Soil Microbial Respiration Research Articles

Dominant plant species alter stoichiometric imbalances between soil microbes and their resources in an alpine grassland: Implications for soil microbial respiration

Soil microbes are subject to stoichiometric imbalances, which are the dissimilarities in elemental stoichiometry between microbial biomass and resources. Shifts in dominant plant species co-occur with unparallel changes in the stoichiometry of soil microbial biomass and resources, leading to stoichiometric imbalances. However, how soil microbes deal with stoichiometric imbalances induced by changes in dominant plant species, and what the implications are for soil carbon cycling, remain unknown. Here, we compared the stoichiometric imbalances of five plant patch types with the dominant plant community (Kobresia pygmaea) in a Tibetan alpine grassland to examine how soil microbes respond physiologically to stoichiometric imbalances, thereby affecting soil microbial respiration (SMR). We found that C:N and C:P imbalances varied between plant patches and differed significantly from those in the soil of K. pygmaea. We also found that the regulation of extracellular enzyme production, SMR, potential microbial carbon use efficiency (CUE), net N mineralization, and net ammonification were essential mechanisms for soil microbes to deal with C:N imbalances. Simultaneously, soil microbes dealt with fluctuating C:P imbalances by regulating their net P mineralization and CUE. Further, structural equation modeling revealed that stoichiometric imbalances induced by changes in dominant plant species could indirectly affect SMR by regulating extracellular enzyme stoichiometry and net nutrient mineralization. These results highlight the importance of the stoichiometry of soil microbe/resource interactions in regulating metabolic activities and modifying terrestrial carbon flows in shifting plant communities.

Towards the effects of moss-dominated biocrusts on surface soil aeration in drylands: Air permeability analysis and modeling

Soil aeration is an important factor influencing soil biological and biochemical processes because it directly affects soil microbial activity and respiration. As an important living skin of the soil, biocrusts strongly impact various soil properties and play a vital role in maintaining surface soil structure and multifunctionality. Although there are several studies concerning the effects of biocrusts on soil respiration processes, it is still not well understood how biocrusts affect air permeability (Ka) and soil aeration in drylands. In a semiarid climate region of the northern Chinese Loess Plateau, the Ka and air-filled porosity (εa) of moss-dominated biocrusts established on aeolian sand and loess soil were measured as a function of soil water content under laboratory and in situ conditions and compared to measurements of bare soils. The relative air permeability (Kra) of biocrusts and bare soils was further analyzed and estimated with commonly applied Kra models that are based on the soil water retention curve (SWRC), and the performance of these models was specifically assessed for biocrusts. The in situ measurements yielded a 51.8% and 76.7% higher Ka for the biocrust-colonized aeolian sand and loess soil, respectively, when compared to the bare soils. Correspondingly, in comparison to the bare soils, the εa of the biocrusts also increased by 38.0% for the aeolian sand and by 52.4% for the loess soil. The laboratory measurements showed an 8.5%–9.3% increase of Ka for the biocrust-colonized soils from wet to dry conditions when compared to their bare counterparts, which was mainly attributed to their higher fine particle and organic matter contents as well as to the moss rhizoids. Moreover, a positive linear relationship (R2 > 0.43) was found between the log Ka and log εa for both biocrusts and bare soils. Additionally, the biocrusts exhibited higher water content at almost all matric potentials in comparison to the bare soils. The Kra of biocrusts was 22.0% higher for aeolian sand and 42.1% higher for loess soil when compared to the bare soils. The van Genuchten-Burdine and Brooks and Corey-Burdine models performed best with regard to the estimation of Kra (RMSE ≤ 0.100, bias ≤ 0.018). In general, biocrusts may greatly increase surface soil aeration due to their higher Ka and εa, and the soil aeration status of biocrusts can be indirectly assessed through their effective degree of soil water saturation. Our findings suggest that biocrusts should be carefully considered in further studies of soil aeration related to biological processes and gas and vapor transport in dryland ecosystems.

Temperature fluctuation promotes the thermal adaptation of soil microbial respiration.

