Key Soil Factors Research Articles

Mangrove afforestation as an ecological control of invasive Spartina alterniflora affects rhizosphere soil physicochemical properties and bacterial community in a subtropical tidal estuarine wetland

Background The planting of mangroves is extensively used to control the invasive plant Spartina alterniflora in coastal wetlands. Different plant species release diverse sets of small organic compounds that affect rhizosphere conditions and support high levels of microbial activity. The root-associated microbial community is crucial for plant health and soil nutrient cycling, and for maintaining the stability of the wetland ecosystem. Methods High-throughput sequencing was used to assess the structure and function of the soil bacterial communities in mudflat soil and in the rhizosphere soils of S. alterniflora, mangroves, and native plants in the Oujiang estuarine wetland, China. A distance-based redundancy analysis (based on Bray–Curtis metrics) was used to identify key soil factors driving bacterial community structure. Results S. alterniflora invasion and subsequent mangrove afforestation led to the formation of distinct bacterial communities. The main soil factors driving the structure of bacterial communities were electrical conductivity (EC), available potassium (AK), available phosphorus (AP), and organic matter (OM). S. alterniflora obviously increased EC, OM, available nitrogen (AN), and NO3−-N contents, and consequently attracted copiotrophic Bacteroidates to conduct invasion in the coastal areas. Mangroves, especially Kandelia obovata, were suitable pioneer species for restoration and recruited beneficial Desulfobacterota and Bacilli to the rhizosphere. These conditions ultimately increased the contents of AP, available sulfur (AS), and AN in soil. The native plant species Carex scabrifolia and Suaeda glauca affected coastal saline soil primarily by decreasing the EC, rather than by increasing nutrient contents. The predicted functions of bacterial communities in rhizosphere soils were related to active catabolism, whereas those of the bacterial community in mudflat soil were related to synthesis and resistance to environmental factors. Conclusions Ecological restoration using K. obovata has effectively improved a degraded coastal wetland mainly through increasing phosphorus availability and promoting the succession of the microbial community.

Regeneration costs of topsoil fertility: An exergy indicator of agricultural impacts

In recent years, heightened environmental concerns linked to agriculture have surged, with soil degradation standing out as a global issue. However, prevailing sustainability assessment methodologies in agriculture often overlook soil systems due to their intricate nature. This study aims to develop a methodology for evaluating soil degradation in agricultural practices using exergy regeneration costs. These costs determine the exergy required to restore soil fertility to pre-harvest levels. The methodology covers key soil factors like nutrients, organic matter, and prevalent issues like salinity, acidification, and erosion. For each of these factors, exergy regeneration costs are determined based on the energy needed to execute an optimal process for reverting the soil to its original or ideal state. The methodology has been applied to data from agricultural trials, showing that the calculated soil replacement cost is significantly higher compared to one of the most energy-demanding processes in agriculture, the use of urea. This demonstrates that agricultural soil degradation needs to be quantified for a correct evaluation of agricultural practices and their sustainability.

Appropriate Application of Organic Fertilizer Can Effectively Improve Soil Environment and Increase Maize Yield in Loess Plateau

Fertilization has a significant impact on soil nutrients and microbiological properties, which, in turn, affect crop yield. However, the specific effects of organic and inorganic fertilizers on soil fertility and microbial characteristics in maize fields, as well as the key soil factors influencing changes in crop yield, remain largely unknown. A study was conducted over two years (2021–2022) to investigate the impact of various nitrogen fertilization rates and types on maize yield and soil properties in the Loess Plateau. Field experiments with five nitrogen levels (60, 90, 120, 150, and 180 kg N ha−1) and two fertilizer types (chemical and organic) were conducted. The optimal yield was achieved with 150 kg N ha−1, significantly surpassing that of other treatments by 4.5−45.7%. Compared with the organic fertilizers, the chemical fertilizers increased soil salt and catalase levels, with soil nitrate and ammonium content being higher at the jointing stage but lower at maturity. Organic fertilization improved soil potassium, organic matter, urease and phosphatase activities, and microbial populations. Yield correlated with several soil indicators, including salt content, nitrate, available potassium, and enzyme activities. Notably, soil nitrate also correlated with actinomyces quantity. A principal component analysis showed that the organic fertilizer was more beneficial to soil health than the chemical fertilizer. Consequently, this study recommends 150 kg N ha−1 of organic fertilizer for sustainable maize farming and soil health in China’s northwest arid region, providing a theoretical framework for agricultural practices.

