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Microbial activity and soil respiration under nitrogen addition in Alaskan boreal forest
 

Summary: Microbial activity and soil respiration under nitrogen
addition in Alaskan boreal forest
S T E V E N D . A L L I S O N *w, C L A U D I A I . C Z I M C Z I K w and K AT H L E E N K . T R E S E D E R *w
*Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697, USA,
wDepartment of Earth System Science, University of California, Irvine, CA 92697, USA
Abstract
Climate warming could increase rates of soil organic matter turnover and nutrient
mineralization, particularly in northern high-latitude ecosystems. However, the effects
of increasing nutrient availability on microbial processes in these ecosystems are poorly
understood. To determine how soil microbes respond to nutrient enrichment, we
measured microbial biomass, extracellular enzyme activities, soil respiration, and the
community composition of active fungi in nitrogen (N) fertilized soils of a boreal forest
in central Alaska. We predicted that N addition would suppress fungal activity relative to
bacteria, but stimulate carbon (C)-degrading enzyme activities and soil respiration.
Instead, we found no evidence for a suppression of fungal activity, although fungal
sporocarp production declined significantly, and the relative abundance of two fungal
taxa changed dramatically with N fertilization. Microbial biomass as measured by
chloroform fumigation did not respond to fertilization, nor did the ratio of fungi : bacter-
ia as measured by quantitative polymerase chain reaction. However, microbial biomass
C : N ratios narrowed significantly from 16.0 1.4 to 5.2 0.3 with fertilization. N

  

Source: Allison, Steven D. - Departments of Ecology and Evolutionary Biology & Earth System Science, University of California, Irvine

 

Collections: Environmental Sciences and Ecology