Nutrient Cycling Processes Research Articles

Contrasting patterns of microbial nutrient limitations between rhizosphere and bulk soil during stump sprout restoration in a clear-cut oak forest

Microbial metabolism changes in soil systems along a vegetation restoration gradient have attracted considerable attention; however, the differences in microbial metabolic limitations between the rhizosphere and bulk soil and their drivers during natural secondary forest restoration after disturbance have rarely been investigated. Here, we used multiple methods based on extracellular enzymatic stoichiometry to examine the microbial metabolic limitations in the rhizosphere and bulk soils along with a clear-cut oak (Quercus aliena var. acuteserrata) forest restoration over 58 years in the Qinling Mountains, China. Overall, the microbial metabolisms in both rhizosphere and bulk soils were co-limited by the availability of soil carbon (C) and phosphorus (P), and the limitations tended to decrease during restoration. Rhizosphere soil microorganisms were subject to relatively strong C limitation and weak P limitation compared with those in bulk soil. Microbial C and P limitations in the bulk soil were regulated by the nutrient ratios, and those in the rhizosphere soil were mainly dependent on the available nutrients mediated by soil moisture. Our results indicate that variations in the soil nutrients caused by oak forest restoration and water differences caused by the rhizosphere effect regulated microbial C and P metabolism in the rhizosphere and bulk soils. This study highlights the microbial metabolism difference between rhizosphere and bulk soil and its drivers during oak forest restoration and provides insights into the microbial resource limitation, nutrient cycling, and rhizosphere processes in the natural secondary forests after clear-cutting.

Nutrient Cycling of Cover Crops in an Amazonian Ecosystem

Cover crops act to improve the chemical and physical quality of the soil and provide sustainability in agricultural systems. Studying the decomposition of these cover crops is key to understand the process of nutrient cycling in cultivation. The purpose of the study was to assess the decomposition and release of nutrients from cover crops in an Amazonian ecosystem. The experiment was conducted in a commercial guarana plantation area at farm Agropecuária Jayoro in Presidente Figueiredo-AM in two agricultural years (2018 and 2019), with a randomized block experimental design following a 4 × 4 factorial scheme, with four cover species (Arachis pintoi, Brachiaria ruziziensis, Canavalia ensiformis and Mucuna deeringiana) and four assessment periods (0, 60, 120, 180 days). The cover crops showed a high rate of decomposition of residues in the two years assessed. The legumes presented high initial nutrient contents. The release of N, P, Ca, and Mg was slower. K showed a rapid release from the decomposition of the residues of the assessed cover crops.

Energy flux across multitrophic levels drives ecosystem multifunctionality: Evidence from nematode food webs

Energy flux in food webs, i.e., energy consumption by different trophic groups and describing their energetic structure, has been proposed as a powerful tool to understand the relationships between biodiversity and multiple ecosystem functions (ecosystem multifunctionality). Here we examined how different fertilization regimes affected the energy flux across multitrophic levels of soil nematodes in the paddy rice and upland maize fields. We considered 13 ecosystem functions of four ecological processes related to plant productivity, nutrient cycling processes and drivers, and functional stability, which are central to energy and nutrient flow across trophic levels. To confirm whether multitrophic flux would underpin the relationships between biodiversity and multifunctionality, we compared energy flux with other approaches including taxonomic diversity, functional diversity and community composition. Results showed that organic fertilizer supported 33–340% greater multitrophic energy flux of soil nematode community and enhanced 41–264% of ecosystem multifunctionality in both fields compared with mineral fertilizer treatments. Organic fertilization enhanced ecosystem multifunctionality by favoring energy flux in multitrophic levels of soil nematodes, while fertilization-mediated changes in other facets of biodiversity were less related to multifunctionality. Our study provides empirical evidence that energy flux within food webs can be used to understand the impacts of environmental change drivers on ecosystem multifunctionality.

