members of the team we have worked with since I became PI Alex Chow, Carl Tretting, Yener Ulus and me. Earlier in my career, I was part of a team that used the mass balance capability of the EcoCELLs to trace the flux of mercury demonstrating that most mercury enters the ecosystem through leaf fall and on direct atmospheric deposition to soils (with Mae Gustin and Steve Lindbergh; see a key paper here that showed that litterfall may be the major way that mercury enters an ecosystem).
Bottom up control of herbivory: soil microplastics and plant insect interactions.
Undergraduates in my laboratory the last two years (and now) have been working on the effect of soil microplastics on the interactions between tobacco plants and the tobacco hornworm. We have trends that that suggest that tobacco hornworms that can detect plants grown in soils amended with microplastics vs controls and that the hornworms grow more slowly on plants grown in soil with microplastics. Our work has also shows an affect on the timing of seed germination in soils amended with microplastic vs. controls. We are continuing to repeat the experiment. Here is a recent undergraduate poster
Olivia Kjuka, an MS student advised by me and Dr. Kim Komatsu is starting an MS thesis project in Spring 2025 where she will examine the question of whether tri-trophic interactions between a plant (soybean), an herbivore (Mexican bean beetle) and a parasitic tachinid fly will be affected by growing soybeans in soil amended with mircroplastics vs controls. Undergraduates will be working with her for tall of 2025
Ecotypic variation in longleaf pine and its relevance to the restoration of long leaf pine stands.
Jordan Winter, a PhD student advised by me and Dr. Sally Koerner. His dissertation His dissertation research is exploring ecotypic variation in seedlings of longleaf pine (Pinus palustris), and its potential to improve restoration efforts. His original research aims are: 1) . Identify the current state of ecotypic and cultivar restorative research in the literature.; 2) Determine if the ecotypes of longleaf pine trees differ across their range, or simply
respond through phenotypic plasticity in response the various climates; 3) Explore the effect of drought and nutrient deposition on longleaf pine restorative ecotypes; and 4) Explore the effect of saltwater and freshwater inundation and saltwater intrusion on longleaf pine restorative ecotypes. Undergraduate students will be working with him in Spring 2025, particularly on the saltwater intrusion experiment.
How leaf and plant development affect leaf biochemistry and susceptibility to insects and pathogens.
Using eastern cottonwood as a model system, we (Clive Jones, Bill Smith (Yale) and I) integrated the tremendous work of Phil Larson, Richard Dickson and Jud Isebrands who detailed the synchrony of form and function in eastern cottonwood seedlings, cuttings and trees, including mapping the vasculature system and clearly showing the physiological, biochemical and anatomical changes that occur a leaf moves through it sink to source transition and then ages. We used this basic understanding to demonstrate the ability of leaf beetles, caterpillars and aphids to track leaf development age, and we demonstrated how the strength of vascular connections between different leaves strongly influenced whether an undamaged leaf would induce defensive chemicals when another leaf was damaged. We used the knowledge of form and function relationships to examine whether environmental stress (using ozone as a model stress), changes plant chemistry and leaf development in such a way that it would change the susceptibility of plants to four different “pests” that feed in different ways and thus change the dynamics of the of insect and fungal pathogen community. We studied a leaf beetle that eats leaf tissue; an aphid that draws phloem fluid, a rust fungus which feeds from living cells, and a leaf spot fungus that only feed after cells have been killed. These data led Clive Jones and I to create what we called a “phytocentric perspective” of plant responses herbivores. I am currently revising a draft paper that describes a link between leaf development with patterns and phenology of leaf production in trees (indeterminate vs. determinate) to life history and ecological traits of herbivores and pathogens in their community, such as the likelihood of having insects with multiple generations/yr or those that experience boom or bust outbreaks. We also determined that it matters a great deal whether insects feed on the tip or the base of an expanding leaf with respect to interpreting how much biomass was eaten by the area of missing tissues- damage on the tip of expanding leaves will end up being around 10x the actual amount eaten, whereas damage to the base will results in roughly equal damage and estimates of amount eaten
How plants allocate carbon and nutrients to roots, shoots, storage and reproduction in response to environmental stress.
We (Kelly McConnaughay and I) examined the importance of plant development and size dependency in interpreting whether adjustments in resource allocation (e.g., root:shoot ratio; N concentration in tissues) in plants to stressful environments follows the hypotheses of optimal partitioning, ontogenetic drift, or both. We tested whether data that supported optimal partitioning resulted from comparing traits of plants at a common age as opposed to at a common size. Plants often develop as a function of their size, and not necessarily their age. Therefore, if one compares plant traits at a common time of a control vs. a stressed plant, then one will be measuring plants of different sizes because the control plant is likely to be bigger than the stressed plant. In such cases, any differences demonstrated in plant traits for plants of different sizes could be due to ontogenetic drift (the allometric relationships between different plant parts as a plant gets bigger), and not necessarily due to adaptive strategies of plants in response to stress.
