Rm. Miller et al., EXTERNAL HYPHAL PRODUCTION OF VESICULAR-ARBUSCULAR MYCORRHIZAL FUNGI IN PASTURE AND TALLGRASS PRAIRIE COMMUNITIES, Oecologia, 103(1), 1995, pp. 17-23
External hyphae of vesicular-arbuscular mycorrhizal (VAM) fungi were q
uantified over a growing season in a reconstructed tallgrass prairie a
nd an ungrazed cool-season pasture. In both sites, hyphal lengths incr
eased throughout the growing season. Peak external hyphal lengths were
111 m cm(-3) of soil in the prairie and 81 m cm(-3) of soil in the pa
sture. These hyphal lengths calculate to external hyphal dry weights o
f 457 mu g cm(-3) and 339 mu g cm(-3) of soil for prairie and pasture
communities, respectively. The relationships among external hyphal len
gth, root characteristics, soil P and soil moisture were also determin
ed. Measures of gross root morphology [e.g., specific root length (SRL
) and root mass] have a strong association with external hyphal length
. Over the course of the study, both grassland communities experienced
a major drought event in late spring. During this period a reduction
in SRL occurred in both the pasture and prairie without a measured red
uction in external hyphal length. Recovery for both the pasture and pr
airie occurred not by increasing SRL, but rather by increasing externa
l hyphal length. This study suggests that growth is coordinated betwee
n VAM hyphae and root morphology, which in turn, are constrained by pl
ant community composition and soil nutrient and moisture conditions.