Manipulation of sheep grazing patterns on upland...

Appendix 5

The characterisation of changes in spatial and temporal sheep grazing patterns in relation to vegetation characteristics and

supplementary feeding on moorlands

Project BD 1216.

Final Scientific Report

September 2002

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The characterisation of changes in spatial and temporal sheep grazing

patterns in relation to vegetation characteristics and supplementary

feeding on moorlands

Sarah L. Hetherington, Hester A. Lyons*, Sarah M. Gardner* and Alison E. Riding*

ADAS Pwllpeiran, Cwmystwyth, Aberystwyth, Ceredigion, Wales, SY23 4AB, UK.

*ADAS Woodthorne, Wergs Road, Wolverhampton, WV6 8TQ, UK.

Running title: Sheep grazing patterns on upland moor

Author for Correspondence

Dr Sarah L. Hetherington

ADAS Pwllpeiran

Cwmystwyth

Ceredigion

SY23 4AB

Tel:- (01974) 282229

Fax:- (01974) 282302

E-mail:- [email protected]

Word Count:

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Summary

1. The spatial and temporal distribution of key moorland species and their associated

level of sheep grazing were assessed at four times during the year and the temporal

changes determined. The effect of the introduction of supplementary feed on the level of

grazing at the localised and moorland management unit scale were investigated.

2. The pattern and intensity of grazing were similar at both sites during Spring and

Winter, with the majority of the grazing concentrated in a few areas. At both sites, the

most heavily grazed areas during these periods were coincident with the areas with the

highest density of Vaccinium myrtillus.

3. Temporal changes in the distribution of grazing across each moor were determined by

quantifying the number of quadrats that maintained or changed their grazing status.

During late spring, a large percentage of quadrats which contained Vaccinium myrtillus,

Molinia caerulea and other species changed their grazing status from ungrazed to grazed.

During summer/autumn the percentage of grazed C. vulgaris quadrats increased markedly

on Site 1 but not on Site 2 where the feed blocks had been present during the spring. This

observation reflects to some extent differences in the vegetation composition of the two

sites, Vaccinium myrtillus being more abundant on Site 2 than on Site 1, but may also

reflect an on-going effect of the feed block treatment.

4. The addition of supplementary feed in the form of feed blocks was applied for a period

of six weeks in the late spring and the autumn. Feed blocks affected the spatial

distribution of grazing in the spring. Results of small scale sampling determined that there

was an increase in Vaccinium myrtillus grazed and the level of total grazing within 30 m of

the block but there was no relationship with distance from the blocks at this localised

scale. However, at the moor-scale there was a relationship with distance from the feed

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block with an increase in the proportion of Vaccinium myrtillus grazed and the total level

of grazing with decreasing distance from the block.

5. Similar relationships at both the moor- and local-scale were observed for the

abundance of sheep droppings.

6. These results show that feed blocks can be used to manipulate sheep grazing patterns.

Therefore, during periods when vegetation communities of interest are vulnerable to

grazing feed blocks place greater than 80 m away can reduce grazing in these areas and the

implications for moorland management are discussed.

Key-words: Grazing pressure; Self-help feed blocks; Semi-natural rough grazings with

heather; Upland vegetation communities.

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Introduction

Heather moorlands are predominantly man-made features of uncultivated upland regions

in the UK (Gimingham 1988; Bargett et al. 1995). They have been maintained for

centuries by management practices such as grazing and/or burning which resulted in the

removal of nutrients from the system that could favour more competitive species

(Gimingham 1989). They are recognised as an important habitat in terms of their ecology

and conservation value (Thompson et al., 1995; Anon 1995). In addition these moorlands

are important assets to the rural economy providing valuable grazing on poor soils

(Gimingham 1989; White 1996). The occurrence of uneven patterns of grazing across

upland grass/heather moor has been well documented (Clarke et al., 1995a,b; Hester &

Bailie 1998; Hetherington 2000). Such patterns arise from the patchy distribution of plant

communities across a moor and from herbivore preferences for specific plant species

and/or grazing areas.

The introduction of the Less Favoured Areas Directive in 1975 together with

economic pressures and agricultural subsidies has resulted in major increases in the

number of sheep (Ovis aries) grazing on upland moor. As a result many moors became

overgrazed with a subsequent decline in the quality and quantity of dwarf heath shrubs

such as heather (Calluna vulgaris (L.) Hull) and other associated flora and fauna

(Anderson & Yalden 1981; Bardgett et al. 1995).

