Sustain Our Nation's Forests and Grasslands

Pondberry — An endangered species seeks sunlight

Pondberry has been listed under the Endangered Species Act since 1986. Photo courtesy of James Henderson, Golden Delight Honey.

MISSISSIPPI — Pondberry is rare and endangered, but don’t underestimate the species.

Forest Service research foresters Brian Lockhart and Emile Gardiner, with several other Southern Research Station scientists, recently investigated pondberry’s physiological response to light availability and soil flooding. Their study, Light availability and soil flooding regulate photosynthesis of an imperiled shrub in lowland forests of the Mississippi Alluvial Valley, was recently published in the journal Photosynthetica.

Pondberry occurs in several southeastern states. Lockhart and his colleagues used plants from the lower Mississippi Alluvial Valley for their study. In some parts of the valley, dense forest canopies intercept most of the sunlight before it reaches the forest floor.

The scientists grew 3,456 pondberry shrubs in the Flooding Research Facility at the Sharkey Restoration Research and Demonstration Site in Mississippi. The facility contains a dozen impoundments that can be flooded for set periods of time, and to specific depths.

The scientists flooded pondberry for 0, 45 or 90 days. They also built shade houses in the impoundments that provided 5, 37 or 70 percent of full sunlight.

Shrubs that received 37 or 70 percent sunlight show a photosynthesis rate 147 percent greater than shrubs that received 5 percent light. Shrubs growing in 5 percent sunlight had low rates of photosynthesis.

Flooding displaces oxygen from the soil. The lack of oxygen is stressful and potentially deadly for plants. Pondberry survived multiple years with 90 days of soil flooding. However, these plants photosynthesized at low rates, no matter how much light they received.

Pondberry that endured 45 days of flooding bounced back quickly. The shrubs in this flooding regime had up to 39 days to recover from flooding before measurements, and they had similar rates of photosynthesis as plants that hadn’t experienced any flooding.

Despite the soil flooding, pondberry flowered in March, as it usually does. How can a plant this hardy be endangered? The answer is probably tied to pondberry’s inability to compete with other species.

This study suggests that pondberry’s ability to quickly recover after soil flooding gives it an advantage over other species. The goal is to help managers develop conservation and recovery plans for pondberry. Its plasticity to light gives managers a lot of options for improving its growth and vigor.