Abstract
Abstract. Slope aspect is an important topographic factor in the micro-ecosystem environment, but its effect on the microbial properties of grassland rhizospheric soil (RS) and non-rhizospheric soil (NRS) remain unclear. A field experiment was conducted at the Ansai Research Station on the Loess Plateau in China to test the influence of slope aspects (south-facing, north-facing, and northwest-facing slopes, all with Artemisia sacrorum as the dominant species) on RS and NRS microbial biomass carbon (MBC) contents, phospholipid fatty acid (PLFA) contents, and the rhizospheric effect (RE) of various microbial indices. Soil samples were collected from the three slope aspects, including rhizospheric and non-rhizospheric region, and analyzed to determine the various related microbial indices. The results showed that MBC content differed significantly among the slope aspects in RS but not in NRS, and the RE for MBC content in the south-facing slope was larger than that in the north-facing slope. RS total, bacterial, and Gram-positive bacterial PLFA contents in the south-facing slope were significantly lower than those in the north- and northwest-facing slopes, and RS Gram-negative bacterial (G−) and actinomycete PLFA contents in the south-facing slope were significantly lower than those in the north-facing slope. In contrast, NRS total, bacterial, and G− PLFA contents in the north-facing slope were significantly higher than those in the south- and northwest-facing slopes, and NRS fungal and actinomycete PLFA contents in the north- and south-facing slopes were significantly higher than those in the northwest-facing slope. RE for all PLFA contents except fungal in the northwest-facing slope were higher than those in the south-facing slope. Slope aspect significantly but differentially affected the microbial properties in RS and NRS, and the variable influence was due to an evident RE for most microbial properties.
Highlights
As an important topographic factor, slope aspect can affect the amount of solar radiation received (Selvakumar et al, 2009), and solar radiation influences ecologically critical factors of local microclimates and determines soil temperature, evaporation capacity, and soil-moisture content (Carletti et al, 2009; Bennie et al, 2008)
The rhizospheric effect (RE) for microbial biomass carbon (MBC) in the south-facing slope was highest among the slope aspects (Fig. 2a)
Bacterial phospholipid fatty acid (PLFA) content was similar to the trend for total PLFA content, with the lowest content in the www.solid-earth.net/9/1157/2018/
Summary
As an important topographic factor, slope aspect can affect the amount of solar radiation received (Selvakumar et al, 2009), and solar radiation influences ecologically critical factors of local microclimates and determines soil temperature, evaporation capacity, and soil-moisture content (Carletti et al, 2009; Bennie et al, 2008). Ai et al.: Influence of slope aspect on microbial properties (carbon, nitrogen, and phosphorus), microbial biomass, and enzymatic activities have been studied (Ai et al, 2017a; Ascher et al, 2012; Gilliam et al, 2014; Huang et al, 2015; Sidari et al, 2008; Qin et al, 2016; Bardelli et al, 2017; Liu et al, 2017). Previous studies have mainly focused on trees and shrubs, but the influence of slope aspect on grassland soil microorganisms is still unclear, even though the grassland ecosystem is an important component of terrestrial ecosystems
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