| 其他摘要 | Soil infiltration and runoff generation process are important research topics in the
hilly Loess Plateau region. Biological soil crusts (biocrusts) were extensively developed on
the surface of revegetated lands after the implementation of the “Grain for Green” Project
and became the important influence factors on soil water infiltration and runoff process.
The distribution pattern of vegetation and biocrusts patches were investigated in six
successive rainfall zones ranging from 250 mm to 550 mm in the Loess Plateau region in
the study. The effects of different type of biocrusts and plant species on soil infiltration
were measured and the mechanism of infiltration differences was analyzed. Then, the
effect of biocrusts and vegetation patches were implored by simulated rainfall experiment
so as to clear the runoff source-sink relationship between biocrusts and vegetation patches.
In addation, the effect of biocrusts types, plant species, biocrust and vegetation plaque area
ratio, distribution patterns, and intensity of precipitation, slope gradient and length were
also implored. The results were as follows.
1) Biocrusts were developed in extensively in the revegetated lands in all of the
rainfall zons investigated. The distribution pattern of vascular plants and biocrusts
patches showed a mosaic pattern across the six rainfall gradients. Biocrusts were
often distributed continuously within each site, while vascular plants often existed in
patchys. Coverage of vascular plants and biocrusts has a significant negative correlation
between the 250-550mm rainfall zones. Total percentage cover of biocrusts of different the
rainfall range investigated were significant varied, however, no significant difference was
observed in the community composition of biocrust along this gradients.
2) As respect to the influences on soil infiltratin, significant differences were
found between biocrusts’ types as well as plants species. Generally, the soil under
plants with tap roots exhibited higher stable infiltration rates than bare soil, while, the stable infiltration rates of soil under plants with fibrous roots did not showed
significant difference compared with bare soil. Overall, infiltration potential of soils
under varscular plants was higher than soils with biocrusts. Soil water content within the
top 10 cm soil were siginificant influenced by the biocover after rain.
3) A “source-sink” relationship of runoff between biolcrusts and vegetation
patches was observed in the study. Runoff was increased for the present of biocrusts
during a rainfall event, thus biocrusts worked as a "source" of runoff on the
revegated slopes, while vegetation as "sinks", which slowing the runoff generation.
Generally, the amount of runoff from the revegated slopes with biocrusts developed
may increased along with the relative ratio between biocrusts and plant stem base.
Biocrust played a positive role in the rainfall - runoff ecological processes, which can be
regarded as the "source" landscape. However, the vegetation canopy interception rainfall
and resulted in a reduced runoff amount, both the above and below ground parts of
varscular plants played a negative role in the runoff processes, which can be considered as
a "sink" landscape.
4) Rain intensity significantly affected the source - sink relationship between
biocrust - vegetation patches. In addition, the length of the slope was an impact factor
during the process. The amount of runoff showed increase trend when the length was
bellow eight meters, however, the amount of runoff may be decreased when the length
of the slope was longer than eight meters in the study. Vegetation patterns (random,
striped, aggregation) and slope (16 °, 25 °) have no significant effect on biological crust -
the vegetation runoff source - sink relationship, but the runoff volume exhibit aggregative
pattern > random pattern > trend stripe pattern.
Key words: loess plateau, biological soil crusts, mosaic distribution, infiltration,
source-sink relationship |
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