Linking stoichiometric homeostasis of microorganisms with soil phosphorus dynamics in wetlands subjected to microcosm warming

Global warming changes biomass and C:N:P stoichiometry of different components in terrestrial ecosystems

Global warming has significantly affected terrestrial ecosystems. Biomass and C:N:P stoichiometry of plants and soil is crucial for enhancing plant productivity, improving human nutrition, and regulating biogeochemical cycles. However, the effect of warming on the biomass and C:N:P stoichiometry of different components (plant, leaf, stem, root, litter, soil, and microbial biomass) in various terrestrial ecosystems remains uncertain. We conducted a comprehensive meta-analysis to investigate the global patterns of biomass and C:N:P stoichiometry responses to warming, as well as interaction relationships based on 1399 paired observations from 105 warming studies. Results indicated that warming had a significant impact on various aspects of plant growth, including an increase in plant biomass (+16.55%), plant C:N ratio (+4.15%), leaf biomass (+16.78%), stem biomass (+23.65%), root biomass (+22.00%), litter C:N ratio (+9.54%) and soil C:N ratio (+5.64%). However, it also decreased stem C:P ratio (-23.34%), root C:P ratio (-12.88%), soil N:P ratio (-14.43%) and soil C:P ratio (-16.33%). The magnitude of warming was the primary drivers of changes of biomass and C:N:P stoichiometry. By establishing the general response curves of changes in biomass and C:N:P ratios with increasing temperature, we demonstrated that warming effect on plant, root, and litter biomass shifted from negative to positive, whereas that on leaf and stem biomass changed from positive to negative as temperature increased. Additionally, the effect of warming on root C:N ratio, root biomass, and microbial biomass N:P ratios shifted from positive to negative, whereas the effects on plant N:P, leaf N:P, leaf C:P, root N:P ratios, and microbial biomass C:N ratio changed from negative to positive with increasing temperature. Our research can help assess plant productivity and optimize ecosystem stoichiometry precisely in the context of global warming.

Distinguishing Stoichiometric Homeostasis of Soil Microbial Biomass in Alpine Grassland Ecosystems: Evidence From 5,000 km Belt Transect Across Qinghai-Tibet Plateau

The biogeographic characteristics of soil microbial biomass stoichiometry homeostasis and also its mechanisms are commonly thought to be key factors for the survival strategies and resource utilization of soil microbes under extreme habitat. In this work, we conducted a 5,000-km transect filed survey in alpine grassland across Qinghai-Tibet Plateau in 2015 to measure soil microbial biomass carbon (MBC) and nitrogen (MBN) across alpine steppe and meadow. Based on the differences of climate and soil conditions between alpine steppe and meadow, the variation coefficient was calculated to investigate the homeostatic degree of MBC to MBN. Furthermore, the "trade-off" model was utilized to deeply distinguish the homeostasis degree of MBC/MBN between alpine steppe and meadow, and the regression analysis was used to explore the variability of trade-off in response to environmental factors in the alpine grassland. The results showed that the coefficient of variation (CV) of MBC/MBN in alpine meadow (CV = 0.4) was lower than alpine steppe (CV = 0.7). According to the trade-off model, microbial turnover activity of soil N relative to soil C increased rapidly and then decreased slightly with soil organic carbon (SOC), soil total nitrogen (STN), and soil water content across alpine meadow. Nevertheless, in alpine steppe, SOC/STN had a positive effect on microbial turnover of soil N. These results suggested that water, heat, and soil nutrients availability were the key factors affecting the C:N stoichiometry homeostasis of soil microbial biomass in Qinghai-Tibet Plateau (QTP)'s alpine grassland. Since the difference of survival strategy of the trade-off demands between soil C and N resulting in different patterns and mechanism, the stoichiometry homeostasis of soil microbial biomass was more stable in alpine meadow than in alpine steppe.

Microorganisms that participate in biochemical cycles in wetlands

Several biochemical cycles are performed in natural wetlands (NWs) and constructed wetlands (CWs). The knowledge of the microorganisms could be used to monitor the restoration of wetlands or the performance of the wastewater treatment. Regarding bacteria, Proteobacteria phylum is the most abundant in NWs and CWs, which possesses a role in N, P, and S cycles, and in the degradation of organic matter. Other phyla are present in lower abundance. Archaea participate in methanogenesis, methane oxidation, and the methanogenic N2 fixation. Sulfur and phosphorus cycles are also performed by other microorganisms, such as Chloroflexi or Nitrospirae phyla. In general, there is more information about the N cycle, especially nitrification and denitrification. Processes where archaea participate (e.g. methane oxidation, methanogenic N2 fixation) are still unclear their metabolic role and several of these microorganisms have not been isolated so far. The study can use 16S rDNA genes or functional genes. The use of functional genes gives information to monitor specific microbial populations and 16S rDNA is more suitable to perform the taxonomic classification. Also, there are several Candidatus microorganisms, which have not been isolated so far. However, it has been described their metabolic role in the biochemical cycles in wetlands.

Analysis of factors controlling sediment phosphorus flux potential of wetlands in Hulun Buir grassland by principal component and path analysis method

Phosphorus (P) flux potential can predict the trend of phosphorus release from wetland sediments to water and provide scientific parameters for further monitoring and management for phosphorus flux from wetland sediments to overlying water. Many studies have focused on factors affecting sediment P flux potential in sediment-water interface, but rarely on the relationship among these factors. In the present study, experiment on sediment P flux potential in sediment-water interface was conducted in six wetlands in Hulun Buir grassland, China and the relationships among sediment P flux potential in sediment-water interface, sediment physical properties, and sediment chemical characteristics were examined. Principal component analysis and path analysis were used to discuss these data in correlation coefficient, direct, and indirect effects on sediment P flux potential in sediment-water interface. Results indicated that the major factors affecting sediment P flux potential in sediment-water interface were amount of organophosphate-degradation bacterium in sediment, Ca-P content, and total phosphorus concentrations. The factors of direct influence sediment P flux potential were sediment Ca-P content, Olsen-P content, SOC content, and sediment Al-P content. The indirect influence sediment P flux potential in sediment-water interface was sediment Olsen-P content, sediment SOC content, sediment Ca-P content, and sediment Al-P content. And the standard multiple regression describing the relationship between sediment P flux potential in sediment-water interface and its major effect factors was Y = 5.849 - 1.025X ₁ - 1.995X ₂ + 0.188X ₃ - 0.282X ₄ (r = 0.9298, p < 0.01, n = 96), where Y is sediment P flux potential in sediment-water interface, X ₁ is sediment Ca-P content, X ₂ is sediment Olsen-P content, X ₃ is sediment SOC content, and X ₄ is sediment Al-P content. Therefore, future research will focus on these sediment properties to analyze the interrelation among sediment properties factors, main vegetable factors, and environment factors which influence the sediment P flux potential in sediment-water interface.

Effects of three global change drivers on terrestrial C:N:P stoichiometry: a global synthesis

Over the last few decades, there has been an increasing number of controlled-manipulative experiments to investigate how plants and soils might respond to global change. These experiments typically examined the effects of each of three global change drivers [i.e., nitrogen (N) deposition, warming, and elevated CO₂ ] on primary productivity and on the biogeochemistry of carbon (C), N, and phosphorus (P) across different terrestrial ecosystems. Here, we capitalize on this large amount of information by performing a comprehensive meta-analysis (>2000 case studies worldwide) to address how C:N:P stoichiometry of plants, soils, and soil microbial biomass might respond to individual vs. combined effects of the three global change drivers. Our results show that (i) individual effects of N addition and elevated CO₂ on C:N:P stoichiometry are stronger than warming, (ii) combined effects of pairs of global change drivers (e.g., N addition + elevated CO₂ , warming + elevated CO₂ ) on C:N:P stoichiometry were generally weaker than the individual effects of each of these drivers, (iii) additive interactions (i.e., when combined effects are equal to or not significantly different from the sum of individual effects) were more common than synergistic or antagonistic interactions, (iv) C:N:P stoichiometry of soil and soil microbial biomass shows high homeostasis under global change manipulations, and (v) C:N:P responses to global change are strongly affected by ecosystem type, local climate, and experimental conditions. Our study is one of the first to compare individual vs. combined effects of the three global change drivers on terrestrial C:N:P ratios using a large set of data. To further improve our understanding of how ecosystems might respond to future global change, long-term ecosystem-scale studies testing multifactor effects on plants and soils are urgently required across different world regions.