Woodland grazing toolbox

Woodland grazing toolbox

6.1.3 Resilience to grazing of key field layer species

Grasses and sedges are more resilient to grazing, i.e. more able to re-grow following grazing, than are dwarf shrubs and trees. This is because the growing points of grasses are at the base of the leaves, close to the ground, so are less likely to be removed when the plant is eaten by herbivores.
 
Pollock et al. (2007) asked experts how plant growth was affected by grazing. The results are summarized in Table 1 below. Table 2, at the foot of the page, outlines information collated, largely from the published literature, on resilience to grazing.

Table 1. Expert opinion on resilience to grazing of key field layer plant species

Group

Species

Phenology

Mean plant response to grazing

Uncertainty

Grasses

Common bent-grass, Agrostis capillaris

E

3.3

0

Grasses

Sweet vernal grass, Anthoxanthum odoratum

E

3.0

1

Grasses

Sheep’s fescue, Festuca ovina

E

2.9

1

Grasses

Red fescue, Festuca rubra

E

2.8

1

Grasses

Viviparous fescue, Festuca vivipara

E

2.7

1

Grasses

Heath-grass, Danthonia decumbens

E

2.5

4

Forbs

Wood anemone, Anemone nemorosa

Sp-Su

2.5

3

Grasses

Mat-grass, Nardus stricta

E

2.4

1

Forbs

Harebell, (sometimes Bluebell in Scotland), Campanula rotundifolia

E

2.4

2

Forbs

Alpine lady’s mantle, Alchemilla alpina

Sp-A

2.3

5

Sedges

Common sedge, Carex nigra

E

2.3

2

Forbs

Heath bedstraw, Galium saxatile

E

2.3

1

Forbs

Yarrow, Achillea millefolium

E

2.3

2

Forbs

Tormentil, Potentilla erecta

Sp-A

2.2

1

Sedges

Pill sedge, Carex pilulifera

E

2.2

3

Grasses

Tufted hair-grass, Deschampsia cespitosa

E

2.2

2

Grasses

Purple moor-grass, Molinia caerulea

Sp-A

2.2

1

Rushes

Field wood-rush, Luzula campestris

E

2.2

3

Rushes

Heath rush, moor rush, Juncus squarrosus

E

2.2

3

Forbs

Bog asphodel, Narthecium ossifragum

Sp-A

2.1

2

Sedges

Deergrass, Trichophorum cespitosum

Sp-A

2.1

3

Sedges

Carnation sedge, Carex panicea

E

2.1

2

Grasses

Wavy hair-grass, Deschampsia flexuosa

E

2.0

1

Forbs

Wild thyme, Thymus praecox

E

2.0

2

Sedges

Harestail cotton-grass, bog cotton, Eriophorum vaginatum

E

2.0

3

Rushes

Soft rush, Juncus effusus

E

2.0

3

Sedges

Green-ribbed sedge, Carex binervis

E

2.0

3

Sedges

Common cotton-grass, Eriophorum angustifolium

E

2.0

3

Dwarf Shrubs

Blaeberry, bilberry, Vaccinium myrtillus

Sp-A

1.9

0

Sedges

Common yellow-sedge, Carex viridula ssp. oedocarpa (formerly C. demissa)

E

1.8

4

Dwarf Shrubs

Bearberry, Arctostaphylos uva-ursi

E

1.5

4

Dwarf Shrubs

Crowberry, Empetrum nigrum

E

1.4

4

Dwarf Shrubs

Heather, Calluna vulgaris

E

1.4

0

Dwarf Shrubs

Cowberry, Vaccinium vitis-idaea

E

1.4

3

Dwarf Shrubs

Bell heather, Erica cinerea

E

1.3

1

Dwarf Shrubs

Cross-leaved heath, Erica tetralix

E

1.2

2

Definitions of values used in Table 1

Phenology. ‘E’ = Evergreen, ‘Sp-A’ = Leaf canopy green Spring to Autumn, “Sp-Su” = Leaf canopy green Spring to Summer (Grime et al. 1990).

