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Goal: Apply Knowledge Globally New genetic tools can help restore high elevation forests

Red spruce populations in the southern Appalachians are isolated from larger populations farther north, resulting in a lack fitness due to inbreeding depression. Researchers are using cutting edge genetic tools to characterize gene diversity and accumulation of negative genes across the species range. The information will be used to recommend seed sources for restoration planting that will restore fitness in the next generation of red spruce trees.

Tiny red spruce seedlings in a lab, with identifying barcodes next to each.
Thousands of red spruce seedlings were monitored for early life fitness traits such as height and survival at the University of Vermont. USDA Forest Service photo by John Butnor.

Red spruce is a species with the potential to live for hundreds of years if left undisturbed. Separate from the core of the species range in the northeastern U.S., populations are found in high elevation “sky-islands” as far south as Tennessee, North Carolina, and Virginia. These high-elevation forests are home to migratory songbirds, the Carolina northern flying squirrel, and other species found hundreds of miles to the north. In the past century much of the forest in the South was unsustainably logged, leaving less than 10% of the original. To understand the viability of existing red spruce populations and devise restoration strategies, researchers collected seeds from 340 individual trees across the range and germinated thousands of seedlings. The team examined seed characteristics (weight, germination) and early life growth characteristics (survival, height) in combination with cutting edge genetic analysis using exome sequencing. This streamlined process examines expressed proteins, or exomes, instead of sequencing large and repetitious genomes.

Small populations with a high degree of genetic similarity accumulate negative mutations and experience inbreeding depression. Populations at the southern edge of the range were demonstrably less fit than the species as a whole, according to the study results.

But there is an upside to this discouraging story: the red spruce exome database will be used to recommend seed sources for restoration planting to enhance heterozygosity and restore fitness in the next generation of trees.

A scenic overlook from Mount Mitchell State Park
This research will inform real world decisions on seed selection in restoration plantings. Depicted is a high elevation forest in Mount Mitchell State Park in North Carolina where some of the earliest attempts at red spruce restoration were made in the early 1900s. USDA Forest Service photo by John Butnor.
Principal Investigators
John Butnor, Research Plant Physiologist
RWU
4160 - Forest Genetics and Ecosystems Biology
Strategic Program Area
Resource Management and Use
Publications
Genomic drivers of early-life fitness in Picea rubens
External Partners
Thibaut Capblancq - University of Vermont
Helena Munson - University of Vermont
Stephen R. Keller - University of Vermont