PONDERING PONDEROSAS: PHYSIOLOGICAL RESPONSES OF PINUS PONDEROSA PROVENANCES IN A PALOUSE COMMON GARDEN STUDY

Ksenia Alice Pereverzeva

doi:10.7273/000007447

Ponderosa pine (Pinus ponderosa), an economically, ecologically, and culturally significant tree species native to the Pacific and Inland Norwest, is experiencing a decline in natural regeneration as a result of anthropogenic climate change and the increasing prevalence of high-severity wildland fires (WLFs). To better understand the species’ ability to withstand more arid conditions brought on by a changing climate, we studied 28 different P. ponderosa provenances sourced from across the Inland Northwest and grown in a common garden located in eastern Washington state. Our study investigated how climate characteristics of provenance sites – such as mean annual precipitation (MAP), mean annual temperature (MAT), continentality (∆T), seasonality index (SI) of precipitation, vapor pressure deficit, elevation, latitude, and longitude - interacted with common garden growth traits (height growth rate (HGR) and radial growth rate (RGR)), physiological responses (non-structural carbohydrates (NSCs), leaf %N and water content (LWC), stable carbon isotope composition (ẟ13C)) and spectral reflectance data interpretations (vegetation indices such as, Normalized Difference Vegetation Index (NDVI), Normalized Difference Water Index (NDWI), Normalized Difference Red Edge Index (NDRE), Photochemical Reflectance Index (PRI)). Using a combination of correlation matrices, linear regressions and partial least squares regression (PLSR), we analyzed the provenance in a common garden setting to gain insights into ponderosa pines’ physiological responses and its capacity for local acclimation to a more arid environment. We hypothesized that (1) trees from wetter and cooler provenances would exhibit less growth and show more signs of physiological stress, and (2) physiological traits can be sensed through hyperspectral measurements and PLSR analysis. Our findings indicated that provenance site precipitation influenced physiological responses of %N and δ13C, while provenance site temperature (MAT) affected NSC concentrations and growth rates generally supporting our first hypothesis. Hyperspectral PLSR and indices explained some variance in observed physiological traits, such as NSC concentrations, leaf %N and water content, but overall correlations were low, providing limited support for our second hypothesis. Overall, provenance climate had a relatively small influence on variation in physiological responses and growth, explaining only 10% of the variability. Nevertheless, trees from all 28 provenances have been able to persist, grow, and even reproduce at the common garden site, suggesting that stress tolerant P. ponderosa from sites with a range of climates can acclimate to hotter and drier conditions.

PONDERING PONDEROSAS: PHYSIOLOGICAL RESPONSES OF PINUS PONDEROSA PROVENANCES IN A PALOUSE COMMON GARDEN STUDY

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