Find one published paper from a scientific journal that includes data on two of

Question

Find one published paper from a scientific journal that includes data on two of the following microbial parameters: (1) soil microbial biomass, (2) soil microbial diversity, and/or (3) soil microbial activity. Attach a link of the paper to this completed assignment. For this paper report the following:

Part A. copy and paste the abstract of the paper, and include a citation below.

Part B. Briefly describe the experimental study, including objectives and/or hypotheses.

Part C. Outline the methods used in the study to measure microbial biomass, diversity, and/or activity (1,2,3 above). In this description, be sure to discuss the importance or relevance of these methods for addressing the objectives of the study.

Part D. Using your understanding of the pros (advantages) and cons (disadvantages) of the methods used, critically discuss if the techniques used were appropriate for addressing the study objectives. If you think the approach is appropriate, be sure to explain why. If you do not find it appropriate, indicate an alternative method that may have been better. (5pts)

Explanation / Answer

Soil microbial biomass, activity and community composition along altitudinal gradients in the High Arctic (Billefjorden, Svalbard)

Abstract The unique and fragile High Arctic ecosystems are vulnerable to proceeding global climate warming. Elucidation

13 of factors driving microbial distribution and activity in Arctic soils is essential for comprehensive understanding of the ecosystem functioning and its response to environmental change. The goals of this study were to investigate the microbial biomass, activity, microbial community structure (MCS) and its abiotic controls in soils along three elevational gradients in 16 coastal mountains of Billefjorden, Central Svalbard. Soils from four different altitudes (25, 275, 525, and 765 m above sea level) were analysed for a suite of characteristics including temperature regimes, organic matter content, base cation availability, moisture, pH, basal respiration, and microbial biomass and community structure using phospholipid fatty acid (PLFA). We observed significant altitudinal zonation of most edaphic characteristics reflected by soil microbial properties. The microbial biomass and activity normalized per unit of organic carbon significantly increased with elevation. The two dominant microbial groups, fungi and bacteria, had different habitat preferences, resulting in high fungi to bacteria (F/B) ratios at the most elevated sites. The changes in MCS were mainly governed by the bedrock chemistry, soil pH, organic carbon content and soil moisture. While the direct impact of summer soil temperature regimes on soil microbes was likely negligible, it s influence on plant distribution along the gradients have strong implications for edaphic conditions and consequently also for soil microbes. Our results highlight the need to consider unvegetated high elevation areas as hotspots of microbial activity and important habitats within the High Arctic ecosystem.

Citation

Kotas, Petr & Santruckova, Hana & Elster, Josef & Kaštovská, Eva. (2017). Soil microbial biomass, activity and community composition along altitudinal gradients in the High Arctic (Billefjorden, Svalbard). Biogeosciences Discussions. 1-31.

Study site and soil sampling

Microbial community structure

The soil microbial community structure was defined by an analysis of PLFA according to modified protocol of Frostegård et al. (1993). Briefly, 13 g (according to TOC content) of freezedried soil samples was extracted twice with singlephase extraction mixture consisting of chloroform, methanol and citrate buffer. After overnight phase separation achieved by adding more chloroform and buffer, the organic phase was purified on silica columns (SPESI Supelclean 250mg/3 mL; Supelco®, PA, USA) using chloroform, acetone and methanol. The polar fraction was transesterified to the fatty acid methyl esters (FAME) (Bossio and Scow, 1998). All FAMEs were quantified by an internal standard calibration procedure using methylnonadecanoate (19:0) as an internal standard. To identify the FAMEs, retention times and mass spectra were compared with those obtained from standards (Bacterial Acid Methyl Esters standard, the 37component FAME Mix, PUFA2, and PUFA3; Supelco, USA). The ISQ mass spectrometer (MS) equipped with Focus gas chromatograph (GC) (Thermo Fisher Scientific, USA) was used for chromatographic separation and detection. Only specific PLFAs were used to assess the microbial community structure: a14:0, i15:0, a15:0, i16:0, i17:0, a17:0 were used as markers of Grampositive bacteria (G+); 16:19, 16:15, cy17:0, 18:111, 18:17, cy19:0 as markers of Gramnegative bacteria (G); 10Me16:0 and 10Me18:0 as markers of Actinobacteria (Kroppenstedt, 1985), 18:19, 18:26,9 as markers of fungi (Frostegård and Bååth, 1996) and polyunsaturated fatty acids 18:43, 20:53 were used as markers of phototrophic microorganisms (Hardison et al., 2013; Khotimchenko et al., 2002). A sum of Actinobacterial markers, PLFAs specific to G+ and G bacteria and general bacterial markers 15:0, 17:0 and 18:15 was used to calculate bacterial biomass and fungi to bacteria (F/B) ratio. The sum of all lipid markers mentioned above and nonspecific PLFAs 14:0, 16:0, 18:0 and 16:17 was used as proxy for microbial biomass (PLFAtot).   

Sterol analyses

Ergosterol, sitosterol and brassicasterol were used as biomarkers of fungal biomass (Gessner et al., 1991), plant (Sinsabaugh et al., 1997) and algal (Volkman, 1986; 2003) residues in organic matter (OM), respectively. Sterols were simultaneously determined using microwave assisted extraction adapted from Montgomery et al. (2000) and GC/MS (ISQMS equipped with Focus GC, Thermo Fisher Scientific, USA) analysis. Briefly, 0.5 g of freezedried soil was treated with 154 6 mL of methanol and 2 mL of 2 M NaOH.   

https://www.researchgate.net/publication/317550548_Soil_microbial_biomass_activity_and_community_composition_along_altitudinal_gradients_in_the_High_Arctic_Billefjorden_Svalbard

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