Kaihua Liao

• PhD
• Fellow at Chinese Academy of Sciences

The identification of representative soil moisture sampling sites is important for the validation of remotely sensed mean soil moisture in a certain area and ground-based soil moisture measurements in catchment or hillslope hydrological studies. Numerous approaches have been developed to identify optimal sites for predicting mean soil moisture. Eac...

China's sustained air quality improvement is hindered by unregulated ammonia (NH3) emissions from inefficient nitrogen management in smallholder farming. Although the Chinese government is promoting a policy shift to large-scale farming, its benefits when integrated with nitrogen management remain unclear. Here we fill this gap using an integrated...

Microwave remote sensing has great potential for capturing surface soil moisture (SSM) but suffers from its coarse spatial resolution. In this study, we combined the disaggregation based on physical and theoretical change (DISPATCH) and random forest (RF) approaches to downscale microwave-based SSM in the Yangtze River Delta region, China. Results...

The rock fragment (RF) has been widely observed in the soil solum or on the soil surface. It regulates soil hydrological processes (SHPs) and thus has great impacts on soil and water conservation. However, responses of SHPs to RF characteristics (position, content, coverage area, mulching thickness, and size) remain unclear. Based on the dataset ex...

The dynamics of soil water dissolved CO2 and N2O are important in determining the fates of soil CO2 and N2O. However, related mechanisms and processes have been rarely revealed. In this study, storages and leaching losses of soil water dissolved CO2 and N2O were investigated on the tea garden (TG) and bamboo forest (BF) hillslopes. Soil water stora...

As the largest terrestrial organic carbon pool, soil organic carbon (SOC) plays an important role in the global carbon cycle, but it is easily affected by land use and climate change. The Huang-Huai-Hai Plain (HHHP) in China, which is dominated by dry farming, is experiencing rapid farmland loss and gain (farmland use transition), which may cause d...

Purpose Inconsistent controlling factors of soil water content (SWC) spatial variation across regions and spatial scales have been acknowledged in previous studies. However, universal principles explaining these inconsistencies are still needed to be explored. The main aim of this study was to conclude the universal principles across regions and sc...

Conservation tillage, defined as no-till with/without straw stubble covering, reduced tillage, or minimum tillage in this study, is widely used to mitigate the negative effects of intensive tillage. Achieving sustainable agricultural development and eco-environmental protection requires a deeper understanding of the effect of conservation tillage o...

Greenhouse gases dissolved in the soil water and transported through subsurface flow were poorly understood in comparison to their emissions at the soil-atmosphere interface. In this study, leachate CO2 and N2O concentrations were monitored on a tea garden (TG) hillslope (cultivated) and a bamboo forest (BF) hillslope (naturally vegetated) from Sep...

Identification of hot spots and hot moments (HSHMs) in regard to soil nitrogen (N) losses has received public attention. Soil nitrous oxide (N2O) emissions and mineral N leaching under varied annual precipitation were simulated with the DayCent model in a mixed landscape (tea garden, bamboo forest and coniferous and broad-leaved mixed forests). The...

Accurate surface soil moisture (SSM) information is essential for various investigations and implications in agronomy, hydrology, meteorology and ecology. In this study, an improved SSM product from 2015 to 2018 was generated by combining the triple collocation (TC) method and entropy value (EV) method (TC&EV) to fuse the European Space Agency Clim...

The saturated hydraulic conductivity (Ksat) is a key soil hydraulic property governing agricultural production. However, the influence of the conversion from the conventional tillage (CT) to conservation tillage (CS; including no tillage, NT, and reduced tillage, RT) on the Ksat of soils is not well understood and still debated. In this study, we a...

Assessing accuracies of satellite soil moisture (SM) products in areas with strong anthropogenic activities, abundant precipitation, and dense vegetation is important but limited. In this study, performances of nine satellite SM products, including the European Space Agency Climate Change Initiative (ESA CCI), and the ascending and descending produ...

Although the frequency and intensity of seasonal drought and wetness are increasing under climate change background, their effects on soil nitrate nitrogen (NO3⁻-N) leaching have remained unclear. In this study, validated by the field data on a typical tea garden hillslope in Taihu basin, China, the Decomposition-Denitrification (DNDC) model was us...

Excess phosphorus (P) in freshwater lakes is a global challenge due to its potential cause of harmful algal blooms threating drinking water safety. However, quantifying the P sources for a specific site in a large lake is extremely challenging due to the complex interaction between internal and external P loading to surface water. To address this c...

