Ecosystem carbon storage following different approaches to grassland
restoration in south-eastern Horqin Sandy Land, northern China
Abstract
Global climate change and extensive socio-economic development together
decrease ground cover in the semi-arid sandy grasslands of Horqin
district in northern China and thereby increase the direct exposure of
surface soil to erosion by strong winds—a process that ultimately
converts the grassland into a sandy desert. Three ways to restore such
degraded lands through afforestation were evaluated in terms of total
carbon stored in the restored ecosystems compared to that in the
control. Total carbon comprised that stored in the biomass of trees,
herbs, and standing litter and in soil (up to a depth of 100 cm). The
three restoration treatments were (1) enclosing the grassland within a
shelter belt of Populus × beijingensis, (2) afforesting small but
well-distributed patches within the grassland using Pinus sylvestris
var. mongolica, and (3) similar afforestation using Ulmus pumila. Total
ecosystem carbon storage increased significantly in all the three
treatments over more than 20 years; at the end of that period, total
ecosystem carbon was maximum (104.29 t/ha) in the grassland enclosed by
the forest belt, followed, in that order, by afforestation with P.
sylvestris (102.96 t/ha), that with U. pumila (92.24 t/ha), and the
control (24.48 t/ha). The structure of the plant community created by
these treatments is different from that found in natural stands of
forest and in grasslands without trees or shrubs, and all the three
treatments are suitable for restoring the moderately desertified sandy
grasslands in south-eastern Horqin, northern China, depending on the
availability of water and soil nutrients.