growth and vegetative spread of schizachyrium scoparium var. littoralis (poaceae) in sand dune microhabitats along a successional gradient

The architecture resulting from the iteration of modules during plant growth affects resource capture. Phalanx and guerrilla growth forms have been described as ends of a continuum regarding the spacing of modules in plants. In this study we investigated the growth form of the perennial, tussock-forming grass Schizachyrium scoparium Michx. var. littoralis (Nash) Hitchc. in three dune microhabitats at Fl Morro de la Mancha, southeastern Mexico: a mobile, a semi-mobile, and a stabilized site. We followed the growth of 15 genets at each site for two consecutive years and found that daughter-tussock formation was more frequent in the stabilized than in the semi-mobile or the mobile sites. Individual tussocks had a higher number of tillers in the mobile site than in the other two. Tiller production occurred within parental tussocks in the mobile site and in the form of daughter tussocks in the stabilized site. Reciprocal transplants suggested that phenotypic plasticity was responsible for the differences observed. Fertilization enhanced tiller production within parental tussocks but did not affect daughter tussock formation. Clearing experiments resulted in enhanced tiller production within tussocks. In these experiments, daughter-tussock production did not occur directionally towards nutrient-rich microsites. It appears that S. scoparium tillers are spaced at longer distances when resources are scarce and intraclonal competition is severe

growth response of six tropical dune plant species to different nutrient regimes

This paper reports the result of an experiment performed with six tropical dune species subjected to different nutrient regimes during 90 days in a greenhouse. Three species are characteristic of beach areas of central Gulf of Mexico (Ipomoea pes-caprae, Canavalia rosea. and Palafoxia lindenii) while the other three occupy mobile and semi-mobile inner dunes (Chamaecrista chamaecristoides, Trachypogon gouini and Schizachyrium scoparium). The nutrient treatments were: I) no nutrients, 2) nutrient rich, 3) predictable nutrient pulses, and d) unpredictable nutrient pulses. Plants grown in the absence of nutrients had smaller dry weight, leaf area, and relative growth rate than plants in the nutrient rich treatment. Nutrient scarcity resulted in a greater biomass allocation to roots than to aerial tissue. Plants subjected to nutrient pulses showed an intermediate response between the two other treatments, though pulse predictability had no significant effect on the growth variables measured. Species from the beach showed slower relative growth rates but more plasticity in their biomass allocation pattern (root/shoot ratio) than species fi om the inner dunes. All species are slow-growing and generally show growth responses characteristic of plants from infertile habitats. However, they show some phenotypic plasticity that enables them to respond to increased nutrient availability