RESEARCH

Video presentation prepared for 2022 Botanical Society of America national meeting describing some results from my work with phenological escape

Conducting a phenology census in Saginaw Forest

(Photo courtesy of Dave Brenner)

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Projected change in spring light window duration for spring-active wildflower species in a) eastern Asian, b) Europe, and c) eastern North America (Lee et al, in review)

Shifts in phenological escape dynamics in response to climate change

 

Many species of understory plants in temperate deciduous forests assimilate up to 80% of their annual carbon budget within the first few weeks of the growing season, prior to canopy closure, a strategy known as phenological escape. Climate change, specifically spring warming, is shifting canopy tree phenology earlier, meaning that understory spring light windows are also shifting. In order to maintain access to this ephemeral resource, spring-active understory plants must therefore shift their phenology at the same or greater rate as the canopy.

During my dissertation, I studied phenological escape dynamics between seedlings and co-occurring canopy trees of two temperate deciduous species: Acer saccharum and Quercus rubra. I found that seedlings were more responsive to spring warming and winter chilling than the adults, suggesting that they are likely to gain access to spring light under climate change conditions. However, I also projected changes in annual carbon assimilation that include effects of hotter and drier summers and found that these seedlings would experience a net reduction in carbon assimilation and performance.

 

I recently expanded this work to examine differences in phenological escape dynamics of herbaceous understory wildflowers across and between continents. Consistent with other studies, we projected a net reduction in access to spring light for North American wildflowers under climate change conditions. However, European and east Asian wildflowers were projected to either maintain or gain access to spring light under warmer springs. This work highlights that phenological responses can differ among continents and that further work is needed to understand the mechanistic underpinnings of this phenomenon.

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Example of a Trillium erectum specimen collected in 1941.

Changes in mycorrhizal community composition across time and space

 

Many temperate forest plant species rely on symbiotic relationships with arbuscular mycorrhizal fungi (AMF), to obtain otherwise-limiting resources such as nitrogen and phosphorous. Recent evidence has suggested that soil microbial communities are affected by climate change, but it is yet unknown how AMF are affected. It is similarly unknown how different AMF community compositions affect the performance of their plant hosts.

For my postdoctoral fellowship work, I am using herbarium specimens collected over the past ~120 years to investigate how AMF community composition differs across time and space (eastern North America). I am collecting root samples from three species of Trillium (T. erectumT. cernuum, and T. luteum) and modeling the response of their AMF communities to climate change and allelopathic invaders (see next section). I am also using field-collected specimens to determine how AMF communities affect plant functional traits such as leaf nitrogen concentrations.

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Jack Hatajik counting the number of flowers, buds, and fruits for an individual Alliaria petiolata at Pymatuning State Forest.

Invasion dynamics of Alliaria petiolata and effects on AMF communities

Garlic mustard (Alliaria petiolata) is an invasive plant originating from Eurasia that is now common across much of the contiguous United States. Previous work found that garlic mustard is allelopathic and produces glucosinolates, which acts to restrict AMF sporulation and can therefore impact AMF interactions with native plant species. However, it is currently a matter of debate as to how much of an effect this has on native plant communities and whether these effects are consistent across time and space. For example, work from Lankau et al. (2009) suggests that allelopathic effects of garlic mustard disappear as a function of time since invasion.

I am working alongside an undergrad from Pitt, Jack Hatajik, to investigate the invasion history of garlic mustard across Pennsylvania and to determine if time since invasion is a good predictor of garlic mustard abundance and performance or native plant community characteristics. I also plan to investigate if and how garlic mustard invasion affects the AMF communities associated with historical Trillium specimens (see above).