Action: Shorten livestock grazing period or control grazing season in forests
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- One replicated, controlled study in Spain found that shortening the livestock grazing period increased the abundance and size of regenerating oak trees.
- One paired-sites study in Australia found no effect of shortening the livestock grazing period on native plant species richness.
- One replicated study in the UK found that the number of tree seedlings was higher following summer compared to winter grazing.
Reducing livestock grazing can be done by reducing the number of animals per area unit or by shortening the grazing period during the year. These two methods may vary in their effects on tree regeneration and forest biodiversity, for example if the livestock is removed in critical seasons of seed production and germination.
Supporting evidence from individual studies
A replicated study in 1986-1993 in temperate woodland in the UK (Hester, Mitchell & Kirby 1996) found thatusingsummer instead of winter grazing increased the number of tree seedlings. The number of seedlings was higher following summer (8-17/100 m2) compared to following winter grazing (4-6/100 m2). Six summer (May-October) and six winter grazing (October-May) plots were established in 1986. Seedlings (>1 year old, <30 cm diameter at breast height) were monitored in 2003 in 20 quadrats (10 × 10 m) within each plot.
A paired-sites study in 2006 in temperate woodland in south-eastern Australia (Dorrough et al. 2012) found no effect of different grazing regimes on native plant species richness. The number of native plant species/plot was similar between treatments (continuous-grazing: 18; rotational-grazing: 15). Monitoring was in two continuous-grazing (livestock had unrestricted access) and two rotational-grazing (<56 days grazing followed by >21 days with no grazing) plots (1 ha) in each of 12 sites (a total of 48 plots).
A replicated study in Mediterranean open woodland in Spain (Carmona et al. 2013) found that seasonal grazing increased the abundance and height of oak saplings compared to permanent grazing. Percentage cover of young oaks (seasonal grazing: 9%; permanent: <1%) and young oak height (seasonal: 80 cm; permanent: 40 cm), and density of young and old oak saplings (seasonal: 100-80 saplings/ha; permanent: 20 saplings/ha) were higher with seasonal than permanent grazing. Two to six sites were located in each of nine permanently grazed areas (grazed throughout the year) and nine areas grazed seasonally December to May. Each area was 20-480 ha and had been grazed in the ten years before treatment. Monitoring was in four 3 × 3 m plots in each site.
- Hester A., Mitchell F. & Kirby K. (1996) Effects of season and intensity of sheep grazing on tree regeneration in a British upland woodland. Forest Ecology and Management, 88, 99-106
- Dorrough J., McIntyre S., Brown G., Stol J., Barrett G. & Brown A. (2012) Differential responses of plants, reptiles and birds to grazing management, fertilizer and tree clearing. Austral Ecology, 37, 569-582
- Carmona C.P., Azcárate F.M., Oteros-Rozas E., González J.A. & Peco B. (2013) Assessing the effects of seasonal grazing on holm oak regeneration: Implications for the conservation of Mediterranean dehesas. Biological conservation, 159, 240-247