ESTIMATING THE ABUNDANCE OF SUBTERRANEAN PROPAGULES OF SUBMERSED AQUATIC PLANTS

1. Data on sample means (xBAR) and variances (s2) of propagule abundan ce for five types of aquatic plants growing in a variety of habitats w ere collected. The data set consisted of 379 values for xBAR and S2, b ased on 4942 individual sample units (sediment samples), drawn from th e literature or from data collected as part of this study. 2. Regressi on analysis relating log S2 to log xBAR yielded an equation which was solved for the number of sample units (n) required to achieve a given degree of precision. For precise estimates [standard error (SE) = 20% of xBAR] values of n between twenty-seven and 234 are required when pr opagule density is low (<200 m2), whereas eight to twenty-six sample u nits are required when propagule density is high (200-1000 m-2). For l arger SE (i. e. 30% of xBAR), n decreased by about 50%. Sampler area ( 20 to 1600 cm2) did not affect estimates of n. 3. Time required to col lect and process sediment cores (collected with either a 5, 10, or 15 cm corer) was approximately 7, 10, or 13 min, respectively. Combining this information with the required number of samples is useful in plan ning studies designed to measure changes in the abundance of undergrou nd propagules of submersed aquatic plants.