Pathogen-induced defoliation impacts on transpiration, leaf gas exchange, and non-structural carbohydrate allocation in eastern white pine (Pinus strobus)

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.

Physiological impacts of beech leaf disease across a gradient of symptom severity among understory American beech

“…Furthermore, it would be meaningful to measure leaf traits in American beech trees that exhibit no symptoms of BLD to determine if there is a difference between asymptomatic leaves within an infected tree comparable within a tree that is void of disease. Many tree species demonstrate a compensatory response to defoliation via an upregulation of photosynthesis (Reich et al, 1993;Williams et al, 2016;McIntire et al, 2020), thus it's feasible that residual leaves within diseased American beech trees attempt to account for a net loss of carbohydrate. The compounding stress induced by multiple years of carbon limitation associated with BLD may become a consequential factor for inciting tree mortality, especially when coupled with other pests, diseases, and environmental elements.…”

Impact of Twig-Tip Dieback on Leaf Nutrient Status and Resorption Efficiency of Mango Trees

“…The reduction in nutrient resorption efficiency would also mean that plants would have to increase their nutrient intake from the soil, which would be more costly in low-nutrient environments [38]. This is detrimental to the nutritional economics of trees because it can shorten leaf lifetime, limit photosynthetic capacity, and lessen internal nutrient cycling [56]. Furthermore, the current season's slower growth will have a cumulative effect on the upcoming years as nutrient reserves in perennial tissues are depleted [57].…”