Botany 45 



Extremely little trace remains to-day of the original vegetation of the 

 peat fen. Almost the whole area has been drained and brought under 

 cultivation: its character can be recognised only by the black peaty soil, 

 the uniform flatness, and by the deep ditches full of reeds {Phragmites 

 communis) that separate fields of potatoes, cereals, and sugar beet. The 

 continuous hawthorn hedges of the neighbouring land thin out abruptly 

 at the fen border. Rows of planted willows, and scattered clumps of 

 shelter trees, or small coverts, remain the only woody plants on the 

 cultivated fen. 



I. WiCKEN Fen 



One of the largest and best known areas of fen still uncultivated is 

 Wicken Fen, covering about one square mile, now in the hands of the 

 National Trust, and lying about lo miles to the north-east of Cambridge 

 on the very margin of the Fenland. 



The lodes, or main drainage channels traversing the area, converge at 

 Upware, and there they communicate through sluicegates with the River 

 Cam. The surrounding cultivated land has an entirely separate drainage 

 system at a much lower level. The water in Wicken Fen itself is conserved 

 in summer by the Upware sluices, and, in winter, excess water is run oflf 

 whenever possible. Thus the water level in the fen changes comparatively 

 little through the year, although the fen surface is about +7 ft. o.d. and 

 the surrounding land has become much lower through peat wastage 

 following draining.' 



Not only are the soil and water-level relations in the fens thus altered 

 from natural conditions, but peat-cutting has removed much of the fen 

 surface, and the fen vegetation has suffered a traditional system of crop- 

 taking maintained to some extent at the present day. Other human activities 

 also in less degree affect the vegetational cover: these include the cutting 

 and clearing of steep-sided lodes and drains, the consolidation and mowing 

 of "droves" and walks, the feUing of old fen scrub, and, to a small extent, 

 propagation of rare species of plants. 



I. The Primary Succession. In accordance with the accepted laws of the 

 succession of plant communities, shallow open water should progress by 

 natural accumulation of peat to shallower conditions, to a soil surface first 

 at water level and then above it, steadily moving towards a final stable 

 community, the climax. This succession is known as the primary hydro- 

 sere, and the climax in East Anglia may be supposed to be deciduous 

 woodland. Human activities have obscured the original simple hydrosere 

 relations at Wicken, but it seems clear that it probably differed httle from 



' See p. 186 below. 



