internship sfs research project
Post on 18-Nov-2014
686 Views
Preview:
DESCRIPTION
TRANSCRIPT
Effects of Edge Orientation and Internal Fragmentation on Cyclone
Disturbance Patterns in Mabi 5b Fragments
Jeffrey Allenby
School for Field Studies
Center for Rainforest Studies
Queensland, Australia
Faculty Advisor: Amanda Freeman
Background
• History of severe fragmentation of Mabi 5b forest through land use over the last century
• Edge effects have become more of a problem as a result
• Interior habitat has become critically endangered
Cyclone Larry
• 20 March 2006 Cyclone Larry passed over the Atherton Tablelands
• Category 3 cyclone when it passed south of the fragments studied
• Winds over 100 km/h recorded in the area
Other research
• Impact of cyclones on individual tree species
• Influences of topography on cyclone disturbance levels
• Impact on flora after cyclone disturbance
Purpose
• To determine the effects of Cyclone Larry on Mabi 5b fragments
• To determine the effects of edge orientation on the patterns of disturbance
• To determine the effects of internal fragmentation on the patterns of disturbance
Study Site
• 6 Fragments of Mabi 5b• Curtain Fig (260 ha)• Wongabel (250 ha)• Tolga Scrub (80 ha)• Thomas Road (19 ha)• Picnic Crossing (16ha)• Favier’s Plot (1 ha)
Field Methods
• Took visual assessments on a 50m grid using the Curran Scale at 564 sites
Level Description0 No Disturbance-Canopy is still largely intact and mostly closed
1 Light Disturbance-No tree fall or stems snapped in the canopy. Canopy predominantly still intact with <25% loss
2 Moderate Disturbance-Canopy foliage retention is 25-50%. Larger limbs will be lost and fallen along with an occasional tree fall in the canopy.
3 Heavy Disturbance-Widespread defoliation of canopy and 50% canopy foliage removed. Extensive treefall or trunks have been snapped off.
Lab Methods
• Inputted and coded disturbance observations into a Geographic Information System (GIS)
• Overlaid Atherton Shire cadastre, Stanton and Stanton Vegetation Mapping, and aerial photographs provided by QPWS
Analysis
• Frequency of overall disturbance levels was calculated
• Frequency of disturbance levels was calculated for edges facing each of the 8 inter-cardinal directions
• Performed a Chi-square test on wind direction and disturbance levels
Results
15%
36%
47%
2%
0
1
2
3
Level
• Disturbance levels overall were high:
Results
• Wind hit the southwestern, western, northwestern, and northern edges the hardest
78%
22%
9%
9%
36%
46%
4%
44%
39%
13%
8%
46%31%
15%
17%
63%
20%
4%
13%
30%
53%
5%
95%
22%
78%
E
N
S
W
0
1
2
3
Level
Results
• Chi-Square analysis shows a strong correlation between edge orientation and levels of disturbance.(χ2=134.493, P=.000, df=14)
Edge Orientation
• There is a higher than expected frequency of heavy disturbance on the western edges
• There is a higher than expected frequency of light to moderate disturbance on the eastern edges
• Consistent with previous findings of cyclone disturbance patterns
Internal Fragmentation
• If fragmenting element is narrow (road or stream) and parallel to the wind:
Tolga Scrub
Wongbel (southern section)
Internal Fragmentation
• If fragmenting element is narrow (road or stream) and curves:
Wongabel (northeastern)
Curtain Fig(southern)
Internal Fragmentation
• If fragmenting element is narrow (road or stream) and perpendicular to the wind:
• Consistent with information about windbreaks
Tolga Scrub
Internal Fragmentation
• If the fragmenting element is wide (forestry plot):
Wongabelinterior edge
(western section)
WongabelInterior edges
(northeastern section)
Limitations and Future Research
• Lower levels of data collected for inter-cardinal directions (NE-SE-SW-NW)
• Not enough examples of effects of internal fragmentation to be conclusive
• Further research into the effects of internal fragmentation on disturbance patterns needs to be done
Conclusions
• Edge orientation plays a large role in determining disturbance patterns
• Internal fragmentation appears to play a large role in determining interior disturbance patterns depending on orientation and shape
• Both edge orientation and internal fragmentation influence how far into the fragments edge effects are seen
Acknowledgements
Thanks to • My research partner Melissa Schlothan for helping me
collect, assemble and make sense of our data • The Plant and Bird DR groups for helping gather data• Amanda Freeman and Tim Curran for providing insight
and assistance at every stage of the work• Mabi Project: Scientific Purposes Permit WISP02094504• Queensland Department of Natural Resources, Mines
and Energy: Atherton Cadastre• Wet Tropics Management Authority: Stanton and
Stanton Vegetation Mapping
top related