512 PROTECTION AGAINST FROST. 



and especially those of shallow-rooted species, such as spruce, 

 birch, alder, beech, hornbeam, etc. Even ash, sycamore, and 

 silver-fir are not unfrequently uprooted in this way. Sweet 

 chestnut, hazel and oaks escape this form of injury on account 

 of the depth to which their tap-root descends during germina- 

 tion. The greatest damage is done in nurseries to seed-beds 

 and beds of transplants, and to sown areas in forests. 



(b) Locality. Certain soils and localities suffer more than 

 others in this way. Thus, provided they are moist fine 

 soils, such as peat, fine sand, marls and loam, are most 

 exposed to frost-lifting. Dry sandy soils do not suffer. As a 

 rule, the finer-grained a soil is, the more water it absorbs, 

 and plants are therefore more easily lifted in such soils, 

 whilst in coarse-grained, sandy soil the water descends, and 

 the surface is therefore not subject to lifting. Soil bare of 

 herbage is also more easily lifted than soil which is kept down 

 by the roots of grass and weeds. 



As regards locality, deep depressions suffer most, as there 

 is then less chance of the moisture draining away. Warm 

 aspects, except westerly ones, suffer most, as, on them, thaw- 

 ing and freezing follow one another most frequently ; northerly 

 aspects hardly suffer at all from frost-lifting. 



3. Protective Rules. 



(a) For the Forest. Drain away all superfluous moisture 

 by open drains ; drain-pipes may be used only in nurseries. 

 Planting should be preferred to sowing, and ball-planting is 

 the best security against this evil, while spring-plantings 

 suffer less than autumn-plantings. Where sowings are 

 adopted, oats may be mixed with the seed, which should be 

 sown rather densely. Preserve the natural soil-covering of 

 weeds when plantations are made on soil liable to be lifted 

 by frost. 



(b) For Forest Nurseries. Mix clay soils with 25 to 83 per 

 cent, of sand. Raise the seed-beds so as to secure good drain- 

 age. Sow deeply and densely, and cover the spaces between 

 the drills or rows of plants with straw, dead leaves or saw- 

 dust, all of which are bad conductors of heat ; even cinder- 

 dirt mixed with sand may be used ; this delays thaws. After 



