Soil Ecological Factors Research Articles

Altitude Distribution Patterns and Driving Factors of Rhizosphere Soil Microbial Diversity in the Mountainous and Hilly Region of Southwest, China

The distribution characteristics of the microbial community in rhizosphere soils of different altitudinal gradients were explored to uncover ecological factors affecting microbial community composition. In this study, the community variations of bacteria and fungi in the rhizosphere soil of Chrysanthemum indicum L. were analyzed. Samples were distributed along an altitudinal gradient of 300–1500 m above sea level in the Fuling watershed of the Three Gorges Reservoir area, China. The analysis was conducted using Illumina MiSeq high-throughput sequencing and bioinformatics analyses. Through correlation analysis with ecological factors, the altitude distribution pattern and driving factors of soil microbial diversity in the mountainous and hilly region of Chongqing were explored. According to the results, the richness and diversity of rhizosphere soil bacteria increased with altitude, while fungi were the richest and most diverse at an altitude of 900 m. The composition of the microbial community differed among different altitudes. Actinobacteria, Proteobacteria, Acidobacteriota, Chloroflexi, Bacteroidota, Ascomycota, unclassified_k_Fungi, Basidiomycota, and Mortierellomycota dominated the microbial community in rhizosphere soil. Correlation analysis showed that the distribution of rhizosphere soil microbial communities correlated with soil ecological factors at different altitudes. Moisture, pH, total nitrogen, total potassium, available potassium, urease, and catalase were significantly positively correlated with rhizosphere soil bacterial α-diversity, while their correlations with fungi were not significant. Variation partition analysis showed that the combined effects of soil physical and chemical factors, enzyme activity, and microbial quantity regulated bacterial community structure and composition. Their combined contributions (19.21%) were lower than the individual effects of soil physical and chemical factors (48.49%), enzyme activity (53.24%), and microbial quantity (60.38%). The effects of ecological factors on fungal communities differed: While the soil physical and chemical factors (44.43%) alone had a clear effect on fungal community structures, their combined contributions had no apparent effect. The results of this study not only contribute to a deeper understanding of the impact mechanism of altitude gradient on the diversity of rhizosphere soil microbial communities, but also provide a scientific basis for the protection and management of mountainous and hilly ecosystems. It lays a foundation for the future exploration of the relationship between microbial communities and plant–soil interactions.

Analysis of Salt Stress on Soil Microbial Community Composition and Its Correlation with Active Components in the Rhizosphere of Acanthopanax senticosus.

Salt stress can adversely affect plant seed germination, growth and development, and eventually lead to slow growth and even death of plants. The purpose of this study was to investigate the effects of different concentrations of NaCl and Na2SO4 stress on the physicochemical properties, enzyme activities, rhizosphere microbial community and seven active components (L-phenylalanine, Protocatechuic acid, Eleutheroside B, Chlorogenic acid, Caffeic acid, Eleutheroside E, Isofraxidin) of Acanthopanax senticosus rhizosphere soil. Statistical analysis was used to explore the correlation between the rhizosphere ecological factors of Acanthopanax senticosus and its active components. Compared with Acanthopanax senticosus under NaCl stress, Na2SO4 generally had a greater effect on Acanthopanax senticosus, which reduced the richness of fungi in rhizosphere soil and adversely affected the content of multiple active components. Pearson analysis showed that pH, organic matter, ammonium nitrogen, available phosphorus, available potassium, catalase and urease were significantly correlated with active components such as Caffeic acid and Isofraxidin. There were 11 known bacterial genera, 12 unknown bacterial genera, 9 known fungal genera and 1 unknown fungal genus significantly associated with the active ingredient. Salt stress had great changes in the physicochemical properties, enzyme activities and microorganisms of the rhizosphere soil of Acanthopanax senticosus. In conclusion, different types and concentrations of salts had different effects on Acanthopanax senticosus, and the active components of Acanthopanax senticosus were regulated by rhizosphere soil ecological factors.

