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Coffs Harbour, Australia

Jamshidi R.,University of Sydney | Dragovich D.,University of Sydney | Webb A.A.,Forestry Corporation of NSW | Webb A.A.,University of New England of Australia
Forest Ecology and Management | Year: 2013

Conservation of soil and water resources is one of the key criteria underpinning sustainable forest management. While soil and water resources are important determinants of forest productivity, without appropriate assessment of soil erosion risk and the application of best management practices (BMPs), some forest management activities can adversely affect hillslope erosion rates with detrimental consequences for aquatic environments and downstream water users. In the multiple-use native eucalypt forests of New South Wales (NSW), Australia, hazard matrix tables are currently used to identify soil erosion risk based upon rainfall erosivity, soil regolith stability and slope classes at the compartment scale prior to undertaking forestry activities. Resultant "inherent hazard levels" (IHLs) direct the BMPs to be used, such as riparian buffer widths, during harvesting and roading operations. The IHL model, being an ordinal classification system, only provides a relative indication of erosion potential without any quantitative estimate of possible post-harvest erosion rates. To potentially better identify erosion risk and quantify likely soil erosion under a range of forest management and climatic scenarios at the hillslope and/or catchment scale, in this paper we utilised an alternative approach by modelling soil erosion using the empirically-derived Revised Universal Soil Loss Equation in combination with a GIS-based spatially distributed raster analysis. In four case study catchments in Kangaroo River State forest, two of which were subjected to single-tree selection harvesting operations, mean annual changes in soil loss were estimated at a grid cell level. Potential differences in soil loss estimates were assessed before, during and after selective logging. Vegetation cover and soil samples were recorded in a 500 × 1000 m rectangular network laid out across the catchments. Slope gradient was found to contribute substantially to the spatial variability of soil loss estimation across the catchments. However, between-year differences demonstrate that the highest estimated annual rates of soil loss occurred on steep hillslopes when high levels of rainfall were recorded, while the values on those same areas remained considerably lower during low rainfall periods. The major effect of the rainfall component in generating soil erosion overshadows the modest impacts of selective logging operations. © 2013 Elsevier B.V. Source

Jamshidi R.,University of Sydney | Dragovich D.,University of Sydney | Webb A.A.,Forestry Corporation of NSW | Webb A.A.,University of New England of Australia
Hydrological Processes | Year: 2014

The intensity of soil loss and sediment delivery, representing hydrologic and geomorphic processes within a catchment, accelerates with rapid changes in land cover and rainfall events. An underlying component of sustainable management of water resources is an understanding of spatial and temporal variability and the adverse influences of regional parameters involved in generating sediment following widespread changes in land cover. A calibrated algorithm of soil loss coupled with a sediment delivery ratio (SDR) was applied in raster data layers to improve the capability of a combined model to estimate annual variability in sediment yields related to changes in vegetation cover identified by analyses of SPOT imagery. Four catchments in Kangaroo River State forest were assessed for annual changes in sediment yields. Two catchments were selectively logged in 2007, while the two other sites remained undisturbed. Results of SDR estimates indicated that only a small proportion of total eroded sediment from hillslopes is transported to catchment outlets. Larger SDR values were estimated in regions close to catchment outlets, and the SDR reduced sharply on hillslopes further than 200-300 m from these areas. Estimated sediment yield increased by up to 30% two years after land cover change (logging) in 2009 when more storm events were recorded, despite the moderate density of vegetation cover in 2009 having almost recovered to its initial pre-logging (2005) condition. Rainfall had the most significant influence on streamflow and sediment delivery in all catchments, with steeply sloping areas contributing large amounts of sediment during moderate and high rainfall years in 2007 and 2009. It is concluded that the current scenario of single-tree selection logging utilized in the study area is an acceptable and environmentally sound land management strategy for preservation of soil and water resources. © 2013 John Wiley & Sons, Ltd. Source

Collins L.,University of Wollongong | Collins L.,University of Western Sydney | Penman T.,University of Wollongong | Ximenes F.A.,Australian Department of Primary Industries and Fisheries | And 3 more authors.
Forests | Year: 2014

