1Dave Egan Emilie Grossmann Jeanine Rhemtulla Land-use changes in the temperate forest biome: Implications for carbon-cyclingDave EganEmilie GrossmannJeanine Rhemtulla
2Temperate Forests: Small in area but important biologically & politically Smallest forest biomeLowest carbon content of all forest biomesLongest history of intensive land-useThe missing sink?Politically powerful
3Small in area Small amount of stored carbon We could ditch this slide and just talk about it a little later – I think slide 15 is where I was going to put the descriptive stats on the temperate(Dixon et al 1994)
4Longest history of intensive land-use Much longer history of intensive land-use than either the tropics or boreal biomesRemaining old-growth:< 1% Europe2-3% Australia (temperate eucalypt forests)~ 25% New Zealand3 – 5 % United States(Norton 1996 & WWF 1997)
5Land-use IIChina: Temperate forests are known primarily from the fossil record – most forest was cleared for intensive agriculture 4000 years ago.Eastern United States: Clearing for timber and agriculture started in 1750’s and swept westward thereafter.Land Clearing in Harvard Forest, Fisher Museum Dioramas
6Figure credit: Woods Hole Research Center The missing sink?Figure credit: Woods Hole Research Center
7Figure credit: Woods Hole Research Center Missing sink IIForests are generally increasing in area throughout the temperate biome:Forest aggradation in eastern U.S.Forest restoration in ChinaPlantations in New Zealand“the coterminous United States, Europe, China, and small Eurasian countries contained one-third of the [northern hemisphere’s] forest and woodland area, but accounted for at least 80% of the observed C-sink. This disproportionate sink in temperate regions relative to boreal regions likely reflects the temperate zone’s legacy of large-scale land-use management and change over the last century, and fire-suppression policies in recent decades.” (Goodale et al. 2002)Figure credit: Woods Hole Research Center
8Politically powerfulThe G8 nations (with the exception of Canada and Russia) contain primarily temperate forest.Much of the world’s political and financial power resides in these nations.Is there a policy bias that favours nations of the temperate biome?
9Types of temperate forest biome Two major types:Broadleaf deciduous forestEvergreen forestCould combine this with the next slide if we want, or add some photographs or something
10Broadleaf deciduous forest Most temperate forests are deciduousThese forests occur in:Eastern United States & adjacent CanadaWestern & Central EuropeEastern Asia, including Korea, Japan, parts of China and RussiaUsually what comes to mind when someone says “temperate” – short warmMaybe use a map as a background for these slides??Hopkins Memorial Forest, Williamstown, MA
11Coniferous and broadleaf evergreen temperate forest Mixed evergreen forests are a much smaller component of the temperate forest biomeThey are found primarily in western North America, Chile, New Zealand, and AustraliaPhoto is of beech forests in New Zealand – needs layout help!
12Working definitions of “temperate” Biological issues:Ecotone between boreal and temperate forestsGeographic issues:Europe often includes Nordic countriesChina is not usually splitUS & Canada are often lumpedConsistency issues:“mid-latitude” (Dixon et al. 1994)re-interpreted as “temperate” (Mahli et al. 1999)I’ll flesh this out with the references – basically say that there’s no consistent stratification of the temperate biome - different papers use different regions which make comparison difficult
14Shows the ecotone issue – Navy is “Evergreen-Deciduous Mixed Forest” – does anyone know how to make a little box around that item on the legend and insert a zoomed in piece of the legend so people can read it??
15Definitions of “forest” and “woodland” A forest is defined as “A plant community composed of trees the crowns of which touch, forming a continuous canopy.”A woodland is defined as “A plant community that includes widely spaced, mature trees the crowns of which do not touch and generally have a canopy closure of 40 percent or less.”(The Concise Oxford Dictionary of Ecology, 1996)I’ll add some details. Might also include the nebulous status of plantation forests
16Temperate Forest AreaData from Dixon et al.(1994), Goodale et al. (2002), & Fang et al. (2001)
17Carbon storage in the temperate biome: State of the knowledge Complementary approaches:Global/continental/regionalAtmospheric studiesLand-use studiesForest inventory/allometryMeta-analysisLocalEddy fluxStand measurements
21Local controls on carbon fixation There has been a lot of mechanistic work done at this scalePatterns seen at larger scales are a composite of local phenomenaWe ultimately manage, and use land at a local scale
22Controls on carbon fixation at a small scale Many things limit carbon fixation:Forest age (Klopatek 2002)Water limitations (Irvine et al. 2002)Carbon dioxide limitationsNitrogen limitations (Nadelhoffer et al. 1999)Ozone pollution (Ollinger et al. 2002)Forest type
23CO2 fertilization hypothesis FACE Experiment, Duke ForestNPP increased by 25%(measurements included roots!)This study was done on a young, aggrading, temperate deciduous forest.This should be considered a maximum response.(DeLucia et al 1999)
24Missing pieces: Below-ground We understand the general processes that limit soil C storage in undisturbed soil reasonably well.We also understand the trends of how land use change influences soil C storage, but need more field measurements.Moving to a larger scale requires modeling.We also need to synthesize this information with the data we have above-ground.