The magnitude of the feedback between soil microbial respiration and increased mean temperature may decrease (a process called thermal adaptation) or increase over time, and accurately representing this feedback in models improves predictions of soil carbon loss rates. However, climate change entails changes not only in mean temperature but also in temperature fluctuation, and how this fluctuation regulates the thermal response of microbial respiration has never been systematically evaluated. By analysing subtropical forest soils from a 2,000 km transect across China, we showed that although a positive relationship between soil microbial biomass-specific respiration and temperature was observed under increased constant incubation temperature, an increasing temperature fluctuation had a stronger negative effect. Our results further indicated that changes in bacterial community composition and reduced activities of carbon degradation enzymes promoted the effect of temperature fluctuation. This adaptive response of soil microbial respiration suggests that climate warming may have a lesser exacerbating effect on atmospheric CO2 concentrations than predicted.

Microbial respiration gives early indication of soil health improvement following cover crops

Farmer participatory research in soil health is important to evaluating soil conservation practices like cover crops on working farms. The Soil Health Partnership (SHP) was a large farmer-led network that conducted a wide-scale assessment of soil health indicators, scores, and crop yields from on-farm research with consistent experimental methods across site-years. The focus of this study was to determine the effect of one to four years of cover crops on 12 soil health indicators, three soil health assessment composite scores, and yields of two crops using data collected from only 35 SHP sites from 2015 to 2019 (total of 45 site-years). Sites applied either single or mixed species winter cover crops in corn (<i>Zea mays</i> L.) and soybean (<i>Glycine max</i> L.) rotations. The strip-level soil health measurements were analyzed using a mixed model analysis of covariance with repeated measures. Observations taken prior to cover crop implementation were used as the covariate. Soil microbial respiration (carbon [C] mineralization) and the composite Comprehensive Assessment of Soil Health score responded to cover crops. Their initial observation values did not influence the impact of cover crops on soil health indicators or scores. These results demonstrate that regardless of initial soil health values, soil respiration might be a helpful indicator to monitor for short-term soil health changes within one to four years following the adoption of conservation practices across the midwestern United States.

Assessment of microbial respiration in sugarcane soil with different nitrogen's dosage

Assessment of microbial respiration in sugarcane soil with different nitrogen's dosage

Soil Biophilic Elements (С, N, Р) and Microbial Respiration Activity in Forest Parks of Moscow and Rural Forests

In six forest parks of Moscow and four rural forests (5 plots each, n = 50), soil physical, chemical and microbial properties of the upper 10 cm layer were assessed in combination to vegetation properties. The content of carbon (C), nitrogen (N), and phosphorus (P) in soil and microbial biomass was determined. It was revealed that soil density, pH value, content of N–\({\text{NO}}_{3}^{ - },\) Ca and heavy metals (Pb, Cu, Ni, Zn) increase in forest parks compared to rural forests. In the soil of the forest parks, a decrease in the content of microbial biomass C (Cmic), its basal respiration (BR), and microbial C- and N-availability (Cmic/C, Nmic/N, BR/C) was noted. The changes of soil microbial properties are mainly driven by the abundance of leaf litter and the content of available soil C (13–35% of the explained variance). The microbial response to the soil enrichment by low molecular weight organic substrates (carbohydrates, carboxylic and phenolic acids, amino acids, amino sugars) in forest parks and rural forests did not differ significantly. In the soils of forest parks, no changes in microbial mineralization and immobilization of P (Pmic, Pmic/P) were found as well. The impact of urbanization on the forest ecosystems has led mainly to a decrease in the intensity of processes associated with soil C and N cycles. Apparently, such changes are caused by the recreational activity and the management practice of green spaces in the city, which leads, in particular, to a decrease in the amount of forest litter in parks compared to rural forests.