Vertical differences in carbon metabolic diversity and dominant flora of soil bacterial communities in farmlands

The carbon cycle in soil is significantly influenced by soil microbes. To investigate the vertical distribution of the dominant groups in agricultural soil and the carbon metabolic diversity of soil bacteria, 45 soil samples from the 0 ~ 50 cm soil layer in Hunan tobacco–rice multiple cropping farmland were collected in November 2017, and the carbon diversity of the soil bacterial community, bacterial community composition and soil physical and chemical properties were determined. The results showed that the carbon metabolic capabilities and functional diversity of the soil bacterial community decreased with depth. The three most widely used carbon sources for soil bacteria were carbohydrates, amino acids, and polymers. The dominant bacterial groups in surface soil (such as Chloroflexi, Acidobacteriota, and Bacteroidota) were significantly positively correlated with the carbon metabolism intensity. The alkali-hydrolysable nitrogen content, soil bulk density and carbon–nitrogen ratio were the key soil factors driving the differences in carbon metabolism of the soil bacterial communities in the different soil layers.

Identification of soil properties influencing primary productivity of fish ponds under red and lateritic soil zones

Aim: The present study aimed to identify the key soil factors influencing the primary productivity of water in the fish ponds situated under low productive red and lateritic soil zones. Methodology: General properties of fish pond soils (n=42) from different red and lateritic soil zones of West Bengal, India were determined along with the gross primary productivity (GPP) values of corresponding pond waters. All the soil properties were correlated with GPP values and the soil factors which were significantly correlated with GPP of pond water were further used for step down regression analysis with regard to GPP.This helped to develop a minimum data set of the key soil factors which showed maximum influence on GPP. The efficiency of the regression equation, generated with the critical soil parameters, in predicting the GPP values of other ponds was also assessed through a study on the variations in calculated and on-farm GPP values of eight fish ponds. Results: Among all the studied soil properties, pH and availability of three major nutrients viz. N, P and K were observed to contribute 84.15% variations in gross production of primary fish food organisms in these pond environment. Of these 4 soil properties, again, pH and available P values of the pond soils appeared to be more important. A regression equation was also developed to predict the GPP of such pond water using soil pH and available P values only. This equation showed a precision range of 83.0 to 99.7% and was found to be statistically at par with the GPP values observed under actual pond condition. Interpretation: High efficiency in predictability of pond GPP values using the minimum data set of two key soil factors viz. soil pH and available P indicates that proper management of these productivity attributing soil properties will be particularly helpful to improve the primary productivity levels of the predominantly low yielding fish ponds under the red and lateritic soil zones. Key words: Fish ponds, Minimum data set, Productivity attributes, Red and lateritic soil zones, Soil factors

PH-Related Changes in Soil Bacterial Communities in the Sanjiang Plain, Northeast China.

