Using Dartmoor ponies in conservation grazing to reduce Molinia caerulea dominance and encourage germination of Calluna vulgaris in heathland vegetation on Dartmoor, UK

Paul Lunt,Malcolm Gibb,Jakob Leigh,Samantha Mcneil

doi:10.52201/cej18svsr7750

Abstract

The increasing dominance of purple moor-grass Molinia caerulea in heathland ecosystems in the UK is of growing concern due to its detrimental impact on plant and animal diversity on sites of nature conservation interest. The use of free-ranging ponies to reduce Molinia dominance was investigated from 2017 to 2019 within a 425 ha site on Dartmoor, UK. Salt blocks were used to attract the ponies to a Molinia-dominated area of heath within the site, away from their previously-preferred grazing areas. The impact of pony grazing was assessed by measurements of vegetation structure and plant species composition. The increased presence of ponies in the vicinity of the salt blocks increased the percentage occurrence of bare ground, reduced sward surface height, reduced percentage occurrence of Molina and increased the germination of heather Calluna vulgaris seedlings. The conclusions of this research are that salt blocks can be used to attract ponies to graze targeted areas of Molinia-dominated heathland. Through their grazing and trampling, ponies can reduce the dominance of Molinia, leading to an increase in the germination and establishment of heather seedlings.

Highlights

Heather-dominated upland heaths are of international importance for nature conservation, supporting a range of specialist invertebrate and bird species (Mitchell et al 2008)
There were two aims to this study: 1) examine whether salt blocks could be used to attract Dartmoor ponies to preferentially graze in selected Molinia-dominated areas, and 2) determine whether increased grazing and trampling of Molinia by ponies leads to an increase in germination and establishment of heather seedlings
Kruskal-Wallis non-parametric ANOVA was used to test for differences between treatments (Salt, No-salt, Control) for (i) bare ground (%), (ii) Molinia cover (%), and (iii) number of heather seedlings

Summary

BACKGROUND

Heather-dominated upland heaths are of international importance for nature conservation, supporting a range of specialist invertebrate and bird species (Mitchell et al 2008). A Priority Habitat listed in Section 41 of the NERC Act 2006 (JNCC 2008), has been in decline since the 1950s in the UK and Europe due in part to increased nitrogen deposition and rainfall (Sala et al 2000, Murphy et al 2019), leading to an increase in the dominance of Molinia (Milligan et al 2004) - a growing concern for nature conservation and habitat management (Chambers et al 1999, Mitchell et al 2008). One study on heathland in northern Spain (Aldezabal et al 2013), found that increasing the number of ponies present at the site reduced grass height in most cases. Cattle and ponies both consume grasses in preference to dwarf shrubs (Celaya et al 2011). There were two aims to this study: 1) examine whether salt blocks could be used to attract Dartmoor ponies to preferentially graze in selected Molinia-dominated areas, and 2) determine whether increased grazing and trampling of Molinia by ponies leads to an increase in germination and establishment of heather seedlings

Study Site The Bellever Forest site is located near

ACTION Experimental Design

Findings

DISCUSSION

The authors wish to thank Dru Butterfield and