Difference between revisions of "Carbon cycle and natural vegetation"

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|KeyReference=Sitch et al., 2003;
 
|KeyReference=Sitch et al., 2003;
 
|Reference=Van Minnen et al., 2008; Houghton, 2010; Müller et al., 2007; Ballantyne et al., 2012; Van Minnen et al., 2009; Gerten et al., 2004; Bondeau et al., 2007; Klein Goldewijk et al., 1994; Van Minnen et al., 2000;
 
|Reference=Van Minnen et al., 2008; Houghton, 2010; Müller et al., 2007; Ballantyne et al., 2012; Van Minnen et al., 2009; Gerten et al., 2004; Bondeau et al., 2007; Klein Goldewijk et al., 1994; Van Minnen et al., 2000;
|InputVar=Temperature - grid; Precipitation - grid; Nr of wet days - grid; Cloudiness - grid; CO2 concentration; Timber use fraction; Timber harvest fraction - grid; Land cover, land use - grid; Irrigation water supply - grid; Forest management - grid;  
+
|InputVar=Temperature - grid; Precipitation - grid; Nr of wet days - grid; Cloudiness - grid; CO2 concentration; Timber use fraction; Timber harvest fraction - grid; Land cover, land use - grid; Irrigation water supply - grid; Forest management - grid; Harvesting efficiency;  
 
|Parameter=Soil properties - grid;
 
|Parameter=Soil properties - grid;
 
|OutputVar=Potential natural vegetation - grid;NEP (net ecosystem production) - grid; Terrestrial CO2 emission - grid; Carbon pools in vegetation, soil and timber - grid; NPP (net primary production) - grid; Soil respiration - grid
 
|OutputVar=Potential natural vegetation - grid;NEP (net ecosystem production) - grid; Terrestrial CO2 emission - grid; Carbon pools in vegetation, soil and timber - grid; NPP (net primary production) - grid; Soil respiration - grid

Revision as of 13:57, 26 March 2014

Component is implemented in:
  • LPJmL model (version 3)
Components:
Related IMAGE components
Models/Databases
Key publications
References
Carbon cycle and natural vegetation module of LPJmL, in IMAGE 3.0
Flowchart Carbon cycle and natural vegetation. See also the Input/Output Table on the introduction page.

Key policy issues

  • What is the role of the terrestrial biosphere in the global carbon cycle, how will it change in time as a result of climate and land-use change?
  • To what extent can the terrestrial biosphere contribute to reducing the accumulation of CO2 in the atmosphere and what are viable mechanisms?
  • What opportunities exist to reduce land-use related carbon emissions (e.g. REDD) and even enhance the carbon uptake through the establishment of new forests.
  • What are the contributions of land-use change, climate change and CO2 fertilization on the future carbon cycle and how can these be considered in climate policies?

Introduction

The terrestrial biosphere plays an important role in global and regional carbon (C) cycles and, thus, also in the climate system. Large amounts of carbon, between 2000 and 3000 PgC, are stored in the vegetation and soil components. Land conversions, such as deforestation, have considerably contributed to the increase in atmospheric carbon dioxide over the past centuries (Van Minnen et al., 2009; Houghton, 2010) and are projected to continue to do so in the future (Müller et al., 2007). At teh same time the terrestrial biosphere currently absorbs about 30% of the emitted CO2 (Ballantyne et al., 2012), and a number of options exists to maintain or even enhance this sink; for example, through protecting existing forests and/or establishing new ones (Van Minnen et al., 2008).

