Factors affecting stand structure in forests - are there climatic and topographic determinants?

Multi-aged stands are not a common structural type of mountain-ash forest i n the Central Highlands of Victoria, southeastern Australia, but they are n evertheless important, particularly as habitat for wildlife. Extensive fiel d data and information generated from spatial models of climate, topography and radiation regimes were examined to identify factors which related to t he occurrence of stands of multi-aged mountain-ash forest. The probability of occurrence of multi-aged stands increased significantly (p < 0.001) with the age of the forest. There also was evidence that multi-aged stands were more likely to occur on steeper slopes (p = 0.01). When actual on-ground f ield measurements were ignored and program-generated climate, topography an d radiation data only were modeled, a decrease in the shortwave radiation r atio (a measure of the estimated solar radiation budget) was associated wit h a significantly increased probability of occurrence (p = 0.03) of multi-a ged stands. Our analyses indicated there are particular parts of mountain-a sh forest landscapes where complex multi-aged stand structures are more lik ely to develop. This has implications for the methods used to harvest mount ain-ash forests for timber and pulpwood, particularly the need for increase d retention of structural components of stands targeted for logging. (C) 19 99 Elsevier Science B.V. All rights reserved.