In recent decades, greater awareness of the impact of agricultural on semi-natural

habitats has led to the introduction of schemes such as the Environmentally Sensitive

Areas (ESA) Scheme, Countryside Stewardship and the Moorland Schemes, have resulted

in lower stocking rates being implemented on substantial areas of upland moor. Despite

these reductions localised over-grazing of C. vulgaris still occurs and less palatable

vegetation such as Molinia caerulea (L.) Moench and Nardus stricta L. remain under-

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grazed (ADAS 1998). When grazing pressure is reduced, species such as N. stricta are

avoided by sheep (Armstrong & Milne 1995), which can give these species a competitive

advantage over dwarf shrubs such as C. vulgaris. In addition, the local distribution of

vegetation communities has implications for the grazing pressure exerted by sheep in that

area, with large areas of grass within heather mosaics attracting sheep resulting in

concentrated grazing on C. vulgaris at the interface (Clarke, Welch & Gordon 1995), and

under certain conditions using the grass as a path, to gain access, to graze higher C.

vulgaris vegetation which would otherwise be inaccessible (Oom & Hester 1999).

The management of these communities is important if agri-environment scheme

objectives, aimed at maintaining and enhancing the cover of C. vulgaris, and UK

Biodiversity targets are to be met. Sheep grazing patterns can be modified during the

summer months by the introduction of self-help feed blocks (Waterhouse & Marsh 1999;

Davies & Griffiths 2000). However, it is known that sheep tend to graze C. vulgaris

during autumn and winter (Welch 1984; Grant et al., 1987) when more palatable grasses

do not meet their metabolic requirements. This study was undertaken to investigate

seasonal variation in the spatial pattern and levels (i.e. frequency) of grazing across two

enclosed moorland management units in mid-Wales and to determine whether these

patterns can be altered using self-help feed blocks strategically placed in

Vaccinium.myrtillus L./N. stricta dominated vegetation.

The specific aims of this study were: (1) to characterise the distribution of key

species on two enclosed moorlands in mid-Wales, UK; (2) to determine the spatial and

temporal changes in sheep grazing patterns on these key species at the scale of the

moorland management unit; and (3) to determine if the use of strategically placed

supplementary feed affects localised and moorland management unit scale grazing

patterns.

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Methods

SITES

The distribution of key plant species (C. vulgaris, N. stricta, V. myrtillus and M. caerulea)

and the frequency of grazing on them (pressure) was investigated at two sites in mid-

Wales, UK. (Table 1). The locations were selected on the basis that they were inside the

boundaries of the designated Cambrian Mountain ESA and currently held a part- or whole-

farm agreement which limited stocking rates to below 1.5 sheep per hectare per year on

semi-natural rough grazings with heather (as defined by Central Office of Information

1995). The sites consisted of an enclosed area of moorland dominated by mosaics of C.

vulgaris, N. stricta and V. myrtillus, which was grazed by Welsh Mountain ewes during

the experimental periods, with the sheep being removed from the area in early January.

The two sites differ in their size, shape and altitudinal range (Table 1). Site 1 was

larger and of a more irregular shape than Site 2. There was a height difference of around

190 m across Site 1 and the highest ground was located in the northern-central area. There

was a relatively steep drop further to the north-west where the lowest ground was located.

The rest of the site had relatively high ground, although it sloped gently downwards to the

south. The height difference across Site 2 was about 100 m, with the higher ground

forming a downward sloping ridge from north to south. The height decreased from this

ridge both to the south-east and the south-west.

EXPERIMENTAL TREATMENTS AND SAMPLING DESIGN

The experimental treatments focused on the positioning of standard self-help feed blocks

(Rumenco, Stettan, Burton-on-Trent, UK) used for supplementary feeding at both sites.

On Site 2, these feed blocks were placed in the centre of three randomly selected 50 m x

50 m experimental areas of V. myrtillus/N. stricta dominated vegetation. The treatments

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were applied at two different times of the year (May and November) for a period of six

weeks.

Sampling of local effects, with in each 50 m x 50 m experimental area, was

undertaken using twelve randomly placed 4 m2 quadrats. The distance of each quadrat

from the centre of each experimental area was measured and its position permanently

marked with wooden stakes. A single feed block was placed at the centres of three of the

six areas determined on Site 2. The remaining three areas, and all three areas on Site 1

were without feed blocks.

