Extramatrical Mycorrhizal Abundance and Grass Nutrition in a Tropical Grazing Ecosystem, the Serengeti National Park, Tanzania

Abstract

The abundance of extramatrical vesicular-arbuscular mycorrhizal (YAM) hyphae was determined in soil samples collected from the upper 10 cm directly beneath grasses at 35 locations in the Serengeti National Park, Tanzania. Samples were collected during the wet season when plants were actively growing and hyphae were measured by membrane filtration, staining, and microscopic counting using a grid intersection method. Total extramatrical hyphae length ranged from 0.03 to 6.95 m g-1 soil with an arithmetic mean of 1.86 m g-1 and a geometric mean of 1.29 m g-l. Hyphallength was negatively correlated with two general measures of soil fertility, organic matter content and total soil mineral nutrient concentration, as well as concentrations of many individual minerals. Hyphallength was positively correlated with the ratio of plant to soil nutrient contents. These results suggest that mycorrhizal associations act to stabilize ecosystem nutrient fluxes, helping to maintain plant concentrations within narrow levels compared with soil variation, and thereby ameliorating potential nutritional stress in both plants and herbivores.