Vegetation recovery patterns of abandoned croplands in the grasslands of
northern China
Abstract
Passive restoration (without any intervention) has been proposed as an
effective strategy for degraded cropland restoration. However, whether
the vegetation in abandoned cropland can change towards the desired
state and the time needed to reach a stable state are still uncertain.
We investigated three abandoned croplands with different recovery times
(5, 15 and 20 years) and one natural grassland in each of two different
types of grassland (desert steppe and typical steppe) in the
agro-pastoral ecotone of northern China to assess the restoration
potential of abandoned cultivated grassland. Above- and below-ground
productivity as well as species biodiversity increased gradually with
increasing recovery time. After 20 years of restoration there was no
significant difference between abandoned cropland and natural grassland
in the typical grassland site, but above- and below-ground productivity
and species biodiversity were still lower in abandoned cropland in the
desert steppe site. At the beginning of restoration, the communities
were dominated mainly by annual species, especially in the desert
steppe. As recovery time increased, the biomass and richness of
perennial grasses and forbs increased significantly and replaced annual
species as the dominant species. In both desert steppe and typical
grassland, species similarity between restored and natural grassland
increased over time, suggesting that previously cultivated grassland
recovered towards the desired state. Our results indicate that 20 years
was long enough for the restoration of previously cultivated grassland
in the typical steppe, but more time may be needed in the desert steppe.