Soil Biochemical Processes Research Articles

Extracellular enzyme activity and stoichiometry reveal P limitation in the wild panda habitat of the Qinling Mountains

AbstractSoil microbial extracellular enzymes play crucial roles in soil carbon and nutrient cycling by catalyzing soil biochemical processes. However, the activity and stoichiometry of enzymes involved in the carbon, nitrogen, and phosphorus cycles in the environment with the highest density of wild giant pandas on the southern slopes of the Qinling Mountains is unknown. We have established eight research areas at an elevation of 1090–2621 m. The β‐1,4‐glucosidase (BG), β‐1,4‐N‐acetylglucosaminidase (NAG), and acid phosphatase (APase) in soil samples were measured. We used redundancy analysis and structural equation model to evaluate the driving factors of metabolic restriction of soil microorganisms along the elevational gradient, and four models were used to cross‐evaluate the nutrient restriction status of soil microorganisms. The results showed that most soil physiochemical properties, soil microbial biomass, and microbial extracellular enzymes exhibited a hump‐shaped trend with increasing elevation. Elevation indirectly affected soil enzyme activity and stoichiometry by C, N, and P status. Microorganisms are limited by C at lower and higher elevations but limited by N at medium elevations. These results could help strengthen the conservation and management of the wild panda's natural habitat.

Onion Varieties (Allium Ascalonicum L.) Test With Application Of Several Kinds Microbia Consortium Its Influence On Growth and Yield

Shallots are one of the horticultural commodities that Indonesian people need. The use of bacterial consortia in shallot cultivation is expected to be useful for increasing soil fertility due to soil biochemical processes. This research aims to determine the effect of applying a microbial consortium from several products to the growth and yield of several shallot varieties. This research was carried out using a Split Plot Design with a split plot method which consists of two factors, namely: 1. Red onion variety, (V1: local rubber variety; V2: white local variety; V3: local Javanese varieties), 2. Types of decomposing plants (microbial consortium), : (P0: Control; P1: M21; P2: EM4; P3: Beka Decomposer). The research results showed: (1) The variety test showed very significant plant height, number of leaves, fresh stover weight, dry stover weight, tuber diameter, fresh tuber weight per bunch, tuber dry weight per bunch, and tuber dry weight per plot. However, there was no real difference between the number of bulbs per plant and the number of bulbs per plot. (2) The combination of microbial consortia with shallot varieties showed significantly different results regarding the number of leaves and bulb diameter. However, there were no real differences in plant height, fresh stover weight, dry stover weight, number of tubers per plant, number of tubers per plot, fresh weight of tubers per bunch, dry weight of tubers per bunch and dry weight of tubers per bunch. (3) The research results showed that the highest yield was obtained from the combination of V2P1 with the treatment of local white varieties of shallots and the application of the M21 microbial consortium with an average value of 150.27 g/plot (16,905 kg/ha or 16.9 tons/ha).

Effects of drought on enzyme activities and hotspot distribution along plant roots

The frequency and severity of drought are projected to increase due to climate change, and Southeast Asia is no exception. Water scarcity hampers all biochemical processes in soil and induces stunted plant growth. While the rhizosphere harbors the most dynamic biochemical processes in the biosphere, the interaction mechanisms between residing microbes and plant roots under drought are poorly understood. In this research, soybean was planted in soil collected from the Red River Delta of Vietnam to test two hypotheses: (i) drought reduces rhizosphere enzyme activities and hampers the extent of the high enzyme activity along single root (from the root tips), and (ii) the turnover time of substrate by enzymes increases with decreasing soil moisture. The research aimed to characterize distributions of β-glucosidase and acid phosphatase enzymes in a distance from root tips. In addition, enzyme activities and plant root and shoot characteristics (length and weight) were investigated. The results demonstrated that shoot length was more impacted by drought than root length with the reduction of 25% for the former and 5% for the later. Meanwhile, the reduction in shoot weight was 61%, and root weight was 90% as the plant experienced drought conditions. The extent of a hotspot for enzymes along a single plant root, measured from the root tips, also decreased in response to drought. Furthermore, drought reduced both rhizosphere enzyme activities, resulting in a slower turnover time of β-D-glucopyranoside (MUF-G) and 4-methylumbelliferyl-phosphate(MUF-P) substrates. The research has shed light on the adverse impacts of drought on root-microbe interactions, which ultimately lead to poor crop growth.

