Evaluation of different methods of post-harvest indicator assessment to devise cost-effective procedures for monitoring

1.4 Evaluation of different methods of post-harvest indicator assessment to devise cost-effective procedures for monitoring

Survey Methods The thorough investigation of alternative survey methods presented in Part II, Study C, suggested

that where transect methods are used to quantify logging disturbance, the transect-quadrat type approach is optimum. Whilst the greatest criticism of this technique is that it is not fully random, the distribution of logging tracks is also non-random, and hence a semi-targeted orientation of transects can be justified. In addition, this counter-randomisation strategy would appear to be particularly suited to obtaining an acceptably reliable estimate of the various disturbance classes without needing to resort to a particularly high intensity of sampling. On the other hand, its drawback, as suggested by the logging study of Part I, is that it will still involve a high level of resources to implement on large coupes such as that encountered in compartment 551.

Alternative to Measuring Soil Physical Properties The only alternative to a physical property based indicator is one that adopts disturbance classes as

a measuring basis. Such an approach would be dependent upon attaching a certain “sustainability implication” to particular disturbance categories, primarily because that would lead to changes in the soil physical environment such as to have a detrimental effect on tree growth.

The evidence in this study suggests that unrehabilitated access tracks and major/primary snig track operational categories could readily be adopted as indicators of soil physical change that would have a direct influence on long-term sustainability. The evidence is similarly strong for class S3 disturbance. (In general, primary snig tracks predominantly consist of S3 disturbance, but S3 can occur elsewhere.) It would probably also be readily agreed that minor or tertiary snig tracks generally do not experience detrimental change in soil physical properties. They are primarily composed of S1 (litter disturbed) and S2 (topsoil disturbed) disturbance, and the regeneration surveys provide no evidence of a loss of growth on these classes. However, this leaves some uncertainty over the secondary (moderate) snig tracks. Part of the reason for this is perhaps due to the composition of disturbance classes on this operational category, i.e. the disturbance tends to be composed of mostly S2, but also significant amounts of S3, level disturbance. There is also a suggestion in the comparison of the NSW and Victorian data, that soil type may be an important determinant of whether S2/secondary snig track type disturbance is detrimental to the subsequent regenerated stand. The hypothesis developed through this study is that where fertility is generally high, and water is not limiting, moderate levels of disturbance are likely to have some detrimental effect on the growth rates of subsequent regeneration and that the reverse applies for low fertility sites.

Thus, a pragmatic indicator might be “the area and percent of the net logged area occupied by disturbance or operational classes known to be associated with reduced tree growth” . This could

be framed to vary depending on soil type, and based on current knowledge for southeastern Australia, we might suggest:

For operations on soils with surface (0-20 cm) texture grade sandy clay loam or finer, and known nutrient defieincies: all areas of unrehabilitated log landings, log truck access tracks, primary snig tracks, secondary snig tracks and additional areas of S3 disturbance.

For operations on soils with surface (0-20 cm) texture grade coarser than sandy clay loam and no known nutrient deficiencies: all areas of unrehabilitated log landings, log truck access tracks, primary snig tracks, and any additional areas of S3 level disturbance.

If this level of data collection were carried out for a randomly selected 10% to 20% of logging operations, it would be not be a prohibitive cost to forest managers. It would also represent a valuable statistically sound indication of the sustainability of management practices for a given forest management region and provide a basis on which managers could assess planning and management. If soil moisture condition and soil type were systematically recorded together with these data, the data could be re-interpreted as necessary if better understandings of relationships between disturbance category, soil type and soil moisture condition were developed through continued applied research.

Actual data recording could be cost effectively performed with either transect surveys or GPS mapping of the snig track and disturbance network. The latter would give the quickest and probably most cost-effective method. It would also be more accurate for the distribution of operational categories, but would be less effective at identifying S3 disturbance that was not coincident with extraction tracks.

One important advantage of the mapping approach to indicator reporting is that it would generate a highly accurate digital data of the extraction tracks and log landings. This could be stored in GIS and used to advantage by forest managers for fire management and future harvesting operations. Forest management codes or regulations could even be framed around this process and require, for example, that harvesting operations utilise previous access tracks, log landings and primary snig tracks where their location is known. The course of this study clearly demonstrated the potential that exists for greater application of GPS technology to forest management, whether for simple mapping or use in machine tracking to provide valuable data that allow detailed analysis of the logging process and its effects.

We believe that these studies have made a significant improvement to our capacity to develop workable methods for cost-effective monitoring of sustainability for Indicator 4.1e. We have identified an optimum sampling strategy that is certainly appropriate for smaller coupes (<30 ha), with high timber yields, but perhaps less so for larger less intensively logged ones. We have also identified a rational basis for using cost-effective surrogate techniques for monitoring and reporting sustainability criteria for intensive ground-based logging of native forests. There is no doubt that the proposed surrogate approach will possess some uncertainties. However, we believe that to adopt this approach, and continue to underpin it with additional research data, especially on long- term tree growth and temporal change in soil properties, will be more cost-effective than adopting a soil property based approach.