Soils with a significant proportion of rock fragments (RFs, with diameter >2 mm) are widely distributed in terrestrial ecosystems. However, a lack of quantitative information about RF characteristics restricts our ability to explain and predict the related soil carbon (C) and nitrogen (N) processes, and induces biases of C and N investigations in a...

Rock fragments (RFs, material particles with diameter > 2 mm) are widely distributed in soils over globe. However, spatial pattern of RF content (RFC) and its roles on hydrological and ecological patterns have remained unclear at the global scale. In this study, based on the collected global datasets, we investigated the relationships between mean...

The saturated hydraulic conductivity (Ksat) is a key soil hydraulic property governing agricultural production. However, the influence of conversion from conventional tillage (CT) to conservation tillage (CS) (including no tillage (NT) and reduced tillage (RT)) on Ksat of soils is not well understood and still debated. In this study, we applied a g...

The nitrogen-15 (15N) natural abundance composition (δ15N) in soils or plants is a useful tool to indicate the openness of ecosystem N cycling. This study aimed to evaluate the influence of the experimental warming on soil and plant δ15N. We applied a global meta-analysis method to synthesize 79 and 76 paired observations of soil and plant δ15N fro...

Soil nitrogen (N) loss is a part of N biogeochemical processes, which plays an important role in the agricultural, ecological and environmental management. Because it is difficult to assess the temporal and spatial changes of different N forms in leachates by field measurement methods, conceptual and physical models are usually used to describe soi...

Rock fragments (RFs, mineral particles with diameter > 2 mm) can substantially influence soil carbon (C) and nitrogen (N) cycles through different physical mechanisms. These physical mechanisms include changing soil hydraulic parameters (vSH) by reducing fine earth bulk density (vSHBD) and volume (vSHVo), and affecting soil C and N stocks (vCN) by...

The 15N natural abundance composition (δ15N) in soils or plants is a useful tool to indicate the openness of ecosystem N cycling. This study was aimed to evaluate the influence of the global warming on soil and plant δ15N. We applied a global meta-analysis method to synthesize 79 and 76 paired observations for soil and plant δ15N from 20 published...

(1) Background: Simulation of soil water infiltration process and analysis of its influencing factors are important for water resources management. (2) Methods: In this study, the relative contributions of the soil water retention characteristics (SWRC) estimation, initial water content, and constant pressure head at upper boundary to the cumulativ...

In order to explore the water level variations of Caizi Lake under river-lake isolation, the monthly water level of the Chefuling station in Caizi Lake from 1989 to 2018 and the daily water level, rainfall and flow of local hydrological stations in 2018 were analyzed by using the Mann-Kendall trend test and wavelet analysis. Results showed that the...

Variations in and control of soil total organic carbon (TOC), nitrogen (TN) and phosphorus (TP) and their stoichiometric ratios (C:N, C:P and N:P) are critical in agricultural nutrient management. This study examined the scale‐dependent effects of environmental factors on these soil properties under two contrasting land use types (tea vs. bamboo) a...

The coarse spatial resolutions of satellite-based soil moisture (SM) products restrict their applications at smaller spatial scales. In this study, the monthly European Space Agency Climate Change Initiative SM data (ESA CCI SM) from 2000 to 2016 was downscaled from 25- to 1-km resolution in the Taihu Lake Basin, a typical humid area with complex t...

Background and aims: The effects of climate factors and rock fragment content (RFC) on soil nitrous oxide (N 2 O) emission and mineral N leaching can be important in reducing N losses in different agroecosystems. This study aimed to analyze and quantify the intertwined effects of precipitation intensity, temperature, RFC, and land use on these two...

Pedotransfer functions were often applied to predict the soil water contents at field capacity (FC) and permanent wilting point (PWP), which are the key parameters used in the soil nitrogen (N) biogeochemical models for simulating the nitrate (NO3--N) leaching. However, the PTF prediction uncertainty was often ignored. In addition, the uncertainty...

Due to the economic benefits, land use change (e.g. deforest to tea or fruit plantation) has been widely occurred in the south-eastern hilly area of China. This may stimulate serious soil nitrogen (N) losses due to large fertilizer inputs (about 1–2 times of that in regular rice-wheat rotation). Therefore, we investigated the soil N2O fluxes and le...

