A Global Spectral Element Model for Poisson Equations and Advective Flow over a Sphere

A global spherical Fourier-Legendre spectral element method is proposed to solve Poisson equations and advective flow over a sphere. In the meridional direction, Legendre polynomials are used and the region is divided into several elements. In order to avoid coordinate singularities at the north and south poles in the meridional direction, Legendre-Gauss-Radau points are chosen at the elements involving the two poles. Fourier polynomials are applied in the zonal direction for its periodicity, with only one element. Then, the partial differential equations are solved on the longitude-latitude meshes without coordinate transformation between spherical and Cartesian coordinates. For verification of the proposed method, a few Poisson equations and advective flows are tested. Firstly, the method is found to be valid for test cases with smooth solution. The results of the Poisson equations demonstrate that the present method exhibits high accuracy and exponential convergence. High- precision solutions are also obtained with near negligible numerical diffusion during the time evolution for advective flow with smooth shape. Secondly, the results of advective flow with non-smooth shape and deformational flow are also shown to be reasonable and effective. As a result, the present method is proved to be capable of solving flow through different types of elements, and thereby a desirable method with reliability and high accuracy for solving partial differential equations over a sphere.

Environmental selection and evolutionary process jointly shape genomic and functional profiles of mangrove rhizosphere microbiomes

Mangrove reforestation with introduced species has been an important strategy to restore mangrove ecosystem functioning.However,how such activities affect microbially driven methane(CH4),nitrogen(N),and sulfur(S)cycling of rhizosphere microbiomes remains unclear.To understand the effect of environmental selection and the evolutionary process on microbially driven biogeochemical cycles in native and introduced mangrove rhizospheres,we analyzed key genomic and functional profiles of rhizosphere microbiomes from native and introduced mangrove species by metagenome sequencing technologies.Compared with the native mangrove(Kandelia obovata,KO),the introduced mangrove(Sonneratia apetala,SA)rhizosphere microbiome had significantly(p<0.05)higher average genome size(AGS)(5.8 vs.5.5 Mb),average 16S ribosomal RNA gene copy number(3.5 vs.3.1),relative abundances of mobile genetic elements,and functional diversity in terms of the Shannon index(7.88 vs.7.84)but lower functional potentials involved in CH4 cycling(e.g.,mcrABCDG and pmoABC),N2 fixation(nifHDK),and inorganic S cycling(dsrAB,dsrC,dsrMKJOP,soxB,sqr,and fccAB).Similar results were also observed from the recovered Proteobacterial metagenome-assembled genomes with a higher AGS and distinct functions in the introduced mangrove rhizosphere.Additionally,salinity and ammonium were identified as the main environmental drivers of functional profiles of mangrove rhizosphere microbiomes through deterministic processes.This study advances our understanding of microbially mediated biogeochemical cycling of CH_(4),N,and S in the mangrove rhizosphere and provides novel insights into the influence of environmental selection and evolutionary processes on ecosystem functions,which has important implications for future mangrove reforestation.

长期磷添加对热带森林土壤磷酸单酯酶与磷酸二酯酶活性比值的影响

热带森林土壤微生物可以通过改变不同类型的磷酸酶活性来适应低磷的环境。以往的研究认为,低磷环境中土壤微生物更倾向于分解有机磷单酯键而非二酯键。因此,磷酸单酯酶(PME)的活性变化对生态系统磷输入的响应可能更敏感,其与磷酸二酯酶(PDE)活性的比值在磷输入后将显著降低。为了检验土壤微生物在低磷的热带森林中对不同磷酸酶的“投资”策略,我们在鼎湖山3种热带森林进行了长达10年的磷添加实验。与以往的研究不同,本研究发现长期磷添加没有改变原生林与次生林的PME:PDE比值,但显著提高了人工林土壤PME:PDE比值。结果表明,长期磷添加可能减少了凋落物或穿透雨来源的PDE,从而使其土壤PDE活性下降较PME降低更快,因而PME:PDE比值未能降低。

