38 A Study of the Vegetation of 
termine the relation between this factor and succession. Read- 
ings at depths of 2 and Io inches respectively, were taken at the 
same stations and at the same time that soil samples for moisture 
determinations were secured. In addition to these a large number 
of readings near the soil surface, in the soil surface, and at depths 
of one and two feet respectively, were made from time to time. 
Many of the temperature readings were made simultaneously, and 
in all cases recorded the interval between the readings at the 
various stations was so short that the error thus introduced is 
almost negligible. This possible error was further reduced by 
taking the readings in the various habitats at any set of stations in 
varying sequence. 
An examination of these data shows almost uniformly a de- 
crease in soil temperature as the climax communities are ap- 
proached. The following tables, selected as representative from 
these data, are illustrative: 
TABLE V 
SHOWING THE RELATION OF SoIL TEMPERATURE TO PLANT SUCCESSION 
Colfax, Wash., 1913 
Agro- | Festuca| Pinus | 4870- | Festuca| Pinus 
yr" | Conso- | Conso- | £¥”%°% | Conso- | Conso- 
Conso- | ciation | cies -OnSO- | ciation | cies 
clation clation 
Depth, 2 Inches Depth, 10 Inches 
Ma Gee Salta sce 200Ci S27) lers2O-ulst370 6.0 
UNELOsayevers wists sissies BU) | 2052 | Lees) IREOLS) ecSsOn dencso 
UME ZO a oe ee eeehree T7.5 | Ore) r25 WS ye eS Los el OrAcm iE 
INES 204 eal ten eae eee 22.5, | E750 | 22-5 120.0% |"76.5 4) Teisha oP Me 
RUM 2 OR ceierrentetie ee Zee. stirs 13.0) WW LQ.0%4- 57-07 || e255" One aie 
NOIR Ae: (Aeon e Oe PoE Te crt y- 29.0) | TOL5) i|05-0) 11)-2'7.0 55) TOCOe4| Ay 
MPU yy 2 Tea, a eter opets Peters Be 26.5 | 23.0 | 18.0 | 25.5* | 22.0* | 16.7* | 9:15 A. M. 
nly So Tel S toe never tase 28.0) 922.5 17-5 | 27.07 | 24.0 | 1710" er: so eae 
ly s2T Ata serach ee 32.5) |22'0. 'r8.0 || 2o25* 4) 25.0" ns © lore ee 
Wliy; SOu ens esters aetna 35.0 | 22.0 | 14.0 | 28.0* | 20.0* | 14.2* 
AUSUSE D3) ce chet ter 20:5 |i 28.52.) L5.0* | 22.0) || 7835) cA 
AUSUSE Hersh oi eiiicle 26:5 -)|°20.0) {)15.0) |]22.57 i rsco. Aro 
September 10......... 2225 SUS On nrc Il TOas 14.5 12.5 
* Readings taken at a depth of 4 inches. 
38 
