Holnest

Also within

Dorset County

Condition (Natural England)

Description

Description The SSSI is a nationally important site because it supports a large population of great crested newts Triturus cristatus on the south western edge of their range. The SSSI consists of two areas, which include breeding ponds and terrestrial habitat that is used by the newts for resting, foraging and hibernation. General description The site is situated on Oxford Clay. The clay soils are slowly permeable and seasonally waterlogged. Natural and artificial ponds are a feature of the landscape. Holnest is located seven kilometres to the south of Sherborne. The particular combination and distribution of aquatic and terrestrial habitats provides ideal breeding, foraging and hibernation conditions for the great crested newt. Numbers of newts recorded on the site are exceptionally high for Dorset, over 200 individuals were recorded in spring 2003 at one pond. The newts depend on water for breeding and particularly favour moderately, deep well vegetated, ponds without fish. The number and variety of ponds on the site, which are largely rain fed and hence of highwater quality, provide extremely good conditions for newts. great crested newts lay their eggs on underwater vegetation. The ponds support marginal plants such as branched bur reed Sparganium erectum, water plantain Alisma plantago-aquatica, greater reed mace Typha latifolia and reed sweet grass Glyceria maxima with broad leaved pondweed Potamogeton natans the most frequent floating vegetation. During the first two or three years of life before breeding starts and outside the spring breeding season, great crested newts are dependent on terrestrial habitats to provide foraging areas and places to hibernate. These terrestrial habitats comprise predominantly woodlands and grasslands. The woodlands comprise a canopy of ash Fraxinus excelsior and pedunculate oak Quercus robur with some downy birch Betula pubescens and with an understorey of hazel Corylus avellana, blackthorn Prunus spinosa and grey willow Salix cinerea. The ground flora is dominated by bluebell Hyacinthoides non-scripta and includes moschatel Adoxa moschatellina, sanicle Sanicula europaea and wood speedwell Veronica montana. Much of the grassland is of a varied structure and provides good foraging conditions for great crested newts. Most has been improved in the past but it is not now farmed intensively. Some of the original herbs, such as pepper saxifrage Silaum silaus, saw wort Serratula tinctoria and corky fruited water dropwort Oenanthe pimpinelloides, persist around field margins that are dominated by tufted hair grass Deschampsia cespitosa and Yorkshire fog Holcus lanatus. Grassland of nature conservation interest has been re established at Ryewater and other herbs and grasses present here include sweet vernal grass Anthoxanthum odoratum, crested dog’s tail Cynosurus cristatus, betony Betonica officinalis, grass vetchling Lathyrus nissolia and dyer’s greenweed Genista tinctoria. In addition to the reasons for notification the site also supports the freshwater mud snail Omphiscola glabra, a scarce species vulnerable to habitat damage. Three nationally scarce moths have also been recorded, the mocha Cyclophora annularia, the marbled green Nyctobrya muralis and the tortrix moth Notocelia tetragonana.

Species mentioned