Search for: All records

The theory of microbial stoichiometry can predict the proportional coupling of microbial assimilation of carbon (C), nitrogen (N), and phosphorus (P). The proportional coupling is quantified by the homeostasis value (H). Covariation of H values for C, N, and P indicates that microbial C, N, and P assimilation are coupled. Here, we used a global dataset to investigate the spatiotemporal dynamics of H values of microbial C, N, and P across biomes. We found that land use and management led to the decoupling of P from C and N metabolism over time and across space. Results from structural equation modeling revealed that edaphic factors dominate the microbial homeostasis of P, while soil elemental concentrations dominate the homeostasis of C and N. This result was further confirmed using the contrasting factors on microbial P vs. microbial C and N derived from a machine-learning algorithm. Overall, our study highlights the impacts of management on shifting microbial roles in nutrient cycling.

 

Recent studies have reported worldwide vegetation suppression in response to increasing atmospheric vapor pressure deficit (VPD). Here, we integrate multisource datasets to show that increasing VPD caused by warming alone does not suppress vegetation growth in northern peatlands. A site-level manipulation experiment and a multiple-site synthesis find a neutral impact of rising VPD on vegetation growth; regional analysis manifests a strong declining gradient of VPD suppression impacts from sparsely distributed peatland to densely distributed peatland. The major mechanism adopted by plants in response to rising VPD is the “open” water-use strategy, where stomatal regulation is relaxed to maximize carbon uptake. These unique surface characteristics evolve in the wet soil‒air environment in the northern peatlands. The neutral VPD impacts observed in northern peatlands contrast with the vegetation suppression reported in global nonpeatland areas under rising VPD caused by concurrent warming and decreasing relative humidity, suggesting model improvement for representing VPD impacts in northern peatlands remains necessary.

 

Bacteria and fungi possess distinct physiological traits. Their macroecology is vital for ecosystem functioning such as carbon cycling. However, bacterial and fungal biogeography and underlying mechanisms remain elusive. In this study, we investigated bacterial versus fungal macroecology by integrating a microbial‐explicit model—CLM‐Microbe—with measured fungal (FBC) and bacterial biomass carbon (BBC) from 34 NEON sites. The distribution of FBC, BBC, and FBC: BBC (F:B) ratio was well simulated across sites, with variations in 99% (P < 0.001), 97% (P < 0.001), and 99% (P < 0.001) being explained by the CLM‐Microbe model, respectively. We found stronger biogeographic patterns of FBC relative to BBC across the United States. Fungal and bacterial turnover rates showed similar trends along latitude. However, latitudinal trends of their component fluxes (carbon assimilation, respiration, and necromass production) were distinct between bacteria and fungi, with those latitudinal trends following inverse unimodal patterns for fungi and showing exponential declining responses for bacteria. Carbon assimilation was dominated by vegetation productivity, and respiration was dominated by mean annual temperature for bacteria and fungi. The dominant factor for their necromass production differs, with edaphic factors controlling fungal and mean annual temperature controlling bacterial processes. The understanding of fungal and bacterial macroecology is an important step toward linking microbial metabolism and soil biogeochemical processes. Distinct fungal and bacterial macroecology contributes to the microbial ecology, particularly on microbial community structure and its association with ecosystem carbon cycling across space.

 

We applied a microbial-explicit model – the CLM-Microbe – to investigate the dynamics of C in vegetation, litter, soil, and microbes during 1901-2016. The CLM-Microbe model was able to reproduce global averages and latitudinal trends of gross (GPP) and net (NPP) primary productivity, heterotrophic (HR) and soil (SR) respiration, biomass C in fungi (FBC) and bacteria (BBC) in the top 30 cm and 1 m, dissolved (DOC) and soil organic C (SOC) in the top 30 cm and 1 m. In addition, the CLM-Microbe model captured the grid-level variation in GPP (R2=0.78), NPP (R2=0.63), SR (R2=0.26), HR (R2=0.23), DOC in 0-30 cm (R2=0.2) and 0-1 m (R2=0.22), SOC in 0-30 cm (R2=0.36) and 0-1 m (R2=0.26), FBC (R2=0.22) and BBC (R2=0.32) in 0-30 cm, and MBC in 0-1 m (R2=0.21). From the 1900s to 2007-2016, simulated C variables increased by approximately 30 PgC yr-1 for GPP, 15 PgC yr-1 for NPP, 12 PgC yr-1 for HR, 25 PgC yr-1 for SR, 1.0 PgC for FBC and 0.4 PgC for BBC in 0-30 cm, 1.5 PgC for FBC, 0.8 PgC for BBC, 2.5 PgC for DOC, 40 PgC for SOC, and 5 PgC for litter C in 0-1 m, and 40 PgC for vegetation C. The relative increases in C fluxes and pools varied across the globe. Increases in vegetation C were closely related to warming and increased precipitation, while C accumulation in microbes and soils was jointly governed by vegetation C input and soil temperature and moisture.