Some Experimental Aspects of the Calcicole-Calcifuge Problem: I. The Effects of Competition and Mineral Nutrition Upon Seedling Growth in the Field

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Abstract
The two calcicoles Scabiosa columbaria and Asperula cynanchica, and the two calcifuges Holcus mollis and Galium saxatile are known from field observation to be highly exclusive in their distribution. To discover the primary factors determining this exclusiveness, seed of each species was sown into an acid greensand, a calcareous sand and a chalk soil, both in the presence and absence of existing vegetation. Various combinations of calcium (as CaSO4 2H2O), potassium (as KC1) and phosphorus (as Ca[H2PO4]2 H2O) were added to the soils. Results were expressed as percentage seedling survival, plant dry weight, and calcium, potassium and phosphorus per plant. There was a crucial phase during seedling establishment when chemical factors exerted a dominant influence compared with the physical nature of the soil and with competition. The nature of this chemical influence was considered.