Climate Change and Dryland Agricultural Ecosystem Management

for example, the family, genus and species of plant communities have significantly increased, a total
of 85 species were identified during this study, belonging to 68 genera and 35 families during 8 years.
Species frequently replaced in the restore process, Annual and biennial xerophytes’ weed (A) was
replaced by the other perennial hygrophilous herb, the important value (IV) of some pioneer tree
increased, such as sheepberry, Betula platyphylla Suk. and Populus davidiana Dode., they gradually
become the constructive species. Community structure showed supraterraneous stratification when
trees and shrubs appeared in community. The height of herb and shrub did not greatly change, while
the tree’s average height increased from 43.5cm in 2002 to 310.3cm in 2008. Herb layer density
increased first then decreased, the density changes of shrub showed bimodal curve, the tree layer
density increased from 0.04plant/m2 to 1.38plant/m2. According to the plant life-form, we divided the
vegetation community into seven functional groups: Annual and biennial weed (A), Perennial forbs
(PF), Perennial grasses (PG), Legume plants (LP), Shrubs or semi-shrubs (S), Arbors (AR) and Lianas
(L). Annual and biennial weed (A) and Perennial forbs (PF) accounted for a large proportion in the
early stage of the restoration process, then the woody plants gradually increased in middle-later period.
While the kinds of tree-layer (TL) is relative single since artificial rearing, species richness and
diversity was far lower than shrub and herbaceous layer. With the restoration time going, the total
community diversity increased, the changes of vegetation community Patrick’s index,
Shannon-Wienner’s index and Simpson’s index in spatial structure as follows: Herb layer(HL)>shrub
layer(SL)>tree layer(TL), but the trend of Pielou’s index was opposite. In the different natural
restoration stage, the soil properties were improved significantly. The average soil bulk density (SBD)
was only 0.86g±0.02/cm3, total porosity of the soil is higher than 53 %. Soil water content (SWC)
increased from 16.1±1.59% in early stage to 38.91±5.91% in later stage of the restoration process, Soil
organic carbon (SOC) and total nitrogen (TN) contents gradually increased. SOC and TN varied
within a range of 4.66±0.37g/kg~70.65±14.06g/kg、3.13±0.21g/kg~5.85±0.70g/kg respectively,
SOC and Total N in surface soil were larger than the deep.
CONCLUSION
There is no doubt that climate change and human interference have effect on plant community, but
strong plasticity of the plant under artificial rearing made them restore themselves quickly. We found
that, under removing human interference, the degraded forest has experienced secondary succession
process that from the herb community to shrub community finally reached woodland community after
8 years exclusion measures, When the vegetation restored to the early pioneer tree-shrub mixed forest
stage, the community composition, structural characteristics and diversity were similar to the local
mature secondary vegetation, and this community type showed a better eco-hydrological effects of
soil at this stage. However, the restore results have some certain specificity and uncertainty in a short
time, it still needs a longer time to return to the top phase of the complex species composition.
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