Long-term responses of rainforest erosional systems at different spatial scales to selective logging and climatic change

Long-term (21—30 years) erosional responses of rainforest terrain in the Upper Segama catchment, Sabah, to selective logging are assessed at slope, small and large catchment scales. In the 0.44 km 2 Baru catchment, slope erosion measurements over 1990—2010 and sediment fingerprinting indicate that s...

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Bibliographic Details
Published in:Philosophical transactions of the Royal Society of London. Series B. Biological sciences 2011-11, Vol.366 (1582), p.3340-3353
Main Authors: Walsh, R. P. D., Bidin, K., Blake, W. H., Chappell, N. A., Clarke, M. A., Douglas, I., Ghazali, R., Sayer, A. M., Suhaimi, J., Tych, W., Annammala, K. V.
Format: Article
Language:English
Subjects:
Cesium Radioisotopes - analysis
Climate Change
Computer Simulation
Cyclonic Storms
Data-Based Mechanistic Modelling
Erosion
Geologic Sediments - analysis
Geologic Sediments - chemistry
Landslides
Lead Radioisotopes - analysis
Logging
Malaysia
Old growth forests
Radionuclides
Rain
Rain - chemistry
Rainforest Logging
Rivers - chemistry
Sediment Fingerprinting
Sediment Transport
Sediments
Spectrometry, Gamma
Suspended solids
Time Factors
Trees - chemistry
Tropical rain forests
Valleys
Watersheds
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Summary:Long-term (21—30 years) erosional responses of rainforest terrain in the Upper Segama catchment, Sabah, to selective logging are assessed at slope, small and large catchment scales. In the 0.44 km 2 Baru catchment, slope erosion measurements over 1990—2010 and sediment fingerprinting indicate that sediment sources 21 years after logging in 1989 are mainly road-linked, including fresh landslips and gullying of scars and toe deposits of 1994—1996 landslides. Analysis and modelling of 5—15 min stream-suspended sediment and discharge data demonstrate a reduction in storm-sediment response between 1996 and 2009, but not yet to pre-logging levels. An unmixing model using bed-sediment geochemical data indicates that 49 per cent of the 216 t km -2 a -1 2009 sediment yield comes from 10 per cent of its area affected by road-linked landslides. Fallout 210 Pb and 137 Cs values from a lateral bench core indicate that sedimentation rates in the 721 km 2 Upper Segama catchment less than doubled with initially highly selective, low-slope logging in the 1980s, but rose 7—13 times when steep terrain was logged in 1992—1993 and 1999—2000. The need to keep steeplands under forest is emphasized if landsliding associated with current and predicted rises in extreme rainstorm magnitude-frequency is to be reduced in scale.
ISSN:0962-8436
1471-2970
DOI:10.1098/rstb.2011.0054