The role of low molecular weight heat shock proteins in protecting plants from heat stress and their evolutionary ecology.
We (Scott Heckathorn, Craig Downs, and Tom Sharkey) were the first laboratory to demonstrate that low molecular weight chloroplast heat shock proteins protect photosystem II from heat stress. We started this work by examining the physiological cost to plants of making heat shock proteins, and whether that cost helps shape the pattern and amount of heat shock proteins produced by a single species within populations that are more or less adapted to experience acute heat stress. We also examined whether such differences correlated with the environment in which different species evolved. We also demonstrated that there is resource cost (particularly N) to making low and high molecular weight heat shock proteins.
How plants and ecosystems respond to rising carbon dioxide levels along with changing precipitation and deposition of nutrients and pollutants associated with climate change.
The Desert FACE (Free-air CO2 enrichment) site, taught us (the main PIs were me, Stan Smith, Jeff Seemann, Bob Nowak, Jay Arnone, Yiqi Luo, Wexin Cheng, Paul Verburg, Dani Obrist, Tim Ball, Dave Evans and Dale Johnson) a great deal about how elevated carbon dioxide affects photosynthesis, ecosystem productivity, carbon cycling and carbon storage, invasive species, soil water and water use efficiency, and the role of the microbial crust that covers the desert floor. Laboratory experiments taught us a lot about closing the carbon cycle, the response of net ecosystem productivity over several years in response to one unusually warmer year, and the full carbon, nutrient and water fluxes and storage of ecosystems in response to elevated carbon dioxide using a nationally unique large mass balance mesocosm facility (EcoCELLs) (https://www.youtube.com/watch?v=j_nYbGfU20c). The EcoCell work on the lagged response of soil respiration to an anomalously warm year was on the cover of Nature in 2008.)
Biogeochemical cycling of mercury
My most recent research grants focus on the biogeochemical cycling of mercury in response to different silvicultural practices aimed at restoring longleaf pine ecosystems. You can see a narrated PowerPoint of our May 2022 presentation “How does mercury methylation respond to intensive forest management and the creation of anoxia in floodplain soils?” . Also see our first peer reviewed paper: here
This research team in my lab is actually led by a former UNCG professor, Martin Tsz-Ki.Tsui who left for the School of Life Sciences, The Chinese University of Hong Kong. Other members of the team we have worked with since I became PI Alex Chow, Carl Tretting, Yener Ulus and me. Earlier in my career, I was part of a team that used the mass balance capability of the EcoCELLs to trace the flux of mercury demonstrating that most mercury enters the ecosystem through leaf fall and on direct atmospheric deposition to soils (with Mae Gustin and Steve Lindbergh; see a key paper here that showed that litterfall may be the major way that mercury enters an ecosystem).
Bottom up control of herbivory: soil microplastics and plant insect interactions.
Undergraduates in my laboratory the last two years (and now) have been working on the effect of soil microplastics on the interactions between tobacco plants and the tobacco hornworm. We have trends that that suggest that tobacco hornworms that can detect plants grown in soils amended with microplastics vs controls and that the hornworms grow more slowly on plants grown in soil with microplastics. Our work has also shows an affect on the timing of seed germination in soils amended with microplastic vs. controls. We are continuing to repeat the experiment. Here is a recent undergraduate poster
Olivia Kjuka, an MS student advised by me and Dr. Kim Komatsu is starting an MS thesis project in Spring 2025 where she will examine the question of whether tri-trophic interactions between a plant (soybean), an herbivore (Mexican bean beetle) and a parasitic tachinid fly will be affected by growing soybeans in soil amended with mircroplastics vs controls. Undergraduates will be working with her for tall of 2025
Ecotypic variation in longleaf pine and its relevance to the restoration of long leaf pine stands.
Jordan Winter, a PhD student advised by me and Dr. Sally Koerner. His dissertation His dissertation research is exploring ecotypic variation in seedlings of longleaf pine (Pinus palustris), and its potential to improve restoration efforts. His original research aims are: 1) . Identify the current state of ecotypic and cultivar restorative research in the literature.; 2) Determine if the ecotypes of longleaf pine trees differ across their range, or simply
respond through phenotypic plasticity in response the various climates; 3) Explore the effect of drought and nutrient deposition on longleaf pine restorative ecotypes; and 4) Explore the effect of saltwater and freshwater inundation and saltwater intrusion on longleaf pine restorative ecotypes. Undergraduate students will be working with him in Spring 2025, particularly on the saltwater intrusion experiment.
