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Wildfire impacts on soil microbial community structure and functional activity have attracted a growing attention because of the higher sensitivity of soil microbes to wildfire. Soil extracellular enzymes play pivotal roles in biogeochemical processes, such as mediating carbon (C) and nutrient cycling. However, little is known about how post-fire changes in soil biogeochemical properties and microbial community composition affect soil extracellular enzyme activities. This study explored the responses and regulating factors of C-, nitrogen-(N), and phosphorus-(P) acquiring extracellular enzyme activities across a wildfire chronosequence (i.e., 1, 6, 13, and 50 years after fire) in subtropical–temperate ecotonal forests in Central China. The activities of C-(β-glucosidase), N-(N-acetylglucosaminidase), and P-(acid phosphatase) acquiring enzymes declined with time post-fire, with the highest values one-year post-fire. The response of C-acquiring enzyme activity to fire was positively correlated with bacterial biomass, suggesting that microbial compositions were related to post-fire changes in extracellular enzyme decomposition. The response of N-acquiring enzyme activity to fire was positively correlated with soil P availability, while P-acquiring enzyme activity was positively correlated with soil N availability. Overall, soil extracellular enzyme activity declined with time post-fire, suggesting wildfire may reduce microbial demand for nutrients over time. Future research is needed to elucidate fire impacts on microbial processes for nutrient-microbial-enzyme linkages.

Terrestrial species are predicted to migrate northward under global warming conditions, yet little is known about the direction and magnitude of change in microbial distribution patterns. In this continental-scale study with more than 1600 forest soil samples, we verify the existence of core microbiota and lump them into a manageable number of eco-clusters based on microbial habitat preferences. By projecting the abundance differences of eco-clusters between future and current climatic conditions, we observed the potential warming-driven migration of the core microbiota under warming, partially verified by a field warming experiment at Southwest China. Specifically, the species that favor low pH are potentially expanding and moving northward to medium-latitudes (25°–45°N), potentially implying that warm temperate forest would be under threat of soil acidification with warming. The eco-cluster of high-pH with high-annual mean temperature (AMT) experienced significant abundance increases at middle- (35°–45°N) to high-latitudes (> 45°N), especially under Representative Concentration Pathway (RCP) 8.5, likely resulting in northward expansion. Furthermore, the eco-cluster that favors low-soil organic carbon (SOC) was projected to increase under warming scenarios at low-latitudes ( 45°N) the changes in relative abundance of this eco-cluster is inversely related with the temperature variation trends, suggesting microbes-mediated soil organic carbon changes are more responsive to temperature variation in colder areas. These results have vital implications for the migration direction of microbial communities and its potential ecological consequences in future warming scenarios.

Soil inorganic carbon (SIC), including mainly carbonate, is a key component of terrestrial soil C pool. Autotrophic microorganisms can assimilate carbonate as the main or unique C source, how microorganisms convert SIC to soil organic carbon (SOC) remains unclear. A systematic field survey (n = 94) was performed to evaluate the shift in soil C components (i.e., SIC, SOC, and microbial residues) along a natural salinity gradient (ranging from 0.5 ‰ to 19 ‰), and further to explore how microbial necromass as an indicator converting SIC into SOC in the Yellow River delta. We observed that SIC levels linearly decreased with increasing salinity, ranging from ∼12 g kg−1 (salinity 6 ‰). Additionally, the concentrations of SOC and microbial residues exponentially decreased from salinity 6 ‰, with the decline of 39% and 70%, respectively. Microbial residues and SOC was tightly related to the variations in SIC. The structural equation model showed the causality on explanation of SOC variations with SIC through microbial residues, which can contribute 89% of the variance in SOC storage combined with SIC. Taken together, these two statistical analyses can support that microbial residues can serve as an indicator of SIC transition to SOC. This study highlights the regulation of microbial residues in SIC cycling, enhancing the role of SIC playing in C biogeochemical cycles and enriching organic C reservoirs in coastal saline soils.

