Microbial Biomass Carbon Content Research Articles

Grazing Regulates Changes in Soil Microbial Communities in Plant-Soil Systems

Soil microorganisms promote material transformation and energy flow in the entire ecological environment and play a key role in the stability and development of grassland ecosystems. Studies on the impacts of grazing on the soil microbial community and the establishment of a reasonable grazing intensity are crucial to improve our knowledge of the mechanisms underlying grassland degradation and to accurately assess the influence of grazing management on grassland functions and the nutrient cycle. Based on the grassland grazing control experimental platform, we compared the structure and diversity characteristics of soil microbial communities under six grazing intensities (0.00, 0.23, 0.34, 0.46, 0.69, and 0.92 AU ha−1) (1 AU = 500 kg of adult cattle) on the Hulunbuir Leymus chinensis meadow steppe. The results showed that soil microbial biomass carbon (MBC) and nitrogen (MBN) decreased with increasing soil depth. The 0–10 cm soil layer of G0.34 had the highest MBC and MBN, and the G0.92 treatment had the lowest MBC and MBN. Heavy grazing significantly decreased the MBC and MBN contents in the soil surface layer. The soil bacterial diversity under light grazing treatment (0.23 AU ha−1) was higher than that under heavy grazing, and the fungal diversity under the no-grazing treatment was higher than that under the grazing treatment. Overgrazing reduced the bacterial species in the soil. The plant belowground biomass significantly (p = 0.039) influenced the bacterial community structure, and the soil pH (p = 0.032), total nitrogen (p = 0.011), and litter (p = 0.007) significantly influenced the fungal community. The effects of grazing on microbial communities were primarily driven by vegetation productivity, litter mass, and soil geophysical and chemical characteristics. This study deepened our understanding of the impacts of grazing practices on soil microbial communities on the meadow steppe, suggesting that moderate-disturbance grazing can promote the sustainable development of grassland vegetation-soil microorganisms.

Soil organic carbon pool distribution and stability with grazing and topography in a Mongolian grassland

Livestock grazing and topography have long been recognized as essential factors that control soil organic carbon (SOC) dynamics. However, the interplay effects of grazing and topography on SOC pool distribution and stability are not well understood, hindering the precise prediction of the organic carbon (OC) fate over the hillslope grassland. Here, we examine the relationship between grazing and topography on SOC pool distribution and stability in a Mongolian grassland. We determined a suite of OC metrics (e.g., particulate OC (POC), mineral-associated OC (MAOC), dissolved OC (DOC), and microbial biomass carbon (MBC) along a topographic gradient (e.g., upper slope, middle slope, and downslope) with grazing or not, and incubation was conducted to quantify OC stability. The results showed that POC and SOC content was 106–138% and 24–63% greater in the grazed than the ungrazed site at low topographic positions, respectively. Across the landscape, more variations in POC and SOC across the topographic gradient were observed at the grazed sites than at ungrazed sites. The MBC content of the downslope was greater in the grazing than in ungrazed sites. Furthermore, the humic-like substances in the grazing area were lower than those in the enclosed area and showed a significant and positive linear relationship with the aromaticity and humification of DOC. The aggregated boosted tree (ABT) analysis showed that the POC and MBC were the most important OC components to affect OC pool stability (accounting for 40.87%). The structural equation model (SEM) supported that the varies of POC regulated the downstream soil biochemical processes and changed SOC pool stability. Collectively, the results suggest the POC could be primarily responsible for the changes in SOC pools and stability in a hillslope grassland. These findings enhanced our understanding of the ecological mechanisms in SOC sequestration.

Effects of straw incorporation and straw-burning on aggregate stability and soil organic carbon in a clay soil of Bangladesh

The clay soil of Bangladesh is typically low in soil organic carbon (SOC) and generally has poor soil aggregate stability (measured as mean weight diameter, MWD). The addition of organic amendments in the field has the potential to increase soil organic matter (SOM) and MWD. However, the influence of organic amendments on aggregation in the clay soils of Bangladesh is largely unknown. A short-term (105 days) field study has been conducted to evaluate the effects of straw incorporation and straw-burning treatments on MWD and SOC in clay soil under eggplant (Solanum melongena L.). This study consisted of three treatments: (i) control (no amendments), (ii) rice straw (straw applied at 21 t ha−1), (iii) rice straw-burning (ash retained after burning at 7.4 t ha−1). Soil samples were collected after plant harvest, and then MWD, SOC, glomalin-related soil protein (GRSP), microbial biomass carbon (MBC), Fe-oxides, and available soil nutrients (e.g., N, P, K, S, Na, Ca, and Mg) were determined. Our results showed that MWD in straw addition treatment was on average 2 times higher, whereas SOC was 1.3 times higher compared to the control and straw-burning treatments, respectively (P < 0.05). Conversely, the straw-burning treatment reduced the MWD by 19% and the SOC by 20% compared to the control treatments (P < 0.05). Significant improvements in the available K, S, and Mg content of soil were found in the straw incorporation treatment (P < 0.05). We did not find any significant influence of the treatments on the MBC and GRSP content of the soil. Soil organic carbon had a significant correlation with MWD (R2 = 0.80**, P < 0.01), while GRSP and Fe-oxides did not show any relationship with MWD (P > 0.05). Our study demonstrates that the incorporation of rice straw has the potential to increase soil aggregation and SOC stock, at least for the short term in the clay soils of Bangladesh.

