Explore the vast range of titles available.

This study was conducted with the aim of developing a circuit system that enables the measurement of the moisture content and ion concentration with a simple circuit configuration. Our previous studies have shown that soil can be represented by an equivalent circuit of a parallel circuit of resistors and capacitors. We designed a circuit that can convert the voltage transient characteristics of the soil when a current is applied to it into a square wave and output frequency information and developed an algorithm to analyze the two types of square waves and calculate R and C. Normal operation was confirmed in the range of 10 kΩ–1 MΩ for the designed circuit, and the calculation algorithm matched within a maximum error of 5%, thus confirming the validity of the program. These successfully confirmed the changes in the water content and ionic concentration. The soil moisture content measurement succeeded in measuring a maximum error of about 10%, except at one point, and the soil ion concentration measurement succeeded in measuring a maximum error of 6.6%. A new, simple, noise-resistant moisture content and ion concentration measurement circuit system with square wave output has been realized.

We compare carbon (and hence energy) costs of the different modes of phosphorus (P) acquisition by vascular land plants. Phosphorus-acquisition modes are considered to be mechanisms of plants together with their root symbionts and structures such as cluster roots involved in mobilising or absorbing P. Phosphorus sources considered are soluble and insoluble inorganic and organic pools. Costs include operating the P-acquisition mechanisms, and resource requirements to construct and maintain them. For most modes, costs increase as the relevant soil P concentration declines. Costs can thus be divided into a component incurred irrespective of soil Pconcentration, and a component describinghowquickly costs increase as the soil P concentration declines. Differences in sensitivity of costs to soil P concentration arise mainly from how economically mycorrhizal fungal hyphae or roots that explore the soil volume are constructed, and from costs of exudates that hydrolyse or mobilise insoluble P forms. In general, modes of acquisition requiring least carbon at high soil P concentrations experience a steeper increase in costs as soil P concentrations decline. The relationships between costs and concentrations suggest some reasons why different modes coexist, and why the mixture of acquisition modes differs between sites.

Improvement of phosphorus circulation in the soil is necessary to enhance phosphorus availability to plants. Phosphorus circulation activity is an index of soil’s ability to supply soluble phosphorus from organic phosphorus in the soil solution. To understand the relationship among phosphorus circulation activity; bacterial biomass; pH; and Fe, Al, and Ca concentrations (described as mineral concentration in this paper) in agricultural soil, 232 soil samples from various agricultural fields were collected and analyzed. A weak relationship between phosphorus circulation activity and bacterial biomass was observed in all soil samples (R2 = 0.25), and this relationship became significantly stronger at near-neutral pH (6.0–7.3; R2 = 0.67). No relationship between phosphorus circulation activity and bacterial biomass was observed at acidic (pH < 6.0) or alkaline (pH > 7.3) pH. A negative correlation between Fe and Al concentrations and phosphorus circulation activity was observed at acidic pH (R2 = 0.72 and 0.73, respectively), as well as for Ca at alkaline pH (R2 = 0.64). Therefore, bacterial biomass, pH, and mineral concentration should be considered together for activation of phosphorus circulation activity in the soil. A relationship model was proposed based on the effects of bacterial biomass and mineral concentration on phosphorus circulation activity. The suitable conditions of bacterial biomass, pH, and mineral concentration for phosphorus circulation activity could be estimated from the relationship model.

Aims Soils are known to be significant sources of atmospheric nitric oxide (NO), a key compound in atmospheric chemistry. NO is a key regulating substance for inter- and intra-species signalling and competition and affects plant growth and soil microbial metabolisms. However, little is known about NO concentration in soils and production of NO in the soil profile. Methods Here we report on soil NO concentrations down to 65 cm soil depth and soil surface flux measurements over a 15 months period in subdaily resolution. This is supplemented by information on aerobic and anaerobic NO production in various soil layers of a spruce stand in SW Germany. Results NO concentrations showed a clear seasonality with highest concentrations of up to 800 nmol mol −1 (or part per billion in volume mixing ratio; ppbv) at the interface between the organic Of-Oh sub-layers in the summer. NO concentrations in the mineral subsoil (−65 cm) were approx. One order of magnitude lower than in the organic layer. Dynamic changes of soil NO concentrations were closely correlated with soil surface NO fluxes. Differences in soil NO concentrations across the soil profile reflected differences in aerobic and anaerobic NO production potential. Conclusion The importance of such high NO concentrations for soil microbial and plant physiological processes remains unclear, but should be addressed in future research in order to improve our understanding of microbe-microbe and plant-microbe interactions.