黄河流域生态功能区植被碳汇估算及其气候影响要素

PDF HTML阅读 XML下载 导出引用 引用提醒 黄河流域生态功能区植被碳汇估算及其气候影响要素 DOI: 10.5846/stxb202203110591 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 水沙科学与水利水电工程国家重点实验室(清华大学)2021年对外开放基金(sklhse-2021-A-06);辽宁省兴辽英才项目资助;国家自然科学基金项目(52079060) Estimation of vegetation carbon sink in the Yellow River Basin ecological function area and analysis of its main meteorological elements Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:基于改进的CASA模型和土壤呼吸模型,综合遥感数据、气象数据、植被数据等多源数据类型,以黄河流域为研究对象,估算生态功能区植被碳源/汇,探讨其时空变化及主要气候影响要素。结果显示:(1)黄河流域植被净初级生产力(NPP)在2000-2020年整体呈波动上升趋势,多年平均NPP值为317.18 gC m-2 a-1;林地＞耕地＞沼泽＞草地,水体、戈壁、风蚀劣地和裸沙地的NPP总体处于较低值。空间尺度上,黄河流域NPP呈现出南高北低的分布特点,高值区集中在黄土高原农业与草原生态区与汾渭盆地农业生态区交界处,空间差异显著。(2)土壤微生物呼吸量极大值出现2018年,为15.82 gC m-2 a-1,最小值出现在2004年为14.34 gC m-2 a-1;空间上呈现从东南往西北、从东往西依次递减的空间分布格局。(3)黄河流域总体呈碳汇属性(碳汇区域超过60%),年均固碳量约为111.02 MgC/a,年均排碳量为-9.96 MgC/a,年均净碳汇总量约为111.41 MgC/a。(4)黄河流域植被碳汇的形成与降水和太阳辐射的相关性最大,气温的影响面积仅占12.44%;当气温为30℃,降水150 mm,太阳辐射550 MJ/m2时,植被固碳能力效果最强。研究结果为区域全面准确地评估陆地生态系统碳源/汇,实现黄河流域高质量发展,达到碳中和目标提供参考依据。 Abstract:Based on the improved CASA (Carnegie-Ames-Stanford Approach) model and soil respiration model, this paper integrates multi-source data, such as remote sensing data, meteorological data and vegetation data, to estimate vegetation carbon sources/sinks in ecological function areas, and explore their spatio-temporal variations and main climate influencing elements in the Yellow River Basin. The results show that (1) the overall Net Primary Productivity (NPP) of vegetation in the Yellow River Basin presented a fluctuating upward trend from 2000 to 2020, with a multi-year average NPP value of 317.18 gC m-2 a-1. The NPP of various vegetation types showed that: forest land>cropland>swamp>grassland, and water bodies, Gobi, wind eroded poor land and bare sand land were at lower values overall. On the spatial scale, the NPP in the Yellow River Basin shows the distribution characteristics of high in the south and low in the north, and the high value areas are concentrated at the junction of the Loess Plateau agricultural and grassland ecological zone and the Fenwei Basin agroecological zone, with significant spatial differences. (2) The maximum value of soil microbial respiration appeared in 2018 at 15.82 gC m-2 a-1, and the minimum value appeared in 2004 at 14.34 gC m-2 a-1; spatially it showed a spatial distribution pattern decreasing from southeast to northwest and from east to west. (3) The Yellow River Basin has a carbon sink attribute in general (the carbon sink area exceeds 60%) The average annual carbon sequestration is about 111.02 MgC/a, the average annual carbon emission is -9.96 MgC/a, and the total annual net carbon sink is about 111.41 MgC/a. (4) The formation of vegetation carbon sink in the Yellow River Basin is mostly correlated with precipitation and solar radiation, and the influence area of air temperature only accounts for 12.44%; the effect of vegetation carbon sequestration capacity is the strongest when the temperature is 30℃, precipitation is 150 mm, and solar radiation is 550 MJ/m2. The results of the study provide a reference basis for a comprehensive and accurate regional assessment of carbon sources/sinks in terrestrial ecosystems to achieve high-quality development in the Yellow River Basin and meet the carbon neutrality target. 参考文献 相似文献 引证文献

Trade-off between microbial carbon use efficiency and specific nutrient-acquiring extracellular enzyme activities under reduced oxygen

