Abstract
Several microbiological indicators of soil quality present high sensitivity, but little is known about the influence of topographic factors on them. This work aimed to evaluate variability of biological indicators of soil quality across a hillslope under native forest and the influence of topographic factors on them. Four positions on a hillslope were evaluated. Activity of the enzymes β-glucosidase, acid phosphatase, urease and fluorescein diacetate (FDA) hydrolysis were determined, as well as basal and substrate-induced respiration, and density of microorganisms: total bacteria, total fungi, actinobacteria, phosphate solubilizers, ammonifiers, native rhizobia, free-living N2-fixing bacteria, spores of arbuscular mycorrhizal fungi and percentage of root colonization by arbuscular mycorrhizal fungi. Activity and density of microorganisms were correlated with topographic factors. The relation of these factors to the variations of the evaluated indicators was determined using the random forest algorithm. Microbiological indicators varied according to the hillslope positions. The indicators urease, basal respiration, spore density, mycorrhizal colonization, total bacteria and fungi, phosphate solubilizers, and free-living N2-fixing bacteria detected in JNFB and FAM culture medium did not vary with terrain attributes and were therefore more indicated in cases of topographic variations. This and future studies can help to select the best microbiological indicators for different conditions.
Highlights
Soil is a heterogeneous and dynamic system and AGRARIAN SCIENCESAn Acad Bras Cienc (2019) 91(4)INDICATORS INFLUENCED BY TOPOGRAPHIC FACTORS to perform their functions side by side to maintain soil quality (Moreira et al 2006)
Organisms that contribute to processes that support the provision of ecosystem services are more commonly evaluated, and indirect assessments of activity of microorganisms that contribute to soil quality, such as enzyme activity evaluations, can be made (Štursová et al 2016, Santos et al 2016, Moreira et al 2013)
The hillslope evaluated at Bocaina Mountain Range presents microorganisms that perform different functions in the maintenance of the quality of the soil and some groups of biological indicators of soil quality vary according to topographic factors, mainly altitude, slope and longitudinal curvature
Summary
Soil is a heterogeneous and dynamic system and AGRARIAN SCIENCESAn Acad Bras Cienc (2019) 91(4)INDICATORS INFLUENCED BY TOPOGRAPHIC FACTORS to perform their functions side by side to maintain soil quality (Moreira et al 2006). The ability of a soil to function within the limits of a natural or managed ecosystem (Doran and Parkin, 1994) can be determined by physical, chemical, and biological indicators These latter are evaluated by processes carried out by the microbial community, which guarantee the maintenance and productivity of ecosystems, such as the carbon cycle and plant nutrients in the soil (Swift et al 2010). Only a small part of these microorganisms are cultivable, which makes it impractical to isolate them to evaluate their activity in soil and to allow inferences about the system To meet this need, organisms that contribute to processes that support the provision of ecosystem services are more commonly evaluated, and indirect assessments of activity of microorganisms that contribute to soil quality, such as enzyme activity evaluations, can be made (Štursová et al 2016, Santos et al 2016, Moreira et al 2013)
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