Comments on the EA for the

Alder Creek Project

Truckee Ranger District

Tahoe National Forest

 


Submitted on April 17th, 2006

By The Forest Issues Group

 

Before reviewing measures proposed by foresters, it is

appropriate to look for guidance in ecology, which is

supposed to provide the scientific basis of forest science.

Boris Zeide, 2005

 

 

 

 

Dear Terri Banka:

 

Thanks for this chance to participate in the management of resources on the Tahoe National Forest (TNF). We have submitted comments of a more general nature on the scoping letter for this action, reviewed the EA, and submit the following comments based on this review.

 

I)             Good response to Forest Issues Group (FIG) comments on the scoping letter.

 

The Scoping Comments Summary section of the EA provides clear and complete responses to all of our scoping comments. This sort of treatment by the Forest Service of public comments, and public participation in general, during the environmental review process, makes the process go smoothly and encourages public cooperation. The one exception involves Aspen Regeneration, and is addressed at III) below. We appreciate this effort.

 

II)                Alternatives not adequate

 

Decision makers are not well served if provided with only one real alternative, as is the case with this project. The public is likewise constrained in its ability to assess project merits. The FIG suggested using the values and guidelines of the 2001 SNFPA to frame an alternative, based on the fact that this original amendment reflects sound ecology and is less politically tainted than the revised version.

 

The Alder Creek EA at page 15 provides arguments against our preferred alternative. Essentially these arguments represent two approaches in support of excluding the FIG preferred alternative: Economics and Forest Health.

 

 

A)    Economics

The “Cost-Efficiency” part of this FS approach to support the relaxation of ecological constraints, (and thereby avoid the inclusion of the original SNFPA as an alternative), is based on supportive language in the revised version of the SNFPA. Since we are suggesting an alternative that would moot this (i.e. the 2004 SNFPA) document, the use of this language in the present context appears to be circular and inappropriate.

 

The “Timber Sale” part of the Economics argument is also problematic. If allowing the taking of 30 inch trees is more economical than restriction to 20 inch trees, it follows that… the larger the trees taken, the better the economics. At the same time it is well known and verified that larger trees are an essential feature of quality habitat. In this way a balance is begged, and indeed exists, between commercial and ecological goals. They are mutually exclusive. That is, you can’t pursue one goal without incrementally sacrificing the other. The original, science-based SNFPA found one balancing point (the 20/50 rule), and the revised version (and the Alder Creek project) proposes another such point (the 30/40 rule). This makes these opposing approaches well suited as alternatives for consideration by decision makers and the public, when attempting to find a way through the complexity of managing the ecology at Alder Creek.

 

The fact that in many stands on the TNF, the largest trees are in the 24 to 30 inch size range, means that the difference in the character of a residual stand under different SNFPA versions is not trivial. In this case, application of the less protective guidelines of the revised SNFPA could result in the removal of the largest trees in a stand. For example, in the Alder Creek stands referred to at EA pages16 and 17:

 

Stand #

     Ave. TPA

 24”- 30” DBH

Ave. TPA > 30 “ DBH

     1

         1.98

         0    

     2

         6.09

       2.27    

     3

         2.66

       0.84    

     4

         3.06

       1.31 

 

In stands 1, 3, and 4, application of the 30\40 rule (revised SNFPA) could eliminate the largest trees in the stand.  Application of the 20/50 rule would avoid this potential, and reduce by maybe 10 or more years the time to recovery of old growth attributes.

 

Consideration of this outcome differential at Alder Creek, by the FS and the public, can only be done if a real alternative, such as proposed by the FIG in our scoping comments, is before agency decision makers and the concerned public.

 

B)  Forest Health and the Stand Density Index

      Stand Demsity Index (SDI) is being relied on increasingly by the Forest Service in support of the need to include larger diameter trees in thin-from-below projects. These projects are often advertised as designed to improve forest health, and SDI has been identified as a useful index in evaluating forest health (Reineke, 1933; Oliver and Larsen, 1966; Alder Creek EA, 2006). However, as I have attempted to understand the SDI concept, I have become skeptical of its ability to support the need to harvest to larger diameters, as argued on pages 16 and 17 of the Alder Creek EA.

