氮添加对森林生态系统植物–土壤–微生物化学计量比影响的研究进展

人类活动引起大气氮沉降速率增加的问题虽有所改善,但仍影响着森林生态系统的物质循环。模拟施氮对中国森林生态系统化学计量比的影响多集中于植物、土壤和微生物的单一分析,对植物–土壤–微生物碳(C)、氮(N)和磷(P)化学计量特征及其耦合关系的研究较少。本文通过整合先前的研究结果,总结了外源氮输入后植物–土壤–微生物C、N和P化学计量特征的响应,结果发现,低浓度施氮有利于土壤主要养分和微生物量的积累,促进植物和微生物养分的吸收利用,高浓度施氮则相反。但对于C和P元素,则表现出不同的结果,C元素随着外源氮的输入而增加或不发生变化,而P元素则充满不确定性,表现为增加、不变或减少等3种结果,这主要是由于养分元素的限制和环境因素的变化所致。通过本文系统的整合,补充了森林生态系统中植物–土壤–微生物C、N、P化学计量特征耦合领域的知识缺失,可为深入认识和理解未来氮沉降对生态系统生物地球化学循环的影响提供理论依据。

土壤溶解性有机碳对气候变暖的响应研究进展

针对土壤溶解性有机碳(DOC)特性及其在气候变暖背景下的响应机制这一土壤碳循环研究的关键问题进行综述。首先阐述土壤DOC的特性,并总结其采集和测定方法。土壤DOC主要来源于土壤有机碳的溶解、植物根系和微生物分泌物与残体转化等过程,其浓度和组成往往随土层深度和时间发生变化。多种采样方法(如负压法)与分析手段(如傅里叶变换离子共振回旋质谱仪)用于探讨土壤DOC对增温的响应及其机制。进一步梳理有关植物、微生物及土壤性质对土壤DOC特性的影响及其机制的文献,认为增温不仅能直接改变土壤DOC的浓度,还可以通过影响植物、微生物群落以及土壤理化性质等因素,间接地改变土壤DOC的特性。未来的研究中应加强对土壤溶解性有机碳的土层迁移与时间动态的关注,以便完善土壤碳模型,提升未来气候变暖情景下全球碳循环过程变化的预测精度。

Effects of Different Vegetable Planting Modes on Soil Microbial Flora and Enzyme Activity

To investigate the effects of different vegetable growing regions and planting modes on soil quality,soils in high,medium and low altitude areas of Guizhou were respectively sampled under different vegetable efficient planting modes,and the variations of soil microbial flora and enzyme activities were analyzed. The soil microbial count and total bacteria of the vegetable efficient cultivation mode were significantly higher than that of the control （traditional planting mode） in each planting area,and the microbial diversity index was also improved to varying de- grees.The soil phosphatase,catalase and urease activities of the vegetable efficient planting mode were higher than that of the control.The soil catalase and urease activities were higher than that of the control by 1.37-1.44 and 1.51-2.80 times. Application of vegetable efficient planting mode in different regions will help to im- prove the soil quality in a given period.

Study on the Surface Soil Micro-biomass Carbon of Kinds of Vegetation Types in Dagu Estuary Wetland

A field experiment was carried out to explore surface soil mircro-biomass carbon （MBC）. The results showed that the difference of soil MBC was significant among three vegetation types in five sample spots in July. The order of surface soil MBC was： Aquaculture pond reed （sample 2）〉 reed of river bank （sample 5）〉 sea- plant（sample 5）〉 river flat（sample 4）〉 The alkaline（sample 1）. There is a very sig- nificant correlation among the soil MBC, the water content of soil and the content of organic matter. Among wetland plants, reed is kind of plant content of high ground biomass and below-ground biomass,especially the MBC planted in wetland is high- er, which shows that compared with common plants, reed is more conducive to the accumulation of soil MBC and has an important effect to wetland protecting and re- covery of function of ecosystem.