Limited legacy effects of extreme multiyear drought on carbon and nitrogen cycling in a mesic grassland

The intensification of drought throughout the U.S. Great Plains has the potential to have large impacts on grassland functioning, as has been shown with dramatic losses of plant productivity annually. Yet, we have a poor understanding of how grassland functioning responds after drought ends. This study examined how belowground nutrient cycling responds after drought and whether legacy effects persist postdrought. We assessed the 2-year recovery of nutrient cycling processes following a 4-year experimental drought in a mesic grassland by comparing two different growing season drought treatments—chronic (each rainfall event reduced by 66%) and intense (all rain eliminated until 45% of annual rainfall was achieved)—to the control (ambient precipitation) treatment. At the beginning of the first growing season postdrought, we found that in situ soil CO2 efflux and laboratory-based soil microbial respiration were reduced by 42% and 22%, respectively, in the intense drought treatment compared to the control, but both measures had recovered by midseason (July) and remained similar to the control treatment in the second postdrought year. We also found that extractable soil ammonium and total inorganic N were elevated throughout the growing season in the first year after drought in the intense treatment. However, these differences in inorganic N pools did not persist during the growing season of the second year postdrought. The remaining measures of C and N cycling in both drought treatments showed no postdrought treatment effects. Thus, although we observed short-term legacy effects following the intense drought, C and N cycling returned to levels comparable to nondroughted grassland within a single growing season regardless of whether the drought was intense or chronic in nature. Overall, these results suggest that the key aspects of C and N cycling in mesic tallgrass prairie do not exhibit persistent legacies from 4 years of experimentally induced drought.

Global patterns and drivers of initial plant litter ash concentration

Ash is a fundamental component of plant litter and plays a vital role in regulating litter decomposition. However, to date, global patterns and underlying mechanisms of initial litter ash concentrations remain unclear. Here, we used 570 observations collected from 104 independent publications to assess the global patterns of initial plant litter ash concentrations and evaluated the effects of mycorrhizal association [arbuscular mycorrhiza (AM) vs. ectomycorrhiza (ECM)], taxon group (gymnosperm vs. angiosperm), life form (tree vs. shrub vs. herb), leaf type (broadleaf vs. needle), and environmental factors such as climate and soil properties on initial litter ash concentration. The results showed that (1) global average ash concentrations varied significantly among different plant tissues and were 7.3, 4.5, 3.7, 3.5, 3.1, 2.4, and 1.5% in leaf, root, bark, reproductive tissue (flower and fruit), branch, stem, and wood litter, respectively; (2) in leaf litter, the initial ash concentrations of AM plants and species associated with both AM and ECM fungi were higher than those of ECM plants, and those of the tree species were lower than those of the herbs and shrubs; in root litter, the initial ash concentrations of the AM plants were lower than those of the species associated with both AM and ECM fungi but higher than those of the ECM plants; in both leaf and root litter, the initial ash concentrations of the angiosperms and broadleaf trees were higher than those of the gymnosperms and needle trees, respectively, while the effect of plant traits on branch litter was not obvious; and (3) the initial ash concentration of leaf litter was predominantly driven by mycorrhizal association and taxon group, while that of root litter tended to be driven by mycorrhizal association well as soil organic carbon. Our study clearly assessed the global patterns and underlying mechanisms of initial plant litter ash concentrations, which could help in better understanding the role of ash in litter decomposition and the related processes of carbon and nutrient cycling.

Mowing Facilitated Shoot and Root Litter Decomposition Compared with Grazing

Shoot and root litter are two major sources of soil organic carbon, and their decomposition is a crucial nutrient cycling process in the ecosystem. Altitude and land use could affect litter decomposition by changing the environment in mountain grassland ecosystems. However, few studies have investigated the effects of land use on litter decomposition in different altitudes. We examined how land-use type (mowing vs. grazing) affected shoot and root litter decomposition of a dominant grass (Bromus inermis) in mountain grasslands with two different altitudes in northwest China. Litterbags with 6 g of shoot or root were fixed in the plots to decompose for one year. The mass loss rate of the litter, and the environmental attributes related to decomposition, were measured. Litter decomposed faster in mowing than grazing plots, resulting from the higher plant cover and soil moisture but lower bulk density, which might promote soil microbial activities. Increased altitude promoted litter decomposition, and was positively correlated with soil moisture, soil organic carbon (SOC), and β-xylosidase activity. Our results highlight the diverse influences of land-use type on litter decomposition in different altitudes. The positive effects of mowing on shoot decomposition were stronger in lower than higher altitude compared to grazing due to the stronger responses of the plant (e.g., litter and aboveground biomass) and soil (e.g., soil moisture, soil bulk density, and SOC). Soil nutrients (e.g., SOC and soil total nitrogen) seemed to play essential roles in root decomposition, which was increased in mowing plots at lower altitude and vice versa at higher altitude. Therefore, grazing significantly decreased root mass loss at higher altitude, but slightly increased at lower altitude compared to mowing. Our results indicated that the land use might variously regulate the innate differences of the plant and edaphic conditions along an altitude gradient, exerting complex impacts in litter decomposition and further influencing carbon and nutrient cycling in mountain grasslands.

