Nitrate-dependent anaerobic oxidation of methane (AOM) is a new pathway to reduce methane emissions from paddy ecosystems. The elevated atmospheric CO2 concentration can affect methane emissions from paddy ecosystems, but its impact on the process of nitrate-dependent AOM is poorly known. Based on the automatic CO2 control platform with open top chambers and the 13CH4 stable isotope experiments, the responses of the activity of nitrate-dependent AOM, abundance and community composition of Candidatus Methanoperedens nitroreducens (M. nitroreducens)-like archaea to the gradual increase of CO2 concentration were investigated in paddy fields. We set up two CO2 concentration treatments, including an ambient CO2 and a gradual increase of CO2(increase of 40 μL·L-1 per year above ambient CO2 concentration until 160 μL·L-1). The results showed the nitrate-dependent AOM rate of 0.7-11.3 nmol CO2·g-1·d-1 in the studied paddy fields, and quantitative PCR showed the abundance of M. nitroreducens-like archaeal mcrA genes of 2.2×106-8.5×106 copies·g-1. Compared to the ambient CO2 treatment, the slow elevated CO2 treatment enhanced the nitrate-dependent AOM rate and stimulated the abundance of M. nitroreducens-like archaea, particularly in 5-10 cm soil layer. The gradual increased CO2 concentration treatment did not change the community composition of M. nitroreducens-like archaea, but significantly decreased their diversity. The soil organic carbon content was an important factor influencing the nitrate-dependent AOM process. Overall, our results showed that the gradual increase of CO2 concentration could promote the nitrate-dependent AOM, suggesting its positive role in mitigating methane emissions from paddy ecosystems under future climate change.
Soil aggregates are the essential building blocks of soil,which impact the retention and distribution of water,air,heat,and nutrients.Binding materials play a pivotal role in the formation of soil aggregates.However,the specific functions of different types of binding materials as well as the mechanisms of the complex interactions in the formation of these aggregates still lack a systematic summary.This article reviews the key theories related to soil aggregates and sorts out types,forms,transformations,and interaction mechanisms of binding materials in soil aggregates under different geographical contexts and human activities.It also describes the effects of binding materials(e.g.,organic matter,minerals,roots,organisms and their derivatives such as Extracellular Polymeric Substances)on the structure and stability of soil aggregates.Furthermore,it introduces models illustrating the self-organization process driven by binding materials within soil aggregates and elucidates the mechanisms of the formation and transformation of soil aggregates.Finally,the future development of soil aggregates is suggested.Specifically,future research could investigate the in-situ analysis of soil aggregates,quantitative description of the formation process of soil aggregates,spatial structure of soil aggregates at the landscape scale in relation to its stability,and development of product/technology in cultivating good soil aggregates for applications.This research holds significant scientific and practical value in promoting the development of healthy soil aggregates,unraveling the processes of soil elemental cycling and evolution,and enhancing overall soil quality and productivity.
Non-point source pollution from agriculture is characterized by its dispersed and random occurrence,uncertain discharge,fluctuating concentrations,diverse pollutant types,and widespread,high-volume impact,making its management a global challenge.At present,the prevention and control of non-point source pollution in China remains a challenge due to unclear overall pollution levels,and the estimation of non-point source pollution load varies greatly among different departments or researchers.Based on decades of site-specific experiments and holistic observational data,it was believed that even though both the national pollution census data and estimations from researchers have overestimated the proportion of pollution emissions from plantations in the total amount of non-point source pollution,the total emissions from plantation remain high and must be given adequate attention and control.Drawing on more than 30 years of experience in controlling non-point source pollution in China,scholars from the Institute of Soil Science,Chinese Academy of Sciences have proposed the 3R(Reduce-Retain-Restore)and 4R(Reduce-Retain-Reuse-Restore)strategies for agricultural non-point source pollution control.Accompanied by upgrades in prevention and control technology,optimization of combinations,technological productization,and equipping the 4R strategy has gradually evolved and expanded into 4R+,providing theoretical support and practical guidance for the control of non-point source pollution in China.After being implemented in some typical areas,these strategies have resulted in successful experiences and case studies in controlling agricultural non-point source pollution.Nevertheless,the prevention and control of agricultural non-point source pollution still faces many challenges.A deeper understanding of the interaction mechanisms between soil and pollutants is pivotal.Moreover,to achieve efficient resource recycling,it is imperative to enhance the purification and recovery rates of key pollutants such as nitrogen and phosphorus,ensuring that agricultural productivity is increased while simultaneously reducing the environmental pollutant load.