Soil bacteria are crucial components of terrestrial ecosystems, playing an important role in soil biogeochemical cycles. Although bacterial community diversity and composition are regulated by many abiotic and biotic factors, how soil physiochemical properties impact the soil bacteria community diversity and composition in wetland ecosystems remains largely unknown. In this study, we used high-throughput sequencing technology to investigate the diversity and composition of a soil bacterial community, as well as used the structural equation modeling (SEM) method to investigate the relationships of the soil's physicochemical properties (i.e., soil pH, soil organic carbon (SOC), total nitrogen (TN), ammonium nitrogen (NH4+N), electrical conductivity (EC) and nitrate nitrogen (NO3-N)), and soil bacterial community structures in three typical wetland sites in the Sanjiang Plain wetland. Our results showed that the soil physicochemical properties significantly changed the α and β-diversity of the soil bacteria communities, e.g., soil TN, NH4+N, NO3-N, and SOC were the main soil factors affecting the soil bacterial α-diversity. The soil TN and pH were the key soil factors affecting the soil bacterial community. Our results suggest that changes in soil pH indirectly affect soil bacterial communities by altering the soil nitrogenous nutrient content.

Organic amendment substitution improves the sustainability of wheat fields changed from cotton and vegetable fields

Long-term excessive use of chemical fertilizers and continuous cropping in vegetable and cotton production lead to a decline in farmland soil quality and crop productivity, endangering sustainable agricultural development. Organic amendment substitution (OAS) or farmland use change or can potentially enhance soil quality and crop yield. However, it remains unclear whether their combined application can improve the sustainability of wheat fields when changing from cotton and vegetable fields. In this study, continuous cropping cotton and vegetable fields were changed to wheat fields (C-W and V-W), and then field fertilization experiments (non-fertilization, NF; chemical fertilizer alone, CF; chemical fertilizer reduced by 20%, RF; and organic amendment substituted 20% of inorganic nitrogen, OAS) were conducted for three years (2018–2020) to explore their effects on wheat productivity and soil quality. The findings revealed that the combined farmland use change and fertilization improved soil quality in wheat fields compared to pre-change cotton and vegetable fields. OAS improved soil quality index (SQI-TDS by 0.36–0.82 and 0.32–0.82; SQI-IDS by 0.37–0.90 and 0.40–0.88) by improving soil properties and increasing microbial diversity compared to NF, CF and RF in C-W and V-W. Meanwhile, OAS increased nutrient use efficiency, crop productivity index (CPI, by 13.69%−72.46% and 8.52%−41.45%) and the sustainability index (SI, by 14.14%−49.35% and 12.56%−40.00%). Moreover, microbial biomass carbon and nitrogen (MBC and MBN), pH, available nitrogen (AN), soil organic carbon (SOC) and ACE index were key soil factors affecting yield. These indicators can be used to construct important dataset to simplify soil quality evaluation systems. Overall, the present study revealed the mechanism by which OAS improved wheat field sustainability by increasing wheat productivity and soil quality after farmland use changes, contributing to sustainable agricultural development. Moreover, it provides valuable reference methods and evaluation ideas for future research on farmland soil quality and sustainability evaluation.

Assembly, diversity and coexistence of bacteria communities in various rhizocompartment niches in Sorghum Cultivars

Root-associated microbial communities play a vital role in plant health, but the assembly processes in sorghum and associated soil factors remain unclear. We conducted 16S rDNA sequencing on bulk soils and rhizocompartments (rhizosphere, rhizoplane, and endosphere) of three sorghum cultivars. Physicochemical properties were measured in bulk and rhizosphere soils. Alpha-diversity decreased from bulk soil to endosphere, and beta-diversity showed compartmental separation. Relative abundances of 16 dominant genera varied among compartments and cultivars. Dispersal limitation increased from (17.0%) to endosphere (35.8%), with homogenous selection dominating rhizocompartment assembly (51.1%–83.0%). Certain soil factors mediated community assembly and shaped phylogenetic structures. Rhizosphere displayed the most complex network, followed by bulk soil, rhizoplane, and endosphere. Differentially abundant taxa were more important in maintaining network stability and connectivity in the endosphere (47.0%–68.4%) compared to the other rhizocompartments. This study provides insights into the factors influencing the assembly of root-associated bacterial communities in sorghum, highlighting the roles of compartment niches, sorghum cultivars, and soil properties. These findings contribute to our understanding of plant-microbe interactions and have implications for agricultural management and ecological restoration efforts. Furthermore, the identification of key soil factors that mediate community assembly processes and shape phylogenetic structures offers potential targets for manipulating microbial communities in agricultural systems, leading to improved plant health and productivity.