Invasive Wetland Weeds Derived Biochar Properties Affecting Soil Carbon Dynamics of South Indian Tropical Ultisol.

This study aimed to: (i) investigate the agronomic properties of biochars derived from selected invasive wetland weeds and (ii) examine the effect of biochar on soil organic carbon (SOC) dynamics and stability of tropical Ultisol soil. The biochars were analyzed for proximate properties, surface characteristics, elemental composition, functional groups, and thermal and carbon stability. Plant growth studies supplemented with biochar under greenhouse conditions for 1 year were conducted. The SOC, its fractions, and its dynamics were studied. The biochar incorporation significantly increased the SOC and its stable fractions like mineral Organic Carbon (MOC), fine-particulate organic carbon (fPOC), and Non-labile Carbon (NLC) by 24.54-7.82, 5.79-2.0, and 9.50-2.16 g kg-1 than control. The labile carbon fractions like Dissolved Organic Carbon (DOC), and coarse-Particulate Organic Carbon (cPOC) showed a substantial reduction by 0.72-0.26 and 2.92-1.29 g kg-1 respectively. However, the easily oxidizable carbon (EOC) and microbial biomass carbon (MBC) content increased by 2.10-4.87 g kg-1 and 28.33-158.55 mg kg-1 respectively. The addition of biochars resulted in the stabilization of soil aggregates. Likewise, substantial CO2 emission reduction (75.24-46.60%) has been achieved during the trials. The carbon pool management index (CPMI) values recorded a substantial increase of 40-7.2% between the trials. The findings imply that the inherent nature of weed biomasses determines the characteristics of the resulting biochar, and their application significantly influenced the carbon dynamics of the tropical Ultisol soil.

Warming changes the composition and diversity of fungal communities in permafrost

PurposeIt is the data support and theoretical basis for the response mechanism of soil fungi to climate warming in permafrost areas in the Greater Xing’an Mountains.MethodsWe collected permafrost from the Greater Xing’an Mountains for indoor simulation experiments and took the natural permafrost as the control (CK) and the test groups of 0 °C (T1), 2 °C (T2), and 4 °C (T3) were set. Illumina MiSeq high-throughput sequencing technology was used to understand the changes in characteristics of fungal communities, and the correlations were analyzed combined with the soil physicochemical properties.ResultsCompared with CK, the value of pH and the content of available potassium (AK) in the three warming treatment groups were significantly lower (P < 0.05), and the microbial biomass carbon (MBC) content was significantly higher (P < 0.05). The content of total nitrogen (TN) and available nitrogen (AN) in the T1 and T3 groups was significantly lower than that in the CK group (P < 0.05). A total of 11 phyla, 39 classes, 89 orders, 187 families, 361 genera, and 522 species were obtained through fungal sequencing and divided into 1463 amplicon sequence variants (ASVs). Ascomycota and Dimorphospora were the dominant phylum and genus, respectively, and there were differences in the response of relative abundance of various groups at the phylum and genus levels to warming. Warming significantly decreased the Sobs and ACE indexes of the treatment groups (P < 0.05), and the Shannon and Shannoneven indexes also showed a downward trend. Moreover, warming significantly changed the fungal beta diversity (P < 0.01), while the value of pH and the content of TN, MBC, and AK could significantly affect the community structure (P < 0.05), and the correlation between fungi at different phyla levels and soil physicochemical properties was different.ConclusionsThese results can provide a reference for further study on the changes in composition and structure of fungal communities and the influence factor in permafrost in the Greater Xing’an Mountains under the background of warming.

