IV] GRASSLAND ASSOCIATIONS 105 



in the same plant formation. On the Pennines further north 

 (see Smith and Rankin, 1903: 154), similar sub-Alpine pasture 

 occurs; but there one species, Poa alpina, occurs which has 

 not been found in the Peak District. Sub-Alpine pasture, 

 characteristic of the Scottish mountains, has been described 

 by R. Smith (1900 b : 454). 



On the calcareous soils, the grassland is poor in heath-loving 

 or humus-loving species but rich in lime-loving species, and this 

 association is termed calcareous grassland. A certain number 

 of species (see the lists of plants given later on in the chapter) 

 are common to siliceous grassland and calcareous grassland. 

 The two types of grassland are related, directly or indirectly, to 

 the presence or absence of calcium carbonate in the soil. On 

 the limestones, it is only at the higher altitudes, where the soils 

 are leached by rain and therefore contain much less lime, that 

 calcareous grassland approaches siliceous grassland in its eco- 

 logical and floristic characteristics. On the lower slopes of the 

 calcareous hills where the soil is rich in lime, the acidic 

 humus which favours the growth of the plants of the siliceous 

 grassland does not appear to be formed ; and it certainly does 

 not accumulate. 



A certain amount of grazing of sheep and cattle takes 

 place on many parts of the grassland ; but the amount is, on 

 the whole, rather small. The land is not artificially manured 

 or drained. On the sub-Alpine grassland, no grazing or 

 manuring takes place at all. 



Other types of grassland occur in other parts of the country, 

 more especially in central and southern England. Clayey and 

 fresh loamy soils, for example, are characterized by the absence 

 of both humus-loving and of lime-loving species ; and the 

 grassland of such soils may therefore be termed neutral grass- 

 land. A fourth type occurs on the flat lands which occur near 

 rivers and which are liable to periodical inundations : this may 

 be termed alluvial or fen grassland. An analysis of the 

 grasslands of Orkney has recently been published (Scarth, 

 1911). 



" Permanent pasture " is an agricultural term in use in 

 this country to denote grazing land which has, in general, 

 been ploughed up at least once, and which is artificially 

 manured (see Chapter VIII). 



