78 CARNEGIE INSTITUTION OF WASHINGTON. 



Further work has been inaugurated with the purpose of following 

 the surface changes in the playas of the Avra Valley and on the bajadas 

 of the Sierrita Mountains, in view of the importance of these changes 

 to the vegetation. The isolated bench-marks previously used have 

 been replaced by series of metal marks established both in the stream- 

 ways and on the bajadas and playas transversely to the drainage. 

 Semi-annual measurements at these marks will indicate the amount 

 of erosion or deposition in the very unstable surfaces of the playa and 

 the fluctuations in gradient and caiTying power of the streamways. On 

 the bajadas the principal interest is in securing a measure of the lateral 

 oscillation of the streamways, which is believed to be responsible for 

 the character of these long slopes of uniform gradient which are so char- 

 acteristic of desert topography. 



Ecology of the Santa Lucia Mountains, hy Forrest Shreve. 



The work begun in 1918 on the Santa Lucia Mountains, which skirt 

 the coast of central California, was again taken up in the summer of 

 1920. The work of the first year showed some differences in the floris- 

 tic composition of the vegetation in the nothern part of these moun- 

 tains near Monterey and in the southern part near San Luis Obispo 

 and Santa Margarita. From the ecological standpoint, however, 

 there is great uniformity throughout their north and south extent and 

 the same types of vegetation recur repeatedly. As the northern end 

 of the range comprises the highest elevations, as well as the entire series 

 of characteristic plant communities, more intensive work has been 

 confined to the region north of the Arroyo Seco. 



Further exploration of this portion of the range has strengthened 

 the observation that no constant differences of vegetation exist between 

 the seaward and landward slopes. While such communities as the 

 redwood forest and the very open forests of digger pine {Pinus sabi- 

 niana) are respectively confined to these slopes, they are very far from 

 being coextensive with them, and the main divide between the drainage 

 into the Pacific and that into the Salinas River is in no respect a vege- 

 tational boundary. Although the known differences of rainfall on the 

 coastal and landward sides of the range are considerable, the rainless 

 character of the greater part of the growing season reduces the influ- 

 ence of the sea to the narrow coastal belt and the larger valleys which 

 are frequently visited by fog. 



On the higher elevations of the Santa Lucia Mountains may be found 

 the Coulter pine {Pinus coulteri), sugar pine (P. lambertiana), yellow 

 pine {P. ponderosa), Santa Lucia fir {Abies yenwsf a) , canyon live oak 

 {Quercus chrysolepis), and a considerable number of shrubs and herbs, 

 none of which is found at the lower elevations. However, there are 

 very many trees and shrubs that occur throughout the vertical range of 

 slightly over 5,000 feet and there are communities at the latter eleva- 