• Reduced oxygen increased microbial metabolic quotient (qCO2).• Reduced oxygen enhanced microbial specific C-, N- and P-acquiring enzyme activity.• Reduced oxygen increased microbial C relative to N and P limitation. • Reduced oxygen increased microbial N relative to P limitation. • Specific enzyme activity was positively related to qCO2 under reduced oxygen.Mangroves are one of the most ecologically sensitive ecosystems to global climate change, which have cascading impacts on soil carbon (C), nitrogen (N) and phosphorus (P) cycling. Moreover, mangroves are experiencing increasing N and P loadings and reduced oxygen availability due to intensified climate change and human activities. However, both direct and interactive effects of these perturbations on microbially mediated soil C, N and P cycling are poorly understood. Here, we simultaneously investigated the effects of N and P loadings and reduced oxygen on microbial biomass, microbial respiration, and extracellular enzyme activities (EEAs) in mangrove soils. We calculated the microbial metabolic quotient (qCO2), which is regarded as a useful inverse metric of microbial C use efficiency (CUE). Our results show that reduced oxygen significantly increases both qCO2 and microbial specific EEAs (enzyme activity per unit of microbial biomass) for C-, N- and P-acquisition regardless of N or P loadings. Furthermore, we found that qCO2 positively correlated with microbial specific EEAs under reduced oxygen, whereas no clear relationship was detected under ambient oxygen. These results suggest that reduced oxygen increases microbial specific EEAs at the expense of increasing microbial respiration per unit biomass, indicating higher energy cost per unit enzyme production.

Temporal Stability of Soil Microbial Properties in Responses to Long-Term Application of Compost Obtained from Tannery Sludge

Successive applications of compost obtained from tannery sludge affected the soil microbial biomass and activity. However, the effect of this practice on the temporal stability of soil microbial properties is not known. This study evaluated the temporal stability of microbial biomass, respiration, and enzymes activities in soil with successive applications of compost obtained from tannery sludge. Soil samples (0–10 cm depth) were collected from sites with successive application of compost at the lowest (2.5 ton/ha) and highest (20 ton/ha) rates, including the control (0 ton/ha). Soil microbial biomass carbon (MBC) and nitrogen (MBN), respiration, dehydrogenase, and urease activities were evaluated at 0, 30-, 60-, 90-, and 150-days post-application. The soil microbial properties varied as per treatments and sampling time. The principal response curve showed higher variation of soil microbial properties in the treatment having highest rate of compost. This analysis showed dehydrogenase, urease, and MBC as the most responsive parameters. The temporal stability of soil microbial parameters showed highest values at the lowest rate of compost. This study showed that the successive application of compost contributed to a decrease in variation and increase in temporal stability of soil microbial properties at the lowest rate.

Monitoring TPH biodegradation in soil around Ray oil refinery by natural attenuation, biostimulation and bioaugmentation treatments

In this study, total petroleum hydrocarbons (TPHs) decontaminating mechanisms for soils around the Rey refinery complex (South of Tehran, Iran) was investigated. Natural attenuation, biostimulation and bioaugmentation (separately and in combination) methods were evaluated TPHs and soil microbial respiration in 210 days, using laboratory treatments The modified methods were applied through 13 different treatments, including improving the environmental conditions for native bacteria (natural attenuation for treatments 1-8), adding non-native bacterial complex (bioaugmentation for treatment 9) and intensifying and stimulating growth while adding non-native bacterial complex (biostimulation-bioaugmentation for treatments 10-13). Although, overall of the treatments, a significant decreasing TPHs concentration were observed over the time, biostimulation-bioaugmentation treatments had the highest amount of TPHs decomposition, the highest rate of bio-respiration, the lowest half-life times (t1/2), and the highest remediation efficiency and biodegradation constants rate. Among natural attenuation treatments, modifiers with manure and sawdust had the greatest effect on reducing the TPHs concentration and the highest rate of bio-respiration. The first-order kinetic model was fitted to the data related to biodegradation in a satisfactory manner. The results showed that there was a strong and positive linear correlation between decreasing TPHs concentration and microbial respiration in all modifiers. Although for the bacterial treatments and at the early stages of inoculation, the rate of total respiration was low, but as the time passed and with adaptation of the effective inoculated bacteria to contaminated soil, the respiration rate gradually was increased. Due to its low cost and low environmental risk, the proposed bioremediation technique for oil contaminated soil can be recommended to the region.

