ANTONSEN, HILDE1, ROGER C. ANDERSON2*, and STEVEN A. JULIANO2. 1Agricultural University of Norway, Department of Biology and Nature Conservation, Post Box 5014, N-1432 Aas, Norway; 24120 Department of Biological Sciences, Illinois State University, Normal, IL 61790-4120 USA. - Reanalyzing data on effects of nutrients on Schizachyrium scoparium (little bluestem) with high and low AM colonization.
An experimental field study was conducted to evaluate the impacts of
supplemental nutrients (N, P, K and Ca+Mg) on little bluestem grass
(Schizachyrium scoparium) with a high (21.0 +/- 0.7%) or low
(3.2 +/- 0.4%) levels of colonization by arbuscular mycorrhizal fungi
(AMF). Low-colonized plants were grown in autoclaved soil in a
glasshouse and transplanted into fumigated soil in the field, while
high-colonized plants were started in unsterilized soil and planted
into unfumigated field soil. Originally, data were analyzed by
multiple univariate analysis of variance. Previous conclusions drawn
from these analyses were that bases (Ca+Mg) were the limiting
nutrients in this sandy prairie system. Since tools for performing
multivariate statistics are now more accessible and userfriendly, a
reanalysis of the data was performed. New interpretations suggest that
phosphorus and bases were limited nutrients in this system, and
enhanced little bluestem growth occurred when mycorrhizal colonization
was low. However, none of the added nutrients had significant effects
on growth for plants with high levels of colonization. This
interaction is explained by the cost of having a fungal partner. Even
if levels of P and Ca+Mg are high enough to sustain increased growth,
available carbon sources are not sufficient for increased growth due
to the drain of the fungal component. Thus, in this sandy prairie
system the AMF acts as a parasitic organism.
Key words: arbuscular mycorrhizal fungi, inorganic nutrients, multivariate analysis, Schizachyrium scoparium