A Study of the Relation Between Growth Form and Exposure on Monte Maiella, Italy

Abstract

In an earlier paper (Whitehead, 1951) the vegetation of the altipiano of Monte Maiella was described. A number of community types were distinguished, and it was established that there exists a relationship between plant height and the roughness of the ground surface. This was calculated from measurements of the wind velocity at different heights above ground level and expressed as the parameter Z0 (Whitehead, 1951). The difference in physiognomy of these communities was so striking that further investigations were carried out in 1951. The four community types referred to as areas A, E, G and H in the earlier work were selected as representing a graded series of communities varying from extreme exposure in A to maximum shelter in H. Quadrats were mapped in detail in each community, the height of each plant, the percentage cover and the growth form of each species being recorded. Growth form is here used in the original sense as proposed by Warming (1909) and as redefined by Du Rietz (1931). The anemometer used to determine Z0 was of the whirling-cup type (cup size 3cm.), electrically recording and made to a design modified from that described by Sheppard (1940). It was set up on the leeward edge of each quadrat, and the wind speed was measured simultaneously at three heights above the surface over a period of at least 3 min. The quadrats were so chosen that the vegetation for the operative distance (c. 30 m.) in the windward direction was as homogeneous as possible. The vegetation data for these quadrats are given in Table 1. The growth-form classification used in this investigation does not belong to any system in particular, but where similar growth forms have already been described, this is indicated in brackets in the list of definitions below: