Formulative Influences on the Landscape
Vegetation and Biodiversity
The landscapes of Test Valley Borough are an important resource for biodiversity, supporting a wide range of habitats and species. The patterns of biodiversity across the Borough today have resulted from the interaction of the natural environment and the long history of human settlement and management of the landscape. This section summarises the broad patterns of habitats across the Borough.
The north of the Borough is dominated by the chalk geology, giving rise to the downland landscapes of the Open Chalklands. The downland landscapes extend to the east across the Hampshire Downs and to the west into the higher and more rugged South Wessex Downs. The Chalk Downland Ridge that runs through Quarley Hill downs marks a transition to the higher South Wessex Downs and is associated with several areas of unimproved grassland.
Since the late 1940s the great majority of the downland grasslands have been ploughed for arable farming and improved ley grassland. The remaining resource of species-rich grasslands are largely confined to isolated sites and to the steeper slopes where ploughing is less practical, and to military training areas. Nationally important areas of grassland are found at Danebury Hill, Quarley Hill Fort and Porton Downs. Remnants of the grassland flora also survive along some green lanes, verges and tracks and beside hedgerows. There are great opportunities to create new areas of unimproved grassland in the downs, and to link isolated remnants along tracks and field margins.
Many areas of the Downs are valued by the local community for open views so any creation of new woodlands or hedgerows will need careful planning. Woodland cover is sparse across much of the downs, and often limited to shelter belts. Woodlands are more common where deposits of clay with flints cap the chalk in the Semi Enclosed Chalk and Clay Farmland and the Semi Enclosed Clay Plateau Farmland. The clay deposits are more extensive in the Enclosed Chalk and Clay Woodlands and the Enclosed Clay Plateau Farmland Landscape Character Types, giving a greater proportion of woodland cover.
The woodlands found on the most acidic soils over clay with flints are dominated by oak, with ash dominant in more neutral and calcareous woodlands. Many woodlands were traditionally managed as coppice, although this form of management has declined in recent years.
The Downs are dissected by stream valleys, and by the broader floodplains of the River Test and its tributaries. Towards their upper reaches, many of the streams in Bourne Valleys flow only seasonally and are completely dry in the summer. Such winterbournes are characteristic of the downland landscapes, and are associated with neutral grasslands along the valley base. Much of the grassland has been agriculturally improved and there is great potential to restore species-rich grasslands.
Further downstream, the rivers and streams of the River Valley Floor are fed by water from the chalk aquifer at a constant temperature of 10óC. This constant temperature and flow has led to the development of a very diverse aquatic habitat. The River Test is a nationally important freshwater habitat with a rich assemblage of aquatic plants.
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The River Valley Floor landscapes are associated with many areas of former water meadow and much of the land adjoining the rivers remains as unimproved grassland today. Many areas of neutral floodplain grazing meadows occur such as those at Chilbolton Common and Stockbridge Common. Other areas have developed as alder and willow carr and as rush pasture following the decline of flood-meadow management. South of Romsey, much of the permanent pasture of the floodplain has been lost to arable and improved grassland although important areas of fen and grazing marsh survive in the far south.
The mosaic of habitats in the south of the Borough is influenced by the complex geology of sand, gravel and clay that mask the chalk, and also by the distinctive cultural history of the New Forest. Semi-natural broadleaved woodlands are prominent in the Mixed Farmland and Woodland – Small Scale and the Mixed Farmland and Woodland – Medium Scale Landscape Character Types. There are many ancient woodlands with a continuous history of woodland cover since at least 1600 AD. Woodlands are often associated with the heavier clay soils that are more difficult to cultivate and are dominated by oak. There has been a decline in coppice management of woodlands over the last century and there is great potential to increase the biodiversity of woodlands through improved management. Species-rich hedgerows, often associated with assarting, are an important resource linking the woodlands.
The unenclosed Heathland landscapes of the New Forest extend into the south-western part of the Borough, on Plaitford Common and West Wellow Common. The heath vegetation, dominated by heather, dwarf gorse and cross leaved heath, occurs in mosaics of acid grassland, woodland and scrub. Valleys have wetter areas due to the deposition of clayey soils and are often associated with mire habitats. Some remnants of heath vegetation are found in the adjacent enclosed landscapes of Pasture and Woodland Associated with Heathland and there is scope for restoring and extending these habitats. A good example of a heathland remnant is at Baddesley Common.
Although Test Valley Borough is a largely rural borough, there are significant urban areas at Andover, Romsey and on the fringes of Southampton. Important habitats lie in and beside these urban areas, including woodland, heath and unimproved grassland. The close interface between urban and rural landscapes is a significant feature of the Borough and there is great potential to improve the quality of these urban fringe habitats to provide benefits for biodiversity and the people living nearby. The gardens in villages and beside isolated houses across the Borough also provide significant habitats, and can be managed to support wildlife.
Test Valley Borough has many nationally significant habitats and there is great potential for increased biodiversity in the future. The Local Biodiversity Action Plan (LBAP) for the Test Valley will provide an assessment of the opportunities for improving biodiversity in the Borough. The LBAP should be used in conjunction with the Landscape Character Assessment to encourage the creation of habitats that provide benefits for biodiversity and contribute to the distinctiveness of landscapes across the Borough.