Phalaris arundinacea (reed canary grass) is a highly aggressive graminoid species that currently is invading most of the northern United States.  In areas previously used for agriculture, and other recently disturbed habitats, P. arundinacea can quickly out-compete native flora and create large monocultures, which can greatly reduce biodiversity and alter ecosystem functioning.  Much research has focused on the growth response of P. arundinacea to varying abiotic and biotic conditions, but surprisingly little has examined how variation in light, soil-N, and moisture affects growth and resource allocation.  Recent experimental evidence showed that when soil-N levels were lowered through the addition of C (as sawdust), P. arundinacea’s growth rate decreased.  This decrease was most likely due to a shift in internal resource allocation.  We studied the growth response and resource allocation of P. arundinacea to contrasting levels of light, soil-N, and moisture in a greenhouse experiment using a split-plot factorial design.

Results/Conclusions

Significant 3-way interactions (MANOVA) were present for the following three groups of response variables: (1) belowground biomass (BGB) and aboveground biomass (AGB); (2) shoot C/N ratio and root C/N ratio; and (3) shoot C/N, total chlorophyll and total soluble protein.  AGB, BGB, shoot/root ratio, root C/N ratio, shoot C/N ratio, total chlorophyll and total tillers all depended on the level of each of the three treatments (ANOVA, significant 3-way interactions).  Total leaf soluble protein content depended on the 2-way interactions of Light x Soil-N and Light x Moisture.  These results illustrate the high degree of plasticity P. arundinacea can exhibit and may help to explain its aggressive invasive behavior in wetlands with high levels of N deposition.