Mechanism of microbial regulation on methane metabolism in saline–alkali soils based on metagenomics analysis

Saline–alkali soils constitute a globally important carbon pool that plays a critical role in soil carbon dioxide (CO2) and methane (CH4) fluxes. However, the relative importance of microorganisms in the regulation of CH4 emissions under elevated salinity remains unclear. Here, we report the composition of CH4 production and oxidation microbial communities under five different salinity levels in the Yellow River Delta, China. This study also obtained the gene number of microbial CH4 metabolism via testing the soil metagenomes, and further investigated the key soil factors to determine the regulation mechanism. Spearman correlation analysis showed that the soil electrical conductivity, salt content, and Na+, and SO42− concentrations showed significantly negative correlations with the CO2 and CH4 emission rates, while the NO2−-N concentration and NO2−/NO3− ratio showed significantly positive correlations with the CO2 and CH4 emission rates. Metabolic pathway analysis showed that the mcrA gene for CH4 production was highest in low–salinity soils. By contrast, the relative abundances of the fwdA, ftr, mch, and mer genes related to the CO2 pathway increased significantly with rising salinity. Regarding CH4 oxidation processes, the relative abundances of the pmoA, mmoB, and mdh1 genes transferred from CH4 to formaldehyde decreased significantly from the control to the extreme–salinity plot. The greater abundance and rapid increase of methanotrophic bacteria compared with the lower abundance and slow increase in methanogenic archaea communities in saline–alkali soils may have increased CH4 oxidation and reduced CH4 production in this study. Only CO2 emissions positively affected CH4 emissions from low– to medium–salinity soils, while the diversities of CH4 production and oxidation jointly influenced CH4 emissions from medium– to extreme–salinity plots. Hence, future investigations will also explore more metabolic pathways for CH4 emissions from different types of saline–alkali lands and combine the key soil enzymes and regulated biotic or abiotic factors to enrich the CH4 metabolism pathway in saline–alkali soils.

Inconsistent responses of soil bacterial and fungal community's diversity and network to magnesium fertilization in tea (Camellia sinensis) plantation soils

Soil microbes are important drivers of nutrient cycling that regulate plant growth and productivity. Yet, a holistic understanding of the effect of magnesium (Mg) fertilizer on the soil microbial community is still poorly understood. Here, a four-year field experiment was conducted to investigate the impact of different rates of Mg application, including 0, 17.5, 35, 52.5, and 70 kg of MgO ha−1, on soil bacterial and fungal communities (Illumina 16S and ITS amplicon sequencing) associated with tea plantations. Results showed that Mg application significantly increased the soil pH and improved the soil acidity, carbon, and available nitrogen, calcium, and Mg contents. Hence, Mg application also significantly increased soil bacterial diversity but did not affectfungal diversity. Moreover, Mg fertilization increased the relative abundance of beneficial bacterial genera belonging to nitrogen fixation and phosphorus mineralizing groups, such as Gemmatimonas, Rhizomicrobium and Sphingomonas. In addition, the Mg fertilization decreased the relative abundance of some pathogen fungi, such as Pestalotiopsis, Chaetomium, and Coniosporium. Network analysis indicated that the Mg application increased the complexity of the bacterial network by enhancing node numbers and connectivity links, while for fungal networks, the low rate of Mg fertilizer increased total nodes and edges. However, the higher amount of Mg fertilizer decreased the complexity of the fungal network. Correlation analysis between soil properties and microbial communities showed that pH, total carbon and nitrogen, available carbon, and exchangeable Mg were the key soil factors that significantly influenced the microbial community structure. These findings suggest that Mg fertilization could increase soil microbial diversity, alter the microbial structure and improve the microbial network structure of the tea plantation soils. These findings could help to improve soil health, sustainability, and crop productivity. Therefore, Mg fertilization can be considered a viable strategy for improving the health and productivity of tea plantation soils.