Dynamic changes of rhizosphere soil bacterial community and nutrients in cadmium polluted soils with soybean-corn intercropping

BackgroundSoybean-corn intercropping is widely practised by farmers in Southwest China. Although rhizosphere microorganisms are important in nutrient cycling processes, the differences in rhizosphere microbial communities between intercropped soybean and corn and their monoculture are poorly known. Additionally, the effects of cadmium (Cd) pollution on these differences have not been examined. Therefore, a field experiment was conducted in Cd-polluted soil to determine the effects of monocultures and soybean–corn intercropping systems on Cd concentrations in plants, on rhizosphere bacterial communities, soil nutrients and Cd availability. Plants and soils were examined five times in the growing season, and Illumina sequencing of 16S rRNA genes was used to analyze the rhizosphere bacterial communities.ResultsIntercropping did not alter Cd concentrations in corn and soybean, but changed soil available Cd (ACd) concentrations and caused different effects in the rhizosphere soils of the two crop species. However, there was little difference in bacterial community diversity for the same crop species under the two planting modes. Proteobacteria, Chloroflexi, Acidobacteria, Actinobacteria and Firmicutes were the dominant phyla in the soybean and corn rhizospheres. In ecological networks of bacterial communities, intercropping soybean (IS) had more module hubs and connectors, whereas intercropped corn (IC) had fewer module hubs and connectors than those of corresponding monoculture crops. Soil organic matter (SOM) was the key factor affecting soybean rhizosphere bacterial communities, whereas available nutrients (N, P, K) were the key factors affecting those in corn rhizosphere. During the cropping season, the concentration of soil available phosphorus (AP) in the intercropped soybean–corn was significantly higher than that in corresponding monocultures. In addition, the soil available potassium (AK) concentration was higher in intercropped soybean than that in monocropped soybean.ConclusionsIntercropped soybean–corn lead to an increase in the AP concentration during the growing season, and although crop absorption of Cd was not affected in the Cd-contaminated soil, soil ACd concentration was affected. Intercropped soybean–corn also affected the soil physicochemical properties and rhizosphere bacterial community structure. Thus, intercropped soybean–corn was a key factor in determining changes in microbial community composition and networks. These results provide a basic ecological framework for soil microbial function in Cd-contaminated soil.

Distinct kin strategies of the legume soybean and the non-legume balsam by accomplishing different nitrogen acquisition and rhizosphere microbiome composition.

SUMMARYKin selection has been proposed vvto be an important mechanism for plant relatives growing together. To reveal kin recognition, we used15N labeling to assess the short‐term nitrogen (N) acquisition (uptake of nitrate and ammonium), long‐term N utilization (recovery of added urea), N‐use efficiency (NUE) and rhizosphere microbiome in leguminousGlycine maxand non‐leguminousImpatiens balsamina. Individuals of each species were planted pairwise with either a sibling or a stranger. Enzyme activity and soil microbial composition were compared between kinship groups. Compared with strangers,G. maxsiblings increased aboveground biomass, NUE, and nitrogenase activity, whereasI. balsaminasiblings decreased root biomass and increased uptake rate of nitrate and potential nitrification rate. Plant kinship affected soil bacterial communities by enriching specific groups possessing explicit eco‐functions (Rhizobiales forG. maxandNitrospiraforI. balsamina). Kinship‐sensitive operational taxonomic units formed independent modules in the bacterial co‐occurrence network and were positively correlated with plant growth performance, N acquisition and enzymatic activity. Plant kin recognition may depend on the growth strategies of the plant species. Kin selection was dominant inG. maxby enhancing biological N fixation through the enrichment of symbiotic rhizobia (demonstrated by aboveground growth and NUE superiority among siblings). Kin selection and niche partitioning occurred simultaneously inI. balsamina, expressed through reduced root allocation but increased nitrate uptake, and enhanced soil N nitrification, by enriching functional microbial groups. Kin recognition responses are the consequence of complex interactions among the host plant, the microbiome, and soil nutrient cycling and utilization processes.