The effects of different straw returning and nitrogen addition levels on soil quality are important for proper coastal saline soil remediation. Two maize/wheat straw returning levels (1.0 × 10 kg ha (2S) and 5.0 × 10 kg ha (S)) and three inorganic nitrogen addition levels (300 kg ha (N2), 150 kg ha (N) and 75 kg ha (N1/2))—were studied, with 150 kg ha inorganic nitrogen and without straw addition treatment as the control (CK), to elucidate the response of soil physical and chemical properties to the two factors. Dry-sieving technique was applied to fractionate the soils into silt-plus-clay particles (< 0.053 mm, CS), microaggregates (0.053–0.25 mm, MI), small macroaggregates (0.25–2.0 mm, SM), and large macroaggregates (> 2 mm, LM). After four consecutive wheat-maize cycles, different straw and N fertilizer treatments obviously decreased the salinity contents, increased the total nutrient contents, and optimized the soil structure of the saline soil. The saline soil reclamation effects showed significant distinctions among the different straw and N fertilizer treatments. The 2SN2 treatment displayed the greatest effects in regard to decreasing salinity, increasing the total soil nutrient contents and optimizing the soil structure, which resulted in the best remediation effect. Straw returning play a major role in decreasing soil salinity and enhancing saline soil aggregate formation. N fertilizer addition supplies rich nutrients for straw decomposition, and promotes soil microbial growth and reproduction, which brought about C sequestration in coastal saline soil. During the coastal saline soil remediation process in the Yellow River Delta, it is suggested to prioritize straw returning and moderate N fertilizer addition, and live together with moderate P fertilizer application.

We propose a novel heterogeneous nineteen-core four-mode fiber. The heterogeneous core arrangement and trench-assisted structure can significantly suppress inter-core crosstalk (XT). In order to control the number of modes in the core, a low refractive index area is introduced in the core. The number of LP modes and the effective refractive index difference (Δneff) of adjacent modes in the core are controlled by changing the refractive index distribution of the core and the parameters of the low refractive index area in the core. And the mode state of low intra-core crosstalk is successfully realized in the graded index core. After the optimization of fiber parameters, each core can stably transmit four LP modes under the optimal fiber parameters, and the inter-core crosstalk of LP02 mode is less than -60 dB/km. Finally, the effective mode area (Aeff) and dispersion (D) of nineteen-core four-mode fiber in C+L band are described. The results show that the nineteen-core four-mode fiber is suitable for terrestrial and undersea communication systems, data centers, optical sensors and other fields.

We propose a homogeneous five-mode twelve-core fiber with a trench-assisted structure, combining a low refractive index circle and a high refractive index ring (LCHR). The 12-core fiber utilizes the triangular lattice arrangement. The properties of the proposed fiber are simulated by the finite element method. The numerical result shows that the worst inter-core crosstalk (ICXT) can achieve at -40.14 dB/100 km, which is lower than the target value (-30 dB/100 km). Since adding the LCHR structure, the effective refractive index difference between LP21 and LP02 mode is 2.8 × 10−3, which illustrates that the LP21 and LP02 modes can be separated. In contrast to without the LCHR, the dispersion of LP01 mode has an apparent dropping, which is 0.16 ps/(nm·km) at 1550 nm. Moreover, the relative core multiplicity factor can reach 62.17, which indicates a large core density. The proposed fiber can be applied to the space division multiplexing system to enhance the fiber transmission channels and capacity.

