A study of the effect of logging on the understorey light environment in riparian buffer strips in a south-east Australian forest

Abstract

Commercial timber harvesting is carried out across much of the wet sclerophyll forests of south-east Australia. Undisturbed forest buffers are retained along streamlines to maintain aquatic and riparian habitat values, but the consequences of this strategy for many habitat values are not well understood. Light penetration plays a major role in the ecology of the riparian forest and protection of the light environment is seen as an important function of buffers that aim to protect riparian habitat values. We used hemispherical canopy photographs, taken at 1, 3.4 and 6.8 m at 10 m intervals along 100 m transects to describe the spatial variation in the forest understorey light environment along a gradient from streamside vegetation to the upslope eucalypt-dominated forest. Post-logging photographs taken at the same points were used to model the light penetration edge effects following clearfelling. We also examined the relationship between light penetration and physical and vegetation characteristics. The natural understorey light environment was influenced by proximity to the streamline to about 50 m upslope, light penetration increasing at a relative rate of about 9% for every 10 m from the streamline. Light penetration was also influenced by topography and vegetation characteristics. There was a high level of spatial heterogeneity, but the light environment was relatively unchanged over a 9-month period, indicating temporal stability. Creation of a sharp edge by logging of the upslope forest resulted in major changes in light penetration. The zone close to the edge experienced increases in light penetration in excess of 100%, with reducing but detectable changes penetrating to 70–100 m.