Sampling of whole-moor effects was undertaken to enable characterisation of the

spatial variation in vegetation composition and grazing pressure over a range of spatial

scales, across the whole moorland unit. A systematic random sampling approach was used

specifically to quantify spatial variation in each of the variables of interest. The basis of

the sampling plan was a 50 m grid covering the whole moor at each site. Additional

samples were located around selected baseline points to provide information on small-

scale spatial variation (<50 m) from all areas of the moors. The exact location of the

smaller-scale sampling points was determined by a systematic random selection of points

within the baseline grid. At each sampling point, within the whole-moor sampling set, a 4

m2 quadrat was used to minimise the effect of very small-scale (less than 30 cm) spatial

variation in each of the key variables. The position of the quadrats were permanently

marked with wooden stakes individually identified by numbered tags.

Sampling points were set out using tapes. All point locations and the moor

boundaries were geo-referenced using a Leica differential GPS system. The GIS system

ArcView (ESRI 1992) was used to link the GPS data with these field measurements, to

calculate the distances between sampling points and feeding blocks and to visualise the

spatial distribution of the measured variables across each moor.

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VEGETATION AND GRAZING ASSESSMENTS

Grids of 4 m2, divided into four hundred 10 x 10 cm cells were used for the assessments

undertaken at each sampling point (whole-moor and localized assessments). Vegetation

and grazing assessments were conducted in 100 of these 10 x 10 cm cells – 25 in each of

the four corners of the quadrat. Sheep dung occurrence and bare ground assessments were

conducted in all 400 cells of each quadrat. At each site, vegetation, grazing and dung

measurements were taken from each sampling point in the whole-moor assessments, at

four time periods in 1999 (Table 1). Collection 1, undertaken in May 1999, provided data

on the baseline distribution of species and grazing pressure at each site. Collections 2 and

4 were taken immediately after the spring and autumn feed block treatments, and

Collection 3 was taken immediately prior to the autumn feed block treatment. The effect

of the feed block treatment on the vegetation, grazing and dung variables was then

determined by comparison of the data from Collections 2, 3 and 4.

Baseline data (Collection 1) were collected from all the sampling points identified in

the local sampling strategy. However, for later collections three randomly selected

quadrats in each experimental area were monitored. For Collections 3 and 4, the same

sampling points were revisited so that any differences could be attributed to the feed block

time period.

For the vegetation assessments the presence of four key species (C. vulgaris, N.

stricta, V. myrtillus & M. caerulea) was recorded and the absence of other plant species

was noted in each of the one hundred 10 x 10 cm cells of the 4 m2 quadrat placed at each

sampling point. In addition, the occurrence of grazing in the cell and the occurrence of

grazing of the individual key species was also recorded. In each of the four hundred 10 x

10 cm cells of the 4 m2 quadrat the presence of sheep dung and bare ground was noted. In

the first sampling period May/June 1999, grazing assessments for each key species were

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made on last year’s growth. For subsequent sampling periods, all grazing assessments

were conducted on the current season’s growth. Thus data on level of grazing is

cumulative for Collections 2-4 whilst those from collection 1 represent the level of grazing

for the previous year.

When they graze, sheep tend to nibble mouth sized chunks and do not select

individual shoots. Therefore, for all of the species there is a grazing horizon, above which

shoots are grazed. This horizon is not necessarily parallel to the ground surface. Shoots

below this horizon will be ungrazed. Grazing of the key grass species was determined by

the presence of ragged leaf blades (indicating grazing) and the presence of a grazing

horizon. Grazing of C. vulgaris was determined by a missing terminal zone above last

year’s leaf scar. If this was due to grazing then other shoots at the top of the grazing

horizon would also be missing. Assessments of V. myrtillus grazing were made by

observations of the occurrence of the woody core that can be seen as a result of the uneven

bite surface.

DATA ANALYSIS

Summary data on the frequency of occurrence, abundance and level of grazing on each

key species were calculated together with a assessment of the temporal change in grazing

pressure on each species following each sample collection. Mean values for species

abundance and grazing level were based on the number of quadrats in which the species

occurred rather than the total number of quadrats present on the moor. Thus quadrats in

which the species were absent were not included in the calculation. The total grazing

intensity was calculated as the total number of grazed cells (V. myrtillus + C. vulgaris + N.

stricta + M. caerulea + Other) during each collection.

