Overstorey and juvenile response to thinning and drought in a jarrah (Eucalyptus marginata Donn ex Sm.) forest of southwestern Australia
- 375 Downloads
Forest thinning is expected to affect tree water use and carbon assimilation, but the related influence from climate variability is little known. Recent forest thinning in the Wungong catchment coincided with a record dry year following the thinning, which provides a rare opportunity to understand the climate influence on the thinning effect.
A field experiment was conducted to examine changes before and after thinning, especially the rainfall, soil moisture, leaf water status, tissue isotope signature (13 C and 15 N) and N concentration of overstorey and understorey juvenile trees of Eucalyptus marginata (Donn ex Sm.).
Despite the post-thinning drought, surface soil was moister and juvenile jarrah plants were less water stressed, attributable to reduced rain interception and transpiration as a result of less canopy cover. The overstorey was under stress but mainly due to drought rather than by thinning. The concentration of N declined in both tree stems and juvenile leaves along with available N in soil, suggesting a soil N limitation. No treatment effects were detected from leaf relative water content and tissue isotope signature (13 C and 15 N).
The drought effects were superimposed over the thinning effects on overstorey growth, with stemwood δ13C being a major indicator of water stress. The water relations and carbon assimilation of understorey juveniles were however dependent more on topsoil moisture, and the wetter soil during the year following thinning enhanced growth activity and hence the depletion of 13 C (more negative δ13C) in juvenile leaves.
KeywordsForest thinning Drought Leaf relative water content δ13C δ 15 N N limiting
This work forms a part of the study supported by the Australian Research Council and the Water Corporation of Western Australia under the Linkage Projects scheme (project number LP0774966). We thank Frank Batini, Michael Loh, Richard Boykett and Frank Bailey for providing background information and field support for this study. Jing Jing Huang and Sita Ram Panta contributed to the some field data collection during their postgraduate study.
- Anon (1930) Thinning operations in forestry. Nature 130:743Google Scholar
- Bari MA, Ruprecht JK (2003) Water yield response to land use change in South-west Western Australia. Department of Environment Salinity and Land Use Impacts Series, Report No. SLUI 31. November 2003. Department of Environment, Western Australia. p 46Google Scholar
- Campbell-Clause JM (2005) Using gypsum blocks to measure soil moisture in vineyards. Farmnote, Western Australia Department of Agriculture and Food, No. 03/98. Perth, Australia.Google Scholar
- Grigg AH, Grant CD (2009) Overstorey growth response to thinning, burning and fertiliser in 10–13-year-old rehabilitated Jarrah (Eucalyptus marginata) forest after bauxite mining in South-Western Australia [online]. Aust Forestry 72:80–86Google Scholar
- Institute of Foresters of Australia (2007) Australia native forests and water. IFA forestry policy statement number 5.1. www.forestry.org.au (accessed on 23 August, 2011)
- Macfarlane C, Silberstein R (2009) Final Report to the Water Corporation of Western Australia on Water Use by Regrowth and Old-growth Jarrah Forest at Dwellingup, Western Australia. Water for a Healthy Country Flagship Report series ISSN: 1835-095X. CSIRO 2009, Perth, Australia. p 26Google Scholar
- Mattiske EM, Havel JJ (1998) Vegetation Complexes of the South-west Forest Region of Western Australia. Maps and report prepared as part of the Regional Forest Agreement, Western Australia for the Department of Conservation and Land Management and Environment Australia, Perth, Australia.Google Scholar
- Panta, SR (2012) Effects of thinning on forest structure and composition in the Wungong Catchment, Western Australia. M.Phil. thesis Murdoch University, AustraliaGoogle Scholar
- Peet GB, McCormick J (1971) Short-term responses from controlled burning and intense fires in the forests of Western Australia. Bulletin no. 79. Western Australia Forests Department, Perth, Australia, p 23Google Scholar
- Peri PL, Ladd B, Pepper DA, Bonser SP, Laffan SW, Amelung W (2011) Carbon (δ13C) and nitrogen (δ15N) stable isotope composition in plant and soil in Southern Patagonia’s native forests. Glob Change Biol. doi: 10.1111/j.1365-2486.2011.02494.x
- Silberstein R (2010) Water yield and vegetation dynamics under changing climate and management –results and projections from the Water Foundation project 041 05. http://www.watercorporation.com.au/_files/Wungong/Research_Forum/2010_Richard_Silberstein_Presentation.pdf
- Soil Survey Staff (2003) Keys to soil taxonomy. 9th edn. USDA-NRCS. U.S. Government Printing Office, Washington, DC.Google Scholar
- Water Corporation (2005) Wungong catchment environment and water management project. Water Corporation, Perth, p 134Google Scholar