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NOTES ON THE EFFECTS OF HEATH FIRES 

 ON VEGETATION. 



Hi F. PARSONS, M.D.j F.G.S., 

 Croydon, 



Apropos of Mr. Elgee's paper on the vegetation of ' Swiddens,' 

 i.e., burnt moors, in North-East Yorkshire, the following notes 

 on the effect of heath fires on vegetation in another part of the 

 country may have some interest. 



In the neighbourhood of Croydon, in Surrey and Kent, are 

 several hilly commons on the Tertiary pebble beds, mostly at 

 altitudes between 300 feet and 500 feet + O.D. The ground is 

 mostly dry, except in the low parts, owing to the absence of 

 any impervious beds to throw out springs. The top soil is 

 thin and peaty, more or less mixed with sand. The dominant 

 plants are gorse {Ule.x europceiis and nanus) ling [Callitna), 

 purple heath, bracken and grasses, especially Aira flexuosa, 

 Molinia, Agrostis canina and Festitca ovina. There are also 

 scattered trees and bushes, especially birch and hawthorn with 

 brambles. 



The commons are not intentionally fired, unless in mischief ; 

 but in dry summers they are often set on fire by picnickers, by 

 lighted matches thrown down by careless smokers, and even, 

 it is said, by the sun's rays through the bottoms of broken 

 glass bottles which act as burning glasses. Areas several acres 

 in extent are thus frequently converted into a blackened waste. 



The fire feeds chiefly on the dry vegetation and debris above 

 ground, and owing to the thinness of the soil, does not char the 

 ground to any great depth. A footpath across the common is 

 usually sufficient to limit its progress, though sometimes when 

 the vegetation is long and dry, the flames, especially if aided by 

 a wind, will scorch the foliage of trees across a road of 30 feet or 

 more in width. Trees are not usually killed, though their 

 foliage suffers. Of bushes such as gorse, the twigs are consumed, 

 but the larger branches remain blackened and charred, and the 

 roots are not killed. Tufts of Molinia ma}- also escape with a 

 top charring. 



This superficial action of the fire is diflerent from what I have 

 observed in fires on deep peat moors, e.g. , Goole Moor, where the 

 fire may consume the dry superficial laj'ers of the peat before 

 the vegetation on the surface. I have seen behind the advanc- 

 ing edge of the fire, indicated by the smoke rising from the 



Natur.ilist, 



