86 CHARACTET^ AND COMPOSITION OF WOODS. 



period has arrived, the factors of the locaHty must suffer. 

 Exceptions are woods growing under favourable conditions. 

 temporar}' mixtures and shelter-woods. 



Generally, only the even aged form is admissible, and even 

 then such mixtures require constant attention, so as to 

 prevent one species being suppressed by the other. 



a. Mi.rlmc in Jliiih Fnresf. 



(1.) Oak, iritJi asli, rhii, or street chesftiiif. — These mixtures 

 require a fertile, deep, moist soil and a favourable climate. 

 Oak is slower growing during early youth, and in many cases 

 also later on ; hence it is liable to be suppressed. At any 

 rate it rarely finds sufficient space for favourable development, 

 being closely pressed by the otlior light demanding species. 

 It does better if placed in groups. 



(2.) Oal,- iritli alder and hircli. — This mixture occurs on 

 wet soil, where the oak occupies the drier parts of the 

 locality. If mixed by single trees, the oak is speedily 

 suppressed. 



(3.) Oal- nith Scotch pine or larch. — Such mixtures are 

 made because oak helps to protect the Scotch pine against 

 damage by insects, snow, etc., and larch against cancer, 

 while Scotch pine and larch protect the oak during youth 

 against frost and drought, ]f for the latter purpose, the 

 mixture is frequently of a tenqiorary nature, or only a few 

 Scotch pines or larches are allowed to remain when the oak 

 does no longer require shelter. 



(4.) Scoteli pine nitli Jiirch. — This mixture occurs naturally, 

 and yet it cannot lie recommended, because such woods are 

 always very thin aiul the soil deteriorates. They are 

 generally the result of unfavourable conditions in localities, 

 where no other species can compete with Scotch pine and birch. 



Up to 15 or 20 years birch grows quicker; the Scotch pine, 

 if it survives tliat period, conies up and passes it; the birch 

 then i-equires hell), if it is to be preserved. Birch falls under 

 the axe at a ccnnparatively early age, and an open wood of 



