Does Litter Decomposition Rate Indicate Species Status in the Plant Community of Alpine Meadow?

Litter decomposition is the physical and chemical breakdown of dead plant material, which is affected by the litter quality, environmental conditions and the composition of decomposer communities (Parton et al. 2007). Within biomes, environmental conditions set a similar background broadly (Berg et al. 1993; Moore et al., 2001; Raich et al. 2006; Parton et al. 2007) and microbial communities are assumed to be ‘functionally equivalent’ in terms of carbon metabolism (Andrén and Balandreau 1999). Consequently, litter quality has been considered as the predominant control on the rate of decomposition of organic matter in the ecosystem (Cornwell et al. 2008). Litter quality was closely related with nutrient use efficiency (NUE), which covers a variety of physiological processes, including the relation between the nutrient content of a plant and its growth rate (Small 1972) and the partitioning of nutrients between litterfall and ‘resorption’ pathways (Vitousek 1982). Nutrient use efficiency plays an important role in the success of plants in intra- and interspecies competition in natural eco-systems (Small 1972). Here we hypothesis that the plant community structure, which was decided by earlier NUE interactions, may correlate with the litter decomposition rates

Patterns and drivers of prokaryotic communities in thermokarst lake water across Northern Hemisphere

13 páginas.- 5 figuras.- 81referencias.Aim: The formation of thermokarst lakes could make a large amount of carbon accessible to microbial degradation, potentially intensifying the permafrost carbon-climate feedback via carbon dioxide/methane emissions. Because of their diverse functional roles, prokaryotes could strongly mediate biogeochemical cycles in thermokarst lakes. However, little is known about the large-scale patterns and drivers of these communities. Location: Permafrost regions in the Northern Hemisphere. Time period: Present day. Major taxa studied: Prokaryotes. Methods: Based on a combination of large-scale measurements on the Tibetan Plateau and data syntheses in pan-Arctic regions, we constructed a comprehensive dataset of 16S rRNA sequences from 258 thermokarst lakes across Northern Hemisphere permafrost regions. We also used the local contributions to beta diversity (LCBD) to characterize the variance of prokaryotic species composition and screened underlying drivers by conducting a random forest modelling analysis. Results: Prokaryotes in thermokarst lake water were dominated by the orders Burkholderiales, Micrococcales, Flavobacteriales and Frankiales. The relative abundance of dominant taxa was positively associated with dissolved organic matter (DOM) properties, especially for the chromophoric/aromatic compounds. Microbial structure differed between high-altitude and high-latitude thermokarst lakes, with the dominance of Flavobacterium in high-altitude lakes, and the enrichment of Polynucleobacter in high-latitude lakes. More importantly, climatic variables were among the main drivers shaping the large-scale variation of prokaryotic communities. Specifically, mean annual precipitation was the best predictor for prokaryotic beta diversity across the Northern Hemisphere, as well as in the high-altitude permafrost regions, while mean annual air temperature played a key role in the high-latitude thermokarst lakes. Main conclusions: Our findings demonstrate significant associations between dominant taxa and DOM properties, as well as the important role of climatic factors in affecting prokaryotic communities. These findings suggest that climatic change may alter DOM conditions and induce dynamics in prokaryotic communities of thermokarst lake water in the Northern Hemisphere. © 2023 John Wiley & Sons Ltd.This work was supported by the National Key Research and Development Program of China (2022YFF0801903), National Natural Science Foundation of China (31988102, and 31825006), and Tencent Foundation through the XPLORER PRIZE. M.D‐B. acknowledges support from TED2021‐130908B‐C41/AEI/10.13039/501100011033/Unión Europea NextGenerationEU/PRTR and from the Spanish Ministry of Science and Innovation for the I + D + i project PID2020‐115813RA‐I00 funded by MCIN/AEI/10.13039/501100011033.Peer reviewe

Permafrost-microbial-nutrient-limitation.zip

The dataset shows the raw data for our unpublished paper 'Microbial nitrogen and phosphorus co-limitation across permafrost region'.</p

Circ_0102543 suppresses hepatocellular carcinoma progression through the miR‐942‐5p/SGTB axis

Abstract Introduction Hepatocellular carcinoma (HCC) is one of the most serious cancers. Circular RNA (circRNA) has been reported to regulate the progression of HCC. Herein, the role of circ_0102543 in HCC tumorigenesis was investigated. Materials The expression levels of circ_0102543, microRNA‐942‐5p (miR‐942‐5p), and small glutamine rich tetratricopeptide repeat co‐chaperone beta (SGTB) were detected by quantitative real‐time PCR (qRT‐PCR). 3‐(4, 5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium Bromide (MTT) assay, thymidine analog 5‐ethynyl‐2'‐deoxyuridine (EDU) assay, transwell assay, and flow cytometry were conducted to explore the function of circ_0102543 in HCC cells and the regulatory mechanism among circ_0102543, miR‐942‐5p and SGTB in HCC cells. Western blot examined the related protein levels. Results The expression of circ_0102543 and SGTB was decreased in HCC tissues, while the expression of miR‐942‐5p was increased. Circ_0102543 acted as a sponge for miR‐942‐5p, and SGTB was the target of miR‐942‐5p. Circ_0102543 up‐regulation hindered tumor growth in vivo. In vitro experiments showed that overexpression of circ_0102543 significantly repressed the malignant behaviors of HCC cells, while co‐transfection of miR‐942‐5p partially attenuated these effects mediated by circ_0102543. In addition, SGTB knockdown increased the proliferation, migration, and invasion of HCC cells inhibited by miR‐942‐5p inhibitor. Mechanically, circ_0102543 regulated SGTB expression in HCC cells by sponging miR‐942‐5p. Conclusion Overexpression of circ_0102543 suppressed proliferation, migration, and invasion of HCC cells by regulating the miR‐942‐5p/SGTB axis, suggesting that circ_0102543/miR‐942‐5p/SGTB axis may be a potential therapeutic target for HCC