Short-term exposure to soils and sludge induce changes to plastic morphology and 13C stable isotopic composition

There is concern about the buildup of plastic waste in soil, their degradation into microplastics, and their potential to interfere with the natural processing of soil organic carbon and other nutrient cycling processes. Here we used scanning electron microscopy (SEM) and 13C isotope ratio mass spectrometry to determine if precut consumer plastics comprised of either high density polyethylene (HDPE), a blend of linear low density polyethylene and low density polyethylene (L/LDPE), or polyethylene terephthalate (PETE) would degrade or transform during a short-term, 32 day, exposure to soil or sludge in laboratory microcosms. SEM confirmed morphological changes occurred to all plastics, but the attachment of biofilm and presence of microorganisms mostly favored PETE and HDPE surfaces. These observations support the idea that abiotic and/or biotic processes may degrade plastics in soil; however distinguishable and significant changes in mean stable isotopic values (Δδ13C) of ~0.2–0.7‰ were only observed for exposed PETE and HDPE. This indicates that each plastic's degradation in soil may be dependent on their physical and chemical properties, with L/LDPE being more resistant and less prone to degradation compared to the others, and less dependent on the environmental conditions or properties of the soil or sludge. Our experiments were short-term and while the mechanisms of degradation are not clear, the results provide strong motivation for further studies of plastic fate and processing in soil systems. Direct mechanistic studies using stable isotopic approaches in combination with other characterizations and techniques are clearly warranted and may lead to a significant enhancement in our present understanding of the interactions and dynamics of plastics in the soil environment.

Bioindicators of Behavior and Regeneration of a Caatinga Area in the Brazilian Semi-Arid - A Review

Studies that allow the understanding of the nutrient cycling processes and maintenance of soil fertility in the caatinga biome are necessary to assist in the proposal of possible management forms, in view of the sustainability of this ecosystem, to provide data in an area of knowledge the quantification of glomalin can be a good indicator of changes caused by the use of the soil and, in turn, therefore, it can become a good indicator of its recovery because it is correlated with important attributes of the soil. In addition to providing data of this process for a better understanding of the soils of the country, a study on this subject will also contribute with a new database for global monitoring. Research that can follow the regeneration rate of Caatinga forests in the Semi-arid will allow the development of models relating to several variables, not currently available for the semi-arid tropical region.

降水变化和氮沉降对荒漠草原两种多年生禾草凋落物分解的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 降水变化和氮沉降对荒漠草原两种多年生禾草凋落物分解的影响 DOI: 10.5846/stxb202103230769 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（31560156，31860136）；内蒙古自治区自然科学基金（2017MS0350） Effects of precipitation and nitrogen deposition on litter decomposition of two perennial grasses in a desert steppe 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:凋落物分解是陆地生态系统养分循环的重要过程，在生物地球化学循环过程中发挥着重要作用。全球变化是影响凋落物分解的重要因子，其对生态系统养分循环的影响存在诸多不确定性。研究荒漠草原凋落物分解对氮沉降和降水变化及其二者交互作用的响应，是揭示这些不确定性、保护草原生态系统结构和功能的科学基础。以内蒙古四子王旗短花针茅荒漠草原为研究对象，选取建群种短花针茅和优势种无芒隐子草两种植物凋落物，开展为期4年的长期分解实验，探究两种植物凋落物分解特征及养分释放规律。实验采用裂区设计，主区为自然降水（C）、增雨30%（W）和减雨30%（R）3个水分梯度，副区为0（N0）、30（N30）、50（N50）和100（N100） kg hm-2 a-1 4个氮素梯度。结果表明：（1）增雨和氮沉降促进荒漠草原凋落物分解，减雨反之，降水对两种凋落物影响具有差异，而氮沉降的作用不依赖于物种；（2）氮沉降缩短凋落物分解周期5.12%-14.82%，增雨与氮沉降交互缩短凋落物分解周期3.69%-28.75%；（3）降水始终有利于凋落物中碳、纤维素和木质素释放，而分解后期氮沉降对其影响不显著，凋落物分解后期主要受木质素分解速率控制。综上所述，影响荒漠草原凋落物分解的主要因素为降水，其次是氮素，二者对凋落物分解具有协同作用。 Abstract:Abstract:Litter decomposition is an important process of ecosystem nutrient cycling, which plays an important role in biogeochemical cycling. Global change is an important factor affecting litter decomposition, but there are many uncertainties in its impact on ecosystem nutrient cycling. Studies on the response and feedback of litter decomposition of desert steppe to the increased nitrogen deposition and precipitation change will provide the scientific basis for revealing these uncertainties and protecting the structure and function of grassland ecosystem. In this study, taking S. breviflora desert steppe in Siziwang Banner, Inner Mongolia as the research object, two kinds of plant litter, the dominant species S. breviflora and C. songorica, were selected to carry out a 4-year decomposition experiment, to explore the litter decomposition characteristics and nutrient release patterns of the two kinds of plants. The experiment used split-pot design, with precipitation as the whole-plot factor and N as the split-pot factor. Precipitation treatments include addition 30% (W), removal 30% (R), and ambient precipitation(C). Nitrogen was added at 0 (N0), 30 (N30), 50 (N50) and 100 (N100) kg hm-2 a-1. The results show that:(1) Increased precipitation and nitrogen deposition promoted litter decomposition in the desert steppe. Furthermore, the precipitation effects were different between the two kinds of litter, while the effect of nitrogen deposition does not depend on species; (2) Nitrogen deposition shortened the litter decomposition duration by 5.12%-14.82%, and the interaction between precipitation enhancement and nitrogen deposition shortened the litter decomposition duration by 3.69%-28.75%; (3) Precipitation was always beneficial to the release of carbon, cellulose and lignin from litter, but nitrogen deposition had no significant effect on it in the later stage of litter decomposition, and the late stage of litter decomposition is mainly controlled by the decomposition rate of lignin. In conclusion, the main factor affecting the decomposition of litter in the desert steppe is precipitation, followed by nitrogen, and the two factors have a synergistic effect on decomposition of litter. 参考文献 相似文献 引证文献