 

First I want to thank Larry Ford at the Sierraville Ranger District for helping me understand the SDI concept and its use in the Forest Vegetation Simulator (FVS) modeling software. I am still far from proficient in these matters, but I feel prepared to make the following observation:

 

1)   A test using analogous data.

The Phoenix project EA, currently under NEPA review by the Sierraville Ranger District, has provided an opportunity to study the ability of the FVS modeling software and the SDI to evaluate the need to include larger diameter trees in thin-from-below “forest health” projects like Alder Creek. FVS and the SDI were used by the Forest Service in the Phoenix project to determine whether use of the 20/50 rule in a thin-from-below project could effectively lower the SDI of four stands of different ecological types proposed for treatment as part of the Phoenix project on the Sierraville District. This Forest Service analysis used the same protocols proposed for use in the present (Alder Creek) project, except that FVS was not applied at Alder Creek. That is, present SDI was determined for the Alder Creek stands, but neither future SDI, nor any other stand statistics that are reported from FVS, were predicted.

 

I did a calibration run using FVS, the same observed data, a thin-from-below treatment following the 30/40 rule, and the same optional input values used by the Forest Service, and produced the same resulting statistics of stand structure, including an SDI value considered desirable by the Forest Service. This indicated that the FS and I were “on the same page”.

 

Then I did a run with the same observed data, but with a thin-from-below treatment following the 20/50 rule, and the same optional input values used by the Forest Service. The result, as expected, included an SDI somewhat higher than the maximum desired by the Forest Service. This indicated that the taking of larger diameter trees can result in a residual stand with a favorable SDI. It shows that one way to keep SDI under control is to cut larger trees. But is it the only way?

 

At this point my question became:  “can the desired SDI value be obtained by using the same observed data, the same thin-from-below prescription, and the more protective 20/50 rule, but by varying some other input parameter?”.

 

To look at this I did a run using the same input parameters, following the 20/50 rule in a thin-from-below treatment, but changed the target trees-per-acre (TPA) value from 120 to 90 (i.e. allowing more trees to be cut). Reported SDI was in the desired range.

 

This repeatable modeling exercise has shown, I submit, that increasing the allowable DBH cut limit, as proposed in the Alder Creek EA, is not necessary in order to obtain a suitable SDI, or to maintain stand health insofar as it is represented by SDI.

 

2)      Is SDI the appropriate metric, as it was applied at Alder Creek? SDI was developed for use in even-aged stands (Reineke, 1933; Ohman and Cohen, 1992). Can SDI accurately predict stand density in the un-even aged stands found at Alder Creek?

 

Woodall et al. (2003) suggest that leaf area index (LAI) is the best measure of site occupancy (but see Zeide, 2005 at page 3), or stand density. This measure is good because it represents photosynthesis/acre of the measured trees, but it is also very difficult to estimate (Cohen, 1990). Waring et al. (1982) have assumed that sapwood area (utilizing pipe model theory, Shinozaki et al. 1964) may be a good, and quantifiable, estimator of LAI. Making these assumptions, and to test the ability of SDI to predict site occupancy in un-even aged stands, Woodall et al. (2003) compared site occupancy predicted by sapwood area, to site occupancy predicted by SDI. Sapwood area was estimated from core samples of 5000 trees.

 

They conclude that “(t)he summation method of calculating SDI [which is the method developed by Shaw (2000) and used in the FVS model (see FVS user guide page 153) added by sb] is biased in its apportionment of site occupancy across diameter classes in ponderosa pine stands” and  “…should only be applied in un-even aged stands if one is cognizant of the effect of diameter distribution on SDI interpretation.” (Woodall et al. 2003).

 

With respect to using Reineke’s SDI even for even aged stands, Boris Zeide (2005) finds that:

“A thorough, though not entirely consistent, examination of Reineke’s index was done by Spurr (1952) known for his unmatched ability to produce textbooks in diverse fields. In one of those, while acknowledging that the correlation of stand density index with age is much lower than that of basal area, he still concludes that “since basal area is apparently fully as satisfactory as stand-density index in most cases, because it is simply obtained, and since it is a finite value in comparison to stand-density index which is an approximate value, it is to be preferred as a measure of density” (Spurr 1952, p 282).

 

Spurr’s view was endorsed by the Committee on Stocking of the Society of American Foresters, which, after 8 years of deliberation, found that Reineke’s index changes with tree size and age and decided that the index ‘does not appear to be a good measure of density’ (Bickford et al. 1957, p 102).”

