Mineral Cycling in Southeastern Ecosystem

Mineral Cycling in Southeastern Ecosystem - Fred G. Howell

A 10-compartment model of the movement of calcium and potassium through a selected cryptozoan food web was constructed. The compartments were litter and microflora, Diplopoda, Cryptostigmata, Orthoptera, Pulmonata, Collembola, medium Araneida, Coleoptera, small Araneida, and Mesostigmata. The densities of these compartments were estimated using standard population-estimation techniques. The fluxes of potassium and calcium between the compartments were estimated using radioactive tracers. Two sets of models for each element were constructed: time-varying-coefficient models based on the state of the systems in the summer and constant-coefficient models that use the annual integrated fluxes from the first set of models. After the nutrient models were made, two biomass models based on the annual potassium and calcium fluxes were constructed. Results indicated that the models based on the summer states of the systems overemphasized the contribution of mesofauna to litter decomposition. On the basis of the annual nutrient models, Cryptostigmata and Collembola were the most important saprovores and small Araneida and Mesostigmata were the most important predators. The biomass model based on calcium fluxes showed that saprovores accounted for 20% of the total annual input; this agrees with the literature. The models may have underestimated the impact of saprovores on litter decomposition for two reasons. First, animal feeding rates may have been underestimated because of inflated uptake values, and, second, the fauna may control litter decomposition either directly or indirectly, but feeding-rate studies measure only the direct controls, which may be of lesser importance to litter decomposition.