Phenolic Acids in Plant-Soil-Microbe System: A Review

Phenolic acids are very common compounds in pedosphere. Theobjective of this review was to summarize the current knowledge ofthe behaviors of phenolic acids in plant-soil microbe system. Whenphenolic acids originated form leaching, decomposition and exudationof living and dead plant tissues enter soils, they can reactphysiochemically with soil particle surfaces and/or incorporate intohumic matter. Phenolic acids desorbed from soil particle surfaces andremained in solution phase can be utilized by microbe as carbonsources and absorbed by plants.

Soil Microbial Activity During Secondary Vegetation Succession in Semiarid Abandoned Lands of Loess Plateau

To show the vegetation succession interaction with soil properties, microbial biomass, basal respiration, and enzyme activities in different soil layers （0-60 cm） were determined in six lands, i.e., 2-, 7-, 11-, 20-, and 43-year-old abandoned lands and one native grassland, in a semiarid hilly area of the Loess Plateau. The results indicated that the successional time and soil depths affected soil microbiological parameters significantly. In 20-cm soil layer, microbial biomass carbon （MBC）, microbial biomass nitrogen （MBN）, MBC/MBN, MBC to soil organic carbon ratio （MBC/SOC）, and soil basal respiration tended to increase with successional stages but decrease with soil depths. In contrast, metabolic quotient （qCO2） tended to decrease with successional stages but increase with soil depths. In addition, the activities of urease, catalase, neutral phosphatase, β-fructofuranosidase, and earboxymethyl cellulose （CMC） enzyme increased with successional stages and soil depths. They were significantly positively correlated with microbial biomass and SOC （P 〈 0.5）, whereas no obvious trend was observed for the polyphenoloxidase activity. The results indicated that natural vegetation succession could improve soil quality and promote ecosystem restoration, but it needed a long time under local climate conditions.

Mineral weathering and element cycling in soil-microorganism-plant system

Soil is an essential part of the critical zone,and soil-microbe-plant system serves as a key link among lithosphere,biosphere,atmosphere and hydrosphere.As one of the habitats with the richest biodiversity,soil plays a critical role in element biogeochemistry on the earth surface(weathered crust).Here we review the soil biological processes that are relevant to mineral weathering,element cycling,and transformation,with an emphasis on rock weathering mediated by soil microbes,plant root and the rhizosphere.

Soil-Plant-Microbe Interactions in Stressed Agriculture Management:A Review

The expected rise in temperature and decreased precipitation owing to climate change and unabated anthropogenic activities add complexity and uncertainty to agro-industry. The impact of soil nutrient imbalance, mismanaged use of chemicals, high temperature, flood or drought, soil salinity, and heavy metal pollutions, with regard to food security, is increasingly being explored worldwide. This review describes the role of soil-plant-microbe interactions along with organic manure in solving stressed agriculture problems. Beneficial microbes associated with plants are known to stimulate plant growth and enhance plant resistance to biotic （diseases） and abiotic （salinity, drought, pollutions, etc.） stresses. The plant growth-promoting rhizobemteria （PGPR） and mycorrhizae, a key component of soil microbiota, could play vital roles in the maintenance of plant fitness and soil health under stressed environments. The application of organic manure as a soil conditioner to stressed soils along with suitable microbial strains could further enhance the plant-microbe associations and increase the crop yield. A combination of plant, stress-tolerant microbe, and organic amendment represents the tripartite association to offer a favourable environment to the proliferation of beneficial rhizosphere microbes that in turn enhance the plant growth performance in disturbed agro-ecosystem. Agriculture land use patterns with the proper exploitation of plant-microbe associations, with compatible beneficial microbial agents, could be one of the most effective strategies in the management of the concerned agriculture lands owing to climate change resilience. However, the association of such microbes with plants for stressed agriculture management still needs to be explored in greater depth.

