Exploring the Linkage Between Physiology and Shade-Related Mortality in Loblolly Pine Branches

Abstract

The importance of crown size in forest management is well recognized, with crown length influencing tree growth and survival. Crown length can serve as a proxy for available photosynthetic area and potential tree growth which makes it an important component of process-based forest models. However, predicting the height to crown base and, hence, crown length, accurately remains challenging due to limited understanding of mechanisms of branch mortality. We conducted an experiment to elucidate the conditions that lead to the death of lower branches under shade conditions in loblolly pine (Pinus taeda). To do this, we explored the relationship between parameters of photosynthetic light response curves and branch mortality using point biserial correlation. Light saturated net assimilation rate (A_max), dark respiration rate (R_d), light compensation point (LCP), and light saturation point (LSP) showed the strongest relationship with branch mortality (r_bs >0.64). We concluded that shade-induced mortality in branches is associated with several physiological changes which include a decline in A_max, R_d, LCP, and LSP. Results from this study will help us predict crown size more accurately and improved prediction of crown size will ultimately lead to improved process-based models predicting stem growth and mortality.

Parent Publication

• Proceedings of the 22nd Biennial Southern Silvicultural Research Conference

Citation

Majekobaje, Adelodun R.; Dean, Thomas J. 2024. Exploring the Linkage Between Physiology and Shade-Related Mortality in Loblolly Pine Branches. In: Bragg, Don C.; Oswald, Brian P.; Koerth, Nancy E., eds. Proceedings of the 22nd biennial southern silvicultural research conference. Gen. Tech. Rep. SRS-274. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station: 170–175. https://doi.org/10.2737/SRS-GTR-274-Pap28.