Hollow Trees in the Coastal Forests of North East NSW Abundance and Spatial Distribution: Now and a Model for the Future

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1 Hollow Trees in the Coastal Forests of North East NSW Abundance and Spatial Distribution: Now and a Model for the Future Justin Williams Regional Ecologist SFNSW - Mid North Coast Region

2 Hollow Tree Summary Many species require tree hollows for nest/den sites which may take years to develop Studies on hollow development and numbers required on few eucalypt species and mostly relate to clearfall silviculture Data for North Coast NSW predict 3-13 hollow trees/ha required before other factors such as food and predators limit wildlife populations

3 Recent Regional Forest Agreement Increased Area of Reserves - 54% of public land reserved Management conditions on production forests effect the number and distribution of hollows Baseline number of hollows trees to be retained: 5/ha

4 Identifying Current Distribution and Abundance of Hollow Trees Mapped strata developed - broad forest type & growth stage Forest inventory plots across strata Identify average number of hollow trees per strata Map distribution of hollow trees using strata averages

5 14 Current Abundance of Hollow Trees Strata Regrowth Blackbutt Regrowth Moist Hardwood Regrowth Mixed Hardwood Regrowth Spotted Gum/Blackbutt Regrowth Dry Sclerophyll Mixed Age Blackbutt Rainforest with Emergent Euc s Area (%) Avg No/Ha Strata 4 7 Mixed Age Moist Hardwood 3 10 Mixed Age Mixed Hardwood 4 7 Mixed Age Spotted Gum/Blackbutt 3 3 Mixed Age Dry Sclerophyll Area (%) Avg No/H a Old Regrowth Blackbutt Old Regrowth 4 13 Moist Hardwood 8 11 Average 10

6 Predicting Future Abundance of Hollow Trees Matrix of likelihood of hollow trees: tree species and size class Grow stands with yield simulation tool used to predict future timber volumes Apply matrix to tree lists produced from yield simulator to predict likelihood of future tree containing hollows

7 Example: Proportions of trees with hollows for five species in the 40-60, 60-80, & 100+ cm diameter size classes 100% Proportion of Trees With Hollows 80% 60% 40% 20% GYG % GYG WMY TWD SBG BBT Species

8 Model of number of trees with hollows today and in 100 years in harvested and not harvested areas Strata Today Harvested Not Harvested Young Regrowth Blackbutt Old Regrowth Blackbutt Mixed Age Mixed Hardwood Mixed Age Dry Sclerophyll Forest Weighted Average All 13 strata

9 Model of the number of trees/ha with hollows for a 200 year period under three silvicultural scenarios Number/ha Actual STS Heavy No Harvest Year

10 Average number of hollow trees/ha across landscape including harvested and reserved areas Y2000 Y2025 Y2050 Y2100 T2200

11 Modelling Future Distribution of Hollow Trees Produce grid of strata and management intent across landscape Reference grid with future hollow matrix to produce grid with number of hollows Spatial analysis to predict distribution of hollow trees across landscape

12 Example Forest Landscape Bellangry State Forest (2000 ha).. Rainforest.. Harvesting Exclusions I:=] New National Park ~ State Forest

13 ~ 3-6 Hollow Trees/ha.. Rainforest ~ 6-10 Hollow Trees/ha.. Harvesting Exe Example Forest Landscape Number of Hollow Trees- Present Hollow Trees/ha c=j State Forest Hollow Trees/ha ~ Hollow Trees/ha c=j New National P

14 Example Forest Landscape ~ 3-6 Hollow Trees/ha - Rainforest ~ 6-1 O Hollow Trees/ha Number of Hollow Trees-100 years Time - Harvesting Exclusion: ~ Hollow Trees/ha ~ New National Park Normal Silviculture Hollow Trees/ha ~ State Forest ~,~~ ~ Hollow Trees/ha

15 Summary of Results Produced useful base-line data on the size-classes where species develop hollows and produced a realistic model to predict the future abundance of hollows The model predicts that the RFA outcome will result in significant increase in number of hollow trees over the long-term and maintain existing numbers in the shortterm

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17 Example Forest Landscape 6,000 ha Average Distance (m) to Mapped Exclusion Area Normal Silviculture Avg Distance to Exclusion 70 m Median Distance 50 m ~~I ~I _ I ~-I I ~I 50 _ 70 I I

18 Model of Number of Hollow Trees/ha - Actual Silviculture for 3 habitat strata No/ha DBBT_E MBBT_C TDE_ABC Mean Year

19 Proportion of Trees with Hollows in the cm size class for 8 common species in four site height categories 100% 80% 60% 40% 20% < % W MY T WD SPG SBG G YG B LW BBX BBT