BULLETIN 791, U. S. DEPARTMENT OF AGRICULTURE. 
The second-weed stage is characterized by a fairly well decom- 
posed soil. The improved condition of the rock as a habitat for 
plants which results from the formation of soil is obvious. This is 
particularly evident when we recall that the rate of succession is 
largely determined by the moisture conditions of the substratum. 
r 
^ 
Deep rooted or- densely 
tufted rather shallow 
roofed perennial grasses, 
other vegetation almost 
entirely lacking. 
[Final or Climax Stage) 
, 
Loamy, fine grave /ly So// 
r/ch /n organic matter^ 
avai/ab/e moisture content] 
high. 
A 
Perennial herbs, ch/'ef/y 
weeds, Mf/th scattered stand 
of aggressive grass e s. 
somef/mes an occasional 
Shrub in evidence. 
(Second Weed Stage J 
« > 
Loamy, s/ighf/y grave //y 
So// with moderate amount 
of organic matter ava//- 
able;mo isture content 
moderate to h/gh. 
, 
. 
£~ar/y maturing annuals 
and shallot* rooted short 
Grave l/y /oem,soi/ poor /n 
organic matter; avai/ab/e 
moisture content mod- 
erate to /ow. 
/ived perennial herbs. 
(P/rst Weed Stage J 
• 
Poj/aceous L/cfrens and 
Mosses with sparse stand of 
Course, grave l/y semi- 
decomposed roclc, avail- 
able mo isture; content /ow 
ear/y maturing annual herbs 
(Transitional ' StageJ 
"' ' ; 
i 
- 
A/gae and Crustaceoos L/'c/>ens 
(In/t/al or P/oneer Stage J 
* 
&<are rocA- -format/on. 
C//7/t/<a/ /Jecomposif/o/TJ 
SO/L PrIASP 
yfGFTA 77K<f" Pf/ASE 
1 
; 
VPe£TAT/VE MDJOIL. POPh/AT/OH 
Fig. 1. — Plant succession or the development of vegetation where grass constitutes the 
climax or subclimax type. 
The soil upon which the second-weed stage develops, being mod- 
erately well impregnated with organic matter, is fairly moist 
throughout the growing season. This condition permits the estab- 
lishment of a stand of perennial herbs of varying density, the weedy, 
unpalatable species often predominating. These, in addition to an 
admixture of bunch grasses and often of turf -forming species as well, 
