Soil Alkali-hydrolyzable Nitrogen Research Articles

How Organic Mulching Influences the Soil Bacterial Community Structure and Function in Urban Forests.

Urban forest soil is often disturbed by frequent human activity. Organic mulching is effective for improving soil quality; however, the effects of organic mulching on soil bacterial communities in urban forests are still largely unexplored. This study evaluated how organic mulching changed the urban forest soil bacterial community through an incubation experiment. Four treatments were applied: (1) no organic mulch (CK); (2) wood chips alone (5 g, Mw); (3) wood compost alone (5 g, Mc); and (4) wood chips + wood compost (This mulch was divided into two layers, i.e., the upper layer of wood chips (2.5 g) and the lower layer wood compost (2.5 g, Mw+c).) We found significant differences in the soil physicochemical properties under organic mulching after incubation. Overall, organic mulching can alter soil bacterial community structure. Soil alkali-hydrolyzable nitrogen, soil organic carbon, soil total nitrogen, and carbon-nitrogen ratio were the main factors affecting soil microbial community structures. Soil bacterial groups under organic mulching treatments mainly acted on the C and N cycling of functional pathways in soil. This study suggests that organic mulching could maintain the development of soil bacteria, which establishes a theoretical foundation for enhancing the microbiological environment of urban forest soils.

Biochar preparation and its effects with reduced compound fertilizer on nutrients, phenolic acid and fungal community in tobacco rhizosphere soil

Biochar is a carbon-rich soil conditioner produced from pyrolysis of biomass, it has been widely used to enhance soil quality because of its physical adsorption as well as water and fertilizer conservation functions. This work aimed to improve the soil quality of continuously cropped flue-cured tobacco fields using biochar prepared from agricultural waste. To explore the impact of reduced compound fertilizer with biochar application on nutrients, phenolic acid contents and fungi diversity in the rhizosphere soil, 4 treatments were set: regular compound fertilizer application (T1), and biochar with reduced compound fertilizer in different proportions (T2, T3, T4, with 100, 75, 50% of compound fertilizer, respectively). The physicochemical properties of the prepared biochar were characterized and observed using electron microscopy. The results indicated that, a noticeable increase in the content of soil organic matter (SOM) and soil organic carbon (SOC) in T2 treatment compared to T1 treatment. Moreover, T2 treatment demonstrated a significant improvement in the contents of alkali-hydrolyzable nitrogen (AN), available phosphorus (AP), and available potassium (AK), with increases of 9.29%, 15.85% and 25.42% compared to T1 treatment, respectively. While a gradual decrease in soil AN, AP, and AK content was observed with the reduction of compound fertilizer application (T2–T4), there was no obvious difference between T3 and T1. For total phenolic acid, the content in T2 treatment significantly decreased by 35.99% compared to T1 treatment, while T3 and T4 treatments showed significant reductions of 15.30 and 18.73% respectively, compared to T2 treatment. Biochar application could enhance the fungal community’s abundance and diversity in the rhizosphere soil. Fungal community exhibited the highest richness under T3 treatment, while the relative abundance ofFusariumandMortierellareduced as the decrease of compound fertilizer (T2–T4). In conclusion, the reduced compound fertilizer with biochar application could reduce nutrient loss, phenolic acids accumulation, and improving the abundance of fungal community in the rhizosphere soil. This paper provides a reference for biochar combined with compound fertilizer to improve soil from the regulation of allelochemicals and soil fungi.

Effects of drip irrigation on yield, soil fertility and soil enzyme activity of different potato varieties in Northwest China.

The effects of different irrigation and fertilization on potato yield, soil fertility and soil enzyme activity of different varieties under drip irrigation fertilization mode were studied, which could provide support for selecting the best varieties in Northwest China. Three factors and three levels orthogonal experimental design method, a total of nine treatments. The three irrigation levels were W1 (100% crop evapotranspiration (ETC)), W2 (80% ETC) and W3 (60% ETC). The three fertilization levels were F1 (N-P2O5-K2O, 240-120-300 kg ha-1), F2 (180-90-225 kg ha-1) and F3 (120-60-150 kg ha-1). The three varieties were V1 (Feiuritar), V2 (Longshu7) and V3 (Qingshu 9). The results showed that different irrigation and fertilization had significant effects on potato yield, soil fertility and soil enzyme activity in root zone. The highest yield of T5 (80%ETC, 180-90-225 kg ha-1, Qingshu 9) was 49,222.3 kg ha-1. With the increase of fertilizer application rate, potato yield and soil enzyme activity in root zone increased first and then decreased, but soil electrical conductivity (SEC), soil nitrate-N content (SNNC), soil alkali-hydrolyzable nitrogen content (SAHC), soil available potassium (AK), soil available phosphorus (AP), soil ammonium-N content (SANC) and soil organic matter (SOM) in root zone increased continuously. The yield, soil catalase activity, soil urease activity and soil sucrase activity at W2 were 2.81% and 22.2%, 1.84% and 7.04%, 8.26% and 9.62%, 5.34% and 13.36% higher than those at W1 and W3, respectively. The overall trend of soil water content, soil nutrient content and enzyme activity in root zone was 0-20 cm >20-40 cm >40-60 cm soil layer. There were many soil factors affecting tuber yield, among which soil enzyme activity, pH value and root zone conductivity were the key factors. The results showed that T5 (80%ETC, 180-90-225 kg ha-1, Qingshu 9) was the best treatment to improve soil enzyme activity and yield.