Long-Term Organic Amendments Combined with Nitrogen Fertilization Regulates Soil Organic Carbon Sequestration in Calcareous Soil

Organic amendments have been widely confirmed to support soil health and agricultural sustainability. However, the effects and mechanisms of long-term organic amendments combined with chemical fertilizers on soil organic carbon (SOC) sequestration and soil macroaggregate formation are still unclear. Therefore, this study aimed to explore the interaction between soil carbon sequestration and soil agglomeration after 12 years of fertilization. Seven treatments within a field experiment were selected to conduct the research, including nitrogen (N) application by farmers, optimized N management, biochar and/or straw, manure, compost or biogas residue plus optimized N management. The results showed that the addition of organic materials significantly enhanced the SOC by 29.6–119.8% and 10.3–36.3% in 0–15 and 15–30 cm soil layers compared to N application by farmers, respectively. Meanwhile, the soil humus carbon pools in the 0–15 cm soil layer were increased by 14.7–205.2%, particularly humin carbon (HUC), which could be considered as a useful indicator of the soil carbon sequestration process. Among the organic materials, the addition of biochar was the most effective strategy due to its high aromatic carbon content that resisted biodegradation. The addition of organic materials also improved the soil labile carbon fractions, and the contents of microbial biomass carbon (MBC), dissolved organic carbon (DOC), particulate organic carbon (POC) and KMnO4-oxidizable carbon (ROC) were enhanced by 120.5%, 92.3%, 217.2% and 85.5% on average, respectively, and the amount of exchangeable Ca2+ and Mg2+ cations and Fe and Al oxides in the soil increased significantly whilst the Na+ content declined in the 0–15 cm soil layer. These indicators showed a significant correlation with the mean weight diameter (MWD). Our results revealed that the addition of organic materials could be an effective management practice to promote soil carbon sequestration and soil macroaggregate formation in calcareous soil.

Effects of Leymus Chinensis (Trin.) Tzvelev Grassland Litter Return on Soil Microbial Biomass Carbon of the Songnen Sandy Land in China

Effects of litter return of Leymus chinensis grassland on soil microbial biomass carbon of the Songnen sandy land were investigated. Characteristics of soil microbial biomass carbon (SMBC) from subhumid area of L. chinensis grassland ecosystem at different content of litter returns (0, 200 and 400 g/m2) and soil depths (0-10, 10-20, 20-30 and 30-40 cm) were evaluated. Results showed that the content of SMBC increased with the increase in litter return at the same soil depth. The content was highest (426.17 mg/kg) at 400 g/m2 litter return, which was 1.61 and 1.50 times higher than at 0 and 200 g/m2, respectively at the depth of 0-10 cm, and decreased sharply at 10-40 cm. These results showed that increasing the amount of litter return and suitable management measures can effectively enhance the carbon content of soil microbial biomass and improve soil microbial activity and fertility to ensure the balance of grassland ecosystem. Bangladesh J. Bot. 51(4): 907-912, 2022 (December) Special

青海云杉林凋落物分解早期微生物生物量时空动态变化

PDF HTML阅读 XML下载 导出引用 引用提醒 青海云杉林凋落物分解早期微生物生物量时空动态变化 DOI: 10.5846/stxb202203220711 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（31901130）；中国地质调查局地质调查项目（DD20208065） Temporal and spatial changes of microbial biomass in litter decomposition early process in Qinghai spruce (Picea crassifolia) forests 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:凋落物分解过程中的微生物生物量动态对于深入了解森林生态系统凋落物分解机理具有重要意义。为了解高寒山地森林典型树种凋落物分解过程中的微生物生物量动态特征，采用凋落物袋野外原位分解法，研究了海拔2850 m、2950 m、3050 m、3150 m和3250 m树冠中心（CC）与树冠边缘（CE）青海云杉（Picea crassifolia）叶凋落物分解过程中凋落物和土壤中的微生物生物量碳（MBC）、微生物生物量氮（MBN）和微生物生物量磷（MBP）时空动态变化。时间尺度上，不同海拔CC与CE凋落物中的MBC、MBN和MBP在生长季节初期上升，生长季节后期下降；但土壤中的MBC、MBN和MBP却在生长季节初期下降，生长季节后期上升。然而，3050 m海拔CE和3250 m海拔土壤中的MBP含量呈"先下降-后上升-再下降"的倒"N"型变化格局。空间尺度上，凋落物中的MBC和MBN含量高于土壤中的，但MBP出现相反情况；CE处的MBC、MBN和MBP含量均显著（P<0.05）高于CC；总体而言，MBC、MBN和MBP含量以中海拔显著最高（P<0.05），其次为低海拔，高海拔显著最低（P<0.05）。这些结果为清晰地认识高寒山地森林凋落物分解过程及机理，以及进一步理解陆地生态系统结构和功能奠定了基础。 Abstract:Microorganism plays an important role in litter decomposition, and the change of microbial biomass is of ecological significance in understanding the mechanism of litter decomposition in the forest ecosystem. In order to understand the dynamic characteristics of microbial biomass during litter decomposition process in the Qinghai spruce forest, Qilian Mountains, we collected leaf litter samples at the crown center (CC) and crown edge (CE) by decomposition litterbags in different times (the early growing season and the late growing season) and altitudes (i.e., 2850 m, 2950 m, 3050 m, 3150 m and 3250 m). The temporal and spatial changes of microbial biomass carbon (MBC), microbial biomass nitrogen (MBN) and microbial biomass phosphorus (MBP) in litter and soil were analyzed. Temporally, the MBC, MBN and MBP increased in the early growing season and decreased in the late growing season. On the contrary, the MBC, MBN and MBP in soil decreased in early growing season and increased in late growing season. However, the content of MBP in soil at CE of 3050 m altitude and 3250 m altitude showed an inverted "N" shaped pattern, that is, "decrease-rise-decrease". Spatially, the contents of MBC and MBN in litter were higher than those in soil at all plots, but MBP was the opposite. The contents of MBC, MBN and MBP at the CE were significantly (P<0.05) higher than those at the CC. In general, the contents of MBC, MBN and MBP were the highest at medium altitude (P<0.05), followed by low altitude, and then the lowest at high altitude (P<0.05). The results would lay foundation to understand the process and mechanism of litter decomposition in the alpine mountain forest ecosystem, and further understand the structure and function of the ecosystem. 参考文献 相似文献 引证文献