Does selective logging affect litter deposition rates in central Brazilian Amazonia?

Selective logging is one of the main human activities that are drastically modifying tropical forests around the world. Reduced-impact logging emerged as a rational model of timber harvesting that reduces the impacts on the ecosystems and contributes to the conservation of natural resources. Nevertheless, this type of activity may still alter the forest structure, nutrient cycling, soil drainage, and other important ecosystem processes. Here, we aimed at testing the effects of selective logging on litter deposition in central Brazilian Amazonia. We estimated litter production during one dry and one rainy season in 11 sites logged between 2003 and 2017 and one unlogged site. Mean litter deposition was greater during the dry season. Although litter deposition rates varied between a few study sites, this variation was independent of the time after logging. The results suggest that the low logging intensity in the study site (16.8 m³/ha) had no intense impacts on litter deposition. Reduced-impact logging may be an alternative for the use of forest resources in Amazonian forests without compromising nutrient cycles.

亚热带米槠天然林凋落物和根系输入变化对土壤磷组分的影响

植物残体添加和去除试验(The Detritus Input and Removal Treatments, DIRT)是研究地上凋落物以及植物根系对土壤营养物质循环过程及机制探究的一种试验设计。于2012年6月选择福建省三明森林生态系统与全球变化研究站的米槠常绿阔叶天然林, 设置5种处理：对照(CT)、去除凋落物(NL)、去除根系(NR)、去除凋落物与根系(NI)、添加双倍凋落物(DL), 在2018年12月对各处理不同土层(0-10cm、10-20cm)土壤磷组分及其影响因子进行研究, 结果表明：(1)在0-10cm土层中DL处理总磷含量显著大于NL处理, NI处理无机磷含量最低, 在10-20cm中DL处理有机磷含量显著大于其他处理；(2)DL处理活性磷(Resin-P、NaHCO₃-Pi、NaHCO₃-Po)含量在0-10cm土层中显著大于其他处理。在10-20cm土层中NR处理活性磷以及中等活性磷显著大于NL处理。残留态磷(Residual-P)含量最高, 但在各处理与土层之间并没有明显差异；(3)酸性磷酸酶在0-10 cm土层不同处理间的变化趋势明显, CT处理活性最高, NI处理活性最低。NR与NL处理在10-20cm土层的差异并不明显。冗余分析表明, 土壤磷组分的变化主要受酸性磷酸酶、土壤含水率、可溶性有机氮以及总氮的影响。凋落物的输入对促进土壤磷素增加, 改善土壤质量具有重要意义；植物根系则对土壤磷的活化与稳定具有关键作用。;The detritus input and removal treatment is an experimental design to study the effects of aboveground litter and plant roots on soil nutrient cycling process and mechanism. In June 2012, we set up five treatments, viz. control (CT), no litter (NL), no roots (NR), no input (NI), and double litter (DL), in a natural evergreen broad-leaved forest of Castanopsis carlesii in Sanming, Fujian Province. Soil phosphorus fractions and their influencing factors in different soil layers (0-10 cm and 10-20 cm) of each treatment were studied in December 2018. The results showed that: (1) in the 0-10 cm soil layer, the total phosphorus content in DL treatment was significantly higher than that in NL treatment. The inorganic phosphorus content in NI treatment was the lowest, The organic phosphorus content in DL treatment was significantly higher than other treatments in 10-20 cm soil layer; (2) The contents of easily-available phosphorus fractions (Resin-P, NaHCO₃-Pi, NaHCO₃-Po) in DL treatment were significantly higher than those in other treatments in 0-10 cm soil layer. In 10-20 cm soil layer, the easily-available phosphorus and moderately-available phosphorus in NR treatment were significantly higher than those in NL treatment. The content of residual-P was the highest, but there was no significant difference between the treatment and soil layer; (3) The change trend of acid phosphatase in 0-10 cm soil layer was obvious among different treatments. CT treatment had the highest activity and NI treatment had the lowest activity. The difference between NR and NL treatments was not obvious in 10-20 cm soil layer. Redundancy analysis showed that the changes of soil phosphorus fractions were mainly affected by acid phosphatase, soil moisture content, dissolved organic nitrogen, and total nitrogen. Adding litter could mineralize organic phosphorus by increasing soil microbial biomass and enhancing soil acid phosphatase activity, promote the transformation of soil organic phosphorus to inorganic phosphorus, and improve the availability of soil phosphorus. However, root system could absorb soil active phosphorus and mineralize other phosphorus fractions. It had positive significance to improve the structure of P in soil.

