Physiological Mechanisms of Foliage Recovery after Spring or Fall Crown Scorch in Young Longleaf Pine (Pinus palustris Mill.)

Mary Anne S Sayer,Michael C Tyree,Eric A Kuehler,Dylan N Dillaway,John K Jackson

doi:10.3390/f11020208

Mary Anne S Sayer, Michael C Tyree + Show 3 more

Open Access

https://doi.org/10.3390/f11020208

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Abstract

We hypothesized that physiological and morphological responses to prescribed fire support the post-scorch foliage recovery and growth of young longleaf pine. Two studies conducted in central Louisiana identified three means of foliage regrowth after fire that included an increase in the gas exchange rate of surviving foliage for 3 to 4 months after fire. Saplings also exhibited crown developmental responses to repeated fire that reduced the risk of future crown scorch. Starch reserves were a source of carbon for post-scorch foliage regrowth when fire was applied in the early growing season. However, the annual dynamics of starch accumulation and mobilization restricted its effectiveness for foliage regrowth when fire was applied late in the growing season. As such, post-scorch foliage regrowth became increasingly dependent on photosynthesis as the growing season progressed. Additionally, the loss of foliage by fire late in the growing season interrupted annual starch dynamics and created a starch void between the time of late growing season fire and mid-summer of the next year. The occurrence of drought during both studies revealed barriers to foliage reestablishment and normal stem growth among large saplings. In study 1, spring water deficit at the time of May fire was associated with high crown scorch and poor foliage and stem growth among large saplings. We attribute this lag in stem growth to three factors: little surviving foliage mass, low fascicle gas exchange rates, and poor post-scorch foliage recovery. In study 2, May fire during a short window of favorable burning conditions in the tenth month of a 20-month drought also reduced stem growth among large saplings but this growth loss was not due to poor post-scorch foliage recovery. Application of this information to prescribed fire guidelines will benefit young longleaf pine responses to fire and advance efforts to restore longleaf pine ecosystems.

Highlights

Longleaf pine (Pinus palustris Mill.) was once a dominant tree species across the southeasternUnited States [1,2]
Mean morning Asat in 2003 was 16% less on day 128 compared to days 211 and 267 and this effect is attributed to a rainfall deficit in April and May
We propose that climate-driven reductions in Asat regardless of sapling size and high crown scorch among large saplings challenged re-establishment of foliage mass after May 2005 fire in study 1

Summary

Introduction

Longleaf pine (Pinus palustris Mill.) was once a dominant tree species across the southeasternUnited States [1,2]. Longleaf pine (Pinus palustris Mill.) was once a dominant tree species across the southeastern. Throughout the second half of the twentieth century, research to improve longleaf pine regeneration and restore longleaf pine ecosystems emerged [7,8,9,10,11,12]. These efforts, together with renewed use of prescribed fire and federal mandates to protect species intrinsic to longleaf pine ecosystems, set the stage for the America’s Longleaf Restoration Initiative [13,14]

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