WMOD00409

• Contract/Permit #: 1-07-81-V0175
• Title: State of Montana Activities in the High Plains Cooperative Program: 1981-1983
• Date: 6/30/1983
• State: MT
• Weather Modification - Doc Type: Report

Weaver (1954) declared. in reference to water erosion. that the .t. . . most
formidable line of defense by prairie grasses against erosion is 'above ground.
. . .n By this he meant grass foliage characteristics greatly influence
erosion susceptibility. He experimented on the resistance to water erosion of
five grass species and found the two C3 species lost soil the fastest. For
instance. AndroDogon gerardi sods took twice as long as Stipa comata sods to
erode completely. Yet he did acknowledge Bromus inermis. an introduced C3
grass. as a good soil binder. In a related series of measurements. Weaver
determined that AgroDyron smithii stands absorbed water at the slowest rate of
any plant cover. being nearly as slow as bare ground areas. whileC4-type
grasses absorbed water at the fastest rates. Weaver's explanation for the poor
water infiltration capacity of Agro~yron smithii may explain well its wind
erosion susceptibility. n. . . this grass had furnished little debris during
the drought years. and much bare ground was exposed." Point frame measures of
the total ground cover'are about two-three times greater on the Bouteloua than
Agropyron site under study here (T. Weaver. personal communication).

Two implications of these data and my interpretations are: 1) ecosystem
development in the northern Great Plains and similar semi-arid but cool regions
may proceed towards the incorporation of both C3 and C4 grasses as a nutrient
conservation mechanism (Odum. 1969); -2) incorporation of C4 grasses into land
reclamation or-range renovation seeding mixtures and management to ensure the~r
survival may lessen ecosystem nutrient losses from wind erosion.

Table 1. Debris weights g/O.l m2. x .:t 1 SEt of suction samples as affect,ed by
soil moisture regime at the A~roDyron smithii community in 1979. Treatments
are CTL. ambient precipitation; SWT. moist soil until about July 1; and WET
moist soil throughout the growing season. Experimental replicates (n=lO) are
separated in the table. Analysis of variance. p<O.05. showed significant soil
water ~ffects on each sample data. Sim~lar letters indicate equivalent means
on each date. paired t-test. p>0.05.

SOIL MOISTURE REGIME
CTL SWT WET
Date 1 2 1 2 1 2
5/23/79 19.9a 33,.7 a 9.5b 25.7a 3.3a 8.4b
4.7 9.4 ' 2.3 3.1 0.9 2.2
6/19/79 l3.3b 25.3a 2.1d 5.9c 0.8d 3.5cd
3.0 5.0 0.8 1.4 0.2 1.3
7/19/79 18.3a 20.1a l2.5a 3.2b 0.5c 3.0b
3.2 5.1 4.6 0.5 0.1 0.6
8/16/79 8.6b l4.5a 3.1c 5.7c 1.4d 3.6c
2.4 4.4 0.8 1.4 0.3 0.9
9/08/79 4.7a 6.5a 1.3b 4.8a 0.6b 1.2b
1.4 1.9 0.4 1.0 0.2 0.3

64