基于变量优选与机器学习的干旱区湿地土壤盐渍化数字制图

土壤盐渍化是导致土壤退化和生态系统恶化的主要原因之一，对干旱区的可持续发展构成主要威胁。为了尽可能精确地监测土壤盐渍化的空间变异性，该研究收集新疆艾比湖湿地78个典型样点，其中选取54个样本作为训练集，24个样本作为独立验证集。基于Sientinel-2 多光谱传感器（Multi-Spectral Instrument，MSI）、数字高程模型（Digital Elevation Model，DEM）数据提取3类指数（红边光谱指数、植被指数和地形指数），经过极端梯度提升（Extreme Gradient Boosting，XGBoost）算法筛选有效特征变量，构建了关于土壤电导率（Electrical Conductivity，EC）的随机森林（Random Forest，RF）、极限学习机（Extra Learning Machine，ELM）和偏最小二乘回归（Partial Least Squares Regression，PLSR）预测模型，并选择最优模型绘制了艾比湖湿地盐渍化分布图。结果表明：优选的红边光谱指数基本能够预测EC的空间变化；红边光谱指数与植被指数组合建模效果总体上优于其与地形指数的组合，3类指数组合的建模取得了较为理想的预测精度，其中RF模型表现最优（验证集R2=0.83，RMSE=4.81 dS/m，RPD=3.11）；在整个研究区内，中部和东部地区土壤盐渍化程度尤为严重。因此，XGBoost所筛选出的环境因子结合机器学习算法可以实现干旱区土壤盐渍化的监测。     

Dynamics of nitrogen translocation from mature leaves to new shoots and related gene expression during spring shoots development in tea plants (Camellia sinensis L.)

The contribution of N remobilization is crucial for new shoots growth and quality formation during spring tea shoots development. However, the translocation mechanism of N from source leaves to sink young shoots is not well understood. In the present study, ¹⁵N urea was applied to mature tea leaves one week before bud break to track N remobilization in a field experiment. The dynamic changes in plant ¹⁵N abundance, contents of amino acids, and the expression levels of genes related to N metabolism and translocation were followed during the 18‐d development of new spring shoots until three expanding young leaves. The results showed that during the growth of new shoots the amount of ¹⁵N in the shoots increased, whereas the N_dff (N derived from ¹⁵N‐urea) in mature leaves decreased, showing that the foliar‐applied N in mature leaves was readily exported to new shoots. This process was found to be accompanied by decline of chlorophylls. In the mature leaves, expression CsATG18a and CsSAG12 involved in autophagy was dramatically induced (> 4‐fold) at approximately nine days after the bud breaking. The genes involved in the transformation of amino acids, including primarily CsGDH2, CsGDH4, CsGLT3, CsGS1;3, and CsASN2 were upregulated by > 3‐fold after bud breaking. The expression levels of CsATG8A, CsATG9, CsSAG12, CsGS1;1, CsGDH1, and CsAAP6 correlated negatively with the N_dff in mature leaves, but positively with ¹⁵N amount and total N amount in new shoots, suggesting these genes played important roles in N export from mature leaves. In the new shoots, the expression of most genes showed two defined peaks, one on six days and one on 12 days after bud breaking. The expression of CsGS2, CsASN3, CsGLT1, and CsAAP4 positively correlated with the ¹⁵N amount and total N amount in new shoots. These genes might be involved in the transport and re‐assimilation of N from mature leaves. The overall results demonstrated that the translocation of ¹⁵N from mature leaves to new spring shoots was regulated by the genes involved in autophagy, protein degradation, amino acid transformation and transport.     

Arbuscular mycorrhizal-like fungi and glomalin-related soil protein drive the distributions of carbon and nitrogen in a large scale

Purpose

Arbuscular mycorrhizal-like fungi (AM-like fungi) are crucial for ecosystem functioning and soil organic matter (SOM) is an indicator of soil quality. However, the spatial distribution of arbuscular mycorrhizal-like fungi, glomalin-related soil protein (GRSP) and SOM in a large scale is still unclear. The objectives of this study were to investigate the spatial distribution of SOM, arbuscular mycorrhizal-like fungi and GRSP, and reveal the potential relationship among them in a large scale across China.

Materials and methods

Soil samples (different in vegetation type, climate, and soil variables) were collected from 26 sites in a large scale across China. The soil properties including pH, total carbon (TC), total nitrogen (TN), and SOM were determined. Quantitative PCR amplification of the 18S rRNA gene was conducted to evaluate the abundance of arbuscular mycorrhizal-like fungi. The contents of easily extractable GRSP (EE-GRSP), difficultly extractable GRSP (DE-GRSP), and total GRSP (T-GRSP) were measured.

Results and discussion

Arbuscular mycorrhizal-like fungi abundance was significantly affected by the vegetation type and dramatically correlated with the soil TN and mean annual precipitation (MAP). EE-GRSP and DE-GRSP were more associated with the TC and TN content, respectively. The abundance of arbuscular mycorrhizal-like fungi significantly but weakly correlated with the T-GRSP and EE-GRSP. The SOM content positively correlated with the DE-GRSP and T-GRSP. Those results suggested that the arbuscular mycorrhizal-like fungi are a larger contributor to regulating the content of GRSP, which is an important indicator of the soil organic carbon pool.

Conclusions

Our results indicated that arbuscular mycorrhizal-like fungi abundance has a greater contribution to driving the distribution of soil C and N in a large scale by affecting the content of glomalin-related soil protein.

     

Thermal effects on water retention behaviour of unsaturated collapsible loess

Journal of Soils and Sediments - Temperature has a significant influence on water retention curve (WRC) because temperature affects surface tension of water and volumetric behaviour of soil....     

