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Interactions of tropospheric CO 2 and O 3 enrichments and moisture variations on microbial biomass and respiration in soil
Author(s) -
Islam K. R.,
Mulchi C. L.,
Ali A. A.
Publication year - 2000
Publication title -
global change biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.146
H-Index - 255
eISSN - 1365-2486
pISSN - 1354-1013
DOI - 10.1046/j.1365-2486.2000.00307.x
Subject(s) - respiration , chemistry , environmental chemistry , soil water , biomass (ecology) , soil carbon , zoology , horticulture , agronomy , botany , biology , ecology
Summary Soil microbial biomass C (C mic ) is a sensitive indicator of trends in organic matter dynamics in terrestrial ecosystems. This study was conducted to determine the effects of tropospheric CO 2 or O 3 enrichments and moisture variations on total soil organic C (C org ), mineralizable C fraction (C Min ), C mic , maintenance respiratory (qCO 2 ) or C mic death (qD) quotients, and their relationship with basal respiration (BR) rates and field respiration (FR) fluxes in wheat‐soybean agroecosystems. Wheat ( Triticum aestivum L.) and soybean ( Glycine max . L. Merr) plants were grown to maturity in 3‐m dia open‐top field chambers and exposed to charcoal‐filtered (CF) air at 350 μL CO 2 L −1 ; CF air + 150 μL CO 2 L −1 ; nonfiltered (NF) air + 35 n L O 3 L −1 ; and NF air + 35 n L O 3 L −1 + 150 μL CO 2 L −1 at optimum (− 0.05 MPa) and restricted soil moisture (− 1.0 ± 0.05 MPa) regimes. The + 150 μL CO 2 L −1 additions were 18 h d −1 and the + 35 n L O 3 L −1 treatments were 7 h d −1 from April until late October. While C org did not vary consistently, C Min , C mic and C mic fractions increased in soils under tropospheric CO 2 enrichment (500 μL CO 2 L −1 ) and decreased under high O 3 exposures (55 ± 6 n L O 3 L −1 for wheat; 60 ± 5 n L O 3 L −1 for soybean) compared to the CF treatments (25 ± 5 n L O 3 L −1 ). The qCO 2 or qD quotients of C mic were also significantly decreased in soils under high CO 2 but increased under high O 3 exposures compared to the CF control. The BR rates did not vary consistently but they were higher in well‐watered soils. The FR fluxes were lower under high O 3 exposures compared to soils under the CF control. An increase in C mic or C mic fractions and decrease in qCO 2 or qD observed under high CO 2 treatment suggest that these soils were acting as C sinks whereas, reductions in C mic or C mic fractions and increase in qCO 2 or qD in soils under elevated tropospheric O 3 exposures suggest the soils were serving as a source of CO 2 .