THE BENEFIT OF INCLUDING RARELY-USED SPECIES IN DENDROCLIMATIC RECONSTRUCTIONS: A CASE STUDY USING JUGLANS NIGRA IN SOUTH-CENTRAL INDIANA, USA

The benefit of using multiple species in dendroclimatic reconstructions in the eastern U.S. has been demonstrated. However, the benefit of including rarely-used species in multispecies reconstructions has been little explored. This paper shows the utility of using a rarely-used species in dendrochronology, Juglans nigra, in a multispecies Palmer Drought Severity Index (PDSI) reconstruction at a site in southern Indiana. First, the crossdating J. nigra is established, followed by determining the climate response. The standardized J. nigra chronology is then compared with co-occurring standardized species chronologies (Quercus alba, Quercus rubra, and Liriodendron tulipifera) reported in Maxwell et al. (2015). Using a principal component regression model, the bi-weights of each species were calculated to determine how much J. nigra contributed to the explanatory power of the model. J. nigra had a high interseries correlation (0.604) and mean sensitivity (0.304) and a strong correlation with summer PDSI, which was comparable in strength and more consistent through time than the co-occurring species. The inclusion of J. nigra in the composite reconstruction provided more consistency and better captured the observed PDSI variability. This is compelling evidence for why rarely-used species should be tested for inclusion in multispecies climate reconstructions.