Effects of Competition, Salinity and Disturbance on the Growth of Poa pratensis (Kentucky Bluegrass) and Puccinellia nuttalliana (Nuttall’s Alkaligrass)

Abstract

Saline wetland and ponds in Canada can be found in arid and semi-arid regions where evaporation exceeds precipitation. An increase in salinity can reduce plant growth and affect competitive interactions between plants. A field experiment and a greenhouse experiment tested the effects of salinity and competition on the growth of two wetland plants, Poa pratensis (a glycophyte) and Puccinellia nuttalliana (a halophyte). For the field experiment, seedlings of Poa pratensis and Puccinellia nuttalliana were transplanted to six sites (two highly saline, two moderate, and two at low salinity) with and without plant neighbours. All sites were affected by high mortality and poor growth of the transplants. Survivorship was greater for plants grown alone. Biomass of plants grown alone was greatest at one of the moderate saline sites. The greenhouse experiment tested the response of P. nuttalliana and P. pratensis in a factorial design with 70 combinations (2 species × 7 salinity × 5 competition) replicated 6 times. Both of the species’ biomass was greatest when grown alone without salt. Species, salt type and competition had greatest effect on survivorship. Puccinellia nuttalliana displayed a greater degree of salt tolerance than P. pratensis. Re-growth after clipping was suppressed at higher salinities. Our results indicate that the interactions between plant species, salinity and clipping (or grazing) can affect the potential quality and quantity of forage for livestock and wildlife.