1. Primary Production in Terrestrial Systems Fundamentals of Ecosystem Ecology Class Cary Institute January 2013 Gary Lovett

2. Equations and Definitions 1.Net Primary Production = Net C fixation by autotrophs 2.NPP = GPP – R a 3.NPP =  Biomass + Consumption + Detritus + Exudates

3. CO 2 GPP NPP Detritus and exudates Not decomposed Organic C export Accumulation in sediments or soil Consumers RaRa Decomposers RhRh Accumulation in biomass NEP (R e = R a + R h ) Oxidation (Fire or UV) Organic C import Components of Productivity

4. Measurement of Productivity in Terrestrial Ecosystems  Usually by measurement of fates of C Accumulation in biomass  Diameter growth/ allometric equations in forests (usually over several years)  Harvest in grasslands (usually annually) Detritus Herbivory Other fates of carbon  Aboveground vs. belowground

5. Normalized Difference Vegetation Index (NDVI) = (NIR – VIS) / (NIR + VIS)

6. NPP using remote sensing of nitrogen plus a productivity model From Ollinger and Smith Ecosystems 2005

7. Typical NPP values (g C/m 2 /y) Desert, poor tundra0-100 Grassland, shrubland100-350 Temperate forest300-800 Tropical forest600-1000 Wetland, sugar cane, rice>1000 Note: Sometimes expressed in biomass units (g dry mass), equal to roughly carbon x 2

8. From E.A. Schuur. Ecology 2003. NPP (Mg C/ha/y) Global Patterns of NPP

9. From Vitousek 2004 Ky (kiloyears) refers to age of geological substrate on these Hawaiian Islands C = Control, N = N addition, P = P addition, NP = N+P addition Nutrient Limitation in Forests Switch in limitation over time Liebig’s Law of the Minimum and multiple limitation

10. Different sites across the Great Plains Different years at one site in CO From Lauenroth and Sala 1992. Variation in ANPP in Grasslands

11. Equations and Definitions 1.Net Primary Production = Net C fixation by autotrophs 2.NPP = GPP – R a 3.NPP =  Biomass + Consumption + Detritus + Exudates 4.Net Ecosystem Production is the net carbon exchange with the atmosphere 5.NEP= GPP - R e = GPP - R a – R h = NPP – R h 6.R e = R a + R h 7.NEP= organic C accumulation in ecosystem (biomass, soils/sediments, detritus) + net export of organic C

12. CO 2 GPP NPP Detritus and exudates Not decomposed Organic C export Accumulation in sediments or soil Consumers RaRa Decomposers RhRh Accumulation in biomass NEP (R e = R a + R h ) Oxidation (Fire or UV) Organic C import Components of Productivity

13. Eddy Covariance Requires: homogeneous surface, tower above the canopy, fast response sensors for wind and CO2 Measures: Net Ecosystem Exchange (NEE) What does this represent? Net flux of CO2 = Downward flux – upward flux

14. LiCor 6400 Portable Photosynthesis System Measures: Net photosynthesis of leaves How do you scale up?

15. Evolving knowledge: How does increasing N deposition affect C storage in forests? 1990s: Global models assumed N fertilization of tree growth, leading to enhanced C storage (e.g. ~ 2 Pg C/yr, Holland et al. 1997) 1999: Nadelhoffer et al summarized 15 N addition studies in Europe and NA, showed most 15 N stored in soils (low C:N) rather than in wood (high C:N). Global C sink estimated at 0.25 Pg C/y. 2000s: Multiple papers and reviews showing that N addition increases soil C storage by decreasing decomposition and soil CO2 release 2007: Magnani et al reported eddy covariance /modeling at multiple sites in Europe/NA. Strong relationship between N deposition and tree growth and C storage, dC/dN>200 2007-9: DeVries, Sutton, others: Criticism of Magnani et al in literature. dC/dN too high. 2008: Hyvonen et al, Devries et al: Experimental N additions in European forests show dC/dN of ~ 20-30 for trees and 10-15 for soil. 2010: Thomas et al. show statistical relationship between N deposition and tree growth in Northeastern US, varies by tree species, dC/dN=61, global N-induced C sink = 0.31 Pg C/y.