Soil microorganisms play an important role in soil carbon sequestration. Microbial biomass and necromass contribute up to 3% and 50% to soil organic carbon, respectively. We studied agricultural sites across an elevational gradient from 115 to 2400 m a.s.l. in Austria, including arable sites, field margins, grasslands, and alpine meadows, for their differences in microbial biomass, necromass, and their derivatives. Median microbial biomass C (MBC) increased from arable (474 mg kg −1 ) to field margins (926 mg kg −1 ; +95.4%), grasslands (1400 mg kg −1 ; +51.2%), and alpine meadows (2940 mg kg −1 ; +110%). Median microbial necromass C (MNC) similarly increased: arable (2460 mg kg −1 ), field margins (3750 mg kg −1 ; +52.4%), grasslands (6660 mg kg −1 ; +77.6%), alpine meadows (10,100 mg kg −1 ; +51.7%). The MNC:MBC ratio was highest in arable soils (5.46) and lower in field margins (4.32), grasslands (4.54), and alpine meadows (3.66). The contribution of MBC to Total Organic Carbon (TOC) rose from arable (2.62%) to field margins (3.03%) and grasslands (4.00%), then levelled in alpine meadows (3.75%); the contribution of MNC to TOC was highest in grasslands (20.0%) versus arable (15.9%), field margins (17.2%), and alpine meadows (16.6%). TN, TOC, bulk density, altitude, and clay content were identified as explanatory variables for soil microbial biomass. Arable soils showed the highest fungi:bacteria ratios in necromass. Our results emphasize the importance of land use and local pedoclimatic conditions regarding soil microbial biomass and necromass, as well as the role of microbes in sustaining soil TOC.
Monoshyn et al. (Mon,) studied this question.