Long-term vegetation restoration insignificantly increases deep soil
carbon storage in the Chinese Loess Plateau
Abstract
Vegetation restoration plays an important role in soil carbon storage,
with the relatively lacking information in either the deep soil or the
soil inorganic processes. The study aims to investigate the effect of
returning farmland to the forest on deep soil carbon in the hilly and
gully region of the Chinese Loess Plateau. Four sampling sites were
selected: PO (Platycladus orientalis (Linn.) Franco forest; oriental
arborvitae), PT (Pinus tabulaeformis Carr. Forest; Chinese red pine), AO
(apple orchard) and FL (farmland, as a control treatment). Soil organic
carbon (SOC) and soil inorganic carbon (SIC) content were analysed in
20-m soil profiles, along with the responsible factors. The mean SOC
content slightly increased in the 1-5 m layer in the order FL
< PO =AO < PT (p < 0.05) and in the 5-10 m
layer in the order FL < PO < PT < AO, but
no differences were found in the 0–1 m layer. Compared with FL, the SOC
storages of PO, PT and AO increased by 6.71%, 16.28% and 2.50%,
respectively. SIC content was relatively uniform throughout the profile,
regardless of land-use types. The soil profiles in the study area
presented vast SIC storage that was 8.8–10.2 times higher than SOC
storage. After the 36-yrs implementation of the “Grain for Green”
Project, SOC in 20 m soil profiles insignificantly increased as a cost
of water depletion while SIC did not change. PT is the preferred tree
species for soil carbon sequestration on afforested farmland in this
region.