Farmland quality construction is a strategic requirement for ensuring food security in China.There is an urgent need to address issues such as soil acidification,salinization,infertility,and declining biological functions for medium to low-yield farmland,in order to comprehensively enhance farmland productivity in China.Based on long-term observation,research,and demonstration,the Institute of Soil Science,Chinese Academy of Sciences has clarified the evolution rules and degradation control mechanisms of soil quality for major cultivated soil types such as fluvo-aquic soil,red soil,and saline-alkaline soil,and developed the theories and technical systems for farmland quality cultivating in different agricultural areas.For fluvo-aquic soil,the formation mechanisms of the internal stability for soil fertility through the synergetic linkage among organic matter,aggregate,and microbe were clarified,the sensing equipment for monitoring farmland soil and crop information were developed,and the models to integrate the construction of fertile cultivated layer and the balanced enhance of crop yield at large-scale were established.For red soil,the mechanisms for inhibiting soil acidification by improving acid buffering capacity and microbial keystone taxa-driven nutrient transformation were revealed,the technologies for synergistic inhibition and resistance of soil acidification and biological fertility cultivation of soil macro-aggregates were developed,and the ecological modes for farmland quality and productivity enhancement in Jiangxi Province were classified and established.For saline-alkali soil,the nitrogen migration and conversion processes associated with soil water-salt management were clarified,the synergistic mechanism and key technologies of salinization obstacles reduction and nutrient enhancement were developed,the soil accelerating fertility cultivation mode and the soil salinization ecological remediation mode were innovated for the coastal region and Hetao Irrigation District respectively.Future research should focus on farmland quality investigation and construction management,farmland soil obstacle remediation and productivity improvement,and soil health management and ecological protection.We need to break through the technical bottleneck for soil obstacle remediation,develop a series of conditioners and biological fertilizer products,improve the implementation rate of regional management modes,and finally establish a systematic solution for improving farmland quality and sustainably utilizing farmland resources in China.
[Objective]The ecology of mining areas in the Loess Plateau is relatively fragile,while the vegetation restoration is closely related to soil microbe-mediated nutrient cycling.This study was designed to clarify the influence and regulatory roles of vegetation restoration on the functional groups related to soil carbon,nitrogen and phosphorus cycles,which are significantly important to rebuilding the ecological resilience and self-sustaining mechanism of mining areas.[Method]In this study,high-throughput Qpcr chip technology,random forest model and structural equation model were used to reveal the changes and mutual feeding mechanism of soil characteristics,enzyme activities,carbon,nitrogen and phosphorus functional groups under different vegetation restoration modes of Antaibao open-pit reclamation waste dump on the Loess Plateau.[Result]The results showed that Caragana korshinskii(bushwood,BL),Pinus tabuliformis(coniferous forest,CF),Robinia pseudoacacia(broad-leaved forest,BF)and Robinia pseudoacacia + Ulmus pumila(mixed forest,MF)were superior to soil nutrient accumulation compared with Populus simonii forest(CK).Compared to CF,soil organic carbon(SOC)of BL,BF and MF increased by 82.26%,168%and 56.65%,respectively.The total nitrogen(TN)of BL,BF and MF enhanced by 68.31%,130%and 46.75%comparing with CF,while the available phosphorus(AP)contents increased by 10.41%,27.65%and 20.89%,respectively.Nevertheless,these were still significantly lower than that of CK(P<0.05).The soil catalase(CAT)activities of BL,CF,BF and MF increased by 95.6%,101.0%,46.4%and 120.0%respectively,and are significantly higher than that of CK(P<0.05).Also,the soil β-glucosidase(BG)and leucine aminopeptidase(LAP)activities decreased significantly(P<0.05).The β-glucosidase activities of BL,CF,BF and MF decreased by 66.5%,67.0%,58.9%and 59.8%,while the leucine aminopeptidase activities decreased by 57.8%,67.7%,78.0%and 67.7%,respectively.The different modes of vegetation restoration significantly changed the relative abundances of functional groups related to carbon,nitrogen and phosphorus(P<0.05),whereas the variation tendencies always keep a consistent correspondence.The functional groups related to carbon,nitrogen and phosphorus were significantly positively correlated with soil nitrate nitrogen(P<0.001),but they presented negative correlations with ammonium nitrogen(P<0.01).The functional groups involved in the carbon cycle,nitrification process and organic phosphorus mineralization were significantly positively correlated with available phosphorus(P<0.01).In addition,results of the structural equation model showed that vegetation restoration could directly affect CAT and AP,thereby regulating the carbon,nitrogen and phosphorus cycle.Otherwise,the vegetation restoration could affect soil AP indirectly,thereupon then regulating the abundances of carbon,nitrogen and phosphorus functional groups,together with other soil characteristics,such as nitrate nitrogen or ammonium nitrogen.[Conclusion]This study might help deepen the knowledge about soil microbiology mechanism of vegetation restoration,which will furtherly help the ecological restoration of damaged mines in the Loess Plateau.
