128 



FLORA AND SYLVA. 



the centre to the outer edge. Where the under- 

 wood system is in force it will be seen that the 

 danger from wind is less when tall trees shelter 

 the young growths, since old trees protect the 

 saplings and young standards. On the outer 

 edge it is well to keep sheltering clumps of 

 trees to break the wind along exposed parts of 

 all great woods. These should receive special 

 treatment apart from the wood proper. In the 

 same way for Pines on mountain slopes, the 

 work should always go on in a direction opposed 

 tothatof the prevailing wind. It might be well 

 also if, as in certain provinces of central Ger- 

 many, neighbouring owners agreed upon zones 

 of shelter and defence, wherever great tracts 

 of woodland are similarly exposed. In any case 

 it is wise to maintain on the outskirts of the 

 wood some screen for separating the forest 

 proper from pasture land. This screen will vary 

 in breadth according to the altitude of the 

 woodland, the character of its ground surface, 

 and the force of the wind. 



Late and early frosts do much harm by 

 destroying the young shoots in the spring, and 



severe winter frost, by in- 

 Frost. juring the inner bark-layers, 



causes canker, at first super- 

 ficial, but eating deeper and deeper into the 

 trunk, and giving rise to all sorts of defects. 

 The only means of protecting trees from this 

 danger lies in such a knowledge of each species 

 as enables the planter to choose for it the situa- 

 tion which is freest from risk. Loss through 

 sudden fall in temperature has less to do with 

 the actual degree of cold than with the con- 

 ditions which accompany or follow it. Sudden 

 changes from cold to heat are far more danger- 

 ous — other things being equal — than slow 

 changes ; a frosty night followed by a bright 

 day may cause frost-bite at points exposed to 

 the sun's rays, when in other parts the trees 

 escape. In sandy, friable soils such as are easily 

 pierced by intense cold, frost-bite and kindred 

 ills are of more frequent occurrence than upon 

 clay, chalk, and (especially) peat soils. Smooth- 

 barked trees also are more liable to injury than 

 others. By choosing for evergreen trees a cold 

 aspect we ensure a more gradual transition 

 from cold to heat; also in hollows exposed to 

 late spring frosts it is well to plant the trees 

 least apt to suffer from cold, or such as are 

 late-leafing. 



Snow 

 and Landslips. 



The dread effect of lightning on trees is 

 shown in many ways, from partial stripping 

 of bark or the single furrow 

 Lightning. which bears witness to its 

 passage, to the stroke which 

 shatters the trunk of great Oaks. Often other 

 trees near are killed by the same stroke though 

 to all appearance untouched. Why one tree 

 should suffer rather than another has been a 

 matter of discussion, some thinking it due to 

 the pointed form of the tree, others to its den- 

 sity of leaf, and others again to the near presence 

 of water. More recent knowledge tends to 

 show that it lies rather in the conductivity or 

 certain kinds, and their green or dry state. It 

 would seem more natural that an Oak, with its 

 taproot striking down to water-bearing strata, 

 should be more exposed to lightning than the 

 Beech, with its shallow root-system. 



Woods are often injured or overwhelmed 

 by early or late snow falling upon trees in leaf. 



Even in England enormous 

 damage happened all over 

 the country to Oak woods 

 by fierce snow storms some years ago. Pine 

 forests upon the lower mountain slopes often 

 suffer from this cause. Its effects may be 

 minimised by clearings carefully made at the 

 right time and place. Landslips may be pre- 

 vented by trenching, staking, or buttressing 

 the ground with stone or masonry, and behind 

 these artificial defences — liable to decay as they 

 are — should be planted a more lasting one in 

 the shape of Swiss Pines. Landslips very often 

 occur in stiff or clay soil when trees are re- 

 moved,anditisimportantnottocut down trees 

 on such slopes, or it should be done at different 

 times. Wholesale clearings may lead to serious 

 trouble. By roadsides the removal of trees 

 may do serious damage. In a forest or planta- 

 tion liable to slip great care is needed to prevent 

 such accidents. 



There was an impression at one time that 

 forests kept off hailstorms, but numerous ex- 

 amples might be given of 



Hail, Rime, and trees bearing within their 

 Slcct, 



stems the wounds caused by 

 heavy h ailstones even after twenty-five or thirty 

 years, and covered by that number of succes- 

 sive woody layers. Rime and sleet causeserious 

 injury by depressing the shoots of saplings and 

 snapping the branches of old trees. 