Aims The mean biomass ATP concentration in aerobic soils is around 10–11 μmol ATP g −1 biomass C, within a fairly narrow range. It is much lower in short-term incubated laboratory waterlogged soils. However, the biomass ATP concentration in waterlogged paddy soils under field conditions remains unknown. This is investigated. Methods Soil microbial biomass C (biomass C), ATP, biomass ATP and heavy metal (Cd, Zn, and Cu) concentrations in soil and rice were measured in a Chinese paddy soil growing rice. Soils and plants were analyzed at day 0, 30, 75 and 90, over the 90 day growing period with inputs of inorganic fertilizer, or biochar and manure singly or in combination. Results Both biomass C and ATP concentrations increased, range from 14.9–30.5% for microbial biomass C and 115.8–160.1% for ATP, from initial values until the end of the experiment following manure or biochar addition. An important result was that the biomass ATP concentration increased throughout the growth period. There were also significant negative correlations ( p  < 0.05) between total and available Cd and these three microbial parameters, despite the low levels of Cd. Over the same period, total plant Cd concentrations increased, and soil Cd decreased. This suggests that the rice acted as a bioaccumulator. The microbial biomass was then in a continually decreasingly toxic environment and responded rapidly by increasing its size. Conclusions These results demonstrate clear differences in microbial energy dynamics between aerobic and anaerobic microbial populations. Both ATP and biomass C are useful bioindicators of the effects of cadmium contamination on microbial processes in waterlogged soil.

Much of the macroecological information about microorganisms is confounded by the lack of standardized methodology, paucity of metadata and sampling effect of a particular substrate or interacting host taxa. This study aims to disentangle the relative effects of biological, geographical and edaphic variables on the distribution of Alnus-associated ectomycorrhizal (ECM) fungi at the global scale by using comparable sampling and analysis methods. Ribosomal DNA sequence analysis revealed 146 taxa of ECM fungi from 22 Alnus species across 96 sites worldwide. Use of spatial and phylogenetic eigenvectors along with environmental variables in model selection indicated that phylogenetic relations among host plants and geographical links explained 43 and 10%, respectively, in ECM fungal community composition, whereas soil calcium concentration positively influenced taxonomic richness. Intrageneric phylogenetic relations among host plants and regional processes largely account for the global biogeographic distribution of Alnus-associated ECM fungi. The biogeography of ECM fungi is consistent with ancient host migration patterns from Eurasia to North America and from southern Europe to northern Europe after the last glacial maximum, indicating codispersal of hosts and their mycobionts.

To investigate the relationships and relative contributions of soil physical and chemical properties, and plant hormones and antioxidant enzymes to maize biomass production with the application of vermicompost and arbuscular mycorrhizal fungi (AMF) in saline-alkali soil. A greenhouse experiment was conducted in a randomized complete block design with maize grown with factorial combinations of plus and minus vermicompost and AMF additions. With the application of vermicompost and AMF, soil macroaggregates increased by 14 to 48%, salt concentration decreased by 12 to 34%, available phosphorus increased by 15 to 59%, and ammonium-N concentration increased by 26 to 40%. In response the shoot K/Na ratio increased by 43 to 261%, with consequent increases in plant nitrogen and phosphorus concentrations, and biomass. The improvements in salt concentration and nutrient availability were paralleled by shoot indole-3-acetic acid concentration increasing by 20 to 28% and shoot catalase activity decreasing by 12 to 48%, which facilitated the increase in nutrient uptake and biomass. The increased biomass was mostly attributed to shoot K/Na ratio and catalase activity, by 54.4% and 9.7%, respectively. The synergistic effects of soil physical and chemical amelioration, and plant endogenously physiological regulation with vermicompost and AMF application effectively improved maize biomass in saline-alkali soil, with shoot K/Na being the key driver of biomass enhancement, and this mechanism merits consideration as an important target to improve plant salinity tolerance and biomass production under salt stress.

Aim: To assess the relative roles of geologically defined terrain types (environmental heterogeneity) and a major river (physical dispersal barrier) as predictors of ecological structuring and biogeographical differentiation within Amazonian forests. Location: Western Brazilian Amazonia, where the Juruá river and its terraces cross a 1000-km-long boundary between two geological formations (the Solimões and Içá Formations). Methods: We sampled a 500-km stretch of the Juruá with 71 transects (5 m by 500 m) that spanned both the river and the geological boundary. All transects were inventoried for pteridophytes (ferns and lycophytes) and Melastomataceae, and a subset of 39 transects also for palms and Zingiberales. Three surface soil samples were collected from each transect. The data were analysed using ordinations, regression trees, indicator species analyses and Mantel tests. Results: All plant groups showed congruent species turnover between geologically defined terrain types, but little evidence of isolation by the river or geographical distance. Soil cation concentration differed between the Solimöes Formation and other terrain types and emerged as the main explanatory factor for species turnover. A large proportion of the plant species were significant indicators for specific parts of the soil cation concentration gradient, and these edaphic associations were congruent with those found in other parts of Amazonia. Pteridophytes had a larger proportion of species in the cation-rich soils than the other plant groups did, and palms had a higher proportion of generalists. Main conclusions: The geological boundary between the Solimões and Içá formations is confirmed as significant floristic turnover zone. As it runs in a north-south orientation for more than 1000 km, the edaphic differences associated with this boundary have wide-ranging implications for speciation and biogeographical patterns in Amazonia.