Direct quantification of terrestrial biosphere responses to global change is crucial for projections of future climate change in Earth system models. Here, we synthesized ecosystem carbon-cycling data from 1,119 experiments performed over the past four decades concerning changes in temperature, precipitation, CO2 and nitrogen across major terrestrial vegetation types of the world. Most experiments manipulated single rather than multiple global change drivers in temperate ecosystems of the USA, Europe and China. The magnitudes of warming and elevated CO2 treatments were consistent with the ranges of future projections, whereas those of precipitation changes and nitrogen inputs often exceeded the projected ranges. Increases in global change drivers consistently accelerated, but decreased precipitation slowed down carbon-cycle processes. Nonlinear (including synergistic and antagonistic) effects among global change drivers were rare. Belowground carbon allocation responded negatively to increased precipitation and nitrogen addition and positively to decreased precipitation and elevated CO2. The sensitivities of carbon variables to multiple global change drivers depended on the background climate and ecosystem condition, suggesting that Earth system models should be evaluated using site-specific conditions for best uses of this large dataset. Together, this synthesis underscores an urgent need to explore the interactions among multiple global change drivers in under-represented regions such as semi-arid ecosystems, forests in the tropics and subtropics, and Arctic tundra when forecasting future terrestrial carbon-climate feedback. National Natural Science Foundation of ChinaNational Natural Science Foundation of China [31430015, 31830012]; US NSFNational Science Foundation (NSF) [DEB-0955771]; ClimMani COST actionEuropean Cooperation in Science and Technology (COST) [ES1308] We thank J. Wang (Hebei University), S. Yang (Institute of Botany, Chinese Academy of Sciences), L. Zhou (East China Normal University), C. Qiao (Xinyang Normal University) and H. Li (Henan University) for their help in meta-analyses and interaction analyses, and H. Li, Y. Liu (Institute of Tibetan Plateau Research, Chinese Academy of Sciences) and Y. He (Peking University) for their help in plotting figures. This work was financially supported by the National Natural Science Foundation of China (grant nos. 31430015 and 31830012). This study emerged from the INTERFACE Workshop in Beijing, China (https://www.bio.purdue.edu/INTERFACE/) supported by the US NSF DEB-0955771. We also acknowledge support from the ClimMani COST action (ES1308). Public domain – authored by a U.S. government employee

Soils store more carbon (C) belowground than plants and the atmosphere combined, providing a critical ecosystem service. While previous research has shown that sustainable forest management practices can increase soil C storage by enhancing plant productivity, the role of soil microbes remains elusive. We analyzed changes in plant litter, soil C, and microbial parameters across a reforestation chronosequence—with average stand ages of ∼20, 80, 120, 200 and ≥ 300 years—to evaluate how microbial communities mediate soil C transformation and sequestration. We observed generally consistent increases in microbial biomass (lipid biomarkers), microbial necromass (amino sugar biomarkers), and soil organic C with forest age, highlighting microbial regulation of soil C accumulation. Specifically, increases in microbial biomass preceded gains in soil C, suggesting microbial lipids are an early and sensitive indicator of ecosystem restoration. We also observed a rapid increase in microbial necromass relative to bulk soil C in forests restored for 80–200 years, likely due to accelerated microbial turnover rates. These patterns suggest high plant productivity (low litter C: N ratios) during the early and middle stages of reforestation facilitates efficient microbial growth and necromass accrual in SOC stocks. As forests age, the contribution of microbial necromass to the SOC pool declines toward background levels. Our results suggest reforestation offers a positive feedback solution that mitigates climate change by efficiently sequestering soil C belowground.

Soil microbes link aboveground and belowground ecosystem processes by modulating nutrient retention, recycling, and availability to plants. The diversity and abundance of soil microbes are influenced by biotic and edaphic factors such as plant communities and soil chemistry. Despite this general understanding, relatively few details are known about how soil microbial community structure responds to changing plant communities and soil chemistry associated with secondary forest succession. To address these gaps, we used 16S rRNA gene sequencing to investigate how diversity, composition and abundance of soil prokaryotic communities differed among five successional stages at two soil depths in a temperate forest, and then related these differences with soil properties. Oligotrophic prokaryotic taxa were more common in earlier successional stages, and community diversity declined at later forest successional stages. Prokaryotic diversity was consistently higher in topsoil than subsoil. Prokaryotic community composition varied with respect to soil organic matter (SOM) properties. The relative abundances of specific carbon (C) functional groups (e.g., aliphatic C groups, aromatic C groups and polysaccharides) revealed by mid-IR spectroscopy were strongly related with prokaryotic community composition. Overall, this study revealed that changes in soil prokaryotic community structure (diversity, composition and taxa abundance) paralleled changes in plant communities and soil chemistry associated with forest succession, and that these changes can be inferred through changes in SOM properties.