Phosphorus Rather than Nitrogen Addition Changed Soil Cyanobacterial Community in a Tropical Secondary Forest of South China

Soil cyanobacteria in tropical forests is understudied despite its important role in soil biochemical process and plant growth. Under a nitrogen (N) deposition background in tropical forests, it is important to learn how soil cyanobacterial communities respond to N deposition and whether phosphorus (P) mediated this response. A fully two-factor (N and P additions) factorial design with four blocks (replicates), each including a 12 × 12 m plot per treatment (Control, +N, +P, and +NP) were established in a tropical secondary forest in 2009. In July of 2022, soil cyanobacteria at 0–10 cm and 10–20 cm depths in the experimental site were collected and analyzed using a metagenomic method. The impact of N and P additions on soil cyanobacteria remained consistent across the different soil depths, even though there was a significant contrast between the two layers. The effect of N addition on soil cyanobacteria did not significantly interact with P addition. N addition increased soil N availability and decreased soil pH but did not significantly affect the soil cyanobacterial community. In contrast, P addition increased soil P availability and soil pH, but decreased soil N availability and substantially changed the soil cyanobacterial community. P addition significantly decreased the abundance of soil cyanobacteria, especially abundant ones. P addition also increased cyanobacterial species richness and Shannon’s diversity, which might be explained by the decline in dominant species and the emergence of new species as nestedness and indicator species analyses suggest. We concluded that (1) soil cyanobacteria in tropical forests exhibits a greater sensitivity to elevated P availability compared to N; (2) an increase in soil P supply may mitigate the advantage held by dominant species, thus facilitating the growth of other species and leading to alterations in the soil cyanobacterial community. This study improves our understanding on how soil cyanobacterial communities in tropical forest responds to N and P addition.

Impact of Potassium Inoculants and Biotite on Soil Microbial Population and Enzymatic Activity under Maize (Zea mays L.) Cultivation in Gangetic Plains

The study explores the impact of potassium inoculants and black mica on soil microbial populations and enzymatic activity in maize cultivated soils. Microbial communities fueled by root exudates play essential roles in nutrient cycling, plant health, and soil structure. This study investigates the effects of potassium-solubilizing bacteria (KSB) and mineral potassium on microbial populations and enzymatic activity across different growth stages of maize. The experiment was conducted in randomized block design with 14 treatments, including combinations of KSB isolates, mineral potassium, and inorganic potassium. Microbial populations (bacteria, fungi, actinomycetes, and KSB) were quantified using serial dilution and plating techniques. Enzymatic activities (dehydrogenase, phosphatase, and urease) were assessed to understand nutrient interactions and microbial influences. The findings indicate that all treatments exhibited increased microbial populations compared to the control. Notably, treatment 75% recommended potassium dose + 25% potassium from Biotite + OVPS 05 consistently demonstrated the highest microbial growth. The presence of KSB appeared crucial in enhancing bacterial and fungal populations. Additionally, enzymatic activities were significantly influenced by treatments, with 75% recommended potassium dose + 25% potassium from Biotite + OVPS 05 showing the highest dehydrogenase, alkaline phosphatase, and urease activities. These results suggest that the combination of KSB isolates and mineral potassium contributes to enhanced microbial populations and soil enzymatic activities, offering insights into sustainable agriculture practices that balance productivity and soil health. The study sheds light on the intricate relationships between microorganisms, nutrients, and soil biochemical processes, providing valuable guidance for future agricultural strategies.

