Principle – Ecological Integrity

Criterion- Genetic Diversity

Indicator – Management does not significantly change gene frequencies.

Box B: Definition:

The potential for changing gene frequencies through harvesting activities is ever present, regardless of the method used. "High-grading" is the term commonly used to describe the genetic consequences of selective removal of the best trees over several generations. Gene frequency change may be induced intentionally or unintentionally, through other forest practices as well.

Box D: Applicability to Different Landowners. Explain any differences:

All landowners can avoid high grading and other practices that may result in genetic degradation.

Box E: Overlap:

None

Notes:

The effects of harvest practices are most readily seen at the level of tenure or site.

Notes:

The indicator is diagnostic in its reflection of the effects of forest harvest methods on gene frequencies. It will also predict the future genetic condition of the forest given continuance of current methods.

Notes:

The indicator reflects a process of forest harvest - mediated phenotypic selection that may influence gene frequencies.

Box I: Underlying Concepts:

When there is little advanced regeneration, and only poor quality, slow growing trees are left after cutting, dramatic changes in gene frequency for quality traits may occur (M.F. Mahalovitch, pers. Comm.). Ledig (1992) suggested that the pitch pine (Pinus rigida Mill.) form and growth rate that is commonly observed today may be the result of high grading over three centuries. "Eugenic" harvesting practices favoring the fast growing and well formed trees may change gene frequencies in the other direction and may unintentionally influence gene frequencies of associated traits. To mitigate these effects, reserve areas well buffered from managed areas, where trees are not selected in either direction, will maintain the "natural" gene frequencies, if the populations are large enough to avoid effects of genetic drift and migration.

Harvesting practices can change gene frequencies, when rotations are very short, by preventing late maturing individuals from successfully reproducing. Gene frequencies may also be shifted by harvesting in a way that not match the normal successional status of the harvested species. For example, clearcutting shade tolerant species selects for individuals that perform best in full sun, as partial cutting shade intolerant species would select for those individuals that can grow relatively well in partial shade.

There is little hard genetic data on the effects of forest harvesting on gene frequencies in any forest species, but anecdotal information abounds (Ledig 1992). For example, Styles (1972) considered that mahogany (Swietenia mahogani L.) has been reduced to a multi-stemmed shrub in the Caribbean because of selective logging of the best trees. Ledig (1992) described the present form of pitch pine (Pinus rigida Mill.) as a consequence of hypothesized genetic degradation as a result of high grading.

Late successional, shade tolerant species are generally less likely to suffer the effects of high grading than are early successional species. Historical accounts of the forests of eastern Canada, for example, include writings by the government agent, Moses Perley who described a straighter, taller, better quality tamarack (Larix laricina (Du Roi) K. Koch) than that observed today. The species is intolerant of shade so would not have regenerated under its own canopy, and it was in great demand during the ship building era.

Potential effects on species in the understory lacking recognized commercial value are less known, though in some cases they are likely significant. The effects at this level would not result from high grading, but from habitat shifts as a result of logging.

Namkoong et al. (1997) proposed "Directional change in allele or genotype frequencies" as an indicator of genetic sustainability. They argued that in addition to the conscious selection that occurs in a high grading situation, indirect selection effects may also result from correlations between traits. Another indirect select effect could result from dependency of another species on a certain size or age class of the targeted species.

Box J: Relevance to Sustainable/Unsustainable Management :

Directional change in gene frequencies as a result of forestry operations may cause populations to lose adaptive fitness to the local environment either under present conditions or if the management practices change or end. Effects of high grading may lead to economic losses, and unintentional selection on associated traits may lead to ecological loses.

Box K: Measurement Methods:

In evaluating genetic indicators, first the target species and populations must be identified. In general the species that are chosen should be sensitive to forestry practices that are being carried out in the region

The choice of species evaluated should not be limited to those for which the most information is available but instead should be based on an assessment of the likely effects of past and present forestry practices. This could be done as follows:

1. With the assistance of local experts, categorize native tree, shrub and, if possible, herbaceous species in the study area, including species with little or no commercial value, according to silvics and habitat requirements; e.g. shade tolerance, moisture requirement, etc.; and by range and frequency reduction or expansion in study area compared to reference (historical) levels.
2. List forestry intervention including proportion of study area treated by each method, and predict impact on gene frequencies of species on the basis of silvics, habitat requirements, range and frequency.
3. Identify those species that are expected to be impacted by the identified harvest methods.Considerations in determining whether or not directional gene frequency change may be occurring in a species as a result of forestry practices:

1. Does the cutting practice suit the silvics of the species; eg. does the predominant harvest method provide for the shade conditions required by the species?
2. Is the species selectively harvested and, if so, how? E.g. do all trees reach reproductive age before being harvested? Does the selective harvesting have the potential to change gene frequencies?
3. If the species is normally regenerated after fire, is there potential for directional gene frequency change occurring as a result of fire suppression?