Identification of geographic, climatic, and soil factors dominating Stevia rebaudiana yield and quality

Raising crop yields and quality through plant ecological research has become an important approach to sustainably improving crop products. Stevia rebaudiana is widely introduced and cultivated around the world because of the continuous increase in demand for steviol glycosides. When selecting regions or plots suitable for high-yield and high-quality cultivation, it is necessary to understand the main ecological factors that contribute to the formation of S. rebaudiana yield and quality. In this study, sampling plots from different geographic and climatic regions in Xinjiang and Jiangsu were selected for S. rebaudiana cultivation. The geographic, climatic and soil ecological factors were analyzed based on a PLSR (partial least squares regression) model to discover the potentially influential factors in the yield and quality formation of the crop. The results suggest that not all geographic and climatic ecological factors contributed to yield formation; however, these factors, such as latitude, altitude and annual sunshine duration, had high or moderate influences on the concentration of each steviol glycoside and total steviol glycoside. Soil organic matter (OM), total potassium (TK), available potassium (AK), zinc (Zn), and catalase (CAT) had high or moderate effects on the concentrations of each steviol glycoside and total steviol glycoside. However, the other soil factors showed variability in the extent to which they drove the steviol glycosides. The study contributes to a more profound understanding of the ecological driving mechanisms of S. rebaudiana yield and quality formation. The yield or steviol glycoside concentrations of sweetleaf may be improved by modifying certain key ecological factors.

Decay of fallen wood and elevation affects soil fungal community assembly and indirectly controls community diversity

Fallen wood has a pivotal role in the forest ecosystem and acts as an important intermediary for material cycling and energy flow between vegetation and soil. A keystone of the forest ecosystem is the soil fungal community which performs a crucial role in regulating the internal functions of the system. Nonetheless, the characteristics of soil fungal community diversity and the process of community assembly beneath fallen wood remain unclear. Here We investigated two subtropical forests at different elevations, and selected three fallen wood of different decay classes and a control soil without fallen wood in each stand. The soil underneath the fallen wood was collected for analysis to explore the effects of decay on soil fungal diversity and community assembly processes. The 18S rRNA amplicon sequencing was used to determine fungal diversity and calculate normalized stochasticity ratios (NST), whilst the underlying soil ecological factors were measured to predict the possible drivers of fungal diversity along with the driving mechanisms. The results revealed that elevation and fallen wood decay had a significant interactive effect on soil fungal alpha diversity as well as beta diversity. Outcomes of tNST (taxonomic Normalized Stochasticity Ratio) suggested that fallen wood decay at high-elevation made stochastic processes progressively more important in the assembly of soil fungal communities, while the opposite occurred at low-elevation, yet the results calculated by the pNST (Phylogenetic Normalized Stochasticity) method tended to indicate a predominance of stochastic processes in both two elevations. Fungal diversity was strongly positively correlated with NST values, but soil ecological factors were only strongly associated with NST values. The partial least squares path model (PLS-PM) further indicated that elevation and fallen wood decay did not directly regulate changes in fungal community diversity, but indirectly controlled fungal community assembly processes by affecting soil ecological factors, anon varied fungal diversity as well as community structure. This work will generate fresh insight into the patterns of soil fungal diversity and community assembly processes in forest ecosystems.

Simulating Crop Productivity in a Triple Rotation in the Semi-arid Area of the Aral Sea Basin

Farmers face increased risks and vulnerability to the effects of climate change and land degradation on crop production due to the lack of information and impact assessment. This is especially true in the Khorezm, an irrigated agricultural region near the Aral Sea Basin (Uzbekistan) which represents eight million of irrigated land in Central Asia. Water scarcity requires research and introduction of alternative crops into a common winter wheat–cotton rotation. Mung bean (Vigna radiata) is considered as a drought-tolerant crop that could be implemented in Khorezm and other similar drought prone areas. The main objective of this study was modeling the triple rotation sequenced the winter wheat (WW), summer mung bean (MB) and cotton (C) as a single cropping system. Specific objectives were to (1) update the parameterization of the irrigated winter wheat and cotton modules in CropSyst to identify the key variables impacting the triple rotation (WW–MB–C) on overall crop yield; (2) to parameterize and validate the developed (CropSyst-based) model using controlled triple rotation data and (3) carry out scenario analyses to capture the influence of soil fertility levels and irrigation water shortage on crops growth, development and yields. The results revealed, for the first time, the impact of different soil-ecological factors such as high soil fertility (HSF) and low soil fertility (LSF) varying levels of irrigation water availability on crops in the triple crop rotation. Compared to LSF simulated yields of winter wheat and cotton under HSF were increased with 0.58 Mg ha−1 for WW grain and 0.21 Mg ha−1 for cotton while mung bean grain yields were not affected by different soil fertility levels. Scenario analyses showed the possibility of reduced (by 20%) irrigation for triple crop without the effect on yield. However, compared to full irrigation scenario, reduction of irrigation for 40 and 60% could decrease the rotation crops yields up to 33% and 40%, respectively. The developed model could be useful to increase the understanding of the nexus of food, energy and water in Khorezm and comparable regions of Central Asia, and to inform decision-making about sustainable use of available water resources.

