Modeling and remote sensing link soil water storage effects to forest LAI Richard Waring 1 & Auro Almeida 2 1 College of Forestry Oregon State University Corvallis, Oregon, U.S.A. 2 CSIRO Sustainable Ecosystems Hobart, Tasmania, Australia Photo: Courtesy of Auro Almeida
Plantations & Native Vegetation in Brazil may differ by 2-fold in LAI Source: lamar.colostate.edu/~binkley/ Brazileucalyptus.htm Source www.fredhoogervost.com/photo 06435 Modified from Fig. 7:Almeida and Soares. Revista Árvore (2003) 27: 159-170.
yet use similar amounts of water because maximum stomatal conductances differ: Native forest = 0.01 m s -1 ; Eucalypt plantation =0.02 m s -1 240 Native forest Eucalypt Available soil water (mm) 200 160 120 80 40 0 4-Nov-99 29-Dec-99 16-Feb-00 12-Apr-00 30-May-00 16-Aug-00 11-O ct-00 30-Jan-01 2-May-01 19-Sep-01 28-Dec-01 Date Derived from: Almeida and Soares. Revista Árvore (2003) 27: 159-170.
In other places, plantations use much more water than the native vegetation Photo: Courtesy Peter Dye, Univ. of Witwatersrand, South Africa
Modeled variation in LAI and water use by three types of vegetation in eastern Australia Source: Feikema et al. 2007. MODSIM 07. Int. Congress Modelling & Simulation Society of Australia and New Zealand
How do we predict growth and water use by different types of vegetation? Leaves Answer: Need vegetation-specific process models to link carbon & water cycles Source: Martti Peramaki, Ph.D. Thesis, Dept. of Forest Ecology, University of Helsinki, Finland
Process models predict seasonal and interannual variation in LAI, MAI, and available soil water (points =data, lines =simulations) Source: Almeida et al. For. Ecol. & Mgmt. (2004) 193:179-195 200 250 Available soil water (mm) 150 100 50 200 150 100 50 Precipitation (mm) 0 0 10/1998 04/1999 10/1999 04/2000 10/2000 04/2001 10/2001 04/2002 Source: Almeida et al. For.Ecol. & Mgmt (2007) 251:10-21 10/2002 04/2003 10/2003 04/2004
Monthly real climatic data are required to predict variation of CAI in drought-prone regions Eucalyptus plantation in eastern Brazil Source: Almeida et al. For. Ecol. & Mgmt. (2004) 193:166-177
As the soil water deficit increases beyond a threshold ( ), the water loss through transpiration is progressively reduced below its potential Eucalyptus maculata Source: Landsberg & Gower 1997. Fig. 4.5. Application of Physiological Ecology to Forest Management. Academic Press, San Diego, CA
If all stored water is exhausted, tree mortality increases and LAI is reduced 4-year old plantation of Eucalyptus globulus during a drought experiences significant mortality in western Australia if soil water storage capacity is <325 mm. Photo: Keith Smettem, Univ. of W. A., Perth, Au. Source: Harper et al. Plant and Soil (2008) in review
Challenge to measure available soil water storage capacity because rooting depth is not easily measured Eucalyptus marginata 28 m depth that roots penetrate Photo: Courtesy of Keith Smettem, University of Western Australia
Modeled LAI when soil water storage capacity is 100, 180, and 400 mm [LiCor 2000 LAI (o)] LAI LAI obs LAI 100 mm LAI 180 mm LAI 400 mm 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 Age (year) Simulations by Auro Almeida for E. grandis hybrid plantation on Aracruz Celulose S.A. lands in eastern Brazil
Satellite-derived maps keep track of changes in land cover 2001-2004 Source: Morton et al. PNAS (2006) 103:14637-14641.
Differences in spectral reflectance provides estimates of LAI from space Source: Nemani et al. Int. J. Remote Sensing (1993)14: 2519-2534.
Estimation of LAI with Landsat imagery Range of temperate and boreal evergreen forests with and without an understory Source: Nemani et al. Int. J. Remote Sensing (1993)14: 2519-2534. 4 LAI from LiCor 2000 3.5 3 2.5 2 y = 0.809x + 0.847 R 2 = 0.92 1.5 1.5 2 2.5 3 3.5 4 LAI from NDVI c Eucalyptus plantations in South Africa Source: Megown, Webster & Jacobs: ffp.csir.co.za/research/rs_lai_paper.pdf
Conclusions Soil drought is a major constraint on productivity Need to compare water use by plantations with that of native vegetation Process-based models link soil water storage capacity with variation in LAI Remote sensing permits accurate estimates of LAI ± 0.5 m 2 m 2 over the critical range Spatial analyses of landscapes can account for variation in productivity & water use
Richard.Waring@oregonstate.edu Auro.Almeida@csiro.au Photo: Waring, R.H. 1982. Land of the Giant Conifers. Nature History 91: 54-63.