The Distribution and Abundance of Grassland Species in Hill Pasture in Relation to Soil Aeration and Base Status

Abstract

The data were collected from twenty-eight sample plots in an area of about 24 ha (60 acres) of sheep pasture in the Cheviot Hills on the Sourhope Field Research Station of the Hill Farming Research Organisation. The area sampled was restricted to an altitudinal range of 270-330 m (900-1100 ft) and included the bottom and lower slopes of a small upland basin of open aspect with surrounding summits at 370-490 m (1200-1600 ft). The plots varied widely in orientation and the slopes ranged from 0 to 6?. The soils all belong to the Sourhope Association and were derived from glacial and soliflucted drift material formed from the local andesite (Muir 1956; Ragg 1960). The climate of the area is characteristic of south-east Scotland, being relatively dry and sunny compared with other similar hill areas, most of which are farther to the west. The average rainfall recorded at 270 m (900 ft) about 15 km from the experimental area is 937 3 mm (36 9 in.). Data for potential water surpluses or deficits are sparse but it appears that at the 305 m (1000 ft) level one or more periods of water deficit (calculated for weekly periods) are to be expected in most summers, usually between April and July. Such dry spells can give rise to accumulated deficits as high as 60 mm. The mean duration of daily sunshine over the year is 3*3 h which is within the range to be expected for central Scotland while the mean daily air temperatures are similar to those for other hill areas in the south of Scotland. The history of the area is one of year-round sheep grazing at low stocking rates,