IN 1998, INTERNATIONAL AND SPACE AGENCIES INTERESTED IN SYSTEMATIC GLOBAL OBSERVATIONS ESTABLISHED THE INTEGRATED GLOBAL OBSERVING STRATEGY PARTNERSHIP, IGOS-P (www.igospartners.org). IGOS-P has developed 'Observation themes' each consisting of a set of related observations required to deal with a particular aspect of the Earth system. The definition of these themes is carried out in collaboration with relevant international programmes and groups.
In response to growing interest in terrestrial carbon the IGOS-P requested that the Global Terrestrial Observing System (GTOS) prepare a proposal for a Terrestrial Carbon Observation (TCO) theme. After circulation in the international scientific and policy communities a revised TCO proposal (TOPC, 1999) was submitted to IGOS-P at its annual meeting in November, 1999 where the following decisions were made:
The TCO observation concept is based on a 'top-down' and 'bottom-up' approach, supported by satellite and in situ observations and by a range of models of key environmental components (atmosphere, vegetation, soils and their interactions) involved in the terrestrial component of the carbon cycle.
During the preparation of the theme report it became evident that the in situ component is more complex and much less organized at the global level than the satellite component. To accelerate the preparations for TCO implementation, GTOS with IGBP decided to hold a workshop specifically addressing in situ data issues. The meeting was held on 5-8 June 2001 in Frascati, Italy with local support provided by FAO and the GTOS Secretariat. The objectives of the workshop were to:
1. assess the capacity and readiness of existing key in situ observation and analysis components for a TCO system;For this workshop, in situ data/products were broadly defined as data or products obtained through non-remote sensing means (i.e. ground measurements). The exceptions are resource inventories (e.g. forest) that are often produced through air photo interpretation with variable field sampling, and trace gas composition measurements that can be made on towers or from aircraft as well as at the surface.2. analyse the comprehensiveness of geographic (continents, regions) and thematic (input data to information outputs) coverage of existing components;
3. identify gaps and discuss possible approaches to filling these gaps to meet TCO requirements;
4. assess the feasibility of, and steps involved in, the preparation of in situ data sets needed to complement satellite observations;
5. prepare a meeting report containing the elements for a provisional in situ TCO implementation plan.
The participants represented programmes that are global, continental, regional, or national in scope and are concerned with carbon-related observations. The following sections of this report summarize the priority actions identified by the participants:
Chapter 2 |
actions to move TCO forward; |
Chapter 3 |
general review of in situ data and their roles in
TCO; |
Chapter 4 |
point in situ data and products; |
Chapter 5 |
gridded in situ data and products; |
Chapter 6 |
data and information management; |
Appendix III |
detailed information on national carbon related data
sets; |
Appendix IV |
details on other terrestrial carbon data acquisition
programmes, networks, and data products. |
The major goals for TCO are:
1. by 2005, demonstrate the capability to estimate annual net land-atmosphere fluxes at a sub-continental scale (107 km2) with an accuracy of +/- 30% globally, and at a regional scale (106 km2) over areas selected for specific campaigns with similar or better accuracy;
2. by 2008, improve the performance to better spatial resolution (106 km2 globally) and an increased accuracy (+/- 20%);
3. In each case, produce flux emission estimate maps with the highest spatial resolution enabled by the available satellite-derived and other input products.
Meeting these goals will also generate early valuable results, and serve as a mechanism for the further evolution of TCO. A design team has been established by GTOS to prepare an implementation plan. TCO will rely on the collaboration of agencies, programmes, and projects that share interest in the terrestrial carbon cycle. Current and planned regional studies (the Amazon, in Europe, North America, Siberia, etc.) will be important for the progress of TCO. The design team is also collaborating in the preparation of the Integrated Global Carbon Observation (IGCO) theme to ensure the integration of terrestrial, atmospheric, and ocean components.
