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Conversion of slope cropland to perennial vegetation has a significant impact on soil organic carbon (SOC) stock in A horizon. However, the impact on SOC and its fraction stratification is still poorly understood in deep soil in Loess Hilly Region (LHR) of China. Samples were collected from three typical conversion lands, Robinia psendoacacia (RP), Caragana Korshinskii Kom (CK), and abandoned land (AB), which have been converted from slope croplands (SC) for 30 years in LHR. Contents of SOC, total nitrogen (TN), particulate organic carbon (POC), and labile organic carbon (LOC), and their stratification ratios (SR) and carbon management indexes (CMI) were determined on soil profiles from 0 to 200 cm. Results showed that the SOC, TN, POC and LOC stocks of RP were significantly higher than that of SC in soil layers of 0–10, 10–40, 40–100 and 100–200 cm (P<0.05). Soil layer of 100–200 cm accounted for 27.38–36.62%, 25.10–32.91%, 21.59–31.69% and 21.08–26.83% to SOC, TN, POC and LOC stocks in lands of RP, CK and AB. SR values were >2.0 in most cases of RP, CK and AB. Moreover, CMI values of RP, CK, and AB increased by 11.61–61.53% in soil layer of 100–200 cm compared with SC. Significant positive correlations between SOC stocks and CMI or SR values of both surface soil and deep soil layers indicated that they were suitable indicators for soil quality and carbon changes evaluation. The Grain-to-Green Program (GTGP) had strong influence on improving quantity and activity of SOC pool through all soil layers of converted lands, and deep soil organic carbon should be considered in C cycle induced by GTGP. It was concluded that converting slope croplands to RP forestlands was the most efficient way for sequestering C in LHR soils. [ABSTRACT FROM AUTHOR]

Abstract: To investigate the feasibility of statistical methods in optimizing the feeding composition in anaerobic co-digestion, a simplex-centroid mixture design (SCMD) and central composite design (CCD) were evaluated with methane potential as the response variable. Dairy manure, chicken manure, swine manure and rice straw (RS) were selected as raw materials and two kinds of manures and RS were mixed in each blend. Each component served as an independent variable in the SCMD and CCD and involved two factors, the manure and C/N ratios. Co-digestion of three-component substrates resulted in higher methane potentials than single and two-component substrates. In response surface plots, SCMD showed the interactions among each component in the co-substrates and CCD presented the interaction between the ratio of manures and the C/N ratio. SCMD and CCD are both suitable methods for optimizing the feeding composition during anaerobic co-digestion. [Copyright &y& Elsevier]

Abstract: This study investigated the possibilities of improving methane yield from anaerobic digestion of multi-component substrates, using a mixture of dairy manure (DM), chicken manure (CM) and wheat straw (WS), based on optimized feeding composition and the C/N ratio. Co-digestion of DM, CM and WS performed better in methane potential than individual digestion. A larger synergetic effect in co-digestion of DM, CM and WS was found than in mixtures of single manures with WS. As the C/N ratio increased, methane potential initially increased and then declined. C/N ratios of 25:1 and 30:1 had better digestion performance with stable pH and low concentrations of total ammonium nitrogen and free NH3. Maximum methane potential was achieved with DM/CM of 40.3:59.7 and a C/N ratio of 27.2:1 after optimization using response surface methodology. The results suggested that better performance of anaerobic co-digestion can be fulfilled by optimizing feeding composition and the C/N ratio. [Copyright &y& Elsevier]

Abstract: As a renewable energy, biogas is not only an important part of the development of rural new energy, but also an important aspect of sustainable development in China. The development process and present status of household biogas, specifically the opportunities and constraints of household biogas in rural China, are discussed in this paper. Only about 19% of the biogas potential has been utilized in rural China. There are several opportunities for household biogas development in rural China, including the problem of rural household energy consumption, the availability of biogas fermentation materials, national financial subsidies, legal and international clean development mechanisms. Also, more research needs to be done in straw fermentation and cold fermentation technology. Training should be conducted to raise the level of biogas customers in comprehensive biogas utilization. Measures should be taken to improve the follow-up services and management of biogas plants. The information presented in this paper will be helpful not only to the sustainable development of household biogas in rural China, but also to the development of biogas in similar countries around the world. [Copyright &y& Elsevier]

Straw retention and wheat-soybean rotation play critical role in maintaining soil quality. However, the correlation between bacterial diversity and community structure, and soil nutrients is unknown, and a systematic understanding of their responses to straw retention is lacking. In the field experiment, the straw retention treatments included no straw (NS), half straw (HS), and total straw (TS) retention during long-term wheat-soybean rotation. The mean contents of soil total nitrogen (TN), nitrate-N (NO3−-N), and microbial biomass nitrogen (MBN) increased by 15.06%, 21.10%, and 38.23%, respectively, with straw retention relative to NS, while that of ammonium-N (NH4+-N) reduced by 3.68%. The concentration of carbon components increased as straw retention increased. The levels of soil dissolved organic carbon (DOC), microbial biomass carbon (MBC), and soil organic carbon (SOC) increased by 4.34%, 7.63%, and 9.34%, respectively, with straw retention relative to NS. Soil bacterial alpha diversity was reduced with straw retention. Soil pH and nutrient content were identified as the main factors affecting the soil microbial diversity and structure at the phylum level. Accordingly, straw retention and soybean-wheat rotation enable sustainable agriculture in the dryland of northern China. [ABSTRACT FROM AUTHOR]

In the agroforestry system, the organic matter in the farmland and natural ecosystem enters the farmland soil in a mixed form to improve soil fertility and carbon pool quality. However, it is unclear how soil microbial carbon-degrading enzyme activity responds to carbon dynamics in this process. Therefore, we took farmland in the Loess Plateau as the research object, combining the application of corn straw and Robinia pseudoacacia leaves in a mass ratio of 4:0, 3:1, 2:2, 1:3, and 0:4 for returning to the field. We measured corn grain yield, carbon emission, organic carbon pool component content, and carbon-degrading enzyme activity of the farmland. The results showed that combining corn straw and Robinia pseudoacacia leaves had a significant impact on soil organic carbon components (readily oxidizable organic carbon and recalcitrant organic carbon), carbon-degrading enzymes (polyphenol oxidase, peroxidase, and cellobiohydrolase), and cumulative carbon emissions. The trend of different indicators in different treatments during the corn growth period was similar. We found that soil carbon emissions were closely related to ROC and soil oxidase activity, while soil carbon content was closely related to soil hydrolase activity. Compared to not returning straw to the field, the corn straw and Robinia pseudoacacia leaves returned to the field in a mass ratio of 1:3(Y1C3) can increase corn grain yield by 32.04%. The Y1C3 treatment has the highest soil carbon content and the lowest crop carbon emission efficiency. Soil water content plays a crucial role in the process of carbon pool transformation driven by soil carbon-degrading enzymes. In conclusion, soil carbon dynamics are closely related to the activity of soil carbon-degrading enzymes. Combining the application of corn straw and Robinia pseudoacacia leaves may be a more suitable farming measure for fragile habitats in the Loess Plateau than other solutions. [ABSTRACT FROM AUTHOR]

Altered precipitation regimes have a great impact on global climate change, with potentially important effects on below-ground carbon dynamics. Soil microbes and carbon (C)-degrading extracellular enzymes activities (EEAs) are considered as the rate-limiting step in C decomposition. However, the effect of altered precipitation on the microbial biomass, microbial EEAs, and mechanism for soil C dynamics has not been established. In current study, we synthesized the responses of microbial biomass, C-degrading EEAs, soil organic carbon (SOC), dissolved organic carbon (DOC), and soil respiration (SR) to altered precipitation from 70 published studies. The results showed that increased precipitation significantly enhanced soil microbial biomass and oxidative C-degrading EEAs (Ox-EEAs) by 16.18% and 6.58%, respectively, but had no effects on hydrolytic C-degrading EEAs (Hy-EEAs). Decreased precipitation led to a significant decline of soil microbial biomass and Ox-EEAs by 11.61% and 10.99%, respectively; however, Hy-EEAs increased by 25.79%. Furthermore, increased precipitation stimulated soil microbial biomass in shrub and grassland but had no effects in forest, while decreased precipitation repressed soil microbial biomass but increased Hy-EEAs in forest. The response ratios (RRs) of microbial biomass to altered precipitation were negatively correlated with the mean annual precipitation (MAP) and mean annual temperature (MAT); however, the RRs of Hy-EEAs were positively correlated with MAP. Particularly, in low MAP (≤600 mm), increased precipitation significantly increased soil microbial biomass by 21.40% but decreased precipitation did not affect soil microbial biomass; In contrast, in high MAP (>600 mm), decreased precipitation significantly declined soil microbial biomass by 15.37%, and significantly increased Hy-EEAs by 29.31% but increased precipitation did not affect both of them. Moreover, the RRs of microbial biomass and Ox-EEAs were significantly correlated with SOC, DOC, and SR; however, we only observed a negative relationship between RRs of Hy-EEAs and RRs of SOC, suggesting the concurrent responses of microbial biomass and C-degrading EEAs for below-ground C dynamics under simulated precipitation changes, and that a large amount of recalcitrant C in the soils would be highly susceptible to changing precipitation. [ABSTRACT FROM AUTHOR]

Anaerobic digestion is a technology that converts complex organic matter into another form of matter, from which energy can be more easily extracted. The stability and digestion of anaerobic co‐digestion with multiple raw materials as substrates is better than the performance of anaerobic mono‐digestion. In the past two decades, there has been a large amount of literature on how to improve the performance of methane production in the anaerobic co‐digestion process, but few systematic reviews have been conducted. This paper summarizes the factors affecting the development of anaerobic co‐digestion. The process parameters, substrate optimization strategy, microbial community, and model application for improving anaerobic co‐digestion performance were systematically analyzed. Methane purification technology and policies to support digestion projects are also discussed. At present, the technological process is basically mature, but the interaction between various parameters can be studied in depth. Methane purification technology expands the market for the biogas industry and increases its economic benefits. Policy is the key to promoting process technology and the methane market. © 2022 Society of Chemical Industry and John Wiley & Sons, Ltd [ABSTRACT FROM AUTHOR]

