14 



The goals of the monitoring program were to determine the best 

 method of tracking H. aquatilis populations over time, and to 

 determine population trends with respect to management practices. 

 Ocular population size estimates and percent cover of H. 

 aquatilis within ponds appears to be the most suitable measure 

 for several reasons: 1) it is an easy, fast, and simple way of 

 sampling a large number of ponds and, 2) it causes the least 

 disturbance within populations. The drawback to population 

 estimation by this method is the difficulty of determining exact 

 numbers of individuals when they are clumped, or in great enough 

 numbers to be difficult to count. 



Although cover gives a better measure of plant biomass than does 

 number of individuals present, the line-intersect measurements 

 are very time consuming for a small number of samples, and the 

 disturbance caused by reading the transects is significant. This 

 disturbance physically uproots the delicate H. aquatilis plants 

 and other species within the pond, and probably affects 

 subsequent transect readings. 



In 1989 and 1990, frequency measurements were also added to the 

 transect study of H. aquatilis . The frequency plots also 

 indicated a reduction in estimated population sizes from 1989- 

 1990, similar to but less severe than results given by the ocular 

 population estimates and line-transect study. 



In conclusion, for long-term monitoring of H. aquatilis . ocular 

 population size estimation is the recommended method of study. 

 Frequency measurements can also be used to quantitatively track 

 population shifts from year to year, but repeated wading along 

 the transect lines is required. 



As hypothesized by Lesica (1990), the large population size 

 fluctuations may be due to variation in pond drying times. 

 Additional data regarding the actual dates of pond drying, are 

 needed to more closely determine the nature of the observed 

 fluctuations. 



V. TRANSPLANT EXPERIMENTS 



METHODS: During September of 1989, soil plugs for transplant 

 experiments were obtained from two ponds containing dense 

 populations of H. aquatilis . The transplants were placed in four 

 ponds that appeared to contain suitable habitat for H. aquatilis . 

 but that had not been observed to support the species. Methods 

 for the transplant study are described in Shelly and Schassberger 

 (1990). The first year of quantitative monitoring of the four 

 transplant ponds was completed. The geographic locations and 

 elevations of the transplant ponds are: 



