Individual study: Response of fen violet Viola persicifolia to different management regimes at Woodwalton Fen National Nature Reserve, Cambridgeshire, England
Pullin A.S. & Woodell S.R.J. (1987) Response of the fen violet, Viola persicifolia Schreber, to different management regimes at Woodalton Fen National Nature Reserve, Cambridgeshire, England. Biological Conservation, 41, 203-217
Fen violet Viola persicifolia probably only persists at two localities in the UK, both in Cambridgeshire (eastern England). A study was initiated at one of these, Woodwalton Fen National Nature Reserve, to identify management regimes enabling perpetuation of violet populations. The first five years of monitoring data of populations under different management are presented.
Woodwalton Fen is divided into compartments of varying size (typically 200 x 300m or less), fen violet occurs in several, being monitored in five since 1982:
C46 A section was cleared of scrub in winter 1977/8 and cut (tractor and swipe) the following winter; in 1980, 475 violet plants.
C41 Sporadic scrub clearance between 1960-1971. From 1971 to 1978 the area was cut (tractor and rotary cutter) during winter. In 1979, a summer (July-August) cut and litter removal regime commenced (tractor and haycutter, hayturner and buckrake). In 1984 and 1985 cut material was raked by hand to reduce compaction; fen violet not recorded since 1959.
C54 In 1977, three open glades were created by scrub clearance and the peat leveled in 1979. Each glade was then cut and gathered every two autumns out of three. In 1980, 135 violets in the south glade, 220 in the central glade (third not monitored).
C55 In 1972 cleared of scrub. In 1977 cattle grazing (usually June to October) commenced. A cut (tractor and swipe) was usually undertaken in autumn and (since 1984) summer to remove rushes Juncus. In 1980 over 5,000 violets recorded in this and C58 (below).
C58 The last scrub clearance was in 1973, the peat surface was levelled and cattle grazing initiated in 1977 (as in C55) with autumn Juncus cutting.
Monitoring: Violet numbers were estimated each May-June. Abundances of all species over each compartment were estimated in June (Domin cover-abundance and Braun-Blanquet scales). Three permanent 1 m² quadrats were established (where violets present) in each compartment in 1982 and species composition within each recorded every June.
The maintenance of open fen with few competitive species appears important for fen violet. But whilst grazing or mowing regimes maintained open areas they encouraged competitive monocotyledons. By 1986, fen violet had disappeared from nine of the 18 quadrats and increased in none, only in compartment 46 did it still occur in all three. In the 10 quadrats in which it declined most or disappeared, the pattern of plant community change suggested replacement by competitive grasses, especially reed Phragmites australis. Other species declining were also typical of open fens with reduced competition. Management trials and monitoring continue.
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