Heath

Lowland heath is an interesting habitat and many issues surround it. It is not a natural habitat, it is man-made and yet it it has international protection status and much time, energy and funding goes into trying to maintain that which remains and restore some of what has been lost. If it is not a natural habitat why do we do this?

I started with that question as it is broadly what I was asked by someone when I was leading a nature walk on Sandford Heath near Wareham a year or so ago. There is a simple answer and a much more complicated one but effectively lowland heath may be man-made but it is an ancient habitat created in bronze age and iron age times (that is around 4,000 years ago!) when the local inhabitants started clearing the woodland that once existed to improve grazing for their animals. The soil was so 'poor' the first plants to colonise the cleared land were various heathers followed by gorse. A unique method of human subsistence farming developed which utilised what natural resources there were but it was a very hard, labour intensive life-style.

Much of the lowland area on all sides of Poole harbour is heathland and would, thousands of years ago, been under water which is where the underlying sand or gravel soil deposits originated. The sandy or gravel soil is generally acidic and so some very specialist plants and animals have been able to colonise the heathland. Most notably, of course, the sandy soil in some areas is ideal for the breeding cycles of our reptile species and all six of Britain's native species occur on the Dorset heaths. The conditions also suit bird species such as Dartford warbler and nightjar that occur here and are very scarce elsewhere in Britain. With invertebrates the story is similar and there are many insects that occur on the heaths that cannot be found elsewhere.

Time has made heathland special and the pace of change in the last 100 years or so has seen vast swathes of heathland lost, much of it for ever. Forestry, agriculture, mineral extraction and housing demands mean only a quarter of the heath that once could be found here remains. It is the unique landscape and its rare wildlife that make it internationally important and why so much effort goes in to preserving (and recovering) what is left.

There are various types of heathland ranging from predominantly dry heath to valley mire where it is constantly wet. Valley mire are not the places for the casual walker to venture as they can be quite dangerous (from time to time people have to be pulled out by helicopter!). Dry heath which rarely floods is accessible but can be difficult walking in places whereas wet heath , which tends to dry out a bit in summer, can be accessible with care.

There is a single example of dune heath in Dorset at Studland. Limestone heath is also a rare habitat in Dorset


 

 

Habitat Types: 
Displaying 1 - 6 of 6

These are some of the habitat types that occur within this general classification. Click/tap any thumbnail for more detail about a specific habitat type.

H1: Dry Heath

Dry heath typically occurs on higher levels of fertile acid sands and gravels that drain freely with the falling rain water passing quickly through the soil to the peat layer below and down towards wet heath and...

H2: Dry Heath/Acid Grassland Mosaic

As you walk over higher dry heath you will occasionally come across areas of open grassland which have resulted from past agricultural activity. In some cases this may date date to Mesolithic times and the original...

H3: Wet Heath

Wet heath occurs in two situations. Firstly in shallow hollows in surrounding dry heath (these can be quite big hollows!) or, secondly, as a transitional phase between dry heath and valley mire and bog. Wet heath is not...

H4: Valley Mire and Bog

Although valley mire and bogs are technically wetland habitats I have included them with heath because they form in low lying valleys and depressions in heathland areas where water percolates through the sand and gravel...

H8: Dune Heath

Dune heath forms on sand dunes that are relatively stable and where heather can take hold often after marram grass has started to colonise. Studland is the only example of dune heath in the south of England. It has a much...

H9: Limestone Heath

Limestone heath is a rare habitat type and occurs where sand deposits have accumulated on a limestone substrate. Limestone heath usually forms at high level on hills and escarpment slopes the sand having come from further...

H1: Dry Heath

H1: Dry Heath

Habitat Class: 

Dry heath typically occurs on higher levels of fertile acid sands and gravels that drain freely with the falling rain water passing quickly through the soil to the peat layer below and down towards wet heath and eventually valley mire and bog. Being such difficult conditions for plants to grow dry heathland is dominated by specialist plants such as heather and gorse. Open dry heath is dependant on some form of intervention management in the form of grazing, burning or clearing to stop regeneration by scrub and eventually tree species such as birch and Scots pine.  

There are various types of dry heath but analysis of these is rather for the experts and I choose to pit them all into one heading but as you visit various areas of heath you start to notice that, contrary to popular belief, heathland habitat is, indeed, quite variable in subtle ways. For example, north of Poole the dominant heather is ling whereas south of Poole it is the deeper purple of bell heather than is dominant. Again, to the north of Poole there is quite a lot of western gorse whereas to the south European gorse  is more common. The dwarf gorse is more widespread to the north of Poole although is frequent to the south.

Within any dry heath areas there are going to be variations as well where, for example, worn paths expose the sand below. his is where some of reptiles thrive along with ground nesting bees, wasps and beetles. Gorse scrub can establish in some areas, a home for Dartford warblers, and elsewhere scattered birch and Scots pine may become established which are beneficial to woodlark, tree pipit and nightjar.

Lowland dry heath is an internationally endangered habitat but, thankfully, although much has been lost in the last fifty years or so, there is still a good amount left in Dorset.


