140 likes | 260 Views
I R S S. Predicting tree diversity across the U.S.A. as a function of Gross Primary Production. Richard Waring 1 , Joanne Nightingale 1 , Nicholas Coops 2 & Weihong Fan 3 1 Oregon State University 2 University of British Columbia 3 Richard Stockton College of New Jersey.
E N D
I R S S Predicting tree diversity across the U.S.A. as a function of Gross Primary Production Richard Waring1, Joanne Nightingale1, Nicholas Coops2 & Weihong Fan3 1 Oregon State University 2 University of British Columbia 3 Richard Stockton College of New Jersey
Outline • Theoretical relationship between productivity and tree species richness • Measures of tree species richness & forest productivity – model / satellite • Data quality • Actual relationships between productivity and tree species richness
Theoretical Relation between Productivity and Tree Diversity Light limiting from competition with a few fast-growing species All but light limiting No factor entirely limiting
Model GPP with 3-PG Recorded Tree richness n = 10 300 CVS plots Theory tested in the Pacific Northwest(Swenson & Waring 2006 Global Ecology & Biogeography)
10 ha CVS data per 100 km2 R2 = 0.71 0.5 ha FIA data per 100 km2 R2 = 0.16 Tree richness predictable from modeled GPP
Measures of GPP Increasing complexity Satellite data Climatic data Soils data
Quantum / Radiation Use Efficiency x x PAR PAR Environmental Modifiers VPD MODIS Modifiers Tmin GPP Soil Water Additional 3-PGS Modifiers Water Balance ??? Rainfall Models of GPP (3-PGS & MODIS GPP)
MODIS GPP ~40% higher than 3-PGS estimates Highly sensitive >20% Moderate sensitivity 5-20% Not sensitive 5% Soil Water Sensitivity
W. Hargrove Soil Nitrogen ORNL W. Fan Soil Nitrogen How “good” is our Soils data anyway??
North West North East West Central East South West EPA Level 1 Ecoregions
Annual Average Maximum NDVI Exp R2 = 0.55 Annual Average Maximum EVI Exp R2 = 0.68 Satellite Index
Annual Average MODIS GPP Power R2 = 0.51 Annual Average 3-PGS GPP Polynomial R2 = 0.53 GPP Models
Correlations MODIS EVI (maximum) 0.68 MODIS GPP (growing season) 0.64 3-PGS (annual average ) 0.53 Poly Note: all models are highly correlated with 3-PGS, R2 ~ 0.7
Conclusions • NDVI & EVI saturate at high levels of productivity (GPP >15 tC/ha/yr) • MODIS GPP (& SPOT NPP) in error with drought • 3-PGS limited by soil & climate – but estimates full range of forest productivity across the USA • If vegetation indices match changes predicted by more complex models, climate change may be inferred