Response of soil C-, N-, and P- acquisition enzymes to moisture pulses in desert grassland to shrubland state transition

Grassland-shrubland state transition causes profound effects on soil nutrients and microorganisms, yet little is known about how these soil characteristics are influenced by rainfall and litter changes during transition. Here, we examined water (high or low moisture pulse) and litter (grass or shrub) effects on these soil characteristics in grassland-shrubland mosaics consisting of desert grassland (DG), grassland edge (GE), shrubland edge (SE), and shrubland (SL) sites. The results showed that the transition of DG-GE-SE-SL significantly reduced soil moisture, total carbon (C), total nitrogen (N), total phosphorus (P), microbial biomass carbon, and microbial biomass nitrogen, revealing evident soil degradation during this transition. After applying water and litter, soil microbial respiration (SMR) and the activities of all enzymes were promoted to varying degrees among the sites. Specifically, SMR was promoted under a low moisture pulse but suppressed under a high moisture pulse along the transition from DG to SL. Two C-acquisition enzymes, cellobiohydrolase and β-1,4-glucosidase, became increasingly active from DG to SL. Another C-acquisition enzyme of β-1,4-xylosidase and an N-acquisition enzyme of leucine aminopeptidase showed the strongest preferences for low moisture pulses in SL. These results indicated that shrub encroachment retained certain microbes with an advanced ability to acquire to C and N from dry and infertile soil in SL. Although a P-acquisition enzyme of alkaline phosphatase showed a decreasing trend along the transition from DG to SL, similar like those C- and N- acquisition enzymes, it was not sensitive to varying moisture levels, suggesting that alkaline phosphatase was affected by other soil physicochemical properties rather than soil moisture. The joint analysis of soil extracellular enzymes and nutrients indicated that microbial biomass carbon played a more important role than other soil characteristics in determining soil extracellular enzyme activities along the transition from DG to SL. Future research on dissecting soil microbial communities is warranted to better understand the microbiological mechanisms behind these phenomena in the shrub encroachment process.

Apparent thermal acclimation of soil heterotrophic respiration mainly mediated by substrate availability.

Multiple lines of existing evidence suggest that increasing CO2 emission from soils in response to rising temperature could accelerate global warming. However, in experimental studies, the initial positive response of soil heterotrophic respiration (RH ) to warming often weakens over time (referred to apparent thermal acclimation). If the decreased RH is driven by thermal adaptation of soil microbial community, the potential for soil carbon (C) losses would be reduced substantially. In the meanwhile, the response could equally be caused by substrate depletion, and would then reflect the gradual loss of soil C. To address uncertainties regarding the causes of apparent thermal acclimation, we carried out sterilization and inoculation experiments using the soil samples from an alpine meadow with 6 years of warming and nitrogen (N) addition. We demonstrate that substrate depletion, rather than microbial adaptation, determined the response of RH to long-term warming. Furthermore, N addition appeared to alleviate the apparent acclimation of RH to warming. Our study provides strong empirical support for substrate availability being the cause of the apparent acclimation of soil microbial respiration to temperature. Thus, these mechanistic insights could facilitate efforts of biogeochemical modeling to accurately project soil C stocks in the future climate.