The elevational patterns and key drivers of soil microbial communities strongly depend on soil layer and season

AbstractKnowledge about the elevational patterns of soil microbial biomass and communities can facilitate accurate prediction of the responses of soil biogeochemical processes to climate change. However, previous studies that have considered intra‐ and inter‐annual variations have reported inconsistent results on the one hand, and they have paid little attention to the effect of soil layer on the other hand. We, therefore, conducted a 4‐year in situ soil core incubation experiment along a 2431‐m elevational gradient across the dry valley shrubland, valley‐montane ecotone forest, subalpine coniferous forest, alpine coniferous forest, and alpine meadow in an ecologically fragile alpine‐gorge region on the eastern edge of the Qinghai‐Tibetan Plateau. Soil microbial biomass and community composition in the organic and mineral layers were measured using the phospholipid fatty acids (PLFA) method at five critical periods each year. Our results indicated that soil microbial biomass in the organic layer was the highest in the subalpine coniferous forest, followed by the alpine meadow, alpine coniferous forest, and valley‐montane ecotone forest. In contrast, soil microbial biomass in the mineral layer was significantly higher in the alpine meadow than in the other sites. Soil microbial biomass exhibited differential seasonal fluctuations at different elevations, resulting in their elevational patterns being strongly intra‐annual and inter‐annual dependent. Our results revealed that elevation and seasonality significantly affected soil microbial communities. Seasonality had a more substantial effect than elevation on soil microbial communities during the first 3 years of incubation, whereas the relative importance of seasonal and elevational effects on microbial communities was reversed in the organic layer with incubation time. These results are mainly attributed to the magnitude and direction of effect of environmental variables on soil microbial biomass and communities vary with elevation, soil layer, and sampling time. Briefly, the elevational patterns and dominant factors of soil microbial biomass and communities have intense soil layer and temporal specificity, implying that differential responses of soil biochemical processes to climate change might be observed at different elevations.

Life cycle greenhouse gas emissions for irrigated corn production in the U.S. great plains

Agricultural management practices improve crop yields to satisfy food demand of the growing population. However, these activities can have negative consequences, including the release of greenhouse gas (GHG) emissions that contribute to global climate change. To mitigate this global environmental problem, the management practices that contribute the most to system GHG emissions should be identified and targeted to mitigate emissions. Accordingly, we estimated the cradle-to-product GHG emissions of irrigated corn production under various farmer-selected scenarios at an experimental testing field in the semi-arid U.S. Great Plains. We applied a carbon footprint approach to quantify life cycle GHG emissions associated with pre-field (e.g., energy production, fertilizer production) and in-field (e.g., groundwater pumping, fertilizer application) activities within fourteen scenarios in the 2020 Oklahoma Testing Ag Performance Solutions (TAPS) sprinkler corn competition. We determined that 63% of the total GHG emission from corn production was associated with in-field activities and that agricultural soil emissions were the overall driving factor. Soil biochemical processes within agricultural soils were expected to contribute an average of 89 ± 18 g CO2-eq kg−1 corn of the total 271 ± 46 g CO2-eq kg−1 corn estimated from these systems. On-site natural gas combustion for agricultural groundwater pumping, pre-field fertilizer production, and pre-field energy production for groundwater pumping were the next most influential parameters on total GHG emissions. Diesel fuel, seed, and herbicide production had insignificant contributions to total GHG emissions from corn production. The model was most sensitive to the modeled GHG emissions from agricultural soil, which had significant uncertainty in the emission factor. Therefore, future efforts should target field measurements to better predict the contribution of direct soil emissions to total GHG emissions, particularly under different managements. In addition, identifying the optimal application rate of irrigation water and fertilizer will help to decrease GHG emissions from groundwater irrigated crops.

Responses of Soil Enzyme Activity to Long-Term Nitrogen Enrichment and Water Addition in a Typical Steppe

Enzyme activity plays an important role in soil biochemical processes and is a key factor driving nutrient cycling. Although a great number of studies examined the effects of nitrogen (N) enrichment and water (W) addition on soil enzyme activity, most of them focused on the effect of only one resource and are based on short-term investigations. The separate and interactive effects of long-term changes in nitrogen and water on soil enzyme activity remain largely unexplored. In this study, we demonstrated the responses of two types of soil enzyme, β-1,4-glucosidase (BG) and acid phosphatase (APA), to increased nitrogen and water based on a 16-year experiment conducted in a typical grassland in northern China. The results show that: (1) nitrogen addition inhibited BG and APA in 2019 and 2020; (2) water addition had no significant effect on BG activity, but significantly reduced APA activity in 2020; and (3) redundancy analysis (RDA) showed that nitrogen and water addition affected soil enzyme activity mainly by affecting soil microbial biomass carbon (MBC). The present research offers a comprehensive explanation of how atmospheric nitrogen deposition and precipitation patterns affect the characteristics of microorganisms and the cycling of nutrients in grassland ecosystems.