Table 1. Observation requirements for bottom-up approach*
Variable |
Type (a) |
Spatial (b) |
Temporal (c) |
Method (d) |
Comments |
1. DRIVING VARIABLES, GRIDDED (for model
application/upscaling, required at every grid point) |
|||||
ATMOSPHERE |
|
|
|
|
|
Air temperature |
1 |
3 |
1,6 |
1,2,3 |
daily maximum, minimum, mean |
Precipitation |
1 |
3 |
1,6 |
1,2,3 |
|
Photosynthetically active radiation |
1 |
3 |
1,6 |
1,2,3 |
|
Relative humidity |
1 |
3 |
1,6 |
1,2,3 |
|
Wind speed |
1 |
3 |
1,6 |
1,2,3 |
|
Net radiation |
1 |
3 |
1,6 |
1,2,3 |
|
Snow water equivalent |
1 |
3 |
1,6 |
1,2,3 |
|
Aerosols |
1 |
3 |
1,6 |
1,2,3 |
for atmospheric corrections of optical data |
Integrated atmospheric water vapour |
1 |
1 |
6 |
1,2,3 |
for atmospheric corrections of optical data |
ECOSYSTEM |
|||||
Vegetation cover class |
2 |
1 |
4 |
3 |
physiognomic classes, dominant species |
Biota biomass |
2 |
1 |
4 |
3 |
may be used to drive decomposition models |
Soil moisture |
3 |
1 |
1 |
2,3 |
|
Leaf area index |
2 |
1 |
4 |
3 |
|
Foliage nitrogen |
2 |
1 |
4 |
3 |
needed to drive decomposition rates |
Chlorophyll |
2 |
1 |
4 |
3 |
to drive canopy photosynthesis in some models |
Natural disturbance history |
1,2 |
1 |
4 |
1,4 |
includes biomass burning and insect-induced
mortality |
Management history |
1,2 |
1 |
4 |
4 |
includes forest harvest, thinning, fertilization,
etc. |
Topography |
2 |
1 |
3 |
3, 4 |
influences radiation and surface water |
2. CALIBRATION/VALIDATION VARIABLES, POINT (required at
selected sites) |
|||||
ATMOSPHERE |
|||||
Air temperature |
1 |
2 |
6 |
1 |
15 to 60 minute averages (continuous) |
Precipitation |
1 |
2 |
6 |
1 |
15 to 60 minute averages (continuous) |
Solar radiation |
1 |
2 |
6 |
1 |
15 to 60 minute averages (continuous) |
Relative humidity |
1 |
2 |
6 |
1 |
15 to 60 minute averages (continuous) |
Wind speed |
1 |
2 |
6 |
1 |
15 to 60 minute averages (continuous) |
Net radiation |
1 |
2 |
6 |
1 |
15 to 60 minute averages (continuous) |
CO2 concentration profile |
1 |
2 |
6 |
1 |
15 to 60 minute averages (continuous) |
Integrated atmospheric water vapour |
1 |
2 |
6 |
1 |
for atmospheric corrections of optical data |
Snow water equivalent |
1 |
2 |
1,6 |
1 |
15 to 60 minute averages (continuous) |
Aerosols |
1 |
2 |
1,6 |
1 |
15 to 60 minute averages (continuous; for atmospheric
corrections) |
ECOSYSTEM |
|||||
SITE |
|
|
|
|
|
Natural disturbance history |
1,2 |
2 |
4 |
1,4 |
includes fires and insect-induced mortality |
Management history |
1,2 |
2 |
4 |
4 |
includes harvest, thinning, fertilization, etc. |
Topography |
2 |
2 |
3 |
3, 4 |
influences radiation, and water fields |
Spatial pattern |
2 |
1,2 |
3 |
3, 4 |
may assist spatial scaling |
VEGETATION |
|||||
Vegetation cover class |
2 |
2 |
2 |
1 |
physiognomic classes, dominant species |
Root carbon |
2 |
2 |
2 |
1 |
coarse and fine |
Above-ground biomass |
2 |
2 |
2 |
1 |
stem, branch, foliage |
Leaf area index |
2 |
2 |
4 |
1 |
|
Foliage nitrogen |
2 |
2 |
4 |
1 |
used for canopy photosynthesis modelling |
SOIL |
|||||
Biota carbon and nitrogen |
2 |
2 |
4 |
1 |
may be used to drive decomposition models |