Long-term effects of restoration on the links between above-and belowground biodiversity in degraded Horqin sandy grassland, Northern China

Long-term ecological restoration plays an important role in the sustainable development of degraded grassland ecosystem. In this study, the levels of species diversity, genetic diversity and soil microbial diversity in restored grassland were measured by vegetation survey, DNA barcoding and soil microbial high-throughput sequencing technology, so as to explore the relationship between above- and belowground biodiversity and its driving factors in Horqin sandy grassland. In this study, the results found that herb are dominated in restoration grassland types. Plant species richness (SR) from post-non-grazing restoration plot (NGR) communities was significantly higher than other restoration communities (10 ± 1.1, p = 0.004). Genetic diversity indices of dominant plant species in chloroplast DNA (cpDNA), were remarkable greater than nuclear DNA (nrDNA) in each recovering sandy grassland plots (amplitude of difference was 44.8%–70.5% in allelic richness (AR), 81.9%–128.1% in expected heterozygosity (HE)). The soil bacterial and fungal richness from natural mobile dune grassland (NM) communities was notably lower than that from recovering grassland types (1641.9 ± 100.4, p < 0.001; 533 ± 16.6, p < 0.001). In this study, heterogeneous levels of genetic variability among different recovering sandy grassland types were detected. Correlation analyses revealed that there were positive correlations between species diversity and genetic diversity (SR & AR: r = 0.56, R2 = 0.31, p < 0.001; SR & HE: r = 0.33, R2 = 0.11, p = 0.045) and a negative correlation between soil microbial diversity and genetic diversity (r = -0.44, R2 = 0.19, p = 0.005). The final structural equation model explained 38% of the variance in SR, 57% in AR, 52% in soil microbial diversity (SD), 49% in aboveground biomass (AGB), 87% in soil organic carbon (SOC), 47% in soil alkali-hydrolyzable nitrogen (SAN) and 69% in soil available phosphorus (SOP). Long-term ecological restoration had significant direct positive effects on AGB, SOC, SAN, SOP, AR, SR and SD. There was a negative correlation between above- and belowground biodiversity and biological and abiotic factors. The results of this study have clarified the above- and underground biodiversity levels of sandy grassland and the relationship with driving factors under long-term ecological restoration measures, and will provide effective support for the management and sustainable development of sandy grassland.

Planting and mowing cover crops as livestock feed to synergistically optimize soil properties, economic profit, and environmental burden on pear orchards in the Yangtze River Basin.

Pears, as an important cash crop, are currently facing great issues due to unsustainable management practices. Cover cropping is a sustainable management strategy that can improve soil fertility and increase fruit yield, while it may also stimulate greenhouse gas emissions. Therefore, synergizing multiple indicators to achieve sustainable development is critical. This study introduces a new management system, namely the planting and mowing of ryegrass as a livestock feed system (PRSS), and analyzes its impact on soil quality, economic benefits, and environmental burdens. Our results indicated that PRSS could increase soil pH from 5.08 to 5.48 and decrease the content of soil alkali-hydrolyzable nitrogen, total phosphate, and available phosphate (26.96-59.89%) while also enhancing yield (+38.51%) compared with the traditional natural grass management system (TMS). The average soil methane fluxes in PRSS were 72.67 μg m-2 day-1 , higher than those of TMS (61.28 μg m-2 day-1 ). However, the gross primary production was lower than TMS (-37.24%), and no significant difference was observed in soil nitrous oxide fluxes. In different scenarios, the total profit of PRSS mode 1 (mowing ryegrass and selling to a livestock company) and PRSS mode 2 (mowing ryegrass and feeding own sheep) were 10 706.21 $ ha-1 and 26 592.87 $ ha-1 respectively. These values are respectively2.36 times and 5.85 times higher than that of TMS. The total global warming potential of TMS (18.19 t CO2 -eq ha-1 ) was 1.29 t CO2 -eq ha-1 higher and 2.89 t CO2 -eq ha-1 lower than that of PRSS mode 1 and mode 2 respectively. Compared with traditional natural grass, planting and mowing ryegrass in pear orchards can optimize soil properties, increase fruit yield, and reduce global warming potential. Different modes can greatly increase revenue but have varying impacts on environmental burdens. These findings can help rebuild the links between farmland and specialized livestock production, contributing to sustainable development in the pear industries. © 2023 Society of Chemical Industry.

