Warra Site Beetle Survey Data, Southern Forests Experimental Forest Landscape, 2010-2011 

This record is on the beetle survey conducted at the Warra Site, as part of the Southern Forests Experimental Forest Landscape (SFEFL). The data set contains information on beetle sample and species identification details, the number of individual specimens sampled, the age class of individuals and any relevant comments for each observation in the data set. 

We at TERN acknowledge the Traditional Owners and Custodians throughout Australia, New Zealand and all nations. We honour their profound connections to land, water, biodiversity and culture and pay our respects to their Elders past, present and emerging. 

The data set was collected as part of a broader study examining the responses of bird, plant and beetle species to the intensity of disturbance in the landscape surrounding plots of either mature tall, wet eucalypt forest or of 25–50 year-old silvicultural regeneration following clearfell harvesting. The study tested the null hypotheses that species persisting in patches of mature forest or re-colonising patches of silvicultural regeneration would be insensitive to the intensity of disturbance in the surrounding landscape. The study was done in 2010–2011 in the Southern Forests Experimental Forest Landscape (SFEFL) a 32 x 35 area anchored on the Warra Long-Term Ecological Research site and extending eastwards to the estuary of the Huon River. 

The surveys of the three taxonomic groups were done in fifty-six, 50x50 m plots – 28 each in mature eucalypt forest and silvicultural regeneration. Those plots were located to sample the measured range of average disturbance intensity (based on the mix of vegetation classes) at three scales, 0.5, 1 and 2 km – in the circular landscapes surrounding the plots. The beetle data set was based on window intercept trap sampling to collect beetles at each 50 x 50 m plot-corner done on over a six-week period in March – April 2010.

Methods used:

• 1) Calculation of landscape disturbance intensity: A vegetation map of the SFEFL representing the 2009 distribution of nine broad vegetation classes (asn_wrra_SFEFL_vegetation_class.csv) was produced at 1:20,000 scale from forest-types interpreted from aerial photography (Stone, 1998, Tasforests, 10: 15-32) acquired in the 2000s (Forestry Tasmania, Forest Class 2005 mapping), and converted to 50 m pixel raster format using the open-source GIS software SAGA©. Each vegetation class was assigned a disturbance rating between 1 (least disturbed) for rainforest and 10 (most disturbed) for agricultural land (asn_wrra_SFEFL_vegetation_class.csv), and each pixel was assigned the disturbance rating corresponding to its vegetation class. Using a moving-window algorithm, the Landscape Disturbance Index (LDI) for each pixel was then calculated by averaging the disturbance rating of all pixels within a given radius of that pixel. Separate LDIs were calculated for radii of 500 m, 1 km and 2 km, to give separate LDI values for each pixel at these three landscape-scales. All LDI values were rounded down to the nearest integer and the raster maps of integer LDIs at each of the three spatial scales were overlaid to identify pixels with the same integer LDI at each of the three spatial scales to produce a “three-scale-consistent LDI” map of the SFEFL.
• 2)Selection of sample plots: The three-scale consistent LDI map of the SFEFL was overlain with the mapped extent of two forest age-classes: (i) mature eucalypt forest > 110 years old and never harvested; and (ii) older (25–50 years-old) wet eucalypt forest that had been silviculturally regenerated after clearfell harvesting. Patches of these age-classes coinciding with pixels that were three-scale consistent for LDI class were identified. All locations of scale-consistent patches of mature eucalypt forest and older silvicultural regeneration were prioritised for field validation according to the following criteria: i. Low altitude (below 600 m); ii. Forest dominated by E. obliqua, E. regnans, or a mixture of these species; iii. At least 75 m from a road, vehicle track, or edge of a strongly contrasting vegetation type; and iv. Forest patch of an age-class was at least 150 m wide at a point where a plot could be located. The final experimental design comprised seven replicate 50 x 50 m square plots of mature eucalypt forest (MAT plots) at each of four LDI classes (4–7), and seven replicate plots of older silvicultural regeneration (SILV plots) at each of four LDI classes (5–8). Mature forest within highly disturbed areas with LDI class 8 was rare, as was older silvicultural regeneration within relatively undisturbed areas with LDI class 4, so these combinations were not sampled.
• 3) Beetle surveys: Single triangular-window intercept traps, each with a rain diverter mounted in the funnel above the collection bottle, were installed at each corner of each plot in early summer 2009–10. The position of each trap was adjusted to provide as open a flight-line as possible for insects travelling at trap height (about 0.5–1.0 m above ground-level). Collection bottles were charged with 100 ml of 95% ethanol and left for a 6-week period in March–April 2010. At the end of this period, collection bottles were removed, topped up with 95% ethanol, and stored in a cool room at 3°C until specimen identification and pinning. The data from the four traps at each plot were aggregated to give the number of specimens of each taxon collected on each plot. All beetles collected have been pinned and incorporated into the Tasmanian Forest Insect Collection housed at the Tasmanian Museum and Art Gallery.
• 4) Study Extent Description: The three-scale consistent LDI map was overlain with the mapped extent of two forest age-classes: (i) mature eucalypt forest > 110 years old and never harvested; and (ii) older (25–50 years-old) wet eucalypt forest that had been silviculturally regenerated after clearfell harvesting. Patches of these age-classes coinciding with pixels that were three-scale consistent for LDI class were identified. All locations of scale-consistent patches of mature eucalypt forest and older silvicultural regeneration were prioritised for field validation according to the following criteria: i. Low altitude (below 600 m); ii. Forest dominated by E. obliqua, E. regnans, or a mixture of these species; iii. At least 75 m from a road, vehicle track, or edge of a strongly contrasting vegetation type; and iv. Forest patch of an age-class was at least 150 m wide at a point where a plot could be located. The final experimental design comprised seven replicate 50 x 50 m square plots of mature eucalypt forest (MAT plots) at each of four LDI classes (4–7), and seven replicate plots of older silvicultural regeneration (SILV plots) at each of four LDI classes (5–8). Mature forest within highly disturbed areas with LDI class 8 was rare, as was older silvicultural regeneration within relatively undisturbed areas with LDI class 4, so these combinations were not sampled.