Changes of Key Soil Factors, Biochemistry and Bacterial Species Composition during Seasons in the Rhizosphere and Roots of Codonopsis pilosula (tangshen)

Codonopsis pilosula is a medicinal and edible herb with a rich nutritional value. In Gansu Province, China, its production quality and yield differ during the four seasons. Here, we investigated the differences in the microfloral composition and metabolic functions in the rhizospheric soil and roots of C. pilosula during the four seasons, and we also analyzed their dynamic and synergistic effects on C. pilosula growth and carbohydrate content change. The C. pilosula samples were analyzed for plant physiology, microfloral composition and metabolic functions in the rhizospheric soil and roots using high-throughput sequencing technology. Environmental indices including soil physiochemistry and meteorological conditions were also determined by the coupled chromatography–spectroscopy technique. The results revealed that the C. pilosula growth was affected by temperature, precipitation and light intensity, with the bacterial structures and functions of the soil and root samples showing obvious seasonal changes. Due to the diversity of microbial composition and community metabolic function, and the synergistic effect of microbial and environmental factors, there are significant differences in stress resistance, physiological status and metabolites of C. pilosula in different seasons. Furthermore, the change in seasons was significantly correlated with the quality and yield of C. pilosula. This study provides a scientific basis for soil improvement and the refinement of local Radix C. pilosula cultivation methods.

Plant Traits Variably Respond to Plant–Soil Interactions during Secondary Succession on the Loess Plateau

Knowledge of plant photosynthesis, biomass, and stress resistance could contribute to exploring the growth and restoration of vegetation. However, the response of these plant traits to plant–soil interactions at different successional stages remains poorly understood, which limits the understanding of secondary succession. A greenhouse experiment was designed to test the effects of rhizosphere soils collected from early- (EarlySoil), mid- (MidSoil), and late-successional (LateSoil) plant communities on plant traits of early-, mid-, and late-successional species (EarlySp, MidSp, and LateSp, respectively). We found that plant traits reacted in a specific direction to plant–soil interactions at different successional stages. Specifically, compared with treatments of plants growing in their own soil, the net photosynthetic rate and single-photon avalanche diode significantly increased in LateSp–EarlySoil (treatment of plants growing in soil) (20%–31%) and LateSp–MidSoil (10%–18%); the maximum quantum efficiency of photosystem II increased in MidSp–EarlySoil (1%) and LateSp–MidSoil (4%); belowground soluble sugar concentrations decreased in LateSp–EarlySoil (33%) and LateSp–MidSoil (45%); leaf, stem, and root biomass increased in MidSp–EarlySoil (76%–123%), LateSp–EarlySoil (180%–342%), and LateSp–MidSoil (83%–137%), and in turn they decreased in EarlySp–MidSoil (40%–73%) and EarlySp–LateSoil (53%–67%). The results indicated that soil conditioned by pre-successional species (early- or mid-successional species) would be conducive to plant functional traits of subsequent successional species (mid- or late-successional species). Constrained redundancy analysis and path analysis suggested that water-soluble ammonium N, total N, and available N concentrations were key soil factors affecting early-, mid-, and late-successional species, respectively. Our findings confirm the directionality of succession and provide new information for plant population dynamics during secondary succession.

