29 August 1997

A copy of W. A. Laycock's review of your Draft EIS, Rangeland Health Standards and Guidelines, arrived on my desk. Of the EIS itself I have only eight pages from Chapter 3, so I can't say much about it. But my old associate Bill Laycock's strongly expressed ideas on utilization and diversity deserve comment.

Mr. Laycock is correct that utilization is misused by the agencies. It does not follow, as he claims, that utilization should not be used as a guide for stocking or that information on utilization in the Draft EIS is erroneous and should be removed. For example, Independent studies in the semidesert grassland over 75 years have been remarkably consistent in finding that less than 40% of black grama growth should be grazed (Havstad & Schlesinger 1996, Forest Service INT-GTR-338). It would be wrong to use this criterion by itself to set stocking levels, but I donI know anyone who advocates that.

Use-level does become devilishly hard to employ, though, in view of several-told year-to- year variation in forage production and in view of the desirability of grazing systems that affect the timing of use (for instance, more can be used in dormant-season grazing). To cut through these difficulties, a simpler criterion (but closely correlated with use-levels; see for instance correlations in Hedrick 1958, J. Range Mgmt. 11:34-43) is preferable: stubble height. Minimal stubble-height standards (of course incorporating some flexibility) cut through most of the difficulties of use levels. Keeping residue of specified height on the ground provides for plant health, erosion control, and wildlife habitat without worrying about averaging abstruse, difficult measurements of percentage use. For riparian areas, for instance, see Clary et al. 1996 (Rangelands 18:137-140). Mr. Laycock couples stubble-height with use-levels in his critique, but in fact gives no argument against use of stubble- height (except the valid one that the more local the standard, the better). I strongly recommend emphasis on use of stubble-height but not, of course, to the exclusion of trend data, and in some instances of supplementary requirements such as a percentage of seed- heads that should be left at the end of the growing season.

Mr. Laycock claims that improving mid-seral communities to high-seral will decrease species diversity. He could cite studies to support this generalization, for instance from sagebrush and aspen communities. In grasslands livestock grazing as it has been practiced (mainly season-long) has greatly decreased species richness; here in much of the Southwest it is the difference between a sea of bIue grama on grazed lands vs. patches of five to ten or more perennial grass species in adjacent cemeteries or other enclosures. Where livestock grazing does cause increases in species numbers, the added species are apt to be shrubs or annuals (often exotics) that come in where bare earth appears; hardly a desirable increase. Grazing pressure increases species evenness, so that a study that used meter-square plots would find more species per plot under heavy grazing (that is, fewer plots are needed to capture, say, 80% of all species) and might conclude that diversity had been increased when in fact there were more species in sufficiently large samples of ungrazed areas. My conclusions are that I do not trust the generalization that diversity decreases at high-seral stages and that even where that does happen, it is needful to inspect the nature of "increased" mid seral diversity. Diversity is, of course, a complex problem, not encapsulated by either Mr. Laycock's generalizations or mine; see West 1993 (J. Range Mgmt. 46:2-13) and West, editor, 1995 (Biodiversity on Rangelands, Utah State Univ. CoIl. of Natural Resources). My point is that you need not fear moving lands toward high-seral conditions because of lost diversity; even where species numbers decline, other elements of diversity such as patchiness will increase.

I guess that I'm moved to submit these comments because of the tone of Bill Laycock's critique: he has the answers and others (such as Jerry Holechek) are out of step with "range science." Neither range science nor the Society for Range Management is anywhere close to unanimous in these complexities. Bill is a master of the science but even the master must be taken with generous grains of salt.

Sincerely,

Roger Peterson
Santa Fe, NM
(ecologist, SRM member)

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