THE ECOLOGY OF THE BUTTES 25 



trees. There are numerous other characteristics of woodland 

 birds. 



4. THE BUTTES PARTLY PIXE COVERED. 



The buttes of the forest reserve are all "flat" topped. The 

 west member of the Cave Hills is called Table Mountain, be- 

 cause it is so level. The margins at least of the tables are rocky. 



(a) Conditions: The buttes are more exposed to the winds. 

 Because of the increased elevation and wind they are cooler than 

 the steppe. In fact, excessively warm temperatures are nearly 

 lacking. Occasionally, when the clouds hang low, the buttes re- 

 ceive more precipitation, in the form of mist than do the lower 

 elevations. 



(b) The most conspicuous plant is the western red or yellow 

 pine (Pinus). The distribution of the pine is rather peculiar. It 

 grows most generally on the slopes, especially the north facing 

 ones, near the tops of the buttes. Locally it extends well down 

 to the base, or even beyond onto the plain (in the case of a valley 

 which heads in the southwestern part of the East Short Pines). 

 Consequently it is not elevation alone that limits their growth. 

 Neither is it slope alone for pines are found on the level top of 

 the West Short Pines and elsewhere, but near slopes. The more 

 probable explanation of the distribution is that pine seedlings can 

 with great difficulty resist the climatic conditions except where 

 protected by the slope or shaded by other pines which when they 

 were young were so protected. The occasional pine on the level 

 and not shaded by a pine which is on a slope is perhaps due to 

 unusually favorable conditions such as being buried in a gopher 

 hole. If slopes are here favorable to the growth of pine trees 

 the question may naturally be asked why pines are not found on 

 hillsides throughout the area. Four factors doubtless combine to 

 bring about this result, (i) The absence of seeds from which 

 pine might grow. The cones of seeds washed down from the 

 buttes are carried along the channels of the ravines and not de- 

 posited on the favorable slopes. The occasional cone favorably 

 dropt as to slope may be prevented from starting a tree by (2) the 

 thick cover of grass or by (3) prairie fires or by (4) the slope 

 being so rapidly eroded as to undermine the seedling. One or 

 more of the reasons is the cause for the lack of pines about the 

 numerous small rocky buttes of this region. The forest service 