Is degradable plastic film alternative? Insights from crop productivity enhancement and soil environment improvement

Currently, it is unclear whether degradable film mulching is a feasible viable alternative to non-degradable film mulching for improving crop productivity and soil environmental conditions. In the present study, a three-year-long field experiment was conducted to evaluate the effects of three alternative degradable films and a traditional plastic film (PF) on soil properties and peanut growth performance. Results showed that degradable films enhanced peanut yields by 6.0–14.3% compared to no mulching (CK), while reduced the peanut yield compared to PF. The results of the structural decomposition model analysis attributed the positive correlations between peanut yields and soil temperature, soil organic carbon, soil alkali-hydrolyzable nitrogen, soil microbial biomass carbon (MBC), and soil microbial biomass nitrogen (MBN). The degradable films decreased soil temperature, soil organic matter, soil alkali-hydrolyzable nitrogen content, MBC and MBN content by 0.12–11.8%, 1.40–10.9%, 1.90–9.91%, 2.31–13.2% and 12.7–34.2% compared to PF, respectively, despite they performed better effects on soil environment than CK. Moreover, the degradation rates of the three degradable films ranged from 7.38% to 91.3%. The aliphatic polyester polylactic acid-based film was found to be the best alternative because of improvement of soil environment and crop yield as well as superior degradation properties.

Optimized soil bacterial structure following grazing exclusion promotes soil nutrient cycling and plant growth

Grazing exclusion is a common grassland restoration strategy, and the effectiveness on optimizing plant species community, increasing vegetation diversity and biomass, and improving soil fertility, has been widely documented in literatures. Soil bacterial community, as one of important ecological components, closely relates to plants and soil features. However, there is no definite conclusion of grazing exclusion effects on various ecological components, especially on soil bacterial community. To clarify this question, we compared the soil bacterial community characteristics and their corresponding vegetation characteristics and soil properties on one 40 years-grazing exclusion (GE) and three free grazing (FG) areas within a Leymus chinensis steppe of Inner Mongolia, China. Our results showed that grazing exclusion could significantly increase the soil bacterial abundance, and optimize the soil bacterial structure, with the synergistic increase of the soil bacterial diversity. The abundance of Euryarchaeota, Verrucomicrobia, Nitrospirae, Proteobacteria, Elusimicrobia, Latescibacteria, and Microgenomates phyla, some taxa of which involved in the N and P cycles, increased significantly following grazing exclusion, while the abundance of Chloroflexi, Firmicutes, Thaumarchaeota, and Pacearchaeota phyla which are often considered to contain many pathogens, decreased significantly. The bacterial phyla increased by grazing exclusion have a significant positive correlation with vegetation biomass and diversity, and soil alkali-hydrolyzable nitrogen content, total nitrogen content, total phosphorus content, organic matter content and water content. The reducing of pathogenic abundance after grazing exclusion provides a healthier environment for plant growth. This work indicates that grazing exclusion optimizes the soil bacterial structure to promote the growth of plants in more sufficient soil nutrients and healthier soil environments, making the enclosed grassland soil ecology form a virtuous circle.

Effects of Sugarcane Leaf Return and Fertilizer Reduction on Maize Growth, Yield and Soil Properties in Red Soil.

