Arthropod Community Dynamics in Three Ruderal Old Fields with Possible Effects of Solid Rocket Fuel Exhaust

Arthropods were collected at three sites on the Canaveral Peninsula of the east central Florida coast, from May until November, 1975. These sites were old fields dominated by grasses and herbs and one of them (site 1) was located near Launch Complex 41, Kennedy Space Center. A modified drop-trap of 0.5 m2 was used to trap arthropods at approximately 14-day intervals. A vacuum collector removed the arthropods and loose material which was visually inspected for arthropods by the unaided eye and a 7X dissecting scope. A total of 12,296 arthropods was collected during the study. Insects were by far the most numerous group, usually contributing 85 to 95% of the individuals. Ants were very numerous comprising 47% of all individuals and were most numerous at site 1. Arthropod density was greatest on site 1 and increased on all three sites until October and then declined November. A bimodal trend in herbivore density occurred with peaks in June-July and October-November. Predators increased during the study and this significantly correlated with the increase in all other arthropods on the three sites and with herbivores on site 2 and 3. Ants increased in density during the study, while parasites, scavengers, and omnivores remained at low densities. The percentage of predators was roughly constant over most of the study. New species were encountered on site 1 about 1.5 times a fast as on sites 2 and 3. The distribution of individuals among the insect families was similar for the three sites, but site 1 averaged more individuals per family. The average number of individuals per species on site 1 was about double that for sites 2 and 3. Species diversity (Shannon-Weaver) values indicated that arthropods at site 1 were more evenly distributed among the species. Dominance (Simpson) values were not significantly different among the three sites. Community similarity indicated that about 50% of the species on one site were found on one of the other two sites. The different plant communities or habitats surrounding the sites were apparently unrelated to the number of arthropod species present on the study sites. The number of arthropod species present did appear to be related to differences in the number of plant species and their relative abundance on the grids. The launches of two Viking spacecraft appeared to have no detrimental effect on the nearby arthropods