Reference Curves for Central Appalachian Red Spruce

Abstract

Red spruce (Picea rubens Sarg.) was a prized timber species in West Virginia during the era of resource exploitation in the late 1800s and early 1900s. As a result, central Appalachian red spruce comprise a much smaller component of high-elevation stand composition and a greatly constricted presence across the region. Widespread restoration efforts are underway to re-establish red spruce across this landscape. However, without benchmarks to gauge growth rates and stand developmental patterns, it is unclear whether these efforts are successful. Our goal was to develop reference curves predicting centile height growth for understory red spruce (≤7.6 m) across the region. We reconstructed the height growth patterns of over 250 randomly selected red spruce seedlings and saplings from 22 high-elevation stands in West Virginia. We also harvested 24 mature red spruce from the same stands to develop juvenile growth curves up to 7.6 m to compare understory growth rates of historical to contemporary rates from the reference curves. Our constructed reference curves showed height growth tended to peak between 10 and 30 years of age. Total heights ranged from 0.95 m to 6.85 m after 50 years. We identified two demographic populations in the mature red spruce trees. All the mature red spruce trees that established after 1890 exceeded the 97% growth centile by age 80. By contrast, only two trees from the pre-1890 population reached the same level by age 80. This work highlights the varied ascension pathways to the overstory for red spruce.