Soil physicochemical characteristics and leaf nutrient contents on banana farms of North Queensland, Australia

Context Banana production in Australia is in three primary sub-regions within tropical North Queensland and the industry faces a variety of challenges including costs of production, disease and pests, and environmental impacts. The range of soil characteristics and banana leaf nutrient status on banana farms has not previously been systematically described. This knowledge gap makes it difficult to adapt research, management recommendations, and regulations to the needs of the three primary growing sub-regions. Aims In this work, we aimed to identify key soil factors that differentiate growing sub-regions, and provide context for future research and industry regulation. Methods We characterised soil and banana leaf samples from 28 banana farms on soil types accounting for >85% of Australia’s banana production. Key results and conclusions Variation in soil properties and leaf nutrient concentrations were driven largely by site- (principal component 1 in both cases) and management-related variables (principal component 2 in both cases). Management-related foliar nutrient concentrations did not differ between regions despite differences in the associated soil variables. The most important site characteristics appeared to be soil parent material and climate. The Mareeba sub-region has basaltic soils, low rainfall and temperature, whereas the other two sub-regions are hotter, wetter and have a variety of soil parent materials. Leaf nitrogen concentrations were mostly below the regulated limit for additional nitrogen fertiliser application. Implications Our findings can facilitate sub-region-specific site selection for research, extension, and monitoring and more targeted regulation of banana production- and environment-related issues.

The importance of incorporating geology, soil, and landscape knowledge in freshwater farm planning in Aotearoa New Zealand

Over half of Aotearoa New Zealand’s (NZ’s) land area is under agriculture or forestry production. Long term monitoring has shown declines in freshwater quality in regions with the most intensive agriculture. The New Zealand government has historically focused on reducing the impact of agriculture on water quality through its Resource Management Act 1991. Lack of improvement in freshwater quality has resulted in the 2020 Essential Freshwater package of reforms which will require all pastoral farms >20 ha in size and all arable farms > 5 ha in size to develop a Freshwater Farm Plan (FFP) by a certified Freshwater Farm Planner. As far as we are aware, New Zealand is the first country in the world to mandate compulsory FFPs. This paper describes the key geological, soil, and landscape factors that need to be considered in an FFP for it to be successful in meeting the 2020 Essential Freshwater objectives. We argue that a greater emphasis should be placed on understanding a farm’s natural resources, as they provide the physical interface between the farming system and both the freshwater and atmospheric ecosystems. Documenting our learning in this area could assist other countries considering Freshwater Farm Planning as a strategy to reduce the impact of agriculture on freshwater quality.

Characterization of Soil-Plant Leaf Nutrient Elements and Key Factors Affecting Mangoes in Karst Areas of Southwest China

Baise city is one of the largest producers of mangoes, with this agricultural industry located in the karst region of Southwest China. However, calcium-rich and alkaline soils, severe soil fragmentation, and poor water and fertilizer retention capacity contribute to low mango yields and are key issues that limit the development of the mango industry in karst areas. Our study objectives were to identify the soil factors that limit mango growth and yield in the karst region of Southwest China, and to determine how these growth- and production-limiting conditions vary between landscape positions. This study analyzed the differences in soil nutrient and element contents in mango leaves, and used a Random Forest algorithm to calculate the eigenvalues of the mango leaf and soil elemental indices in the different geomorphic parts (slopes, transition zone, passes, high-yielding depressions, and low-yielding depressions) of the karst peak-cluster depressions. The key factors affecting the mango leaves and soil were screened based on the diagnostic results and the eigenvalues. The results showed that for the elemental contents of Fe, Mg, Ca, and Mn in the mango leaves in the different geomorphic parts of the karst, the peak-cluster depressions were generally deficient and varied significantly. The contents of available B (AB), soil organic matter (SOM), pH, total nitrogen, available Fe, available Mn, alkaline hydrolysis nitrogen, exchangeable Ca (Caex), exchangeable Mg, and other indices in the soils differed significantly, and AB, available Zn, and available K (AK) showed low or very low content levels. In addition, the key soil factors limiting mango yield in the karst areas were AB, fulvic acid, SOM, Fe, Mn, Caex, soil water, and AK; and the key mango leaf factors were Ca, Mn, Fe, Zn, and Mg. Consequently, the characteristics of soil water content, pH, and soil organic matter may be the main drivers affecting the differences in the mango yield and the elemental characteristics. These findings suggest that the addition of organic fertilizer could improve the quality and yield of mangoes in karst areas.