In order to make better use of the vast sugarcane leaf straw resources and reduce the overuse of chemical fertilizers in the subtropical red soil region of Guangxi, this study aimed to determine the effects of sugarcane leaf return (SLR) and fertilizer reduction (FR) on maize growth, yield component and yield, and soil properties. A pot experiment with three SLR amounts (full SLR (FS), 120 g/pot; half SLR (HS), 60 g/pot; and no SLR (NS) with three FR levels including full fertilizer (FF), 4.50 g N/pot, 3.00 g P2O5/pot, and 4.50 g K2O/pot; half fertilizer (HF), 2.25 g N/pot, 1.50 g P2O5/pot, and 2.25 g K2O/pot; and no fertilizer (NF)), without nitrogen, phosphorous, and potassium added, was conducted to assess the effects of different SLR amounts and chemical FR levels on maize growth, yield, and soil properties. Compared with no sugarcane leaf return and the no-fertilizer treatment (CK), SLR and FR could increase maize plant height, stalk diameter, number of fully developed maize plant leaves, total leaf area and chlorophyll content, soil alkali-hydrolyzable nitrogen (AN), available phosphorus (AP), available potassium (AK), soil organic matter (SOM), and electrical conductivity (EC). The maize yield component factors of FS and HS were higher in NF treatment than those in NS treatment. The relative increase rate of treatments retained FF/NF and HF/NF under FS or HS condition on 1000 kernel weight, ear diameter, plant air-dried weight, ear height, and yield than that under NS condition. FSHF had not only the largest plant air-dried weight but also the highest maize yield (3225.08 kg/hm2) among nine treatment combinations. The effects of SLR on maize growth and yield and soil properties were lower than those of FR. SLR and FR combined treatment did not affect maize growth but affected maize yield significantly. Soil properties improved more with SLR + FR treatment than with SLR or FR application alone. The plant height, stalk diameter, number of fully developed maize plant leaves, and total leaf area, as well as AN, AP, AK, SOM, and EC levels in soil, were enhanced by SLR and FR incorporation. The experimental results indicated that applying reasonable FR combined with SLR increased AN, AP, AK, SOM, and EC, which improved maize growth and yield and enhanced soil properties in red soil. Hence, FSHF might be a suitable combination of SLR and FR.

Seasonal and spatial variations in soil biochemical properties in areas with different degrees of mining subsidence in Central China

Land subsidence due to underground mining results in soil nutrient loss and reduced soil fertility. Land reclamation, which refers to the improvement of soil nutrients through targeted measures, requires spatial and temporal distribution information on the soil properties. However, this has not yet been studied. Therefore, the spatial autocorrelation of soil chemical and biological properties was examined in the Pingdingshan coal mining area during four seasons in China from 80 collected and analyzed soil samples. The spatial autocorrelation was determined by the global and local Moran’s indices. Spatial clustering and variability were analyzed with ArcGIS 10.2 (Environmental Systems Research Institute, ESRI, USA) and GeoDa 7.0 software (Center for Spatial Data Science in University of Chicago, USA). Soil pH and the soil total carbon (TC) content, soil total nitrogen (TN) content, soil available phosphorus (AP) content, and soil alkali-hydrolyzable nitrogen (AN) content were measured as soil chemical properties. The soil biological properties included the quantities of bacteria, actinomycetes, and fungi. The soil chemical and biological properties showed a strong spatial autocorrelation during the four seasons. “High-high” and “low-low” were the dominant autocorrelation types that were distributed in serious and light subsidence areas. The soil properties decreased as the mining subsidence degree increased. Both the soil TC and soil AP contents were highest in spring, the soil TN content was highest in autumn, and the soil AN content was highest in summer. These results provide a reliable theoretical reference for land reclamation and ecological restoration in mining areas.

Soil Organic Nitrogen Indirectly Enhances Pepper-Residue-Mediated Soil Disease Suppression through Manipulation of Soil Microbiome

Banana Fusarium wilt-suppressive soils are effective against pathogen invasion, yet soil physicochemical factors responsible for conducive or suppressive behavior have not been reported. Here, we investigated the changes in banana biomass, disease incidence (DI), soil culturable microbes and physicochemical properties by incorporating pepper and banana residues into conducive and suppressive soils. Before the incorporation of any residues, the suppressive soil significantly increased banana biomass and decreased DI compared to the conducive soil. The biomass of the suppressive soil was significantly higher than that of the conducive soil after the incorporation of either pepper or banana residues. Compared with the control (CK), the incorporation of pepper residues to both soils significantly reduced DI, while banana residues had the opposite effect. Additionally, both conducive and suppressive soils supplemented with pepper residues significantly reduced the amounts of culturable Fusarium oxysporum and increased the amounts of beneficial Pseudomonas and Bacillus. The pepper residue extracts significantly inhibited the growth of F. oxysporum mycelium. Soil alkali-hydrolyzable nitrogen (AN) responded most strongly to residue application to suppressive soil. The AN factor was significantly and positively correlated with banana biomass; however, there was no direct and significant negative correlation with DI. Further analysis of the results showed that elevated AN content could stimulate the amounts of culturable Bacillus in the soil, and Bacillus antagonized the proliferation of pathogen and thus indirectly and effectively reduced banana DI. In conclusion, soil AN content can indirectly improve the disease suppression ability of pepper-residue-mediated suppressive soil by manipulating the soil microbiome.

