Feb. 16,1914 
Indicator Significance of Vegetation 
405 
flowering plants. 1 A condition which is almost always correlated with the 
presence of greasewood is a permanent supply of moisture available for 
growth within the depth of soil penetrated by its roots. 
GRASS-FLAT COMMUNITIES 2 
Topographical Relations 
The grass-flat of vegetation occurs in an interrupted belt (see map, 
PI. XUI), which crosses the northern part of the valley and lies 
between the area occupied by the main body of the greasewood-shadscale 
association and the salt flats. It covers a gently sloping or nearly level 
expanse and appears to be lower in elevation than some of the ridges and 
hillocks situated between it and the shore of the lake. The area is thus 
somewhat analogous to a coastal lagoon and may have had a similar 
origin. It is characterized during the greater part of the year by a very 
moist condition of the soil, due probably in part to seepage. 
Appearance and Botanical Composition 
The vegetation of the grass flats shows considerable diversity. 
Several plant communities can be distinguished, although the boundaries 
are rarely very sharp. The two most important of these are characterized 
by the dominance of (i) tussock grass, or purple top (Sporobolus airoides), 
and rabbit brush ( Chrysothamnus graveolens glabrata) , and (2) salt grass 
(.Distichlis spicata ). The rabbit brush is also frequently associated with 
greasewood (Sarcobatus vermiculatus) , especially along lines of contact 
between greasewood-shadscale areas and the grass flats. For the most 
part the vegetation of the grass flats is distinctly halophytic in character, 
but in limited areas around springs and flowing wells it resembles that 
of an ordinary nonsaline meadow. 
A list of the species which were noted as composing the grass-flat 
vegetation follows: 
perennial species 
Triglochin mariiima L. 
Triglochin palustris L. 
Distichlis spicata (L.) Greene 
Poa nevadensis Scribner 
Puccinellia airoides (Nutt.) Wats. 
Spartina gracilis Trin. 
Sporobolus airoides Torr. 
Juncus balticus Willd. 
Iris sp. (probably I. missouriensis Nutt.). 
Halerpestes cymbalaria (Pursh) Greene 
Dodecatheon sp. 
Glaux mariiima L. 
Aster pauciflorus Nutt. 
Chrysothamnus graveolens glabrata (Gray) 
A. Nels. 
Crepis glauca (Nutt.) T. and G. 
Iva axillaris Pursh 
1 At Grand Junction, Colo., young seedlings of greasewood were found growing where the soil to a depth 
of 2 inches, which was about the limit to which their roots had penetrated, gave a specific resistance of 36 
ohms, indicating the presence of at least 2.5 per cent of salts. 
2 The ecological status of the vegetation of the grass flats can not be determined until further investigations 
in the Great Basin region shall have been made. For the present, therefore, it seems advisable to use the 
general term “community” in referring to these types. 
24395°—M-4 
