ADAS WORKSHOP
Molinia Management in ESAs and the Uplands
Peak District National Park, Derbyshire
14-15th June 2000
Contents
1. Introduction3
2. Presentations4
2.1 The alleged recent rise to dominance of Molinia in moorland ESAs: obtaining new perspectives from palaeoecological techniques 4
2.2 Molinia management using sheep grazing preferences6
2.3 Molinia management in the uplands8
2.4 From Molinia back to purple: using modern machines9
3. Field trip - Howden Moor, Peak District National Park12
4. Discussion Groups12
4.1 Molinia in the uplands and within ESAs12
4.2 Species traits12
4.3 The influences of land management13
4.4 Desirable characteristics of Molinia14
4.5 Management techniques for Molinia14
4.6 Long-term management and sustainability16
4.7 Areas for further research17
5. Conclusions18
6. Acknowledgements19
7. Contacts19
1. Introduction
A two-day workshop was held in the Peak District on the management of Molinia caerulea (purple moor-grass) in Environmentally Sensitive Areas (ESAs) and the uplands. The workshop consisted of a day of talks followed by small group discussions, held at the Old Hall Hotel, Buxton. The second day included a field trip to view some Molinia management techniques in the Peak District National Park, courtesy of the National Trust.
The aim of the workshop was to discuss the idea of a recent rise in Molinia dominance, to place current Molinia-dominated vegetation types into a wider historical perspective, and illustrate techniques used to manage Molinia under different circumstances. The four presentations were:
- Prof Frank Chambers, Cheltenham & Gloucester College of Higher Education – The alleged recent rise to dominance of Molinia in moorland ESAs: obtaining new perspectives from palaeoecological techniques
- Dr Sarah Ross, ADAS Redesdale – Molinia management using sheep grazing preferences
- Prof Rob Marrs, University of Liverpool – Molinia management in the uplands
- Mr Geoff Eyre, Wm. Eyre & Sons, Derbyshire – From Molinia back to purple: using modern machines
Following the presentations, discussion groups of between 12-14 people were led by ADAS personnel, and used to identify:
- if Molinia always requires management
- species traits that increase Molinia’s competitive advantage
- management regimes that may encourage Molinia dominance
- when management might be necessary
- techniques used for successful management
- the appropriateness of techniques to different situations
- long-term, sustainable management
- areas for further research.
The field visit to Howden Moor, in the Peak District National Park, enabled participants to view the work carried out by Geoff Eyre and the National Trust, as presented in the final talk.
The following report outlines the four presentations given, summarises the findings of the workshop discussion groups and presents their conclusions. It also briefly outlines the field trip.
2. Presentations
2.1 The alleged recent rise to dominance of Molinia in moorland ESAs: obtaining new perspectives from palaeoecological techniques
Frank Chambers - Centre for Environmental Change and Quaternary Research, Cheltenham & Gloucester College of Higher Education
2.1.1 Introduction
Molinia has been identified as a ‘problem species’ potentially expanding into vegetation dominated by dwarf shrubs. It is thought to have replaced vegetation dominated by dwarf shrubs within recent years in some ESAs. This study aimed to assess the changes leading to Molinia dominance in two areas of heathland on Exmoor: (1) Larkbarrow - an area of ‘grey’ moorland (a mixture of Calluna, Vaccinium and Molinia); and (2) Lanacombe - an area of ‘white’ moorland dominated by Molinia. Similar studies were also undertaken on blanket mire in South and Mid-Wales.
2.1.2 Methods
This study uses palaeoecological techniques of plant macrofossil analysis, pollen analysis, spheroidal carboniferous particle (SCP) analysis and radiocarbon dating to assess the nature and timing of past vegetation change. Undisturbed vertical columns of peat were extracted using peat corers and peat monoliths, and analysed using samples taken 2cm apart, to give a temporal sequence.
2.1.3 Results for Larkbarrow – ‘grey’ moorland
The peat was highly humified, which prevented detailed analysis, but five main pollen analysis zones could be identified:
- Zone A (bottom of core; radiocarbon date 1360 +/- 60 BP) dominated by Gramineae suggesting grass heath around the Dark Ages (5th – 9th centuries AD). Molinia pollen is difficult to separate from other grasses so specifying grass species was not possible.
- Zone B dominated by Calluna indicating a dwarf shrub vegetation type developing around the medieval period (c. AD 1100-1300), when climatic conditions were apparently drier or warmer.
