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Title: Temperature-dependent models of Zannichellia palustris seed germination for application in aquatic systems

item Bytnerowicz, Thomas
item Carruthers, Raymond

Submitted to: Environmental and Experimental Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/22/2014
Publication Date: 6/3/2014
Publication URL:
Citation: Bytnerowicz, T.A., Carruthers, R.I. 2014. Temperature-dependent models of Zannichellia palustris seed germination for application in aquatic systems. Environmental and Experimental Botany. 104:44-53.

Interpretive Summary: Horned pondweed, Zannichellia palustris, is a common native plant species that grows in many lakes and streams throughout North America and the world. It is a key natural component of the vegetation in the Fall River of Northern California where it serves as one of the primary producers that acts as the base of a complex food chain that supports a world famous trout fishery in the area. The Fall River runs through an extensive agricultural area that draws water from this tributary and in recent years it has been invaded by exotic plants such as Eurasian watermilfoil. Efforts to reduce milfoil growth and displace it with more highly desired species such as Z. palustris have required detailed biological studies on many different aspects of this native species life cycle, including its germination characteristics and dynamics. This current study uses a combination of statistical analysis and computer simulation modeling to assess Z. palustris seed germination characteristics as they relate to stream temperature and then predicts when seeds will actively germinate in the stream following production and or managed seeding events. This is helpful to wetland managers who are working to restore this river from invasive species infestations and to replant areas destroyed by heavy sedimentation. Seed germination and seedling establishment is extremely important in re-vegetating disturbed habitats and allows native plants to again serve as the bases for food webs that support native fish and other fauna in the area.

Technical Abstract: The germination characteristics of Zannichellia palustris seeds collected from the spring-fed Fall River of Northern California were investigated across a range of constant temperatures from 4.2 to 40.8 ºC. Germination experiments were conducted on freshly produced and collected seeds. Seeds germinated at all temperatures except 40.8 ºC, with the maximum germination fraction observed at 24.4 and 29.5 ºC with 69 ± 5 and 73 ± 3 % total germination, respectively. The cumulative spread in germination over time was determined to be log-normally distributed through modeling comparisons made using a probit function for both individual temperatures and for temperature data that was converted to thermal units, through linear regressions of subpopulations. Further analysis used more complex multi-linear models and non-linear models such as the Logan Type III Biophysical Model to relate changes in temperature to the rate of seed germination. These statistical models were then incorporated into a computer simulation model constructed in the USDA-ARS Hermes Modeling System. This simulation model uses constantly changing temperature conditions measured from the river to estimate seed germination patterns in multiple locations along the Fall River and across different seasons within the year. Clear patterns of seed germination were established in the upper river reach, mid-river reach and downstream where the Fall River joins the Tule River. The full pattern of seed germination was simulated and will assist land and waterway managers in implementing re-vegetation efforts in the most efficient ways throughout the watercourse.