Browsing by Author "Bahn, Michael"
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Item Biotic interactions and biogeochemical processes in the soil environment(2012-05-24) Subke, J.-A.; Carbone, M.S.; Khomik, M.; Stoy, Paul C.; Bahn, Michael"Soils play a key role in the terrestrial carbon (C) cycle bystoring and emitting large quantities of C. The impact of abiotic conditions (mainly soil temperature and moisture) on soil C turnover is well documented, but unravelling the influence of these drivers across temporal and spatial scales remains an important challenge. Biotic factors, such as microbial abundance and diversity, macro-faunal food webs and below-ground plant (i.e. root) biomass and diversity, play an important role in controlling soil C storage and emission, but remain under-investigated. To better understand the soil processes underlying terrestrial C cycling, the interactions between plants (autotrophs) and soil organisms (heterotrophs) need to be addressed more explicitly and integrated with short- and long-term effects of abiotic drivers. This special issue presents recent advances in field, laboratory, and modelling studies on soil C dynamics, with a particular emphasis on those aiming to resolve abiotic and biotic influences. The manuscripts highlight three areas of investigation that we suggest are central to current and future progress in ecosystem C dynamic research: (1) novel interpretations of abiotic controls on soil CO2 efflux, (2) legacy effects of abiotic drivers of soil C dynamics, and (3) the interaction between plant C dynamics and soil biological processes."Item Redefinition and global estimation of basal ecosystem respiration rate(2001-10-13) Yuan, Wenping; Luo, Yiqi; Li, Shuguang; Yu, Guirui; Zhou, Tao; Bahn, Michael; Black, Andy T.; Desai, Ankur R.; Cescatti, Alessandro; Marcolla, Barbara; Jacobs, Cor; Chen, Jiquan; Aurela, Mika; Bernhofer, Christian; Gielen, Bert; Bohrer, Gil; Cook, David R.; Dragoni, Danilo; Dunn, Allison L.; Gianelle, Damiano; Grünwald, Thomas; Ibrom, Andreas; Leclerc, Monique Y.; Lindroth, Anders; Liu, Heping; Marchesini, Luca Belelli; Montagnani, Leonardo; Pita, Gabriel; Rodeghiero, Mirco; Rodrigues, Abel; Starr, Gregory; Stoy, Paul C.Basal ecosystem respiration rate (BR), the ecosystem respiration rate at a given temperature, is a common and important parameter in empirical models for quantifying ecosystem respiration (ER) globally. Numerous studies have indicated that BR varies in space. However, many empirical ER models still use a global constant BR largely due to the lack of a functional description for BR. In this study, we redefined BR to be ecosystem respiration rate at the mean annual temperature. To test the validity of this concept, we conducted a synthesis analysis using 276 site-years of eddy covariance data, from 79 research sites located at latitudes ranging from ∼3°S to ∼70°N. Results showed that mean annual ER rate closely matches ER rate at mean annual temperature. Incorporation of site-specific BR into global ER model substantially improved simulated ER compared to an invariant BR at all sites. These results confirm that ER at the mean annual temperature can be considered as BR in empirical models. A strong correlation was found between the mean annual ER and mean annual gross primary production (GPP). Consequently, GPP, which is typically more accurately modeled, can be used to estimate BR. A light use efficiency GPP model (i.e., EC-LUE) was applied to estimate global GPP, BR and ER with input data from MERRA (Modern Era Retrospective-Analysis for Research and Applications) and MODIS (Moderate resolution Imaging Spectroradiometer). The global ER was 103 Pg C yr −1, with the highest respiration rate over tropical forests and the lowest value in dry and high-latitude areas.