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Project description

Applied ecology and management of Eurasian watermilfoil (Myriophyllum spicatum) in Fall River. (04XU029)
Program Exotic Pests and Diseases Research Program
Principal
investigators
J.M. DiTomaso, Vegetable Crops, UC Davis
D.F. Spencer, Vegetable Crops, UC Davis
Host/habitat Wildland
Pest Eurasian Watermilfoil Myriophyllum spicatum
Discipline Weed Science
Review
panel
Urban Systems
Start year (duration)  2004 (Three Years)
Objectives Map the extent of Eurasian watermilfoil (Myriophyllum spicatum L.) in Fall River and quantify the role of disturbance (i.e. sediment deposition) in the invasion process. Such a comparison may identify possible factors limiting further spread.

Measure the seasonal changes in total nonstructural carbohydrate in root crowns and shoots of Eurasian watermilfoil populations in Fall River to optimize the success of plant harvest techniques and reduce the need for herbicide treatments.

Project
Summary
Eurasian watermilfoil (Myriophyllum spicatum) is one of the most invasive aquatic weeds in California. It is currently a problem in 44 states and Canada. Although typically a problem in lentic (still water) habitats, reports of its occurrence in flowing systems (lotic) throughout the West have become more frequent. In lotic systems, its growth contributes to increased flooding. We propose to investigate the occurrence, phenology, and growth status of Eurasian watermilfoil and to apply this information to its management in Fall River, Calif. We will map its distribution in Fall River and compare sediment and plant characteristics from invaded and uninvaded areas to determine potential limitations to its spread. Total nonstructural carbohydrate in plant tissues will be measured to identify periods when reserves are lowest. This information will be essential for timing mechanical harvesting operations.
Final report A Eurasian watermilfoil location and frequency was surveyed on the river. This was accomplished taking GPS-tagged digital photos on the stream bed using underwater viewing apparatus. These photos were analyzed in the laboratory, and Eurasian watermilfoil presence in the photos was recorded and linked to corresponding geographic coordinates. The data obtained from this survey was used to create a map of Eurasian watermilfoil on the river and to determine its frequency of occurrence in the river.

The in situ experiment in 2007 examined the growth of Eurasian watermilfoil in different sediments and at different locations in the river where the properties of the water column may differ. This was accomplished using a randomized split plot design. Whole plot treatments evaluated the effect of overall water column conditions at different locations in the river on the growth of Eurasian watermilfoil. Results indicated some restriction of growth based on overall water column conditions within the river. Sub-plot treatments evaluated the effect that sediment collected from different locations in the river has on growth of Eurasian watermilfoil. The results indicated no restriction of growth based on various sediments collected from the river.

Root crown stored TNCs were examined, and the annual cycle for 2007 was determined. This was accomplished with repeated sampling at two sites in the river at 3- or 6-week intervals. The samples were analyzed for root crown stored TNCs using the services of the ANR lab. The results indicated TNC minima during the months of June, July, and August.

Third-year
progress
Fall River is considered a world-renowned trout fishery. In August 2003, 3,000 acres of grazing land flooded when a levee collapsed on the Fall River. This occurred because of the slow water flow caused by Eurasian watermilfoil infestations downstream of this break. Since Eurasian watermilfoil appears to rely heavily on sediment-based nutrients for growth, we hypothesized that differences in sediment nutrient levels in infested and uninfested sites in the Fall River can be used to predict the areas susceptible to invasion.

In the third year of the study a distribution map of M.spicatum on the Fall River for 2006 has been developed. An additional distribution survey is planned for 2007. The biomass return from the 2005 nutrient addition experiments utilizing sediments from infested locations within the range of the plant and uninfested locations outside of the range of the plant indicated no nutrient limitation from the sediment regardless of collection site. In 2006 additional nutrient addition experiments were conducted both in the lab and in the field. The results of the 2006 experiments are still being analyzed. Analysis of 2005 root TNC content indicates a TNC minimum time closely following flowering time at site "Don Martin" and no apparent root TNC minimum at site "Whipple2." Root TNC continued to be monitored for 2006. Samples are still to be analyzed due to cost and the most efficient use of the TNC analysis is being determined.

Second-year
progress
Fall River is considered a world renowned trout fishery. In August 2003, 3,000 acres of grazing land flooded when a levee collapsed on the Fall River. This occurred because of the slow water flow caused by Eurasian watermilfoil infestations downstream of this break. Since Eurasian watermilfoil appears to rely heavily on sediment-based nutrients for growth, we hypothesized that differences in sediment nutrient levels in infested and uninfested sites in the Fall River can be used to predict the areas susceptible to invasion.

In the second year of this project, water quality measurements including temperature, specific conductance, photosynthetically active light (PAR) intensity values, pH, and dissolved oxygen (DO) were measured at seven sites on 18 dates from Dec. 21, 2004 through March 18, 2006. One of these sites was uninfested, one was infested without canopy breaching the surface, and five were infested with the canopy breaching the surface.

Additionally, plant tissue samples were taken from four of these sites to determine biomass allocation, TNC allocation, and community biomass distribution. Biomass allocation and community biomass distribution has been determined to date. TNC has yet to be completely analyzed due to cost. For these samples, we are waiting to determine the most efficient use of the TNC analysis, once we have analyzed our other results. Chlorophyll fluorescence was measured during the growing season at three of the four biomass collection sites. Relative electron transport rates (rETR) and rapid light curves (RLCs) were determined for the three sites: Whipple 1, Whipple 2, and Don Martin. Sediment samples were collected for nutrient analysis (N-P-K).

Camera transects upstream of spring creek bridge were obtained with the Remote Control Survey Boat on August 29 and 30, 2005. The data/footage is still in analysis. Nutrient addition experiments were conducted ex situ with soil and plant material extracted from the river with the objective of identifying N and/or P limitation. Response variables include biomass allocation, rETR, RLC, and N and P content of plant material.

First-year
progress
Fall River is considered a world-renowned trout fishery. In August 2003, 3,000 acres of grazing land flooded when a levee collapsed on the Fall River. This occurred because of the slow water flow caused by Eurasian watermilfoil infestations downstream of this break. Since Eurasian watermilfoilappears to rely heavily on sediment-based nutrients for growth, we hypothesized that differences in sediment nutrient levels in infested and uninfested sites in the Fall River can be used to predict the areas susceptible to invasion.

In the first year of this project, winter baseline values at four different sites on the Fall River were measured. These sites represent one uninfested and three infested Eurasian watermilfoil sites. In all four of these sites, dissolved oxygen concentration, water temperature, PAR (photosynthetically active radiation), pH, and specific conductance were determined on four dates from Dec. 21 to March 25, 2005. In addition, roots, lower stem, upper stem samples, and autofragments of living plants were collected and provided to the DANR Analytical Laboratory for analysis of Total Nonstructural Carbohydrates (TNC).

Sediment samples were also collected and will be used for nutrient analysis (N-P-K). Although the results indicate variation among the sample sites, no correlations with the level of infestation appear to be present. These results were expected since all measurements were taken during winter when biomass was low. These parameters will continue to be followed throughout the year and for the next two years.

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