# Presentation: 071911

## FACE Network*

- Presented by:	Bob Nowak
- 		Stan Smith
- Assistance from:	Hormoz BassiriRad
- 		Terri Charlet
- 		Dave Ellsworth
- 		Dave Evans
- 		Lynn Fenstermaker
- 		Eric Knight
- 		Peter Reich
- 		Participants of FACE 2000 Conference

- * aka FACE Universal Network (Norby 2000)

## F.U.N. Charges

- How do the various experiments work together as a network?
- Can we increase the efficiency of CO2 use?
- What measurements are being conducted and can they be critically compared?
- What general ecological principles are being discovered?
- What is the value-added from the network?

## Non-agricultural FACE Network

- Base map courtesy CDIAC

## Global Vegetation Types

## FACE Design & Protocols

- 	_Mini-FACE_	_BNL_	_Other_
- CO2 fumigation design	46%	36%	18%
- 	_Seasonal_	_All year_
- Yearly CO2 treatment period	77%	23%
- 	_Daylight_	_24 hour_	_Unknown_
- Daily CO2 treatment period	36%	41%	23%
- CO2 control point
-  86% of sites effectively have [CO2] ~550 (± 10%)
-  90% of these control to set [CO2]; 10% control as +200
-  9% of sites control to <495; 5% control to >605
-  9% of sites have >1 elevated [CO2]

## Increasing Efficiency of CO2 Use

-  Preventative maintenance
-  Keep CO2 delivery system sealed and fully operational
-  Potential design enhancements
-  Improve response time of system
-  Increase turbulence mixing

**Notes:**
Theoretically, there is a limit -- have to raise the CO2 concentration of a certain volume of air.  Extensive trials during early design phases, e.g. by BNL, generally have largely maximized CO2 uniformity and minimized CO2 use.  But even is can increase CO2 efficiency by a few %, its still $1,000’s.
Preventative maintenance

## Turbulent Mixing: Vortex Generators

**Notes:**
Install vortex generator in riser to give turbulent component to an essentially laminar flow of air.  Twisted sheet metal; fixed fan blades.

## Variables Measured

- 	_Yes (%)_	_No / Unk (%)_
- Physiology
- Leaf gas exchange	54	46
- Root physiology	27	73
- Aboveground production
- Biomass	100	--
- Litter	59	41
- Carbon pools/fluxes	36	64
- Nitrogen pools/fluxes	100	--
- Belowground production
- Root	59	41
- Microbial	32	68
- Carbon pools/fluxes	41	59
- Nitrogen pools/fluxes	41	59
- ET / Soil water content	54	46
- Biodiversity
- Plants	91	9
- Herbivores	32	68

## Predictions: Leaf physiology

-  Leaf photosynthesis increases under elevated CO2, although down-regulation may or may not occur
-  Stomatal conductance decreases under elevated CO2
-  Consequently, water use efficiency at the leaf level increases

## Dominant species responsesto elevated CO2: how large is enhancement? 

**Dominant species responses****to elevated CO****2****: how large is enhancement?**** **

**Data from:**
**Ellsworth et al.**

**Yellow Bars:**
**compiled from literature**
**and unpublished results**

**WI         MN       NC     NV**

## Enhancement dependence on leaf N

**Enhancement dependence on leaf N**

**Data from:**
**Ellsworth et al.**

## Enhancement dependence on leaf N

**Enhancement dependence on leaf N**

**Data compiled from literature and unpublished sources:**
**Duke, Rhinelander, Oak Ridge, Maricopa, Nevada, Switzerland, Italy**

## Predictions: Productivity

- After Strain & Bazzazz (1983)

## Results: Shoot production

- JRGCP, NDFF, NZGraze, ORNL, & Swiss

**Results: Shoot production**

## Predictions: Root processes

-  Because of greater carbon assimilation rates, root processes (growth,  turnover, or exudation) increase under elevated CO2
-  Because of increased plant size (and despite decreased nutrient concentrations per unit tissue weight), _whole-plant_ nutrient uptake increases
-  *BUT* nutrient uptake per unit root length/biomass may or may not increase

## Results: Root processes

-  Some sites have increased root biomass
-  Grasslands (BioCON, JRGC, Swiss)
-  Forests (FACTS-I, ORNL)
-  Some sites have no change in root biomass
-  Desert (NDFF)

## Predictions: Water balance

-  Reduced stomatal conductance under elevated CO2 reduces leaf water use
-  If reduced conductance scales to the canopy, then canopy transpiration decreases and soil moisture is conserved under elevated CO2
-  *BUT* increased growth (shoot and root) and increased canopy temperature at least partially offsets this conservation of soil moisture

## Results: Soil water at NDFF

**Results: Soil water at NDFF**

## Predictions: Nutrient cycling

-  Because of increased availability of carbon substrates, microbial activity, including N-fixers and mycorrhizae, increases, and thus alters N cycling
-  *BUT* effects on N availability could be positive or could be negative

## Flow diagram from Evans

## Results: Nutrient Cycling 

- Deciduous forest

- Conifer forest

- Grassland

- Chaparral

- Desert

- Data from BassiriRad & Evans

## Predictions: Biodiversity

-  Because co-occurring species differ in their response to CO2, there will be winners and losers ... *BUT* can rarely extrapolate from monoculture studies
-  Because more diverse species assemblages often produce greater biomass per unit area, elevated CO2 has greater effects in more diverse communities
-  Because growth rate, fecundity, and water use efficiency of  plants increase under elevated CO2, invasions occur where water or nitrogen limit recruitment (*e.g.* invasions of woody plants into grasslands; invasive species)
-  Perturbations and disturbance (*e.g.* fire, grazing, pathogens) and concomitant global changes (*e.g.* warming, altered precipitation, increased UV-B) interact with and alter CO2 responses