4. Among those species that are known or suspected to be susceptible to directional genetic change as a result of forest practices, choose several representing different impacts. For example, the assessor might choose one species that is being selectively harvested throughout much of the study area, one species of little commercial value that is commonly associated with the harvested species, and one species that does not respond well to the prevalent harvesting practices.
5. Monitoring may be carried out at different levels of intensity. The simplist level is determining whether there are adequate unmanaged reserves of each species in the study area. The second level involves establishing sample plots in the target areas and in reference areas where forestry interventions are not occurring, and monitoring the natural regeneration for phenotypic traits that would be expected to show effects of directional gene frequency change as a result of forest harvest. Monitoring would be long term. A more labor intensive method that would provide better genetic information would involve collecting seed from the remaining seed trees in a random sample of areas where the target harvesting practices occurred, as well as from reference areas. Progeny tests would be established in common environments, designed to evaluate genetic effects of the harvesting practices.

In the southwest Idaho study area, a useful set of species to evaluate might be Ponderosa pine (primarily harvested by selection), lodgepole pine (planted off-site in past, not well suited to selection harvesting), and a shrub species, such as Symphoricarpos albus (common snowberry), that is commonly associated with ponderosa pine.

Box L: Data Required:

The required data includes:

• the harvesting methods that are used in different habitat types and the harvest rules (obtainable from local foresters).
• existence of unmanaged reserves for the commercial forest species
• baseline data from reference populations, either phenotypic means and variances or genetic parameters depending on the level of monitoring that is carried out.
• phenotypic or genetic data collected from harvested areas or tests with seed from remaining trees in harvested areas.

Failing the availability of the above data sources, any documented effects of forest harvest on target species if such descriptions exist, would be useful.

Box M: Data Used for the North American Test:

There are no data available to assess the genetic effects of harvesting practices. No formal monitoring is carried to assess existence or effects of high grading occurring in the study area.

The only source of information was through discussions with other CIFOR team members who are located in Idaho and from forest geneticists located in the State of Idaho. They described harvest methods and rules that are applied in this area, and gave their opinions with respect to genetic effects.

Box N: Example Results:

Almost all harvesting is by some form of selection cut or small patch cut and is described as selection from below. In other words, the slower growing, poorly formed, diseased or otherwise undesirable trees are removed first and the well formed, fast growing trees are allowed to regenerate the stands.

However, there is not complete agreement on this question. Two forest geneticists expressed concerns about high grading.

From the economic perspective, selection harvesting methods that ensure retention of the largest, best formed trees, are sustainable, and far preferable to harvesting the best first. However it still has the potential to shift gene frequencies, to select gradually for economically valuable traits, which may not be the most important adaptively in the long term.

There are no "unmanaged reserves" that are specifically designated to maintain natural levels of gene frequency, but there are many such de facto reserve areas in the National Forests that would be expected to cover all species.

There are no data on the effects on the associated species.

A focused monitoring program to address this issue would be very useful.

Box O: Assessing the Practicality:

The phenotypic component of this indicator could easily be tracked for harvested species and for traits that may be directly selected against, more difficult for associated species in the understory or for indirectly selected species.

Box P: Assessing the Information Value:

This indicator, especially when monitored over time will provide useful information to managers and other stakeholders. If the indicator drops, targeted genetic studies should be initiated to track potential genetic consequences.

Box Q: Overall assessment:

Accepted

Strengths – measurable, there is a good probability that if the indicator is negative, species gene pools are being affected.

Weakness – the indicator may not give us a direct measure of the genetic variability, and will not provide information about traits that may be selected for indirectly.

Box R: Did you rewrite or revise to a new indicator. If so what?

This is a new indicator.

Box S: References:

• Canadian Council of Forest Ministers. 1997. Criteria & Indicators of Sustainable Forest Management in Canada. Technical Report. Cat. Fo75-3/6-1997E, ISBN 0-662-25623-9. Natural Resources Canada–Canadian Forest Service 8th floor, 580 Booth Street,Ottawa ON
• Ledig, F.T. 1992. Human impacts on genetic diversity in forest ecosystems. OIKOS 63:87-108
• Namkoong,G., T. Boyle, Y. El-Kassaby, G. Eriksson, H.-R. Gregorius, H.Joly, A. Kremer, O. Savolainen, R. Wickneswari, A. Young, M. Zeh-Nlo, and R. Prabhu. Criteria and indicators for assessing the sustainability of forest management: consideration of genetic diversity. AMBIO. (submitted 1997)
• Styles, B.T. 1972. The flower biology of the Meliaceae and its bearing on tree breeding. Silvae Genet. 21:175-182.

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