- Zone C also dominated by Gramineae with low Calluna levels. Elevated SCPs levels indicate a period at or just after the Industrial Revolution (from c. AD 1760).
- Zone D showed reduced Gramineae and increased Calluna implying a re-establishment of heather.
- Zone E (top most) had higher Gramineae and reduced Calluna representation. Appears to link to anecdotal evidence of Molinia replacing Calluna in recent decades.
2.1.4 Results for Lanacombe – ‘white’ moorland
Palaeoecological analysis of peat cores at Lanacombe showed an earlier period of Sphagnum and Eriophorum abundance succeeded by increased Calluna, which implied some drying out of the mire surface. The subsequent decrease in Calluna was accompanied by an increase in Cyperaceae and Gramineae. The uppermost part of the core contained the greatest Molinia macrofossil remains and the highest representation of charcoal fragments.
2.1.5 Results for Dryan Fawr, Elenydd, Mid-Wales - blanket mire
Macrofossil studies for one of the profiles suggested there was no direct correlation between increased charcoal occurrence and increased Molinia remains, in contrast to results at Lanacombe, Exmoor. Some Molinia remains were found at depth, relating to approximately 2000 years ago. There were, however, far more Molinia macrofossil remains toward the top of the profile, suggesting a recent rise in Molinia.
2.1.6 Discussion
This study has shown that the rise of Molinia does appear to be a recent feature at the two Exmoor sites studied. This seems to have been at the expense of earlier vegetation that was dominated by dwarf shrubs. At Larkbarrow (Exmoor) the associated increase in charcoal implies more frequent burning during this time of vegetation change. There are, however, indications at Larkbarrow that the Callunetum had originated in medieval times from grass-dominated heath which contained at least some Molinia. This highlights the antiquity of Molinia in upland moorland vegetation communities. At Larkbarrow, the apparent drying out of the vegetation, and rise of Molinia, may be connected with local drainage (David Lloyd pers. comm.).
2.1.7 Conclusion
Combining pollen analysis with macrofossil analysis and other palaeoecological techniques can provide information on past vegetation types in upland moorland areas. Linking vegetation history to past climate is important, and this could be achieved through the determination of peat humification and through the analysis of testate amoeba remains in the peat profile. Such data could then be considered when developing management plans for moorland and blanket mire. There is considerable scope for partnership research to this end.
2.1.8 Reference
Chambers, F.M., Mauquoy, D. & Todd, A. 1999. Recent rise to dominance of Molinia caerulea in environmentally sensitive areas: new perspectives from palaeoecological data. Journal of Applied Ecology 36: 719-733.
2.2 Molinia management using sheep grazing preferences
Sarah Ross - ADAS Redesdale, Otterburn, Northumberland
2.2.1 Introduction
Recent UK reductions in Calluna-dominated heathland have often been associated with a rise in competitive grass species, in particular Molinia caerulea. This has been attributed to various factors including changes in grazing management, changes in burning regimes and increases in N-deposition. Although some areas are now completely dominated by Molinia, with only remnant dwarf shrub species, this study focuses on moorland where there is a small scale mosaic of Molinia-dominated and dwarf shrub-dominated vegetation types.
Where Calluna still dominates in larger patches, burning is often used to rejuvenate the Calluna. The success of this management technique depends on the age of Calluna at burning, the level and timing of post-burn grazing, and associated species in the vegetation. If Molinia is present in the vegetation, burning can encourage Molinia to invade the burnt areas, possibly to the detriment of Calluna re-establishment. Clipping experiments on Molinia grassland in southern Scotland have shown that 3 years of summer light grazing (equivalent to a 33% reduction in annual Molinia leaf growth) reduced Molinia growth by 40% in the fourth year, while 3 years of heavy grazing (66% reduction in annual Molinia leaf growth) reduced Molinia growth by 78% in the fourth year (Grant et al. 1996). Similar grazing levels on mixed Calluna / Molinia moorland may control Molinia regrowth after burning, and so enhance Calluna re-establishment.
This experiment aims to investigate the effect of these two levels of summer-only grazing on two stands of heather that have been burnt at different ages. The success of these summer grazing regimes as potential management techniques to control Molinia while enhancing Calluna re-establishment is assessed.