Large‐scale evidence for microbial response and associated carbon release after permafrost thaw

Permafrost thaw could trigger the release of greenhouse gases through microbial decomposition of the large quantities of carbon (C) stored within frozen soils. However, accurate evaluation of soil C emissions from thawing permafrost is still a big challenge, partly due to our inadequate understanding about the response of microbial communities and their linkage with soil C release upon permafrost thaw. Based on a large-scale permafrost sampling across 24 sites on the Tibetan Plateau, we employed meta-genomic technologies (GeoChip and Illumina MiSeq sequencing) to explore the impacts of permafrost thaw (permafrost samples were incubated for 11 days at 5 degrees C) on microbial taxonomic and functional communities, and then conducted a laboratory incubation to investigate the linkage of microbial taxonomic and functional diversity with soil C release after permafrost thaw. We found that bacterial and fungal alpha diversity decreased, but functional gene diversity and the normalized relative abundance of C degradation genes increased after permafrost thaw, reflecting the rapid microbial response to permafrost thaw. Moreover, both the microbial taxonomic and functional community structures differed between the thawed permafrost and formerly frozen soils. Furthermore, soil C release rate over five month incubation was associated with microbial functional diversity and C degradation gene abundances. By contrast, neither microbial taxonomic diversity nor community structure exhibited any significant effects on soil C release over the incubation period. These findings demonstrate that permafrost thaw could accelerate C emissions by altering the function potentials of microbial communities rather than taxonomic diversity, highlighting the crucial role of microbial functional genes in mediating the responses of permafrost C cycle to climate warming

Large-scale evidence for microbial response and associated carbon release after permafrost thaw

Permafrost thaw could trigger the release of greenhouse gases through microbial decomposition of the large quantities of carbon (C) stored within frozen soils. However, accurate evaluation of soil C emissions from thawing permafrost is still a big challenge, partly due to our inadequate understanding about the response of microbial communities and their linkage with soil C release upon permafrost thaw. Based on a large-scale permafrost sampling across 24 sites on the Tibetan Plateau, we employed meta-genomic technologies (GeoChip and Illumina MiSeq sequencing) to explore the impacts of permafrost thaw (permafrost samples were incubated for 11 days at 5 degrees C) on microbial taxonomic and functional communities, and then conducted a laboratory incubation to investigate the linkage of microbial taxonomic and functional diversity with soil C release after permafrost thaw. We found that bacterial and fungal alpha diversity decreased, but functional gene diversity and the normalized relative abundance of C degradation genes increased after permafrost thaw, reflecting the rapid microbial response to permafrost thaw. Moreover, both the microbial taxonomic and functional community structures differed between the thawed permafrost and formerly frozen soils. Furthermore, soil C release rate over five month incubation was associated with microbial functional diversity and C degradation gene abundances. By contrast, neither microbial taxonomic diversity nor community structure exhibited any significant effects on soil C release over the incubation period. These findings demonstrate that permafrost thaw could accelerate C emissions by altering the function potentials of microbial communities rather than taxonomic diversity, highlighting the crucial role of microbial functional genes in mediating the responses of permafrost C cycle to climate warming

Changes in above-/below-ground biodiversity and plant functional composition mediate soil respiration response to nitrogen input

1. Biodiversity loss and changes in plant community composition induced by anthropogenic nitrogen (N) deposition exert profound effects on ecosystem functions. However, limited studies have considered the joint effects of plant community composition, plant species richness, plant functional diversity and soil biodiversity on the dynamics of soil autotrophic and heterotrophic respiration under extra N input. 2. We addressed this issue by conducting a multilevel N-manipulation experiment in a Tibetan alpine steppe. Based on soil respiration observations as well as biotic and abiotic measurements under this N addition experiment, we quantified the relative and interactive effects of above-/below-ground biodiversity, plant community composition and other explanatory variables (environmental factors, plant and microbial properties) on autotrophic and heterotrophic respiration. 3. Our results showed that the effects of N enrichment via plant productivity, root amount, the proportion of sedge biomass and plant functional diversity explained 71% of the N-induced variations in autotrophic respiration. With regard to heterotrophic respiration, the combination of N addition, soil pH, plant functional diversity and soil biota diversity accounted for 78% of its variations along the N addition gradient. Further analyses showed that above-/below-ground diversity loss and changes in plant community composition explained similar variation to that contributed by other factors in both autotrophic and heterotrophic respiration. The declined plant functional diversity and the increased proportion of sedge biomass promoted autotrophic respiration. Conversely, the loss of soil biodiversity together with the decreased plant functional diversity led to the decline of heterotrophic respiration along the experimental N gradient. 4. Our results highlight that the indirect regulation of N input on ecosystem function through changes in plant community composition and above-/below-ground biodiversity loss should be considered for better understanding the responses of terrestrial ecosystems to atmospheric N deposition