自然增温对南亚热带森林土壤微生物群落与有机碳代谢功能基因的影响

基于海拔高度下降气温上升的关系，将模拟的生态系统（含植物和土壤）从高海拔整体移位至低海拔地区，实现自然增温的效果。通过对自然增温条件下土壤环境因子及其相关理化性质的动态监测，结合磷脂脂肪酸分析与宏基因组学方法，测定土壤微生物群落结构以及与土壤有机碳分解相关基因丰度，探究自然增温对鼎湖山南亚热带山地常绿阔叶林土壤有机碳代谢的影响及其微生物学机制。结果表明：（1）增温处理显著改变了0-10 cm土壤温度与湿度：2016-2018年间土壤温度显著上升2.48℃，湿度显著下降23.93%。（2）增温处理下，干季土壤有机碳含量与湿季土壤硝态氮含量显著降低，其他土壤理化因子无显著变化。（3）增温处理下，干季和湿季土壤微生物群落结构发生改变，且湿季变化显著。土壤湿度是影响干季和湿季土壤微生物群落结构变化的主要因子，解释了干季50.2%的变异度与湿季79.2%的变异度。（4）宏基因组结果表示：增温抑制了干季山地常绿阔叶林土壤有机碳代谢基因丰度，增强了湿季山地常绿阔叶林土壤有机碳代谢基因丰度。以上结果表明，增温通过改变土壤微生物生物量和群落结构以及有机碳代谢相关功能基因的丰度，最终影响南亚热带山地常绿阔叶林土壤有机碳代谢过程。;Global warming is one of the environmental problems that cannot be ignored in the world today, which has significant impacts on soil carbon dynamics and soil microorganisms. Soil microorganisms affect the soil nutrient cycling process and play a leading role in the net carbon balance of terrestrial ecosystems. Further exploration of microbial responses to climate warming is important for predicting the feedback and carbon budget of terrestrial ecosystems in warmer climates. In this study, soil organic carbon content and microorganisms were investigated in a natural warming experiment using a whole ecosystem transplanting approach. Plots of plants and soil in a subtropical mountain evergreen broadleaf forest at high altitude (600 m asl) were moved to low altitude (30 m asl) in Dinghu Mountain to experience natural warming treatment. Plots with similar plants and soil at the high altitude were used as the control. To explore the effect of natural warming on soil organic carbon metabolism and its microbiological mechanism, soil physical and chemical properties, soil organic carbon, and soil microbial community structure were measured for the control and warmed plots. Meta-genomic method was used for soil microbial community structure and abundance of genes involved in soil organic carbon decomposition. Results showed that:(1) warming treatment significantly changed soil temperature and moisture of the 0-10 cm soil layer. From 2016 to 2018, the soil temperature was significantly increased by 2.48℃, and the soil moisture was significantly decreased by 23.93% (relative change). (2) Warming treatment significantly reduced soil organic carbon content in the dry season and the soil nitrate nitrogen content in the wet season, while other soil physical and chemical factors had no significant changes under warming treatment. (3) Warming treatment changed the soil microbial community structure in both dry and wet seasons, and the change was significant in wet season. The results of principal component analysis showed that soil moisture was the main factor affecting the variation of soil microbial community structure in dry season and wet season, which explained the variation degree of 50.2% in dry season and 79.2% in wet season. (4) The metagenomic analysis showed that increasing temperature inhibited the abundance of soil organic carbon metabolism genes of mountain evergreen broadleaf forest in the dry season, and enhanced them in the wet season. Our results showed that although warming treatment did not significantly change soil microbial biomass in the subtropical mountain evergreen broadleaf forest, it reduced soil organic carbon by changing soil microbial community structure and abundance, and significantly affected soil organic carbon metabolic processes and ecosystem carbon cycling.

