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Citation

Hopkins D, Sparrow AD, Shillam L, English LC, Dennis P, Novis PM, Elberling B, Gregorich EG & Greenfield LG (2008) Enzymatic activities and microbial communities in an Antarctic dry valley soil: Responses to C and N supplementation. Soil Biology and Biochemistry, 40 (9), pp. 2130-2136. https://doi.org/10.1016/j.soilbio.2008.03.022

Abstract
The soils of the Antarctic dry valleys are exposed to extremely dry and cold conditions. Nevertheless, they contain small communities of micro-organisms that contribute to the biogeochemical transformations of the bioelements, albeit at slow rates. We have determined the dehydrogenase, ?-glucosidase, acid and alkaline phosphatase and arylsulphatase activities and the rates of respiration (CO2 production) in laboratory assays of soils collected from a field experiment in an Antarctic dry valley. The objective of the field experiment was to test the responses of the soil microbial community to additions of C and N in simple (glucose and NH4Cl) and complex forms (glycine and lacustrine detritus from the adjacent lake comprising principally cyanobacterial necromass). The soil samples were taken 3 years after the experimental treatments had been applied. In unamended soil, all enzyme activities and respiration were detected indicating that the enzymatic capacity to mineralize organic C, P and S compounds existed in the soil, despite the very low organic matter content. Relative to the control (unamended soil), respiration was significantly increased by all the experimental additions of C and N except the smallest NH4Cl addition (1 mg N g-1 soil) and the smallest detritus addition (1.5 mg C g-1 soil and 0.13 mg N g-1 soil). The activities of all enzymes except dehydrogenase were increased by C and combined large C (10 mg C g-1 soil) and N additions, but either unchanged or diminished by addition of either N only or N (up to 10 mg N g-1 soil) with only small C (1 mg C g-1 soil) additions in the form of glucose and NH4Cl. This suggests that in the presence of a large amount of N, the C supply for enzyme biosynthesis was limited. When normalized with respect to soil respiration, only arylsulphatase per unit of respiration showed a significant increase with C and N additions as glucose and NH4Cl, consistent with S limitation when C and N limitations have been alleviated. Based on the positive responses of enzyme activity, detritus appeared to provide either conditions or resources which led to a larger biological response than a similar amount of C and more N added in the form of defined compounds (glucose, NH4Cl or glycine). Assessment of the soil microbial community by ester-linked fatty acid (ELFA) analysis provided no evidence of changes in the community structure as a result of the C and N supplementation treatments. Thus the respiration and enzyme activity responses to supplementation occurred in an apparently structurally stable or unresponsive microbial community.

Keywords
10; 3; activities; analysis; Antarctic; Assessment; C; CAPACITY; Communities; community; COMPLEX; Control; ENZYMES; evidence; experiment; fatty acid; FATTY-ACID; FIELD; GLUCOSE; Laboratories; LAKE; LIMITATIONS; MATTER; objective; RATES; resources; respect; RESPIRATION; responses; SAMPLE; SAMPLES; SOIL; SOILS; Structure; SUPPLEMENTATION; Transformation; treatment

Journal
Soil Biology and Biochemistry: Volume 40, Issue 9