Individual study: Introduction of sheep grazing to control scrub encroachment at Little Scrubbs Meadow, Lincolnshire, England
Wilkinson R.B. (2000) From mowing to grazing – the control of scrub at Little Scrubbs Meadow. Enact, 16-18
Little Scrubbs Meadow is an unimproved herb-rich grassland, now a rare habitat in Lincolnshire (eastern England). The site, owned by the Forestry Commission, has been managed by Lincolnshire Wildlife Trust (LWT) since 1972. Invading scrub, mainly oak Quercus robur, had always been present but in 1993 it was evident that birch Betula, and willow Salix spp., especially goat willow S.caprea, were increasing. As a scrub control trial, in a test plot birch and willow scrub was sprayed with a herbicide (Garlon 4) which proved almost 100% effective. However it was impractical (due to cost) to treat the whole meadow in this way and also undesirable as there was some loss of floristic interest (although later recovering). Summer sheep grazing was introduced as a possible means of scrub control.
Earlier management: From 1972 to 1988, the meadow was mown each autumn with the cut material left. From 1989 to 1995 cutting was undertaken each autumn and the cut material baled and removed.
Monitoring: In November 1993, three transects were established across the meadow to monitor scrub encroachment and to identify if sheep grazing alone would control scrub, but if not, what combined treatment might best reduce it. On 21 July 1994, scrub in the transects was treated as follows:
Transect 1 - sprayed with Garlon 4 in water using a hand-held Hozelock pressurised horticultural sprayer;
Transect 2 - mown;
Transect 3 - left untreated (control).
Transect 4 (a second mown plot) was added in 1995 - mown once before grazing was initiated.
Grazing regimes: The meadow was split into three grazing plots (each about 0.37 ha). An ungrazed area around the periphery of the meadow continued to be autumn cut. In 1996, temporary sheep-netting was erected around grazing plots: Enclosure 1 (grazed with nine ewes and lambs from 3 August-20 September 1996); and in 1997 with six ewes and 11 lambs (reduced later) from 4 July-5 September. Enclosure 2 was grazed (five ewes and seven lambs) from 29 June to 30 August 1998 and 16 June to 1 September 1999.
Srub stem counts: On 21 July 1998, a stem count along each transect in a 1.5 m wide band was made.
Stem counts: There was a decrease in stem count of all five woody scrub species recorded (Q. robur 56%, Betula sp. 72%, Salix spp. 74%, hawthorn Crataegus monogyna 66% and ash Fraxinus excelsior 82%) after two years of summer grazing. In Transect 1 the count was consistently low after very effective spraying with Garlon 4, except for was a single persistent Salix (20 stems counted in 1998). A count on 21 July 1998 revealed a 6.2% increase in the control compared to the previous year (two summers without grazing).
Scrub height: On 21 July and 18 September 1998, height measurements were taken of a sample of oak (n= 25 and 11 respectively) and birch (n = 19 and 11) in Enclosure 1, and the ungrazed area (oak n= 26 and 1; birch n = 20 and 11) at the southeast end of the meadow (considered fairly typical of the meadow prior to grazing). On average, oak was nearly 30% taller (56 vs. 43 cm) and birch 108% taller (67 vs.32 cm) in the ungrazed area in comparison with the grazed area. In 1999, oak was 96% taller and birch 87% taller in ungrazed areas.
Conclusions: Sheep grazing significantly reduced the number of woody stems and the vigour of the invading tree/shrub species, and therefore appeared a good method of controlling scrub encroachment.