Singlers Marsh Plan

SINGLERS MARSH LOCAL NATURE RESERVE WELWYN HERTFORDSHIRE Management Plan 2014 -2024 (JUNE 2014) SINGLERS MARSH, WELWYN, HERTFORDSHIRE Management Plan Section 1 DESCRIPTION 1 1.1 Name of Site 1 1.2 Location 1 1.3 Tenure 1 1.4 Legal Constraints 1 1.5 Physical Description 2 1.6 Ecological Description 2 1.7 Site History 5 1.8 Present Use 6 Section 2 EVALUATION 6 2.1 Wildlife Value 7 2.2. Amenity Value 7 2.3. Educational Value 7 2.4 Site Potential 7 2.5 The Role of Countryside Stewardship 8 Section 3 FUTURE MANAGEMENT 8 3.1 Objectives of Future Management 8 3.2 Management Proposals 8 3.3 Getting the work done 10 3.4 Community Involvement 10 Section 4 ANNUAL WORK PROGRAMME 11 Section 5 SITE MONITORING & REVIEW 12 5.1 Annual Monitoring 12 5.2 Plan Review 12 Section 6 Maps Section 1 DESCRIPTION 1.1 Name of Site Singlers Marsh Local Nature Reserve 1.2 Location Singlers Marsh is located to the immediate north of the village of Welwyn. A little more than three quarters of the site lies within the area administered by Welwyn Hatfield Council in central Hertfordshire, the remainder being within North Hertfordshire District Council’s area. The site’s eastern boundary is formed by the River Mimram and by enclosed private gardens along the B656 road between Welwyn and Codicote. On the west side are public roads with more residential properties. To the east of the site beyond the Codicote Road is Danesbury Local Nature Reserve, also owned by Welwyn Hatfield Borough Council. To the west, beyond adjacent housing, is open farmland, mostly arable but including grazing meadows and carr woodland adjacent to the River Mimram. A location map is included in Appendix 1. The centre of the site lies at Ordnance Survey grid reference TL 228166. 1.3 Tenure and Access The site is owned by Welwyn Hatfield Borough Council. Singlers Marsh was part of the estate of Welwyn Rural Council transferred to Welwyn Hatfield Council on its formation in 1974. There are no public rights of way but the public have unrestricted access on foot throughout the site. Access to the site is by kissing gates at several points along the western boundary. Although post-and-rail fencing now divides the site, a kissing gate allows free access to each part. The kissing gates were designed to allow access by push-chair and small childrens’ bicycles, but to prevent access by larger (motor) bicyles and horses. There is also field-gate access to each half of the site. Affinity Water has access via gates and concrete roads to two pumping stations located on the site. 1.4 Legal Constraints Singlers Marsh was declared as a Local Nature Reserve by means of a joint agreement between the borough council and Natural England in May 2009. ‘Local Nature Reserve’ (or LNR) is a statutory designation made under Section 21 of the National Parks and Access to the Countryside Act 1949, and amended by Schedule 11 of the Natural Environment and Rural Communities Act 2006. Singlers Marsh / Fulling Mill Meadow was designated Local Wildlife Site in 1997 at the time of the Hertfordshire Habitat Survey completed in 1999. This status gives a measure of protection from development, as does its location within a flood plain. Conservation management on the nature reserve has been supported since 1994 by Countryside Stewardship grant schemes in agreement with Natural England. Each grant scheme operates for a ten-year period, so the council’s agreement was renewed in October 1 2003 and again in October 2013 when the council entered the Higher Level Stewardship scheme. Most fences and access points are maintained by the Borough Council, except for those surrounding the pumping stations which are the responsibility of Affinity Water. 1.5 Physical Description Singlers Marsh is a long, narrow site extending to almost 700m in length but measuring no more than about 140m across the widest point. The land narrows at each end. In all, the site extends to 4.7 hectares and lies at a general elevation of 70m above sea level. The underlying geology is derived from the chalk overlain by various neutral to slightly acidic clays and gravels. The land slopes gradually from the western side of the site towards the river. The site is aligned north-west to south-east with the River Mimram forming the major boundary along the eastern side. The southern two-thirds of the area is bisected longitudinally by a seasonal stream fed by a spring arising in the northern part of the site. In times of heavy rainfall, the north end of the reserve is often flooded as a result of high ground water levels rather than directly from the river overflow. Flooding may also be due to impoundment of water caused by the artificial raising of land levels in the