 Under the Phase 1 habitat survey classification system dry dwarf shrub heath is coded as D1 and is described as follow:

"Vegetation with greater than 25% cover of encoids or small gorse species in relatively dry situations. Calluna vulgaris (ling). Vaccinium myrtillus (bilberry), Erica cineraria (bell heather), Ulex minor (dwarf gorse) and Ulex galli (western gorse) are typical of lowland dry dwarf shrub heath. Acid heaths usually occur on deep podsols developed on base-deficient sands, gravels and clays. Basic heaths are much more restricted in extent and may be recognised by the presence of herbs characteristic of chalk grassland and open habitats. "

Under the National Vegetation Classification system dry heath is classified primarily as H1-4, H6, H8-10 and H12-22.


 

The information about this Site of Special Scientific Interest has been organised into reports, charts, maps and photos. Click a pic below to see the detail:

Distribution Map Linked Species Linked Sites Some Photographs Guidance Notes
Habitat Home: 

When you have finished here click/tap the pic to return to this habitat's home page and continue to discover more about it's features and species

H2: Dry Heath/Acid Grassland Mosaic

H2: Dry Heath/Acid Grassland Mosaic

Habitat Class: 

As you walk over higher dry heath you will occasionally come across areas of open grassland which have resulted from past agricultural activity. In some cases this may date date to Mesolithic times and the original woodland clearance which was followed by intensive stock grazing or attempts at cultivation. Other areas may be more recent attempts at agriculture but the underlying sand or gravel soil has defeated even the most optimistic farmer!

In the ancient areas the border between the heath and the grassland may have become somewhat blurred and the flora and fauna will be quite rich and varied whereas in more recent areas there may still be clearly defined fields with less diverse vegetation. It is quite common for these areas to be still grazed by livestock today and in the Purbeck area on Stoborough Heath and Middlebere Heath ponies from the New Forest have been brought in to help maintain the nature of these ancient sites.

This is not a pure habitat type but a hybrid of two but they are so entwined that it is easier to merge them together. Areas of heather and gorse are interspersed with open grassland of where particular dry areas are colonised or the reddish brown sheep' sorrel which gives it a unique and distinctive look.

 


Under the Phase 1 habitat survey classification system dry heath land/acid grassland mosaic is coded as D5 and is described as follow:

"This represents a common mixture of dry heath (D1) and acid grassland (B1). The category has been specified only for the ease of mapping and the relative proportions of each type of habitat should be noted."

Under the National Vegetation Classification system dry heath/acid grassland mosaic  is classified primarily as H1-4, H8-10, H12, H15-18 and U1-8.


 

The information about this Site of Special Scientific Interest has been organised into reports, charts, maps and photos. Click a pic below to see the detail:

Distribution Map Linked Species Linked Sites Some Photographs Guidance Notes
Habitat Home: 

When you have finished here click/tap the pic to return to this habitat's home page and continue to discover more about it's features and species

H3: Wet Heath

H3: Wet Heath

Habitat Class: 

Wet heath occurs in two situations. Firstly in shallow hollows in surrounding dry heath (these can be quite big hollows!) or, secondly, as a transitional phase between dry heath and valley mire and bog. Wet heath is not generally permanently wet tending to dry out in periods of relative drought.

Formed on acid soils with a thin layer of peat it favours hardy but shallow rooted vegetation with a predominance of sedges and rushes but also some specialist flora features. Cross-leaved heath is often a dominant species as opposed to ling and bell heather in dryer conditions. The intermediary nature of the environment means that species dependant on surface water to be present such as oblong-leaved sundew is not found whereas round-leaved sundew that can survive happily in damp conditions as well as near standing water thrives on bare mud patches.

Insect fauna, being mobile, can move between neighbouring habitat types as water levels vary to suit their requirements. Quite often, pools that never dry out form which are acidic in nature and favour several species on dragonfly and damselfly. The mosaic combination of dry heath, wet heath and valley mire and bog are essential for some quite rare insect species such as the Southern damselfly and the large marsh grasshopper.

In general, wet heath is generally far more accessible than valley bog and mire although after very prolonged wet periods they may become impassible.


 Under the Phase 1 habitat survey classification system wet heath is coded as D2 and is described as follow:

"A s with dry dwarf shrub heath (D1) this vegetation type has more than 25% cover of encoides and/or small Ulex (gorse) species. However, it differs from D1 in that Molina caerulea (purple moor grass) is often abundant and it generally contains some Sphagnum compactum  0r Sphagnum tenellum and less frequently other sphagna.

In transition to mires the proportion of Sphagna will increase and the species composition will change often with Sphangum papillosum and Sphagnum subnitens becoming more frequent. Erica tetralix(cross-leaved heath)  is common in wet dwarf shrub heath and is often present in significant quantity. Trichophorum cespitosum (deer-grass) is occasionally present at lower levels. Macrolichens such as Cladonia portentosa , Cladonia arbuscula and Cladonia uncialis may be locally abundant. The abundance of Molina and Erica tetralix decreases in the transition from wet to dry heath."

Under the National Vegetation Classification system wet heath is classified primarily as M15/M16 and H5.


