National Implementation Case Study: China - Soil Carbon: Science, Management and Policy for Multiple Benefits - page 354

Approaches for Soil Carbon
Governance in China

91 Tg C with a farmyard manure incorpor-
ation rate of 200% and 465 Tg C with a
crop residue return rate of 30% combined
with reduced tillage (Xu et al ., 2011).
Moreover, fertilization and water manage-
ment and the optimization of rotation and
cropping systems have also often been
used jointly with the conservation tillage
technique, which may amend the soil's
physical properties, reduce possible soil ero-
sion and thereby improve soil fertility and
SOC content.

Land use and land cover

Land-use/land-cover change is a critical
factor affecting the storage of carbon in ter-
restrial ecosystems. Transformation from
natural woodland, meadow and wetland
to cropland may cause soil carbon losses,
while conversion of cropland to vegetable
fields in China sequestrates SOC due to
the high inputs of fertilizer and manure in
vegetable fields (Zhang et al ., 2006, 2007;
Kong et al ., 2006). In China, vegetable fields
covered only 2.8% of the arable land in 1978,
whereas this figure increased to 16.4% in
2007, according to the China Statistical
Yearbook (2008) (National Bureau of Stat-
istics of China, 2008). This increase has
turned into an important driving factor af-
fecting the sequestration of SOC (Liu et al .,
2012). Conversion of uplands to paddy
fields can also increase soil carbon content.
For example, the acreage of paddy fields in
the Jiangsu Province of China increased by
1.73 million ha (Mha) from 1949 to 1998,
and 17 Tg C was sequestrated in soils (Pan
et al ., 2003).

Forestry activity and pasture
management

Forestry activities such as forestation, re-
forestation, restoration of degraded eco-
systems and establishment of agroforestry
ecosystems are the most effective ap-
proaches to increase carbon sequestration
in the vegetation and soils in China
(Zhang et al ., 2005). The percentages of
forest cover in China increased from
16.55% in 1998 to 18.21% in 2003 (State
Forestry Administration of China, 2005),
which largely benefited the accumula-
tion of carbon in forestry soils. Moreover,
the rapid restoration of the shrub-covered
area also made important contributions to
soil carbon sequestration (Huang et al .,
2010). Fenced-in grazing (the pasture is
fenced into many subpastures during graz-
ing, each grazed for a short period and then
given adequate rest periods for regrowth),
artificial planting of grass, returning farm-
land to grassland, fertilization, irrigation
and grazing management are the main
methods for carbon sequestration in pas-
ture soils. In Inner Mongolia, Tibet and
Xinjiang (China), SOC storage can be in-
creased by 4561 Tg C through reducing graz-
ing pressure, on the assumption that all
degraded grassland (55% grassland in the
area) can be fully recovered, and, utilizing
similar methods, the annual sequestration
rate of SOC under the condition of artifi-
cial planting of grass, returning farmland
to grassland and fenced-in grazing can be
estimated at 25.6, 1.5 and 12.0 Tg C year - 1 ,
respectively (Guo et al ., 2008).

Agricultural management practice

Conservation tillage, fertilization and water
management and the optimization of crop-
ping systems are major approaches for se-
questrating carbon in cropland soils of China.
Conservation tillage is a tillage system that
reduces loss of soil or water relative to con-
ventional tillage (Mannering and Fenster,
1983), and it is usually a combination of re-
duced tillage, no tillage and straw mulching.
Utilizing the DNDC model (denitrification-
decomposition model; for additional infor-
mation on the DNDC model, please refer to Li
et al ., 1994), the carbon sequestration po-
tential (years 2009-2050, with 2008 as the
baseline) for China's paddy soils is estimated at
239 Tg C under the condition of reduced
tillage and 415 Tg C with no tillage, 437 Tg C
with a crop residue return rate of 50%,