540 ^^/le Philippine Journal of Science im 



ting and the clear cutting extends uninterruptedly over the whole 

 area of the operation. If the system of utilization is necessarily 

 so intensive that it becomes impossible to leave the necessary 

 amount of shelter wood in the area, it will be better to abandon 

 entirely any thought of limitation of the cut and to accept as in- 

 evitable the fact that clear cutting will have to be carried on and 

 then so to regulate this clear cutting that a fair measure of suc- 

 cess can be expected. Due to environmental considerations clear 

 cutting in the Philippines will probably rarely be a satisfactory 

 system of forest management. The intense insolation following 

 any considerable opening of the forest crown is always followed 

 by a tremendous reduction in the percentage of the main species 

 in the reproduction and by the entrance of vast quantities of 

 intolerant, rapid-growing weeds, trees, and vines. The larger 

 we make the opening in the forest, the greater is the change 

 in the climatic condition and the more surely does the forest 

 pass over into a second-growth or jungle habit. If then clear 

 cutting becomes necessary, it must be confined to the smallest 

 possible area permissible under the system of logging in use. 

 The smaller the opening in the forest, the more does the effect 

 of the adjoining forest extend over it and, likewise, the less 

 is the opportunity for light-loving weeds and vines of the ad- 

 joining open land to enter the area. If the system of utilization 

 is not so intensive as to preclude the possibilities of leaving on 

 the area a shelter wood which will at the same time protect 

 the young growth already on the ground and furnish seeds for 

 additional reproduction, some system of limiting the cutting 

 is advisable. The defect of one arbitrary diameter limit for 

 the whole area has already been discussed. If the amount of 

 supervision that can be given the operation is so limited that 

 it becomes obvious that nothing but a diameter limit can be 

 used for purposes of regulation, the limit should vary for each of 

 the main species in the area. No diameter limit whatever should 

 be set until after a thorough study of the volume and species 

 distribution of the forest has been concluded and until there 

 have been collected data showing the approximate size at which 

 most of the main species come into full seed bearing. With data 

 of this kind at hand it would be possible to set a diameter limit 

 for each of the species in the stand which would be satisfactory 

 for certain limited types of forest. It would not be possible 

 to set such limits for each species, over the entire area, as the 

 habit of growth of the trees, their time of seeding, and distribu- 

 tion by volume will differ at different elevations and under dif- 

 ferent conditions of soil moisture and exposure. A study should, 



