Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 27Slide 28Slide 29Slide 30Slide 31Slide 32Slide 33Slide 34Slide 35Slide 36Slide 37Slide 38Slide 39Slide 40Slide 41Slide 42Slide 43Slide 44Slide 45Slide 46Slide 47Slide 48Slide 49Slide 50Slide 51Slide 52Slide 53Slide 54Slide 55Slide 56Slide 57Slide 58Slide 59Slide 60Slide 61Slide 62Slide 63Slide 64Slide 65Slide 66Slide 67Slide 68Slide 69Slide 70Slide 71Slide 72Slide 73Slide 74Slide 75Slide 76Slide 77Slide 78Slide 79Slide 80Slide 81Slide 82Slide 83Slide 84Slide 85Slide 86Slide 87Slide 88Slide 89Slide 90Slide 91Slide 92Slide 93Slide 94Slide 95Slide 96Slide 97Slide 98Slide 99Slide 100Slide 101Slide 102Slide 103Slide 104Slide 105Slide 106Slide 107Slide 108Slide 109Slide 110Slide 111Slide 112Slide 113Slide 114Slide 115Slide 116Slide 117Slide 118Slide 119Slide 120How do we account for these effects?Are there integrating variables that scale up?what regulates C gain or loss across scales?canopy processes increase range of light intensities over which light use efficiency (LUE) is constantleaf nitrogen (N): controls photosynthetic capacitythese variables are all correlated with each other: • net photosynthesis• leaf N• specific leaf area• leaf lifespanWhy?what regulates C gain or loss across scales?• net photosynthesis – balance between C- fixed & respired• leaf N concentration  N is necessary for making chlorophyll • specific leaf area  surface area: mass • leaf lifespan  fast or slow turnover?photosynthesis: a chemical overviewwhat are the biological tradeoffs?• low [N]• low photosynthesis capacity• small surface area:mass• slow turnover• high [N]• high photosynthesis capacity• big surface area:mass• quick turnoverimage source: http://www.wallpapers247.com/wallpaper/Big-Green-Leaf/http://www.pitzer.edu/offices/arboretum/scott_lawn/sage.aspleaf lifespan (months)specific leaf area (cm-2 g-1)leaf N (mg g-1)specific leaf area (cm-2 g-1)leaf N (mg g-1)net photosynthesis (nmol g-1sec-1)leaf N (mg g-1)leaf lifespan (months)NPP is about half of GPPwhat regulates C gain or loss across scales?source: Vourlitis et al. 2003: Spatial variation in regional CO2 exchange for the Kuparuk River Basin, Alaska over the summer growing season.what regulates C gain or loss across scales?GPP & ecosystem respiration both positively correlated with greenness (NDVI).these relationships make ecosystem C cycling modeling possible.leaf area index: leaf area per unit ground area  can be measured by satellite remote sensing to produce NDVI “greenness” indexlarge spatial scale modeling of GPPN content physiological activity  how much chlorophylllive green plants appear relatively dark in the PAR & relatively bright in the near-infraredMaximum NDVI(bimonthly average)Air temperature(average, daily)Solar radiation(average, daily)large spatial scale modeling of GPPsource: Vourlitis et al. 2003: Spatial variation in regional CO2 exchange for the Kuparuk River Basin, Alaska over the summer growing seasonmeasured NDVI for the Kuparuk watershed, northern Alaska (1994 & 1995)modeled ecosystem respiration for the Kuparuk watershed, northern Alaska (1994 & 1995)source: Vourlitis et al. 2003: Spatial variation in regional CO2 exchange for the Kuparuk River Basin, Alaska over the summer growing season high rate is 5 g C m-2 d-1modeled GPP for the Kuparuk watershed, northern Alaska (1994 & 1995)source: Vourlitis et al. 2003: Spatial variation in regional CO2 exchange for the Kuparuk River Basin, Alaska over the summer growing season high rate is 4 g C m-2 d-1high rate is 2 g C m-2 d-1modeled NEE for the Kuparuk watershed, northern Alaska (1994 & 1995)source: Vourlitis et al. 2003: Spatial variation in regional CO2 exchange for the Kuparuk River Basin, Alaska over the summer growing seasoncaveatsTo model NPP and NEE, you must model plant respiration. Not trivial  • respiration results from multiple processes with different rates in different tissues• roots cannot be remotely sensed• method requires lots of measurements (LAI, %N)What regulates productivity at an ecosystem scale? What controls leaf area, %N, etc. ?LIMITING RESOURCELiebig’s Law of the MinimumPlant growth is limited by a single resource at any one time. Another resource becomes limiting only when the supply of the first resource is increased above the point of limitation.Chapin et al. pg. 383By the deficiency or absence of one necessary constituent, all others being present, the soil is rendered barren for all those crops to the life of which that one constituent is indispensible. Translated from Liebig 1855Liebig’s Law of the MinimumIt is indisputable that, when a plant needs 12 substances to develop, it will not grow if any one of those is missing, and it will always grow poorly, when one of those is not available in a sufficiently large amount as required by the nature of the plant. Translated from Sprengel 1928Implications:1. If you add more of the limiting resource, production will increase.2. If you add anything else, production will be unaffected. This probably applies to crop plants, but does it apply to ecosystems?Liebig’s Law of the MinimumResource Supply(e.g. N, CO , etc.)2Production/Growth{ThresholdLimited byresourceLimited by either: A. Another resource B. Genetic limit to growthtesting Liebig’s Law of the Minimumtesting Liebig’s Law of the MinimumResource Supply(e.g. N, CO , etc.)2Production/GrowthAdd NAdd Ntesting Liebig’s Law of the MinimumResource Supply(e.g. N, CO , etc.)2Production/GrowthAdd NAdd Ptesting Liebig’s Law of the MinimumResource Supply(e.g. N, CO , etc.)2Production/GrowthAdd NAdd Catesting Liebig’s Law of the MinimumResource Supply(e.g. N, CO , etc.)2Production/GrowthAdd NAdd micronutrients: Fe, MgMaximum possible growth ratetesting Liebig’s Law of the Minimumissues:1. it isn’t absolute lowest quantity that matters, but relative lowest quantity.Supply < DemandDemand varies among species2. plants can shift allocation to control demand.e.g.: produce low nutrient foliageCAM photosynthesis 3. plants can control resource supply.e.g.: shift allocation to resource acquisition systems  root/shoot ratiotesting Liebig’s Law of the Minimumimagine: P is limiting N is notWhat does a plant do?• produce low P, high