COS 9-3 - Moderate windthrow and salvage logging do not alter herbaceous diversity or composition in twenty-one-year study of Tennessee coastal plain forest

Abstract: The southeastern United States supports high herbaceous diversity in forested systems. However, maintaining this diversity in the face of climate change will require understanding how the forecasted increase in disturbance severity may affect herbaceous species. Few long-term studies have analyzed the effects of varying disturbance severity (from multiple natural and/or anthropogenic disturbances) on herbaceous species diversity and composition.

Here, we present a study of a coastal plain forest that weathered a moderate-severity windstorm and subsequent salvage logging in 1999 and analyze how herbaceous diversity and composition have changed between sampling in 2001 and 2022. In 2001, sixteen 30x30 meter plots were established at Natchez Trace State Park in Tennessee; eight in unsalvaged stands and eight in salvaged stands. Plot-level severity was calculated, based on the proportion of basal area fallen or salvaged. Average herbaceous diversity, composition, and canopy openness did not differ between unsalvaged and salvaged plots. In 2022, the same plots were re-sampled in order to make historical comparisons. Average herbaceous diversity, composition, and canopy openness did not vary between plots; however, canopy openness did significantly decrease between 2001 and 2022.

These data support two conclusions: 1) low-to-moderate severity disturbances (whether from single or multiple disturbances) may not alter herbaceous diversity and composition, and 2) the herbaceous layer, in absence of additional major disturbances, supports similar levels of diversity and composition over long periods of time, as demonstrated by similar values in both 2001 and 2022. This long-term study supports the validity of many short-term (3-5 years post-disturbance) studies’ post-disturbance conclusions.