25Amundson 2001: Regression derived from Post et al.’s 1982 data Modeled SOCLots of modeling has been done to explain how SOC relates to climate.Amundson 2001: Regression derived from Post et al.’s 1982 data
26Here’s some summary data on soil C storage Here’s some summary data on soil C storage. The data are pretty good though (usually more than 100 soil pits, for these life-zones) based on Holdridge Life Zone divisions.Most of this is based on undisturbed ecosystems, however.Amundson 2001
27Missing pieces: Below-ground We understand the general processes that limit soil C storage in undisturbed soil reasonably well.We also understand the trends of how land use change influences soil C storage, but need more field measurements.Moving to a larger scale requires modeling.We also need to synthesize this information with the data we have above-ground.
28Land Use Transitions & Soil C From Guo &Gifford 2002agriculture has released 70 Gt of C to the atmosphereWe do know a little bit though... this information is just starting to come together.There’s a lot of uncertainty, and a lot of caveats though. (i.e. Crop to plantation transition depends on species planted)Also, as you can see, our observations are not extensive, especially when you consider that we’re extrapolating to the global level in this paper.
29Uncertainty in Transitions Paul et al. 2002As you can see, here’s another graphic that describes what happens to soil C when agriculture is returned to forest cover. There’s a lot of spread in these numbers... some positive, and some negative.The question is though, does this tell us enough to make predictions at a larger scale? (i.e. will we store a lot more carbon if we convert a bunch of acres into plantation?
30From Guo &Gifford 2002Pasture to PlantationThis type of transition is common in New Zealand, where Pinus radiata plantations are common.
31Missing pieces: Below-ground We understand the general processes that limit soil C storage in undisturbed soil reasonably well.We also understand the trends of how land use change influences soil C storage, but need more field measurements.Moving to a larger scale requires modeling.We also need to synthesize this information with the data we have above-ground.
32Scaling back up: Using models Models have been used to link our small scale mechanistic understanding of carbon cycling to larger scale patterns.Model development needs more work:“Whether models are parameterized by biome or plant life form (or neither), use single or multiple soil layers, or include N and water limitation will all affect predicted outcomes.” (Jackson et al. 2000)
33Soil C modelsUsed primarily to scale up, or to feed in to carbon budget modelsOne such model is the Century Model, a process-based model of soil nutrient dynamics. (Parton et al. 1994).It was created based on agricultural soils
34Missing pieces: Below-ground We understand the general processes that limit soil C storage in undisturbed soil reasonably well.We also understand the trends of how land use change influences soil C storage, but need more field measurements.Moving to a larger scale requires modeling.We also need to synthesize this information with the data we have above-ground.
35Carbon flux over time (from data in Houghton & Hackler 2002) I can make the text bigger and change the colours if you want…
36Land use trendsIn the U.S., much of the carbon sink is due to changing land uses and subtle management effects, such as reduced fire frequency that leads to woody encroachment (Schimel et al. 2001)In Europe, the carbon sink is the result of both land-use changes and increased tree growth due to CO2 fertilization & N-deposition (Schimel et al. 2001)
37Land-use trends II China 1949: new social system established, resulting in rapidly increasing population, economic development and, therefore, forest exploitation1970’s to present: Chinese government has implemented several extensive forest restoration projects (Fang et al. 2001)
38Land-use trends III New Zealand: Increased planting of exotic forests (primarily Pinus radiata) is the biggest land-use change in New Zealand – ha in 1996Organic C in the surface mineral-soil layers is 17-40% lower under plantation forests than pasture, although this may be offset by C-accumulation in the forest floor(Tate et al. 2000)
39Future carbon trends Limitations to the US carbon sink? How long will it last?How much C will it suck out of the atmosphere?What policies could limit or enhance the US carbon sink?Will agricultural abandonment & forest regrowth create another sink somewhere else? Or not?
40Future social trends“Landsat photos showing that China is losing cultivated land to development two and one-half times faster than previously assumed have moved the Politburo into ordering tough new measures.” US Embassy, Beijing, June 1997