southern half of the site. The southern half of Singlers Marsh is separated from the northern half by post-and-rail fencing erected prior to the commencement of grazing in 1995. It is maintained for public amenity being regularly mown to keep the grassland short. The northern half is grazed by cattle in late summer/autumn. This provides the reserve with a more characteristic and ‘natural’ pasture habitat. The northernmost part of the site comprises a small area separated from the remainder by land occupied by a pumping station. It is a relatively quiet backwater of the river supplied with water diverted through the former Fulling Mill. Boundaries are fenced or hedged. The whole site is well endowed with natural cover provided by clumps of mixed scrub and the numerous large willow trees are a conspicuous feature. Singlers Marsh may be divided into compartments which are readily identified on site and shown on the map at Appendix 2: Compartment 1: the smallest compartment lying north of Fulling Mill Pumping Station and comprising a short section of river joined to the millstream connected by a small peninsular. Compartment 2: an old grazing pasture south of the pumping station as far as an old hedge boundary, separating it from the next field. Compartment 3: this comprises the land south of the old hedgerow and north of the post- and-rail fencing separating the site. It contains the majority of the willows. Compartment 4: the whole of the area south of the post-and-rail fencing, mown for amenity use. 1.6 Ecological Description Several main wildlife habitats may be recognised on the site. They are described below and shown on the map at Appendix 3, originally provided by the Hertfordshire Biological Records Centre. The habitats are as follows: 2 stands of willow trees mixed scrub, hedgerows and other trees species-rich neutral grassland species-poor rank grassland mown secondary grassland wet grassland and marsh temporary standing water permanent flowing water 1.6.1 Willow trees Crack Willows Salix fragilis were probably planted as an early attempt to dry out the areas prone to flooding. They can be found throughout the reserve, but mostly along the central stream course. A substantial line of crack willows is situated in the northern half of the Marsh. All are now of similar age and some have begun to break apart. This is natural growth behaviour of Crack Willows in flood-plain habitats. Fallen trees root into the ground, throw out new vertical stems and develop into new trees. In totally natural riverine woodland sites which are rare in Britain, this pattern of growth will alter watercourses and perpetuate a floodplain habitat. During the last 10-12 years however, several small groups of willows have been pollarded as part of a programme supported by the Countryside Stewardship grant scheme. Three mature crack willows were pollarded as part of health and safety works in 2012 and two more very mature crack willows growing adjacent to the river were reduced in height in Spring 2013 as part of the suite of works funded by Natural England via the Lea Catchment Nature Improvement Area and management undertaken by the Herts & Middlesex Wildlife Trust. Sallow Salix cinerea and Osier Salix viminalis grow with the crack willows along the seasonal water course flowing through the centre of the reserve. More unusual Salix species can also be found here including Shining Willow Salix lucida. Many of the bushes are now mature and have begun to fall out into adjacent grassland. A project to reclaim the grassland margins and regenerate the willows as younger coppice was begun in 2012 (see 3.2.3 below). Significant areas have now been cut and cleared, especially along the course of the seasonal stream. Ground vegetation beneath the willows is dominated almost entirely by nettles. Several of the older trees support good colonies of lichens and mosses. 1.6.2 Mixed scrub, hedgerows and other trees The scrub communities on the site are an important habitat for a wide range of wildlife, especially birds and insects. There are blackthorn thickets, clumps of bramble, and mixed aged scrub comprising hawthorn, field maple, elder and hazel. A few dead and dying elms remain in the roadside hedgerows and next to the river. Some of the clumps of scrub derive from old hedgerows formerly dividing the site into small fields. A new hedge was planted by Friends of the River Mimram around the fenced boundary of the central pumping station in 2011, using a hedgerow mixture supplied freely by the Woodland Trust. Some of the species included, for example, silver birch, are not characteristic of lowland wet meadow and may fail in due course.

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