Alfisol Soil Fertility Before Planting and After Harvest as Meloon Planting Media with Bioboost Fertilization

Soil fertility is important in the cultivation process. Soil fertility is the potential of the soil to provide nutrients in sufficient quantities in available and balanced forms to ensure optimum plant growth and production. The current availability of nutrients in the soil has decreased as a result of continuous land use with the use of chemical fertilizers in the cultivation process, plus leaching and erosion by rainwater, not least in Alfisol soils. Therefore, fertilization with organic materials is carried out, namely the provision of Bioboost fertilizer. Bio boost is a biological fertilizer containing superior soil microorganisms, useful for increasing soil fertility as a result of soil biochemical processes. One of the applications of organic cultivation is the cultivation of melon (Cucumis melo L.) because melon is a plant that has high economic value and is profitable to be cultivated as a source of income for farmers. Based on this, a study was conducted to determine the nutrient status of Alfisol soil before planting and after harvesting which was used as a Melon plant with various concentrations of Bioobost fertilization. Furthermore, for the analysis of soil fertility, laboratory analysis was carried out by taking 1 kg of disturbed soil samples that had been air-dried and then analyzing soil properties, namely texture, pH (H2O), C-Organic (%), Nitrogen (%), P2O5 (ppm), K (cmol kg-1), Ca (cmol kg-1), Mg (cmol kg-1), Na (cmol kg-1), Na (cmol kg-1), CEC (cmol kg-1), and KB (%). The application of Bio boosts fertilizer showed an increase in the nutrient status of Alfisol soil as a Melon growing from low to moderate categories before planting to medium to high categories after harvest. The more concentration of Bioboost fertilizer given, the soil nutrient status also increases. The concentration of P4 (1100ml bio boost + 400ml water) gave the highest increase in nutrient status.
 Keywords: bioboost; soil-fertility; melon

Structure and biogeochemical process of microaggregates in a water source area of China’s South-to-North Water Diversion Project according to different land use types

Soil biogeochemical processes have the potential to impact water quality in source areas of water diversion projects. This study aimed to explore the differences in biochemical processes and mechanisms at the microaggregate scale for different land use types in the water source area of China's Middle Route of the South-to-North Water Diversion Project. The study compared four typical land use types—forests, shrublands, terraces, and cultivated land—by characterizing the microaggregates using various analytical techniques, including scanning electron microscopy (SEM), SEM-EDS plane scan analysis, X-ray diffraction (XRD), X-ray fluorescence (XRF) spectroscopy, and Fourier transform infrared (FTIR) spectroscopy. Microaggregates from forests and shrublands had a flocculent spatial structure, while those from terraces had a nondirectional plate-like spatial structure, and those from cultivated land had a laminar spatial structure. Additionally, elements such as Mg, Al, and Fe were enriched in clay particles when combined with microaggregates. The mineral composition of clay varied significantly between different land use practices, with illite, chlorite, anorthite, albite, and quartz present in higher proportions in terraces and cultivated land than in forests and shrublands. Moreover, the contents of transitional elements such as Ti, Fe, Zn, Y, and Zr increased with each successive land use practice. Soil organic matter (SOM) was observed to decline in the order of forest > shrubland > terraces > cultivated land. Over-tillage appeared to be the primary mechanism of organic matter loss due to long-term tillage. The results of this study provide valuable insights into soil erosion and chemical transport dynamics. The mineral composition and spatial structure of microaggregates are important determinants of soil biochemical processes and mechanisms, which can influence water quality. The findings suggest that forest and shrubland management practices may be more conducive to maintaining soil health and water quality in source areas of water diversion projects.

