Global cropland monthly gross primary production in the year 2000
Croplands cover about 12% of the ice-free terrestrial land surface. Compared with natural ecosystems, croplands have distinct characteristics due to anthropogenic influences. Their global gross primary production (GPP) is not well constrained and estimates vary between 8.2 and 14.2 Pg C yr<sup>...
| Main Authors: | , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2014-07-01
|
| Series: | Biogeosciences |
| Online Access: | http://www.biogeosciences.net/11/3871/2014/bg-11-3871-2014.pdf |
| Summary: | Croplands cover about 12% of the ice-free terrestrial land surface.
Compared with natural ecosystems, croplands have distinct characteristics due
to anthropogenic influences. Their global gross primary production (GPP) is
not well constrained and estimates vary between 8.2 and
14.2 Pg C yr<sup>−1</sup>. We quantified global cropland GPP using a light use
efficiency (LUE) model, employing satellite observations and survey data of
crop types and distribution. A novel step in our analysis was to assign a
maximum light use efficiency estimate (ϵ<sup>*</sup><sub>GPP</sub>) to
each of the 26 different crop types, instead of taking a uniform value as
done in the past. These ϵ<sup>*</sup><sub>GPP</sub> values were
calculated based on flux tower CO<sub>2</sub> exchange measurements and a
literature survey of field studies, and ranged from 1.20 to
2.96 g C MJ<sup>−1</sup>. Global cropland GPP was estimated to be
11.05 Pg C yr<sup>−1</sup> in the year 2000. Maize contributed most to this
(1.55 Pg C yr<sup>−1</sup>), and the continent of Asia contributed most with
38.9% of global cropland GPP. In the continental United States, annual
cropland GPP (1.28 Pg C yr<sup>−1</sup>) was close to values reported previously
(1.24 Pg C yr<sup>−1</sup>) constrained by harvest records, but our estimates of
ϵ<sup>*</sup><sub>GPP</sub> values were considerably higher. Our
results are sensitive to satellite information and survey data on crop type
and extent, but provide a consistent and data-driven approach to generate a
look-up table of ϵ<sup>*</sup><sub>GPP</sub> for the 26 crop types for
potential use in other vegetation models. |
|---|---|
| ISSN: | 1726-4170 1726-4189 |