2.2.2 Methods
Two stands of heather, one 8 years old the other 22 years old, were burnt in 1996. Plots (20 m x 60 m) were established with a high level of grazing (Molinia kept at 6 cm length = 66% off-take of annual growth) and a low level of grazing (Molinia kept at 12 cm length = 33% off-take of annual growth), and an un-grazed control. These grazing levels were based on studies carried out in southern Scotland on Molinia regrowth after clipping or cattle grazing, as described in section 2.2.1 (Grant et al., 1996). Grazing was applied from 1st June to 31st August, and sheep numbers on each grazed plot were manipulated weekly to ensure Molinia was kept at the desired length. Post burn vegetation re-establishment was monitored each year until 1999, using 1m2 quadrats and assessing Calluna and Molinia percent relative frequency and Calluna regeneration as indicators.
2.2.3 Results
1. Percent relative frequency of Molinia and Calluna
8-year-old heather stand: under both high and low grazing regimes Molinia cover was seen to decrease by at least 50%. There was no reduction in Molinia the un-grazed control. There was an increase in Calluna cover under low grazing and the control, but little if any increase under high grazing.
22-year-old heather stand: Molinia cover increased by approximately 50% in the un-grazed control, but decreased under both high and low grazing. Calluna cover showed a decline under high grazing, but increased slightly under lower grazing and also in the control.
2. Calluna regeneration
8-year old heather stand: data not presented.
22-year old heather stand: In the un-grazed control Calluna seedlings showed an increase in the autumn of the first year (October 1996), up to a mean of approximately 50 seedlings per 1m2, but declined thereafter to approximately 20-25 seedlings in the final assessment in April 1998. Under high grazing there was very little regeneration at all, often showing fewer than 10 seedlings per 1m2. Under lower grazing there was an increase in the first autumn to approximately 45 seedlings per 1m2, which was sustained into the second and third year assessments (August 1997, October 1997 and April 1998).
2.2.4 Discussion and Conclusion
Summer-only grazing appears to be effective in controlling Molinia after burning these mixed moorland areas. At higher levels of summer-only grazing (equivalent to 66% off-take of annual Molinia growth) Molinia was effectively controlled, showing approximately a 50% reduction in percent relative frequency. There was, however, some grazing on Calluna, and little if any increase in percent relative frequency. The lower level of summer-only grazing, equivalent to approximately 33% off-take of Molinia annual growth, was similarly effective in reducing Molinia cover, but also increased Calluna percent relative frequency by approximately 50%. Application of these summer-only grazing at a larger scale is required to fully assess the usefulness of this technique as a management tool for controlling Molinia while enhancing Calluna re-establishment after burning.
2.2.5 References
Grant, S.A., Torvell, L., Common, T.G., Sim, E.M. & Small, J.L. 1996. Controlled grazing studies on Molinia grassland: effects of different seasonal patterns and levels of defoliation on Molinia growth and responses of swards to controlled grazing by cattle. Journal of Applied Ecology 33: 1267-1280.
2.3 Molinia management in the uplands
Rob Marrs, Pamela Todd*, Anna Milligan, John Phillips* and Phil Putwain
Applied Ecology Research Group, University of Liverpool; *The Heather Trust, Kippen, Stirling
2.3.1 Introduction and Methods
Molinia is increasingly perceived as a problem species in moorland areas. The control of this species on ‘white’ and ‘grey’ moorland often involves herbicide application to reduce Molinia cover and vigour, allowing dwarf shrubs to re-establish. Several types of herbicide were screened in the laboratory for their effect on Molinia and Calluna. Field trials of selected herbicides were also carried out on both ‘white’ and ‘grey’ moor. Different application methods for herbicide were also assessed in the field, including aerial spraying and weed wiping.
2.3.2 Results for laboratory herbicide screening
Several herbicides were tested, including Roundup, Clethodim, Laser, Citadel, Fusilade, Pilot and Checkmate. For each herbicide the effective dose for a 50% reduction in Calluna or Molinia growth (ED50) was assessed from laboratory trials. Data were highly variable and not all herbicides showed a typical sigmoid ED50 response curve. Roundup, Pilot and Checkmate all showed reductions in Molinia growth, but Roundup also showed significant damage to Calluna.
2.3.3 Results for field application trials using a weed wiper
Tartrazine dye was used as a substitute for herbicide to compare herbicide deposition rates between weed wiping (once or twice) and spraying. Dye application to different depths of the vegetation was assessed. On ‘white’ moorland, spray did not reach the base of the tussocks, while weed wiping (particularly twice) gave better deposition rates. On ‘grey’ moor, spray application was more effective than weed wiping, reducing the re-growth of Molinia tillers. The timing of herbicide application was important; May application was least effective, July application was most effective, whilst September was also effective but there was more damage to Calluna.