Responses of Soil Microbial Activity and Biomass to Salinity After Repeated Additions of Plant Residues

Microbial adaptation to salinity can be achieved through synthesis of organic osmolytes,which requires high amounts of energy;however,a single addition of plant residues can only temporarily improve energy supply to soil microbes.Therefore,a laboratory incubation experiment was conducted to evaluate the responses of soil microbes to increasing salinity with repeated additions of plant residues using a loamy sand soil with an electrical conductivity in saturated paste extract(EC_e) of 0.6 dS m^(-1).The soil was kept non-saline or salinized by adding different amounts of NaCl to achieve EC_e of 12.5,25.0 and 50.0 dS m^(-1).The non-saline soil and the saline soils were amended with finely ground pea residues at two rates equivalent to 3.9 and 7.8 g C kg^(-1) soil on days 0,15 and29.The soils receiving no residues were included as a control.Cumulative respiration per g C added over 2 weeks after each residue addition was always greater at 3.9 than 7.8 g C kg^(-1) soil and higher in the non-saline soil than in the saline soils.In the saline soils,the cumulative respiration per g C added was higher after the second and third additions than after the first addition except with3.9 g C kg^(-1) at EC_e of 50 dS m^(_1).Though with the same amount of C added(7.8 g C kg^(-1)),salinity reduced soil respiration to a lesser extent when 3.9 g C kg^(-1) was added twice compared to a single addition of 7.8 g C kg^(-1).After the third residue addition,the microbial biomass C concentration was significantly lower in the soils with EC_e of 25 and 50 dS m^(_1) than in the non-saline soil at3.9 g C kg^(-1),but only in the soil with EC_e of 50 dS m^(-1) at 7.8 g C kg^(-1).We concluded that repeated residue additions increased the adaptation of soil microbial community to salinity,which was likely due to high C availability providing microbes with the energy needed for synthesis of organic osmolytes.

Soil microbial properties under different vegetation types on Mountain Han

This study investigated the influence of broadleaf and conifer vegetation on soil microbial communities in a distinct vertical distribution belt in Northeast China.Soil samples were taken at 0-5,5-10 and 10-20 cm depths from four vegetation types at different altitudes,which were characterized by poplar(Populus davidiana)(1250-1300 m),poplar(P.davidiana) mixed with birch(Betula platyphylla)(1370-1550 m),birch(B.platyphylla)(1550-1720 m),and larch(Larix principis-rupprechtii)(1840-1890 m).Microbial biomass and community structure were determined using the fumigation-extraction method and phospholipid fatty acid(PLFA) analysis,and soil fungal community level physiological profiles(CLPP) were characterized using Biolog FF Microplates.It was found that soil properties,especially soil organic carbon and water content,contributed significantly to the variations in soil microbes.With increasing soil depth,the soil microbial biomass,fungal biomass,and fungal catabolic ability diminished;however,the ratio of fungi to bacteria increased.The fungal ratio was higher under larch forests compared to that under poplar,birch,and their mixed forests,although the soil microbial biomass was lower.The direct contribution of vegetation types to the soil microbial community variation was 12%.If the indirect contribution through soil organic carbon was included,variations in the vegetation type had substantial influences on soil microbial composition and diversity.

Effect of Rhizobacterium Rhodopseudomonas palustris Inoculation on Stevia rebaudiana Plant Growth and Soil Microbial Community

There is an increasing concern that the continuous use of chemical fertilizers might lead to harmful effects on soil ecosystem.Accordingly, a biocompatible approach involving inoculation of beneficial microorganisms is presented to promote plant growth and simultaneously minimize the negative effect of chemical fertilizers. In this study, Rhodopseudomonas palustris, a plant growth-promoting rhizobacterium(PGPR), was inoculated into both fertilized and unfertilized soils to assess its influence on Stevia rebaudiana plant growth and microbial community in rhizosphere soils in a 122-d field experiment. Soil enzyme assays(dehydrogenase, urease, invertase, and phosphomonoesterase), real-time quantitative polymerase chain reaction(RT-_qPCR), and a high-throughput sequencing technique were employed to determine the microbial activity and characterize the bacterial community. Results showed that the R.palustris inoculation did not significantly influence Stevia yields and root biomass in either the fertilized or unfertilized soil. Chemical fertilization had strong negative effects on soil bacterial community properties, especially on dehydrogenase and urease activities.However, R. palustris inoculation counteracted the effect of chemical fertilizer on dehydrogenase and urease activities, and increased the abundances of some bacterial lineages(including Bacteroidia, Nitrospirae, Planctomycetacia, Myxococcales, and Legionellales). In contrast, inoculation into the unfertilized soil did not significantly change the soil enzyme activities or the soil bacterial community structure. For both the fertilized and unfertilized soils, R. palustris inoculation decreased the relative abundances of some bacterial lineages possessing photosynthetic ability, such as Cyanobacteria, Rhodobacter, Sphingomonadales, and Burkholderiales. Taken together, our observations stress the potential utilization of R. palustris as PGPR in agriculture, which might further ameliorate the soil microbial properties in the long run.