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Results

VEGETATION COMPOSITION AND DISTRIBUTION AT EACH SITE

The frequency of occurrence and abundance of the four key species are shown in Figs. 1

and 2. V. myrtillus was the most widespread (Fig. 1) and abundant species on both sites.

C. vulgaris occurred in 35% (221) of quadrats at Site 1 and 25% (115) at Site 2 (Fig. 1)

and where present, was normally abundant (Fig. 2). N. stricta differed markedly in its

distribution across the two sites, being widespread at Site 1 but not at Site 2 (Fig. 1). On

both sites, however, it was only moderately abundant when present (Fig. 2). M. caerulea

was not widespread at either site but was more abundant where present at Site 2 (Fig. 2).

The spatial distribution of the key species on Site 1 and 2 are shown in Figs. 3 and 4,

respectively. At both sites V. myrtillus was present across the moor, although at Site 1 it

was much less abundant in the southern ‘leg’ (Fig. 3). C. vulgaris was generally restricted

to discreet areas at both moors; at Site 1 it occurred mainly in quadrats in the central and

southern area (Fig. 3), while at the Site 2 it was restricted to the central and northern

quadrats (Fig. 4). N. stricta was widespread at Site 1 where it was abundant in the east

(Fig. 3); in contrast, it occurred only in patches across Site 2 and was only abundant in few

quadrats (Fig. 4). M. caerulea occurred at Site 2 in the same area where C. vulgaris was

present (Fig. 4). However, on Site 1, M. caerulea was restricted to quadrats in the

northern-central part of the site, where it occurred in low abundance (Fig. 3). These areas

on both sites were noted as having a high water table throughout the assessment periods.

TEMPORAL VARIATIONS IN GRAZING PRESSURE

The grazing pressure on each species at the four collections is shown for both sites in Fig.

5. On both sites grazing patterns were similar. V. myrtillus and other species, mainly fine-

leaved grasses, were grazed most heavily on each sampling occasion while grazing on the

other three key species was generally low. A temporal change in pattern was observed in

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the grazing pressures on V. myrtillus, M. caerulea and other species. The amount of

grazing on V. myrtillus was lower in July and October (Collections 2 and 3) than in May

and January (Collections 1 and 4) (Fig. 5). This would be expected since the May

collection was representative of a total previous year’s grazing whereas the collections in

July, October and January measured only the grazing during the current season. The

opposite pattern was observed for M. caerulea and other fine-leaved grass species. M.

caerulea was absent from all quadrats (Site 1) and was only present in four quadrats (Site

2) during the January collection (unpublished data) whereas during Collection 1 which

represented grazing on last years growth larger occurrences were recorded. This can be

explained by the deciduous nature of the grass with most of leaf blades of M. caerulea

becoming detached in the period proceeding Collection 4, whereas in Collection 1 many

still remained attached and therefore the grazing on these could be recorded.

THE SPATIAL DISTRIBUTION OF GRAZING

The proportion of grazing on each species at each sampling point of the 50m grid was

expressed visually using pie charts. The size of each pie chart indicates the magnitude of

the total grazing activity at that point (Figs. 6 and 7). A temporal spatial pattern of grazing

pressures can be observed in these maps. The pattern of intensity was similar at both sites

during Collections 1 and 4, with the majority of the grazing concentrated in a few areas.

At both sites, the most heavily grazed areas during these periods are coincident with the

areas where the highest density of V. myrtillus is found (Figs. 3 and 4). At Collection 2,

the grazing is more evenly spread across the moors. At Collection 3, the grazing is again

concentrated in a few areas, but these do not coincide with the greatest densities of any of

the focus species. During this period the grazing on ‘other’ vegetation at both sites, and on

N. stricta at Site 1 is particularly pronounced.

LOCALISED EFFECTS OF FEEDING BLOCK PLACEMENT

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The locations of the feeding blocks at Site 2 were outside the main areas of C. vulgaris

abundance in areas dominated by V. myrtillus (Fig. 4). To assess the effects that the

presence of feeding blocks may have had on grazing intensity within shorter distances of

the feeding blocks at this site, the results from the localised assessments were combined

with the results from the whole moor. Dropping densities and total grazing pressure were

combined in 20-metre distance classes from the feeding block locations (Figs. 8a and 8b).

