Analysis and review of regeneration records (1987-1995) from the HEMS forest in East Gippsland.  J. D. Delbridge.  December 1998.  28pp. (unpubl.)

SUMMARY

In recent years, silviculture of the High Elevation Mixed Species (HEMS) forest type has received significant attention due to concerns with achieving satisfactory regeneration. As a result, the Eastern Research and Development Action Group (ERDAG) identified a series of principles which should be followed in regenerating HEMS coupes. The Working Group predicted that variations from these principles would be implicated in the failure of many of the HEMS failed coupes which had been reported at the time. As such, the purpose of this report was to review the results of HEMS regeneration operations and to determine factors influencing regeneration outcomes and evaluate the effect of departing from ERDAG principles.

A study was conducted of the records for HEMS coupes harvested in East Gippsland from 1987 onwards. This included coupes from Cann River, Bendoc, Bairnsdale, Orbost, Nowa Nowa and Swifts Creek Districts. Three case study Districts, Cann River, Bendoc and Nowa Nowa were selected for further collection of additional coupe data.

Data analysed included elevation, coupe area, duration of harvest, curing time, rate of harvesting, time from site preparation to sowing, slope and yield. Regression analysis and general linear models were employed to identify trends in the data and to reveal the significance of factors.

The results show an extremely high level of variation within each category for all factors analysed. Since the development of the 1993 ERDAG regeneration guidelines, variation from these principles have continued to occur, although to a lesser extent, and even when the principles are followed regeneration outcomes have had variable success. The significance of year of harvest (regeneration) indicates that seasonal growing conditions make a major contribution to regeneration outcomes, potentially overriding negative ecological or physical site characteristics or management variables.

Despite the extremely high level of variation observed, a number of factors were found to influence the outcome of regeneration operations including year of harvest, silvicultural system, elevation, aspect, and coupe area for some Districts. Weak trends of increasing regeneration success were associated with higher yielding coupes and higher intensity burning, whilst carrying-over of coupes was implicated in failed regeneration.

It was concluded that whilst it is plausible to suggest that a single factor may be of critical importance to regeneration success at a particular site in a given year, the same factor may not be significant at another site or at a different time. Perhaps it is more appropriate to suggest that regeneration is influenced by all the factors, both on an independent and interactive basis, however, the significance and the ranking of these factors will change from site to site and year to year.

Recommendations are made on the implications for management and research.