Coastal blue carbon in China as a nature-based solution toward carbon neutrality

To achieve the Paris Agreement,China pledged to become“Carbon Neutral”by the 2060s.In addition to massive decarbonization,this would require significant changes in ecosystems toward negative CO_(2)emissions.The ability of coastal blue carbon ecosystems(BCEs),including mangrove,salt marsh,and seagrass meadows,to sequester large amounts of CO_(2)makes their conservation and restoration an important“nature-based solution(NbS)”for climate adaptation and mitigation.In this review,we examine how BCEs in China can contribute to climate mitigation.On the national scale,the BCEs in China store up to 118 Tg C across a total area of 1,440,377 ha,including over 75%as unvegetated tidal flats.The annual sedimental C burial of these BCEs reaches up to 2.06 Tg C year^(−1),of which most occurs in salt marshes and tidal flats.The lateral C flux of mangroves and salt marshes contributes to 1.17 Tg C year^(−1)along the Chinese coastline.Conservation and restoration of BCEs benefit climate change mitigation and provide other ecological services with a value of$32,000 ha^(−1)year^(−1).The potential practices and technologies that can be implemented in China to improve BCE C sequestration,including their constraints and feasibility,are also outlined.Future directions are suggested to improve blue carbon estimates on aerial extent,carbon stocks,sequestration,and mitigation potential.Restoring and preserving BCEs would be a cost-effective step to achieve Carbon Neutral by 2060 in China despite various barriers that should be removed.

Coastal blue carbon： Concept, study method, and the application to ecological restoration

Coastal blue carbon refers to the carbon taken from atmospheric CO2; fixed by advanced plants(including salt marsh,mangrove, and seagrass), phytoplankton, macroalgae, and marine calcifiers via the interaction of plants and microbes; and stored in nearshore sediments and soils; as well as the carbon transported from the coast to the ocean and ocean floor. The carbon sequestration capacity per unit area of coastal blue carbon is far greater than that of the terrestrial carbon pool. The mechanisms and controls of the carbon sink from salt marshes, mangroves, seagrasses, the aquaculture of shellfish and macroalgae, and the microbial carbon pump need to be further studied. The methods to quantify coastal blue carbon include carbon flux measurements, carbon pool measurements, manipulative experiments, and modeling. Restoring, conserving, and enhancing blue carbon will increase carbon sinks and produce carbon credits, which could be traded on the carbon market. The need to tackle climate change and implement China's commitment to cut carbon emissions requires us to improve studies on coastal blue carbon science and policy. The knowledge learned from coastal blue carbon improves the conservation and restoration of salt marshes,mangroves, and seagrasses; enhances the function of the microbial carbon pump; and promotes sustainable aquaculture, such as ocean ranching.

Species-dependent responses of soil microbial properties to fresh leaf inputs in a subtropical forest soil in South China

Aims Forest disturbance from extreme weather events due to climate change could increase the contribution of fresh green leaves to the litter layer of soil and subsequently alter the composition and activity of the soil microbial properties and soil carbon cycling.The objective of this study was to compare the effect of naturally fallen litter and fresh leaves on the soil microbial community composition and their activities.Methods Fresh leaves and normal fallen litter were collected from four tree species(Pinus elliottii,Schima superba,Acacia mangium,A.auriculaeformis)in subtropical China and mixed with soil.Soil microbial community composition was determined using PLFAs,and its activity was quantified by soil respiration.During a 12-month period,the decomposition rate of litter was measured bimonthly using a litterbag method.Soil microbial samples were collected after 6 and 12 months.Soil respiration was measured monthly.Important Findings We found that fresh leaves decomposed faster than their conspecific fallen litter.Although total microbial biomass and bacterial biomass were similar among treatments,soil fungal biomass was higher in fresh leaf than fallen litter treatments,resulting in greater values of the Fungal phospholipid fatty acids(PLFAs)/Bacterial PLFAs ratio.Fungal PLFA values were greater for Schima superba than the other species.The effect of litter type on soil respiration was species-dependent.Specifically,fallen litter released 35%more CO_(2) than fresh leaves of the conifer P.elliottii.The opposite pattern was observed in the broadleaf species whose fresh leaf treatments emitted 17%–32%more CO_(2) than fallen litter.Given future predictions that global climate change will cause more disturbances to forests,these results indicate that conifer and broadleaf forests in subtropical China may respond differently to increased fresh litter inputs,with net soil microbial respiration decreasing in conifer forests and increasing in broadleaf forests.

A review of intensified conditioning of personal micro-environments:Moving closer to the human body

Various systems and technologies have been developed in recent years to fulfil the growing needs of high-performance HVAC systems with better performance of energy efficiency,thermal comfort,and occupancy health.Intensified conditioning of human occupied areas and less intensified conditioning of surrounding areas are able to effectively improve the overall satisfaction by individual control of personalized micro-environments and also,achieve maximum energy efficiency.Four main concepts have been identified chronologically through the devel-opment of personal environmental conditioning,changing the intensified conditioning area closer to the human body and enhancing conditioning efforts,namely the task ambient conditioning(TAC)system,personal envi-ronmental control system(PECS),personal comfort system(PCS),and the personal thermal management(PTM)system.This review follows a clue of the concept progress and system evaluation,summarizes important findings and feasible applications,current gaps as well as future research needs.