Above- and below-ground resource acquisition strategies determine plant species responses to nitrogen enrichment

Background and Aims: Knowledge of plant resource acquisition strategies is crucial for understanding the mechanisms mediating the responses of ecosystems to external nitrogen (N) input. However, few studies have considered the joint effects of above-ground (light) and below-ground (nutrient) resource acquisition strategies in regulating plant species responses to N enrichment. Here, we quantified the effects of light and non-N nutrient acquisition capacities on species relative abundance in the case of extra N input. Methods: Based on an N-manipulation experiment in a Tibetan alpine steppe, we determined the responses of species relative abundances and light and nutrient acquisition capacities to N enrichment for two species with different resource acquisition strategies (the taller Stipa purpurea, which is colonized by arbuscular mycorrhizal fungi, and the shorter Carex stenophylloides, which has cluster roots). Structural equation models were developed to explore the relative effects of light and nutrient acquisition on species relative abundance along the N addition gradient. Key Results: We found that the relative abundance of taller S. purpurea increased with the improved light acquisition along the N addition gradient. In contrast, the shorter C. stenophylloides, with cluster roots, excelled in acquiring phosphorus (P) so as to elevate its leaf P concentration under N enrichment by producing large amounts of carboxylate exudates that mobilized moderately labile and recalcitrant soil P forms. The increased leaf P concentration of C. stenophylloides enhanced its light use efficiency and promoted its relative abundance even in the shade of taller competitors. Conclusions: Our findings highlight that the combined effects of above-ground (light) and below-ground (nutrient) resources rather than light alone (the prevailing perspective) determine the responses of grassland community structure to N enrichment

Data from: Trait identity and functional diversity co-drive response of ecosystem productivity to nitrogen enrichment

1. Exploring the mechanisms underlying the change in ecosystem productivity under anthropogenic nitrogen (N) inputs is of fundamental ecological interest. It has been proposed that functional traits, environmental factors, and species richness are central drivers linking ecosystem productivity with environmental change. However, few studies have considered the joint effects of functional traits, environmental factors, and species richness on ecosystem productivity under increasing N inputs. 2. We established a N-manipulation experiment in a Tibetan alpine steppe in 2013. Using structural equation models, we assessed the effects of N-induced changes in environmental factors, species richness, and trait metrics (the mean, variance, skewness and kurtosis of trait distribution) on gross ecosystem productivity as well as three resource use efficiencies (water, light, and phosphorus (P) use efficiencies), based on measurements during the peak growing season in 2016. 3. We found that both light and P use efficiencies decreased under N enrichment, largely due to the N-induced decline in functional diversity of leaf P concentration. However, both gross ecosystem productivity and water use efficiency exhibited initial increases and subsequent slight decreases with N addition. These nonlinear patterns were closely associated with both the increased morphological trait (i.e., mean-leaf area) and decreased diversity of leaf P concentration. 4. Synthesis. Our results illustrate how N-induced changes in functional traits may have dual effects on ecosystem productivity: the stimulating effects of the dominant trait identity via increasing canopy light interception vs. the inhibiting effect of decreasing trait diversity via declining resource use efficiencies. Our results highlight the importance of including functional traits in land surface models to improve predictions of the response of ecosystem function to N inputs

Magnitude and Drivers of Potential Methane Oxidation and Production across the Tibetan Alpine Permafrost Region

Methane (CH4) dynamics across permafrost regions is critical in determining the magnitude and direction of permafrost carbon (C)-climate feedback. However, current studies are mainly derived from the Arctic area, with limited evidence from other permafrost regions. By combining large-scale laboratory incubation across 51 sampling sites with machine learning techniques and bootstrap analysis, here, we determined regional patterns and dominant drivers of CH4 oxidation potential in alpine steppe and meadow (CH4 sink areas) and CH4 production potential in swamp meadow (CH4 source areas) across the Tibetan alpine permafrost region. Our results showed that both CH4 oxidation potential (in alpine steppe and meadow) and CH4 production potential (in swamp meadow) exhibited large variability across various sampling sites, with the median value being 8.7, 9.6, and 11.5 ng g(-1) dry soil h(-1), respectively. Our results also revealed that methanotroph abundance and soil moisture were two dominant factors regulating CH4 oxidation potential, whereas CH4 production potential was mainly affected by methanogen abundance and the soil organic carbon content, with functional gene abundance acting as the best explaining variable. These results highlight the crucial role of microbes in regulating CH4 dynamics, which should be considered when predicting the permafrost C cycle under future climate scenarios