Seven-core five-mode fiber and single-core five-mode fiber with the same core structure by high and low refractive index double rings are prepared based on plasma chemical vapor deposition. The transmission characteristics of the single-core few-mode fiber and the seven-core few-mode fiber are measured and characterized by building an experimental platform. The prepared single-core few-mode fiber can stably transmit five LP modes at 1550 nm, which not only has low loss characteristics, but also has excellent bending resistance. Furthermore, the transmission loss of the prepared seven-core fiber is lower than 0.4 dB/km, and the inter-core crosstalk is lower than -50 dB/km, which realizes the high-density and low-crosstalk transmission of the multi-core fiber. The prepared seven-core few-mode fiber can solve the capacity limitation of single-mode fiber, which will contribute the development of future communication systems.

Microbial residues play important role in regulating soil carbon (C) turnover and stability, but the responses of microbial residues to climate change are neglected. In this study, a 5-year field experiment that simulated two climate change factors (precipitation and warming) was performed to examine microbial residue changes in a semiarid grassland, with water limitation. Both the contents of total amino sugars (a biomarker of microbial residues) and glucosamine (a biomarker of fungal residues) increased significantly with increased precipitation and decreased under warming, whereas neither increased precipitation nor warming influenced the content of muramic acid (a biomarker of bacterial residues). These findings clarified the role of fungal residues in determining the response of microbial residues to altered water availability and plant productivity induced by increased precipitation and elevated temperature. Interestingly, microbial residues had a much greater response to climate change than total soil C, implying that soil C composition and stability altered prior to soil C storage and simultaneously slowed down the change of soil C pool. Integrating microbial residues into current climate-C models is expected to enable the models to more accurately evaluate soil C responses to climate regimes in semiarid grasslands.

Modern Yellow River Delta (MYRD) is a typical petrochemical and agricultural industrial area of China. To effectively assess the current status of the four heavy metals (Cr, Pb, Ni and Cd) of topsoil residues, soil samples (0 ~ 20 cm) (n = 104) in the MYRD were collected and analyzed. The results showed that the contents of the four heavy metals were all below or equal to the level 1 background content as specified in the National Environmental Quality Standard for Soils, while the content of Cd and Pb were 1.68 and 1.41 times higher than the background value of soil in Shandong province, respectively. The difference of four heavy metal contents between different kinds of land types existed. Geoaccumulation index and potential ecological risk index methods were used to evaluate the risk of the four heavy metal pollution in the MYRD. The results showed that there was a light or moderate pollution of heavy metals Cd and Pb, which were a strong ecological hazard. Therefore, it is necessary to enhance the monitoring and controlling of heavy metal Cd and Pb pollution in the MYRD.

We propose a heterogeneous 13-core few-mode fiber, which is characterized by the combination of a high refractive index ring and a trench. All cores of the optical fiber can stably transmit L P 01 , L P 11 , L P 21 , and L P 02 modes in the C + L band through structural optimization and numerical analysis. The effective refractive index difference of the L P 21 and L P 02 modes reaches 2 × 10 − 3 , which is conducive to the independent transmission of modes. The trench can effectively suppress the inter-core cross talk below − 50 d B / k m at 1550 nm. The proposed few-mode multi-core fiber is conducive to solving the long-distance signal transmission problem of large capacity and low cross talk in future optical communication systems.

Numerous ecosystem manipulative experiments have been conducted since 1970/80 s to elucidate responses of terrestrial carbon cycling to the changing atmospheric composition (CO2 enrichment and nitrogen deposition) and climate (warming and changing precipitation regimes), which is crucial for model projection and mitigation of future global change effects. Here, we extract data from 2,242 publications that report global change manipulative experiments and build a comprehensive global database with 5,213 pairs of samples for plant production (productivity, biomass, and litter mass) and ecosystem carbon exchange (gross and net ecosystem productivity as well as ecosystem and soil respiration). Information on climate characteristics and vegetation types of experimental sites as well as experimental facilities and manipulation magnitudes subjected to manipulative experiments are also included in this database. This global database can facilitate the estimation of response and sensitivity of key terrestrial carbon-cycling variables under future global change scenarios, and improve the robust projection of global change‒terrestrial carbon feedbacks imposed by Earth System Models., Measurement(s) organic material • plant production • carbon exchange Technology Type(s) digital curation Factor Type(s) climate characteristics • vegetation traits Sample Characteristic - Environment climate system Sample Characteristic - Location global Machine-accessible metadata file describing the reported data: 10.6084/m9.figshare.12932843