Mean plant response to grazing.High values for plant response indicate the plant re-grows well following grazing. Categories are:
1 - grazed plants grow a lot less than ungrazed plants
2 - grazed plants grow a bit less than ungrazed plants
3 - grazed plants grow the same as ungrazed plants
4 - grazed plants grow more than ungrazed plants

N.B. these values are for open hill communities, not woodlands. Individual species may respond differently in woodland shade; some species are unlikely to be encountered within woodland.

Uncertainty. The value in this column is the number of experts (out of 8) leaving the relevant question unanswered.

Table 2: Other information on resilience to grazing of key field layer plant species.

Common name

Latin name

Information

Source

Wavy Hair-grass,
Greater Wood-rush

Deschampsia flexuosa,
Luzula sylvatica

The effects of grazing and browsing on the continued persistence and abundance of particular species within the community can depend on competitive interactions with other plant species. For example Deschampsia flexuosa appears not to be heavily suppressed by grazing in scrub habitats on acid soils, possibly because of its relatively high shade tolerance allows it to retain its competitive edge….whereas in open moorland habitats its abundance is often much reduced by grazing. On the other hand, Luzula sylvatica appears to show the opposite behaviour, surviving and even spreading under moderate grazing when growing on the open hill but being much reduced by grazing in woodland and scrub.

MacDonald (1998)

Blaeberry/ Billberry,
Heather

Vaccinium myrtillus,
Calluna vulgaris

Vaccinium myrtillus is palatable but rhizomes provide protected buds and reserves which facilitate replacement of browsed shoots and make it slightly more resistant [resilient] to browsing than Calluna. Calluna is one of the most vulnerable dwarf-shrubs to heavy browsing pressure.

MacDonald (1998)

Common Bent-grass

Agrostis capillaris

Capable of establishing a dense low leaf canopy which under heavy grazing is rapidly renewed during late spring and early summer.

Grime, Hodgeson & Hunt (1990).

Cock’s-foot

Dactylis glomerata

Height of defoliation can be especially critical for orchardgrass (Dactylis glomerata L.), a bunch-type cool season grass that stores carbohydrate reserves for new regrowth in stem bases.
Be wary as info from North America.

Carlassare & Karsten (2002)

Blaeberry, Bilberry

Vaccinium myrtillus

Tolerant of sheep grazing

Grime, Hodgeson & Hunt (1990)

Blaeberry, Bilberry

Vaccinium myrtillus

Vaccinium myrtillus is less tolerant of sheep grazing than grasses

R.Thompson (personal communication)

Yorkshire Fog

Holcus lanatus

Not tolerant of close grazing or heavy trampling

Grime, Hodgeson & Hunt (2007)

Creeping Soft-grass

Holcus mollis

Does not persist in heavily grazed pasture, as its few robust shoot stems are eaten more quickly than they are replaced

Grime, Hodgeson & Hunt (1990)

Bracken

Pteridium aquilinum

Trampling is an important factor reducing bracken vigour.

MacDonald (1998)

References

Carlassare, M. & Karsten, H.D. (2002 Species contribution to seasonal productivity of a mixed pasture under two sward grazing height regimes. Agronomy Journal, 94, 840–50.

Grime, J.P., Hodgeson, J.G. & Hunt, R. (2007) Comparative plant ecology: a functional approach to common British species. Castlepoint press.

MacDonald, A.M., Stevens, P., Armstrong, H.M, Immirzi, P. & Reynolds, P. (1998) A Guide to Upland Habitats. Surveying Land Management Impacts. Scottish Natural Heritage, Battleby.

Pollock, M. L., Legg, C.J., Holland, J.P. & Theobald, C.M. (2007). Assessment of expert opinion: seasonal sheep preference and plant response to grazing. Rangeland Ecology and Management, 60, 125-135.