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

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

Keeping thinning-derived deadwood logs on forest floor improves soil organic carbon, microbial biomass, and enzyme activity in a temperate spruce forest

Deadwood is a key component of forest ecosystems, but there is limited information on how it influences forest soils. Moreover, studies on the effect of thinning-derived deadwood logs on forest soil properties are lacking. This study aimed to investigate the impact of thinning-derived deadwood logs on the soil chemical and microbial properties of a managed spruce forest on a loamy sand Podzol in Bavaria, Germany, after about 15 years. Deadwood increased the soil organic carbon contents by 59% and 56% at 0–4 cm and 8–12 cm depths, respectively. Under deadwood, the soil dissolved organic carbon and carbon to nitrogen ratio increased by 66% and 15% at 0–4 cm depth and by 55% and 28% at 8–12 cm depth, respectively. Deadwood also induced 71% and 92% higher microbial biomass carbon, 106% and 125% higher microbial biomass nitrogen, and 136% and 44% higher β-glucosidase activity in the soil at 0–4 cm and 8–12 cm depths, respectively. Many of the measured variables significantly correlated with soil organic carbon suggesting that deadwood modified the soil biochemical processes by altering soil carbon storage. Our results indicate the potential of thinned spruce deadwood logs to sequester carbon and improve the fertility of Podzol soils. This could be associated with the slow decay rate of spruce deadwood logs and low biological activity of Podzols that promote the accumulation of soil carbon. We propose that leaving thinning-derived deadwood on the forest floor can support soil and forest sustainability as well as carbon sequestration.

Enzyme activity after applying alkaline biosolids to agricultural soil

Municipal wastewater biosolids are nutrient-rich residuals with potential as crop fertilizer, if their alkalinity does not adversely affect soil biochemical processes. This study assessed the potential soil enzyme activity after three annual applications of biosolids in a conventionally tilled field under silage corn ( Zea mays L.). Biosolids were municipal wastewater sludge treated by mesophilic anaerobic digestion, lime stabilization, or composting, compared with urea fertilizer and an unfertilized control. Generally, the potential soil enzyme activity did not change with biosolids application, but the N-acetylglucosaminidase activity increased in soil amended with lime-stabilized biosolids, which also had higher soil pH and greater soil NH4 + concentration.

Independent response of soil DOM to MAT and MAP: Evidence from a large-scale survey of moss crusts in mainland China

It is known soil dissolved organic matter (DOM) plays an important role in global biogeochemical cycle and is an important factor in soil-forming processes. However, the linkage between the diversity of chemical composition and properties of DOM molecules and the climatic conditions (temperature, precipitation) at regional scales is still not well studied. Therefore, in our study, we selected 33 soil DOM samples which were, divided into temperature-variation and precipitation-variation groups, and used Fourier transform ion cyclotron resonance mass spectrometry to analyze the influence of climate on the chemical characterizations of DOM. Our results showed that although the factors affecting the chemical properties of DOM are complex, mean annual precipitation (MAP) and mean annual temperature (MAT) can explain part of the chemical changes of DOM, and the two data sets in this study can well separate the effects of MAP and MAT on DOM, respectively. The results showed that the content of lignin and tannin were positively related to MAP, while carbohydrate, lipid, unsaturated hydrocarbon and protein decreased with the increase in MAP. The content of nitrogen-containing molecules gradually decreased with the increase in MAT. Meanwhile, the content of sulfur-containing molecules was almost unaffected by the MAP and MAT. In terms of DOM composition, the content of protein decreased with the increase in MAT. The results suggested that the chemical characteristics of DOM is an ecosystem attribute that is closely related to the environment and may be used to predict large-scale soil biochemical processes in the soil carbon cycle.

An open Soil Structure Library based on X-ray CT data

Abstract. Soil structure in terms of the spatial arrangement of pores and solids is highly relevant for most physical and biochemical processes in soil. While this was known for a long time, a scientific approach to quantify soil structural characteristics was also missing for a long time. This was due to its buried nature but also due to the three-dimensional complexity. During the last two decades, tools to acquire full 3D images of undisturbed soil became more and more available and a number of powerful software tools were developed to reduce the complexity to a set of meaningful numbers. However, the standardization of soil structure analysis for a better comparability of the results is not well developed and the accessibility of required computing facilities and software is still limited. At this stage, we introduce an open-access Soil Structure Library (https://structurelib.ufz.de/, last access: 22 July 2022) which offers well-defined soil structure analyses for X-ray CT (computed tomography) data sets uploaded by interested scientists. At the same time, the aim of this library is to serve as an open data source for real pore structures as developed in a wide spectrum of different soil types under different site conditions all over the globe, by making accessible the uploaded binarized 3D images. By combining pore structure metrics with essential soil information requested during upload (e.g., bulk density, texture, organic carbon content), this Soil Structure Library can be harnessed towards data mining and development of soil-structure-based pedotransfer functions. In this paper, we describe the architecture of the Soil Structure Library and the provided metrics. This is complemented by an example of how the database can be used to address new research questions.