Effects of different long-term cropping systems on phosphorus adsorption and desorption characteristics in red soils

Journal of Soils and Sediments - Phosphorus (P) fertilizer has been applied in regions with red soils to ensure high crop yield. However, the supply of bioavailable P for crop plants is...     

Remediation of saline-sodic soil using organic and inorganic amendments: physical,chemical, and enzyme activity properties

Purpose

Crops grow poorly in saline-sodic soils, and the productivity of these soils can be dramatically improved with proper amendments. Current research mainly focuses on either organic or inorganic soil amendments, whereas few studies address options of combining organic and inorganic amendments. The objective of this study was to develop new organic and inorganic soil amendments which can lower the soil pH, replace sodium, and improve soil structure.

Materials and methods

Polyhalite (PL), microporous potassium-silicon-calcium mineral fertilizer (MF), furfural residue (FR), and fulvic acid (FA) were mixed with four different ratios to produce organic and inorganic soil amendments: PLFR, PLFA, MFFR, and MFFA. And their optimum mixing ratios were determined by comparing the potassium, calcium concentrations, and pH of filtrate after dissolution. Then, a leaching experiment was conducted by packing mixtures (mass ratio of soil to amendment = 219:1, equivalent to 13 t/hm²) of the saline-sodic soil with each one of these amendments plus two contrasts, gypsum (GP), and no amendment (CK). And the remediation effect was compared by pH, EC, ESP, texture, organic recombination degree of clay, saturated hydraulic conductivity, water-stable aggregates fraction, and enzyme (urease, alkaline phosphatase, and catalase) activities of soil.

Results and discussion

After four times leaching experiment, soil treated with PLFR had lower pH and 25.86% lower exchangeable sodium than untreated soils. The water-stable small macroaggregate fractions and saturated hydraulic conductivity of the MFFR-treated soils were significantly increased by 133% and 31%, respectively. Also, the total soil and heavy fraction organic carbons of the soils treated with MFFR in addition to its alkaline phosphatase activity were all significantly higher than the other treatments.

Conclusions

The results revealed that MFFR has more potential as a soil amendment to improve soil structure and quality and thus help in the development and use of saline-sodic lands for agriculture.

     

A chronosequence study of purple paddy soils with respect to improving ammonium and potassium fertilization management

Journal of Soils and Sediments - Purple paddy soils cover about 66% of the paddy soils in Sichuan Basin. Complex interactions made the effects of potassium fertilizer application on NH4+ adsorption...     

Effects of soil moisture content on CO2 triggered soil physicochemical properties in a near-surface environment

Journal of Soils and Sediments - Carbon capture and storage (CCS) has been frequently discussed as a strategy for meeting CO2 emission reduction and its targets. However, some critical issues have...     

Biochar addition mitigates nitrogen loss induced by straw incorporation and nitrogen fertilizer application

Biochar has been shown to be potentially beneficial for enhancing yields and soil properties, and diminishing nitrogen (N) losses. However, it remains unclear how biochar regulates soil carbon (C) and N to mitigate N losses induced by straw mixing with N fertilizer in dryland soils. Therefore, we investigated the effects of straw mixing (S₁), S₁ with biochar (SB) and no straw inputs (S₀), and routine urea application rates (N₁) and 70% of routine rates (N_0.7) on yields and N losses, and identify the relationship between N losses and soil C and N compounds. Results showed that N_0.7 and N₁ were suitable for the maize and wheat seasons, respectively, contributing to mitigating N losses without reducing crop yields. Moreover, in the maize season, N_0.7-SB significantly mitigated the straw-induced NH₃-N and N₂O-N emissions by 106% and 81%, respectively. In the wheat season, N₁-SB reduced the straw-induced NH₃-N and N₂O-N emissions by 35% and 66%, respectively. In addition, N_0.7-SB sharply reduced soil inorganic N (SIN) storage in the maize season. Furthermore, the NH₃-N and N₂O-N emission rates were negatively correlated with dissolved organic carbon/SIN content (0–20 cm) (DOC/SIN_0-20). N losses (N₂O-N and NH₃-N emissions and SIN storage) were positively correlated with SIN_0-20, but negatively correlated with soil organic carbon / SIN_0-20 (SOC/ SIN_0-20). This study provides further evidence that biochar with an appropriate N application rate decreased SIN_0-20 and increased DOC/SIN_0-20, thus reducing SIN storage and the straw-induced gaseous N emissions without decreasing crop yields.     

基于云服务的棚室蔬菜智能终端系统设计与实现——以黑龙江省为研究案例

棚室蔬菜产业在黑龙江省农业转方式、调结构和供给侧改革中占有重要的战略地位。黑龙江省棚室蔬菜生产规模近年来发展较快,技术支撑需求也与日俱增。本研究针对黑龙江省棚室蔬菜发展规模与技术服务支撑能力不匹配的现状,提出了基于云服务的棚室蔬菜智能终端系统及关键技术的实现方法。本研究以专家服务为主、数据挖掘技术为辅,以物联网设备为感知手段、以智能手机为用户终端,利用云服务对知识、资源、物联网数据的整合配置能力,提供蔬菜专家及棚室蔬菜用户对信息获取、存储、分析和决策的高效解决方案。本研究的部分内容已在黑龙江省农业科研部门、企业、蔬菜合作社、农户等不同用户群体中实验应用,能够为专家提供棚室蔬菜生产环境的远程问诊手段,适用于各类棚室蔬菜应用场景。本研究还提出了对大规模应用场景下的技术解决方案建议,可在全国的棚室蔬菜生产中推广应用,实现更广泛高效的专家技术服务支撑。