Seasonal dynamics of soil and microbial respiration in the banj oak and chir pine forest of the central Himalaya, India

This research investigates seasonal changes of root respiration (Rroot), total soil respiration (Rtotal) and microbial respiration (Rmicrobial) in three central Himalayan forest types: banj oak (BO), chir pine (CP) and banj oak regenerated (BOR). The trenching method is used to separate Rroot from Rtotal. Soil physicochemical and biological properties were compared among the forest type and seasons using one-way ANOVA. Results indicated the significant (p < 0.05) influence of forest type and season on Rtotal, Rroot and Rmicrobial. BO forest had significantly (p < 0.05) higher Rtotal than the CP forest. This was attributed to lower bulk density (BD), pH and high soil moisture, soil organic carbon (SOC), total nitrogen (TN) and microbial biomass carbon (MBC) in the BO forest. Higher soil moisture, SOC, TN and MBC in BO reflects higher microbial metabolic activity than the CP, with low soil moisture and nutrient content. The Rroot/Rtotal ratio ranged from 35 to 62 % for BO, 12 to 58 % for CP and 14 to 45 % for BOR, indicating that Rroot was an important contributor to Rtotal. The contribution of Rroot was at a maximum in the rainy season (53 %) and a minimum in the winter season (11 %), indicating the synergistic effect of optimum soil micro-climatic conditions and soil nutrient content to Rroot. In an exponential regression analysis, soil temperature better explained Rtotal (r2 = 0.81–0.82, p < 0.001). In comparison to Rmicrobial (r2 = 0.58–0.85, p < 0.001), Rroot is better explained by soil moisture (r2 = 0.59–0.88, p < 0.001) in a linear regression model. Present findings suggest that the positive effect of temperature, moisture and litter nitrogen on Rtotal are majorly regulated by forest types, which potentially increases the understanding of climate change and nutrient dynamic processes on a global scale.

Recent Photosynthates Are the Primary Carbon Source for Soil Microbial Respiration in Subtropical Forests

AbstractTropical and subtropical forests represent the largest terrestrial carbon pool. Elucidating the carbon sources for soil microbial respiration (Rm) in tropical and subtropical forests is of fundamental importance to the global carbon cycle in a warming world. Based on hourly measurements, we quantified Rm of in situ forest soil and soil cores from a subtropical forest. We found recent photosynthates, not soil organic carbon (SOC), contributed 88% ± 12% of the carbon source fueling Rm. The control of recent photosynthates on Rm is also supported by the close relationship between Rm and photosynthetically active radiation as well as literature data synthesis results. These results challenge conventional models based on the tenet that Rm is mainly regulated by soil temperature in all forest ecosystems. The results imply that the widely observed warming‐induced Rm increases are largely explained by the enhanced input of recent photosynthates in tropical forests, not SOC consumption.

Asynchronous responses of microbial CAZymes genes and the net CO2 exchange in alpine peatland following 5 years of continuous extreme drought events

Peatlands act as an important sink of carbon dioxide (CO2). Yet, they are highly sensitive to climate change, especially to extreme drought. The changes in the net ecosystem CO2 exchange (NEE) under extreme drought events, and the driving function of microbial enzymatic genes involved in soil organic matter (SOM) decomposition, are still unclear. Herein we investigated the effects of extreme drought events in different periods of plant growth season at Zoige peatland on NEE and microbial enzymatic genes of SOM decomposition after 5 years. The results showed that the NEE of peatland decreased significantly by 48% and 26% on average (n = 12, P < 0.05) under the early and midterm extreme drought, respectively. The microbial enzymatic genes abundance of SOM decomposition showed the same decreasing trend under early and midterm extreme drought, but an increasing trend under late extreme drought. The microbial community that contributes to these degradation genes mainly derives from Proteobacteria and Actinobacteria. NEE was mainly affected by soil hydrothermal factors and gross primary productivity but weakly correlated with SOM enzymatic decomposition genes. Soil microbial respiration showed a positive correlation with microbial enzymatic genes involved in the decomposition of labile carbon (n = 18, P < 0.05). This study provided new insights into the responses of the microbial decomposition potential of SOM and ecosystem CO2 sink function to extreme drought events in the alpine peatland.

Cleaner production technologies for the amelioration of soil health, biomass and secondary metabolites in Ocimum basilicum L. under Indian Western Himalaya.

