Document: JAM-3-99-126

Ectomycorrhizal diversity alters host tree performance in experimental host-symbiont culture conditions.

BAXTER, J.W.* and J.DIGHTON

Rutgers University, New Lisbon, NJ 08064 USA ¹

Abstract:
We examined the influence of ectomycorrhizal fungal diversity on host plant performance. Individual birch, Betula populifolia, seedlings were grown with 1, 2, or 4 species of ectomycorrhizal fungi simultaneously and without mycorrhizas for 10 weeks in peat-vermiculite moistened with MMN nutrient medium. Six replicate 1, 2 and 4 species mycorrhizal communities were generated by random draws from a pool of 6 fungal species. Each unique species combination was replicated four times in order to distinguish compositional effects from that of mycorrhizal richness. When assessing host responses, we used the realized diversity rather than the initial inoculated diversity of the treatment. Multiple mycorrhizal colonizations were successful in almost all cases and no colonization was observed on the controls. Mycorrhizal colonization per m seedling root length increased from the 1- to the 4-species diversity treatment. Seedling shoot mass decreased from 1 to 4 species of mycorrhizal fungi, while root mass increased across this range of species richness. Despite higher mycorrhizal colonization rates with increasing fungal diversity, there was no relationship between colonization rate and either shoot or root mass. Our results suggest that higher mycorrhizal richness per se, rather than differences in species composition or higher colonization rates, lowered shoot mass and increased root mass in laboratory-grown birch seedlings. Increased competitive vigor among the competing fungi and consequent greater carbon allocation to roots at the higher diversity levels may explain these results.

Keywords: ectomycorrhizal fungi,mycorrhizas

This abstract is being presented at: 11:15 AM in session:
Oral Session #8: Mycorrhizal Fungi.