The management of forest ecosystems to increase carbon storage is a global concern. Fire frequency has the potential to shift considerably in the future. These shifts may alter demographic processes and growth of tree species, and consequently carbon storage in forests. Examination of the sensitivity of forest carbon to the potential upper and lower extremes of fire frequency will provide crucial insight into the magnitude of possible change in carbon stocks associated with shifts in fire frequency. This study examines how tree biomass and demography of a eucalypt forest regenerating after harvest is affected by two experimentally manipulated extremes in fire frequency (i.e., ~3 year fire intervals vs. unburnt) sustained over a 23 year period. The rate of post-harvest biomass recovery of overstorey tree species, which constituted ~90% of total living tree biomass, was lower within frequently burnt plots than unburnt plots, resulting in approximately 20% lower biomass in frequently burnt plots by the end of the study. Significant differences in carbon biomass between the two extremes in frequency were only evident after >15-20 years of sustained treatment. Reduced growth rates and survivorship of smaller trees on the frequently burnt plots compared to unburnt plots appeared to be driving these patterns. The biomass of understorey trees, which constituted ~10% of total living tree biomass, was not affected by frequent burning. These findings suggest that future shifts toward more frequent fire will potentially result in considerable reductions in carbon sequestration across temperate forest ecosystems in Australia. © 2014 by the authors. Source

Law B.,Australian Department of Primary Industries and Fisheries | Gonsalves L.,Australian Department of Primary Industries and Fisheries | Tap P.,Forestry Corporation of NSW | Penman T.,University of Melbourne | Chidel M.,Australian Department of Primary Industries and Fisheries
Austral Ecology | Year: 2015

Landscape-scale monitoring is a key approach for assessing changes in indicators. However, great care needs to be taken to collect rigorous data and avoid wasting resources in long-term programmes. Insect-eating bats are diverse, functionally important and are often proposed as indicator species of environmental health. We used acoustic (ultrasonic) data from pilot bat surveys undertaken in forests and woodlands to optimize sampling effort to produce precise estimates of bat activity and occupancy. We also carried out simulations to evaluate the statistical power of different sampling designs to detect changes in activity and occupancy levels of individual bat species. There was little gain in precision for estimates of bat activity by sampling beyond five to six detector nights. To ensure spatial heterogeneity was sampled around a monitoring point, three detectors for two nights or two detectors for three nights would be required. This level of sampling was also sufficient to be 90% certain of recording occupancy for 11 of 12 taxa. Power simulations revealed that a sampling design using two detectors per monitoring point for two nights could detect a 30% decline within 10 years with 90% power for all species, except the white-striped free tail bat (Tadarida australis), using either changes in activity levels or occupancy. However, fewer years were required when using occupancy. Setting detectors either on-flyways or off-flyways contributed only minor differences to the time taken to reach 90% power for both occupancy and activity levels, though sampling both locations has major implications for interpreting trends in bats. We suggest that bat activity levels are more sensitive for detecting change than occupancy because one pass or 1000 passes can be recorded per night by an acoustic detector, and this is not differentiated by occupancy. Bats can be monitored cost-effectively and should be included in monitoring programmes. © 2015 Ecological Society of Australia. Source

Webb A.A.,Forestry Corporation of NSW | Webb A.A.,University of New England of Australia | Jarrett B.W.,Forestry Corporation of NSW
Forest Ecology and Management | Year: 2013

Eucalypts are commonly planted hardwoods worldwide and Eucalyptus dominated forests naturally grow in the headwaters of many Australian water supply catchments. The hydrological effects of disturbances have been extensively reported for one species, E. regnans (Mountain Ash). The typical response to disturbance is unusual in that following an initial increase, with heavy seed dispersal and rapid regeneration, streamflow from these forests is greatly reduced. In New South Wales (NSW), native forests are dominated by different Eucalyptus species that typically grow in mixed-species and mixed-age stands that regenerate less vigorously. In this study the long term streamflow records from the six Yambulla catchments in southeastern NSW were analysed to assess the relative effects of wildfires, integrated logging operations and subsequent mixed species eucalypt forest regeneration on catchment hydrology.In all five treated catchments an increase in total streamflow, baseflow and stormflow was detected following the 1979 wildfire and/or integrated logging activities that occurred at various intervals. A subsequent reduction of streamflow to below that of a mature stand was not detected in three of the catchments but was detected in the two that had been subjected to integrated logging followed by a wildfire, and a wildfire followed by salvage logging, respectively. The reduction, however, was minor and short-lived in each case meaning that overall there was a cumulative increase in streamflow in the post-disturbance period. These results contribute to a growing body of evidence indicating that catchment-scale hydrological responses to disturbance of mixed species eucalypt forests do not follow the unusual response often reported in wet Mountain Ash forests. This has important implications for the modelling and management of mixed species eucalypt hydrology. © 2013 Elsevier B.V. Source

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