Aim: Fresh carbon (C) inputs to the soil can have important consequences for the decomposition rates of soil organic matter (priming effect), thereby impacting the delicate global C balance at the soil–atmosphere interface. Yet, the environmental factors that control soil priming effect intensity remain poorly understood at a global scale. Location: Global. Time period: 1980–2020. Major taxa studied: Soil priming effect intensity. Methods: We conducted a global dataset of CO2 effluxes in 711 pairwise soils with 13C or 14C simple C sources inputs and without C inputs from incubation experiments in which isotope‐labelled C was used to quantify fresh C‐induced rather than exudate‐induced priming. Results: Soil priming effect intensity is predominantly positive. Soil texture and C content were identified as the most important factors associated with priming effects, with sandy soils from tropical and mid‐latitudes supporting the highest soil priming effect intensity, and soils with greater C content and fine textures from high latitudes maintaining the lowest soil priming effects. The negative association between C content and soil priming effect intensity was also indirectly driven by changing mean annual temperature, net primary productivity, and fungi : bacteria ratio. Using this information, we generated a global map of soil priming effect intensity, and found that the priming was lower at high latitudes and higher at lower latitudes. Main conclusions: Global patterns of soil priming effect intensity can be predicted using environmental data, with soil texture and C content playing a predominant role in explaining in priming effects. These effects were also indirectly driven by climate, vegetation and soil microbial properties. We present the first global atlas of soil priming effect intensity and advance our knowledge on the potential mechanisms underlying soil priming effect intensity, which are integral to improving the climate change and soil C dynamics components of Earth System models. [ABSTRACT FROM AUTHOR]

In order to provide a clear guidance for biogas development in rural China, the progress and current status of rural biogas, critical factors influencing biogas development in rural areas, and probable biogas transformations are discussed in this paper. Rural biogas in China experiences rapid development in the past fifteen years and subsidies and policies from Chinese government are two main driving forces for promoting this development. For the recent days, the growth rate of household biogas decreased and that of Medium-to-large biogas projects (MLBPs) obviously increased. Several surveys showed that the utilization rate of household biogas greatly decreased and more and more digesters were discontinued. The underlying reasons for these changes come from the development of large-scale livestock farms, agricultural modernization and urbanization, which deeply affect the agricultural and social environment in rural China. The development of these agricultural and social factors all create positive conditions for MLBPs, but they negatively affect household biogas projects in terms of biomass supply and their participation in modern agricultural processes. Ongoing transformations and developments in local agriculture and rural society significantly influence the patterns of biogas projects. For future biogas development, MLBPs should be encouraged and the reduction of household biogas projects should be allowed to continue. However, recommendations on probable biogas development transformations suggest that the decision for expanding or abandoning the household projects in certain regions should be consistent with the developments and trends of local agriculture and society. For MLBPs, suitable developing models and reasonable operating mechanisms should be fully considered for assuring their benefits and continuous operation. [ABSTRACT FROM AUTHOR]

Artificial forest restoration is widely recognized as a crucial approach to enhance the potential of soil carbon sequestration. Nevertheless, there is still limited understanding regarding the dynamics of aggregate organic carbon (OC) and the underlying mechanisms driving these dynamics after artificial forest restoration. To address this gap, we studied Pinus tabuliformis forests and adjacent farmland in three recovery periods (13, 24 and 33 years) in the Loess Plateau region. Samples of undisturbed soil from the surface layer were collected and divided into three aggregate sizes: >2 mm (large aggregate), 0.25–2 mm (medium aggregate), and <0.25 mm (small aggregate). The aim was to examine the distribution of OC and changes in enzyme activity within each aggregate size. The findings revealed a significant increase in OC content for all aggregate sizes following the restoration of Pinus tabuliformis forests. After 33 years of recovery, the OC of large aggregates, medium aggregates and micro-aggregates increased by (30.23 ± 9.85)%, (36.71 ± 21.60)% and (37.88 ± 16.07)% respectively compared with that of farmland. Moreover, the restoration of Pinus tabuliformis forests lead to increased activity of hydrolytic enzymes and decreased activity of oxidative enzymes. It is noteworthy that the regulation of carbon in all aggregates is influenced by soil P-limitation. In large aggregates, P-limitation promotes the enhancement of hydrolytic enzyme activity, thereby facilitate OC accumulation. Conversely, in medium and small aggregates, P-limitation inhibits the increase in oxidative enzyme activity, resulting in OC accumulation. The results emphasize the importance of P-limitation in regulating OC accumulation during the restoration of Pinus tabulaeformis forest, in which large aggregates play a leading role. • The Pinus tabuliformis forest restoration has increased the OC content of soil aggregates. • The Pinus tabuliformis forest restoration has increased the OC contribution rate of soil large aggregates. • The restoration of Pinus tabuliformis forest enhanced hydrolase activity while reducing oxidase activity. • The OC of aggregates of different sizes is regulated by P-limitation. [ABSTRACT FROM AUTHOR]

Straw incorporation with half-plastic film mulch is a promising approach for enhancing soil quality in dryland farming. However, its effects on soil greenhouse gas (GHG) and NH 3 emissions remain poorly understood. This study aims to optimize the mulch practice to balance the plastic film input with comprehensive benefits and examine the temporal dynamics and influencing factors of soil GHG and NH 3 emissions. A 3-year field experiment was conducted in a wheat-maize cropping system in north-western China with a complete randomized design including three treatments replicated thrice: (a) no straw incorporation or half-plastic film mulch (CT), (b) straw incorporation without half-plastic film mulch (S), and (c) straw incorporation with half-plastic film mulch (SP). The study revealed that S treatment significantly enhanced crop yield and soil cumulative N 2 O, CO 2 , and NH 3 emissions during the maize season by 8.26%, 113.51%, 31.78%, and 64.92%, respectively, compared to CT treatment. SP treatment significantly decreased N 2 O and NH 3 emissions by 30.66% and 23.74%, respectively, and slightly stimulated CO 2 emissions by 8.73% relative to S treatment throughout the three maize seasons. The average maize yield gap between S and SP treatments ranged from 517 to 800 kg ha−1. N 2 O and NH 3 emissions were significantly associated with soil water content (SWC), soil N components, and enzyme activity (nitrate and nitrite reductase), whereas CO 2 emissions were significantly influenced by soil temperature. Compared with S treatment, half-plastic film mulch increased SWC (16.77%), reduced soil N content and inhibited activity of nitrate (12.15%) and nitrite reductase (8.40%), eventually mitigated straw incorporation-induced N 2 O and NH 3 emissions by 30.66% and 23.74%, respectively. Overall, we demonstrated that straw incorporation with half-plastic film mulch is an innovative practice for enhancing the sustainability of dryland farming by increasing maize yield and mitigating N 2 O and NH 3 emissions. [Display omitted] • Nitrogen cycle- related enzyme activities are key to regulating gas emissions. • S significantly increased N 2 O, CO 2 , and NH 3 emissions compared with CT. • SP significantly reduced N 2 O and NH 3 emissions and increased yield compared to S. • SP is an innovative practice for promoting the sustainability of dryland farming. [ABSTRACT FROM AUTHOR]

• Straw return and fertilization improve the soil nutrient status. • Straw return with nitrogen fertilizer reduced soil CO 2 emissions by 270.01%, compared with straw return. • Enzyme stoichiometry showed that soil microorganisms of winter wheat were carbon and nitrogen limited under straw-return conditions. • Microorganisms use their stoichiometric flexibility to regulate soil CO 2 emissions. Straw return is the key measure of green agricultural production. Nitrogen (N) and phosphorus (P) play pivotal roles in crop growth and carbon (C) cycling in agroecosystems. However, the mechanism of soil CO 2 emissions and enzyme stoichiometry regulation by straw return with N and P application remain unknown. Therefore, this study is aimed to use enzyme stoichiometry to investigate the effects of straw return with N and P fertilizer application on soil CO 2 emissions, enzyme activity, and microbial nutrient limitation through a two-year field experiment. A split-plot experimental design was used (straw as the main plot and fertilizer as the sub plot). The results indicated that the addition of N, P (SNP) increased CO 2 emissions by 25.54 %, and N application (SN) reduced CO 2 emissions by 27.01 %, compared with straw return (SW). Enzyme stoichiometry indicated that straw return with N and P application exhibited significant C and N limitations. In soil nutrients and nutrient stoichiometry, compared with the S 0 W treatment, straw return with fertilizer (SNP, SN) significantly increased microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), dissolved organic carbon (DOC) and dissolved organic nitrogen (DON); SNP treatment increased β-1,4- n −acetylaminoglucosidase (NAG) enzyme activity by 53.72 %, increased l −leucine aminopeptidase (LAP) enzyme activity by 58.11 %, and increased one P-acquiring enzyme alkaline monoalkaline phosphatase (AKP) enzyme activity by 39.49 % (P < 0.05). Structural equation modeling suggested that straw return and fertilization can influence microbial biomass phosphorus (MBP) and vector length (VL) by affecting MBN, which, in turn, affects CO 2 emissions. Soil microbes regulate CO 2 emissions using stoichiometric flexibility to maintain a stoichiometric balance of nutrients and microbes. Therefore, straw return with N and P fertilizers to winter wheat soils can meet the requirements of microbial stoichiometry, modulate microbial and extracellular enzyme activities, and effectively regulate CO 2 emissions and resource limitations. [ABSTRACT FROM AUTHOR]

To alleviate pollution and promote clean energy production, food waste can be used to produce methane through anaerobic digestion (AD). In this study, wheat straw was used to produce biochar (BC) and magnetic biochar (MB) as additives for AD of food waste. MB2.5% and BC2.5% led to the highest methane production. The main action mechanism of the additives in AD was the change in environmental factors upon stimulating microorganisms to rapidly metabolize volatile fatty acids. The stimulation of microbial function increased the abundance of the methanogenesis pathways. Methanosarcina was the most dominant archaea in the four methanogenesis modules, and the microbial community changed more clearly with time than with treatment. This study is innovative in finding the effectiveness of BC and MB treatments attributed to the abundance of methanogenesis modules, especially MB2.5% treatment retained its advantage until the later stage of digestion in AD process. [ABSTRACT FROM AUTHOR]