How leaf and plant development affect leaf biochemistry and susceptibility to insects and pathogens.
Using eastern cottonwood as a model system, we (Clive Jones, Bill Smith (Yale) and I) integrated the tremendous work of Phil Larson, Richard Dickson and Jud Isebrands who detailed the synchrony of form and function in eastern cottonwood seedlings, cuttings and trees, including mapping the vasculature system and clearly showing the physiological, biochemical and anatomical changes that occur a leaf moves through it sink to source transition and then ages. We used this basic understanding to demonstrate the ability of leaf beetles, caterpillars and aphids to track leaf development age, and we demonstrated how the strength of vascular connections between different leaves strongly influenced whether an undamaged leaf would induce defensive chemicals when another leaf was damaged. We used the knowledge of form and function relationships to examine whether environmental stress (using ozone as a model stress), changes plant chemistry and leaf development in such a way that it would change the susceptibility of plants to four different “pests” that feed in different ways and thus change the dynamics of the of insect and fungal pathogen community. We studied a leaf beetle that eats leaf tissue; an aphid that draws phloem fluid, a rust fungus which feeds from living cells, and a leaf spot fungus that only feed after cells have been killed. These data led Clive Jones and I to create what we called a “phytocentric perspective” of plant responses herbivores. I am currently revising a draft paper that describes a link between leaf development with patterns and phenology of leaf production in trees (indeterminate vs. determinate) to life history and ecological traits of herbivores and pathogens in their community, such as the likelihood of having insects with multiple generations/yr or those that experience boom or bust outbreaks. We also determined that it matters a great deal whether insects feed on the tip or the base of an expanding leaf with respect to interpreting how much biomass was eaten by the area of missing tissues- damage on the tip of expanding leaves will end up being around 10x the actual amount eaten, whereas damage to the base will results in roughly equal damage and estimates of amount eaten
How plants allocate carbon and nutrients to roots, shoots, storage and reproduction in response to environmental stress.
We (Kelly McConnaughay and I) examined the importance of plant development and size dependency in interpreting whether adjustments in resource allocation (e.g., root:shoot ratio; N concentration in tissues) in plants to stressful environments follows the hypotheses of optimal partitioning, ontogenetic drift, or both. We tested whether data that supported optimal partitioning resulted from comparing traits of plants at a common age as opposed to at a common size. Plants often develop as a function of their size, and not necessarily their age. Therefore, if one compares plant traits at a common time of a control vs. a stressed plant, then one will be measuring plants of different sizes because the control plant is likely to be bigger than the stressed plant. In such cases, any differences demonstrated in plant traits for plants of different sizes could be due to ontogenetic drift (the allometric relationships between different plant parts as a plant gets bigger), and not necessarily due to adaptive strategies of plants in response to stress.
The role of low molecular weight heat shock proteins in protecting plants from heat stress and their evolutionary ecology.
We (Scott Heckathorn, Craig Downs, and Tom Sharkey) were the first laboratory to demonstrate that low molecular weight chloroplast heat shock proteins protect photosystem II from heat stress. We started this work by examining the physiological cost to plants of making heat shock proteins, and whether that cost helps shape the pattern and amount of heat shock proteins produced by a single species within populations that are more or less adapted to experience acute heat stress. We also examined whether such differences correlated with the environment in which different species evolved. We also demonstrated that there is resource cost (particularly N) to making low and high molecular weight heat shock proteins.
How plants and ecosystems respond to rising carbon dioxide levels along with changing precipitation and deposition of nutrients and pollutants associated with climate change.
The Desert FACE (Free-air CO2 enrichment) site, taught us (the main PIs were me, Stan Smith, Jeff Seemann, Bob Nowak, Jay Arnone, Yiqi Luo, Wexin Cheng, Paul Verburg, Dani Obrist, Tim Ball, Dave Evans and Dale Johnson) a great deal about how elevated carbon dioxide affects photosynthesis, ecosystem productivity, carbon cycling and carbon storage, invasive species, soil water and water use efficiency, and the role of the microbial crust that covers the desert floor. Laboratory experiments taught us a lot about closing the carbon cycle, the response of net ecosystem productivity over several years in response to one unusually warmer year, and the full carbon, nutrient and water fluxes and storage of ecosystems in response to elevated carbon dioxide using a nationally unique large mass balance mesocosm facility (EcoCELLs) (https://www.youtube.com/watch?v=j_nYbGfU20c). The EcoCell work on the lagged response of soil respiration to an anomalously warm year was on the cover of Nature in 2008.)