River Cliff Woodlands in Worcestershire

By John Day

This note is based on part of work undertaken for Worcestershire County Council which comprised a desk study aimed at pin-pointing suitable habitat, followed by a field survey to search for Sorbus domestica, the True Service Tree (See Worcestershire Record - references at end of article) in Worcestershire. No new Sorbus domestica have been found to date!

The field survey also proved invaluable for the collection of data on the riverine cliff ancient woodland communities of Worcester shire. These ecotones are of outstanding ecological interest. Furthermore, they are fragile, often very small, and ecologically important, and the aim of this article is to place on record a few of their notable features, to give examples, and to list the most important sites. These woods are within the highest possible category of Worcestershire woodlands in their scores for naturalness, diversity, rarity, fragility, recorded history, intrinsic appeal and scientific value.

Wood-edge communities, that is light demanding saum types, combined with ancient provenance and habitat continuity are the primary ecological features which determine their special quality. A novel suite of soils and physical conditions adds to their interest. Ecological gradients are steep. There is considerable natural variation. For instance, bluffs, cliffs, cliff tops and cliff bases vary floristically within a small area. Micro-patterning of plant communities may be intense. The physical character of each site gives a unique fingerprint to each site. These woods are so rare that all remaining examples are worthy of conservation.

The survey did not examine any sites on the Devonian, Carboniferous or Silurian geological formations. That is the areas upstream of Stourport on the River Severn and upstream of Osebury Rock on the River Teme and these are not discussed in detail. However, the Wyre gorge does hold some fine examples. Similarly, a whole series of small and very rich wood-cliff communities occur along the Teme between Knightsford and Little Hereford near Tenbury Wells.

Special reference is made to the limestone woodlands of the Knightsford gap (on ancient river cliffs) and the magnificent Devonian cliff below Berrow Hill.

Marl Cliffs

The outstanding feature of the marl cliffs, those derived from the Mercian Mudstones, is the abundance of Wild Service Tree Sorbus torminalis . It is often confined to a narrow band along the leading edge of the cliff. In such locations individual trunks may be of considerable age, and its favoured niche is at the crumbling cliff top, where it often grows vertically downwards, so that a canopy of ancient Wild Service may curtain the cliff top. These are ancient clones occupying native wildwood habitat, possibly since the dawn of human immigration after the last Ice Age. It is quite feasible that these individuals have occupied the Sabrine cliffs for thousands of years as a single creeping root-mass, moving inland as the cliff crumbled and fell. This woodland community scores as high as possible for naturalness.

Of special interest is the occurrence of wood edge plants of both oligo-mesotrophic soils and of more basic conditions in close proximity. This due to the varying soil conditions, through the vertical exposures, and is a reminder of the variability of mudstone derived soils.

Riparian cliff-base willow woods are a feature of some sites

The rare phenomenon of tufa springs derived from the Mercian Mudstones is exhibited at Rockhill and Cotheridge on the River Teme.

Triassic Sandstones and Breccia Cliffs

The outstanding feature of these cliff is the lime wood communities. Both small- and large-leaved limes, Tilia cordata and Tilia platyphyllos occur. The former is often dominant. Nationally, all ancient semi-natural woodlands with Tilia platyphyllos are of ecological significance, as this is one of Britain's rarest native trees. Wild Service Tree is also a constant component, but is mainly confined to rock exposures, and therefore may occur at a low frequency. The classic ground flora component on the more skeletal soils is Luzula sylvatica. Nationally uncommon, Festuca altissima occurs on the cliffs in Shrawley Wood.

Important and fairly well-known examples of this group of woodlands are Shrawley Wood and the outliers at Blackstone Rock, and on the Breccias at Osebury Rock. However reference must be made to the series of woodlands on the bluffs above the flood plain between the confluences with the rivers Stour and Salwarpe on the left (east) bank of the Severn. These are an outstanding limewood resource in size, rarity (species and communities), diversity, scientific resource and intrinsic appeal. The stands are generally richer in species and often have a better structure than those in Shrawley Wood.

The almost constant occurrence of Tilia platyphyllos is a distinct feature of these woods. The population here is certainly of regional significance and provides a contrast to the populations on the more basic soils of the Silurian formations.

Sites of High Scientific Interest

These sites are known from this or previous surveys by the author to support exceptionally fine examples of riverine cliff, woodland communities. Within their geological formations, they are considered to be the best examples examined to date, within Worcestershire. Only sites with features of high scientific interest are listed below.

Mercian Mudstone / Marl Cliffs

Red Cliff & Hayley Dingle: SO7554, SO7654, SO7553.
Rockhill Covert: SO7953, SO7952, SO7853.
Clevelode Cliff: SO8346
Cliffey Wood: SO8344, SO8444
CliffWood: SO8542
Bevere Cliff: SO8459
Cotheridge Cliff: SO7854

Triassic and Sandstone Cliffs

Blackstone Rock: SO7871, SO7971.
Redstone Rock: SO8169
Lincomb Wood: SO8168, SO8269
Winnall Coppice: SO8166, SO8167.
Shrawley Wood: SO8165, SO8166
Mutton Hall & Lineholt Woods: SO8166, SO8165, SO8164.
Hawford & Bournes Dingle: SO8460, SO8461, SO8362

Breccia Cliff

Osebury Rock: SO7455

Acknowledgements

Grateful thanks to the Worcestershire County Council for permission to publish note arising from commissioned work.

References