Clonal Growth in Typha Latifolia: Population Dynamics and Demography of the Ramets

Abstract

(1) Ramet demography and growth in a mature natural population of Typha latifolia shoots in south-central Michigan, U.S.A. were studied. Records of 1981 individuallytagged shoots, observed at 1or 2-week intervals for two growing seasons, included height, number of leaves and status of each leaf. Biomass was determined by harvesting replicate plots. (2) Shoots emerged in three main pulses each year, resulting in three major cohorts. These pulses were timed similarly in 2 years. The first cohort emerged in early spring, grew throughout the summer and senesced completely in late autumn. The second emerged in midsummer; 82% (year 1) and 76% (year 2) of these shoots senesced completely in autumn, while the remainder resumed growth the following spring. The third emerged in late summer and early autumn; 78% (year 1) and 92% (year 2) of all its shoots resumed growth the following spring. (3) Shoot mortality within 3 weeks of emergence was minor (13%, year 1; 6%. year 2). (4) The ranges in live shoot density were very similar for the 2 years: 12 7-43 9 shoots m-2 in year 1 v. 11 2-41-9 shoots m-2 in year 2. In year 1, however, live shoot density increased gradually throughout the growing season, while in year 2 a rapid increase in shoot density resulted in a density of 40.1 shoots m-2 by mid-May. This density was maintained throughout the second growing season. (5) Because the density of shootsv growing from early spring was 60% greater in year 2 than in year 1, we were able to evaluate the applicability of genet-based, density-mediated competition theory (based on eight expected consequences) to ramet-level populations. We conclude that density-mediated competition does not regulate ramet populations in mature stands of T. latifolia.