Soil nutrient heterogeneity affects the accumulation and transfer of cadmium in Bermuda grass (Cynodon dactylon (L.) pers.)

There have been no studies demonstrating the correlation between soil nutrient heterogeneity and cadmium (Cd) absorption of Bermudagrass. In this study, a pot experiment was carried out to study the correlation between them. The purpose is to find soil nutrient factors which are conducive to improving the Cd absorption and translocation. The eighth group had the largest total number of surviving plants, the highest Fv/Fo value (3.24) and the best growth characteristics. The fifth group had the lowest total number of surviving plants, Fv/Fo (2.47) and the worst growth. The Cd content of the fifth group (36.11 mg kg−1) was close to the eighth group (35.72 mg kg−1), but the two groups had significant differences in plant height, stem node length and stem node number (P < 0.05). The eighth group showed the highest contents of nitrate nitrogen (NO3−-N), available potassium and urease activity. The fifth group showed the lowest NO3−-N content, but the highest ammonium nitrogen (NH4+-N) and available phosphorus content. There was significant difference of the Cd bioconcentration factors (BCF) and translocation factor (TCF) between the fifth and the eighth group although they had the similar total soil Cd content (P < 0.05). The fifth group had the highest BCF and TCF. RDA analysis indicated the BCF and TCF were positively correlated with soil NH4+-N and available phosphorus and negatively correlated with soil NO3−-N. The results demonstrated that soil NH4+-N and available phosphorus were important soil ecological factors to enhance Cd absorption and translocation of bermudagrass.

Ефективність препарату «Реаком» на чорноземі звичайному за вирощування пшениці озимої

The article describes the importance of using micronutrients in the dry climate of the Southern Steppe of Ukraine on degraded soils under conditions of atmospheric pollution, violation of traditional schemes of crop rotation of crops and deficiency of organic fertilizers. The main purpose of the study, taking into account that the fertilization was carried out in a single scheme, both in terms of norms and technology, was to investigate the influence of soil ecological factors on the yield of winter wheat against the background of differentiation of the extracorporeal fertilization with the trace elements of Reakom (Zn, Cu, B, Mo, Co, P 2 O 5 , K 2 O) in a dose of 2.5 l/ha and 5 l/ha. The research was carried out on chernozem in the usual low-humus and its eroded abnormalities: weak and medium-sized, which marked the rise of carbonates due to some blurring of the upper accumulative genetic horizon and deterioration of qualitative soil fertility indices. The yield of winter wheat on chernozem was almost 1.17% higher than that of 2.5 l/ha, compared to control, whereas there was no effect on the washed offs. For application of 5l/ha Reakom at discarded crop yields increased to 13.8% on medium-chernozem. Effectiveness of the drug for foliar application of winter wheat in arid conditions on the abovementioned soil abnormalities is described by the regression equation, the use of which will allow the efficient allocation of funds when planning purchases of trace elements of trace elements.

Soil-ecological conditions of Korean pine growth in its natural area and upon introduction in the European part of Russia

Socioeconomic expediency and soil-ecological potential of introducing Korean pine (Pinus koraiensis) in the forest zone of the European part of Russia are discussed. The specificity of soil-ecological conditions and technologies applied for growing Korean pine in some tree farms in the Far East region and in the European part of Russia are compared. The main soil-ecological factors and optimum soil parameters for the successful development of Korean pine in its natural and introduction areas are determined. It is shown that development of Korean pine seedlings on well-drained soils depends on the contents of potassium, humus, and physical clay in the soils. The seedlings gain maximum size upon their growing on soddypodzolic soils (Retisols). The analysis of mineral nutrition of pine seedlings of different ages, soil conditions, and seasonal growth phases shows that the contents of potassium and some microelements play the leading role in the successful growth of introduced Korean pine.