УГЛЕРОД МИКРОБНОЙ БИОМАССЫ В ПРОФИЛЕ МЕРЗЛОТНЫХ ПОЧВ ЮГА ВИТИМСКОГО ПЛОСКОГОРЬЯ

The cryogenic nature of soils undoubtedly affects the carbon content of microbial biomass. Global climate warming has led to a highly dissected relief in the form of heave mounds and thermokarst depressions, where the first reaction of landscapes to changing environmental conditions is the response of biota. The objects of our research are permafrost soils, brown soils and quasi-clay chernozems. The aim of the work was to determine the carbon of microbial biomass in soils with a dissected relief of the south of the Vitim plateau. We found a strong direct correlation between the carbon content of humus and carbon of microbial biomass in the studied soils. The correlation between the content of C-biomass and soil moisture in the forest cenosis is also noteworthy, here the relationship was (r=0.91) in the humus pocket and less close (r=0.69) in the host horizon. Comparing the carbon content of microbial biomass from frost-breaking cracks (humus pocket) in the soil from the same depths of the host horizon, it should be noted that the entry into the soil of significant amounts of organic matter with plant litter stimulates the soil microflora and even in the lower horizon there is a fairly high content of C-biomass. The indicators of microbial biomass and humus in frost cracks are higher. The obtained data characterize the direction and intensity of microbiological processes along the profile horizons. Such studies in agroecosystems are necessary to assess the influence of natural and anthropogenic factors on the soil microbial complex.

Effects of applying peanut shell and its biochar on the microbial activity and community structure of dryland red soil

Due to its soil formation process, dryland red soil has certain characteristics that are unfavorable for crop growth, including acidity, fineness, plate structures, and erosivity. The use of large amounts of fertilizer can decrease fertility and biodiversity and increase acidification, thereby seriously restricting the sustainable utilization of dryland red soil resources. Therefore, there is an urgent need for techniques that improve the crop quality and yield in dryland red soil areas. Returning crop waste to fields as fertilizer is a promising approach to sustainable agriculture. In the present study, the effects of applying peanut shell and an associated biochar product to dryland red soil were investigated, with a focus on soil microbial activity and community structure. Field experiments were conducted in Jiangxi Province, southern China, in 2020, in field plots of sweet potato crops. Seven treatments were set up according to the principle of equal carbon return to farmland: Control: (conventional fertilization); S1, S2, S3 (peanut shell application of 3000, 4500 and 6000 kg hm-2, respectively); and BC1, BC2, BC3 (peanut shell biochar application of 1000, 1500 and 2000 kg hm-2, respectively). The application of peanut shell and its biochar improved soil basal respiration, with the greatest increase relative to controls of 161.06% found in treatment S3 at the root harvest stage. The most obvious increase in microbial biomass carbon content due to biochar application was 206.50% in treatment BC2 at the root harvest stage. The application of peanut shell and its biochar increased the phospholipid fatty acid (PLFA) contents of total soil microorganisms and different microbial groups. The maximum increases in the PLFA contents of total soil microorganisms, gram-positive bacteria, and gram-negative bacteria occurred at the early root formation stage in treatment BC2, which were 112.16%, 102.52%, and 115.64%, respectively. Both peanut shell and biochar increased the PLFA contents of soil actinomycetes, arbuscular mycorrhizal fungi (AMF), and other fungi to certain extents. The soil actinomycetes PLFAs increased by 120.08% at the early root formation stage in BC2, while the AMF PLFAs increased by 79.44% at the seedling stage in S2. This study provides theoretical and practical guidance for the comprehensive utilization of peanut shell and the implementation of circular agriculture in dryland red soil regions. It also provides a scientific basis for improving the fertility of dryland red soil.

