We investigated the importance of present-day and historical local and regional factors for determining spatial patterns of species richness in longleaf pine savannas. Using a nested-plot sampling design, we surveyed understory plant communities at 40 longleaf pine savannas that have been managed for Red-Cockaded Woodpecker populations at the Savannah River site in South Carolina.
Results/Conclusions
History (historical land-use, stand age, and time since last fire) had significant effects on species richness at both local (≤1 m²) and large scales (100 – 1000 m²). Intensive agricultural history decreased species richness relative to continuously forested stands. For those stands with agricultural history, richness increased with stand age. In general, richness decreased with time-since-fire. It was only at the smallest spatial scales (0.01 – 0.1 m²) that the effects of overstory management were apparent, with richness declining as a function of increasing stand basal area and canopy cover. We observed significant positive relationships between large-scale (1000 m²) and small-scale richness, which we attribute to history as the dominant driver of richness across scales. This relationship was strongest between 1000m² and 1 m² (r² ≥ 0.78), but declined sharply at the smallest scale, 0.01 m² (r² = 0.41), which may be explained by the increasing importance of overstory density for controlling richness at very small scales. This work elucidates complex interactions between land-use legacies and present-day land management, with varying effects on species richness at large and small scales. We suggest that management plans must take into account land-use history when setting priorities. Furthermore, monitoring and management assessment efforts must consider scale, as outcomes may differ at large vs. small sampling scales.
