Evaluation of the proposed interim indicator 4.1e

3.1.8 Evaluation of the proposed interim indicator 4.1e

At the inception of the various WAPIS research projects that were framed to address Montreal Process Criterion 4, a protocol document to guide procedures of research and data interpretation was developed by the Project Steering Committee. This measurement protocol included guidelines for applying the Interim Indicators proposed in the criteria and indicators framework document published by the Montreal Process Implementation Group (1998). The protocol is included in the current report as Appendix 1. The following section examines the results with reference to the interim indicators outlined in the Protocol.

Area and percent of forest land with significant soil erosion The interim indicator 4.1e (MIG, 1998) is “area and percent of forest land systematically assessed

for soil erosion hazard, and for which site-varying scientifically based measures to protect soil and water values are implemented”. In the case of this harvesting operation and all operations in this region, the entire coupe, 55 ha or 100% in this case, is assessed for erosion hazard. In other words, 0% of the area is not assessed for erosion hazard, whereby non-assessment represents a negative contribution to sustainability.

Raison and Rab (2001) and the measurement protocol (Appendix 1) proposed that the area and percent occupied by access roads, fire breaks, log landings, snig tracks and subsoil-disturbed areas was an approximation of the “area and percent of forest land with significant soil erosion”. This amounted to 20% of the coupe for both survey methods.

Area and percent of forest land with significant compaction or changes in physical properties The MIG (1998) framework document proposed an interim indicator: “proportion of harvested

forest area with significant change in bulk density of any horizon of the surface (0-30 cm) soil”. The protocol document (Appendix 1) uses a similar approach, but is more specific in defining significant change as areas with;

greater than 20% increase in bulk density in the 0-300 mm depth; aeration porosity less than 10% in the 0-300 mm depth.; and areas affected by S3 disturbance that do not satisfy the bulk density change condition; The reference comparison for bulk density is undisturbed soil. We examined change for both the 0-

100 mm disturbed core samples and the averaged value of the 0-100, 100-200, and 200-300 mm undisturbed core samples to represent the 0-300 mm depth. We compared post-harvest bulk densities with the respective pre-harvest sample mean. Only one sample from the 0-300 mm depth exceeded the 20% increase criterion (Figure 18). For the 0-100 mm disturbed core samples, 21 of the 180 post-harvest samples, or 12%, were more than 20% higher than the pre-harvest mean value. Only two samples taken from S3 disturbance did not have a 20% or greater increase in bulk density. None of the samples with less than 20% change in bulk density had aeration porosity below 10%. When scaled to account for the proportion of the coupe surveyed, these results suggest that around 7% of the total area of the coup was affected.

Although soil strength is not included in the interim indicator, we adopted the same approach as bulk density for this parameter. Strengths recorded between 25-300 mm were averaged to give a 0- 300 mm value. Around 19% of penetration resistance measurements in the 0-300 mm depth showed a greater than 20% increase when compared with samples from undisturbed parts of the coup (Figure 18). Scaling for proportion of the coupe surveyed, this corresponds to about 12% of the coupe. As with aeration porosity, it is probably more relevant to consider absolute values of penetration resistance than a percent change. It is difficult to select a single critical value of penetration resistance, since the relationship between root growth and soil strength is continuous. This is also the case for aeration porosity, although 10% is commonly adopted as a critical value below which a lack of oxygen prevents normal root function. A similar value for penetration resistance, above which root extension is generally regarded as being impeded, would be around

2.5 MPa. There were only ten values in the 0-300 mm depth that exceeded 2.5 MPa. It is apparent that only a relatively small proportion of the coup exceeded the standards for soil

damage suggested by the proposed interim criteria. These were approximately equal to the proportion of the coup affected by access tracks, log dumps and major snig tracks.

0-100mm

40 samples

0-300mm

depth an h

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20 21 samples

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40 0-300mm

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depth ( 30 ty

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Figure 18. Box plots showing distribution of percent change in bulk density for 0-100 mm and 0-300 mm depths, mean air porosity, and percent change in penetration resistance.