Soil priming is a microbial‐driven process, which determines key soil–climate feedbacks in response to fresh carbon inputs. Despite its importance, the microbial traits behind this process are largely undetermined. Knowledge of the role of these traits is integral to advance our understanding of how soil microbes regulate carbon (C) emissions in forests, which support the largest soil carbon stocks globally. Using metagenomic sequencing and 13C‐glucose, we provide unprecedented evidence that microbial traits explain a unique portion of the variation in soil priming across forest biomes from tropical to cold temperature regions. We show that microbial functional profiles associated with the degradation of labile C, especially rapid simple sugar metabolism, drive soil priming in different forests. Genes involved in the degradation of lignin and aromatic compounds were negatively associated with priming effects in temperate forests, whereas the highest level of soil priming was associated with β‐glucosidase genes in tropical/subtropical forests. Moreover, we reconstructed, for the first time, 42 whole bacterial genomes associated with the soil priming effect and found that these organisms support important gene machinery involved in priming effect. Collectively, our work demonstrates the importance of microbial traits to explain soil priming across forest biomes and suggests that rapid carbon metabolism is responsible for priming effects in forests. This knowledge is important because it advances our understanding on the microbial mechanisms mediating soil–climate feedbacks at a continental scale. [ABSTRACT FROM AUTHOR]

Abstract: As a renewable energy source, biogas not only alleviates energy shortage in rural areas but also effectively reduces the environmental risk associated with agricultural waste management. This study presents a comprehensive overview of development of household bio-digesters and medium and large-scale biogas plants (MLBPs) in China, and discusses the advantages and disadvantages of both biogas systems in terms of environmental performance, role in agriculture, economic benefit, government support, energy efficiency, societal influence, and resident living mode. Both systems have their relative strengths and weaknesses. The operation and maintenance of household bio-digesters are easier, and their environmental and economic performances are superior compared to those of MLBPs. However, MLBPs have higher energy efficiency and better social effect. Thus, the choice of a biogas generation system depends on the local circumstances. Household bio-digesters are suitable for undeveloped regions where the rural residents live far apart from each other, whereas MLBPs are suitable for developed regions where people live close together. The government can play a positive role in preventing the negative impacts of rural social structural change, such as those of urban migration of adults, on household biogas development. Additionally, establishment of scientific and technological support and service systems is recommended for further development of biogas in rural China. [Copyright &y& Elsevier]

• The priming effect initially increased and decreased thereafter with stand age. • Nitrogen addition induced attenuation in priming effect. • Phosphorus addition induced enhancements in priming effect. • Mineral protection and nutrient limitation co-explained the effect of nutrient addition. Changes in plant carbon (C) inputs to soil due to afforestation can affect the decomposition rate of the old soil C, with this so-called priming effect being dependent on the soil nitrogen (N) and phosphorus (P) availability following the establishment of the new forest. However, the patterns and drivers of the priming effect in afforested soils as well as its responses to nutrient (i.e., N and P) addition remain unclear. In this study, soil samples were collected from various sites along a 45-year Robinia pseudoacacia afforestation chronosequence on the Loess Plateau in China, and incubation experiment with the addition of 13C-labeled glucose and nutrients (N or P) was conducted. The results showed that, regardless of N or P addition, the pattern of temporal changes in the soil priming effect was the same along the chronosequence: initially increasing and then decreasing, with a peak at the 20-year site. The lower C accessibility (indicated by a high mineral associated organic C (MOC) content determined the priming effect patterns after afforestation. Moreover, the soil priming effect after afforestation differed depending on the type of nutrient added; that is, it decreased with N addition but increased with P supplied. This suggests that the decomposition of old soil C at the late stage was inhibited by N addition but stimulated after P addition. Aside from soil and microbial properties, aggravated microbial nutrient limitation was a primary reason for the decreased priming effect response induced by N addition, whereas the increased response caused by P addition was due to the alleviation of microbial P limitation. Collectively, our findings shed light on the contrasting impacts of nutrient addition on the priming effect in afforested ecosystems and highlight the importance of mineral protection and microbial nutrient limitation in regulating this phenomenon under changing nutrient availability conditions. [ABSTRACT FROM AUTHOR]

• Vegetation restoration has significantly promoted soil and water conservation; • Afforestation leads to strong evapotranspiration than abandoned farmland; • Afforestation may lead to water depletion in the late restoration stage; • Abandoned farmland is more conducive to sustainability of vegetation restoration; Vegetation restoration has been widely implemented to restore degraded land. However, vegetation expansion may result in the overconsumption of soil moisture and soil desiccation, which in turn exacerbates land degradation. To ensure the sustainability of ecological restoration, it is necessary to optimise restoration patterns. Two restoration patterns (afforestation with Robinia pseudoacacia L. (RP) and abandoned farmland (AL)) along a revegetation chronosequence (0, 9, 17, 27, and 42 years) were selected to analyse variations in soil and hydrological characteristics on the Loess Plateau, China. The results showed that for the two revegetation types, the soil quality index (SQI) increased markedly (p < 0.05) and the soil loss (SL) and surface runoff (R) decreased significantly (p < 0.05) over time, indicating that vegetation restoration improves soil quality and prevents soil and water erosion. The annual increments of soil moisture storage (Ws) within a 200 cm depth notably decreased during the late restoration stage (>27 years) for the artificial forest. Moreover, forest also showed increasing actual evapotranspiration (ET) trends and decreasing Ws trends. These results suggest that afforestation might lead to overconsumption of water and soil water depletion during the late restoration stage. Although RP sites had higher SQI (22.2–36.7 %) values and lower SL (47.0–81.4 %) and R (86.5–196.8 %) values when compared with AL sites, the change rates of the SQI, R, and SL at RP sites were stable or decreased over a period of restoration, while these rates showed increasing tendencies under AL sites. These suggests that natural grasslands may be more beneficial than artificial forests during the late restoration stage. Therefore, naturally restored grasslands are highly recommended for sustainable ecological restoration in the semiarid and arid areas of the Loess Plateau or in similar areas elsewhere. [ABSTRACT FROM AUTHOR]

• The soil aggregate multifunctionality (SM) is influnced by aggregate size (AS). • The relation between bacterial diversity and SM is affected by AS and afforestation. • Afforestation enhances the complexity and stability of aggregate bacterial community. • The complexity of bacterial community is the key factor mediating aggregate SM. The multifunctionality of soil ecosystems depends on the soil structure and microenvironment because soil is a multi-structured, interconnected system. However, how the microenvironments of different aggregate affect the soil microbial community and soil multifunctionality remains unknown, which hinders our ability to understand the sustainability of afforestation ecosystems. To address this, we investigated three paired afforestation sequences accosted 629.3 km on the Loess Plateau, China. Our results showed that afforestation significantly increased the stability of soil aggregates and the macroaggregates increased soil multifunctionality, including carbon, nitrogen, and phosphorus cycle functions. In addition, soil enzyme (BG, PO, LAP, and NAG) activities were enhanced by the soil aggregate size, which played a major role in supporting soil multifunctionality. This change was directly affected by soil aggregate size or indirectly affected by the complexity of bacterial co-network and was regulated by carbon restriction and the abundance of core species. In addition, macroaggregate increased the complexity of soil bacterial communities and afforestation enhanced the complexity crossed aggregates with different sizes and consequently affected soil multifunctionality during afforestation. Therefore, the responses of soil microbes in different soil aggregates to afforestation should be considered when assessing the sustainability of afforestation, as different soil structures have varied response to forest ecosystems in semiarid and arid climates. [ABSTRACT FROM AUTHOR]

• Altered precipitation significantly affected soil C fractions and CPMI. • Microbial C limitation was alleviated with increasing precipitation. • The proportion of Poly-alcoholic C and aliphatic C increased with precipitation. • Labile C functional groups and C limitation play opposite roles in mediating CPMI. Ongoing, multifaceted climate change impacts soil carbon (C) dynamics, with serious possible consequences on terrestrial C cycling. Using a three-year manipulative experiment in abandoned land on the Loess Plateau of China, we examined the effects of in situ warming and altered precipitation (ranging from 50% reduction to 50% increases in precipitation) on different fractions of the soil organic C (SOC), the C pool management index (CPMI), ecoenzymatic stoichiometry, and SOC functional groups. Our results showed that SOC, readily oxidizable organic C, dissolved organic C, particulate organic C, and microbial biomass C exhibited an increasing trend with increasing precipitation, whereas warming had no significant effect. This response pattern also led to an increase in the CPMI with increasing precipitation. The ecoenzymatic vector model indicated that microbial C limitation decreased with increasing precipitation. In addition, the proportion of labile poly-alcoholic C and aliphatic C increased with precipitation gradient, while recalcitrant aromatic C and carboxylic C decreased. The CPMI correlated negatively with microbial C limitation and positively with labile SOC functional groups. Structural equation modeling and relative importance analyses further indicated that microbial C-limitation and labile SOC functional groups are important factors mediating the CPMI but have opposite effects. Overall, these findings considerably advance our understanding of the links between the soil CPMI and both microbial elemental limitations and SOC chemical composition, providing new insight for the accurate prediction of soil C dynamics under changing environments. [ABSTRACT FROM AUTHOR]

Abstract: As a fuel, rural biogas is a promising renewable energy source. Policy support is a key initial impetus for industry development. This study explores household biogas development in rural China based on policy support found in literature. Relevant policies, which mainly include directive and guiding policies, economic inspiring policies, research policies, market policies, and other constructive policies, are gradually issued. Moreover, the National People''s Congress has enacted five relevant laws, including the Agricultural Law, Renewable Energy Law, Animal Husbandry Law, Energy Conservation Law, and the Act on the Development of Circular Economy. The Energy Law is currently under revision. Relational rules and regulations have also been formed in response to the national policies and laws, which have already produced significant effects. The development of rural household biogas in China is growing steadily, and the technology standard projects have been established. The number of household biogas digesters and biogas annual output in 2010 was double of that in 2005. The offered financial incentive increased from 47 million dollars in 2002 to 760 million dollars in 2011. Policy supports play an important role in rural biogas development. And thus, additional national policy supports are necessary in the fields of scientific research, technological development, and biogas use model. [Copyright &y& Elsevier]