Field response of N2O emissions, microbial communities, soil biochemical processes and winter barley growth to the addition of conventional and biodegradable microplastics

Microplastic contamination in agroecosystems is becoming more prevalent due to the direct use of plastics in agriculture (e.g., mulch films) and via contamination of amendments (e.g., compost, biosolids application). Long-term use of agricultural plastics and microplastic pollution could lead to soil degradation and reduced crop health due to the slow degradation of conventional plastics creating legacy plastic. Biodegradable plastics are more commonly being used, both domestically and in agriculture, to minimise plastic pollution due to their biodegradable nature. However, the influence of a biodegradable plastics on soil function at the field scale is largely unknown. We investigated the effect of conventional (polyethylene) and biodegradable (PHBV) microplastics on N2O emissions and soil biochemical processes in a field trial of winter barley. Microplastic was added to the soil at realistic levels (100 kg ha-1) for both conventional and biodegradable treatments. N2O emissions were measured throughout the growing season alongside key soil quality indicators (microbial community composition, ammonium, nitrate, moisture content, pH and EC). Overall, microplastic addition had no observable effect on crop yield, microbial communities or soil biochemical properties. Yet, we found cumulative N2O emissions were reduced by two-thirds following conventional microplastic addition compared to the no-plastic and biodegradable microplastic treatments. We believe this response is due to the lower soil moisture levels over the winter in the conventional microplastic treatment. Overall, the response of key soil parameters to microplastic addition show fewer negative effects to those seen in high dose laboratory mesocosm experiments. Thus, it is imperative that long-term field experiments at realistic dose rates be undertaken to quantify the real risk that microplastics pose to agroecosystem health.

Distributions and Influencing Factors of Soil Organic Carbon Fractions under Different Vegetation Restoration Conditions in a Subtropical Mountainous Area, SW China

Vegetation type is known to affect soil organic carbon (SOC) storage. However, the magnitudes and distributions of SOC sequestration and driving factors for different vegetation types are still largely unknown. Thus, we studied the changes in SOC fractions along soil profiles for different vegetation restoration types and their relationships with soil properties. We selected five vegetation types and collected soil samples from depth intervals of 0–10, 10–30, 30–60, and 60–90 cm. Five soil carbon fractions and the soil properties were tested to evaluate the soil carbon fraction distributions and influencing factors. Our results demonstrated that the concentrations of total organic carbon (TOC) and five carbon fractions were strongly affected by vegetation types and soil depths. The concentrations of all five soil carbon fractions in 0–10 cm depth were higher than those in the other three soil depths and generally increased with vegetation complexity. The Pearson correlations and redundancy analysis showed that the fractions of soil glomalin-related soil protein (GRSP) and Fe oxides as well as the soil bulk densities, were the most significant related to soil TOC levels and carbon fractions, which suggests that soil biochemical and physicochemical processes are among the most important mechanisms that contribute to SOC persistence. Considering the sensitive indices of the soil carbon variables and PCA results, soil permanganate oxidizable carbon (POXC) was considered to be the most sensitive index for differentiating the effects of vegetation types. These results provide important information regarding the distributions and driving factors of the carbon fractions that result from different vegetation restoration types and will help to improve our understanding of soil carbon sequestration during vegetation restoration processes.

Short-Term Resilience of Soil Microbial Communities and Functions Following Severe Environmental Changes

