Tree species associations of Pinus echinata mill. over a large-scale sampling regime on the interior highlands of ArkansasThis article is part of a larger document. View the larger document here.
The Interior Highlands physiographic province of Arkansas is considered the ecological center of the geographic distribution of shortleaf pine (Pinus echinata Mill.). I used data from the U.S. Forest Service, Forest Inventory and Analysis (FIA) program to identify the major tree species associates of P. echinata across this 66,700-km2 landscape. Across the region, 41,207 km2 were covered by timberland. The study population was represented by 434 relatively undisturbed upland sample plots from the 1995 forest survey of Arkansas. P. echinata ≥12.7 cm in diameter at breast height (DBH) occurred on 211 of these sample plots. Additionally, it ranked first in basal area on 119 plots, second on 39 plots, and third on 19 plots. Where P. echinata was dominant, stand basal area averaged 23.1 m2 ha-1 (±0.57 SEM). I used chi-square to test for degree of association between the stand dominants and to test for positive and negative associations. There was a positive association between P. echinata and Quercus alba L. (X2 = 0.490; 1df). In contrast, there was a negative association between P. echinata and Q. velutina Lam. (X2 = 15.571; 1df). These results demonstrate that the chisquare test of association is effective even on the larger scales of sampling where lack of sample homogeneity may sometimes complicate analysis. Such quantitative tests for species associations offer meaningful insights into P. echinata communities at the landscape scale of sampling.