There was no difference in dropping density (Fig. 8a) with distance from the feeding block

at Collection 1 indicating that there was no preference for the experimental areas being

exhibited by the sheep in the baseline data. Dropping densities were higher in the areas up

to 20-40m from the feeding blocks at Collection 2. At Collection 3 there was considerable

variability in dropping densities at locations close to the feeding blocks, which decreased

with distances from the feeding block. At Collection 4 the situation was similar to

Collection 1, albeit with an increased overall variability. The mean number of celss with

droppings recorded was fairly constant throughout Collections 1 to 2, for example Site 2

4.00and 3.29 cells, and but increased for Collections 3 and Collection 4, 8.32 and 17.63

cells, respectively.

Analysis of moorland management scale assessments showed that the pattern of total

grazing intensity was similar to the pattern for droppings (Fig. 8b), with increased total

intensity of grazing at locations within a short distance (20-40m) of the feeding blocks at

Collection 2.

Since the sampling points are located in the experimental areas which are dominated

by V. myrtillus, the analysis of localised effects of feed blocks will address the level of

grazing on this species as well as the level of total grazing and the presence of sheep

droppings.

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The changes in localised total grazing level and V. myrtillus grazing associated with

the periods of feed block placement are presented in Table 2. There is an increase in V.

myrtillus and total grazing levels on both sites during the spring feed block placement

period. However, during the autumn period the levels of grazing on Site 1 decreased,

whereas on Site 2 there was a general increase in total and V. Myrtillus grazing. This was

even greater for the experimental areas with feed blocks at their centre.

The frequency of sheep droppings (Table 3) was generally lower on Site 1 than Site

2 in both spring and autumn. In addition, Site 2 experimental areas which had feed blocks

located at their centres had a greater occurrence of droppings than experimental areas with

no feed blocks. However, within the boundaries of the experimental areas there was no

significant relationship between sheep droppings and the distance away from the feed

blocks for both experimental areas with or with out feed blocks at their centre in either

spring or autumn.

TEMPORAL CHANGE IN THE GRAZING STATUS OF EACH SPECIES

Temporal changes in the distribution of grazing across each moor were determined by

quantifying the number of quadrats of each species that maintained or changed their

grazing status, for example changing from grazed to ungrazed status, between each

collection. The results are shown in Table 4.

During the period May to July (Collection 2), which coincided with the first feeding

block treatment on the experimental site, a large percentage of quadrats of V. myrtillus, M.

caerulea and of other species changed their grazing status (Table 4), from ungrazed to

grazed. Little change in grazing level was observed on C. vulgaris quadrats on Site 1 and

2.

During August to October (Collections 2 and 3) the percentage of C. vulgaris

quadrats grazed, increased markedly on Site 1 but not on Site 2. This was accompanied by

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a spatial shift in grazing pressure (Fig.6) towards an area of the moor which was

dominated by C. Vulgaris (Fig. 3). The mean number of cells grazed per occupied quadrat

(Fig.5) did not increase dramatically. However, between Collections 3 and 4 the numbers

of ungrazed quadrats changing to grazed C. vulgaris quadrats were similiar to at both sites.

Therefore, the shift to C. vulgaris grazing was later at Site 2.

The percentage of M. caerulea quadrats grazed increased at Collection 2 on Site 1

but this was not apparent on Site 2 until October-January (Collections 3 and 4). On Site 1

this incease was accompanied by a spatial shift in grazing pressure in areas where M.

caerulea was abundant. However, on Site 2 grazing was still frequent (Fig. 7) in M.

caerulea abundant areas with V. myrtillus and N. stricta being preferentially selected.

The percentage of V. myrtillus quadrats grazed on Site 1 and 2. followed a similar

trend of increase throughout the year. A slight increase in the percentage of N. stricta

quadrats grazed also occurred on Site 1. These observed changes reflect to some extent

differences in the vegetation composition of the two sites, V. myrtillus being more

abundant on Site 2 than on site 1, but may also reflect an on-going effect of the feed block

treatment particularly with respect to the difference in C. vulgaris quadrats grazed at each

site.

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Discussion

SPATIAL AND TEMPORAL CHANGES IN THE DISTRIBUTION OF GRAZING ON

KEY MOORLAND SPECIES

There was a marked seasonal variation in grazing pressure on the key species of C.

vulgaris, V. myrtillus, Nardus, M. caerulea and on other species present at each site. The

results confirm those of Grant et al. (1987) that the dietary composition of sheep is greatly

influenced by time of year with M. caerulea being grazed in spring and summer, and

avoided late summer and autumn (Job & Taylor 1978), C. vulgaris and other ericoids in

autumn and winter and N. stricta in late autumn when other food is scarce (Welch 1984;

Grant et al., 1985).

