HABITAT CHARACTERISTICS AND THE EFFECT OF VARIOUS NUTRIENT SOLUTIONS ON GROWTH AND MINERAL-NUTRITION OF ARNICA-MONTANA L GROWN ON NATURAL SOIL

Arnica montana, one of the character species of the replacement plant community Violion caninae on sandy acid humic podzol, is declining in the Netherlands since 1950. Locally, it is even extinct. This process of decline may be attributed to (i) autonomic succession; (ii) increas ed rate of acidification of the soil and/or (iii) change in competitiv e relations among Arnica and more productive plant species, such as th e successive dominant Deschampsia flexuosa. This paper examines the la st two hypothesized factors, supposedly being regulated by atmospheric input of N-input, by (a) describing the habitat characteristics of a seemingly still healthy individual-rich population of Arnica and (b) g rowing Arnica and Deschampsia in mixed humic podzol soil (mainly A1 ho rizon) fertilized with variously-composed nutrient solutions in order to assess the nutrient supplying capacity of the podzol soil and speci es-specific nutritional demands related to their respective growth cap abilities. The results suggest that an increased rate of soil acidific ation yielding extra supply of ionic Al and Mn is presumably of less i mportance. The implications of growth rate differences among Arnica an d Deschampsia as related to their nutritional demands are likely far m ore important. Arnica grows more slowly than Deschampsia in fertilized humus podzol. The latter species has a much more efficient use of nut rients. Furthermore, both species differ in K-nutrition if NH4+ is the dominant N-source, a situation normally occurring in acid podzolic so ils. Deschampsia processes the capability to adapt its metabolic nutri tion (avoiding nutritional imbalances) to a wide range of nutrient sup plies thereby maintaining a rather constant level of growth. Arnica, o n the contrary, lacks this capability. These results are discussed in the framework of competitive relations among co-occurring plant specie s in the plant community Violion caninae. It is concluded that mainten ance of Arnica and likely other character species of that alliance - a ll characterized by a low growth rate - will only be achieved when the plant community is properly managed by trampling, mowing or light lev els of grazing (low stocking rate). Of prime importance is to maintain a low and relatively open vegetation structure at a relatively low le vel of nutrient supply.