The Effects of Prescribed Burning on Soil and Litter Invertebrate Diversity and Abundance in an Illinois Oak Woodland

The effect of 23 years of low intensity prescribed burning on soil and litter invertebrates was studied over 18 months. Samples were collected from 40 plots distributed among annually burned, periodically burned (every 3–4 yrs), and unburned areas of an oak woodland. A total of 26,416 invertebrates representing 21 classes and orders were extracted from soil core and litter layer samples using Berlese-Tullgren funnels. Invertebrates were 25 times more abundant in litter than soil, and Acari and Collembola were the most prevalent taxa, accounting for 76% and 17%, respectively, of the total collection. Statistical analyses of the Shannon entropy index for diversity and associated values of class and order richness, evenness, and abundance indicated that burning was not associated with significant changes in the broad invertebrate community. Average Shannon entropy indices (H) ranged from 0.73 to 0.78 across burn treatments for soil samples and from 0.43 to 0.46 for litter samples. However, within Acari, diversity indices were significantly lower (P < 0.0005) in annually burned plots (H = 0.72) versus unburned controls (H = 0.85), and periodic burn plots had an intermediate H value of 0.79. Taxa evenness was similar in all treatments (J = 0.40–0.57), reflecting the widespread distribution of Acari and Collembola and rare occurrence of several orders from which 20 or fewer individuals were collected. Fall sample dates had more diverse (soil and litter) and abundant (soil) invertebrate assemblages than the spring date (P ≤ 0.001). reflecting large seasonal shifts in Acari. The average depth of the litter layer was similar, at 2.8–3.1 cm, in all three burn treatments, and was most varied in unburned plots. Collectively, the findings suggest that long term burning of the woodland for the purpose of vegetation management has not altered significantly the broadly classified invertebrate community. Possible influences of postfire recovery interval, low fire intensity, and remnant litter refugia are considered.