Managing Soil Health Towards Sustainable Agriculture

Macro and microorganisms play a crucial role in improving soil health. Soil organisms decompose complex organic substances and release nutrients. Further, they involve in nutrient cycling and transformation process in the soil. Population dynamics of soil organisms depend on many external factors including human activities, climate change, contaminations and soil erosion. Hence, adverse conditions may create a tremendous pressure on soil biota leading to large-scale land degradation and loss of productivity in the long run. The positive effect of soil organic matter (SOM) on soil health is well documented. Soil organic matter serves as a source of nutrients for plant growth, enhances soil aggregation, retains soil moisture, increases infiltration and reduces the risk of soil erosion. Depletion of SOM pool specially in farmlands is a global issue. Therefore, it is essential to manage SOM pool above the threshold level (1.0 -1.5%) in order to reverse the process of soil degradation. In addition, quality and quantity of SOM pool is one of the crucial factors in order to strengthening resilience and reduce risk of soil degradation. It has been reported that, depletion of Soil Organic Carbon (SOC) pool is grater when essential nutrients are limited in the soil for microbial growth. Thus, application of organic manure with alternative nutrient sources could be a better option to increase SOC pool and soil health.

Changes in the microbial community structure triggered by permafrost peat thawing

An increase in permafrost temperature, accompanied by the melting and release of buried organic carbon, is one of the elements of the global warming scenario. To understand the way ecosystems respond to environmental changes, it is necessary to elucidate the factors affecting the distribution and activity of microbes in permafrost soils, which have been poorly studied so far. Meanwhile, they can have significant implications for nutrient cycling and related processes. Our research is devoted to assessing changes in the structure of the microbial community due to the melting of the palsa permafrost layer caused by the fire in 2007. The ecological-trophic groups of microorganisms of the territories changed under the influence of a natural fire in comparison with undisturbed analogs have been studied. It was revealed that the number of microorganisms in most groups on the palsa, affected by fire, is statistically significantly higher than the number of microorganisms in the undisturbed area.

Arbuscular mycorrhizal fungi outcompete fine roots in determining soil multifunctionality and microbial diversity in a desert ecosystem

Fine roots and mycorrhizal fungi play a crucial role in soil nutrient cycling and microbial processes. However, the importance of the symbioses between fine roots and arbuscular mycorrhizal fungi (AMF) in different plant functional groups to maintain soil multifunctionality (the ability to provide multiple functions and services) and microbial diversity remains unclear, especially in desert ecosystems. In this study, we conducted an ingrowth core experiment on three vegetation types, namely shrub-dominated, grass-dominated, and mixed vegetation communities, in the Mu Us Desert, northern China, to investigate the importance of fine roots and mycorrhizal fungi in shaping soil nutrient composition and microbiome. Furthermore, we detected the relationships among AMF-related inputs [extraradical AMF hyphae and glomalin-related soil protein (GRSP)], soil multifunctionality, and soil microbial diversity. We found that most of the soil properties associated with nutrient cycling and microbial community composition and diversity varied among the three vegetation types, but were not significantly different between distinct ingrowth core treatments with fine root and hyphal access. AMF-related inputs, especially the easily extractable GRSP, were the most important determinants of soil multifunctionality and microbial community diversity across the shrub and grass communities, while the changes in soil multifunctionality and microbial diversity were inconsistent with the trend of fine root biomass. Moreover, AMF-related inputs were positively correlated with soil nutrients, particularly soil organic carbon (SOC). In contrast to the minimal negative correlation between SOC and soil microbial richness, soil multifunctionality was positively correlated with SOC. These findings support the role of AMF in shaping soil multifunctionality and microbial diversity by stabilizing SOC in a desert ecosystem, regardless of the fine root accessibility of plant functional groups. Therefore, this study improved our understanding of plant-derived carbon in the soil and its effects on the induction of soil abiotic and biotic processes in resource-limited ecosystems.

