40 JOURNAL OF THE ARNOLD ARBORETTM [vol. i 



frequently by Red Pine cand Fir {Abies holophylla Maxim.) and in the 

 course of time develops into pure broad-leaf forest, mixed forest or pure 

 Pine-forest according to the type which becomes dominant. On tlie east 

 side of the Diamond Mts. where man has much thinned the former pure 

 forest of Red Pine, broad-leaf trees arc rapidly changing the w^holecharac-ter 

 of the forest. On the west side of the same mountains, especially rounrl 

 the monastery of Choanji, the broad-leaf forests are being displaced by 

 Nut Pine and Fir. In central Korea and northward coarse grasses are 

 less aggressive and Birch is associated with Aspen in increasing quantity 

 until the volcanic areas of the Paiktu region are reached w^here Larch be- 

 comes a ])rominent companion of the Pirch and Asj>cn. It is in this Paiktu- 

 san region tliat the succession of forest types is most clearly shown. The 

 cycle is roughly as follows: In the course of time after volcanic activity in 

 tliat region had ceased, as after forest fires at the present time» seedlings of 

 Birch, Aspen and Larch sprang up from seeds transported from the north by 

 wind. Then, as now, the three kinds of trees grew well together for a few 

 years, the Birch and Asi)en the faster at Lhe commencement, but tJie Larch, 

 though it needs when young a certain amount of shade just such as the 

 twiggy branches of Birch and Asp.en afford, is a light-denumding tree and 

 after twenty or thirty years it outstrii)S its fellows in pace of growth, finally 

 kills them and pure forests of Larch remain. Such forests are thin, open and 

 park-like in aspect and the trees almost of the same age, for no Larch seed- 

 lings will vegetate in such forests except by the side of v/ell-tramped ])aths, 

 or on fallen, rotting trunks, l)ut where fire breaks through they thrive exceed- 

 ingly. As the Larch-trees increase in size, so the forest floor beneatli be- 

 comes more and more shady and invites the presence of more shade-loving 

 trees such as Fir and Si)ruce. When the Larch is from sixty to one hundred 

 years old seedlings of these Fir and S])ruce establish themselves, in the course 

 of time grow into trees and finally kill out the Larch to form pure forests of 

 themselves. Like the Larch the trees are of about the same age, for in such 

 forests seedlings do not vegetate under the dense shade of tlie parent trees 

 either because the shade is too great, because there is too much humic acid 

 in the soil from the constant accumulation of rotting vegetation, or, because 

 of l)oth. On the edges of these forests, in glades, or on fallen rotting trunks 

 only are yoimg seedlings of Spruce and Fir to be found. 



Larch with its deciduous leaves, and trunks clear of branches for a con- 

 siderable distance from the ground, is in much less danger from fire than Fir 

 and Spruce which are evergreen, keep their branches from near the ground 

 Tipwiird and, moreover, have a very resinous bark and resinous leaves. 

 However, sooner or later, either from electrical storms or through human 

 agency, fire sweeps through tlie forests and the cycle is rejicated. 



The Fir { Abies holophijUa Maxim.) and the Nut Pine {Pinus lioraieiisis 

 S. & Z.) nowhere in Korea, to-day, form pure forests. Both are associated 

 with broad-leaf trees and the conifers mentioned above. They love rich, cool 

 soils and in the extreme north of Korea there are limited areas of forest 

 fifty per cent pure Nut Pine. 



