500 TRANSACTIONS OF SECTION K. 



allotted to each unit should include several types of herbage, since these vary 

 in nutritive value and at different times of the year. The following plants 

 form types of vegetation, pure or in mixture : Heather (Calluna) is one of the 

 more important plants, and furnishes grazing for Black-face and other hill- 

 breeds of sheep all through the year. Cotton-sedge (Eriopfwrum) ocCTirs on 

 peat, and is valuable during the flowering season in spring. Purple heath-grass 

 {Moli7iia) has some grazing value in early summer, and this is increased where 

 the plant association includes heather. Narrlus stricta is another widely distri- 

 buted type, but it is less useful. Grassland on stream alluvia and on slopes 

 flushed by spring- water is an essential item of the herbage of every flock-unit.* 

 The proportion of each type of vegetation varies with the district. Thus, 

 Calluna is relatively more abundant in the eastern districts than in the western, 

 where there is a preponderance of greener herbage and peat vegetation. Because 

 of the local variation of the herbage there is no fixed nimiber for a flock-unit, 

 nor can any definite area be allotted ; some of the better hill-grazings carry one 

 sheep to the acre, others are nearer four acres to a sheep. There is considerable 

 opportunity for improvement in the production of the hill-grazinge. Amongst 

 methods in actual operation the following may be indicated : — 



Drainage. — Surplus water is generally removed by open surface drains. In 

 the case of peat this dries the surface and encourages heather. It also localises 

 the peaty water which causes deterioration, e.g., of good grassland on slopes, 

 into Narclus. On fine-soiled alluvia, drainage encourages the finer grasses to 

 replace Junciis and Carcx spp., which are less useful. 



Irrigation, or artificial flushing. — In some districts {e.g., S.E. Scotland), 

 where Calluna is in excess and grassland deficient, the latter can be encouraged 

 by leading spring water, emerging on the valley slopes, by means of open ditches 

 so arranged that the water overflows on to heather, which is thereby rapidly 

 displaced by gra,ssland. This is the result of constant or periodic watering by 

 more or less hard water, accompanied by surface aeration and by top-dressing 

 with fine mineral matter. 



Periodic burning. — The types with dominance of CaUuna, Eriophorum, 

 Molinia, and Narclii.s are treated by periodic burning. Heather {Calluna) at 

 some age (15 to 25 years) begins to lose vigour; it assumes a grey colour due 

 to scarcity of fresh green shoots, hence low feeding value ; the flowering is also 

 reduced. When this is fired, generally in the spring months up to middle of 

 April, the old plants are destroyed and the ground is left bare. Calluna returns 

 mainly by seedlings, less frequently from renewal-shoots arising from dormant 

 or adventitious buds at the base of old stems. The time required for renewal 

 of a close covering varies from five years upwards, and depends partly on the 

 age of Calluna when burned, partly on the soil. The slowest return is after 

 Calluna burned old on ' hard ' soils with a scanty surface layer of humus. The 

 quickest return is after Calluna burned young on surface-drained peat or on 

 soils -with several inches of himius. During the period after burning the area 

 may be occupied by a transitional vegetation, e.g.. Erica cinerea on dry soils, 

 Erica tetralix on moist soils, Vaccinium Myrtillus, Nardus, Molinia, Juncus 

 squarrosus, &c. ; these may become more or less permanent and displace Calluna. 

 The maintenance of the maximum food-supply requires that the heathery herb- 

 age be burned in patches or blocks, the total area of which varies according to 

 the rotation. With pure heather the annual proportion for any given area 

 should be one-fifteenth for a fifteen-year burning rotation ; some moors are 

 burned over every ten or twelve years. Where the heather is mixed with cotton- 

 sedge, &c., as on peat, a seven-year rotation is preferable. If the herbage is 

 mainly Molinia or Nardus, better grazing is supplied by burning every two to 

 four years. The number of years applies only where abundant seedlings or 

 renewal-shoots come within two years after burning. These proportions to be 

 burned annually are seldom attained in pra,ctice, although the recommendations 

 of the Grouse Disease Committee ' have been beneficial. With increased burning 



* Cf. ' Types of Upland Grazings,' D. Macpherson and W. G. Smith, British 

 Association, Sect. ]\I., Manchester, 1915. 



' ' The Grouse in Health and Disease.' Beport of the Committee of Inquiry, 

 1911. Popular edition, London, 1912. 