Processes

The CO2 uptake by and release from the terrestrial biosphere is determined by a number of processes that are sensitive to environmental conditions, such as climate, atmospheric CO2 concentration and moisture availability. Hence, even if land cover and land use would remain unchanged, the strength of the current net sink may change, over time, in response to changes in those conditions. Basic processes include photosynthesis, plant and soil respiration, transpiration, carbon allocation and turnover, and disturbances, such as fires. Photosynthesis is the process where CO2 is taken up from the atmosphere and converted into organic carbon compounds. This conversion of CO2 is called gross primary production (GPP). The sequestered carbon is partially needed for plant maintenance and growth (autotrophic or plant respiration), while the remainder (net primary production NPP) is incorporated in new tissues in various parts of plants, forming live biomass carbon pools. The ultimate fate of these plant parts (incl. leaf fall and mortality) cause the stored carbon to be transferred to various carbon pools, such as the soil and the atmosphere. From the soil pools, through processes of soil respiration, CO2 is also emitted back into the atmosphere.

Modelling

Terrestrial carbon-cycle and vegetation models contribute to a better understanding of the dynamics of the terrestrial biosphere related to the underlying processes and their relation to the Hydrological cycle and Agricultural economy and forestry. The LPJmL model (Sitch et al., 2003; Gerten et al., 2004; Bondeau et al., 2007) replaces the earlier IMAGE-2 carbon cycle and vegetation model (Klein Goldewijk et al., 1994; Van Minnen et al., 2000). Here, we give a general overview of the LPJmL model in the IMAGE context, with a focus on carbon and vegetation dynamics. For a detailed description of the IMAGE-Natural vegetation and carbon cycle model and a sensitivity analysis, see (Müller et al., 2013[1]).

  1. Müller et al.,b (unpublished)

Input/Output Table

Input Carbon cycle and natural vegetation component

IMAGE model drivers and variablesDescriptionSource
Cloudiness - grid (historical data) Percentage of cloudiness per month; assumed constant after the historical period CRU database
Number of wet days - grid (historical data) Number of days with a rain event, per month; assumed constant after the historical period CRU database
CO2 concentration Atmospheric CO2 concentration. Atmospheric composition and climate
Forest management type - grid Forest management type: clear cut, selective logging, forest plantation or additional deforestation. Forest management
Irrigation water supply - grid Water supplied to irrigated fields; equal to irrigation water withdrawal minus water lost during transport, depending on the conveyance efficiency. Water
Land cover, land use - grid Multi-dimensional map describing all aspects of land cover and land use per grid cell, such as type of natural vegetation, crop and grass fraction, crop management, fertiliser and manure input, livestock density. Land cover and land use
Precipitation - grid Monthly total precipitation. Atmospheric composition and climate
Temperature - grid Monthly average temperature. Atmospheric composition and climate
Timber use fraction Fractions of harvested timber entering the fast-decaying timber pool, the slow-decaying timber pool, or burnt as traditional biofuels. Forest management
External datasetsDescriptionSource
Soil properties - grid Soil properties that have an effect on vegetation growth and hydrology. These characteristics differ between soil types. Relevant characteristics are soil texture and depth and water holding capacity HWSD database

Output Carbon cycle and natural vegetation component

IMAGE model variablesDescriptionUse
Carbon pools in soil and timber - grid Carbon biomass in three soil pools (litter, humus and charcoal) and two timber pools (slow decaying, and fast decaying).
Potential natural vegetation - grid Potential natural vegetation type/biome, based on distribution of plant functional types.
Land-use CO2 emissions - grid Land-use CO2 emissions from deforestation, wood harvest, agricultural harvest, bioenergy plantations and timber decay.
NEP (net ecosystem production) - grid Net natural exchange of CO2 between biosphere and atmosphere (NPP minus soil respiration), excluding human induced fluxes such as decay of wood products.
Carbon pools in vegetation - grid Carbon pools in leaves, stems, branches and roots).
NPP (net primary production) - grid CO2 sequestered by plants and incorporated in new tissue in plant carbon pools.
Soil respiration - grid CO2 release from soils into the atmosphere due to the decay of soil carbon pools and respiration of soil organisms. Final output

Parts of Carbon cycle and natural vegetation

  1. Introduction page
  2. Model description
  3. Policy issues
  4. Data, uncertainty and limitations
  5. Overview of references