Few studies have examined the utilisation of V. myrtillus by sheep, the most noted

one by Welch (1998), indicated that bilberry swards were grazed much more heavily

during August – October. However, the level and extent of V. myrtillus grazing observed

in this study throughout the year, almost to the exclusion of everything else is surprising,

and the sheer magnitude means that many studies have may under estimated the level of V.

myrtillus grazing within upland moorlands. The occurrence of other species, mainly fine-

leaved grasses, appears to be important in reducing grazing pressure on Vaccinium and C.

vulgaris during July-October when these species are most productive (Grant et al. 1987).

THE EFFECTS OF FEED BLOCKS ON GRAZING PATTERNS AT THE LOCAL AND

MOORLAND MANAGEMENT UNIT SCALE

The principal aim of the feed block treatments was to manipulate sheep grazing patterns

and to concentrate grazing in areas of moorland and move animals away from plant

communities such as C. vulgaris which they prefer to graze (Clarke et al. 1995a).

Mapping of the grazed vegetation in relation to distance and results from local grazing

assessments indicated that blocks were effective in manipulating sheep grazing behaviour

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and suggest that they may be used to enhance short-term grazing on selected vegetation

communities (Davies & Griffiths, 2000). Results from the moor scale assessments

suggests that the effect of the block is dependent on the time of year. In spring/summer

the placement of feed blocks may lead to an overall reduction in grazing across the moor,

and a concentration of grazing around the feed blocks. Whereas in winter there appears to

be no apparent effect. However, the analysis of localised grazing shows that there is still

an increase associated with block placement in the autumn. Studies by Waterhouse (1999)

and Waterhouse & Marsh (1999) showed that sheep tended to graze up hill from feed

block positions, however, in this study there seemed to be no preferred aspect.

Some changes in grazing status were apparent on the experimental site which may be

due to the feeding block treatments. During the summer period 43.4% of C. vulgaris

quadrats on the site without feed blocks changed from ungrazed to grazed status, compared

to 10.5% of quadrats on the site with feed blocks. Sheep normally switch to grasses in

May or June when the new flush of growth appears although Grant et al. (1987) reported a

high proportion of C. vulgaris and V. myrtillus shoots in the diet of sheep grazing on

heather moor in April-May. It is possible that the presence of feed blocks may have

delayed the switch to C. vulgaris from other species such as grasses. An assessment of the

local effects of the feed block treatments demonstrated a general increase in grazing within

50 m of the block, particularly for graminoids and a significant increase in the grazing

frequency of N. stricta (Hetherington 2000). However, the proportion of N. stricta in the

experimental areas within this study was very limited, therefore it is impossible to draw a

similar conclusion. Nevertheless more other species, such as fine leaved grasses, were

being grazed later during the year on the site with feed blocks (26.5%) than the site where

no feed blocks were present.

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When the feeding blocks are ‘in use’ or ‘effective’, they appear to cause a

concentration of grazing and general activity (i.e. droppings) within a radius of about 30m

around the feed block. This effect may alleviate pressure on surrounding areas.

There is a possible indication of an ‘after-effect’ of the placement of feed blocks in

the immediate area surrounding them. If this is true then it means that the feeding block is

able to draw sheep away from other areas for a prolonged time, especially if these areas

are further away. However this effect does not last into winter, as noted above.

Utilisation of C. vulgaris by sheep in autumn and winter is well-known (Welch,

1984; Grant et al. 1985) and it appears that the presence of the feed block early in the year

may again have reduced the switch onto these species later in the year. However, during

the period of the late autumn feed block treatment patterns were again similar with over

50% of C. vulgaris and 30% of Nardus quadrats changed from ungrazed to grazed on both

sites.

IMPLICATIONS FOR THE MANAGEMENT OF MOORLANDS (SEMI-NATURAL

ROUGH GRAZINGS WITH HEATHER) UNDER REDUCED STOCKING RATES

Gardner & Lobo (submitted) have shown that small-scale changes in species competition

can have a significant impact on the rate and direction of vegetation change across a whole

moor. Thus where localised manipulation of grazing interacts with the competitive

dynamics between species, the effects may persist into the long-term larger-scale

community dynamic.

