Pathogen-induced defoliation impacts on transpiration, leaf gas exchange, and non-structural carbohydrate allocation in
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ORIGINAL ARTICLE
Pathogen‑induced defoliation impacts on transpiration, leaf gas exchange, and non‑structural carbohydrate allocation in eastern white pine (Pinus strobus) Cameron D. McIntire1,2 · Brett A. Huggett3 · Emma Dunn3 · Isabel A. Munck1 · Matthew A. Vadeboncoeur4 · Heidi Asbjornsen2,4 Received: 11 August 2019 / Accepted: 18 September 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Key message Pathogen-induced defoliation resulted in a reduction in transpiration, an upregulation of photosynthesis in the early growing season, and no change in NSC reserves across stem, root, and foliar tissues. Abstract The defoliation of eastern white pine (Pinus strobus L.) by native fungi associated with white pine needle damage (WPND) can substantially reduce foliar area for much of the growing season in the northeastern United States. Chronic defoliations in the region are known to have slowed growth rates in symptomatic stands, but the physiological impacts of WPND as it relates to tree water use and carbon assimilation are largely unresolved. We investigated how the severity of WPND defoliation influences transpiration throughout the course of a growing season. We also assessed leaf-level gas exchange between defoliation severity classes and needle age over time. Finally, we compared concentrations of non-structural carbohydrates (NSC) between defoliation severity classes in five different tissue types over time. We found that trees experiencing a high-severity defoliation had 20% lower sap flux density compared to low-severity individuals. We found that rates of photosynthesis were significantly influenced by the needle age class and time of year, while instantaneous water use efficiency was higher across all needle age classes late in the growing season. Our findings suggest that the residual current-year foliage of high-severity defoliated trees compensated for the loss of mature second- and third-year foliage in the early portion of the growing season. This study found that soluble sugars and starch varied significantly over time and by tissue type, but defoliation severity had little effect on NSC concentrations. Together with reduced basal area increment in high-severity trees relative to low-severity trees, this indicates that WPND-affected trees are prioritizing NSC storage over secondary growth. Keywords White pine needle damage · Defoliation · Forest pathogen · Sap flux · Leaf gas exchange · Non-structural carbohydrates
Introduction Communicated by Jared LeBoldus. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00468-020-02037-z) contains supplementary material, which is available to authorized users. * Cameron D. McIntire [email protected] 1
Present Address: USDA Forest Service, State and Private Forestry, 271 Mast Rd., Durham, NH, USA
Department of Natural Resources and the Environment, University of New Hampshire, 56 College Rd., Durham, NH, USA
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Defoliation of eastern white pine (Pinus strobus L.) by
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