1. Jing Hu University of Queensland
Dynamics of a Logged Tropical Forest-Following Different intensity Silvicultural Treatments over 48 years (Mt Baldy, Atherton)
Jing Hu
University of Queensland

2. Why set up this long-term experiment in 1960s?
North Queensland rainforests managed for timber production prior to 1988
No logging, no silvicultural treatment (removing non-commercial species)
Set up in 1967 to look at effects of different intensity silvicultural treatments on commercial timber volume.

3. Today’s situation: balance between timber provision and maintaining ecosystem services
Did silvicultural treatments promote commercial timber volume, and which intensity perform best?
How would above-ground tree biomass, species diversity and composition recover following different intensity treatments over 48 years?

4. Study site
Mount Baldy, Atherton, north Queensland

5. Inventory years 1967 Mar,1969 Aug, 1969 1973 1981 1989 1997 2015
1968 (logging)
Treatment

6. ≥ 10cm DBH;
DBH, mortality and recruitment; Species ID

7. Did silvicultural treatments promote commercial timber volume, and which intensity perform best?

8. Medium intensity treatment performed best in increasing commercial timber volume.
Indication: treatment effects may still work for the next several decades.
Low intensity
Logging only
High intensity
Fig. 1 Harvestable timber volume of top 5 commercial species >40 cm in DBH

9. The number of trees ≥40 cm DBH in MT increased most.
The number of trees <40 cm DBH in HT increased most.
High intensity
Medium intensity
Logging only
Low intensity
Prediction:
For the next several decades, the timber volume in HT may increase most with L least.

10. Will the increase of the abundance of commercial species alter the community functional composition?
Canopy opening regeneration of early successional species with rapid growth rates and low wood density lower community weighted wood density

11. How about a polycyclic silvicultural system were applied?
Trade-off between the number of commercial species and early- successional species

12. Did above-ground tree biomass, species diversity and composition recover to their pre-logging levels following different intensity treatments over 48 years?

13. Effects on biomass and species composition--
Immediate effects: Reduced basal area and species density through silvicultural treatments
Treatments L LT MT HT
Basal area (m2 ha−1)
Initial basal area pre-logging (1967)
61.7
53.2
48.1
58.0
Basal area reduction through treatment c
0 (0%)
12.4(40.8%)
17.2 (55.6%)
19.3 (65.4%)
Basal area post-treatment (1969)
35.6
17.8
13.7
10.2
The total number of species in each treatment (0.4 ha)
Initial number of species pre-logging (1967) 70 74 75
The number of species reduction through treatment
0(0%)
11 (20.0%)
24 (32.3%)
49 (70.5%)
The number of species post-treatment (1969) 55 48 42 18

14. Similar biomass increasing rates between treatments
Medium-term effects:
Similar biomass increasing rates between treatments
Only L and HT did not recover to their pre-logging levels.
How about long-term effects?
Logging only
Low-intensity
Medium-intensity
High-intensity

15. Things behind the biomass trajectories:
High intensity treatments resulted in less competition, pushed forests back to earlier successional states, with less remnants and more recruits, higher growth rates.
Fig.5 Ratio of the number of remnants post-treatment to the number of recruits over 46 years.

16. Species richness recovered to their pre-logging levels in L, LT and MT.
Reason: probably disperse from adjacent natural forests or from local seed and seedling bank.

17. Species composition in HT was altered by silvicultural treatment, and partially recovered over 46 years.
Takes longer for species composition to recover

18. Compositional similarity between treatments recovered.
Implication on large scales:
Lacking dispersion and local seed pools low resilience can not recover to original state divergence

19. Next step research
Is silviculture worthwhile in natural forests?- Financial analysis
Tree growth rates- Competition between individuals

20. Thanks very much for your listening!