| 其他摘要 | The ecological environment has been greatly improved since the large-scale soil
and water conservation project in the Loess Plateau. Vegetation restoration can not
only maintain soil and water, reduce soil erosion, but also improve soil nutrient status.
Characteristics of soil ecosystem after returning farmland to forest, is the basis for
further understanding of the function of ecological system, which has important
theoretical and practical significance to predict response of soil function to
environment.
To assess the effects of vegetation types on soil development, the basic
physicochemical properties, microbial biomass carbon (MBC) and nitrogen (MBN),
and the number of bacteria and fungi of soils were measured. We assessed whether
land-use types or soil chemical properties are the primary drivers of soil microbial
community composition, and how changes in one part of the ecosystem affect another.
We applied Ion Torrent sequencing to the bacterial and fungal communities of five
different vegetation types in the Loess Plateau of China, including a secondary natural
oak forest, a non-typical natural forest of oriental arborvitae, a natural shrub land, a
planted forest of black locust, and a plot of unforested bare land. We found that (1)
soil properties improved with the presence of vegetation, compared with the
abandoned bare land, and that there were differences in the physicochemical
properties of soil from the different land-use types. Soils from the bare land and black
locust forest yielded higher pH values than the natural forests, and the overall trend of soil quality was: natural forest > plantation > bare land. This indicated that vegetation
coverage, especially natural types, has a beneficial effect on soil nutrient conditions
and soil pH. (2) Similar to the trend of the other soil parameters, both MBC and MBN
were highest in the oak forest and shrub land and lowest in the bare land and black
locust forest. These two indices (MBC and MBN) were also strongly correlated with
specific soil properties (soil organic carbon, r 2 = 0.725, total nitrogen, r 2 = 0.736, and
phosphorus, r 2 = 0.775; P < 0.001), suggesting that vegetation types and soil
properties influence microbial biomass. Thus, microbial biomass can be used to assess
soil trophic status and which were lower in oligotrophic soils on the Loess Plateau of
China. In our study area, the soil was alkaline (pH 8.18–8.48), and the MBC/MBN
ratio was ~6, indicating that actinomycetes were dominant, possibly facilitated by the
alkaline soil conditions. (3) Bare land harbored the lowest abundance of bacteria, and
the abundance of fungi in the black locust was lower than that in the oak forest. The
abundance of bacteria exhibited a strong relationship with specific soil properties and
was positively correlated with C/N ratio (r 2 = 0.754, P < 0.001), soil organic carbon
(r 2 = 0.636, P < 0.05), total nitrogen (r 2 = 0.611, P < 0.05), and phosphorus (r 2 = 0.775,
P < 0.05), and negatively correlated with pH (r 2 = 0.761, P < 0.001). In contrast, the
abundance of fungi was only correlated with soil pH, thus confirming previous reports
that bacteria and fungi respond to different environmental factors. (4) Dominant
bacterial phyla consisted of Proteobacteria (42.35%), Actinobacteria (15.61%),
Acidobacteria (13.32%), Bacteroidetes (8.43%), and Gemmatimonadetes (6.0%). The
dominant fungi phyla were Ascomycota (40.39%), Basidiomycota (38.01%), and
Zygomycota (16.86%). The results of Canonical Correspondence Analysis (CCA) and
Redundancy Analysis (RDA) based on land-use types displayed groups according to
the land-use types. Furthermore, the bacterial communities were mainly organized by
soil organic carbon (SOC). The fungal communities were mainly related to available
phosphorus. (5) Soil respiration of two typical stands (natural oak forest and black
locust) was the maximum at 25ºC and Q 10 of natural oak forest (1.630) is slightly
higher than black locust (1.572), soil respiration was increased with the soil moisture decreased, were the maximum at 60% soil water content.
The results suggested that the changes of vegetation type generated changes in
soil chemical properties, controlling the composition of microbial community in the
semiarid Loess Plateau region. The microbial community could be an indicator for
soil quality with respect to ecological restoration.
Key Words: Vegetation types; Soil microbial biomass carbon; Soil microbial
biomass nitrogen; Soil bacteria community; Soil fungi community; Soil properties;
Loess Plateau |
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