The action of an anecic earthworm (Aporrectodea longa) on vertical soil carbon distribution in New Zealand pastures several decades after their introduction

Anecic earthworms have the ability to incorporate carbon (C) from the surface to depth in the soil. This study aimed to quantify the rate of spread of Aporrectodea longa, and their influence on the amount of C stored, in two contrasting soils where this earthworm was introduced in the 1980s. The rate of spread of A. longa at both sites (5.3–12.5 m/y) is similar to endogeic species. Over several decades there was a decrease in soil C in the presence of A. longa in the Pallic soil (78 912 vs. 85 796 kg C/ha for 0–300 mm) while soil C tended to increase in the Allophanic soil (141 845 vs. 111 076 kg C/ha at 0–300 mm). In the Pallic soil, bulk density tended to be lower in the presence of anecic earthworms at 150–300 mm depths and may have encouraged the decomposition of more stable C. Further, the interaction with higher abundances of endogeic earthworms and lower organic matter inputs in the Pallic soil than the Allophanic soil may help explain the lower soil C in the Pallic soil. The conflicting results in the two soils highlight the influence of the earthworm community and soil properties on C dynamics.