Population of Humic Acid Degrading Microorganisms in Andosols under Different Vegetation Types and Grassland Management Regimens

Abstract

To examine the effect of vegetation type and grassland management regimen on the distribution of humus-degrading microorganisms, populations of humic acid-degrading (HAD) bacteria and fungi at three Andosol sites were investigated using the dilution plate method. Each site had three different vegetation types (Eulalia grassland, bamboo grassland, and coniferous plantations). Among the six grassland sites, two were maintained by burning and the others by cutting. HAD microorganisms were found in all soil samples. Low densities and small percentages of HAD bacteria were detected with no significant differences in the number of bacteria found between different vegetation types and grasslands managed in different ways. In contrast, the densities and percentages of HAD fungi differed according to vegetation type and management regimen. Specifically, the percentages of HAD fungi were significantly higher for burned grasslands. At burned sites, the numbers and percentages of HAD bacteria remained at a consistently low level, and no distinct seasonal changes were observed. In contrast, marked seasonal fluctuations in HAD fungi were detected. The percentages of these fungi remained relatively high between April and December. These fluctuations are likely due to the effects of burning on soil microorganisms.

Degradation capacity of humic acids-degrading bacteria on humic acids extracted from arable soil

“…The CFU of S. maltophilia (strain 3) was the highest in combination treatments, accounting for 86.92, 83.23 and 82.52 % of total CFU in T1+T3, T2+T3 and T1+T2+T3, respectively. Different bacterial species exhibited varying capacities for HA degradation (Yanagi et al, 2008), which are closely associated with their adaptability to HA. In the present study, S. maltophilia (strain 3) remained higher CFU in HA substrate among the various single-colony and combination treatments and became the dominant species, indicating its suitability in the medium.…”

“…Therefore, the soil environment and global change are profoundly impacted by soil organic carbon (SOC); mainly consisting of humus C. Humic acids (HA) are a component of soil humus with an intermediate molecular weight, a complex structure and relatively active chemical and biological properties. The functional group structure and elemental composition of HA vary with different vegetation types, land-use patterns and extraction methods (Tatzber et al, 2007;Yanagi et al, 2008;Prentice, Webb, 2010). It has been found that traditional cultivation patterns are unfavourable for SOC sequestration and transformation (Eaton, Lawrence, 2009;Acharya et al, 2012).…”

Interactions between Humic Substances and Microorganisms and Their Implications for Nature-like Bioremediation Technologies

“…A large variety of bacterial consortia capable of degrading HSs were isolated from soil [ 9 , 13 , 14 , 93 , 94 ], coal [ 20 ], or aquatic environments [ 2 , 95 , 96 , 97 , 98 ], including marine and estuarine waters [ 6 , 99 , 100 ]. According to the data presented by Yanagi and coauthors [ 14 ], the population of total bacteria that were capable of degrading soil HAs varied from 0.1 × 10 6 to 2.8 × 10 6 CFU g −1 of soil, forming 0.2–3.5% of the total microbe density.…”

“…Fungi, which are active in the decomposition process, mainly include ascomycetes and basidiomycetes ( Table 3 ), which are common in the upper layer of forest and grassland soils [ 10 ]. Estimates performed by Yanagi and coworkers showed that the density of HA-degrading fungi in soil ranged from 1.9 × 10 4 to 14.9 × 10 4 CFU g −1 soil, or 2.4–12.5% of total fungi density [ 14 ].…”

“…HSs, in turn, beneficially affect the growth of microorganisms. HSs stimulate microbial growth, as a source of nutrients [ 6 , 10 , 12 , 13 , 14 ]. They also play the role of extracellular electron shuttles (EESs), which enables the availability of spatially remote substrates [ 15 , 16 , 17 , 18 ].…”