Spatial Distributions of Nitrogen and Phosphorus in Surface Sediments in Intertidal Flats of the Yellow River Delta, China

The spatial distributions of nitrogen (N) and phosphorus (P) in surface sediments are of great significance in studying the ecological process of nutrient cycling in intertidal flats. However, little is known about N and P’s spatial distribution in intertidal flats of the Yellow River Delta (YRD). We analyzed the N and P contents in surface sediments and Suaeda glauca density at the low-tidal level to identify the spatial distributions of nutrients and their influencing factors in coastal tidal flat sediments. The results showed that the total nitrogen (TN) and total phosphorus (TP) concentrations in this study were both lower than the background values of China’s shallow sea sediments. The spatial distributions of N and P had significantly spatial heterogeneity, while those of the nutrients at different distances from the low-tidal level to the coastline showed no significant distance effects. The spatial distribution of S. glauca in coastal tidal flats had significant location characteristics and was closely related to the distribution of TN and pH. The TN in non-estuarine intertidal flats was less than that in estuaries; in contrast, the TP was higher in non-estuaries. There are some differences of N and P between estuary and non-estuary areas.

Birds of the Pantanal floodplains, Brazil: historical data, diversity, and conservation

The Pantanal floodplains of Brazil are a region of rich biodiversity. To date, the true richness of the Pantanal avifauna has not been explored satisfactorily caused by a lack of studies in the region and, especially, by the divergence of opinion among the works published by various authors on the many species found in the region. This is due to the lack of criteria in examining records, both with regard to the reliability of the identifications and in the precise geographical allocation. Therefore, in the study, we collage findings from various studies and records created by us in the last few decades from 199 distinct locations to produce a list of birds in the Pantanal floodplains. We grouped the results into three lists: primary, secondary, and tertiary. We found that the avifauna of the Pantanal floodplain is composed of a total of 617 species, of which 571 (92%) have supporting records of occurrence (primary list) and 46 still lack documentation (secondary list). The number of species listed here for the Pantanal floodplain represents 32% of all avifauna known to the Brazilian territory. This reflects the importance of the biome, as part of the national territory, for the maintenance of a meaningful avifaunistic richness. Migratory birds (n = 183), notably northern ones (n = 43), are among the main players involved in ecological processes of nutrient cycling and dispersion of important pathogens between the two continents. With regard to conservation, 25 species are included in some category of threat in the lists of threatened species with global extinction. We hope that our list will help future researchers a more definitive approach when researching the avian fauna in this bountiful region.

Variations of earthworm gut bacterial community composition and metabolic functions in coastal upland soil along a 700-year reclamation chronosequence

Most ecosystem functions attributed to earthworms are mediated by their internal microbiomes, and these are sensitive to disturbances in the external environment. However, few studies have focused on the response of the earthworm gut microbiome to soil chronosequence. Here, we used 16S rRNA high-throughput sequencing and high-throughput quantitative PCR to investigate the variations in bacterial communities and functional gene abundance in earthworm (Lumbricina sp.) guts and upland soils under 700 years of cultivation. Our results indicated that 700 years of upland cultivation significantly shaped bacterial communities and increased functional traits of microbes in earthworm guts, which were more sensitive to cultivation age compared to the surrounding soils. The earthworm gut bacterial community changed rapidly over the first 300 years of cultivation and then changed slowly in the following centuries. Along with the cultivation age, we also observed that the earthworm gut microbiota was successive towards a copiotrophic strategy (e.g., Xanthobacteraceae, Nocardioidaceae, Hyphomicrobiaceae, and Bacillaceae) and higher potential functions (e.g., ureC, nirS, nosZ, phoD, and pqqC). Furthermore, canonical correspondence analysis further revealed that soil pH, C:N ratio, soil organic carbon, and total nitrogen were key abiotic drivers shaping earthworm gut bacterial communities. Taken together, this study reveals the succession of bacterial communities and potential functions in earthworm guts within 700 years of upland cultivation, which may provide a broader space for us to rationally exploit and utilize the interactions between soil and earthworm gut microbiotas to benefit the soil nutrient cycling process.