Although autotrophic or chemotrophic microorganisms can assimilate CO2 or carbonate, it is still unclear how microorganisms convert soil inorganic carbon (SIC) to organic carbon (SOC), owing to the lack of a microbial indicator between SIC and SOC. Herein, we hypothesized that carbonate-rich saline soils are a potential source that contribute to the SOC pool through the transformation of microbial necromass. SIC levels linearly decreased with an increase in salinity, while SOC and microbial residues exponentially declined. A structural equation model verified the causality of SIC-microbial residues-SOC, suggesting that microbial residues can serve as an indicator of SIC transition to SOC. This study highlights the regulation of microbial necromass in SIC cycling, thus enhancing the application of SIC for C biogeochemical cycles and enriching organic C reservoirs in global saline or dry lands.

Microbial residues play a significant role in the formation of soil organic matter (SOM), but it is not clear how microbial traits influence residue accrual and SOM persistence. By pairing microbial biomarker and genomics approaches, we tested whether microbial life history strategies and residue accrual differed between primary (~70-year-old) and secondary (~30-year-old) subtropical forests. We found that microbial residue concentrations were significantly higher in secondary than primary forests, and strongly associated with several abundant microbial taxa (Ascomycota, Proteobacteria, Gemmatimonadetes). Microbial communities inhabiting resource-rich secondary forests were also associated with high growth yields and soil organic carbon (SOC) accrual (through residue retention), while nutrient-limited primary forests were dominated by microorganisms employing resource-acquisition strategies. We therefore suggest microbial life history traits can be used to link microbial community composition and metabolic processes with the turnover and transformation of SOC.

Soil salinization and nutrient deficiency have emerged as the major factors negatively impacting soil quality and primary productivity in the coastal saline-alkali soil of the Yellow River Delta. Biochar has been proposed as an efficient strategy for promoting plant growth and restoring degraded saline-alkali soil. However, knowledge is inadequate regarding the effects of adding Spartina alterniflora-derived biochar alone or in combination with effective microorganisms (EM) on the growth of Sesbania cannabina and soil quality in saline-alkali soil. To enhance this knowledge, a pot experiment with different EM treatments (without EM addition, EM-; with EM addition, EM+) and a gradient of biochar treatments (0%, B0; 0.5%, B1; 1.5%, B2; and 3%, B3; biochar weight/soil weight) was conducted. Our results showed that biochar addition alone and in combination with EM significantly increased seed germination, plant height, stem diameter, total biomass and plant nutrient uptake of S. cannabina. Biochar addition, EM addition and their interaction significantly decreased soil salt content efficiently and increased soil total carbon (TC), total nitrogen (TN), available phosphorus (AP) and available potassium (AK) but had little effect on soil pH. Biochar addition increased soil organic carbon, soil NH4+ and NO3−, microbial biomass carbon, and soil enzyme activities and these effects increased in strength when biochar and EM were present simultaneously. Of the treatments, the EM + B3 treatment had the largest effects in terms of inhibiting salinization, increasing soil fertility, elevating soil nutrients and enzyme activities, and improving plant growth. Moreover, the application of biochar and EM promoted the growth of S. cannabina by enhancing plant nutrient uptake, improving soil fertility (e.g., TN, AP, AK, NH4+ and NO3−), and elevating soil enzyme activities (urease and alkaline phosphatase activity). Overall, the integrated use of an appropriate biochar rate (3%) and EM for coastal saline-alkali soil could be an effective strategy to ameliorate soil salinity, improve soil quality and promote plant productivity.