Changes in precipitation patterns in arid and semi-arid regions can reshape plant functional traits and significantly affect ecosystem functions. However, the synchronous responses of leaf economical, anatomical, photosynthetic, and biochemical traits to precipitation changes and their driving factors have rarely been investigated, which hinders our understanding of plants' ecological adaptation strategies to drought tolerance in arid areas. Therefore, the leaf traits of two typical plantations (Robinia pseudoacacia , RP and Pinus tabulaeformis , PT) along the precipitation gradient in the Loess Plateau, including economical, anatomical, photosynthetic, and biochemical traits, were investigated in this study. The results show that the leaf photosynthetic traits of RP and PT increase along the precipitation gradient, whereas leaf biochemical traits decrease. The anatomical traits of PT decrease with increasing precipitation, whereas no significant variation was observed for RP. Random Forest analysis show that LNC, LDMC, Chl, and PRO are leaf traits that significantly vary with the precipitation gradient in both plantations. Correlation analysis reveals that the traits coordination of RP is better than that of PT. The LMG model was used to determine driving factors. The results suggest that MAP explains the variation of PT leaf traits better (30.38%–36.78%), whereas SCH and SPH contribute more to the variation of RP leaf traits (20.88%–41.76%). In addition, the piecewise Structural Equation Model shows that the climate and soil physical and chemical properties directly affect the selected leaf functional traits of RP, whereas only the soil chemical properties directly affect the selected leaf functional traits of PT. The results of this study contribute to the understanding of the ecological adaptation of plants to environmental gradients and highlight that correlations among leaf traits should be considered when predicting plant adaptation strategies under future global change scenarios. • The leaf functional traits in broadleaf and coniferous plantations had different response patterns. • LNC, LDMC, Chl, and PRO seemed to be the most sensitive leaf traits that responded to precipitation changes. • Better coordination among leaf functional traits was observed in the broadleaf plantation. • MAP contributed more to traits variations in coniferous plantation, SCH and SPH explained more in broadleaf plantation. [ABSTRACT FROM AUTHOR]

Natural restoration (NR, e.g., secondary succession) and artificial restoration (AR, e.g., afforestation) are key approaches for rehabilitating degraded land; however, a comparative assessment of microbial network between these approaches is lacking. We compared bacterial networks under NR and AR in two different watersheds on the Loess Plateau. Our findings revealed significantly heightened network complexity under NR compared to AR, including metrics such as node, edge, modularity, degree, centrality, and keystone nodes. NR's network robustness exceeded AR by 19.45–35.9% and 7.79–17.74% in the two watersheds, aligning with the ecological principle that complexity begets stability. The significantly higher negative/positive cohesion and natural connectivity under NR also support its better network stability than AR. Integrated analysis of paired sequencing data from five Loess Plateau studies conducted on the Loess Plateau further confirmed the higher complexity and stability of bacterial networks under NR. Further analysis unveiled "biological interactions" as primary drivers of bacterial co-occurrence (on average 84.21% of links), surpassing the influence of environmental filtering (5.17%) or dispersal limitation (4.2%). Importantly, networked communities under NR exhibited generally stronger linkages with various ecosystem function than AR. Overall, our study provides insights into vegetation restoration strategies from the perspective of microbial network, underscoring natural regeneration's potential as a superior remedy for degraded-land restoration. • Bacterial network features under natural and artificial restoration were studied. • Bacterial networks showed higher complexity and stability under natural restoration. • Bacteria show tighter correlation with ecosystem function under natural restoration. • Regional data analysis supports higher network stability under natural restoration. [ABSTRACT FROM AUTHOR]

Fungi play critical roles in the regulation of terrestrial ecosystem processes and functions. However, the biogeographic patterns, assembly mechanism and phylogenetic information of fungi across complex environmental gradients remains unexplored, especially the differences between abundant and rare fungi. Here, based on an extensive soil sampling (117 samples) covering almost all vegetation types in the Loess Plateau, we explored biogeography, community assembly, and phylogenetic niche conservatism of abundant and rare fungi. The results showed that the abundant fungal taxa exhibited less phylogenetic clustering than the rare fungi, but their environmental associations and phylogenetic signals were stronger. Stochastic processes dominated the assembly of abundant fungi. In contrast, the homogeneous selection of deterministic processes was the major assembly process of rare taxa. Soil organic carbon and nitrate nitrogen were the key factors driving the community assembly of abundant and rare fungi, respectively. Microbial network and niche analyses further indicated abundant fungi were more advantageous for maintaining microbial co-occurrence patterns and metabolic flexibility. We concluded that abundant fungi have broader environmental adaptation potential at spatially complex environmental scales and are less dispersed by environmental changes. These results provide insights for understanding the phylogenetic and community assembly mechanisms by which fungi adapt to large-scale environmental changes. • This is a regional-scale survey of soil abundant and rare fungal taxa. • Abundant fungi showed stronger environmental associations and phylogenetic conservation. • Rare fungi have higher phylogenetic diversity. • The assembly of abundant and rare fungi is dominated by randomness and determinism, respectively. • Soil organic carbon and nitrate nitrogen are key factors mediating abundant and rare fungal assembly, respectively. [ABSTRACT FROM AUTHOR]

The spatial pattern of herbaceous plants is closely associated with the reestablishment of species diversity as well as other ecological benefits in restored vegetation communities. However, it is still not clear how the distribution of herbaceous understory plants occur after the vegetation restoration. Additionally, the relationship between spatial heterogeneity index and number of herbaceous plants in semi-arid areas are still not well-understood. We selected two types of 35-year-old afforested lands and one type of grassland with areas of 50 × 50 m in Ansai County, Northern Shaanxi, Loess Plateau of China (36°46′42″–36°46′28″ N, 109°13′46″–109°16′03″ E). Each plot was evenly divided into a total of 100 (5 × 5 m in size) cells. The herbaceous plants in each cell were surveyed in three randomly selected 1 m×1 m S-quadrats. The power law model was used to define the relationship among the variance in the number of plants for species i (vi) and the mean total number of plants (mi) to reflect the spatial heterogeneity index. Results indicated that the relationship between vi and mi in afforested land and grassland demonstrated good fit with the power law model (R2 > 0.85). The spatial heterogeneity indexes of all herbaceous species in the three plots were >0, and the regression lines of the power law model were significantly above the y = x. The species number, Shannon index, and overall spatial heterogeneity indexes of the afforested land were greater than those of the restored grassland. There was a positive correlation between spatial heterogeneity index and mean number of plant individuals. Additionally, there was a negative correlation between overall spatial heterogeneity index and total number of herbaceous plant individuals. These results indicated that afforestation has positive effects on the reestablishment of diversity for herbaceous species. The herbaceous species in afforested land and restored grassland communities exhibited an aggregated distribution in the Loess Plateau. [ABSTRACT FROM AUTHOR]

Aims: This study aimed to determine the responses of soil bacteria and fungi to plant species diversity and plant family composition (PFC) following secondary succession on former farmland (FL). Methods: Illumina sequencing of 16S rRNA and ITS genes was used to determine soil microbial communities along a chronosequence of FL left abandoned for 0, 10, 20, 30, 40, and 50 years on the Loess Plateau. Soil properties, plant diversity, and PFC were also investigated. Results: Fungal communities were dominated by Ascomycota and Basidiomycota. Fungal diversity and Ascomycota abundance increased with time, while Basidiomycota abundance decreased. The fungal diversity and dominant phyla were related to the increasing levels of plant species diversity and evenness with succession. Bacterial diversity first increased and then decreased as succession proceeded, peaking at 30 years. Bacterial communities transitioned from Actinobacteria to Proteobacteria dominance during the first 30 years, after which Actinobacteria was dominant. Plant family composition exerted indirect effects on the diversity and dominant phyla of bacterial communities, mainly through direct effects on soil organic carbon and total nitrogen content. Bacterial diversity and Proteobacteria abundance were higher at Leguminosae- and Gramineae-dominant succession stages, but lower in Compositae-dominant plots; Actinobacteria showed the opposite result. Conclusions: Plant species diversity and evenness might be the key drivers for shaping fungal communities, but bacteria are influenced more by changes in PFC and abiotic soil nutrient levels during succession. [ABSTRACT FROM AUTHOR]

Straw retention is an effective method to conserve soil water content and improve soil carbon stocks. However, how soil carbon dynamics respond to different straw retention practices remains unclear. In this study, we investigated soil respiration and soil carbon sequestration at depths of 0–100 cm. We conducted a two-year field experiment with three crop rotation treatments and three straw retention treatments in northwest China. The straw retention treatments included no straw retention (NS), retention of half the straw (HS), and retention of the total amount of straw (TS). The crop rotations treatments included winter wheat plus summer soybean (WS), winter wheat plus summer maize (WM), and winter wheat plus summer fallow (WF). Mean soil respiration rates under WS, WM, and WF treatments were 5.14, 6.53, and 5.49 μmol·m-2·s-1; and 5.67, 5.47, and 6.03 μmol·m-2·s-1 under TS, HS, and NS treatments. The mean soil water content were 15.50%, 15.57%, and 15.74% under WS, WM, and WF rotations, and 15.81%, 15.41%, and 15.50% under TS, HS, and NS treatments. The soil organic carbon (SOC) concentration was higher with increased straw retention, and lower at deeper soil depths. Mean SOC concentrations under different rotations and straw treatments of TS, HS, and NS, respectively were as follows: WS: 6.91, 6.63, 6.39 g/kg; WM: 6.90, 6.72, 6.57 g/kg; and WF: 6.49, 6.52, 6.37 g/kg. Soil temperature was the main determinant of soil respiration rates. We conclude that WS rotation resulted in lower soil respiration, WM rotation resulted in a higher soil carbon sequestration potential, and WF rotation resulted in higher soil water content. However, continued, long-term monitoring is needed to confirm the effect of rotations and straw retention on soil respiration and carbon sequestration in dryland cropping systems in northern China. [ABSTRACT FROM AUTHOR]