Responses and comprehensive evaluation of growth characteristics of ephemeral plants in the desert–oasis ecotone to soil types

The ecological environment of the Gurbantünggüt desert–oasis ecotone is extremely fragile. Ephemeral plants are an important part of the ecosystem and play an essential role in maintaining the ecological stability of the ecotone. However, few studies have focused on the growth, soil quality and system sustainability of ephemeral plants in different soils. This study was based on two typical soil types (grey desert soil, GS; aeolian soil, AS) in the aforementioned ecotone, considered four ephemeral plants (Tetracme recurvata, TR; Tetracme contorta, TC; Malcolmia scorpioides, MS; Isatis violascens, IV) as the research object, analysed plant characteristics and soil properties, and comprehensively evaluated the ephemeral plant system by analysing the soil quality index (SQI) and sustainability index (SI). The results showed that there were significant differences in biomass and nutrient accumulation between different ephemeral plants, which were significantly affected by soil types. In the two examined soils (GS and AS), the contents of nutrients and microbial carbon (MBC) and nitrogen (MBN) in the rhizosphere soil were higher than those in the bare soil (BS), and there were significant differences among different species. The key soil factors related to total biomass in GS and AS were also different. The SQI of ephemeral plants was significantly higher than that of the BS, and varied with soil types and plant species. The species with the highest SQI of the key factor data set in GS and AS were IV and TR, respectively. The SI analysis indicated that IV in GS and MS and IV in AS were sustainable, and the plant properties can be better used to assess the sustainability of ephemeral plant systems. In conclusion, ephemeral plants improved the soil quality and system sustainability of the study ecotone. Further, the growth of ephemeral plant and rhizosphere soil properties vary with plant species and soil types; thus, selecting suitable species for large-scale planting in different soil types is of great significance for improving the ecological stability of the ecotone.

Clay Content Played a Key Role Governing Sorption of Ciprofloxacin in Soil

Ciprofloxacin is a broad-spectrum antibiotic of the fluoroquinolone class that is used to treat bacterial infections in both humans and animals. Antibiotics released into the environment can select for antibiotic-resistant microorganisms, which negatively affects human and animal healthcare. Understanding soil factors that govern the mobility of ciprofloxacin can facilitate the development of targeted efforts to mitigate potential negative impacts. The objectives were (1) to determine the sorption capacity of ciprofloxacin in soils under acidic conditions; and (2) to reveal relative importance of key soil factors that influence sorption of ciprofloxacin. Evaluations were conducted using 20 soil samples with diverse properties and different cultivation/vegetation history. Sorption capacity ranged from 8 to 141 g kg−1; distribution coefficient (Kd) ranged from 23 to 200 mL kg−1 soil; and soil organic carbon-water partitioning coefficient (Koc) values ranged from 54 to 2,146 mL g−1 organic carbon. Clay content and cation exchange capacity were the most significant factors that influenced sorption capacity and Kd of ciprofloxacin with r values of 0.92*** and 0.64***, respectively. Soil pH had little effect on ciprofloxacin sorption parameters with r < 0.25. pH-independent charges played a predominant role dictating sorption parameters of ciprofloxacin in soil. Cation exchange via interlayer adsorption was a primary sorption mechanism under acidic conditions. Sorption parameters were significantly correlated with organic carbon content in cultivated soils only, resulting in r values of 0.97*** (with sorption capacity) and 0.72*** (with Kd). Cultivation led to changes in the quality of soil organic matter, resulting in changes in the sorption behavior and altered mechanisms of ciprofloxacin sorption in soil. Soils are effective in restraining the mobility of ciprofloxacin through adsorption and the effectiveness increases with clay content.

Plant Adaptability and Vegetation Differentiation in the Coastal Beaches of Yellow-Bohai Sea in China.