 

Zeide (2005) adds that:

“It may be that Reineke’s index is not a good measure of density, but it is still the best we have (when used in even aged stands [added by sb]). At least it does not lead to the confusion between overstocked and understocked stands of the same species. However, the relationship between the number of trees and diameter may not be as simple as Reineke believed.”

 

See also Weller 1987,  Enquist et al. 1998, and  Ferguson and Leech (1976 citation missing) for similar criticism of the Reineke formulation.

 

Note: A descriptive document for the FVS variant (WESSIN) used by Sierraville describes a method employed in the WESSIN variant to mitigate the bias reported here for SDI. This is not consistent with the statement quoted above from the FVS user manual. I have not found any assessment of the effectiveness of this fix in removing the bias complained about in Reineke’s SDI formulation.

 

3)   How consistent has the assignment of the SDI values to species been? How consistent has the assignment of the SDI values to the same species in different variants of FVS been?

 

Since SDI for the stand is based on the species specific stand density values of the trees that comprise the stand (for example maximum SDI value FVS assigns SDI for Douglas fir on the TNF = 547; Jeffery and ponderosa pine on the TNF = 571; red fir on the TNF = 800) resulting SDI is quite sensitive to the SDI values assigned to the species that make up the stand. I have found recommended values for SDI that vary widely for the same species. For example, the maximum SDI values for the three species listed above are 600, 800, and 1000 for an unspecified region (University of Missouri website). These values would lead to higher maximum densities at similar levels of forest health.

 

Protocols for assigning SDI values to species for use in FVS do not appear consistent. For example, the values of maximum SDI assigned to species in the WESSIN variant (used on the TNF) “were specified for this variant by Region 5 (Ralph Warbington, RO staff) based on published ‘average maximum’ values”, and the SO variant (southern Oregon/northern California) assigns SDI to plant associations, rather than to single tree species. The process of SDI assignment needs clarification.

 

 

4)      Silviculture vs. Ecology

Reineke’s SDI is a silvicultural, not an ecological, tool. The following quotation indicates the traditionally solid identification between healthy or “normal” stands and product yield.

 

In the past, it was believed that normal stands produce maximum

total yield and, therefore, are the goal of management, as

the very term “normal” indicates. Tursky’s silviculture

(2000, p 12), compiled at the end of the nineteenth century

from several classic German Waldbau’s (textbooks of

silviculture) and recently reissued as the ninth edition, is a

good example: “The stand is called normal when it is

dense, healthy, and when, for a given species composition,

age, and site, it produces the maximum yield of the best

quality wood.” A normal stand was still defined as “that

producing the maximum possible volume in cubic feet for

a given age and site (thinnings usually being disregarded)”

well into the last century (Committee 1926, p 659).

(Zeide, 2005.) (Emphasis added.)

 

      The historic goal of forestry has been fiber yield, (though the mission of the Forest Service has been broader from the start) and we suggest that Reineke, in his effort to measure stand density for use in managed forests, equated forest health with fiber yield as described in the above quotation. We suggest that tools devised to serve single-purpose, yield-oriented management are not necessarily suited for service in modern forestry, especially when they are used, as they are at Alder Creek, to support the pursuit of a goal (taking larger diameter trees) that is widely considered to be incompatible with modern, ecology-based forestry. Forest health means, or should mean, something different to the designers of the Alder Creek project than it did 80, 60, or even 40 years ago at the height of mechanized harvest activity in western forests.

 

      The Forest Service argues (e.g. Alder Creek FEIS at page 17) that allowing a stand to increase in density beyond the SDI threshold, as in an epidemic, can lead to mortality that results in reduction of density “far below the density that triggered the epidemic”. Yet on the same page we read that “Thinning to a 30 inch diameter limit would allow residual trees room to grow for a longer period of time, before the SDI again approaches the threshold of mortality”. Here the Forest Service acknowledges that “over-thinning” is a potential good, but insists that it is better to do it with chainsaws than to let nature and the self-thinning function of the conifers do the job themselves. Please note that we are not opposed to thinning, only to the raising of the cut limit provided by the revised SNFPA, and to the use of the SDI concept in support of this change.