Core IdeasVegetation restoration altered the diversity and structure of the N‐fixing microbial community.Dominant phyla changed from Actinobacteria in farmland to Proteobacteria in revegetation types.The N to P ratio was the key environmental factor regarding the composition of N‐fixing microorganisms.Study data can be a reference for developing N‐fixing microbial fertilizers suitable for this region. In this study, we determined the variations in the diversity and structure of nitrogen‐fixing microorganisms during afforestation and how this variability correlates with the soil physicochemical factors. Soils were sampled from replicated plots representing three revegetation types (Robinia pseudoacacia L. [Rp], Caragana korshinskii Kom [Ck], and abandoned land) with adjacent farmland as the control at a research site in Ansai District, Yan'an City, Shaanxi Province, China. Using high‐throughput sequencing of the nifH rRNA gene, we found that revegetation significantly increased the Shannon diversity index, and for the richness index Chao1 was highest in Ck and have no significant difference in other three lands. From farmland to vegetation types abandoned land, Ck, and Rp, the dominant phylum of nifH microorganisms changed from Actinobacteria to Proteobacteria. Furthormore, variation in the Chao1 richness index was significantly influenced by pH (p = 0.002), soil organic carbon (SOC; p = 0.025) and total nitrogen (TN; p = 0.015). The Shannon diversity index was significantly influenced by SOC, nitrate nitrogen (NN), C to P ratio, TN, AN, N to P ratio, TP, and sand. The changes of nifH microorganism composition at the phylum level were significantly correlated with the soil N to P ratio, which explained 53.1% of the variation among environmental factors (F = 11.8, p = 0.002). The ratio of N to P (interpretation rate 65.2%, F = 18.8, p = 0.002) was also a key factor that influenced the composition at the genus level. Based on the diversity and composition, Ck was a more advantageous recovery method to increase the capacity for N fixation. This study provides a basis for the study of N‐fixation characteristics in the Loess Hilly Region. [ABSTRACT FROM AUTHOR]

Microbial necromass is known to be the main component of soil organic carbon (C) sequestration. However, the contribution of microbial necromass to soil aggregates has not been comprehensively studied because of the heterogeneity of microhabitats in different soil aggregates, especially in different ecosystems on a global scale. To address this gap, we conducted a global-scale meta-analysis to investigate the contribution of microbial necromass to carbon sequestration in aggregates and identify the climatic and soil factors that influence necromass carbon in aggregates. The database of fungal and bacterial necromass carbon was based on the glucosamine and muramic acid contents in microaggregates (< 250 μm, 226 samples), medium macroaggregates (250–2000 μm,132 samples), and macroaggregates (> 2000 μm, 66 samples). On average, microbial necromass carbon in microaggregates, medium macroaggregates, and macroaggregates contributed 48.5 %, 40.9 %, and 42.5 % of aggregate carbon sequestration, respectively. The contribution of fungal necromass carbon was significantly higher than that of bacteria (average 30.9 % vs. 13.1 %, respectively). Meanwhile, the ratio of fungal to bacterial necromass carbon increased with the increasing aggregate size, from 2.68 (< 250 μm) to 3.11 (250–2000 μm) to 3.14 (> 2000 μm) for micro, medium size, and macroaggregates, respectively. In addition, the screening method for aggregates and the type of land use significantly affected the contribution of microbial necromass to aggregate carbon sequestration. Specifically, grassland and dry sieving significantly increased the contribution of microbial necromass carbon to aggregate carbon. Finally, the results from PLS-PM showed that climatic factors regulated fungal and bacterial necromass carbon through soil pH, sand, and nutrients in aggregates, thereby enhancing the contribution of microbial necromass to aggregate carbon sequestration. In addition, fungal and bacterial necromass carbon improved with increasing carbon and nitrogen content of the aggregates. Furthermore, a lower soil pH seemingly stimulates the accumulation of fungal and bacterial necromass in soil aggregates. These findings emphasize that the contribution of microbial necromass carbon to aggregate carbon sequestration, especially fungal necromass carbon, is an important method for improving carbon sequestration in soil aggregates. [Display omitted] • The contribution of microbial necromass-C to aggregate-C sequestration is 43.96 %. • The contribution of fungal necromass-C is higher than that of bacterial. • Wet-sieving decrease the value of microbial necromass-C than Dry-sieving. • Grassland enhances the accumulation of necromass-C than other ecosystems. [ABSTRACT FROM AUTHOR]

Abstract Soil microbial communities are closely associated with aboveground plant communities and soil properties. This study explored the dynamics of soil bacterial communities during the plant growing season and their interaction with soil carbon and nitrogen, physicochemical properties, plant biomass and diversity following afforestation. The study investigated afforested lands containing Robinia pseudoacacia L (RP) and Caragana korshinskii Kom (CK), as well as abandoned land (AL) and farmland (FL) in the Loess Hilly Region of northern China. After establishment on former FL for 40 years, the Richness and Shannon's index, above-ground herbaceous biomass (AGB) and below-ground biomass (BGB) in RP and CK increased by 0.5, 0.1, 1.2 and 1.7 times, respectively, compared with AL. Additionally, the soil organic carbon (SOC), total nitrogen (TN), dissolved organic carbon/nitrogen (DOC/N) and microbial biomass carbon/nitrogen (MBC/N) increased by 1.7, 1.9, 0.8 and 2.5 times, respectively, while the soil bacterial abundance and alpha diversity (Shannon index) increased by 4.7% and 2.0% compared with FL. During the growing season, the soil carbon and nitrogen content was higher in August or October than in April or June. Particularly, the AGB, DOC and MBC showed a temporal pattern of normal distribution that was 36.7%, 48.2% and 74.9% higher in August than the rest of the study period. The BGB also increased by 123.5% in October compared with June in all study areas. The soil bacterial abundance in afforested lands was also higher in October, and beta bacterial diversity (Principal coordinates analysis plots: PCoA) was greater in June and August than in April and October. The dominant bacterial taxa, Proteobacteria and Bacteroidetes , were significantly higher in afforested lands than in FL, and Proteobacteria increased from April to October, while Actinobacteria and Acidobacteria peaked in June or August. These seasonal changes in the soil bacterial community were significantly correlated with carbon and nitrogen levels of soil and plant biomass, especially with DOC and BGB. Additionally, soil variables explained 41.2% of the total variation in bacterial-dominant phyla, while plant biomass only explained 20.2% of it, which indicates that soil properties are more important controlling factors of the bacterial community than plant biomass. In conclusion, soil variables change seasonally, which drives the composition and diversity of the soil bacterial community to exhibit a temporal pattern over the growing season after return of AL to forest. Highlights • Afforestation improving soil, vegetation and bacterial community simultaneously. • Variation of soil and plants control seasonal dynamics of bacterial communities. • Soil properties were stronger effected bacterial composition than plant biomass. • Soil bacterial compositions were the most sensitive to DOC and root biomass. [ABSTRACT FROM AUTHOR]

Abstract The effects of vegetation restoration on plant characteristics and soil physicochemical properties have been widely documented; however, knowledge of the variation in soil ecoenzymatic activity and stoichiometry remains limited, particularly with respect to their relationship with plant and soil variables in restored ecosystems. Here, the vegetation and soil from one farmland and two restored land-use types (Robinia pseudoacacia plantations: RP and abandoned lands: AL) of four age classes (10, 18, 28, and 43-years) were investigated and sampled on the Loess Plateau, China. The activity of C, N, and P-acquiring enzymes (β-1,4-glucosidase, BG; β-1,4-N-acetylglucosaminidase, NAG; leucine aminopeptidase, LAP; and alkaline phosphatase, AP) and other major influencing factors (soil physical properties, soil nutrient contents, and microbial biomass) were determined. It was found that both restoration time and vegetation types significantly affect plant characteristics, soil physical properties, soil nutrient content, and microbial biomass. Soil BG, NAG + LAP, and AP enzyme activities were higher in RP and AL than in farmland, and increased with restoration time in AL. For RP, the activity of these enzymes increased from year 10 to year 28, then decreased from year 28 to year 43. Soil ecoenzymatic C:P and N:P activity ratios were ordered: farmland > AL > RP, and decreased with restoration time in AL and RP; thus, P limitation was stronger in RP than in AL and increased with restoration time in both AL and RP. Soil ecoenzymatic C:N:P acquisition ratios of farmland, AL, and RP deviated from the 1:1:1 ratio and depended on the availability of environmental nutrients and demand for microbial nutrients. The vegetation characteristics and soil physical properties were closely related to the nutrient acquisitions of microbes and, ultimately, contributed towards shaping soil ecoenzymatic activity and stoichiometry (particularly vegetation coverage, belowground biomass, soil water content, soil bulk density, and pH). Furthermore, variation in soil ecoenzymatic activity and stoichiometry was better accounted by dissolved nutrients in the soil (particularly C and N) and microbial biomass (particularly N and P) than by plant characteristics and soil properties. Overall, this study demonstrates that the C:N:P stoichiometry of soil microbes and ecoenzymatic activity is nutrient dependent, rather homeostatic, with the potential to influence nutrient cycling on the Loess Plateau. Graphical abstract Image 1 Highlights • Soil ecoenzymatic C:N:P acquisition ratios deviated from the 1:1:1. • Soil ecoenzymatic activity ratio was not in homeostasis but resource dependent. • P limitation of microbial metabolisms increased with restoration time. • Soil ecoenzymatic stoichiometry were influenced by both plant and soil properties. • Soil dissolved nutrients and microbial biomass have stronger effect on soil ecoenzymatic stoichiometry than plant and soil properties. [ABSTRACT FROM AUTHOR]

Abstract Agricultural non-point source (NPS) pollution in water source protection areas poses serious challenges for governments in developing countries. It is important to consider the environmental behavior of farmers when exploring the causes of NPS pollution as well as when establishing scientific controls and management measures. However, the poor understanding of factors influencing the environmental behavior of farmers and the lack of a suitable environmental socio-psychological model limit the application of the environmental behavior of farmers in NPS pollution management. In this study, we therefore integrated the theory of planned behavior (TPB) and the protection motivation theory (PMT) to identify the main determinants of the NPS pollution-related environmental behavior and intention of farmers in the Water Source Area of the Middle Route of the South-to-North Water Diversion Project in China. Results indicated that the integrated model provided a better understanding of the environmental behavior and intention of farmers than that provided by each component when used individually, and revealed that farmers perceived that the susceptibility and severity of threats caused by water deterioration influenced environmental intention through the mediating effects of subjective norm and attitude toward adopting pro-environmental behavior. At the same time, the perceived vulnerability of farmers was relatively high and their perceived severity was relatively low. Furthermore, the subjective norm, attitude, self-efficacy (i.e., the perceived behavioral control), and response efficacy positively and significantly influenced intention. However, response cost had a significantly negative effect on intention. Among them, subjective norm had the largest effect on intention. Intention was the key determinant for the actual environmental behavior of farmers, while self-efficacy also had a significantly positive effect on behavior. Managing and controlling agricultural NPS pollution requires a multi-disciplinary and comprehensive approach. Therefore, an integrated theoretical framework was developed in this study by integrating TPB and PMT to gain insight into the environmental behaviors and intention of farmers. The results provided a theoretical basis for NPS pollution control. Highlights • Integrated TPB and PMT to study farmers' environmental behavior. • Subjective norm had the greatest effect on farmers' environmental intention. • Attitude and subjective norm mediate the effects of threat appraisal on intention. • Pro-environmental behavior should be facilitated through comprehensive measures. [ABSTRACT FROM AUTHOR]

