BIOLOGICAI, AND ECONOMIC ASPECTS OE CHAPARRAL 11 



the tree, and this seed can pass through tires which totally destroy the 

 parent tree, without deterioration, the seed being scattered when the 

 cones open. Knob-cone pine is a strong tree because of its relatively 

 rapid growth on dry sites, and the fact that the cones retain seed of 

 good vitality for many years to be released after a fire. 



In the past the fire rotation in the chaparral forests was something 

 like 20 years longer on some areas than others, but since the Forest 

 Service has developed its present efficient protective schemes, the rate 

 of fire rotation has been increased to something like 200 years. This 

 change is manifesting itself in the reproduction, for now young trees 

 are showing up through brushy areas where their presence was never 

 before suspected and where there are no evidences of a previous forest. 

 With man aiding the forest by lengthening this rotation, the rapid 

 encroachment of the forest upon the chaparral may be expected. 



The successful planting of conifers in localities far from any tree 

 growth also demonstrates the fact that this is really forest land. In 

 one plantation Monterey and knobcone pines and deodar cedar are 

 growing so rapidly and thriftily that they are shading out the brush 

 and have built up a forest floor, having attained an average height of 

 16 feet and an average diameter of five inches in 15 years. 



Chaparral has a marked efifect on the reproduction of the trees. In 

 heavy mature stands of oak, lilac, and kindred species, a heavy leaf 

 litter from three to eight inches deep is formed. When this deep, it 

 nearly always is matted firmly together, and one can lift large chunks 

 of this material several inches thick without difficulty. Seed falling 

 upon this and not finding conditions favorable for germination either 

 lie dormant or rot. How long seed can lie in this dufif without losing 

 its vitality is not known, but with favorable conditions some seed 

 will germinate on the surface, though some will be unable to reach 

 mineral soil. It has been found that western yellow pine and bigcone 

 spruce cannot send their radicals through two inches of this duff, 

 Jeffrey pine through three inches, and Coulter pine through three and 

 one-half inches. 



In addition to offering a physical resistance to the germination of the 

 seed, the chaparral harbors countless numbers of seed-eating rodents 

 and birds who destroy immense quantities of seed, so that the chance 

 of a few seed trees being able to seed down a large brush area is ex- 

 ceedingly slight. If, however, a seed year comes soon after a fire in 

 which the seed trees have not all been destroyed, there is an excellent 

 chance of tree growth getting a start to some extent before the rodents 

 again become active. 



