BOOKS AND CURRENT LITERATURE 



Vegetation of Washington and Idaho. — A highly diversified area 

 of about 4000 square miles in southeastern Washington and south- 

 western Idaho, drained by the Snake and Palouse Rivers, has been 

 subjected to a very thorough ecological investigation by Weaver. 1 

 The several formations and associations are described in some detail 

 and illustrated, but the most notable feature of the work is the excellent 

 series of data on the critical physical conditions in the leading plant 

 communities. 



The western portion of the area is occupied by a desert scrub of Artem- 

 isia and Chrysothamnus. To the east of it are areas of xerophytic 

 grassland dominated by Agropyron spicatum and less xerophytic grass- 

 land formed by Festuca ovina. The transition zone between the grass- 

 land and forest is occupied by a shrub community of Symphoricarpos, 

 Opulaster and Rosa, which is sometimes improperly alluded to by the 

 author as "chaparral." The pioneer member of the forest communities 

 is Pinus ponderosa, closely followed by Pseudotsuga. The most impor- 

 tant forests of the region are made up of Larix occidentalis and Abies 

 grandis, and the climax is dominated by Thuja plicata. 



The investigation of physical conditions has centred chiefly in the 

 soil moisture and evaporation, which were determined at weekly inter- 

 vals from May to September. Data are also given on soil temperature, 

 air temperature, seasonal distribution of rainfall, and the chemical 

 composition of the soil. There is an irregular rise in the rate of evap- 

 oration and a steady fall in the soil moisture during the rainless summer 

 months. The graphs for these two conditions as determined in six of 

 the leading plant communities show a progessive fall in evaporation 

 rate and a rise in soil moisture as we pass from the Agropyron grassland, 

 through the Festuca grassland, the Opulaster scrub, and the forests of 

 Pinus and of Pseudotsuga to those of Thuja. In some cases the condi- 

 tions for Festuca and Pinus are quite similar. Readings taken at depths 

 of 2 and 10 in. indicate a progressive lowering of soil temperature as we 

 pass from one community to the next in the successional sequence given 



1 Weaver, J. E. A Study of the Vegetation of Southeastern Washington and 

 Adjacent Idaho. Univ. Neb. Studies, 17: 1-114; figs. 48; Jan. 1917. 



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