Variable retention harvesting and canopy species dominance and regeneration in Nothofagus-Ceratopetalum cool temperate rainforest

Transcription

1 Variable retention harvesting and canopy species dominance and regeneration in Nothofagus- cool temperate rainforest Ross Peacock NSW Department of Environment & Climate Change c/o Department of Biological Sciences Macquarie University, Australia 1

2 Study background experiment commenced in 196 as a result of silvicultural difficulties being experienced in the 195 s with rainforest in New South Wales utilisation of the canopy dominant Nothofagus (Beech) was poor the sub-dominant tree were preferred 5% canopy retention harvesting adopted largely based on experience in SE Asia damage and poor health of retained trees was a challenge elsewhere in NSW rainforest silviculture adopted selection methods or stands were converted to plantation or Eucalyptus forest 2

3 Cool Temperate Rainforest in northern NSW confined to higher elevations > 1 m with frequent mists and low temperatures Rainfall peaks in summer, although temperatures are relatively cool with occasional frosts and snow fall. Currently managed for nature conservation, with canopy dieback being a challenge for park managers. Timber production ceased in 198 s. 3

4 n Rd Crow 4 Hastings Forest Way Hasting s For est Way Cocker a wombe eba Rd

5 simple structure and dominance pattern tree basal areas high at 57-8m 2 /ha Nothofagus dominates with as a sub-dominant canopy for stems >1cm dbh initial basal area (m 2 /ha) initial density/ha Mean stem diameter (cm) Nothofagus moorei apetalum Doryphora sassafras Tristaniopsis collina sum

6 apetalum (Coachwood) preferred species for its wood properties slow growth ( cm/year) post harvesting seed availability limited year to year by mast behaviour high density of shade tolerant seedlings and coppice growth but growth under residual canopy is slow regeneration enrichment trials abandoned thin bark leads to damage or death following low intensity fires 6

7 apetalum 7

8 Nothofagus moorei (Antarctic Beech) utilisation by sawmills problematic seedlings favour canopy gaps, snig tracks, fallen logs, possibly requiring mycorrhizal interaction seed production is erratic, high viability, short lived faster growth (.1 to 1.3 cm, average.4 cm/year on 9 cm dbh tree) basal or stump coppice follows low intensity fires or harvesting 8

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10 plot design harvesting tree marking plot measurement per treatment plot measurement Four un-replicated treatments (, 25, 5 and 75% basal area removal) each of 1 ha Chainsaw, dozer skidding and winching 1961 Single tree selection harvesting based on 7% of removed trees to be of merchantable quality, 3% nonmerchantable one 4 x 4m plot per treatment, all trees > 1 cm Response variables: species, height, dbh, dominance, mode, damage, health 34 2 x 2 m sub-plots plot per treatment Response variables: floristics, tree height, seedling density, regeneration mode measured in 1962, 1964, 1968, 1972, 1976, 198, 1983, 1985, 1991, 26 Hypothesis: manipulating harvesting intensity will lead to different proportions of Nothofagus and in the regenerating stand 1

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12 Treatment 25% basal area removed 5% basal area removed 75% basal area removed initial 196 BA m 2 /ha log volume removed m 3 /ha nil BA m 2 /ha % BA removed ~nil % soil disturbance nil 4-5% % 12

13 25% 5% 75% 13

14 1962 Stems >1cm 25% 5% 75% % removed Nothofagus stem density/ha stem density/ha diameter (cm) Nothofagus basal area/ha % removed % removed basal area/ha Stems >1cm Nothofagus stem density/ha stem density/ha % % % % removed diameter (cm) Nothofagus basal area/ha basal area/ha % removed % removed

15 % % coppice seedlings Nothofagus coppice Nothofagus seedlings 5% 1962 seedlings/ha % % coppice seedlings Nothofagus coppice Nothofagus seedlings 5% 26 seedlings/ha

16 % %.5.5 coppice seedlings - - Nothofagus coppice Nothofagus seedlings 5% 1962 Mean seedling height (m) % % coppice seedlings Nothofagus coppice Nothofagus seedlings 5% 26 Mean seedling height (m)

17 Damage to the residual stand from harvesting and wind throw can be significant % 5% 75% Mortality (% of trees) Nothofagus

18 Tree growth (>1 cm dbh) for those surviving since 196 Treatment 25% basal area removed 5% basal area removed 75% basal area removed Nothofagus pai (cm) pai (cm)

19 can increasing harvesting intensity lead to different proportions of Nothofagus and in the regenerating stand? Tree density and basal area (> 1 cm) Seedling recruitment Seedling growth Mortality Tree growth Overall response to increasing canopy removal apetalum relative decline in BA and stem density highly variable response however seedlings persist in understorey slower than coppice stems more susceptible to wind throw increases with intensity of canopy removal disadvantaged Nothofagus moorei increase in BA and stem density highly variable response coppice associated with more intensive canopy removal initially more rapid in less intensive treatments, then more rapid in intensive treatments more susceptible to canopy dieback two to three times faster advantaged 19