Highlights • Afforestation improved soil IN concentration and stock until forest reached maturity. • Forestland had higher NH 4 –N, NO 3 –N and TIN than grassland. • The soil (40–200 cm) accounted for 60–90% of the NH 4 –N, NO 3 –N and TIN stocks. • ANR was more sensitive than other IN variables to soil physicochemical properties. Abstract In the Loess Hilly Region of China, the widespread conversion of farmland to forestland and grassland has resulted in great changes in soil carbon (C) and nitrogen (N) storage in the shallow soil layers. However, knowledge regarding changes in the status and relative availability of inorganic nitrogen (IN) is still limited. To determine the responses of soil IN storage and its relative availability to revegetation patterns and chronosequence, a 0–200 cm soil profile was collected from two typical vegetation restoration patterns in the heartland of the region, artificial forestland (Robinia pseudoacacia) and natural grassland, with a stand age sequences of 15, 20, 25, 30 and 40 years. The farmland near the sites was selected as a control. As a whole, the NH 4 -N, NO 3 -N and total inorganic nitrogen (TIN) concentrations and stocks in the forestlands were significantly higher than those in the grasslands, especially in the topsoil (0–10 cm). With increasing revegetation chronosequence, afforestation improved soil NH 4 –N, NO 3 –N and TIN concentrations and stocks until Robinia pseudoacacia reached maturity at an age of 25–30, but abandoned on former farmland had minor effects on soil IN. After revegetation, soil NH 4 –N was higher than NO 3 –N, and the NH 4 –N/NO 3 –N ratio (ANR) was greater than 1 and increased with soil depth. The soil at 40–200 cm accounted for 60–90% of the total IN stock of the 0–200 cm soil profile, and the soil at 100–200 cm accounted for more than 35% of the total levels. Moreover, soil physicochemical properties were significantly correlated with soil IN variables, and ANR had a greater correlation coefficient with soil physicochemical properties than the other IN variables. It was concluded that afforestation was a better choice for soil IN restoration of degraded land, and subdeep and deep soil provided an extremely important resource for evaluating soil IN pools and their relative availability. Furthermore, soil IN dynamics, particularly ANR, could be regarded as indicators for assessing the dynamics of soil fertility. [ABSTRACT FROM AUTHOR]

Abstract C:N:P stoichiometry in the plants and soils is an important indicator of biogeochemical cycles and functioning in ecosystems; however, the response of plant growth to ecological stoichiometry following afforestation remains unclear. To illustrate the C:N:P stoichiometry connections between the plants and soils and their effects on the growth of plants, soil and plant samples were collected from one farmland site and four Robinia pseudoacacia (RP) forests that were planted for 10, 15, 25, and 35 years. Plant community characteristics, growth of overstory trees and understory plants, physical and chemical properties of the soil, and C:N:P stoichiometry in plants and soil were measured. The results revealed that soil organic C, total N, total P, dissolved organic N, C:P and N:P ratios, and water content significantly increased, whereas soil bulk density, available P, and pH decreased with afforestation age. Leaf C:P and N:P ratios in RP were significantly higher than that in understory biomass because P concentrations gradually decreased in RP leaves and increased in understory biomass. The C, N, and P contents and stoichiometry in the soils and plants were significantly correlated, particularly for N:P ratio that can be used to reveal close coupling between plant and soil nutrients. The N:P ratio in RP leaf and understory biomass increased with afforestation age and varied from 14.44 to 20.81 and 7.59 to 10.96, respectively, suggesting that P limitation gradually increased in RP, and N limitation gradually declined in understory biomass. Furthermore, the responses of overstory trees and understory plant growth to N:P ratios were contradictory, because of their different nutrient acquisition patterns and nutrient-use efficiencies. Therefore, this finding provides evidence that the strong correlation between the plants and soils were tightly coupled to N and P concentrations and N:P ratios, and therefore, have the potential to influence the growth of forests on the Loess Plateau. Graphical abstract Unlabelled Image Highlights • Robinia pseudoacacia afforestation improved soil and plant community characteristics. • Leaf C:P and N:P ratios were higher for Robinia pseudoacacia than for understory plants. • N:P ratios indicate a tight coupling between soil and plant. • P limitation increased in Robinia pseudoacacia and N limitation declined in understory biomass. • N:P ratios negatively correlated with Robinia pseudoacacia growth, but positively correlated with understory biomass. [ABSTRACT FROM AUTHOR]

Abstract Afforestation greatly alters soil nitrogen (N) dynamics and soil microbial community, but the response of soil N dynamics to microbial activity, particularly to that of N-fixing microbes, remains unclear. In the present study, soil samples were collected from areas with a chronosequence of 17, 27 and 42 years of Robinia pseudoacacia L (RP17a, RP27a, and RP42a) and a sloped farmland (FL) as a control. The nifH gene was sequenced with the Illumina MiSeq platform to analyze soil microbial diversity and composition, and soil N fractions (TN, AN, NN, MBN, DON) were estimated. The soil N stocks, N fractions, and diversity of N-fixing microorganisms increased with the chronosequence of R. pseudoacacia. Beta diversity, analyzed using nonmetric multidimensional scaling, revealed that afforestation effectively improved soil microbial communities. The profiles of the N-fixing microorganism communities at sites 17a, 27a and 42a were clearly separated from the farmland, and soil N-fixing microbial community compositions generally changed in the farmland from Actinobacteria-dominated to Proteobacteria- dominated with stand ages. Redundancy analysis revealed that soil N fractions were positively correlated with the main species, particularly for AN, which had a 34.7% explanatory space in axis one and was significantly correlated with the Proteobacteria at the phylum level. Results implied the evolutionary tendency of the dominant microbial groups, and demonstrated the variation of the N fractions and some other physical-chemistry properties along the chronosequence of R. pseudoacacia, and that AN was the most sensitive N fraction to the N-fixing microorganism composition. Thus, our results provide evidence that the variation of soil compositions of N-fixing microbial communities is linked to the level of N fractions, especially the content of AN. Highlights • Soil diazotrophs abundance, diversity, and compositions changed along with the chronosequence. • With the increase in ages, the difference in species composition decreased. • Soil N fractions were significantly correlated with the major microbial species. • AN was the most sensitive N fraction to N-fixing microorganisms. [ABSTRACT FROM AUTHOR]

Abstract The use of crop residues as mulching materials or organic fertilizer, instead of burning, can help improve the soil organic carbon (SOC) and crop grain yield. An experiment was conducted for three consecutive seasons from 2013 to 2016, to study the effect of no straw (S0), S1/2 (700 kg/ha soybean straw, and 3000 kg/ha wheat straw), and S1 (1400 kg ha−1 soybean straw, and 6000 kg/ha wheat straw) treatments in wheat-soybean multi-crop system. The randomized complete block design was used with three repeats. Compared with the S0 regime, a significant increase of 0.5%–8.7% and 1.4%–27.7% in soil CO 2 emission was observed in the S1 regime during all growth stages of summer soybean and winter wheat, respectively. Soil temperature of S1/2 and S1 was 0.1–1.1 °C and 0.3–1.4 °C higher than that of S0 during the seeding stage and greening stage for wheat, during 2013 to 2016. During wheat season, soil moisture was higher in the S1 than in the S0 treatment. Likewise, wheat, soybean crop resulted the same results. Soil CO 2 emissions increase with the increasing in soil temperature, and 73.4–73.9% of the variation could be explained by seasonal variation in soil temperature in wheat season. Similarly, 69.5–74.7% of the variation in soil CO 2 emissions is recorded by seasonal variation in soil temperature in summer soybean season. Meanwhile (S1) increased the SOC and grain yield of wheat and soybean when compared to S0. Straw input increasing soil CO 2 , grain yield and SOC content, considering the benefits of straw inputs to crops yield and SOC content, It is concluded that the addition of straw improve agriculture production. However, the types of straw inputs in order to promote the sequestration of soil organic carbon with the decrease in greenhouse gas emission is the future research direction for agriculture development in Guanzhong region of China. Graphical abstract Unlabelled Image Highlights • Soil temperature was the main driven for soil CO 2 emission • Cumulative soil CO 2 emission increased by straw input • Straw input increased soil organic carbon • Straw returning and mulching increased soil CO 2 emission and crop yield [ABSTRACT FROM AUTHOR]

Highlights • Potato is sensitive to drought over the north single cropping zone in China. • The north single cropping zone of potato tended to become drier since the 1970s. • The study area as a whole will become drier in the potato mature stage. • The future drought trend is generally consistent with the current state. • Crop management strategies must be adapted for increased drought conditions. Abstract Knowledge about drought variability in the main potato producing areas can provide a scientific basis for management of potato crops. In this study, the variations and patterns of drought in the potato growing period (GP), seedling stage (SS), tuber-growth stage (TS), and mature stage (MS) identified by the Standardized Precipitation Evapotranspiration Index (SPEI) were investigated in the north single cropping zone (NSCZ) in China for the period of 1960–2016 based on the empirical orthogonal function analysis, Mann–Kendall statistical test, Mann–Kendall test, Sen's slope, Hurst exponent, and continuous wavelet transform. Additionally, grey theory was used to study the relationship between drought and potato production. The results of the study follow: 1) The spatiotemporal patterns of drought of the two leading patterns were identified. 2) Since the 1970s, the NSCZ has become drier in the GP and MS, has become wetter in the TS, but has always remained in an unstable state of alternating wet and dry conditions in the SS. 3) The changes in dryness/wetness conditions include significant periodic oscillation features. 4) The future drought trend is generally consistent with the current state. In addition, it is worth noting that the NSCZ as a whole will become drier in the MS. 5) The drought of SS and TS had a relatively large negative effect on potato production, whereas that of MS had a relatively small positive effect. Because the NSCZ is within the marginal region of the Asian monsoon and the agro-pastoral ecotone, it is an ecologically fragile region. Therefore, under the background of global climate change, studying changes in dryness/wetness conditions has important implications for the ecological security and potato production of the region. [ABSTRACT FROM AUTHOR]