Ocimum basilicumL. and its derived products are primarily consumed by humans; hence, agrochemical use seems inappropriate for its cultivation. However, farmers are accustomed to using rampant inorganic fertilizers to augment crop productivity, which has unintendedly engendered severe environmental perturbations. Concomitantly, farmers will soon have to confront the challenges of growing crops under suboptimal conditions driven by global climate change. Consequently, to develop a clean, sustainable, and resilient production technology, field experiments spanning over two years (2020 and 2021) were conducted, comprising three biostimulants,viz., vermicompost (0, 4, and 8 Mg ha-1), biofertilizer (uninoculated and inoculated), and liquid seaweed extract (without and at 7ml L-1) in the Indian western Himalaya for the first time. Soil health indicators, leaf photosynthetic pigments, gaseous exchange, mineral contents, essential oil (EO) quantity, and composition were evaluated. Soil microbial respiration (SMR), microbial biomass carbon (MBC), organic carbon (OC), dehydrogenase (DHA), alkaline phosphatase (ALP), and β-glucosidase activities were increased by 36.23, 83.98, 30.61, 42.69, 34.00, and 40.57%, respectively, when compared with the initial soil status. The net photosynthetic rate (Pn) was significantly increased with the highest (8 Mg ha-1) and moderate (4 Mg ha-1) vermicompost dosages by 13.96% and 4.56%, respectively, as compared with the unfertilized control (0 Mg ha-1). Likewise, the biofertilizer and seaweed extract also enhanced Pn by 15.09% and 10.09%, respectively. The crop's key EO constituents,viz., methyl chavicol and linalool, were significantly improved with the highest and moderate vermicompost rates of 2.71, 9.85%, and 1.18, 5.03%, respectively. Similarly, biofertilization and seaweed application also boosted methyl chavicol and linalool by 3.29, 8.67%, and 1.93, 3.66%, respectively. In both years, significantly higher herbage (8.86 and 11.25 Mg ha-1) and EO yield (113.78 and 154.87kg ha-1) were recorded with a congregate treatment of the highest vermicompost dose, biofertilizer, and liquid seaweed extract. In conclusion, the integrated use of biostimulants having complementary properties can sustainably maximize the quantity and quality ofO. basilicumand concomitantly ameliorate soil health. This study can inspire scientific communities and industries to develop second-generation biostimulant products, delivering better sustainability and resilience for a renaissance in agriculture.

Tree species is more effective than season dynamics on topsoil function andCO2emissions in the temperate forests

AbstractSoil respiration is one of the most important operations controlling carbon (C) erosion from territorial ecosystems and a useful index of whole underground allocation of C and stand efficiency. However, how tree species effects root (i.e., autotrophic respiration) and soil microbial respiration (i.e., heterotrophic respiration), based on precise experiential schemes, are still restricted, even though crucial to guide the selection of species for reforestation and C management purposes. This research was done to study how tree species effect soil characteristics and function at stand level and which are the main drivers of soil CO2emission in mixed temperate forests in northern Iran (Mazandaran province). Four most common tree species at the experimental site (Parrotia persica,Ulmus minor,Quercus castaneifolia, andPopulus caspica) that surrounded by same species, were selected. Around each selected tree, four replicates of soil and litter samples were taken from (30 × 30 × 15 cm) and mixed to characterize soil physicochemical characteristics (i.e., bulk density, texture, water content, pH, electrical conductivity, N, organic carbon, and available P, K, Mg, and Ca), basal respiration and substrate (i.e., D‐manitol, D‐glucose, L‐asparagine, L‐arginine, gluconic acid, quinic acid, succinic acid, malonic acid, D‐glucosamine, L‐glutamine) induced respiration. In the litter characteristics, total N, C (OC), and C/N ratio were measured. Our results confirmed that soil chemical properties are more sensitive to species composition than soil physical ones. Moreover, individual tree species in mixed deciduous forests strongly influence induced microbial respiration, independently of the used substrates. On the contrary, season was the major factor explaining variations of basal respiration.

Functional Diversity and CO2 Emission Characteristics of Soil Bacteria during the Succession of Halophyte Vegetation in the Yellow River Delta.

