Abstract
Distributions of soil macroarthropods were studied monthly for 1 yr (February 2001 to January 2002) in three depth strata (0–8, 8–16, and 16–24 cm) at six sampling sites along a moisture gradient stretching from the shore of Lake Yale, central Florida, to an upland hammock. Annual mean density of total soil macroarthropods at these sites varied from 312 to 1,809 individuals/m2; highest density was recorded near the center of the gradient. The most abundant groups of soil arthropods were Isopoda, predominantly Armadillidium vulgare (Latreille), and Diptera larvae (mostly Limoniidae, Chironomidae and Bibionidae). Species of five genera of Chironomidae (Paraphaenocladius sp., Pseudosmittia sp., Metriocnemus sp., Bryophaenocladius sp., and Smittia sp.) were found. Total number of macroarthropod species at individual sites varied between 40 and 70. The majority (61–92%) of soil macroarthropods from all sites was recovered from the near-surface stratum. Proportion of soil macroarthropods found in the two deeper strata increased with distance from the shoreline, elevation above lake water level, soil carbon content, and acidity of soil. The two sites located near the shoreline were continually flooded from September to January after the lake water level increased by up to 30 cm. Two inland sites were periodically (June–September) flooded by rain water. Flooding at either site caused decreased density of soil macroarthropods, with the effect of lake flooding being more pronounced. Density of soil macroarthropods at flood-affected sites peaked during spring, whereas seasonal changes in density of these invertebrates at most upland sites were less pronounced and peaked in autumn. Results indicated that seasonal migration and recolonization by soil macroarthropods along the moisture gradient are important strategies to overcome flood-affected population losses.