IX, A, 6 Brown and Mathews: Dipterocarp Forests 533 



In very moist localities the effect of removing the main canopy 

 might be much less severe than it would be in the dipterocarp 

 forest on Mount Maquiling. 



EFFECT OF CUTTING IN DIPTEROCARP FORESTS 



As has been indicated in the discussion of growth, cutting in 

 a dipterocarp forest carries with it a disturbance in the main 

 canopy which is usually accompanied by increased growth and 

 development of the second- and third-story trees, for the most 

 part of inconsiderable commercial value. This holds true, of 

 course, only for unregulated cutting in which the distributiom 

 of dipterocarps in the second and third stories is not adequately 

 considered. All cuttings under the supervision of a forest of- 

 ficer or staff are supposed to be done with some attempt at 

 regulation. Where the forest staff is small and has an extremely 

 large area to cover this regulation generally takes the form of 

 a simple diameter limit. The purpose of the diameter limit is 

 so to regulate the amount of cutting that the desirable species 

 remain on the ground in sufficient volume to insure their per- 

 petuation as the dominant species. This system of regulation 

 is essentially a regulation by volume, and in temperate climates, 

 where forests are composed of one or, at the most, of a very few 

 species, it has proved very successful. In the tropics the same 

 measure of success has not, for the most part, been attained. 

 Naturally, some forests are much better suited to the successful 

 operation of such a system than others, but dipterocarp forests 

 are, in a great majority of instances, not among those in which 

 this system succeeds. 



The use of the selection system, operated by means of a di- 

 ameter limit, presupposes that there is in the forest such a dis- 

 tribution of size classes that there can be fixed a diameter limit 

 which will remove that portion of the stand which is ready for 

 cutting and leave on the ground only that portion which should 

 remain. Our dipterocarp forests do not meet this necessary 

 condition. An inspection of the volume table for the northern 

 Negros forest on page 427 shows at once that no diameter limit of 

 any reasonable size will restrict the cutting to only that portion 

 of the main stand which can safely be taken out at one cut. A 

 diameter limit of 50 centimeters is regarded, in most parts of the 

 world, as exceptionally high ; but as can be seen from the above- 

 mentioned table the operation of such a limit in northern Negros 

 would allow almost clear cutting of the main forest canopy. 

 In the discussion of associations on cleared lands this has been 

 shown to be true. After cutting with a diameter limit of 50 



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