The response of soil respiration to different N compounds addition in a saline-alkaline grassland of northern China

The increase in atmospheric nitrogen(N)deposition has profound effects on soil respiration(SR).However,the responses of SR to the addition of different N compounds,particularly in saline-alkaline grasslands remain unclear.A 3-year controlled field experiment was conducted to investigate the responses of SR to different N compounds(NH,NO,(NH),SO,and NH,HCO,)during the growing seasons in a saline-alkaline grassland located in the agro-pastoral ecotone of northern China.Our results demonstrated that SR showed a bimodal pattern and a significant interannual diference that was regulated by air or soil temperature and precipitation.Nitrogen addition had a significant effect on SR,and the effect of N addition on SR varied yearly,which was related to seasonal precipitation.The mean SR across 3 years(2017-2019)was increased by 19.9%,13.0%and 16.6%with the addition of NH,NO,(NH,),SO,and NH,HCO3,respectively.The highest effect of NH,NO3 addition on SR across 3 years was ascribed to the highest aboveground net primary production,belowground net primary production(BNPP)and soil NO,-concentrations.SR(C loss)was significantly increased while plant productivity(C input)did not significantly change under NH,HCO,addition,indicating a decrease in C sequestration.In addition,BNPP was the main direct factor influencing SR in this saline-alkaline grassland,and soil salinization(e.g.soil base cations and pH)indirectly affected SR through soil microorganisms.Notably,NH,NO,addition overestimated the response of SR to N addition,and different N compounds should be considered,especially in saline-alkaline grassland.

Effects of plant coverage on shrub fertile islands in the Upper Minjiang River Valley

The patchy distribution of vegetation in dry land results in well-documented "fertile islands". However, the response of shrub fertile islands to plant recovery and the underlying mechanisms, such as the linkage plant and soil properties, remain unknown.We sampled soils from areas with three different plant coverages(25%, 45%, and 75%) and three of their adjacent inter-plants to investigate soil physicochemical and microbial properties in the upper Minjiang River arid valley. The results showed that these factors were influenced by the persistence of plants that contrasted with the inter-plant interspaces. We found fertile islands in under-plant soil that were enhanced with increasing plant coverage, from 25% to 45% and 75%; however, there were no significant differences between 45% and 75% plant coverage apart from the soil clay content and the fungi to bacteria ratio. The soil microbial communities in under-plant soil were strongly influenced by the total soil carbon(TC), soil organic carbon(SOC),and available nitrogen(AN), whereas the microbial communities in inter-plant soil were primarily constrained by the AN and available phosphorous(AP). Moreover, the inter-plant soil properties, including gravimetric soil water content, pH, electrical conductivity(EC), and soil C:N ratio, were also strongly influenced by adjacent vegetation, which suggested that fertile islands may be beneficial for plant recovery in this region.

The negative effects of soil microorganisms on plant growth only extend to the first weeks

Soil biotic communities can strongly impact plant performance.In this paper,we ask the question:how longlasting the effect of the soil microbial community on plant growth is.We examined the plant growth rates at three stages:early,mid and late growth.We performed two growth experiments with Jacobaea vulgaris,which lasted 49 and 63 days in sterilized soil or live soil.In a third experiment,we examined the effect of the timing of soil inoculation prior to planting on the relative growth rate of J.vulgaris with four different timing treatments.In all experiments,differences in biomass of plants grown in sterilized soil and live soil increased throughout the experiment.Also,the relative growth rate of plants in the sterilized soil was only significantly higher than that of plants in the live soil in the first two to three weeks.In the third experiment,plant biomass decreased with increasing time between inoculation and planting.Overall,our results showed that plants of J.vulgaris grew less well in live soil than in sterilized soil.The negative effects of soil inoculation on plant mass appeared to extend over the whole growth period but arise from the negative effects on relative growth rates that occurred in the first weeks.