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<br />It was recognized that expectation of benefit to crop and range production is the primary
<br />reason for precipitation management efforts in the Great Plains. The effect of rainfall, acting
<br />through indirect effects on temperature, relative humidity, soil potential, fertilization, and soil
<br />moisture, is very important as a determinant of crop a.nd range production; but the relationships
<br />among these need to be better defined. An effort should be made to consolidate information
<br />from all completed studies and extend them into new areas.
<br />The vegetation of the Great Plains is being and will be determined by allocation of the land
<br />among different types of crops and native range, and by differences in cropping practices among
<br />continuous or alternate cropping, minimum tillage, fallowing, and irrigation. The effect of
<br />precipitation management on land allocations and cropping practices, and hence indirectly on
<br />vegetation, may become important especially if it were to lead to abandonment of water and soil
<br />conservation practices. In parts of the northern plains, vegetation and rainfall are interrelated in
<br />the saline seep problem that has been taking considerable land out of production.
<br />Changes in the community composition of native vegetation, and crop selection according to
<br />moisture, will probably cause changes in quality and quantity of range and crop species, with
<br />consequent changes in animal habitats.
<br />These changes would lead, eventually and indirectly, to changes in soil texture and organic
<br />matter, availability and distribution of nutrients, and the distributions of pests and animal
<br />populations. These items should be assessed as methods for addressing them become available.
<br />Possible offsite effects include shifts in competitive advantages of various sites, effects of
<br />additional municipal and industrial water on the regional economy, and demand for and
<br />production of energy, Of particular concern are the effects that precipitation management in one
<br />area may have on precipitation distribution in downwind areas.
<br />Mountain ecosystems.-For winter-orographic snowpack augmentation, a matrix table of
<br />concerns, sensitivities, and state-of-the-art was prepared, an abbreviated version of which is shown
<br />on figures 3 and 4. Better knowledge of the distribution of augmented snowfall with altitude, its
<br />redistribution on a local scale by drifting, and the effect of these variables on local duration of
<br />snow cover was identified as a key need, constituting the basis for analysis of effects on
<br />vegetation at high elevations.
<br />Somewhat lower in priority are the productivity of high meadows and of low elevation
<br />vegetation, decomposition, nutrient loss, and susceptibility to insects and disease. Concern for
<br />species-composition changes, forest productivity, nutritive value of vegetation, land use changes"
<br />species diversity, plant growth, phenology, reproduction, and endangered species were noted but
<br />rated low in priority.
<br />Offsite impacts were of high concern with respect to changes in land use and associated
<br />changes in vegetation types, with lower priority assigned to endangered species, vegetative
<br />productivity, growth, reproduction, and species. Concern was also noted for the possible offsite
<br />effects on vegetation if migrating big game were to be forced onto winter range unusually early in
<br />the season, causing overuse of the vegetation resource. A delayed beginning of the:
<br />precipitation-management season was recommended where this might prove to be a problem.,
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