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Hot-drought effects on European trees.
Hot-drought effects on European trees.
Alongside rising temperatures and evaporative demand, Europe is experiencing an increasing frequency of hot–drought events, necessitating a clearer understanding of how forests acclimate to these shifting climate regimes. Across a set of long-term experimental systems, this work examines how heat and drought interact to constrain transpiration, alter leaf thermoregulation, and reshape hydraulic function and thermal vulnerability.
At the Model Ecosystem Facility, a five-year manipulation of air temperature and soil moisture using open-top chambers in Fagus sylvatica and Quercus pubescens provides insight into long-term acclimation to combined stress. Results show that soil drought is a primary driver of thermoregulatory breakdown. By limiting transpiration, it reduces evaporative cooling and leads to breachingof leaf thermal safety margins, which is directly associated with leaf scorching under hot–drought conditions.
Long-term in situ rainfall exclusion experiments in natural Quercus ilex forests across Europe examine how chronic soil drought alters water use, stomatal sensitivity, hydraulic traits, and thermal tolerance in situ. At Pfynwald, a similar experiment in Pinus sylvestris combines rainfall exclusion, irrigation, and a novel manipulation of vapour pressure deficit (VPD), enabling us to disentangle atmospheric- versus soil-drought effects on plant water relations, thermoregulation, and heat vulnerability under field conditions.
Together, these approaches provide a mechanistic framework for understanding how hydraulic constraints and tradeoffs mediate forest responses to ever warmer and drier conditions.
Heat tolerance and trait acclimation in urban trees.
Heat tolerance and trait acclimation in urban trees.
Using the urban heat island effect in Miami, Florida as a 'found experiment' to simulate the effects of climate change, we investigate acclimation to elevated temperatures in urban street trees.
So far, we have found very limited acclimation of thermoregulatory traits and thermal tolerances in our species, but perhaps a greater ability to acclimate in species that are adapted to greater seasonality (i.e., species from higher latitudes). Read more in our publication in Tree Physiology!
Despite a weak acclimation response and consequently low leaf thermal safety margins at high temperatures, we also didn't find any increases in the thermal optimum of photosynthesis in hotter areas of the city. It's likely that this lack of acclimation response of net photosynthesis is due to stomatal limitation. Read more in our publication in Plant, Cell & Environment!
We're also interested in how Miami's 250+ tree species will fare with future climate warming so that we can create an informed plan for the future of our urban tree community. We've found that by the end of the century, climate warming may make Miami inhospitable to many of the street trees we currently utilize, including live oak and cabbage palm. Native tree species will be disproportionately impacted by warming compared to exotic trees. See our paper in Urban Forestry & Urban Greening for more details.
Acclimation of trees to elevated temperatures in the Amazon.
Acclimation of trees to elevated temperatures in the Amazon.
Rapid warming in the lowland tropics is generating novel climatic conditions, particularly in the Amazon rainforest, where environmental conditions are shifting beyond historical bounds and future responses of tree communities remain difficult to predict. To address this, I work at the Boiling River in Peru, where geothermally heated waters create extreme thermal gradients over very short distances: maximum air temperatures differ by as much as 11 °C over just 0.5 km. This system provides a rare natural experiment for examining how tropical forests respond to sustained, high-temperature conditions that are otherwise difficult to study in situ.
Using this gradient, our research integrates ecophysiology and community dynamics to understand how trees respond to elevated temperatures. So far, we have documented coordinated shifts in leaf functional traits along the thermal gradient, demonstrated seasonal acclimation of thermal tolerance, and shown declines in tree diversity as well as increasing relative abundance of heat-loving species with increasing temperature. Together, these results point to both physiological limits and ecological reorganization in the Amazon under extreme heat.
Ongoing work at the site continues to expand on these themes, including efforts to link thermal environments to carbon balance, species interactions, and more.
This research has also been featured in Science Magazine, Mongabay, BBC Futures, New Phytologist.
Tree diversity in Sierra Nevada de Santa Marta, Colombia.
Tree diversity in Sierra Nevada de Santa Marta, Colombia.
Due to its geographic isolation from the Andes and unique elevational gradient, the Sierra Nevada de Santa Marta (SNSM) is recognized for its high rates of endemism, especially in birds, amphibians, and reptiles. Despite very few studies carried out on plants, high rates of endemism have been found among Bryophyta and Melastomataceae. However, rigorous inventories of other plant groups are lacking above 1000 m asl in the mountain range.
The Jungle Biology Lab in collaboration with the Cartagena Botanic Garden JBGP and the ProAves Foundation to establish a permanent 1-hectare forest dynamics plot in the SNSM. The plot, established in 2023, gives us detailed data on a tree community in a patch of primary cloud forest around 2200 m asl. Occurrence data is available through SiB Colombia and GBIF.
Read more about our findings from the plot in Annals of Forest Science, and see our paper in Annals of the Missouri Botanical Garden for broader contextualization about the floristic uniqueness of the SNSM.
Ongoing work in the plot includes microclimate monitoring and repeated inventories to track demography.
Temperature response of net photosynthesis in alpine vegetation.
Temperature response of net photosynthesis in alpine vegetation.
In alpine environments, plant carbon gain depends not only on instantaneous photosynthetic rates but on how leaf temperature is regulated relative to ambient conditions. If leaves maintain similar thermal regimes across elevations, the temperature response of net photosynthesis may remain conserved, even as overall carbon budgets decline at higher elevations due to shorter growing seasons and structural constraints on growth.
In this project, we measured net photosynthesis temperature response, leaf functional traits, leaf temperature, and air temperature in Norwegian alpine plants across an elevational gradient to test how thermal buffering, canopy structure, and growing season length interact to shape carbon balance.
Data from this study are available in Scientific Data.
Distribution and biology of rare magnolias.
Distribution and biology of rare magnolias.
Understanding newly discovered species requires moving beyond initial identification to documenting their geographic ranges, habitat specificity, and ecological interactions—particularly in highly threatened systems such as Andean cloud forests. Establishing how these species reproduce, disperse, and interact with pollinators is essential for accurately assessing their conservation status and informing effective management strategies.
In the eastern Andean cloud forests of Ecuador, I worked with the EcoMinga Foundation to study two recently described Magnolia species (Magnolia vargasiana and Magnolia llanganatensis), each initially known from only a handful of individuals. Through field surveys across remote terrain, I documented more than 300 additional trees, expanding the known populations of both species and identifying a putative natural hybrid between them. Alongside mapping their distributions, I collected data on population structure, leaf and floral morphology, and reproductive phenology, establishing a clearer ecological baseline for these taxa.
We have published the first conservation assessments of M. vargasiana (VU) and M. llanganatensis (EN) on the IUCN RedList.
Contamination of Maine lakes by pharmaceuticals and personal care products.
Contamination of Maine lakes by pharmaceuticals and personal care products.
The contamination of surface waters by pharmaceutical and personal care product chemicals (PPCPs) is well-studied in treated wastewater effluent and urban surface waters, but the extent of PPCP contamination in rural areas unaffected by wastewater treatment or industrial runoff is not well understood .
Exploring PPCP contamination in the rural Belgrade Lakes of Maine, We have detected a handful of PPCPs, such as caffeine and amphetamine, nearly ubiquitously within and between lakes and across seasons. Although the levels we detected were always low, they may have significant impacts on the health and behaviors of aquatic biota. Read more in our publication in the Journal of Environmental Studies and Sciences!
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