Soil microorganisms are key drivers of soil biochemical processes, but the resilience of microbial communities and their metabolic activity after an extreme environmental change is still largely unknown. We studied structural (bacterial and fungal communities) and functional responses (soil respiration, adenosine triphosphate (ATP) content, hydrolase activities involved in the mineralization of organic C, N, P and S, and microbial community-level physiological profiles (CLPPs)) during the microbial recolonization of three heat-sterilized forest soils followed by cross- or self-reinoculation and incubation for 1, 7 and 30 days. Soil ATP content, biochemical activities and CLPP were annihilated by autoclaving, whereas most of the hydrolase activities were reduced to varying extents depending on the soil and enzyme activity considered. During the incubation period, the combination of self- and cross-reinoculation of different sterilized soils produced rapid dynamic changes in enzymatic activity as well as in microbial structure and catabolic activity. Physicochemical properties of the original soils exerted a major influence in shaping soil functional diversity, while reinoculation of sterilized soils promoted faster and greater changes in bacterial community structure than in fungal communities, varying with incubation period and soil type. Our results also confirmed the importance of microbial richness in determining soil resilience under severe disturbances. In particular, the new microbial communities detected in the treated soils revealed the occurrence of taxa which were not detected in the original soils. This result confirmed that rare microbial taxa rather than the dominant ones may be the major drivers of soil functionality and resilience.

ЭНЕРГОСБЕРЕГАЮЩАЯ ПОДГОТОВКА ПОЧВЫ ПОД ПОСАДКУ ХМЕЛЯ

At present, the preparation of the soil for the hop plant with machines of traditional hop production technology is unrealistic, since there are no more hops and no one is producing them. In this regard, a progressive technology for growing hops and promising machines for them, including for energy-saving tillage for hops, have been proposed. As the main cultivation, two-strip soil cultivation was used for rows of hops with a combined subsoiler-drener developed at the Chuvash State Agrarian University. Moreover, loosening is carried out with the simultaneous introduction of liquefied litterless manure with a dose of 100-120 t / ha to the subsurface zone from 0.20 to 0.60 m. In the soil, liquefied litterless manure fills the drainage canal and the soil pores adjacent to the canal, activates the activity of microorganisms and soil biochemical processes. Row loosening with a combined machine allows to reduce the energy consumption of processing by 57% compared to continuous plowing with plantation plows and to exclude the operation of applying bedding manure with subsequent moldboard embedding. As a pre-planting soil preparation, cultivation with combined stubble cultivators of the KST-3,8 type and its analogues with the incorporation of crushed green manure (up to 75%), high-quality leveling and crumbling of the soil is proposed. Stirring and leveling of the field surface is provided by afrontal discs behind the last row of flat-cut tines, crumbling - by a ribbed roller. The maneuverability of such a cultivator in the cramped conditions of the hop is taken into account. Replacement of plowing operations with general purpose plows and subsequent leveling by a cultivator allows an additional 45-50% reduction in the energy intensity of pre-planting soil cultivation. The main energy source in the main tillage is the tractor BTZ-243k

Soil enzyme activities of typical plant communities after vegetation restoration on the Loess Plateau, China

Soil enzyme activities can indicate soil quality due to the catalyst roles enzymes play in various soil biochemical processes. However, little is known about the variations in soil enzyme activities among different plant communities with diverse environmental conditions. Here, the activities of four soil enzymes, catalase (CA), urease (UA), polyphenol oxidase (POA) and saccharase (SA), were investigated in shrub lands, forest lands and abandoned cropland on the Loess Plateau, China. Soil microbial biomass (MB) that contained bacteria, fungi and actinomycetes was also analyzed to determine the variations in enzyme activities. The results showed that soil enzyme activities varied significantly among different plant communities. Land uses, climate factors, topography and soil properties are all related to variations in enzyme activities. Specifically, soil properties including soil nutrients and MB were stable driving factors. With increasing soil MB, UA increased linearly, but CA, POA and SA increased exponentially, which might have resulted from soil nutrient deficiencies. Different plant communities with diverse microbial metabolisms performed differently in terms of soil enzyme activities, for example, in comparison to the other studied species, Hippophae rhamnoides had the greatest advantages and could improve the soil environment more effectively. Therefore, we suggest that the afforestation of Hippophae rhamnoides is an appropriate scenario for vegetation restoration in the typical hilly region of the Loess Plateau. AbbreviationsUnlabelled TableCAcatalase activityUAurease activityPOApolyphenol oxidase activitySAsaccharase activityMBmicrobial biomassSLshrub landFLforest landACabandoned croplandMATmean annual temperatureMAPmean annual precipitationSOCsoil organic carbonTNtotal nitrogenANavailable nitrogenTPtotal phosphorousAPavailable phosphorousTKtotal potassiumAKavailable potassium