Increases in the Methane Uptake of Upland Forest Soil in China Could Significantly Contribute to Climate Change Mitigation

Upland forest soil is an important CH4 sink that plays a key role in climate change mitigation. China features large areas of various types of forest, but spatiotemporal variation in CH4 flux has not yet been clarified. Here, we analyzed variation in CH4 flux and the effects of environmental variables on the CH4 flux of forest in China using in situ observational data. Upland forest soil absorbed CH4 at a rate of 0.24 ± 0.02 g m−2 yr−1. The CH4 uptake rate (0.46 ± 0.10 g m−2 yr−1) of warm temperate deciduous broad-leaved forest was the highest. Soil alkali-hydrolyzable nitrogen was the only factor significantly correlated with CH4 uptake variation among vegetation zones. A break point in CH4 uptake over the study period (from 1997 to 2020) was detected in 2015. CH4 uptake slightly decreased until 2015 and increased after 2015. The mean CH4 uptake of the period after 2015 (0.44 ± 0.07 g m−2 yr−1) was significantly higher than that before 2015 (0.20 ± 0.02 g m−2 yr−1). Atmospheric nitrogen deposition was negatively related to interannual CH4 uptake. Our findings suggest that the CH4 uptake of upland forest soil will continue to increase over the next few decades as China accelerates efforts to achieve its carbon neutrality goal, and this would result in continuous decreases in nitrogen deposition through various pathways.

Bacterial community structure and diversity in the rhizospheric soil of Robinia pseudoacacia and Juniperus sabina planted in iron tailings matrix

Iron tailings matrix is deficient in nutrients, and phytoremediation is one of the effective methods to improve tailings nutrients. The response of phytoremediation to tailings microorganisms remains to be studied. The present study analyzed rhizospheric soil of two kinds of plants bacterial diversity and community structure and their relationship with soil environmental factors. The results indicate that the rhizospheric soil bacteria species of Robinia pseudoacacia and Juniperus sabina were not significantly different from that of bare tailings, but rhizospheric soil bacterial community compositions and abundance were significantly different from that of bare tailings. Canonical correlation analysis (CCA) showed that soil alkali-hydrolyzable nitrogen (AN), soil total nitrogen (TN), and soil organic matter (SOM) were the main environmental factors affecting bacterial community diversity. Spearman's correlation analysis showed that AN, TN, and SOM were significantly positively correlated with the relative abundance of Gemmatimonadetes and Nitrospirae, and were significantly negatively correlated with that of Firmicutes, Fusobacteria, and Bacteroidetes. FAPROTAX function prediction showed that the functional microbial communities of rhizospheric soil of the two plants were significantly different from those of bare tailings. Overall, the findings support an increase of microbial diversity, SOM, and nitrogen in rhizospheric soil of revegetated tailings compared to bare tailings. These results provide theoretical support for the development and application of phytoremediation in abandoned mines.

Arbuscular Mycorrhizal Fungi Promote Gleditsia sinensis Lam. Root Growth under Salt Stress by Regulating Nutrient Uptake and Physiology

Towards the improvement of plant productivity in saline–alkali soils, the application of arbuscular mycorrhizal fungi (AMF) is an intensive topic of research. For this study, three inoculation treatments, namely, autoclaved AMF inocula (CK), Funneliformis mosseae (FM), and Corymbiglomus tortuosum (CT), and four NaCl levels, namely, 0, 50, 100, and 150 mM were established to investigate the growth and physiological responses of mycorrhizal Gleditsia sinensis Lam. root systems to increase salinity through root dry weight, morphology, nutrient content, and physiology, and soil nutrient content. As NaCl levels increased, root dry weight, morphology, and nutrient content under the CK treatment exhibited a downward trend, while FM and CT treatments weakened this trend and significantly improved root dry weight and morphology, which increased by more than 200%. Under high NaCl levels, root activity under the FM treatment was significantly higher than that under the CK, with an average increase of 120.86%. In contrast to the activity of nitrate reductase, niacinamide adenine dinucleotide oxidase activity under CK was significantly less than that in FM and CT treatments. Moreover, inoculation with AMF significantly affected soil alkali-hydrolyzable nitrogen (AN), total nitrogen (TN), and phosphorus (TP), while NaCl had no significant impact on soil nutrients. Further, both soil salinity and mycorrhizal colonization rate had significant direct effects on root growth. However, soil salinity primarily influenced root growth through indirect effects on root nitrogen content, while mycorrhizal colonization rate indirectly impacted root nitrate reductase activity, and root nitrogen and phosphorus content. Our results suggested that the use of suitable AMF (e.g., Funneliformis mosseae) might effectively improve the currently unfavorable situation of economic tree species production on land with saline soils, which may greatly optimize the utility of these areas.

