| 其他摘要 | Vegetation restoration based mainly on conversion of cropland to forest and
grassland was an important ecological construction project in loess hilly region,
which not only changed the land use and topsoil carbon sequestration status in
the region, but also affected the deep layer soil carbon storage as well as
ecosystem carbon cycle. At present only a few research were carried out on deep
soil organic carbon. The accumulation process and sequestration mechanism is
unclear, which may lead to bias estimates of soil carbon storage. To meet the
requirement of soil organic carbon research and assessment of the benefits of
soil carbon sequestration on the Loess Plateau, through field investigation and
sampling, using
13 C isotopes method, this paper was designed to explore deep
soil organic carbon storage, its distribution in profile, accumulation dynamics
and its response to LUCC under different land use types and land use years. The
sources of deep soil organic carbon were also discriminated. The results could
provide scientific basis for estimating regional soil carbon storage and
certification of carbon sequestration in the Loess Plateau. The main conclusions
were as follows:
(1) The distribution of soil organic carbon storage in soil profile under
different vegetation types in the loess hilly region was: the storage decreased
significantly as the depth increased and ranged from 5.10 to 12.85 t∙hm -2 in the
0–100 cm layer; but the storage just varied from 5.12 to 6.13 t∙hm -2 , and there
were only slight fluctuations among different soil layers.
(2) In 0-100 cm soil profile, the organic carbon storage decreased
significantly with the increase of soil depth. However, in deep soil, the organic
carbon storage had a slight fluctuation. The total organic carbon storage in
100-400 cm soil profile was considerably high, accounting for approximately 60% of that in 0-400 cm soil profile. The organic carbon storage in 80-100 cm
soil layer had a significant linear correlation with that in 100-200 cm and
200-400 cm soil layers, and among the organic carbon storages in the five layers
in 0-100 cm soil profile, the organic carbon storage in 80-100 cm soil layer had
the strongest correlation with that in 100-400 cm soil profile, being able to be
used to estimate the soil organic carbon storage in deep soil in this region.
(3) The organic carbon storage in 0-20 cm soil layers in the three types of
revegetation lands was significantly higher than that in slope croplands, but the
organic carbon storage in deep soil had no significant difference among the land
use types. The organic carbon storage in deep soil increased with the increasing
years of revegetation. In R. pseudoacacia woodlands and C. korshinskii shrub
lands, the average increasing rate of the organic carbon storage in 100-400 cm
soil layer was 0.14 and 0.19 t∙hm -2 ∙a -1 , respectively, which was comparable to
that in the 0-100 cm soil layer. It was suggested that in the estimation of the soil
carbon sequestration effect of revegetation in the hilly Loess Plateau region, the
organic carbon accumulation in deep soil should be taken into consideration.
Otherwise, the effect of revegetation on soil carbon sequestration could be
significantly underestimated.
(4) The δ 13 C value of soil organic carbon increased as the depth increased
in the soil profile of R. pseudoacacia woodlands, whereas in slope croplands,
theδ 13 C value had a slight fluctuation. The proportion of organic carbon that
come from the plant residues of R. pseudoacacia woodlands in 0-20 cm was
69.6%, which was much higher than the proportion that between 7.0~17.0% in
100-300 cm soil layer.
KEY WORDS: Deep soil; SOC storage; SOC sources; stable C isotope; hilly
Loess Plateau |
修改评论