Herbicide effects on leaf litter decomposition processes in an oak-hickory forest

Herbicide treatments (2, 4, 5-Trichlorophenoxyacetic acid) of 0.225 g/m"2 and 2.250 g/m"2 were applied in a Latin square design to the forest floor of an oak-hickory forest in Georgia. White oak (Quercus alba) leaf litter decomposition and litter and soil microarthropod populations were studied in control and treated areas. Weight loss of natural white oak leaf litter averaged 35% for the 1st yr and reached 67% after 2 yr. Litter decomposition rates were similar in control and treated areas. However, white oak leaves defoliated through stem injections lost 59% of their biomass in 1 yr. Decomposition was increased because of initially higher N levels and a lower C:N ratio in defoliated leaf tissue. Herbicide spray treatment increased microarthropod densities for up to 8 mo after application. The herbicide spray apparently influenced springtail and mite reproductive activity in treated areas. The increases in soil and litter microarthropod densities were not sufficient to affect leaf litter weight losses. Repeated defoliation of plant communities and the resulting increased decomposition rates could cause imbalances in litter dynamics and cycling processes. Changes in the timing of annual litterfall and the rates of nutrient release may thus lead to soil desiccation and the depletion of available nutrient pools.