Effects of Longleaf Pine Restoration

Emily Jordan, Corrina McLeod, Devin Orr, Ellie Johnson, Dr. Thea Hagan

Abstract

The Historic Camden Foundation is currently working to restore acquired lands back to it’s historic longleaf pine state at the Camden Battlefield and Longleaf Pine Preserve in Camden, SC. Restoration goals for the site include reinstating the fire regime necessary for ecosystem maintenance and reducing the basal area of the canopy trees by thinning.

Vegetation community and soil data for a recently thinned stand at the site was taken before and after a controlled burn that took place on March 12, 2020. Five randomly placed plots were surveyed each summer and total species present and various soil characteristics were collected and analyzed.

Comparison of this data will allow for a better understanding of the immediate ecosystem changes due to restoration efforts, particularly prescribed fires, as well as how these efforts have benefited the resurgence of longleaf pine savannas throughout the southeastern U.S.

Introduction

Longleaf pine ecosystems used to stretch vast areas of the United States, however, it is now considered a highly endangered ecosystem. Longleaf pine ecosystems are characterized as being fire-dependent, relying on bunch grasses and a diverse understory of herbaceous species to promote the proper fire regime. Many of these species require frequent fires in order to germinate their seeds, as well as to keep undesired species from overtaking the native ecosystem vegetation. 

In our area of interest at the Camden Battlefield and Longleaf Pine Preserve, there is a distinct lack of the needed fire behaviors and proper understory makeup. This has led to an increase in non-fire dependent species (ex. Hardwoods such as oaks and hickories) that compete with the desired Longleaf pine canopy.

As part of efforts to restore the area, a thinning in 2018 was performed to remove the undesired hardwoods and open the canopy to the desired longleaf pines. More recently, in March of 2020, a controlled burn was applied to the area to not only improve the makeup and diversity of the understory, but to help limit the reemergence of the undesired hardwoods. 

Through these restoration efforts, it is hypothesized that not only will there be a marked improvement in understory diversity, but also an increase in available nutrients for desired species.

Methods and Materials

In 2019, five plots were randomly placed throughout the site and were surveyed the summer before and after the prescribed burn. At each plot three, 20-meter transects were ran from plot center at 0, 120, and 240 degrees. The established plot area (approx. 1,964 m^2) was then walked through and each unique species of plant was identified and recorded. In addition, a closer survey of vegetation communities was done along transect lines.  

Corrina_Devin_work

Fig(1): Devin O. and Corrina M. running transects.

A soil sample was taken at the end of each transect and plot center then mixed together as one whole sample. This final sample was then sent to the Clemson Agricultural Soils lab for testing. This data was analyzed and compared to describe how the fire altered the understory’s abiotic and biotic components.

Emily_work2

Fig (2): Emily J. taking soil samples.

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Fig (3). Line 3, plot TM7 in the summer of 2019 (before controlled burn).

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Fig (4). Line 3, plot TM7 in the summer of 2020 (after controlled burn).

Changes in Soil After Fire

The intensity of the fire is one of the main factors that affect post-fire soil nutrients present on the forest floor. Although the relationship between soil and fire is complex, it is common for forest fires to decrease the total soil nutrient-pool size on a site. However, if the intensity is low, it releases nutrients from the soil that would have otherwise remained trapped in dead plant tissue. 

With any fire, it is expected that through the process of volatilization and oxidation, the percentages of essential elements (ex. phosphorus, nitrogen, and potassium) will decrease. Since this plot was prescribed a surface burn, the results are consistent with what is expected to happen. There was an increase in calcium and magnesium ions in the post-fire results and a slight decrease in phosphorus. This aligns with other studies that found an increase in the concentration of potassium, calcium, and magnesium after a surface level forest fire.

Fig (5). Comparison of the percent of nutrients P, Mg, and Ca in the soil before and after a controlled burn.
Before FireAmount P%Amount Mg%Amount Ca%
Before Fire10.5627.4299.28
After Fire9.7244.28521.48
% Change-7.9561.674.25

Changes in Vegetation After Fire

Following the controlled burn in March 2020, there was a pattern of vegetation changes within all five plots of interest. Compared to the previous year, there was a noted increase in the variety of both woody and herbaceous vegetation. An average of 11.4 new species were identified in each plot in the summer of 2020 than the previous year. These species tended to consist of more grasses and herbaceous species such as wiregrass, smilax, and little bluestem. 

Plants in the Smilacaceae family are heavily resistant to fire and can resprout after being burned. Alongside these fire-resistant species, there was a marked increase in the variety of grasses in the area. These grasses grow quickly and catch fire easily, making them a good conduit for fire spread. All of the species are characteristic of a natural longleaf pine ecosystem. 

Looking back at both the previous year and this year, there was a wide range of different Fagaceae and Juglandaceae and after the prescribed burn, the diversity in these families only increased. This is interesting as the goal of this burn was to control the number of hardwoods growing throughout this area.

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Fig (6): Comparison of the amount of identified species per plot in 2019 and 2020.

Final Overview

Comparing the results of soil samples before and after the controlled burn, we can see that the presence of calcium and magnesium ions increased while phosphorus decreased. These changes line up with what was expected of a surface-level fire. 

Looking at changes in vegetation, there was a marked increase in plant diversity between the summer of 2019 and the summer of 2020. This increase in diversity was mainly in fire-resistant herbaceous species and flammable grass species, both of which promote the needed fire regime to sustain a longleaf pine ecosystem.

References

1. Barnett, J. P. (1999). Longleaf Pine Ecosystem Restoration: The Role of Fire. Journal of Sustainable Forestry, 9, 89-96.

2. Brockway, D. G., & Lewis, C. E. (1996). Long-term effect of dormant-season prescribed fire on plant community diversity, structure and productivity in a longleaf pine wiregrass ecosystem. Forest Ecology and Management, 96 (1997), 167-183.

Acknowledgements

Special thanks to: 

Creative Inquiry of Clemson University 

Frederick (Coy) Myers Jr. and Forest Land Management Inc. 

Virginia Zemp and The Historic Camden Foundation

Clemson Agricultural Soil Lab

All the lovely ladies at the Camden Comfort Inn