The near‐surface soil water content (SWC) can reflect the agricultural drought levels. In addition, understanding the historical trends of near‐surface SWC change in China is an important step in combating climate change. The monthly near‐surface SWC data set during 1988‐2016 published by the European Space Agency Climate Change Initiative were use...

Spatial patterns of land use types (mixed forest: MF, tea garden: TG, bamboo forest: BF) in a mountainous area with rapid agricultural land development were optimized to reduce NO3⁻-N leaching and N2O emission in this study. Firstly, a process-oriented biogeochemical model (Denitrification Decomposition, DNDC) was calibrated and validated on repres...

The development of a theoretical method for estimating the wetting branch of soil water retention curve (SWRC) is required for the knowledge of the soil infiltration process. The aim of this study was to derive the theoretical functions to represent the wetting branch of SWRC based on the Jensen method, and then compare the Jensen method and Kool a...

Spatio‐temporal variations of nitrate‐nitrogen ( NO3 - ‐N) leaching is driven by both soil hydrology and biogeochemistry. However, the widely used soil hydrology and biogeochemistry models have their weaknesses in simulating soil N cycling and soil water movement processes, respectively. In this study, we proposed an alternative approach by simply...

This study was conducted on a stony‐soil hillslope that severely eroded due to land use change from bamboo to tea. First, three approaches were used to extract soil hydraulic properties and then inputted into the Denitrification–Decomposition model for simulations. The Denitrification–Decomposition model defaults and ROSETTA pedotransfer function w...

Core Ideas Soil hydraulic properties from saturation to oven dryness are needed to simulate soil water movement. A new soil hydraulic model was compared with the classic van Genuchten–Mualem models. The new model with different fitted parameters was more efficient than the van Genuchten–Mualem models. Soil water retention characteristics and hydra...

The unsaturated soil hydraulic conductivity accounting for film flow is important for understanding soil hydrological and biological processes, especially in arid and semi‐arid regions. Recently, a theoretically based hydraulic conductivity model was developed to describe the hydraulic conductivity as a function of water content. We have used this...

Cation exchange capacity (CEC) has diverse applications from soil classification and management to agricultural/environmental simulations. Direct measurement of CEC is difficult. The objective of this study was to investigate the effect of calibration dataset size on accuracy and validity of soil CEC pedotransfer functions (PTFs) derived for select...

The humid region of Southeast China is one of the most prominent areas of environmental problems. Eutrophication of water bodies is a major problem that hampers the economic and social developments in the region. Especially in recent years, affected by government policies and market forces, the development of hilly and mountainous areas was intensi...

Soil moisture variations in space and time are critical in ecological, hydrological, pedological and environmental studies. This study used fractal analysis to detect the spatio-temporal variability of soil moisture on two contrasting land use hillslopes in the hilly area of Taihu Lake Basin of China. Surface (0–20 cm) soil moisture data from Janua...

The ROSETTA model has routinely been applied to predict the soil hydraulic properties for simulating the water flow at the hillslope scale. However, the uncertainties in water flow simulations are substantial due to the soil heterogeneity and ROSETTA model structure. In order to reduce these uncertainties, this study used the HYDRUS-2D and ensemble...

Spatio-temporal variability of soil moisture (θ) is a challenge that remains to be better understood. A trade-off exists between spatial coverage and temporal resolution when using the manual and real-time θ monitoring methods. This restricted the comprehensive and intensive examination of θ dynamics. In this study, we integrated the manual and rea...

Topsoil (0–20 cm) data of 25 997 sites were analyzed across five land uses in the Jiangsu Province of China. The results showed that the residential/industrial land stored the highest amount of soil organic carbon (SOC) among all the land uses. The polynomial model can best describe the relationship between SOC density (SOCD) and pH, showing that S...

Purpose Spatial prediction of near-surface soil moisture content (NSSMC) is necessary for both hydrologic modeling and land use planning. However, uncertainties associated with the prediction are always neglected and lack of quantitative analysis. The objective of this study was to investigate the influences of different sources of uncertainty on N...

Knowledge of the generation of subsurface flow for hillslopes is important for controlling agricultural nonpoint nutrient losses. This study used a physically based hillslope hydrologic model HYDRUS-2D to assess the sensitivity of simulated subsurface flow to the interactions between precipitation, soil texture and land use. Soil moisture data from...

Knowledge of soil moisture temporal stability and its controlling factors is important for hydrological and environmental management decisions. This study analyzed the influences of soil and terrain on soil moisture temporal stability (relative difference of soil moisture—δ and standard deviation of δ − Sδ) on two contrasting land use hillslopes [t...

