On the ecology of Thelypteris limbosperma — a synecological investigation of T. limbosperma-dominated stands in W Norway

The investigation is based on phytosociological and ecological analyses of T. limbosperma-dominated stands from different parts of W Norway. The distribution and floristical composition of the stands are related to different environmental parameters, such as climate, soil and topography. The data are analysed by numerical methods, of which two-way indicator species analysis (TWINSPAN), canonical correspondence analysis (CCA), and simple discriminant functions (DISCRIM) are the most useful. The broad-scale distribution of T. limbosperma stands is determined by climatic factors. Within its distribution area soil factors and human influence govern the floristic composition and development of different types of such stands. Based on the TWINSPAN classification 9 different stand types are distinguished.
The first major division of the TWINSPAN classification is mainly correlated with soil factors. Most of the stands growing on the richest soils are interpreted as representing regeneration stages after intensive human influence. Divisions at lower levels are well correlated with altitude and temperature conditions.
The stands are all characterized by low pH and base saturation. Some types are concentrated to certain geographical regions, indicating that both altitudinal and west-east-gradients are important in influencing the floristic composition of the different types. The investigations indicate that T. limbosperma has a rather narrow realised phytosociological niche. It is mainly concentrated to stands that are floristically most related to the poorest part of Vaccinio-Piceion communities. Occasionally it is also dominant in Alno-Padion and Lactucion alpinae communities.