Grassland: Selecting indicators of success for grassland enhancement (TIN050)

Cover of invasive trees and shrubs

Scrub is often of wildlife value in its own right and it may be of high environmental value as defined in the FEP (see feature code V05), even if it has been recorded as general scrub in the FEP (ie FEP feature V04). Even scrub that does not fit the V05 criteria is part of the grassland system and can make a valuable contribution to the wildlife value of a grassland site.

When considering how to manage scrub and set the targets for future scrub cover, a number of factors need to be taken into account. These include how long the scrub has been present on any particular part of the site, because it will affect the vegetation that is likely to develop if the scrub is removed. If the scrub has been present for a long time then it is unlikely that grassland of high quality will be produced by clearing it. Younger scrub with remnants of grassland under it is more likely to produce grassland of worthwhile quality.

There might be sites, particularly those in restoration and certainly those in creation options, where there is too little scrub. The target could therefore be to increase scrub to the desired levels.

If the scrub is composed of various species, of various ages in an irregular pattern with good transitions to grassland and lots of edge it is considered to be of high wildlife value. Low value scrub is composed of a single species growing in an even-aged block. Most scrub is somewhere between high and low value, and where scrub work is proposed it is worth seeking ecological advice and producing a management plan.

Agreement year

The quantity of scrub on a site at the start of the agreement is not necessarily related to the quality of the grassland and hence not related to whether it is in restoration or maintenance. Grassland creation sites are likely to be starting from arable so they are unlikely to have scrub.

If it is decided that there is too much scrub on the site then it might be best to gradually reduce the cover over a number of seasons rather than drastically reducing it in year 1. However, for practical reasons it might be necessary to carry out work in substantial blocks. The year by which the desired scrub cover is achieved can be altered depending on which approach is taken.

Species in text

On many sites a small number of woody species, often a single species, make up the bulk of the scrub while several others are present as scattered or lone individuals. If reducing the overall cover of scrub you can retain the diversity of species by picking out the scarce species on the site for retention (not just the notable species listed in the indicator). For some sites an adviser may wish to specify particular problem species. Typical problem species include various cotoneasters, holm and Turkey oaks, particularly on limestone sites in the south.

Sites with juniper, box (native sites), bog myrtle, creeping willow and other notable scrub species are of high value and need particular care, as do sites with rare species associated with scrub (e.g. Dartford warbler in gorse, dormouse especially where there is hazel). All scrub above 600 m in altitude is of high value as is scrub on peaty soils with alder buckthorn and various willow species.

Frequency/Density/% Cover

This depends on the cover at the start of the agreement, on the value of the scrub and the quality of the grassland as well as on which species are associated with the scrub and what their requirements are. Deciding on how much scrub is appropriate is a balancing act. Where the scrub is not of special wildlife value 5% cover of the grassland area is given as a default. Some species which are desirable and beneficial are excluded from this assessment of cover, though if they are present then the scrub is likely to be of high wildlife value.

In situations where a hay crop is regularly taken scrub is likely to be restricted to field margins, and the cover value in the areas cut for hay should be close to zero in normal circumstances (otherwise it would not be a hay meadow!). On sites with high quality grassland you would not normally want scrub to encroach beyond its current extent, unless the scrub is a high value species and the scrub cover currently low.

Landscape/Historic Considerations

No new scrub should be allowed to encroach on features of historic environment interest as most such features can be damaged by the roots of woody species. It may be appropriate to remove all the scrub on such features, leaving stumps treated but in situ. If the site has very high value scrub or is a SSSI then consult an ecologist and a Historic Environment adviser. See feature detail information and the ELS scrub management option for more information. If you are uncertain as to the extent of such features please consult your regional Historic Environment advisor.

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