Montana State researchers focus on tree carbohydrates in multi-phase study
The project’s goal is to increase understanding of how stored carbohydrates affect tree survival during drought and develop a method to measure those levels remotely.
MSU photo by Colter
Peterson Montana State University professors Danielle Ulrich, left, and Anna Schweiger are pictured Friday, Nov. 15, 2024, in Bozeman, Montana. The researchers recently received a National Science Foundation grant to study how stored nutrients affect tree survival after drought.
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BOZEMAN - The ability of a tree to recover from drought is essential to its survival and – in the case of whitebark pine – potentially critical to the future of the species, which is experiencing significant decline and was listed as threatened under the Endangered Species Act in 2022.
Now, with nearly $1.3 million in funding from the National Science Foundation, two Montana State University scientists are studying how non-structural carbohydrates, or NSCs, stored in the needles of whitebark pine trees affect their abilities to survive and recover from drought. In addition, the team will develop a method to remotely measure NSC levels to pave the way for assessing the drought tolerance of entire forests and to streamline lab-based measurements of NSCs.
The resulting knowledge and technology should help wildland managers assess the drought tolerance of tree populations by predicting whether an individual tree will survive a drought, according to Danielle Ulrich, assistant professor in the Department of Ecology in the College of Letters and Science and principal investigator for the five-year study.
NSCs are products of photosynthesis comprising starches and soluble sugars. Ulrich said one goal of the study is to better understand how those NSCs affect the physiological mechanisms of plant recovery and survival in response to drought.
“During preliminary drought treatments in the greenhouse, we found that individuals with higher starch levels in their needles prior to treatment were more likely to survive the drought,” Ulrich said. “This suggests that we may be able to use pre-drought, or pre-stress, carbohydrate dynamics, to predict before the onset of a drought whether an individual tree will die or survive.”
With the ability to measure NSCs remotely, scientists also may be able to predict before drought occurs which trees will survive and which will die during a drought, Ulrich said. That’s a notoriously challenging feat, partly because most physiological metrics that detect the likelihood of mortality during a drought are evident only after trees have passed a point of no recovery.
For this study, Ulrich and her students will use time-consuming, labor-intensive, and lab-based processes to measure stored NSC levels in juvenile greenhouse trees exposed to simulated drought conditions. Using the same techniques, they also will monitor seasonal changes in stored NSCs in mature trees in the field. But as they are collecting the data through traditional means, the grant’s co-principal investigator Anna Schweiger will lead the team in measuring the carbohydrate content of the same trees with a different method.
“The contents of structural carbohydrates and non-structural carbohydrates, pigments, macro- and even some micronutrients all can be derived from spectroscopy,” said Schweiger, assistant professor in the Department of Land Resources and Environmental Sciences in the College of Agriculture. “It can more or less immediately determine the content of starches non-destructively.”
Tools called optical spectrometers are used to identify materials by analyzing the energy emitted or absorbed at different parts of the visible, ultraviolet, and infrared spectra. These instruments capture hundreds of contiguous spectral bands to provide detailed analysis of materials based on their unique properties. For this work, Schweiger will use a hand-held spectrometer to measure spectral reflectance directly at the leaf level.
The team will combine these spectral measurements with those obtained through the traditional lab-based methods. They then will build and test a model to estimate NSC levels from spectral data alone and, once it is perfected, work to develop a system for its use at larger scales in the field. This part of the research will make use of imaging spectroscopy, which can capture hundreds of wavelengths for each pixel in an image and be tied to the chemistry and structure of plants.
“We’re going to see if we can remotely measure NSC levels to predict drought recovery and survival and also streamline the measurement process,” Ulrich said. “The field component will involve measuring trees in the field. We’ll monitor seasonal NSC dynamics during natural drought that occurs in the summer to find out if we can use leaf spectra to make accurate predictions of NSC dynamics on mature trees in the field.”
Schweiger said the sensor also should be able to differentiate tree species from a distance, providing information that will be useful for managers to assess a particular forest’s vulnerability to specific stressors. But the goal is to devise methods for gathering information that will be helpful to land managers as they make decisions, particularly for endangered species like the whitebark pine.