Highlights • Wheat straw mulch increases (7.4%) soil moisture and decreases (3%) soil temperature. • Increases in straw mulch and nitrogen significantly improved growth of soybean. • Straw mulch (6 tons ha−1) with 27 kg N ha−1 significantly increased yield of soybean. Abstract In North-west china, the soybean (Glycine max L. Merr.) is grown in June, when the climate is dry, and soil has limited moisture contents. Moisture deficiency limits the soybean biomass. We studied the effects of wheat straw mulching and nitrogen on soybean growth, physiology and soil properties in three-year field experiments. The treatments included three straw mulching i.e. S1 (0 kg ha−1), S2 (3000 kg ha−1) and S3 (6000 kg ha−1), and three nitrogen rates i.e. N1 (0 kg N ha−1), N2 (21.6 kg N ha−1), and N3 (27 kg N ha−1). Full mulching (S3) significantly increased moisture retention (7.4%) and decrease soil temperature (3.0%) in 0–20 cm soil depth, increased photosynthesis, SPAD-value, leaf area, leaf area index, growth, and soybean grain yield (20.8%) over no-mulching (S1). The S3 improved the roots mass, nodules number and weight than S1. The application of 27 kg N ha−1 or 100% N fertilizer (N3) had significantly increased photosynthesis, SPAD-value, growth, and biomass and seed yield of soybean over no-N application (N1). It was concluded that using straw mulching (6 Mg ha−1) can change the soil hydrothermal regime for provision of favorable condition for soybean growth when 27 kg N ha−1 was used in semi-arid condition of North-west China. [ABSTRACT FROM AUTHOR]

Highlights • Natural succession increases plant species diversity and abundance. • Natural succession increases soil carbon, nitrogen, and phosphorous contents. • Functional group composition affects soil C, N, and P mainly in the 0–20 cm layer. • Plant diversity has stronger impact on soil C, N, and P at the soil depths of 20–60 cm than 0–20 cm. • The percentage of Leguminosae plants can indicate soil quality in the 0–20 cm layer. Abstract The relationships among soil C, N, and P, aboveground plants, and belowground organisms are well-known; however, the impact of the aboveground dynamics of plant communities and their ensuing effects on soil C, N, and P, particularly during secondary succession need clarification. This study explored the effects of plant functional composition and diversity on soil C, N, and P at different soil depths. Soil samples were collected at soil depths ranging from 0 to 60 cm from three grassland sites abandoned for 5, 17, and 30 years in the Yang Qing Chuan catchment. Soil properties and fine root biomass were determined for different soil depths, and the plant community characters at each site were also evaluated. The results revealed that the plant community transitioned from dominance by annual herb to dominance by perennial species during the succession, and the percentage of Leguminosae plants, plant diversity, and species richness increased with succession time. The soil water content, organic carbon, total nitrogen, total phosphorous, C:P ratio, and N:P ratio increased significantly with successional time and decreased significantly with soil depth. In contrast, the soil bulk density and pH decreased significantly with successional time and increased significantly with soil depth. Furthermore, the plant functional group composition and diversity significantly affected soil C, N, and P contents and ratios, but was sensitive to the vertical stratification of soil. Plant functional group composition had a stronger correlation to soil C, N, and P contents and ratios at soil depths of 0–20 cm than that of the 20–60 cm depth primarily due to the fact that the nutrients returned are mostly concentrated on the topsoil and seldom deposited in the deeper soils. However, plant diversity had a stronger impact on soil C, N, and P contents and ratios at soil depths of 20–60 cm than at 0–20 cm depth, because plant diversity exacerbates interspecific competition and forces the roots to grow deeper, which alters nutrients in the deep soil. In addition, the percentage of legumes can be used as a practical indicator of soil quality in the 0–20 cm layer during natural succession of abandoned farmlands. This study provides evidence that plant communities have a strong influence on soil C, N, and P, but that the pathways and degree of influence differ across vertically stratified soil. [ABSTRACT FROM AUTHOR]

Addition of organic material, such as crop straw mulch in most soils is considered a strategy for sustainable agricultural production. We conducted a two-year experiment in 2015 and 2016 to determine changes in soil biochemical properties and maize yield in response to treatment with wheat-straw mulch. The treatments consisted of the addition of different levels of wheat-straw mulch (S1: 0, S2: 2500, S3: 5000 kg ha −1 ). Soil samples from four depths (0.1, 0.2, 0.3, and 0.4 m) were collected and analyzed. Soil enzymes, such as invertase, phosphatase, urease, and catalase, were significantly higher in the S3 treatment than in the S1 treatment. Values were greater for the samples collected at 0.1 m soil depth than those collected from deeper soil layers. Regarding soil properties, soil organic carbon (SOC), available nitrogen (AN), available phosphorus (AP), total nitrogen (TN), total phosphorus (TP), and soil water content (SWC) were significantly higher in S3 at 0–0.1 m soil depth than in other treatments. Compared with the (S1), an average increase in SOC, AN, AP, TN, TP, and SWC in 0–0.4 m soil depth with full straw mulch (S3), were 32.4, 31.9, 32.0, 11.8, 16.7, and 18.5%, higher, respectively. On average, urease, phosphatase, invertase, and catalase increased by 15.1, 11.0, 88.4, and 24.0%, respectively in the S3 treatment compared with that in the S1 treatment at 0–0.1 m depth, and decreased with increasing soil depth. The S3 treatment had increased grain yield (7%), biomass yield (28%), and water use efficiency (8%), compared with the S1 treatment. Overall, our results suggested that the S3 straw mulch treatment (5000 kg ha −1 ) could be used to sustain maize productivity and promote a better relationship between soil enzymes and soil properties in the semi-arid conditions of the Guanzhong area. [ABSTRACT FROM AUTHOR]

Vegetation restoration has been widely implemented to control soil degradation, reduce soil erosion, and improve soil quality. It is vital to understand the mechanisms affecting soil quality in soil restoration processes and to determine an appropriate recover pattern for soil restoration. Thus, a soil quality index was developed using integrated approach to assess soil quality after vegetation restoration in this study. Soil samples were collected from two restoration pathways (afforestation by Robinia pseudoacacia L. and natural recovery of abandoned farmland) with ages sequence of 0, 17,27 and 42 years old at two soil depths (0–10 and 10–20 cm) to measure soil physicochemical and biological properties on the Loess Hilly Region of China, China. The results showed that soil quality index (SQI) was developed based on microbial biomass carbon (MBC), fine particles (FP), and total phosphorus (TP). The MBC, which had the fastest increase rate than TP and FP, had the highest contribution to the final SQI and these contributions increased with recovery age. The MBC values were higher in Robinia pseudoacacia L. than in abandoned land sites at all recovery ages with greater increases along with restoration age. The SQI values significantly increased with increasing restoration age up to 27 years ( P < 0.05). After 27 years, SQI values for the AL sites remained stable, while SQI values for RP sites continually improved with increasing restoration age. In addition, SQI values were higher for RP sites than for AL sites for all restoration ages. [ABSTRACT FROM AUTHOR]

The environmental behavior of farmers plays an important role in exploring the causes of non-point source pollution and taking scientific control and management measures. Based on the theory of planned behavior (TPB), the present study investigated the environmental behavior of farmers in the Water Source Area of the Middle Route of the South-to-North Water Diversion Project in China. Results showed that TPB could explain farmers' environmental behavior (SMC = 0.26) and intention (SMC = 0.36) well. Furthermore, the farmers' attitude towards behavior (AB), subjective norm (SN), and perceived behavioral control (PBC) positively and significantly influenced their environmental intention; their environmental intention further impacted their behavior. SN was proved to be the main key factor indirectly influencing the farmers' environmental behavior, while PBC had no significant and direct effect. Moreover, environmental knowledge following as a moderator, gender and age was used as control variables to conduct the environmental knowledge on TPB construct moderated mediation analysis. It demonstrated that gender had a significant controlling effect on environmental behavior; that is, males engage in more environmentally friendly behaviors. However, age showed a significant negative controlling effect on pro-environmental intention and an opposite effect on pro-environmental behavior. In addition, environmental knowledge could negatively moderate the relationship between PBC and environmental intention. PBC had a greater impact on the environmental intention of farmers with poor environmental knowledge, compared to those with plenty environmental knowledge. Altogether, the present study could provide a theoretical basis for non-point source pollution control and management. [ABSTRACT FROM AUTHOR]

Straw incorporation is widely applied to improve crop productivity, and biochar amendment may be an effective countermeasure for mitigating greenhouse gas (GHG) emissions; however, the comprehensive evaluation of straw return and biochar amendment coupled with different N application rates on soil organic carbon (SOC) sequestration rate, GHG emissions, and reactive N losses have been inadequately recorded. Consequently, the field experiment had six treatments and three replications including two mineral N fertilization rates (conventional N fertilizer application (N 1) and 30% reduced N fertilizer application (N 0.7)) and three types of straw and biochar management variations (no straw incorporation (S 0), straw incorporation (S), and straw incorporation with biochar amendment (SB)) and the results were based on three years of soil SOC and GHGs emission data in wheat-maize agroecosystem. Our finding revealed that N 0.7 reduced the GHG emissions (CO 2 : 13.9%; N 2 O: 34.2%; CH 4 : 32.5%), greenhouse gas intensity (GHGI; 32.7%), carbon footprint (CF; 35.1%) and nitrogen footprint (NF; 24.5%), but had no significantly different crop yields compared with N 1 (p > 0.05). Straw incorporation had no significant impact on CF and yield-scaled CF but increased NF (29.7%) because the stimulated GHG emissions would be offset by SOC sequestration. Under S, the wheat and maize yields increased by 9.7% and 5.4%, respectively, whereas the GHGI increased by 59.6% compared with S 0. Biochar amendment reduced GHG emissions (CO 2 : 19.9%; N 2 O: 29.9%), GHGI (32.7%), CF (26.7%) and yield-scaled CF (29.2%), while improving crop yields (wheat: 5.8% (p < 0.05); maize: 1.5% (p > 0.05)) and SOC sequestration rate (74.5%) compared with that under S. Overall, N 0.7 SB exhibited enormous potential for enhancing wheat-maize agroecosystem productivity and drastically mitigating their CF and NF in the semi-arid conditions of the Guanzhong Plain. [Display omitted] • Soil quality, crop productivity, and environmental benefits of different field managements were evaluated. • Reduce N application mitigated GHG emissions, carbon and nitrogen footprints, but had no effect on crop yields. • Biochar inhibited the stimulation of GHG emissions by straw incorporation and increased the SOC sequestration. [ABSTRACT FROM AUTHOR]

