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

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Abstract
Ramet demography and growth in a mature natural population of T. latifolia shoots in south-central Michigan, USA were studied. Records of 1981 individually-tagged shoots, oberved at 1- or 2-wk intervals for 2 growing seasons, included height, number of leaves and status of each leaf. Biomass was determined by harvesting replicate plots. Shoots emerged in 3 main pulses each year, resulting in 3 major cohorts. These pulses were timed similarly in 2 yr. The 1st cohort emerged in early spring, grew throughout the summer and senesced completely in late autumn. The 2nd 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 3rd emerged in late summer and early autumn; 78% (year 1) and 92% (year 2) of all its shoots resumed growth the following spring. Shoot mortality within 3 wk of emergence was minor (13%, year 1;6%, year 2). The ranges in live shoot density were very similar for the 2 years: 12.7-43.9 shoots in m-2 in year 1 vs. 11.2-42.9 shoots m-2 in year 2. In year 1, live shoots 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. Because the density of shoots growing from early spring was 60% greater in year 2 than in year 1, it was possible to evaluate the applicability of genet-based, density mediated competition theory (based on 8 expected consequences) to ramet-level populations. Density-mediated competition does not regulate ramet populations in mature stands of T. latifolia.