Bacterial and enchytraeid abundance accelerate soil carbon turnover along a lowland vegetation gradient in interior Alaska

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• 作者：M.P. Waldrop^a ; ^{mwaldrop@usgs.gov} ; J.W. Harden^a ; M.R. Turetsky^b ; D.G. Petersen^c ; A.D. McGuire^d ; ^e ; M.J.I. Briones^f ; A.C. Churchill^e ; D.H. Doctor^g ; L.E. Pruett^a
• 关键词：Bonanza Creek LTER ; Boreal wetland ; C and N mineralization ; Fungi ; Bacteria ; Enchytraeids ; Soil enzymes ; Black spruce ; Tussock ; Fen
• 刊名：Soil Biology & Biochemistry
• 出版年：2012
• 期刊代码：96_00380717
• 类别：abs
• 出版时间：July, 2012
• 卷：50
• 期：Complete
• 页码：188-198
• 文件大小：614 K

摘要

Boreal wetlands are characterized by a mosaic of plant communities, including forests, shrublands, grasslands, and fens, which are structured largely by changes in topography and water table position. The聽soil associated with these plant communities contain quantitatively and qualitatively different forms of soil organic matter (SOM) and nutrient availability that drive changes in biogeochemical cycling rates. Therefore different boreal plant communities likely contain different soil聽biotic communities which in turn affect rates of organic matter decomposition. We examined relationships between plant communities, microbial communities, enchytraeids,聽and soil C turnover in near-surface soils along a shallow topographic soil moisture and vegetation gradient in interior Alaska. We tested the hypothesis that as soil moisture increases along the gradient, surface soils would become increasingly dominated by bacteria and mesofauna and have more rapid rates of C turnover. We utilized bomb radiocarbon techniques to infer rates of C聽turnover and the ¹³C isotopic composition of SOM and respired CO₂ to infer the degree of soil humification. Soil phenol oxidase and peroxidase enzyme activities were generally higher in the rich fen compared with the forest and bog birch sites. Results indicated greater C fluxes and more rapid C turnover in the surface soils of the fen sites compared to the wetland forest and shrub sites. Quantitative PCR analyses of soil bacteria and archaea, combined with enchytraeid counts, indicated that surface soils from the lowland fen ecosystems had higher abundances of these microbial and mesofaunal聽groups. Fungal abundance was聽highly variable and not significantly different among sites. Microbial data was utilized in a food web聽model that confirmed that rapidly cycling systems are dominated by bacterial activity and enchytraeid grazing. However, our results also suggest that oxidative enzymes play an important role in the C mineralization process in saturated systems, which has been often ignored.