A comparative assessment of seedling survival and biomass accumulation for fourteen wetland plant species grown under minor water-depth differences

Abstract

The purpose of this experiment was to investigate the survival and biomass accumulation of wetland plant species under different water depths in controlled microcosms. In the greenhouse, two-weekold seedlings were randomly assigned to one of seven water-depth treatments (Ϫ6, Ϫ4, Ϫ2, 0, ϩ2, ϩ4, and ϩ6 cm relative to the soil surface) and allowed to grow for six months. Species included five perennial sedges, four perennial and one annual grasses, and two perennial and two annual forbs. Twelve of the species had their lowest biomass and lowest survivorship at water depths greater than 0 cm. The root:shoot ratio, however, did not change across water-depth treatments. Biomass accumulation differed by plant form (sedg-esϾforbsϾgrasses). Annuals had the greatest biomass values across the widest range of water depths compared to perennials. Of the fourteen plants tested, Lythrum salicaria (purple loosestrife), one of the two invasive, non-native species tested, had the greatest biomass at water depths from Ϫ6 to ϩ2, whereas Phalaris arundinacea (reed canarygrass), the other invasive, had comparatively small mean biomass values. Ranking of biomass between species was highly concordant between non-flooded treatments but not significantly concordant between flooded treatments indicating that plant species have distinct responses to flooding. This research suggests that newly established plant seedlings in wetland restorations should not be submerged, or if submergence is unavoidable, annuals and sedges may be more tolerant of prolonged flooding.

Effect of minor water depth treatments on competitive effect and response of eight wetland plants

“…The 475-ml cup was 14 cm in height; therefore the distances of water level to the bottom of the cup were 8, 10, 12, 14 and 16 cm from lowest to highest water depth. Fraser and Karnezis (2005) found that the percent of plant survivorship of five of the eight species at water depths greater than 2 cm above the soil surface was zero, and therefore water depth treatments above 2 cm were not included in the experiment reported here. Eight species tested across five water levels, plus five replicates, resulted in a total of 200 pots.…”

“…The other two species, P. arundinacea and Lythrum salicaria, were selected because they are also commonly found growing in the same freshwater marshes as the six native species but are non-native invasives (Apfelbaum andSams 1987, Thompson et al 1987). These eight species were also used in a previous study to measure the effects of minor water depth on biomass accumulation and survivorship (Fraser and Karnezis 2005).…”

“…Water-level fluctuation can cause distinct zonation patterns among plants van Eck et al 2004) and determine a specific assemblage of wetland plants (Weiher and Keddy 1995). Biomass accumulation and survivorship of individual wetland plants grown at different water depths can vary significantly between species, but when water level is consistently higher than soil level (i.e., flooded) plant growth and survivorship is generally limited (Visser et al 2000;Kercher and Zedler 2004;van Eck et al 2004;Fraser and Karnezis 2005). Another important factor contributing to the distribution and composition of freshwater wetland plant communities is competition (Wilson and Keddy 1986;Lenssen et al 1999;Budelsky and Galatowitsch 2000;Brose and Tielborger 2005).…”

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

“…Nevertheless, there is still a wide range of growth response between wetland plant species to flooding and to tolerance of different water levels (Fraser and Karnezis 2005;Mitsch and Gosselink 2007;Araya et al 2010). One aspect of hydrology that is rarely considered in wetland plant studies is the indirect effects of hydrology on water chemistry.…”

Effects of water levels and soil nutrients on the growth of Iris laevigata seedlings

“…The seedling establishment phase of the life cycle is crucial to successful propagation of any plant. Notably, the water level is the most important factor affecting seedling survival and the establishment of submerged plants (Nicol and Ganf 2000, Fraser and Karnezis, 2005, Kwon et al 2007). Water level determines wetland plant community composition and zonation because of different response and adaptation of species (Casanova and Brock 2000).…”