;26 



AMERICAN FORESTRY 



and a greneral feeling of depression and 

 discouragement prevailed. An idea, 

 like the reforestation of the country by 

 which large areas of land could be re- 

 claimed, compensating in some measure 

 for the lost provinces, would naturally 

 appeal to the energetic and active ele- 

 ments of the population. Xo man was 

 probably better fitted for this work than 

 Dalgas. He soon succeederl in rousing 

 interest in the cause, formed in 1866 

 the Danish Heath Society ( Det Danske 

 Hedeselskab). and found many warm 

 supporters of his work, prominent 

 among whom was the Danish consul- 

 general in Hamborg, Pontoppidan, who 

 enabled Dalgas to commence the work. 

 .Also, the government was induced to 

 give a subsidy, which at first was small, 

 but which in the following years was in- 

 creased and was supplemented by in- 

 creasing private subscriptions. 



The first technical difficulty to be 

 solved was that of finding a tree which 

 would grow under the adverse condi- 

 tions existing on the sand dunes and on 

 the heath, and it was found that the 

 mountain fir from Central Europe 

 ( Pinus uioiitoiia) served the purpose 

 better than any other tree. This tree 

 would, in fact, thrive in spite of winds 

 aufl drought, wet or cold, and would 

 kill the heather by spreading close over 

 the ground. Spruce, if planted alone, 

 would generally reach a certain devel- 

 opment, but then stagnation might set 

 in and continue for many years ; only 

 in some spots would the trees grow up. 

 where they appeared as hillocks or isl- 

 ands above the average growth of 

 stunted and undeveloped trees. 



The cause of this irregularity in the 

 growth of spruce was .sought in local 

 conditions of the soil, but in many such 

 cases the most scientific research has 

 not revealed any difiference in the phvs- 

 ical or chemical composition of the soil, 

 and it is now generally considered that 

 the cause is biological. 



The next great step in the develop- 

 ment was the discovery of the remark- 

 able fact that the mountain fir acted as 

 a nurse to spruce trees planted in its 

 vicinity. Tn the same localities where 

 spruce, if planted alone, would remain 



stagnant at an early age. it would, if 

 planted close to a mountain fir, grow up 

 vigorously ; and on the basis of this 

 discovery a new system of planting was 

 introduced, by wdiich the mountain fir 

 and the spruce were mixed, one moun- 

 tain fir for each one, two, or more 

 spruce trees, according to the quality 

 of the soil. 



.\fter some years of experience it 

 was, however, found that the mountain 

 fir, which had been an excellent nurse 

 during the early years of the life of 

 the spruce, would hamper their growth 

 and cause them to stagnate when they 

 were at the age of about ten years ; 

 while the mountain fir would grow up 

 and overshadow the spruce. Now fol- 

 lowed the next important step in the 

 development, when it was discovered 

 that even if the mountain fir was cut 

 down at an early age, the vitality which 

 it had given to the adjacent si:)ruce trees 

 would remain in effect, and these would 

 continue to grow thereafter as well as 

 if they had been planted in good soil. 



This remarkable discovery was made 

 b\- Colonel Dalgas's son. Christian Dal- 

 gas, who is a forester in the service of 

 the Heath Society, and one of its lead- 

 ing men, and who has devoted his life 

 to the continuation of the great work 

 commenced by his father. 



The influence of the mountain fir on 

 the spruce was for a long time denied 

 by many men of science. The phenom- 

 enon is not clearly understood, but va- 

 rious theories have been propounded, 

 the most plausible of which seems to 

 be that the roots of the mountain fir 

 are inhabited by some microscopic par- 

 asite, which produces the nitrogen nec- 

 essary for the growth of the trees, and 

 that this organism is transferred to the 

 roots of the surrounding spruce trees. 

 Once this infection or transfer has 

 taken place, the presence of the moun- 

 tain fir is no longer necessary, and is, 

 in fact, rather pernicious after the trees 

 have reached a certain age. 



flence, by the latest method of plant- 

 ing, mountain fir and spruce alternate, 

 so that one mountain fir is planted for 

 each one or two spruce trees, and at an 

 early age the fir, when it has done its 