Sufficient soil moisture is required to ensure the successful transplantation of sweet potato seedlings. Thus, reasonable water management is essential for achieving high quality and yield in sweet potato production. We conducted field experiments in northern China, planted on 18 May and harvested on 18 October 2021, at the Nancun Experimental Base of Qingdao Agricultural University. Three water management treatments were tested for sweet potato seedlings after transplanting: hole irrigation (W1), optimized drip irrigation (W2), and traditional drip irrigation (W3). The variation characteristics of soil volumetric water content, soil temperature, and soil CO2 concentration in the root zone were monitored in situ for 0–50 days. The agronomy, root morphology, photosynthetic parameters, 13C accumulation, yield, and yield components of sweet potato were determined. The results showed that soil VWC was maintained at 22–25% and 27–32% in the hole irrigation and combined drip irrigation treatments, respectively, from 0 to 30 days after transplanting. However, there was no significant difference between the traditional (W3) and optimized (W2) drip irrigation systems. From 30 to 50 days after transplanting, the VWC decreased significantly in all treatments, with significant differences among all treatments. Soil CO2 concentrations were positively correlated with VWC from 0 to 30 days after transplanting but gradually increased from 30 to 50 days, with significant differences among treatments. Soil temperature varied with fluctuations in air temperature, with no significant differences among treatments. Sweet potato survival rates were significantly lower in the hole irrigation treatments than in the drip irrigation treatments, with no significant difference between W2 and W3. The aboveground biomass, photosynthetic parameters, and leaf area index were significantly higher under drip irrigation than under hole irrigation, and values were higher in W3 than in W2. However, the total root length, root volume, and 13C partitioning rate were higher in W2 than in W3. These findings suggest that excessive drip irrigation can lead to an imbalance in sweet potato reservoir sources. Compared with W1, the W2 and W3 treatments exhibited significant yield increases of 42.98% and 36.49%, respectively. The W2 treatment had the lowest sweet potato deformity rate.

PurposeThis study compared the effects of four invasive plants, namely Impatiens glandulifera, Reynoutria japonica, Rudbeckia laciniata, and Solidago gigantea, as well as two native species—Artemisia vulgaris, Phalaris arundinacea, and their mixture on soil physicochemical properties in a pot experiment.Materials and methodsPlants were planted in pots in two loamy sand soils. The soils were collected from fallows located outside (fallow soil) and within river valley (valley soil) under native plant communities. Aboveground plant biomass, cover, and soil physicochemical properties such as nutrient concentrations, pH, and water holding capacity (WHC) were measured after two growing seasons. Discriminant analysis (DA) was used to identify soil variables responsible for the discrimination between plant treatments. Identified variables were further compared between treatments using one-way ANOVA followed by Tukey’s HSD test.Results and discussionPlant biomass, cover, and soil parameters depended on species and soil type. DA effectively separated soils under different plant species. DA on fallow soil data separated R. laciniata from all other treatments, especially I. glandulifera, native species and bare soil, along axis 1 (related mainly to exchangeable K, N-NH4, total P, N-NO3, and WHC). Large differences were found between R. laciniata and S. gigantea as indicated by axis 2 (S-SO4, exchangeable Mg, total P, exchangeable Ca, and total Mg). DA on valley soil data separated R. japonica from all other treatments, particularly S. gigantea, R. laciniata, and native mixture, along axis 1 (N-NO3, total N, S-SO4, total P, pH). Along axis 2 (N-NO3, N-NH4, Olsen P, exchangeable K, WHC), large differences were observed between I. glandulifera and all other invaders.ConclusionsPlant influence on soil differed both among invasive species and between invasive and native species. Impatiens glandulifera had a relatively weak effect and its soil was similar to both native and bare soils. Multidirectional effects of different invaders resulted in a considerable divergence in soil characteristics. Invasion-driven changes in the soil environment may trigger feedbacks that stabilize or accelerate invasion and hinder re-colonization by native vegetation, which has implications for the restoration of invaded habitats.