Orychophragmus violaceus-maize rotation increases maize productivity by improving soil chemical properties and plant nutrient uptake

Appropriate use of cover crops and crop rotation in agriculture can contribute to food security and sustainable production. However, the impacts of Orychophragmus violaceus ( O. violaceus ) as rotation cover crop in maize on soil physicochemical properties and crop nutrient uptake have rarely been verified and quantified via field studies. With a conventional wheat ( Triticum aestivum L.)-maize ( Zea mays L.) rotation used as a control, a field experiment was conducted on the North China Plain in 2017–2018 and 2018–2019 to evaluate the dynamic variations in soil chemical properties and maize agronomic indexes and the impacts on maize nutrient uptake and yield under continuous maize and O. violaceus -maize rotation. We observed that rotation of O. violaceus with maize positively impacts soil chemical properties and subsequent maize productivity. Compared to those in the wheat-maize rotation, the mean contents of soil organic matter (SOM), soil alkali–hydrolyzable nitrogen (SAN), soil available phosphorus (SAP), and soil available potassium (SAK) in the O. violaceus -maize rotation increased by 8%, 11%, 13% and 18%, respectively, within the 0–60 cm soil layer, thereby increasing the maize N and P uptake and yield at maturity. According to correlation analysis and path model results, the most powerful direct factor affecting the maize yield was plant nutrient uptake rather than biomass accumulation. The O. violaceus -maize rotation was superior to the wheat-maize rotation and continuous maize in term of SOM, SAN, plant agronomic indexes, and maize nutrient uptake and yield. Overall, O. violaceus -maize is a reasonable rotation system for use on the North China Plain and provides new insight into the mechanisms and processes underlying crop yield and nutrient uptake. • O. violaceus -maize greatly increased soil organic matter and soil available nitrogen. • The maize nutrients uptake was increased at maturity in O. violaceus -maize system. • Replacing wheat or fallow field with O. violaceus increased maize yield by 8%−12%. • The relationship between soil chemical property and maize yield was quantified.

Stoichiometry of C:N:P in the Roots of Alhagi sparsifolia Is More Sensitive to Soil Nutrients Than Aboveground Organs.

The stoichiometry of carbon, nitrogen, and phosphorus (C:N:P) among leaves, stems, and roots reflects trade-offs in plants for acquiring resources and their growth strategy. The widely distributed plant Alhagi sparsifolia is an ideal species to study the ecological stoichiometry in different organs in response to the availability of nutrients and water in the desert ecosystem. However, which response of organs is most sensitive to environmental conditions is still unclear. To answer this question, we collected samples of plants and soils including not only aboveground leaves and stems, but also underground roots and soils from a wide range of arid areas during the growing season. The C, N, P, C:N, C:P, and N:P ratios in leaves, thorns, stems, and roots were derived to explore their relationship as well as their response mechanisms to nutrients and water spanning 1 m deep in the soil. The results showed that the order of N concentration was leaves > thorns > stems > roots, that the concentration of P in the leaves, thorns, and stems was similar, and that their values were higher than those in the roots. First, the C:N ratios in the leaves and stems were significantly positively correlated with the ratio in roots. The C:N ratios in each organ showed a significant relationship with the soil alkali hydrolyzable nitrogen (SAN) above a depth of 60 cm. In addition to SAN, soil available phosphorus (SAP) and soil organic carbon (SOC) affect the C:N ratio in the roots. Second, the C:P and N:P ratios in aboveground organs showed no correlations with the ratios in roots. The C:P and N:P ratios in the leaves and thorns have no relationship with soil nutrients, while the C:P ratio in roots was influenced by SAN and SOC in all soil layers. Finally, the N:P ratios in roots were also affected by nutrients in different soil depths at 0–20 and 60–80 cm. These results illustrate that the roots were more sensitive to soil nutrients than the aboveground parts. Our study of ecological stoichiometry also suggests a novel systematic approach for analyzing the sensitivity of responses of an organ to environmental conditions.

