WSP06813

• File Number: 8273.400
• Description: Colorado River Basin Salinity Control - Federal Agency Reports - BLM
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 2/1/1980
• Title: Control of Salinity from Point Sources Yielding Groundwater Discharge and from Diffuse Surface Runoff in the Upper Colorado River Basin - 1978-79 Status Report
• Water Supply Pro - Doc Type: Report/Study

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Rauzi and Zingg (36) compared water intake data from many sites over
seven Great Plains States, representing a 'variety of soils and climate.
Water intake was significantly greater on ranges in good condition than
on those in poor condition, irrespective of soil texture. McGinty et al.
(30) found no significant differences in infiltration rate be~ween a 4-
pasture grazing system and a long-time enclosure, both presumably in
good condition.

Buwai and Trlica (8) and Trlica et al. (39) conducted defoliation studies
on a :'~,,1iarid northwestern Colorado rangel and. These data indicate the
effects of defoliation on plant health depend upon the species of plant,
stage of growth (phenology), and number of defoliations. A number of
plant species produced smaller herbage yields and showed reduced vigor
following multiple defoliations at a moderate level. They were most
, severely affected by heavy defoliations. A number of plant species
'recovered within 14 to 26 months after a single heavy defoliation.
Plants clipped when green or during the rapid growth stage did not make
complete recovery following the rest period. Cook and Childs (12) state
that plant vigor may have also been affected by the harsh conditions of
the desert site. The implication is that desert ranges in the Inter-
mountain area are in a delicate natural balance and can deteriorate
rapidly if not used correctly.

Laycock (24), using species composition and plant vigor as indices of
change, found desert ranges in poor condition improved when grazed only
in the fall, while those in good condition deteriorated under spring
grazing, Cook (11) found 60 percent util ization of cold desert plants
during winter was too severe to maintain plants in good vigor. The rate
of recovery of plants from defoliation was also proportional to the
initial state of plant vigor. Plants grazed when in low vigor were
slower to recover under complete rest. It was suggested that 50 percent
utilization would maintain optimum vigor and sustained yield.

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Costello and Turner (13) ,during a study of more than 100 exclosures,
found that recovery of perenni a 1 vegetati on (especi a lly shrubs) from
effects of grazing was very slow under natural conditions. Exclosures
over 30 years old showed the greatest percentages of the highly pala~
table plants. Willard and Herman (42) report that improvement in range
condition is slow on the Northern Great Plains, even under grazing
management. This was true for grazing systems that did not allow at
1 eas t one full year of rest for pastures duri ng the grazi ng cycl e.
Greater improvement in soil and plant conditions was observed from
winter grazing than from rest-rotation. This was attributed to frozen
soils, reducing the effect of livestock trampling on soil . compaction.

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