Changes in soil bacterial community along a gradient of permafrost degradation in Northeast China

Spatial fragmentation of permafrost alters soil hydrothermal conditions and physicochemical properties that control microbial activity responsible for the decomposition of organic matter. Due to climate warming, there is a need to identify changes in microbial community and diversity to predict altered soil function along permafrost degradation gradient. To determine the drivers of soil bacterial community at regional (across permafrost regions) and local scales (across habitats, within permafrost region), the method of “space instead of time” was adopted. The soil samples were collected from forest and wetland ecosystems in three types of west-east permafrost regions (including discontinuous, sporadic and isolated patches permafrost regions, which represent the primary degenerate sequence) in Northeast China. The results showed that Chloroflexi, Proteobacteria, Actinobacteria, and Acidobacteria were the most abundant phyla. The effect of permafrost degradation on bacterial relative abundance varied by species and habitats. The response of soil bacterial α-diversity (the observed OTU richness and phylogenetic diversity) in forests and wetlands to permafrost degradation were inconsistent. It was significantly correlated with mean annual temperature (MAT), mean annual precipitation (MAP), soil pH, soil microbial biomass carbon (MBC) and nitrogen (MBN) contents. The structure of soil bacterial community became increasingly dissimilar with degradation, indicating that permafrost degradation significantly changed the bacterial community structure. Climate conditions and edaphic factors jointly contribute to 92 % of the variance in the soil bacterial diversity and 40 % in community composition. The results are valuable for understanding the dynamics of soil microbial community and potential carbon feedback to future climate warming in permafrost regions.

Assessing the impact of seasonal freezing and thawing on the soil microbial quality in arid northwest China

In drylands, soil microorganisms play a vital role in restoring degraded soils, and soil microbiota is significantly affected by human activities and climate events, such as seasonal freezing and thawing. However, the response of soil microbes to freezing and thawing, as well as their properties in drylands agroecosystems, remains unknown. This study investigated the effects of seasonal freezing and thawing on soil fungal and bacterial communities, multifunctionality, and soil microbial quality in a dryland agroecosystem. It has been observed that seasonal freezing and thawing promoted nutrient releases such as total carbon and available phosphorus. After thawing, soil catalase and cellulase activities increased while acid phosphatase and urease activities and total nitrogen content at topsoil decreased. Soil microbial biomass carbon content at 0–40 cm depth was significantly reduced by 94.77 %. Importantly, freezing and thawing considerably shifted the composition of fungal groups, while the soil bacterial community exhibited more stress tolerance to freezing-thawing. Compared to pre-freezing, the relative abundance of dominant fungal phyla such as Basidiomycota and Mortierellomycota decreased. At the same time, Ascomycota increased after thawing, and the relative abundance of pathogenic fungus also increased. For dominant bacteria phylum, freezing and thawing increased the relative abundance of Proteobacteria and Gemmatimonadetes while Micrococcaceae declined. Freezing and thawing significantly increased bacterial diversity and evenness by 4.94 % and 4.19 %, respectively, but decreased fungal richness and diversity by 23.49 % and 14.91 %, respectively. The minimum and total data sets were used to evaluate soil quality and we found that freezing and thawing significantly negatively impacted soil multifunctionality and microbial quality. In summary, this study demonstrates that the seasonal freezing-thawing has a significant negative impact on soil microbial quality and multifunctionality, and accelerates soil degeneration in dryland agroecosystem.