The goal of this study was to determine the dynamics of physicochemical properties and biological activities of soil, and their relationship following afforestation. Soil samples were collected at 0–10 cm from five Pinus tabulaeformis plantation forests restored for 15, 25, 30, 45, and 70 years, as well as a millet ( Setaria italica ) farmland in the Damaiji catchment area. These five afforested lands were converted from similar farmlands. The activities of catalase (CAT), saccharase (SAC), urease (URE) and alkaline phosphatase (ALP), microbial biomass, soil water content, pH, soil bulk density, soil organic carbon (SOC), total nitrogen (TN), ammonium nitrogen, nitrate nitrogen, total phosphorus (TP), and available phosphorus (AP) were measured. The results revealed that the contents of SOC, TN, AP, microbial biomass C, N, and P, CAT, SAC, URE, and ALP in the P . tabulaeformis forest soil were significantly higher than those in the farmland by 64.97%–262.02%, 75.44%–254.28%, 46.63%–114.21%, 125.95%–554.83%, 101.35%–464.21%, 15.80%–167.35%, 22.57%–49.95%, 96.78%–145.73%, 6.98%–56.08% and 89.15%–177.89%, respectively. The soil properties, microbial biomass, enzymatic activities, and C:P and N:P ratios in soil and microbial biomass improved with increasing plantation chronosequence. Variations in C:N:P stoichiometry and higher C:P and N:P ratios in the soil and microbial biomass revealed the P limitation. Simultaneously, N:P ratios included more serviceable information that reflected the relationship between soil and microbes. Soil enzymatic activities had a high correlation with soil nutrient cycling and could be indicators of soil fertility status, particularly for ALP. The significant correlation between SOC, TN, enzymatic activities, and microbial biomass revealed that the substrate availability of carbon and nitrogen could influence the activity of soil enzymes and microorganisms. This study demonstrated that soil enzymatic activities and microorganisms respond to the process of afforestation and hence have the potential to affect nutrient balance and quality of soil. [ABSTRACT FROM AUTHOR]

Alt'itudinal gradients strongly affect plant biodiversity, but the effects on microbial patterns remain unclear, especially in the large scale. We therefore designed an altitudinal gradient experiment that covered three climate zones to monitor soil microbial community dynamics and to compare those with plant and soil characteristics. Illumina sequencing of the 16S rRNA gene and ITS gene was used to analyze soil microbial (bacterial and fungal) diversity and composition, and fumigation–extraction was used to determine microbial biomass; the plant community metrics (i.e., percent cover, Shannon-Wiener, grass biomass, and carbon/nitrogen in leaf and biomass) and soil properties (i.e., soil moisture, soil temperature, bulk density, organic carbon, total nitrogen, and available nitrogen) were determined. The results showed that carbon/nitrogen in microbial biomass was higher at medium altitude and was positively related to carbon and nitrogen in both soil and grass biomass along the altitudinal gradients. Soil bacterial alpha diversity was significantly higher at medium altitude but fungal alpha diversity did not affected by altitudinal gradients; the effect of altitudinal gradients on bacterial beta diversity was larger than that on fungal beta diversity, although both groups were significantly affected by altitudinal gradients. Moreover, Alpha - proteobacteria , Beta - proteobacteria , and Gemmatimonadetes were significantly more abundant in higher altitude than in lower altitude, both Acidobacteria and Actinobacteria significantly declined with increasing altitude; other bacterial taxa such as Chloroflexi , Nitrospirae , Gamma - proteobacteria , and Delta - proteobacteria were significantly higher at medium altitudes. For fungal taxa, Basidiomycota and Ascomycota were the dominant phyla and responded insignificantly to the altitudinal gradients. The responses of microbial alpha diversity were mostly associated with plant Shannon index, organic carbon, and total nitrogen, whereas microbial beta diversity and composition mainly depended on soil moisture and temperature. Overall, these results suggest that soil bacteria rather than fungi can reflect changes in plant and soil characteristics along altitudinal gradients. [ABSTRACT FROM AUTHOR]

Rainfall reductions influence ecosystem processes through impacts on the microbial community. However, the response of soil microbial community and their interactions with ecosystem processes remain unclear. In this study, we conducted a meta-analysis to synthesize the response of soil total microbial biomass and community composition to experimental rainfall reductions and the implications for soil carbon dynamics. The results showed that rainfall reductions significantly decreased soil total microbial biomass and bacterial abundance, but no significant effects on fungal abundance were observed. While, within bacterial and fungal groups, rainfall reductions only significantly influenced the relative abundance of Proteobacteria, Gemmatimonadetes, and Chloroflexi , but did not affect Gram-positive bacteria (GP) , Gram-negative bacteria (GN), Actinomycetes, Arbuscular mycorrhizal fungi, and other sequenced bacterial phyla. These contrasting responses suggested that rainfall reductions had major effects on total microbial biomass but minor effects on community compositions. Further analysis showed that the direction and magnitude of total microbial biomass responses were mainly explained by the size of rainfall reductions rather than the duration. Particularly, higher decreases in total microbial biomass were observed in sites where more rainfall was excluded. Reductions in total microbial biomass were larger in forests with higher aridity index (AI) than in grass/shrublands with lower AI, and stronger reductions in microbial biomass were observed at higher mean annual precipitation (MAP)/sites with higher AI. Moreover, both soil organic carbon (SOC) and soil respiration (SR) significantly declined under reduced rainfall experiments and had positive relationships with changes in total microbial biomass, especially in humid lands (AI≥ 0.65). The microbial responses to aridity levels indicated that soil carbon in humid lands may be highly susceptible to future drought scenarios. This meta-analysis highlighted the importance of considering the size of rainfall reductions and aridity levels when modeling and projecting soil carbon dynamics. [ABSTRACT FROM AUTHOR]

[Display omitted] • Secondary succession on the Loess Plateau decreased soil microbial C limitation. • Microbes were N-limited in the first 10-year of succession but then were P-limited. • Soil physicochemical properties mainly drive microbial element limitations changes. • Element limitations depend more on plant diversity than plant family composition. • Soil bacteria respond more sensitively to microbial element limitations than fungi. Disproportionate inputs of carbon (C), nitrogen (N), and phosphorus (P) following plant succession typically induce microbial resource limitations. Such limitations are directly relevant to the fate of soil element cycles. However, it is not well understood how generalizable patterns of resource constraints act on soil microbial communities during the natural succession of abandoned farmlands, nor their driving forces. To this end, the potential activities of C-, N-, and P-acquiring enzymes, soil properties, plant characteristics, and soil microbial community composition and diversity were investigated along a 30-year successional chronosequence following agricultural abandonment on the Chinese Loess Plateau. Ecoenzymatic stoichiometry revealed a decrease in C limitation following succession, and soil microorganisms were primarily limited by N in the 10th year of succession but limited by P in the 20th and 30th years. Soil physicochemical properties cumulatively contributed 62.59% and 59.33% to the variations in microbial C and nutrient limitations, respectively. In particular, soil organic C content, C:N and C:P ratios, microbial biomass, and pH strongly affected microbial element limitations. Plant characteristics had minor effects on microbial resource constraints, accounting for 37.41% and 40.67% of the variance in microbial C and nutrient limitations, respectively. In comparison, plant diversity affected soil microbial element limitations more than plant family composition. Notably, the bacterial alpha and beta diversities, as well as the relative abundances of dominant phyla, such as Actinobacteria , Bacteroidetes , Proteobacteria , Acidobacteria , Gemmatimonadetes , and Planctomycetes , were significantly more associated with resource limitations than soil fungal community. Collectively, these findings suggest that the variable patterns of microbial element limitations were predominantly the result of changing soil properties across distinct successional stages, with soil bacteria responding more strongly than fungi to changes in microbial element limitations. [ABSTRACT FROM AUTHOR]

Soil Phosphorous (P) availability is a limiting factor for plant growth and regulates biological metabolism in plantation ecosystems. The effect of variations in soil microbial P cycling potential on the availability of soil P during succession in plantation ecosystems is unclear. In this study, a metagenomics approach was used to explore variations in the composition and diversity of microbial P genes along a 45-year recovery sequence of Robinia pseudoacacia on the Loess Plateau, as well soil properties were measured. Our results showed that the diversity of P cycling genes (inorganic P solubilization and organic P mineralization genes) increased significantly after afforestation, and the community composition showed clear differences. The gcd and ppx genes were dominant in inorganic P transformation, whereas phnM gene dominated the transformation of organic P. The abundance of genes involved in inorganic P solubilization and organic P mineralization was significantly positively correlated with P availability, particularly for phnM , gcd , ppx , and phnI genes, corresponding to the phyla Gemmatimonadetes, Acidobacteria, Bacteroidetes , and Planctomycetes. The critical drivers of the microbial main genes of soil P cycling were available P (AP) and total N (TN) in soil. Overall, these findings highlight afforestation-induced increases in microbial P cycling genes enhanced soil P availability. and help to better understand how microbial growth metabolism caused by vegetation restoration in ecologically fragile areas affects the soil P cycling. • The diversity of microbes with P cycling genes increased by afforestation. • PhnM , gcd , ppx , and phnl genes dominated the increase of soil P availability. • The key drivers of the microbial main genes of soil P cycling were AP and TN. [ABSTRACT FROM AUTHOR]