As trees grow and develop, they sample C and O from the environment and therefore tree-ring C and O stable isotopes (d13C, d18O) record environmental conditions and the tree's response to the environment. We use this tool to reconstruct past physiological responses to abiotic (drought) and biotic (pathogen) environmental stress.
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Western hemlock (Tsuga heterophylla) infected (left) and uninfected (right) with dwarf mistletoe (Arceuthobium tsugense) in the Wind River Experimental Forest, WA
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How can tree-ring stable isotopes inform tree water use?
We used tree-ring C and O stable isotopes to examine the effect of distance from a stream on the growth and physiology of old-growth ponderosa pine (Pinus ponderosa) in central Oregon. Using a process-based model (Predicting Principles in Growth; 3PG) and the tree-ring stable isotope record, riparian trees were bigger, used more water, and exhibited enhanced canopy conductance compared to upland trees. Ulrich et al. (2019) Ecology What are the impacts of dwarf mistletoe on the physiology of host western hemlock?
Hemlock dwarf mistletoe (Arceuthobium tsugense) is a hemiparasitic plant that primarily depends on its host western hemlock (Tsuga heterophylla) for water and nutrients, eventually killing its host. Because it takes decades for the parasite to kill its host, we use tree-ring stable isotopes to investigate its impacts on host physiology. This work can be extended to other systems as there are 42 dwarf mistletoe species with varying host specificity. Marias et al. (2014) Tree Physiology |