To identify the key soil factors influencing the vegetation differentiation in the coastal tidal flats of the Yellow−Bohai Sea in China, this study investigated the corresponding relationship between the Spartina alterniflora (SA), Suaeda salsa (SS), and Phragmites australis (PA) communities and their respective soil factors with published data, and combined the ecological strategy for analysis. The results showed a corresponding relationship between community and soil factors. The SA community had a lower bulk density (BD) and higher soil total nitrogen (TN), and the SS community was the opposite, while the PA community had the lowest salinity and higher TN. BD, salinity and TN acted as the main soil factors driving vegetation differentiation, but the explained proportion of the three factors to vegetation differentiation changed by season and region. Considering that higher TN facilitates the competitors, salinity represents the environmental stresses, and BD is positively related to the frequency of perturbation in the specific habitat in the study area, SA, SS and PA could be recognized as C–S, S–R and C strategic species to some extent. It is likely that some coexistent mechanisms for invasive and local species will be developed, especially the SS community which seriously shrunk recently but served as an important habitat for waterfowls in tidal flat habitats.

Driving mechanisms of climate-plant-soil patterns on the structure and function of different grasslands along environmental gradients in Tibetan and Inner Mongolian Plateaus in China

Grassland plants contribute to carbon fixation through photosynthesis, which can in turn produce plant biomass. Previous studies have demonstrated that vegetation productivity is enhanced by improved soil nutrient status in humid environments and is influenced by climate in arid environments. However, the responses of biomass productivity to different patterns of climate-plant-soil in different natural grassland ecosystems have not been clearly and comprehensively analyzed. In this study, we systematically explore the functional patterns of different grasslands, as well as the underlying mechanisms in the response to key climatic, soil, and plant factors. The survey range covered broad environmental gradients from humid, semi-arid, to arid environments in Tibetan and Inner Mongolian Plateaus. We found that the above- and belowground biomass production gradually decreased from humid, semi-arid, to arid environments. Biomass production was sensitive to climatic factors in different environments. However, compared to soil and plant factors, climate was always the most important factor determining biomass production in all grassland types. Furthermore, biomass production was regulated mainly by climate and soil characteristics in humid environments, but by climate in arid environments. Specifically, the corresponding limiting factors of each factor largely dominated the effects of the corresponding factors on different grasslands. For instance, the climate dominated by temperature negatively influenced the soil nutrient availability and then influenced the aboveground biomass production in alpine humid grasslands. These findings enhance our understanding of the heterogeneity of mechanisms of different grasslands along broad environmental gradients, which are crucial for predicting the effects and consequences of environmental change on terrestrial ecosystem functioning.

Predicting Potential Habitat of a Plant Species with Small Populations under Climate Change: Ostryarehderiana

Ostrya rehderiana is a famous plant species with extremely small populations. With ongoing global climate change, the extremely small populations would face more uncertainties and risks, including the loss of genetic diversity and extirpation. Thus, assessing the impact of climate change on suitable habitat of O. rehderiana is particularly important for its conservation and restoration. Here, we built niche models with climate variables and soil and human footprint variables. Furthermore, new methods were applied to avoid confounding effects between climate and soil and human footprint variables to simulate the potential habitats of O. rehderiana in current and future climates. We found that the Hargreaves climatic moisture deficit, degree-days below 0 °C, chilling degree-days, and the temperature difference between mean warmest month temperature and mean coldest month temperature, or continentality, were the most important climate factors. The topsoil USDA texture classification, topsoil cation exchange capacity of (clay), and topsoil sodicity (ESP) were the key soil factors determining the suitable distribution of O. rehderiana. Compared with soil factors, human footprint has less influence on the suitable distribution of O. rehderiana. The niche range of this species was projected to expand and shift to north in the Representative Concentration Pathway (RCP) 4.5 scenario for the 2050s. Our study results could be referenced in further extremely small populations ecological restoration studies and provide the scientific strategies for the conservation and restoration of O. rehderiana.