Carbon dioxide (CO2) is the most important greenhouse gas in the atmosphere, which is mainly derived from microbial respiration in soil. Soil bacteria are an important part of the soil ecosystem and play an important role in the process of plant growth, mineralization, and decomposition of organic matter. In this paper, we discuss a laboratory incubation experiment that we conducted to investigate the CO2 emissions and the underlying bacterial communities under the natural succession of halophyte vegetation in the Yellow River Delta by using high-throughput sequencing technology and PICRUSt functional prediction. The results showed that the bacterial abundance and diversity increased significantly along with the succession of halophyte vegetation. Metabolic function is the dominant function of soil bacteria in the study area. With the succession of halophyte vegetation, the rate of CO2 emissions gradually increased, and were significantly higher in soil covered with vegetation than that of the bare land without vegetation coverage. These results helped to better understand the relationships of soil bacterial communities under the background of halophyte vegetation succession, which can help to make efficient strategies to mitigate CO2 emissions and enhance carbon sequestration.

Comparison of the Responses of Soil Enzymes, Microbial Respiration and Plant Growth Characteristics under the Application of Agricultural and Food Waste-Derived Biochars

The conversion of bio-wastes to useful products such as biochar provide a suitable option not only to minimize the mass of wastes, but also to use the biochar as soil amendment. In the present study, food waste biochar (FWB) and agricultural waste derived biochar (AB), either alone or in combination (FWB + AB), were tested for their effects on soil microbiological characteristics (soil enzymes, soil basal as well as substrate-induced respiration), plant growth and photosynthetic parameters. Four treatments were tested: control, FWB, AB and FWB + AB. The results indicated that the application of AB significantly enhanced the plant above ground and below ground fresh and dry biomass as compared to other amendments and control (+41 to +205% compared to control). The application of FWB enhanced the quantum yield of photosystem II (QY-max, +4% compared to control) and normalized difference vegetation index (NDVI, +13% compared to control). Moreover, the FWB application improved the soil dehydrogenase (DHA) activity (+24% compared to control). Furthermore, the soil basal respiration was found to be increased under AB application (+46% compared to control) and the substrate-induced respirations were relatively decreased, depicting negative effects of applied biochars on substrate-induced respirations. Thus, we concluded that the differential responses of observed crop and soil attributes might be related to the biochar specific effects on soil properties.

Responses of microbial community composition and respiration to soil moisture in eroded soil

Soil moisture (SM) is one of the most limited factors on the Loess Plateau, but its effects on the microbial community and respiration are still unclear. To investigate the effects of stepwise wetting and constant SM on the soil microbial community and respiration rates, eroded soil under afforestation on the Loess Plateau was examined. The soils were sampled and incubated with constant gravimetric SM of 5 %, 30 % and 45 % and wetting treatments with SM increasing from 5 % to 30 % (5–30 %), from 5 % to 30 % to 45 % (5–30–45 %) and from 30 % to 45 % (30–45 %). As shown in the results, bacterial richness and Shannon diversity were lower in the wetting treatments of 5–30 % and 5–30–45 % than those in 5 %, 30 % and 45 % SM constant treatments. Contrary, the values were similar in the 30 % SM constant and the 30–45 % SM wetting treatment, which were the highest among all the treatments. The dominant bacterial species converted from Actinobacteria to Alphaproteobacteria and Acidobacteria with SM increasing. No significant differences were observed in fungal Shannon diversity, richness and communities under varying conditions. Consequently, the wetting treatments influenced the bacteria more significantly than fungi. A greater Birch effect occurred with a two-step increase in SM (i.e., 5–30–45 %) than the one-step wetting treatment (i.e., 30–45 %), while a dampened Birch effect was observed with higher previous soil respiration. However, excessive moisture did not enhance or even inhibit microbial respiration. Our work indicated that even short-term changes in the antecedent SM can significantly affect bacterial communities and dynamic of carbon flux. The responses of microbe and respiration were not only dependent on the current SM but also related to the antecedent SM condition. This study benefits plant-soil-water relationship management during afforestation on the Loess Plateau of China.