Ding Quarry, Rochdale - Assessment of Vegetation Colonisation

Penny Anderson Associates
Consultant Ecologists
52, Lower Lane
Chinley
Stockport
SK12 6BD

1. Introduction

Objectives

1.1 The aim of the assessment was to examine the extent and character of the vegetation which has colonised the quarry since it was abandoned, and to estimate the age of any species which can be measured

1.2 The site was visited on the 22nd of November 1995, and a walk-over survey conducted in order to produce a vegetation map. The approximate location of all woody vegetation which can be aged was marked, and major variations in plant communities mapped.

2. The Quarry Character

2.1 Most of the quarry area is composed of what are assumed to be old tramways and their associated banks which were used to take the waste rock, vegetation and overburden away from the working face.

2.2 The vegetation of the tramways is variable. the sides are, in places, dominated by very large rocks, whilst elsewhere there is a complete and dense grass cover. Other areas are of a very patchy vegetation with grasses or mosses. The small scale variation in the vegetation is so great that only broad habitat categories are indicated on the accompanying map and the locations shown for specific species or types of habitats are approximate due to the difficulty of accurately locating each tramline.

2.3 The major grass species found on the site are mat-grass (Nardus sticta) and Common bent-grass (Agrostis capillaris). Both are significant components of the surrounding moor land vegetation and would colonise the disused quarry fairly quickly after quarrying activity ceased. However, from experience on the other moor lands, it is likely that it would take 5 to 10 years for a complete grass cover to become established on the abandoned quarry assuming that sheep were not excluded and bearing in mind that mat-grass, in particular, grows and spreads fairly slowly.

2.4 Crowberry (Empetrum nigum) is a major component on the sides of the tramways in the western section of the quarry. This plant does not occur in any quantity in the adjacent moor land to the south-east. Crowberry seed germinates after passing through the gut of a bird and it is likely that this plant must have been more frequent in the adjacent moor land than it is now to result in the degree of colonisation exhibited in the quarry. this alone suggests that it colonised some time ago.

2.5 The crowberry is variable in form, location and age, but it is generally in a prostrate creeping form between the larger rocks on the edges of the tramways. At the time of the site visit much of the crowberry looked to be in poor condition, being brittle, with little fresh growth and few leaves. This may be the result of the 1995 dry summer and the plants could be severely droughted and stressed.

2.6 The age of the plants has been established in two ways. Firstly, by counting the stem nodes (a classic way to age similar woody shrubs such as Heather (Calluna vulgaris) which identifies the points where each new year's growth begins) and secondly by counting the stem rings of a cross section under a 30X microscope. Generally the plants were in the 15-18 year range but some were older examples of 40 or more years were found.
The older plants were located towards the southern half of the tramways. Crowberry does not readily vegetate bare ground and it is likely that the plants would begin to appear 5-10 years after the abandonment of those area of the quarry where it is found, were these were on raw soils, but might have established at an early stage if it could re-grow in the dumped peaty soils removed with the overburden.

2.7 Several small patches of deep peat vegetation were located within the area of the disused quarry. These included Hare's-tail cotton grass (Eriophorum vaginatum), Cross-leaved heath (Erica tetralix), Heath rush (Juncus squarrosus) and Purple moor-grass (Molinia caerula). It is unclear if these are areas of the original vegetation or are tipped peat which has re-established the vegetation typical of the undisturbed areas. The cross-leaved heath does not appear to be particularly old or well established, there are only short stems visible and the plants could not be accurately aged.

2.8 Along the remaining rock face of the quarry there is some vegetation cover with grasses on the ledges, occasional ferns (broad buckler-fern (Dryopteris dilatata) and Hard-fern (Blechnum spicant)) and various lichens, algae and mosses. There are also two small Rowan (Sorbus aucuparia) trees in the rock face. The larger of the two has been aged at 15 years as an absolute minimum and is much more likely to be over twenty years old, the stressed conditions resulting in the small size and generally stunted growth of the tree. The tree was aged by counting the number of annual growth increments.

2.9 There are however, some small bare and apparently freshly exposed areas on the rock face. These may be the result of a natural rock fall and weathering of the face or the direct removal of stone by mechanical means.

2.10 The area immediately adjacent to both the remaining rock faces has been very recently (within the current growing season) disturbed by a large tracked machine which has levelled areas. There is also an area to the west of the quarry which has been disturbed in the past year or two, with the topography shown on the map bearing no relationship with that on the ground. It is not clear exactly what operations have been undertaken in this area only that material has been moved around.

2.11 There are also signs that a tracked vehicle has moved widely around the quarry and dug holes in the existing waste piles and tramways on the quarry floor. this has allowed observations of the soil depth in these areas. the overall conclusion from this is that, like the vegetation, the soil depth is very variable from 15cm to less than 2.5cm. The soil depth is a product of the amount of rock, shale and soil dumped in each area by the trams, also the compaction or lack of compaction by vehicles, it is impossible to deduce age from the depth of soil as it has not been produced in situ.

2.12 the pond shown on the base map used does not hold water or any aquatic vegetation. the degree of colonisation of a pond could have aided the aging of the vegetation. there is some aquatic vegetation Flote-grass (Glyceria spp) and Water-starwort (Callitriche spp) on the old track way marked on the map. These species are however, very common, and although there are good stands, little can be concluded except that the vegetation has been there for 3-4 years.

2.13 The band of soil mounds closest to the northern rock face, south of the bare areas have a more disturbed vegetation than the bulk of the quarry. The vegetation is not so productive on these areas and crowberry occurs only rarely. these may indeed be the youngest waste piles or they could have undergone the most disturbance due to the closeness of the rock face and therefore the working area. If the recent disturbance witnessed had been undertaken in a similar fashion in the past then this would be the result of recreational pleasure - bikes, motorbikes or 4 wheel drive vehicles. There is evidence of limited usage of the quarry by all the vehicles mentioned, and more intense activity could have resulted in the thinner vegetation on those waste tips closest to the rock face.

Conclusion

2.14 The major area of quarry floor supports a dense cover of vegetation with individual plants of crowberry aged on average 15 years or more. This cover of vegetation, bearing in mind the minimum length of time crowberry is likely to take to establish itself, indicates a lack of major disturbance for at least 20-30 years.

2.15 The rock face to the north is generally vegetated to some degree and although there is little, apart from the two stunted rowan trees, which can be aged it is thought to be unlikely that there has been substantial working of this face in the last 25-30 years. This conclusion has been reached by the presence of the trees one of which is aged at 15-20 yrs and the need for some weathering of the rock face before it would provide the conditions for the establishment of trees.

2.16 there is more disturbed vegetation on the spoil mounds closest to the rock face and very little crowberry was recorded from this area. However, the cause of this disturbance is not clear and could be from sources other than quarrying activities.

2.17 Small areas have been recently levelled and recent exploratory holes have been dug into the existing spoil mounds.