CAUSES OF DECLINE. 19 



the rainy districts and forms a dense mat several inches thick over 

 the surface of the ground. Tree seeds can not germinate beneath it. 

 Another coarse grass of similar habits is the so-called rice grass (mau- 

 like). But it is neither so common nor so prohibitive of reproduction 

 as Hilo grass. 



In drier districts Bermuda grass (manicnie) obtains such a hold as to 

 prevent forest reproduction, and even to hinder tree growth. Some of 

 the forests of Hamakua and Kohala, in Hawaii, have died from no 

 other apparent cause than a predominant growth of this grass. 



FIRE. 



Fire has done far more injury in Hawaiian forests than would be 

 supposed in regions of so great rainfall. The most serious fire within 

 recent years occurred two j^ears ago in southern Hamakua. It burned 

 an area 15 miles long and 2 to 4 miles wide, leaving unburned only 

 occasional patches. Trees, undergrowth, and humus were generally 

 completely destroyed. The forest was a normal one for the islands, 

 consisting of a fairly heavy growth of lehua and koa, with a heavy 

 undergrowth of fern and a deep accumulation of humus. Ordinarily 

 this forest could not have been burned, but a severe drought prevail- 

 ing for several months previously had dried it out to the point where 

 it burned with great rapidit3\ At the present time the land is covered 

 with fallen trees and debris, and in places a growth of weeds. But 

 little reproduction has. as yet taken place, and, as practically all seeds 

 and seed trees on the area were burned, there is no possibility of 

 immediate reproduction. Whatever growth comes up on the land 

 must come from seeds carried in from other places. 



Other forest districts, particularly on Kauai and Maui, have also 

 suffered from fire, though there have been no other recent burns so 

 severe as the one mentioned above. 



There is distinct evidence of a severe fire upward of fifty years ago 

 in the southern part of Hamakua. This fire burned over a tract of 

 large, though unknown, extent. It killed practically all the forest 

 and undergrowth, and consumed the humus. Its heat must have been 

 intense, for it baked the soil to such an extent that at the present time 

 it shows as a brick-like layer from 2 to 6 inches thick. In many cases 

 it burned the roots of trees several feet below the surface. The 

 forest which has come up on the ground following this fire, though 

 composed of the same species as the ordinary Hawaiian forest, differs 

 from it distinctly in conditions and requirements. The trees have 

 grown slowly and have less than the usual amount of undergrowth, 

 but they have far greater power than the normal forest to withstand 

 grazing. 