Effects of Different Stand Types on Soil Chemical Properties in Rainy Zone of West China

In order to explore different forest types effects on soil chemical properties, four stand types, namely pure Cunninghamia lanceolata forest, pure Cryptomeria fortunei forest, pure Liriodendron chinense forest and Cryptomeria fortune × Phoebe zhennan mixed forest, were selected as the research objects, and the difference of soil chemical properties and the organic contents of different forest types were analyzed by variance analysis. The results showed that there were significant differences in soil pH, available potassium, total phosphorus, total potassium and total nitrogen among different forest types, but there were no significant differences in available phosphorus, alkali-hydrolyzable nitrogen, and soil organic matter. The soil pH value of the four forest stands was between 4.02 and 5.33, which was acidic, and increased with the increase of soil depth. The contents of soil organic matter, total nitrogen, total phosphorus, alkali-hydrolyzable and available phosphorus in different forests types all decreased with the increase of the soil depth. The 0~10cm total phosphorus content of soil in four different forest stands was higher than that of 10~20 cm. The soil total potassium content of pure C. lanceolata forest, pure C. fortunei forest and pure L. chinense forest all fluctuated up and down with the increase of the soil depth, while the content of C. fortune × P. zhennan mixed forest increased gradually. The contents of soil alkali-hydrolyzable nitrogen and available phosphorus in soil of four forest stands all decreased with the increase of soil depth. The soil available potassium content of pure C. lanceolata forest and pure C. fortunei forest increased first and then decreased, while that of pure L. chinense forest and C. fortune × P. zhennan mixed forest increased gradually. The average phosphorus supply intensity of the four stands at the soil layer of 0~10cm, 10~20cm, 20~40cm and 40~60cm was 2.64%, 2.71%, 2.57% and 2.61%, respectively. Soil K supply intensity of pure L. chinense forest and C. fortunei × P. zhennan mixed forest increased with the increase of soil layer, while that of pure C. fortunei forest first increased and then decreased.

坝上地区不同年代退耕还林生境的草本层植物多样性及影响因子

PDF HTML阅读 XML下载 导出引用 引用提醒 坝上地区不同年代退耕还林生境的草本层植物多样性及影响因子 DOI: 10.5846/stxb201912042631 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（41671181） Herb diversity and its impact factors in different periods from 1970s to 2000s of the returning farmland to forest project in the Bashang Area of North China Author: Affiliation: Fund Project: The National Natural Science Foundation of China (General Program) 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:退耕还林是坝上地区重要的生态修复工程，其生态效益日益受到广泛关注，但针对林下植物多样性保护功能的研究还较少，虽然草本层植被是森林生态系统服务功能的重要指标之一。为评估不同年代退耕还林生境的生物多样性，调查了20世纪70年代至21世纪初共4个年代退耕还林生境的草本层植物多样性，并与弃耕生境及自然林生境进行了对比。为进一步分析林下草本层植物多样性的影响因子，还分析了乔灌层植被、土壤理化性质与林下草本植物多样性的关系。结果显示，不同年代退耕还林的林下草本植物多样性未有显著差异，且均显著低于弃耕生境与自然林生境。草本层物种丰富度对土壤碱解氮含量、灌木层丰富度、灌木层密度具有显著的正响应，Simpson多样性主要与乔木层林木密度呈显著负相关。研究表明，不同年代退耕还林后的林下草本层植物多样性保护功能低于预期，而改善林分空间结构与建设模式可能利于提升其生物多样性保护功能。未来植被修复中需充分权衡生态系统不同服务功能之间的关系，因地制宜，宜林则林，宜草则草，重视自然恢复与多元化生态修复方式，以实现更好生态效益。 Abstract:Returning farmland to forest (RFTF) project is one of the most critical ecological restoration projects in Bashang area, and its ecological service value has been paid more and more attention. Although the herb layer of the artificial forest was a vital indicator to biodiversity conservation and ecosystem services, the relevant researches were much less than expected in this area. We surveyed herb diversities of these forests that were planted in four different periods from 1970s to 2000s of the returning farmland to forest project. Then, the herb diversity of returning farmland to forest habitat was compared with that in abandoned farmland and the natural forests. The effect of the soil character, tree and shrub layer on herb diversity was also analyzed. The results showed that there was no significant difference of herb diversity among different periods of RFTF projects. While all of them were significantly lower than that in the abandoned farmland and the natural forests species richness of herb layers was significantly and positively responded to the content of soil alkali-hydrolyzable nitrogen species richness and densities of shrub. The Simpson diversity of herb layer was negatively responded to the densities of tree. The research revealed that the herb diversities of RFTF habitats might be lower than that we expected, improving vertical spatial structures and construction mode might be helpful to increase the herb diversity level. In order to preferably realize ecological benefits of future ecological restoration projects in Bashang area, it needs to weigh the different relationships of ecological ecosystem service functions, choose ecological restoration methods based on local conditions, and emphasize the importance to natural restoration and diverse restoration methods. 参考文献 相似文献 引证文献

