Enchytraeid numbers, biomass and respiratory metabolism in a beech woodland - Wytham Woods, Oxford

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Abstract
The mean annual population density of enchytraeids in the litter and upper 6 cm of soil was found to be 14,590 m-2. Mean individual weights approximated 116, 158 and 151 μg wet wt. in the litter, 0–3 cm and 3–6 cm strata respectively. The mean biomass was estimated to be 1.908 g wet wt m-2. Vertical migration was shown to occur, the upward migration in late Autumn was a response to temperatures in the litter being temporarily higher than those of the 0–3 cm stratum. As a result of upward vertical migration and possibly recruitment, numbers reached a maximum in the litter during Winter. On an annual basis the litter, 0–3 and 3–6 cm strata contained 41.43, 46.44 and 12.12% respectively of the extracted enchytraeids. The equivalent biomass values were 33.18, 52.46 and 14.36%. Total numbers and biomass revealed a general picture of high values in late Autumn to Winter which gradually decreased through Spring and Summer except for a minor peak in May–June. The annual oxygen consumption of the enchytraeids approximated 4.285 l O2 m-2 yr-1 (≡20.461 kcal≡85.610 kJ) and accounted for 1.63% of the total soil metabolism. A production/biomass (P/B) ratio of 4.93 was estimated as was a net population efficiency of 32%. For this site the contribution by enchytraeids to total soil respiration is about one-third that of the earthworms and an order of magnitude greater than that of the nematodes.