Biota biomass |
2 |
2 |
4 |
1 |
may be used to drive decomposition models |
Temperature profile |
1,2 |
2 |
4 |
1,2 |
profiles are useful as a driver and for process
studies |
Maximum thaw depth |
1,2 |
2 |
4 |
1,2 |
critical for climate impact on permafrost-affected
areas |
Thermal conductance |
2 |
2 |
3 |
1, 2 |
to estimate heat transfer and heterotrophic
respiration |
Thermal diffusivity |
2 |
2 |
3 |
1, 2 |
related to thermal conductance but needs heat capacity
information |
Soil moisture |
1,2 |
2 |
5 |
1, 2 |
affects heat transfer and decomposition |
Hydraulic properties |
2 |
2 |
3 |
1, 2 |
for vertical and horizontal water exchange |
Ground water table depth |
2 |
1,2 |
4,5 |
1,2 |
influences wetland dynamics |
Carbon content (organic & inorganic) |
2 |
2 |
3 |
1 |
directly affects heterotrophic respiration |
Carbon age |
2 |
2 |
3 |
1 |
needed to improve Rh calculation |
Nitrogen and phosphorus content |
2 |
2 |
3 |
1 |
affects gross primary productivity |
Bulk density |
2 |
2 |
3 |
1 |
needed for diffusivity estimation |
Sand and clay fraction (percentage) |
2 |
2 |
3 |
1 |
|
pH |
2 |
2 |
3 |
1 |
important limitation to growth and soil biology |
Macro & micro nutrients |
2 |
2 |
3 |
1 |
these processes affect plant nutrient uptake |
Microbial biomass |
2 |
2 |
3 |
1 |
affects decomposition |
PHYSIOLOGY |
|||||
Foliage nitrogen |
2 |
2 |
2 |
1 |
needed to drive decomposition rates |
Foliage lignin |
2 |
2 |
2 |
1 |
needed to drive decomposition rates |
Chlorophyll |
2 |
2 |
2 |
1 |
needed to drive canopy photosynthesis in some models |
Rubisco |
2 |
2 |
2 |
1 |
needed to drive canopy photosynthesis in some models |
FLUXES |
|||||
Carbon fluxes (above & near ground) |
3 |
2 |
6 |
1 |
critical for model validation |
Above-ground NPP |
3 |
2 |
4 |
1 |
carbon storage flux |
Below-ground NPP |
3 |
2 |
4 |
1 |
carbon storage flux |
Litterfall nitrogen, phosphorus |
2 |
2 |
2 |
1 |
carbon flux to soil & litterfall nutrients and
carbon |
indicate nutrient availability |
|
|
|
|
|
Hydrogen and ET (above stand) |
3 |
2 |
6 |
1 |
important for carbon flux estimation |
CH4 |
3 |
2 |
6 |
1 |
important for wetlands |
VOC |
3 |
2 |
6 |
1 |
can be significant in total carbon budget |
DOC |
3 |
2 |
2 |
1 |
carbon exchange can affect stocks and processes |
Heterotrophic respiration rate |
3 |
2 |
4 |
1 |
needed to validate NPP and NEP components |
DOC = dissolved organic carbon, VOC = volatile organic
carbon |
|||||
a: 1 = external forcing variable; 2 = internal status
variable; 3 = output variable |
|||||
b: 1 = gridded with a resolution of 1 km or better; 2 = one or
more sites for each land cover class; 3 = gridded with a resolution of 0.5-1
degree or better |
|||||
c: 1, since industrialisation with desirable frequency; 2,
periodical measurement once every 5-10 years; 3, one-time measurement; 4:
multiple-year continuous measurement; 5, daily in calibrations years; 6,
continuous |
|||||
d: 1 = site measurement (including characterisation of its
spatial heterogeneity as appropriate); 2 = modelling; 3 = remote sensing; 4 =
existing survey or inventory |
* From: FAO, 2002b