Effects of planting Caragana shrubs on soil nutrients and stoichiometries in desert steppe of Northwest China

Caragana korshinskii shrubs are widely planted in desert steppe of Northwest China to mitigate desert encroachment. Soil nutrients and stoichiometries reflect the cycling of soil organic matter in ecosystems. Thus, there is a dynamic balance between soil nutrients and stoichiometries due to the establishment of Caragana shrubs in this region. Here, soil nutrients and stoichiometries were characterized with different planting densities of Caragana shrubs (HD, high density, 4530 bundle/hm2; MD, mid density, 3670 bundle/hm2; LD, low density, 2560 bundle/hm2) to explore how the planting of Caragana shrubs affects soil nutrients and stoichiometries in desert steppe of Northwest China. The results showed that soil available phosphorus (AP) and soil total phosphorus (TP) had no significant differences between LD and control (CK) (p > 0.05). Further, soil organic carbon (SOC), soil total nitrogen (TN), and soil alkali-hydrolyzable nitrogen (AN) followed the order of HD > MD > LD > CK, indicating that the planting of Caragana shrubs had an increasing effect to soil nutrients, with the exception of AP and TP (p < 0.05), and the increasing effect gradually died down along soil profile. In addition, the planting of Caragana shrubs significantly affected soil stoichiometries. Specifically, soil N/P and C/P gradually increased with soil depth with fluctuation, while soil C/N decreased with soil depth. Besides, soil water content (SW), AP, AN, and SOC had strong positive effects on soil C/N, while they had strong negative effects on soil C/P and N/P, highlighting the importance of soil properties in determining soil stoichiometries. Overall, our results indicated that planting Caragana shrubs can improve levels of soil nutrients, and HD can be considered the optimal planting density for vegetation restoration in desert steppe. Nevertheless, the threshold of the planting density most favorable for the special climates must be identified through further study in this region.

Effects of Biogas Slurry Application on Crop Production and Soil Properties in a Rice–Wheat Rotation on Coastal Reclaimed Farmland

The field experiment of a rice–wheat rotation system was conducted on a coastal reclaimed farmland with different application rates of biogas slurry from a large-scale standardized hoggery. Crop yield, grain quality, and soil properties were examined to determine the appropriate application rate. At the slurry application rates of 480 m3 ha−1 for rice and 9.00–11.25 m3 ha−1 for wheat, grain yields of rice and wheat were 8.9 and 15.7% higher than those under conventional fertilization, respectively. When 840 m3 ha−1 biogas slurry was applied to the rice field, the grain amino acid content was significantly higher than that of conventionally fertilized rice. In the rice–wheat rotation system, under biogas slurry treatments, soil pH and EC did not significantly increase; the contents of soil Pb, Cr, Cu, and Zn were within allowable limits; the contents of soil alkali-hydrolyzable nitrogen were greatly increased and significantly higher than those under conventional fertilization treatment; and the content of soil organic matter had no significant difference with that under no fertilization treatment. Therefore, the recommended application rate of biogas slurry on coastal reclaimed farmland should be 480 and 9.00–11.25 m3 ha−1 for rice and wheat, respectively.

Updating the main vegetable fertilization index system for southern China

ABSTRACTHere, we established abundance and deficiency indices of soil nutrients and fertilization to generate a reference for the optimum fertilization dosage of the main vegetable crops in southern China under current production conditions. We consolidated 3414 field datasets about the main vegetable crops (leafy vegetables, gourds, legumes) in this region between 2010 and 2013. The nutrient abundance and deficiency index method was used to separate soil alkali-hydrolyzable nitrogen, available phosphorus, and available potassium levels into five groups based on relative vegetable yields (range: 50%–95%). Recommended fertilizer dosages were determined by obtaining values for nitrogen, phosphorus, and potassium by fitting optimum dosage against available nutrient content. Required fertilization levels were dependent on soil conditions and crop type. Comparison of the study results showed that available phosphorus and available potassium had significantly improved, whereas alkali-hydrolysable nitrogen in each level was similar.