Hollow Trees in the Coastal Forests of North East NSW - Abundance - - PowerPoint PPT Presentation

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

Hollow Tree Summary

• Many species require tree hollows for

nest/den sites which may take 150-250 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

• Recent Regional Forest

Agreement

• Increased Area of

Reserves - 54% of public land reserved

• Management conditions
• n production forests

effect the number and distribution of hollows

• Baseline number of

hollows trees to be retained: 5/ha

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

Current Abundance of Hollow Trees

Strata Area (%) Avg No/Ha Strata Area (%) Avg No/H a Regrowth Blackbutt 4 7 Mixed Age Moist Hardwood 17 14 Regrowth Moist Hardwood 3 10 Mixed Age Mixed Hardwood 24 13 Regrowth Mixed Hardwood 4 7 Mixed Age Spotted Gum/Blackbutt 9 6 Regrowth Spotted Gum/Blackbutt 3 3 Mixed Age Dry Sclerophyll 10 10 Regrowth Dry Sclerophyll 1 15 Old Regrowth Blackbutt 9 5 Mixed Age Blackbutt 5 9 Old Regrowth Moist Hardwood 4 13 Rainforest with Emergent Euc’s 8 11 Average 10

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

GYG

Example: Proportions of trees with hollows for five species in the 40-60, 60-80, 80-100 & 100+ cm diameter size classes

0% 20% 40% 60% 80% 100% GYG WMY TWD SBG BBT

Species Proportion of Trees With Hollows

60-80 80-100 100+

40-60

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 7 12 22 Old Regrowth Blackbutt 5 10 27 Mixed Age Mixed Hardwood 13 14 27 Mixed Age Dry Sclerophyll Forest 10 13 20 Weighted Average All 13 strata 10 12 24

Model of the number of trees/ha with hollows for a 200 year period under three silvicultural scenarios

5 10 15 20 25 30 2000 2025 2050 2100 2200 Year Number/ha

Actual STS Heavy No Harvest

Average number of hollow trees/ha across landscape including harvested and reserved areas

5 10 15 20 25 Y2000 Y2025 Y2050 Y2100 T2200

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

.. Rainforest .. Harvesting Exclusions Example Forest Landscape -

I:=] New National Park

~

State Forest

Bellangry State Forest (2000 ha)

~

3-6 Hollow Trees/ha

.. Rainforest

~

6 - 10 Hollow Trees/ha

.. Harvesting Exe

Example Forest Landscape

~

11 - 15 Hollow Trees/ha

c=J New National P

Number of Hollow Trees- Present

.. 16 -22 Hollow Trees/ha

c=J State Forest

• 23 - 35 Hollow Trees/ha

Example Forest Landscape ~

3-6 Hollow Trees/ha

• Rainforest

~

6 - 1 O Hollow Trees/ha

Number of Hollow Trees-100 years Time

• Harvesting Exclusion:

~

11 - 15 Hollow Trees/ha

~

New National Park

Normal Silviculture

.. 16 - 22 Hollow Trees/ha

~

State Forest

• 23 - 35 Hollow Trees/ha
• ~,~-~-

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 short- term

a

• a

Example Forest Landscape 6,000 ha Average Distance (m) to Mapped Exclusion Area Normal Silviculture

~I

12 - 24 ~I _ I 100 - 150

~-

I

150- 175 ._~

50 _ 70 I

I 175- 3808

Avg Distance to Exclusion 70 m Median Distance 50 m

Model of Number of Hollow Trees/ha - Actual Silviculture for 3 habitat strata

3 6 9 12 15 18 2000 2025 2050 2100 2200 Year No/ha DBBT_E MBBT_C TDE_ABC Mean

BBT BBX B G LW YG SBG SPG T W WD MY

Proportion of Trees with Hollows in the 80-100 cm size class for 8 common species in four site height categories

0% 20% 40% 60% 80% 100% <27 28-33 34-40 40+