The local vegetation distribution has implications for the grazing pressure exerted by

sheep, with large areas of grass within heather mosaics attracting sheep and resulting in

concentrated C. vulgaris grazing at the interface (Clarke, Welch & Gordon 1995) and in

certain cases the grass being used as a path, to graze the higher C. vulgaris vegetation at

the sides which otherwise would be unobtainable (Oom & Hester 1999).

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The use of feed blocks to move grazing pressure away from areas of naturally

occurring heather/grass mosaic interfaces at times of year when sheep grazing preferences

would result in levels of grazing that could change the competitive balance between

species would be advantageous. The extent of this effect will be determined from the

whole moor spatial analysis which together with longer-term sampling of the vegetation,

will indicate the size and extent of the impact of strategic placement of feed blocks on

vegetation composition.

Acknowledgements

The Authors would like to acknowledge the Ministry of Agriculture for their financial

support under project BD1216. We would also like to thank the farmers who gave us

access to their land.

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grass/heather mosaics. Journal of Applied Ecology, 32, 166-176.

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grazing of heather moorland by red deer and sheep. II. The impact on heather.

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Davies, O.D. & Griffiths, J.B. (2000) The strategic use of feed blocks to manage sheep

grazing in the uplands. In BGS Occasional Symposium No 34, (Ed. JA Rook).

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USA.

Gardner, S.M. & Lobo, N.A. The influence of spatial pattern in the dynamics of Calluna

vulgaris and M. caerulea on upland moor. Journal of Applied Ecology (in

submission).

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Gimingham, C.H. (1988) Introduction: Ecological change in the uplands. Ecological

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(1987) Comparative studies of diet selection by sheep and cattle: blanket bog and

heather moor. Journal of Ecology, 75, 947-960.

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and red deer within natural heather/grass mosaics. Journal of Applied Ecology, 35,

772-784.

Hetherington, S.L. (2000). The use of self-help feed blocks as an aid to grazing and

vegetation management of semi-natural rough grazing. Aspects of Applied Biology, 58,

1-6.

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University Press, New York.

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grazings on Plynlimon Wales. Journal of Biogeography, 5, 173-191.

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a natural heather/grass mosaic. Botanical Journal of Scotland, 51, 23-38.

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heather moorland in Great Britain: A review of international importance, vegetation

change and some objectives for nature conservation. Biological Conservation, 71,:163-

178.

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British hill farming systems. Options Mediterrancenes, 38, 365-370.

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Waterhouse, A. & Marsh, S.P. (1999) Effect of supplementation method on grazing

behaviour of hill ewes. British Society of Animal Science, Annual Meeting Proceedings

131.

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descriptions and patterns of utilisation. Journal of Applied Ecology, 21, 179-195.

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Economy and the British Countryside. (Eds. P. Allanson & M. Whitby), pp. 62-82.

Earchscan Publications Ltd, London.

5

Table 1. Summary of site characteristics and sampling details for the assessment of

spatial grazing vegetation patterns and their manipulation by supplementary feeding, at

scales of the moorland management unit and within 50m of the feeding area.

Sites

Site 1 Site 2

Grid Reference SN 83 95 SN 69 55

Area (ha) 54.9 39.0

Altitude (m) 370-564 340-430

Number of sampling points for the

assessment of vegetation and grazing at

the moorland management unit scale

631 461

Number of experimental areas for the

assessment of localised vegetation and

grazing

3 6

Number of assessment areas with

strategic feed placement

0 3

Collection period 1 May/June May

Collection period 2 July/August June

Collection period 3 October/November October

Collection period 4 January/February January

5

Table 2. The mean changes (±SE) in grazing of V. Myrtillus (VmG) and overall grazing

levels (Total G) during spring and autumn feeding periods for Sites 1 and 2. Site 1 only

contained experimental area which did not contain supplementary feed in the form of feed

blocks where as Site 2 included experimental areas with and without feeding blocks at

there centre (n=9).

Site 1 Site 2

Without feeding blocks Without feeding blocks With feeding blocks

VmG Total G VmG Total G VmG Total G

Spring 5.11±3.40 21.11±6.04 37.42±11.34 45.56±12.45 56.80±11.77 68.89±9.14

Autum

n

-5.47±4.72 -30.37±6.17 26.95±11.92 16.22±12.40 45.49±6.55 22.78±10.73

5

Table 3. The frequency of sheep droppings (mean±SE) after spring and autumn feeding

periods for Sites 1 and 2. Experimental areas in site 1 did not contain feed blocks where

as Site 2 included experimental areas with and without feeding blocks at their centre (n=9).