## Winners & Losers: BioCON

**Winners & Losers: BioCON**

- Data from Reich

## Winners & Losers: Observed Responses at Elevated CO2

-  Shift to dicots in grasslands
- Swiss –  legume
- NZ Graze –  legume
- MEGARICH –  dicots
- JRGC –  dicots
- BioCON –  dicots
-  Potential for increase of invasives
- FACTS-I –understory invader
- ORNL – understory invader
- NDFF – annual grass

## + N, - CO2

**Species Richness**

**Production**

**+ N, + CO****2**

**+ N, **-** CO****2**

- -** N, **-** CO****2**

- -** N, + CO****2**

***Diversity Increases CO******2****** Effect: Hypothetical Response Curves***

- From Reich

**Notes:**
-N, -CO2 = At ambient CO2 and soil N conditions, ecosystem parameters will increase with species richness.
+N, +CO2 = Under elevated CO2 and N,  productivity will increase in plots at all levels of species richness, but will increase more with increasing species richness. 
+N, -CO2 = Given that N is the limiting resource at this site, ambient CO2 plus elevated N treatments should lead to heightened productivity in all plots, but with a greater increase at high species richness. 
-N, +CO2 = For Ambient N levels:  If the effect of elevated CO2 is independent of N limitation, CO2 enhancement of productivity should occur at all levels, with greater enhancement at high diversity.    Or    If available N is already being utilized fully by the species-rich plots, elevated CO2 may cause a slight enhancement of productivity in species rich plots, and a greater enhancement in low richness plots.  

## BioCON –Biomass response (average 1998, 1999)

**BioCON***** –******Biomass response (average 1998, 1999)***

- Reich *et al*. (2001) Nature

## Results: Increased fire cycle

- Smith *et al*. (2000) Nature

## Slide 28

## Slide 29

## Community change

- _Community change_

- Photos by T. Huxman & T. Esque

## Predictions: Evolution

-  Because of the rapidity of increased CO2, evolution may have little potential role ... *BUT* evolutionary response likely:
-  in species (*e.g.* pests) with large population sizes (>105), short generation times (<1 year), and high intrinsic growth rates
-  where migration and dispersal are limited (*e.g.* habitat islands)
-  Evolutionary responses depend on:
-  the extent that phenotypic *vs.* genotypic processes occur
-  resource availability, including population density
-  level of intraspecific variation, especially compared to interspecific variation

**Predictions: Plant-animal interactions**

-  Increased C:N ratios of foliage may:
-  lead to increased consumption by insect herbivores but decreased consumption by large ruminants
-  alter growth,  development, and reproduction of all herbivores

## Two contrasting points of view:

**FACE or OTC experiments mimic future [CO****2****] so that observations**
**       ****from the experiments represent ecosystem responses to [CO****2****].**
**Current experiments exert an ecosystem perturbation – a step-increase in  [CO****2****] –  achieved primarily by altering carbon influx.**
_**Solutions to step-increase problem:**_
**Analyze data from FACE experiments using inverse approach to challenge the structure of existing models and derive parameter values.**
**2.    Collect highly accurate, informative data by improving experimental design and measurement plan for the FACE network.**

**Luo (2001) New Phytol.**

## Need for Data Archives

**Facilitate cross-site comparisons**** **
**  ****Compiled results**
** ****data means, relative enhancements with SE, **
** ****in data base, spreadsheet, or ASCII format**
**New ways to analyze old data**
**  ****Raw data sets **
** ****quality checked, quality controlled**
**FACE** **NETWORK**
-        Should some measurements be taken at every site?
-        Can we standardize measurement protocols?
-        How and where to archive the data?

## Slide 34

## CDIAC 

- Carbon Dioxide Information Analysis Center

**FACE Data: Oak Ridge, Tennessee **
- The following data, and summary documentation, from the Oak Ridge, Tennessee, FACE site are now available from CDIAC:
- _weather data_
- _CO 2 data_ - coming soon!
- _tree basal area data_ - coming soon!
- _leaf production data_ - coming soon!
- Relevant publications:
- Norby, R. J., et al. 2001. Allometric determination of tree growth in a CO 2 -enriched sweetgum stand. *New Phytologist*
- 150(2):477-487.
- Wullschleger, S. D., and R. J. Norby. 2001. Sap velocity and canopy transpiration in a sweetgum stand exposed to free-air CO 2
- enrichment (FACE). *New Phytologist *150(2):489-498.
- _FACE Home_
- _CDIAC Home_
-      *10/2001*

- http://cdiac.esd.ornl.gov/programs/FACE/ornldata/ornldata.html

## CDIAC DOCUMENTATION

- Data is checked and corrected for unrealistic large or small values.
- Daily statistics are calculated only for those variables with at least 12 good hourly values
- X-Y scattergrams are used to check for outliers and consistency among the data loggers.

-    Example:  Contents and format of the hourly files, r*_wh_*.dat.

**DESCRIPTION and FORMAT OF THE ASCII DATA FILES**

**SAS, FORTRAN, and C CODES TO ACCESS THE DATA**
- Import code for each file type

## F.U.N. Charges

- How do the various experiments work together as a network?
- Can we increase the efficiency of CO2 use?
- What measurements are being conducted and can they be critically compared?
- What general ecological principles are being discovered?
- What is the value-added from the network?