Taxonomic and phylogenetic shifts following an inland derecho

Abstract

Abstract In 2009, a derecho occurred in southern Illinois affecting large areas of the regional forest systems. Previous research reported multi-strata species compositional shifts post-derecho at LaRue Pine Hills/Otter Pond Research Natural Area (LPH/OP RNA). Here, we expand these observations to include phylogenetic and spatial relationships, including elevation as a covariate. Surveys were conducted before and after the derecho. Univariate and multivariate analyses documented diversity and compositional shifts. Spatial analyses identified distinct spatial patterns in taxonomic (TSR) and phylogenetic (PSR) species richness, and metrics of phylogenetic clustering and overdispersion (net relatedness index and nearest taxon index; NRI and NTI, respectively), in seedling, sapling, and tree communities. Decreases in tree TSR and PSR and sapling PSR, and increases in sapling NTI occurred post-derecho. Seedling diversity-elevational relationships exhibited a humped-backed relationship in all cases excluding NTI pre-derecho, while saplings showed positive linear relationships between phylogenetic metrics and elevation. Despite the relatively small elevation gradient (122m), multivariate analyses identified elevation as the most influential environmental driver of community dissimilarity. Local Moran’s I analysis showed post-derecho clustering in the north-central extent. Co-Kriging (CoK) interpolation predicted that seedling diversity increased in the southwestern extent, while sapling diversity increased in the eastern extent and tree diversity increased from the north-central extent post-derecho, indicating competitive interactions at lower elevations and environmental filtering at higher elevations. Seedling and tree NRI and NTI increased in the southern extent, whereas sapling clustering increased in the northeastern extent. Co-Kriging had a better prediction capability compared to other spatial interpolation methods.