2.3.4 Results for herbicide field trials
Plot trials, to control Molinia and re-establish Calluna, were carried out on moorland areas in Exmoor, North Peak and the Yorkshire Dales. The treatments included combinations of burning, cutting, grazing, herbicide application (Roundup), litter removal and seed application. Herbicide application gave a significant reduction in Molinia, with low application rates achieving the same level of control as higher application rates. After 5 years there was no difference between the control and the herbicide application plots. Herbicide followed by Calluna seed application helped to increase Calluna density.
2.3.5 Discussion and Conclusion
On ‘grey’ moorland herbicide controlled Molinia in the short term, and glyphosate appeared most effective although it had negative effects on Calluna. Graminicides, which specifically target grasses, can also be effective at reducing Molinia, but they are not at the present time licensed for use in moorland areas. Weed wiping can be an effective herbicide application method in ‘grey’ moorland areas. On ‘white’ moorland Calluna appeared to need some assistance to re-establish using, for example, litter disturbance or seed application. Careful herbicide application may provide a ‘window of opportunity’ in which additional heather restoration techniques can be more effectively implemented.
2.3.6 References
Todd, P.A., Phillips, J.D.P., Putwain, P.D. & Marrs, R.H. 2000. Control of Molinia caerulea on moorland. Grass & Forage Science 55: 181-191.
Milligan, A.L., Marrs, R.H. & Putwain, P.D. 1997. Control of Molinia caerulea (L.) Moench in upland Britain. British Crop Protection Conference (Weeds) 1997: 679-680.
Marrs, R.H. 1984. The use of herbicides for nature conservation. Aspects of Applied Biology 5: 265-274.
2.4 From Molinia back to purple: using modern machines
Geoff Eyre – Wm. Eyre & Sons, Hope Valley, Derbyshire
2.4.1 Introduction
In past decades Molinia-dominated and mixed moorland areas have often been repeatedly burnt in spring to encourage spring grazing for sheep and cattle. This has led to monocultures of Molinia in some areas, resulting in little wildlife diversity. Restoring Molinia monoculture areas to a more diverse mix of moorland plants can, in the long term, bring many benefits.
2.4.2 Controlling Molinia with grazing animals
In mixed Calluna/Molinia areas, where some remnant dwarf shrubs remain, controlled seasonal grazing can open the canopy, encourage light penetration, and benefit any emerging heather seedlings. However, the digestibility of Molinia declines over the season, and the next available food source for grazing animals is typically the green shoots of heather. Regular (daily) inspection of the ground is needed to ensure grazing animals are removed as soon as they begin to graze Calluna in preference to Molinia. In addition, uncontrolled winter grazing by rabbits and hares can inhibit the regeneration of heather.
2.4.3 Molinia control using modern machines
Molinia is thought to have replaced large areas of dwarf shrub dominated heath over the last century, and if there is a desire/need to restore this heath, time- and cost- effective restoration methods need to be developed. Some management options can begin to be drawn together from work in the High Peak, with the development of techniques that encourage Eriophorum, Deschampsia, Vaccinium and Calluna re-establishment, and discourage Molinia re-invasion. To achieve the desired results full use has been made of modern machinery and crop husbandry techniques, along with regular inspection and quick action to address any problems.
2.4.4 Restoration techniques used
- A tractor mounted flail – a design developed from hedge cutters, for cutting Molinia tussocks. Flails require 15 horsepower for each foot of cut, for example an 8’ cut behind 120hp tractor. Cutting can take place in early spring, and as a general rule cuts should be higher on wetter ground. On wetter ground cutting the tops off Molinia tussocks provides a good Calluna seedbed. On drier ground cutting closer to the ground ensures moist conditions for the Calluna seed. The Molinia will need a second cut in summer, and possibly a third cut the following spring. During this time sheep can be grazed on the area to help consolidate the remaining plant material. If necessary, the first application of Calluna seed can take place after the second cut (summer), and sheep can remain on all winter. A second application of seed can be put on in the following spring, with the sheep left on to graze Molinia re-growth. Sheep should be excluded no later than the end of June, and remain off for two to three years, or until plants have flowered. After this time a mixture of Calluna and Molinia should have developed, which then requires careful long term management, with restricted winter grazing.
Advantages of the flail: