Combining livestock production information in a process-based vegetation model to reconstruct the history of grassland management
Grassland management type (grazed or mown) and intensity (intensive or extensive) play a crucial role in the greenhouse gas balance and surface energy budget of this biome, both at field scale and at large spatial scale. However, global gridded historical information on grassland management intensit...
| Main Authors: | , , , , , , , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-06-01
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| Series: | Biogeosciences |
| Online Access: | http://www.biogeosciences.net/13/3757/2016/bg-13-3757-2016.pdf |
| Summary: | Grassland management type (grazed or mown) and intensity
(intensive or extensive) play a crucial role in the greenhouse gas balance and surface
energy budget of this biome, both at field scale and at large spatial scale.
However, global gridded historical information on grassland management intensity
is not available. Combining modelled grass-biomass productivity with
statistics of the grass-biomass demand by livestock, we reconstruct gridded
maps of grassland management intensity from 1901 to 2012. These maps include
the minimum area of managed vs. maximum area of unmanaged grasslands
and the fraction of mown vs. grazed area at a resolution of
0.5° by 0.5°. The grass-biomass demand is derived from
a livestock dataset for 2000, extended to cover the period 1901–2012. The
grass-biomass supply (i.e. forage grass from mown grassland and biomass
grazed) is simulated by the process-based model ORCHIDEE-GM driven by
historical climate change, rising CO<sub>2</sub> concentration, and changes in
nitrogen fertilization. The global area of managed grassland obtained in
this study increases from 6.1 × 10<sup>6</sup> km<sup>2</sup> in 1901 to 12.3 × 10<sup>6</sup> km<sup>2</sup> in 2000, although the expansion pathway varies
between different regions. ORCHIDEE-GM also simulated augmentation in
global mean productivity and herbage-use efficiency over managed grassland
during the 20th century, indicating a general intensification of
grassland management at global scale but with regional differences. The
gridded grassland management intensity maps are model dependent because they
depend on modelled productivity. Thus specific attention was given to the
evaluation of modelled productivity against a series of observations from
site-level net primary productivity (NPP) measurements to two global
satellite products of gross primary productivity (GPP) (MODIS-GPP and SIF
data). Generally, ORCHIDEE-GM captures the spatial pattern, seasonal cycle,
and interannual variability of grassland productivity at global scale well
and thus is appropriate for global applications presented here. |
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| ISSN: | 1726-4170 1726-4189 |