Factors affecting growth of Ptelea trifoliata seedlings

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Abstract
With the limited supplies of nutrients and water in the Lake Michigan sand-dune habitat [near Saugatuck, Michigan, USA], environmental factors which affect seedling growth also strongly affect survival. Soil temperature, rainfall frequency, nutritional status of the soil and species-specific water relations were studied as to their effects on the growth of P. trifoliata L. seedlings. Root development was examined carefully since previous studies had indicated that root growth sufficient to reach a permanent water supply was critical for survival. Growth was stimulated by the temperature and soil-moisture conditions which occur in early spring. Fertilization, especially N and P, strongly stimulated growth. In addition, P. trifoliata produced adventitious roots when buried. Survival of seedlings was not enhanced by any adaptation to conserve water because plant resistances to water flow were typical of mesic species. Consequently, high transpiration rates occur in the sand-dune habitat, increasing the importance of good root growth. If adequate water is available, the high transpiration rates may help the seedling tolerate the high temperatures of this environment. Thus, P. trifoliata seedlings possess no single characteristic that explains their ability to survive in the rigorous dune habitat, but possess many characteristics that contribute to their success.