Some Preliminary Observations on the Ecology of Pit Heaps

Abstract

This preliminary account of the ecology of pit heaps is based on work carried out in the Nottinghamshire-Derbyshire coalfield and to a lesser extent in the south Yorkshire coalfield. The investigation was carried out in the attempt to discover what factors lead to the establishment of vegetation on pit heaps and the types of plant involved. In addition detailed studies of particular plants were made with reference to their capacity to stabilize pit banks. METHODS Although Hope-Simpson (1940) has shown that subjective estimates of plant frequency vary considerably, this method was used in nearly all the work reported here because it seemed the best for rapidly estimating the frequencies of plants growing on a large number of heaps. The final list of plants presented here is derived from the pooled information of frequencies of plants from each of forty heaps. In five of the heaps studied the numbers of shoots found in twenty half-metre quadrats were counted, the quadrats being randomized on the heaps as follows. A stone was thrown and where it landed the compass points were roughly drawn out. Four random numbers were taken from Fisher and Yates's Statistical Tables (1953) and these were measured out in feet, one in each compass direction, and the quadrats put down. This was repeated until twenty quadrats had been made. A similar procedure was employed for randomizing the glass plates used for trapping wind-borne seeds. Each stem in a quadrat was counted as a single plant. In the case of tuft formers such as Festuca ovina each small bunch of grass was counted as one shoot. The age of the five heaps studied in detail was supplied by the surveyors of the National Coal Board, East Midlands Division. It was decided that the date of the last tipping on the particular part of the heap studied should indicate the age. The material making up the heaps was of similar geological origin and the greater part of it came from the Deep-hard, Deep-soft horizon. (I am indebted to the Chief Surveyor, National Coal Board, East Midlands Division, for this information.) Pit heaps usually consist of mixtures of: (a) Bind, an indurated clay mixed with oxide of iron; (b) Fireclay; (c) Sandstone; (d) Ironstone and (e) Small amounts of clay and boiler ash. This waste is tipped into heaps by means of overhead buckets or by waggons; often pit heaps have been on fire and this has restricted for a period the growth of vegetation; such heaps can often- be recognized by their red colouration. It was decided to classify the visible fragments of pit heaps according to size as shown below. Ten metre quadrats were taken at random on each heap to estimate the size of fragments, which were classified as: (a) fine, where most of the material ranged *Now at the Manchester Grammar School.