Soil water temporal stability is subject to spatial variation, which influences the prediction of mean soil water status on a hillslope. However, estimation of the spatial pattern of soil water temporal stability and quantification of the uncertainties associated with the predictions are often ignored. In this study, volumetric soil water contents...

Soil cation exchange capacity (CEC), which is considered to be an indicator of buffering capacity, is an important soil attribute that influences soil fertility but is costly, time-consuming and labour-intensive to measure. Pedotransfer functions (PTFs) have routinely been used to predict soil CEC from easily measured soil properties, such as soil...

Agricultural, environmental and ecological modeling requires soil cation exchange capacity (CEC) that is difficult to measure. Pedotransfer functions (PTFs) are thus routinely applied to predict CEC from easily measured physicochemical properties (e.g., texture, soil organic matter, pH). This study developed the support vector machines (SVM)-based...

Soil moisture and its spatial pattern are important for understanding various hydrological, pedological, ecological and agricultural processes. In this study, data of rainfall and soil moisture contents at different depths (10 cm, 20 cm, 40 cm and 60 cm) in forestland and vegetable plot in the Taihu Lake Basin, China were monitored and analyzed for...

Soil moisture is one of the most important parameters controlling various critical zone processes including energy balance and nutrient cycling. However, hillslope soil moisture variation and its response to rainfall are not fully understood yet. Through real-time monitoring systems, mechanisms of soil moisture response to rainfall were investigate...

Assessing and managing the spatial variability of hydropedological properties are important in environmental, agricultural, and geological sciences. The spatial variability of soil apparent electrical conductivity (ECa) measured by electromagnetic induction (EMI) techniques has been widely used to infer the spatial variability of hydrological and p...

Hydrological, environmental and ecological modellers require van Genuchten soil-water retention parameters that are difficult to measure. Pedotransfer functions (PTFs) are thus routinely applied to predict hydraulic parameters (θs, ln(α) and n) from basic soil properties (e.g. bulk density, soil texture and organic matter content). This study inves...

Understanding the spatial distribution and variability of soil texture is essential for land use planning and other activities related to agricultural management and environmental protection. This study was conducted to evaluate Landsat Enhanced Thematic Mapper (ETM) remote sensing data as auxiliary variables for spatial estimation of surface soil...

This study tested the ability of four published pedotransfer functions (PTFs) (including ROSETTA, RAWLS, CAMPBELL and VAUCLIN) to predict unsaturated hydraulic conductivity for 56 sandy soil samples from the UNSODA database. Different PTFs for the estimation of saturated hydraulic conductivity were also evaluated in this study. Results showed that...

Pedotransfer functions are commonly used to predict soil hydraulic characteristics. However, the analysis of prediction uncertainty is often ignored by researchers. In an attempt to reduce the prediction uncertainty and to improve the applicability of pedotransfer functions, two existing pedotransfer functions are used to predict the spatial distri...

Prediction of the field capacity and the permanent wilting point is of importance due to actual needs of hydrological model for solving large scale soil moisture problems. The aim of this study is to develop pedotransfer functions for predicting field capacity and permanent wilting point through a new methodology based on artificial neural network...

Accurate prediction of soil moisture spatial–temporal variations remains critical in agronomic, hydrological, pedological, and environmental studies. Traditional approaches of soil moisture monitoring and prediction have limitations of being time-consuming, labour-intensive, and costly for direct field observation; and having low spatial resolution...

A total of 107 soil samples were taken from the city of Qingdao, Shandong Province, China. Soil water retention data at 2.5, 6, 10, 33, 100, 300, and 1500 kPa matric potentials were measured using a pressure membrane apparatus. Multiple linear regression (MLR) was used to develop pedotransfer functions (PTFs) for single point estimation and van Gen...

As soil cation exchange capacity (CEC) is a vital indicator of soil quality and pollutant sequestration capacity, a study was conducted to evaluate cokriging of CEC with the principal components derived from soil physico-chemical properties. In Qingdao, China, 107 soil samples were collected. Soil CEC was estimated by using 86 soil samples for pred...

This paper establishes soil water movement model of typical farmland in Chanzhi Reservior irrigation area based on long-time field experiment. The results indicate that leakage of soil water is almost serious under conventional irrigation mode, precipitation and irrigation show positive correlation with water leakage and field evapotranspiration. W...