 

We have shown that Stand Density Index has the following problems that should preclude its use, as attempted here, to support of the relaxed cutting limits of the revised SNFPA, and the elimination of the 2001 SNFPA from consideration as an alternative in the Alder Creek project:

 

·        The SYSTUM-1 model as used here with a thin-from-below prescription can be adjusted to report suitable SDI values without the taking of 30 inch dbh trees. This makes its use in support of the 30/40 rule suspect or illegal, and its use in support of the elimination of the 2001 SNFPA from consideration as an alternative in the Alder Creek project unjustified.

·        The SDI was developed for even-aged stands, and is considered marginally suited by some experts even for that limited application. It is not considered appropriate for use in un-even aged stands as proposed in the Alder Creek EA. Its use in support of the 30/40 rule is suspect or illegal.

·        The SDI is a product of traditional, single-purpose, yield-oriented forestry. It does not account for stand attributes that qualify habitat, or for other values that might be considered part of the ecological forest system. Its use in support of the 30/40 rule, or in support of the elimination of the 2001 SNFPA from consideration as an alternative in the Alder Creek project, is not justified.

 

For use in modern forest management the SDI should be complemented with some measure of true forest health. Maybe natural or historic range of variability as described by Reed Noss and others (2006) would produce, in some combination with SDI, a measure of forest health that would achieve both silvicultural and ecological goals for use in the desired condition section of NEPA documents.

 

III)      Aspen Restoration

           

We support the concept behind the effort to re-establish Aspen stands. We recognize the ecological importance of this habitat for dependant species, and the need to facilitate expansion of the type toward an acreage that approaches the natural range of variability, or the proportion of the landscape it occupied in pre-fire-suppression days. We submit that this effort will be more likely to succeed if the following conditions are met:

 

 

 

We suggest that the Aspen Regeneration issue needs to be further developed at the level of Forest wide planning. Aspects of the program as we understand it now, including the taking of very large, rare, conifers, and the apparent unlimited spatial scope proposed for stand treatment, indicate a project whose design is “in-progress”.  The caveats we provided in response to scoping for Alder Creek continue to apply, so we have repeated them here.

 

 

Thanks again for the opportunity,

 

 

Stephen Benner for the Forest Issues Group

Box 191, Sierraville, CA. 96126

           

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

References Cited

 

 

 

 

Cohen, W. B., & Justice, C. (1999). Validating MODIS terrestrial ecology products: Linking in situ and satellite measurements. Remote Sensing of Environment, 70, 1–3.

Cohen, W. B., Maierpserger, T. K., Gower, S. T., & Turner, D. P. (2003).  An improved strategy for regression of biophysical variables and Landsat ETM+ data. Remote Sensing of Environment, 84, 561–571.  Semivariograms of digital imagery for analysis of conifer canopy structure. Remote Sensing of Environment, 34, 167– 178.

Committee on standardization of volume and yield tables (1926) Methods of preparing volume and yield tables. J For 24:653–666

Enquist, B.J., Brown, J.H., and West, G.B. 1998. Allometric scaling of plant energetics and population density. Nature (London), 395: 163–165.

Noss, R., Franklin, J.F., Baker, W., Schoennagel, T., and Moyle, P. 2006. Ecological science relevant to management policies for fire-prone forests of the western United States. Society for Conservation Biology Scientific Panel on Fire in Western U.S. Forests. Executive Summary

Reineke, L.H. 1933. Perfecting a stand-density index for even-aged stands. J. Agric. Res. 46: 627–638.

Shaw, J.D. 2000. Application of stand density index to irregularly structured stands. West. J. Appl. For. 15: 40–42.

Shinozaki, K., Yoda, K., Hozumi, K., and Kira, T. 1964. A quantitative analysis of plant form — the pipe model theory. Jpn. J.  Ecol. 14: 97–104.

Stage, A.R. 1968. A tree-by-tree measure of site utilization for grand fir related to stand density index. USDA For. Serv. Res.  Note. INT-77.

 

Weller, D. 1987. A re-evaluation of the –3/2 power rule of plant self-thinning. Ecol. Monogr. 57: 23–43.

Woodall, C.W., Fiedler, C.E. and K.S Milner, 2003. Stand density index in uneven-aged ponderosa pine stands. Can. J. For. Res. 33: 96–100

 

Zeide, B., 2005. How to measure stand density. Trees 19: 1–14