The relationship between soil water and the growth of higher plants was partly dealt with in Section 3.5.1. Water is an important growth factor for trees as well as for other plants. Both excess water and drought are limiting factors for tree growth. In the case of virgin mires, excess water in the substrate checks root growth and microbial activity, and may lead to unfavourable biochemical phenomena. One of the most important goals of draining is therefore to adjust the water content of the soil to a level which ensures sufficient aeration (Päivänen 1973b). As discussed by Heikurainen (1964) some scientists speak about removing excess water (Multamäki 1936), some about lowering the groundwater table (Lukkala 1929), and others claim that the purpose of drainage is to increase the movement of water (Huikari 1959b). The purpose of draining may also be to increase the depth of rooting and so reduce the risk of windthrow. This is especially the case in Great Britain (Pyatt 1990a).
KeywordsDrainage Ditch Sedimentation Pond Ditch System Drainage Depth Forest Drainage
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