Influences of Conservation Tillage Practices on Farmland Soil Ecological Factors and Productive Benefits in Dryland Region with Triple Cropping System

针对我国西南地区旱作农田土层浅薄、水土流失严重、季节性干旱多发等问题,以常规平作（T）、垄作（R）、平作＋秸秆覆盖（TS）、垄作＋秸秆覆盖（RS）、平作＋秸秆覆盖＋腐熟剂（TSD）、垄作＋秸秆覆盖＋腐熟剂（RSD）6种措施作为处理,连续2年进行大田对比试验,研究不同保护性耕作措施对西南＂旱三熟＂种植区农田土壤生态要素、产量和水分利用效率的影响。结果表明,保护性耕作措施可以有效地改善土壤有机质和养分状况,且对酸性土壤有一定的改良作用,其中有秸秆覆盖的4个处理显著增加了土壤有机质、全氮、全钾、碱解氮含量;可改善土壤水分状况,增强作物的抗旱节水能力,各处理0~80 cm土层2年平均贮水量排序为：RSD（258.82 mm）〉TSD（252.40 mm）〉RS（250.19mm）〉TS（246.66 mm）〉R（239.19 mm）〉T（235.87 mm）;可降低7月份表层土壤温度,缓解夏季高温对玉米后期生长发育造成的伤害,其中有秸秆覆盖的4个处理对5 cm和10 cm土层温度有显著降低效应;可抑制杂草生长,具有良好的控草效应,其中TS、RS、TSD、RSD处理的杂草高度、密度和生物量均比T和R有极显著下降;可促进蚯蚓的繁殖和生长,使农田生态环境得到明显改善。总体来看,秸秆覆盖措施可以改善土壤肥力,并具有增加土壤贮水、调节土壤温度、控制农田杂草和促进蚯蚓生长的作用,垄作和腐熟剂在增加土壤贮水方面有明显效果。保护性耕作模式显著提高了作物的产量和水分利用效率,增加了经济收益。2年系统平均产量和水分利用效率排序为：RSD〉RS〉TSD〉TS〉R〉T（CK）,总产值和纯收入排序为RS〉RSD〉TSD〉R〉TS〉T（CK）。在各处理中以RSD、RS两种模式的综合效果最好,在西南＂旱三熟＂种植区具有很好的推广前景。

ECOLOGICAL ASSESSMENT OF LAND COVER OF GANIKH VALLEY

Abstract. In the article, the results of the research studies conducted in the direction of the study of the soil cover and ecological assessment of the Ganikh valley were interpreted. Four ecological groups were divided according to the spread characteristics of land cover structures in the Ganikh valley, as well as with the help of soil maps and the main soil-ecological factors, and these were considered as the main criteria in the ecological assessment of the area. Appraisal scores were calculated according to the main diagnostic indicators of soils. Four main types of land cover structures were identified and their average appraisal scores were found. Keywords: elementary soil areas, soil cover structure, appraisal scores, relief plasticity method

Dynamics of Microbial Population in Soil as Influenced by Simazine and Ecological Factors

Simazine, even at normal rates of application, showed toxicity to bacteria fungi. It was less toxic to actinomycetes, since toxicity up to 20 ppm of the herbicide was not observed. On the contrary, the normal rate of simazine stimulated both Azotobacter and actinomycetes population. The interaction of simazine with soil ecological factors, such as temperature, moisture, pH, and organic matter, affected soil microbial population differently. Simazine was relatively less toxic to bacteria under acidic and alkaline conditions of soil; they were not affected at 15 degrees C. Actinomycetes were comparatively not adversely affected even with 200 ppm of simazine under high soil moisture regime. The stimulatory effect of simazine on Azotobacter was also confirmed under different ecological conditions. The incorporation of 2 per cent of organic matter in soil mitigated the toxicity of simazine in respect to soil fungi. Simazine also appeared to be less toxic to soil fungi at lower temperatures, under acidic and alkaline conditions of soil, as well as under high moisture regime.