Influence of vegetation types on soil physical and chemical properties, microbial biomass and stoichiometry in the central Himalaya

Soil physical and chemical properties and microbial biomass dynamics are significantly related to vegetation types. However, how different vegetation types influence the soil and microbial dynamics remains poorly understood. The aim of the present study is to assess the influence of vegetation types on soil physical properties (bulk density (BD), porosity, moisture, texture, and water holding capacity), chemical properties (soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), soil pH and electrical conductivity (EC), and SOC, TN and TP stocks), microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), microbial biomass phosphorus (MBP), and stocks as well as soil and microbial biomass C: N: P stoichiometry within three soil depth (0–10 cm, 10–30 cm and 30–60 cm) in central Himalaya. Five vegetation types, namely oak (Quercus leucotrichophora A. Camus) forest, Chir-pine (Pinus roxburghii Sarg.) forest, deodar (Cedrus deodara (Roxb.) G.Don) forest, Sal (Shorea robusta (Roth) forest) and one was abandoned agricultural land was selected for the present study. Principal component analysis (PCA) and correlation analyses were performed to evaluate the relationship among physical, chemical, and microbial characteristics and stoichiometry. ANOVA revealed significant differences in soil physical and chemical properties, microbial biomass, and stoichiometry due to vegetation types (P < 0.001), soil depths (P < 0.001), and vegetation types × soil depth interaction (P < 0.001). The results showed that the SOC, TN, TP, MBC, MBN, and MBP contents decreased with soil depths. MBC, MBN, and MBP contents were significantly and positively related to SOC, TN, and TP contents. Oak and deodar forests had the highest, SOC, TN, TP, MBC, MBN, and MBP contents, compared with other vegetation types. Sal forest soil (0–10 cm) had the highest SOC: TN, and SOC: TP ratios. Different vegetation types have different soil properties and stoichiometry, implying their different soil C, N, and P stocks. Thus our findings can help in developing a promising guideline for sustainable management strategies and soil management in long run.

Decay processes in Salix psammophila sand barriers increase soil microbial element stoichiomery ratios

Salix psammophila sand barriers are a widely used engineering measure to control quicksand in northwest China. Thus, it is important to elucidate the influence of the sand barrier decay process on soil microbial ecological stoichiometric characteristics in desert environments. In the present study, field in situ sampling and laboratory index measurements were used to evaluate and compare the performance degradation, variation in soil physical and chemical properties, and soil microbial ecological stoichiometry of sand barriers during decay. The results showed that with the worsening of the decay degree, all indexes of the decay characteristics decreased significantly, among which the flexural strength of mechanical properties decreased the most, which directly led to collapse and damage. The cellulose and lignin contents of the chemical components also exhibited varying degrees of decomposition, and the soil physical and chemical properties showed a significant increase. The changes in the microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) contents were consistent with the trend of the soil properties, and both reached their peak at 7 years. With the aggravation of decay, the stoichiometric ratios of soil microbial elements C, N, and P increased continuously. However, there was no significant increase in MBC/MBP and MBN/MBP in the early period (≤3 years) of the sand barrier establishment, but there was a significant increase in the later period (≥5 years). These results indicated that S. psammophila sand barriers mainly played the role of windbreak and sand fixation in the early period, and made soil microorganisms susceptible to phosphorus limitation in the later period. Stepwise linear regression analysis showed that MBC/MBN, MBC/MBP, and MBN/MBP were mainly affected by basic density (BD). Therefore, the sand barrier changes soil properties by degrading its own chemical components during the decay process and the loss of basic density is the main driving factor for increasing the C:N:P stoichiometry of soil microbial biomass. It can still be further promoted and used in the resource utilization process of mechanical sand barriers in the future.

Depth-Related Changes in Soil P-Acquiring Enzyme Activities and Microbial Biomass—The Effect of Agricultural Land Use/Plant Cover and Pedogenic Processes

Although the phosphatase enzymes regulate phosphorus (P) turnover throughout the soil profile, at present, they are rarely studied and are less well understood in the deeper soil layers than in the surface horizons. Hence the changes in P-associated soil properties were assessed throughout five Phaeozem profiles for different agricultural land uses including alfalfa, winter wheat, grapevine, apple trees and hops. The acid phosphatase (AcP), alkaline phosphatase (AlP) and phosphodiesterase (PDE) activity was assayed, as were the microbial biomass carbon (MBC) and phosphorus (MBP) contents and also other properties (e.g., available phosphorus, total organic carbon, total nitrogen). We have also determined the mass, length and surface area of the plant roots. In general, the activities of the studied enzymes were highest in the topsoil in four out of the five profiles studied, which corresponded to the highest level of root mass. The older the plant, the greater the root mass and increased enzymatic activity in the deeper horizons of apple trees and hop profiles in comparison to the surface layers. The greatest enzymatic activity, MBC and MBP contents were found in the horizons with a TOC content &gt;0.5% and decreased down the soil profiles similarly to the changes in TOC and TN contents. While the studied properties were determined to varying degrees by means of the organic C content and availability in all of the genetic horizons, the influence of the prevailing conditions and the factors related to soil depth and pedogenic processes were less pronounced. The clay content was related to a significant extent to all of the studied enzyme activities, but only in horizons with a TOC content &lt;0.5%. Significantly higher phosphatase activity under aerobic as opposed to anaerobic conditions were determined in this study, while the opposite trend was found for the content of MBC and MBP as well as the ratio of MBC/MBP. Overall, we pointed out the complex effect of the soil depth, soil forming-processes and cultivated plants on soil P-associated enzyme activities and other properties throughout the soil profiles. This knowledge will allow better understanding of the state of enzymes and their contribution to the biogeochemical cycle of soil P, especially in subsoils, where the enzyme activities follow different patterns than those in the surface horizons.