 

The information about this Site of Special Scientific Interest has been organised into reports, charts, maps and photos. Click a pic below to see the detail:

Distribution Map Linked Species Linked Sites Some Photographs Guidance Notes
Habitat Home: 

When you have finished here click/tap the pic to return to this habitat's home page and continue to discover more about it's features and species

H4: Valley Mire and Bog

H4: Valley Mire and Bog

Habitat Class: 

Although valley mire and bogs are technically wetland habitats I have included them with heath because they form in low lying valleys and depressions in heathland areas where water percolates through the sand and gravel of the neighbouring higher ground into the low lying area from where it cannot readily escape, possibly because of the topography of the ground (bog) but also, frequently, where the vegetation slows down the run off into a stream or river (mire). This seepage through vegetation into a river can be seen quite clearly at Morden Bog or Hartland Moor in Purbeck. 

The water in these areas is usually acidic and poor in nutrients and so favours a unique variety of plant species but, notably, sphagnum mosses are a key feature of such sites. Valley mire is wet at all times of the year although the water table level will vary depending on the amount of rain and so the fringes may not always under water. Plant species near the edge of a valley mire may well differ from those who will have their foundations in water all year. Certain specialised insects also thrive in these conditions and, being able to move, can relocate to appropriate degrees of 'wetness' to suit their needs.

Valley mire can show a variation in surface patterns with open ponds, or even lakes, where the surface is clear to what is known as blanket bog where the water surface is covered in dense vegetation and the water is hidden. These can be particularly dangerous places for some animals, including humans! Both plants and animals will vary depending on the degree of open or covered water. Looking down on a valley mire it is possible to see changes in colouration of the vegetation as the mix changes with the depth of the water.  

Of 120 known valley mire sites in northern Europe 90 are found in the New Forest. I do not know exactly how many of the remaining 30 are in Dorset but it is certainly in double figures and the Dorset heath around Poole Harbour is an important area for this unique and rare habitat. Most mires have existed for thousands of years almost unchanged although there is evidence of peat digging is some areas where the depth of the peat is significant. In some cases valley mire has formed in places where clay has been extracted at some point in the past. 

Valley mire is a unique and interesting habitat. The variations between very wet and occasionally wet areas and between open and covered wet areas leads to diversity of species, many of which are quite unique to such conditions.


Under the Phase 1 habitat survey classification system valley mire is coded as E3.1 and is described as follow:

"A valley mire develops along the lower slopes and floor of a small valley and receives water from springs and seepages on the valley sides, feeding a central water course. Such a fen can be distinguished from a flush because the former is a complex, whereas a flush is a discrete single feature, usually of limited extent.Valley mires are often dominated by acidophilous vegetation containing sphagnum species, carex species and ericoids. However, vegetation typical of base rich conditions can also occur, for instance, Schoenus nigricans (bllack bog-rush) and Juncus subnodulosus (blunt-flowered rush). Floating mats of mosses and sedges may be present. Acid watercourses often contain Hypericum elodes (marsh St John's-wort) and Potamogeton polygonifolius (bog pondweed)."

Under the National Vegetation Classification system valley mire is classified primarily as M21 and M29


 

The information about this Site of Special Scientific Interest has been organised into reports, charts, maps and photos. Click a pic below to see the detail:

Distribution Map Linked Species Linked Sites Some Photographs Guidance Notes
Habitat Home: 

When you have finished here click/tap the pic to return to this habitat's home page and continue to discover more about it's features and species

H8: Dune Heath

H8: Dune Heath

Habitat Class: 

Dune heath forms on sand dunes that are relatively stable and where heather can take hold often after marram grass has started to colonise. Studland is the only example of dune heath in the south of England. It has a much restricted flora because of the harsh soil conditions but reptiles and some insect species thrive in these conditions.

Dune heath is classified along with dry heath and has similar species depending on how well an area has become established and stabilised.


 

The information about this Site of Special Scientific Interest has been organised into reports, charts, maps and photos. Click a pic below to see the detail:

Distribution Map Linked Species Linked Sites Some Photographs Guidance Notes
Habitat Home: 

When you have finished here click/tap the pic to return to this habitat's home page and continue to discover more about it's features and species

H9: Limestone Heath

H9: Limestone Heath

Habitat Class: 

Limestone heath is a rare habitat type and occurs where sand deposits have accumulated on a limestone substrate. Limestone heath usually forms at high level on hills and escarpment slopes the sand having come from further north blown by the wind. The mix of acidic sands and underlying calcareous rocks can produce a strange cocktail of heather and gorse mixed with chalk grassland flora like common milkwort, dropwort and salad burnet. 

Limestone heath is not separately classified and often gives the appearance of acid grassland so the appearance of chalk loving plants in amongst the heath species produces a strange effect!


 

The information about this Site of Special Scientific Interest has been organised into reports, charts, maps and photos. Click a pic below to see the detail:

Distribution Map Linked Species Linked Sites Some Photographs Guidance Notes
Habitat Home: 

When you have finished here click/tap the pic to return to this habitat's home page and continue to discover more about it's features and species