Document: HEA-3-35-13

N source diversity promotes plant community diversity under N-limiting conditions.

REYNOLDS, H.L.* ¹ and B.L.FOSTER ²

WK Kellogg Biological Station, Hickory Corners, MI 49060 ¹
University of Kansas, Lawrence, KS, 66045 ²

Abstract:
We manipulated microbial diversity (inoculated or not) and diversity in N source (NH₄+NO₃+urea or NH₄ alone) in greenhouse microcosms seeded to yield initially equal densities of old-field perennials. Microcosms consisted of 0.1 m² pots filled with sterilized flaked silica clay (turface) as the growing medium. The experiment was conducted at two levels of overall N fertility (low and high), in each case using 8 perennials typical of low or 8 perennials typical of high fertility soil. We found that increasing the diversity of N sources led to a significant increase in plant community diversity (Shannon-Weaver index) at low overall N fertility, but had no effect on plant diversity at high overall N fertility where light penetration to the soil surface was lowest. Microbial diversity had no effect on plant community diversity, although preliminary data show no difference in average microbial activity levels between inoculated versus non-inoculated pots. These results suggest that niche partitioning among multiple forms of N may contribute to plant species coexistence under conditions in which N is a relatively more limiting resource than light.

Keywords: plant community diversity, N, niche partitioning

This abstract is being presented at: 10:30 AM in session:
Oral Session #23: Soil Ecology.