Changing precipitation effect on forest soil carbon dynamics is driven by different attributes between dry and wet areas

Changes in precipitation patterns have the potential to significantly affect the global carbon (C) cycle by altering soil organic carbon (SOC) dynamics. Comparing the patterns and drivers of soil C responses to precipitation changes in wet and dry forests can improve our understanding of soil carbon-water coupling. In this study, we conducted a meta-analysis to assess the effects of precipitation changes on soil dissolved organic carbon (DOC), microbial biomass carbon (MBC), SOC concentrations, and carbon dioxide (CO2) flux across a broad range of forest sites in dry and wet regions. The results showed that both the soil DOC and MBC concentrations decreased significantly (by averages of 7.8 and 7.9%, respectively) at the wet sites, but increased (by 1.2 and 10.2%, respectively) at the dry sites under increased precipitation conditions. The soil MBC concentrations decreased by 17.5% at the wet sites but by 4.1% at the dry sites under reduced precipitation conditions. The soil CO2 flux decreased by 18.9% and 14.3% at the wet and dry sites, respectively, under reduced precipitation. The responses of the soil MBC concentrations were influenced by precipitation intensity, whereas soil DOC and SOC concentration, and CO2 flux were regulated by the soil texture and climate. Clearly, soil MBC was more sensitive to increased precipitation at the dry sites than at the wet sites. Under reduced precipitation, changes in soil MBC concentration and CO2 flux were stronger at the wet sites than at the dry sites. To enhance forecasting of soil C cycles and functional alterations in a changing climate, the differing response mechanisms in dry and wet areas should be considered using process-based climate models.

Anticipated atmospheric CO2 elevation differentially influenced the soil microbial diversities in crop, grassland, and forest: A meta-analysis

The increasing of atmospheric carbon dioxide (CO2) has a greater impact on soil microbial diversity and related soil nutrient dynamics under different ecology. In our study, a global database of 572 observations from 202 research publications analysed to explore the impacts of increased atmospheric CO2 on soil microbial diversities. The soil microbial biomass carbon (MBC), structural (microbial populations), and functional (enzymatic activities) microbial diversities were analysed across 22 nations and 108 crops (including forest, grassland and C3 plants). The impact of three elevated CO2 (eCO2) concentrations i.e., <25%, 25–50% and >50% over ambient in three-time scale (1970–1989, 1990–2009 and 2010–2020) and two region (tropical and temperate) on the above parameters were studied. Higher MBC contents were found under eCO2 level (>50%) followed by eCO2 level 25–50% and <25% over ambient in C3 plants and forest ecology, however, in grassland the average MBC content was higher under eCO2 level 25–50%. Soil enzymatic activities were higher under eCO2 (25–50%) than other elevated CO2 conditions in the forest and C3 plants, whereas in grasslands, the enzymatic activities decreased with an increase in CO2 concentrations. These findings suggested that grassland was more sensitive to elevated CO2 as such compared to the forest and C3 plants. Both the bacterial and fungal populations were higher only up to eCO2 level (25–50% over ambient) in all the vegetations. So, higher microbial populations and soil enzymatic activities were noticed up to 50% elevation of CO2 over ambient conditions irrespective of the vegetation and region indicating higher belowground soil activities. Therefore, the findings suggested that there would be higher belowground soil activities in increased CO2 levels (anticipated climate change scenario) in agriculture and forest crop up to a certain threshold elevation of CO2 which needs better water and nutrient management for getting sustainable yield. The finding also suggested region and vegetation-specific (crop/forest/grassland) management options are necessary for fetching advantage of CO2 fertilization and to tackle the abiotic stress management of crops.

