THE EFFECTS OF LIVE AND DEAD ROOTS ON SOIL FUNGI IN SPODOSOLIC SOILS OF THE NEW-JERSEY PINELANDS

The effects of live and dead roots on soil fungi were investigated exp erimentally in a spodosolic soil of the New Jersey Pinelands. Field me socosm plots were constructed to have a layer of either C- and N-rich organic soil or a vermiculite substitute overlying a layer of sandy mi neral soil with a very low organic content. The plots were also suppli ed with live pitch pine and blueberry roots or dead pitch pine roots i n varying quantities based on naturally occurring densities (half, sam e, and double the ambient quantities). All plots were sampled 1 year a fter construction (June 1991), and three more times in two subsequent years (November 1991, June 1992, June 1993). In the presence of live r oots, fluorescein diacetate-determined (FDA-active) fungal hyphae, tot al fungal hyphae, and soil moisture decreased significantly in the org anic material, while no change was associated with the dead roots. The FDA-active fungal length in the live-root plots ranged from 40 to 165 mg(-1) soil, and from 55 to 335 mg(-1) soil in the dead-root plots. W hile the total fungal length in live-root plots remained constant over time (similar to 3000 m g(-1) soil), the total fungal length in the d ead-root plots increased from an initial value of 3000 to > 4000 m g(- 1) soil at the conclusion of the study. Fungal lengths in mineral soil were higher under organic material than under the vermiculite substit ute. Soil moisture was higher in the presence of live roots in mineral soils, but this did not increase the fungal abundance. Inputs of dead roots did not alter the fungal abundance. Overall, we demonstrated th at live and dead roots had different effects on fungal abundance in so ils with contrasting qualities, and in a spodosolic forest soil, roots could have ecosystem effects very different from those in agricultura l soils.