Ecology of wall vegetation

Abstract

In the preceding chapter the influence of human activities on the development of wall vegetation and the resemblances and differences in comparison with vegetation of rock crevices was pointed out. In this chapter, the ecological factors will be briefly surveyed. The environmental factors are separately dealt with, but they are of course not all independent of one another. They constitute an interrelated complex of factors that is, especially in respect of the subject under discussion, very insufficiently known. More extensive studies seem to be indicated, the more so since the results might have some practical significance. Each ecological factor can be considered on at least three different levels viz. from a geographical point of view (compare: distributional area or macroclimate), from a local point of view (compare: landscape or local climate), and at the level of the habitat (compare: microclimate). One could even go further and consider the patterns within vegetation stands separately, or the ecology of the individual species present, or even various developmental stages. In the present discussion the emphasis is on the conditions prevailing at the level of the site of a vegetation stand, but the relations to the conditions found at other levels are not altogether disregarded. The various levels are not only recognisable in relation to space, but also in relation to time.