Rhizosheaths are frequently found in arid and semiarid ecosystems, but their impacts on root decomposition rates and associated carbon (C) and nutrient fluxes remain unclear. We investigated mass, C and nitrogen (N) loss for the roots of Stipa krylovii and Carex korshinskii; the roots were exposed to rhizosheaths, bulk soil, or no soil in litterbags during a 102-d short-term decomposition experiment. Compared with no soil addition, rhizosheath addition increased the mass loss by 39% for S. krylovii, a sheath-forming grass, and by 11% for C. korshinskii, a non-sheath-forming grass. Rhizosheath addition also increased root C loss by 39% and N loss by 41% for S. krylovii but did not significantly alter root C or N loss for C. korshinskii, which may be due to a “home-field advantage” effect. In contrast, bulk soil addition did not alter mass, C, or N loss for either plant species, possibly because bulk soils contained fewer nutrients (C, N, and phosphorus) than rhizosheaths. We demonstrate for the first time that conventional root decomposition studies that do not account for rhizosheaths will underestimate the root mass, C and N loss by >20% in semiarid grasslands. Future studies should emphasize the crucial yet unappreciated role of rhizosheaths in driving soil organic matter cycling.

It is predicted that locust outbreaks will occur more frequently under future climate change scenarios, with consequent effects on ecological goods and services. A field manipulative experiment was conducted to examine the responses of gross ecosystem productivity (GEP), net ecosystem carbon dioxide (CO2) exchange (NEE), ecosystem respiration (ER), and soil respiration (SR) to locust outbreaks in a temperate steppe of northern China from 2010 to 2011. Two processes related to locust outbreaks, natural locust feeding and carcass deposition, were mimicked by clipping 80 % of aboveground biomass and adding locust carcasses, respectively. Ecosystem carbon (C) exchange (i.e., GEP, NEE, ER, and SR) was suppressed by locust feeding in 2010, but stimulated by locust carcass deposition in both years (except SR in 2011). Experimental locust outbreaks (i.e., clipping plus locust carcass addition) decreased GEP and NEE in 2010 whereas they increased GEP, NEE, and ER in 2011, leading to neutral changes in GEP, NEE, and SR across the 2 years. The responses of ecosystem C exchange could have been due to the changes in soil ammonium nitrogen, community cover, and aboveground net primary productivity. Our findings of the transient and neutral changes in ecosystem C cycling under locust outbreaks highlight the importance of resistance, resilience, and stability of the temperate steppe in maintaining reliable ecosystem services, and facilitate the projections of ecosystem functioning in response to natural disturbance and climate change.

Understanding soil CO2 flux temperature sensitivity (Q10) is critical for predicting ecosystem-level responses to climate change. Yet, the effects of warming on microbial CO2 respiration still remain poorly understood under current Earth system models, partly as a result of thermal acclimation of organic matter decomposition. We conducted a 117-day incubation experiment under constant and diurnally varying temperature treatments based on four forest soils varying in vegetation stand and soil horizon. Our results showed that Q10 was greater under varying than constant temperature regimes. This distinction was most likely attributed to differences in the depletion of available carbon between constant high and varying high-temperature treatments, resulting in significantly higher rates of heterotrophic respiration in the varying high-temperature regime. Based on 16S rRNA gene sequencing data using Illumina, the varying high-temperature regime harbored higher prokaryotic alpha-diversity, was more dominated by the copiotrophic strategists and sustained a distinct community composition, in comparison to the constant-high treatment. We found a tightly coupled relationship between Q10 and microbial trophic guilds: the copiotrophic prokaryotes responded positively with high Q10 values, while the oligotrophs showed a negative response. Effects of vegetation stand and soil horizon consistently supported that the copiotrophic vs oligotrophic strategists determine the thermal sensitivity of CO2 flux. Our observations suggest that incorporating prokaryotic functional traits, such as shifts between copiotrophy and oligotrophy, is fundamental to our understanding of thermal acclimation of microbially mediated soil organic carbon cycling. Inclusion of microbial functional shifts may provide the potential to improve our projections of responses in microbial community and CO2 efflux to a changing environment in forest ecosystems.