Effect of Biochar on Rhizosphere Soil Microbial Diversity and Metabolism in Tobacco-Growing Soil

In this study, four different biochar application rates and a control were set up using indoor potted tobacco, to study the effects of biochar on the microbial diversity and metabolism of tobacco-growing soil. The five treatments were as follows: control—0% biochar (w/w) + 26 g fertilizer/pot; biochar treatments—1% biochar (w/w) + 26 g fertilizer/pot, 2% biochar (w/w) + 26 g fertilizer/pot, 3% biochar (w/w) + 26 g fertilizer/pot, and 4% biochar (w/w) + 26 g fertilizer/pot. We found that biochar increases the microbial diversity of soils and simultaneously changes the microbial community structure. Under the influence of biochar, soil urease activity increased by 18%, invertase activity increased by 23.40%, polyphenol oxidase activity increased by 59.50%, and catalase activity increased by 30.92%. Biochar also significantly increased the microbial biomass carbon and nitrogen content of the soil. Soil microbial biomass nitrogen had a positive correlation on bacterial diversity, with the highest coefficient, while soil microbial biomass carbon had a positive correlation on fungal diversity, with the highest coefficient. The microbial diversity and metabolic capacity of soil are improved under the influence of biochar, and soil enzyme activity and microbial biomass carbon and nitrogen have positive impacts on soil microbial diversity.

Seasonal freeze-thaw characteristics of soil carbon pools under different vegetation restoration types on the Longzhong Loess Plateau

Soil carbon pools are important for maintaining the stability of the carbon cycle in terrestrial ecosystems and regulating climate change. However, it is not clear how soil carbon pools change under different vegetation restoration types at high altitudes during frequent seasonal freeze-thaws (FTs). Therefore, we studied the seasonal FT variability (before freezing, early stages of freezing, stable freeze stage, thawing stage) of soil organic carbon (SOC), microbial biomass carbon (MBC), dissolved organic carbon (DOC), and easily oxidized organic carbon (EOC) under three vegetation restoration types (Grassland, GL; Caragana korshinskii, CK; Xanthoceras sorbifolia, XS) on the Longzhong Loess Plateau region. We found that during the seasonal FT, the 0–40 cm SOC, MBC, DOC, and EOC contents were higher in XS vegetation than in GL and CK vegetation, but the sensitivity index of SOC was lower in XS vegetation (sensitivity index = 2.79 to 9.91). In the 0–40 cm soil layer, the seasonal FT process reduced the MBC content and increased the DOC content in the three vegetation soils. Meanwhile, DOC and EOC contents accumulated obviously in the stable freezing period and decreased significantly in the thawing period. We also found that the SOC, MBC, DOC, and EOC contents were higher in the surface soils (0–10 cm) than in the underlying soils (10–20 and 20–40 cm), while the sensitivity of the soil carbon pool fractions to seasonal FT processes differed considerably between soil depths. Redundancy analysis (RDA) showed that soil total nitrogen, temperature, total phosphorus, and soil water content were important environmental factors influencing soil carbon pool fractions during seasonal FT. This study suggested that in the Longzhong Loess Plateau region, soil MBC and DOC were more susceptible to seasonal FT phenomena and that the soil system of the Xanthoceras sorbifolia vegetation had a stronger soil C sequestration function during the seasonal FT process.

Comparative evaluation of changes in soil bio-chemical properties after application of traditional and enriched vermicompost

For nutrient-deficient soils, vermicompost is an excellent soil additive. We find biochemical fluctuations in soil by comparing enriched vermicomposts to regular vermicomposts in a carefully controlled pot experiment. Various rock minerals, including mica, dolomite, and rock phosphate (RP), were used to create the enriched vermicompost before it was applied to acid lateritic soil, and so we investigated how vermicompost’s biochemical impact on the soil evolves (15-day intervals). Our results suggested that traditional vermicompost (VC) prepared from water hyacinth effectively improves nutrient content, enzymatic activities, and soil microbial properties. However, enriched VC application significantly (p<0.05) augments the concentration of available P (60% higher than conventional VC) and exchangeable K (increased by 10% from conventional VC) in soil. Furthermore, we observed that enrichment of VC using a combination of rock minerals showed significantly higher urease (around 35%), acid phosphatase activity (by 93%), and enhanced microbial biomass carbon (about 25%) and nutrient content of soil compared to only rock mineral additions. Nevertheless, our study revealed that conventional VC shows better soil organic carbon build-up than rock-based enriched VC. Although, enrichment conferred differential benefits to the soil in terms of increased P in RP-based and raised K in MC-based VC. • Organic wastes recycled to enriched vermicompost may better cater to plant needs. • Additives like rock minerals and microbes enhance macro-nutrients in final product. • Enhanced enzymatic activities can be observed with enriched vermicompost. • Enrichment of vermicompost may better serve to goals of sustainable agriculture.