Moderate topsoil erosion rates constrain the magnitude of the erosion-induced carbon sink and agricultural productivity losses on the Chinese Loess Plateau
Despite a multitude of studies, overall erosion rates as well as the contribution of different erosion processes on Chinese Loess Plateau (CLP) remain uncertain, which hampers a correct assessment of the impact of soil erosion on carbon and nutrient cycling as well as on crop productivity. In this p...
Main Authors: | , , , |
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Format: | Article |
Language: | English |
Published: |
Copernicus Publications
2016-08-01
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Series: | Biogeosciences |
Online Access: | http://www.biogeosciences.net/13/4735/2016/bg-13-4735-2016.pdf |
Summary: | Despite a multitude of studies, overall erosion rates as well as the
contribution of different erosion processes on Chinese Loess Plateau (CLP)
remain uncertain, which hampers a correct assessment of the impact of soil
erosion on carbon and nutrient cycling as well as on crop productivity. In
this paper we used a novel approach, based on field evidence, to reassess
erosion rates on the CLP before and after conservation measures were
implemented (1950 vs. 2005). We found that current average topsoil erosion
rates are 3 to 9 times lower than earlier estimates suggested. Under 2005
conditions, more sediment was produced by non-topsoil erosion (gully erosion
(0.23 ± 0.28 Gt yr<sup>−1</sup>) and landsliding
(0.28 ± 0.23 Gt yr<sup>−1</sup>) combined) than by topsoil erosion
(ca. 0.30 ± 0.08 Gt yr<sup>−1</sup>). Overall, these erosion processes
mobilized ca. 4.77 ± 1.96 Tg yr<sup>−1</sup> of soil organic carbon (SOC):
the latter number sets the maximum magnitude of the erosion-induced carbon
sink, which is ca. 4 times lower than one other recent estimate suggests.
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The programs implemented from the 1950s onwards reduced topsoil erosion from
0.51 ± 0.13 to 0.30 ± 0.08 Gt yr<sup>−1</sup> while SOC mobilization
was reduced from 7.63 ± 3.52 to 4.77 ± 1.96 Tg C yr<sup>−1</sup>.
Conservation efforts and reservoir construction have disrupted the
equilibrium that previously existed between sediment and SOC mobilization on
the one hand and sediment and SOC export to the Bohai sea on the other hand:
nowadays, most eroded sediments and carbon are stored on land.
<br><br>
Despite the fact that average topsoil losses on the CLP are still relatively
high, a major increase in agricultural productivity has occurred since 1980.
Fertilizer application rates nowadays more than compensate for the nutrient
losses by (topsoil) erosion: this was likely not the case before the
dramatic rise of fertilizer use that started around 1980. Hence, erosion is
currently not a direct threat to agricultural productivity on the CLP but
the long-term effects of erosion on soil quality remain important. |
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ISSN: | 1726-4170 1726-4189 |