Spring Autumn

Without feed blocks Site 1 5.78±4.94 0.00±0.00

Site 2 7.44±4.48 7.44±2.91

With feed blocks Site 2 9.33±3.09 13.89±3.36

5

Table 3. The percentage of quadrats of each species group that changed their grazing

status between different sampling collections. Assessments were carried out on current

seasons growth.

Collection

(C) Periods

Site % change

C. vulgaris

% change

V. myrtillus

% change

N. stricta

% change

M. caerulea

% change

Other

0 vs C2 Site 1 5.5 73.2 28.1 93.9 74.6

0 vs C2 Site 2 5.8 72.4 24.4 83.5 57.5

C2 vs C3 Site 1 43.4 21.7 37.8 76.1 18.7

C2 vs C3 Site 2 10.5 34.6 26.9 38.6 26.5

C3 vs C4 Site 1 50.8 19.3 31.6 100 22.6

C3 vs C4 Site 2 57.3 15.5 42.0 67.7 16.6

5

Fig. 1. Frequency of occurrence of each of the key moorland species C. vulgaris, V. myrtillus, N. stricta and M. caerulea present on two

moorlands management units in mid Wales UK at Collection 1.

Fig. 2 Mean abundance of each of the key moorland species C. vulgaris, V. myrtillus, N. stricta and M. caerulea present on two moorlands

management units in mid Wales UK at Collection 1.

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myrtillus N. stricta, and M. caerulea at Site 1, Mid Wales, UK.

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5

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myrtillus N. stricta and M. caerulea at Site 2, Mid Wales, UK. The # marks the location

of the feed blocks used to manipulate sheep grazing pattern.

Collection 2

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5

Fig. 5. The mean number of cells grazed in occupied quadrats for the key moorland C. vulgaris, V. myrtillus N. stricta and M. caerulea at a)

Site 1 and b) Site 2.

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myrtillus N. stricta and M. caerulea at Site 1. The size of each pie chart indicates the

magnitude of the total grazing activity at that point.

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5

Fig. 7. Spatial variation in grazing pressure on each of the key species C. vulgaris, V.

myrtillus N. Stricta and M. caerulea at Site 2. The size of each pie chart indicates the

magnitude of the total grazing activity at that point.

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Collection 4

Collection 3

0 100 200 300 metres

5

Fig. 8. The relationship of distance from the feed block with a) the abundance of sheep

droppings and b) total grazing pressure for all four collections at Site 2. Data are a

combination of assessments made local to the feed block and at the moorland management

unit scale.

A)

Collection 1

25443638403126262926N =

Distance from feeding block, metres

180-200160-180

140-160120-140

100-12080-100

60-8040-60

20-400-20

Num

ber

of d

ropp

ings

at C

1

50

40

30

20

10

0

-10

Collection 2

2544363840312626209N =


180-200160-180

140-160120-140

100-12080-100

60-8040-60

20-400-20

Num

ber

of d

ropp

ings

at C

2

50

40

30

20

10

0

-10

Collection 3

25443638403126261910N =


180-200

160-180

140-160

120-140

100-120

80-100

60-80

40-60

20-40

0-20

Num

ber

of d

ropp

ings

at C

3

50

40

30

20

10

0

-10

Collection 4

25443638403126262215N =


180-200160-180

140-160120-140

100-12080-100

60-8040-60

20-400-20

Num

ber

of d

ropp

ings

at C

4

50

40

30

20

10

0

-10

5

10

15

B)Collection 1

25443638403126262926N =


190.00

170.00

150.00

130.00

110.00

90.00

70.00

50.00

30.00

10.00

Tota

l gra

zing

at C

1

140

120

100

80

60

40

20

0

Collection 2

2544363840312626209N =

Distance from feeding block metres

190.00

170.00

150.00

130.00

110.00

90.00

70.00

50.00

30.00

10.00

Tota

l gra

zing

at C

2

140

120

100

80

60

40

20

0

Collection 3

25443638403126261910N =


190.00

170.00

150.00

130.00

110.00

90.00

70.00

50.00

30.00

10.00

Tota

l gra

zing

at C

3

140

120

100

80

60

40

20

0

Collection 4

25443638403126262215N =


190.00

170.00

150.00

130.00

110.00

90.00

70.00

50.00

30.00

10.00

Tota

l gra

zing

at C

4

140

120

100

80

60

40

20

0

5

10

Manipulation of sheep grazing patterns on upland...

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