Spatial Patterns and Controlling Factors of Soil Organic Carbon and Total Nitrogen in the Three River Headwaters Region,China

The alpine ecosystem has great potential for carbon sequestration.Soil organic carbon(SOC)and total nitrogen(TN)are highly sensitive to climate change,and their dynamics are crucial to revealing the effect of climate change on the structure,function,and services of the ecosystem.However,the spatial distribution and controlling factors of SOC and TN across various soil layers and vegetation types within this unique ecosystem remain inadequately understood.In this study,256 soil samples in 89 sites were collected from the Three River Headwaters Region(TRHR)in China to investigate SOC and TN and to explore the primary factors affecting their distribution,including soil,vegetation,climate,and geography factors.The results show that SOC and TN contents in 0-20,20-40,40-60,and 60-80 cm soil layers are 24.40,18.03,14.04,12.40 g/kg and 2.46,1.90,1.51,1.17 g/kg,respectively;with higher concentrations observed in the southeastern region compared to the northwest of the TRHR.One-way analysis of variance reveals that SOC and TN levels are elevated in the alpine meadow and the alpine shrub relative to the alpine steppe in the 0-60 cm soil layers.The structural equation model explores that soil water content is the main controlling factor affecting the variation of SOC and TN.Moreover,the geography,climate,and vegetation factors notably indirectly affect SOC and TN through soil factors.Therefore,it can effectively improve soil water and nutrient conditions through vegetation restoration,soil improvement,and grazing management,and the change of SOC and TN can be fully understood by establishing monitoring networks to better protect soil carbon and nitrogen.

Comparison of Soil Moisture in Different Soil Layers between Three Typical Forests in the Upper Reaches of Lijiang River Basin, Southern China

Throughfall, stemflow, evapotranspiration and infiltration are likely to vary with forest types, and consequently affect soil moisture regimes in different soil layers. In this study, the spatial and temporal characteristics of soil moisture were investigated to understand variations in soil moisture in three typical forests, including Phyllostachys pubescens forest (abbreviated as PPF), Schima superba forest (abbreviated as SSF) and Cunninghamia lanceolata forest (abbreviated as CLF) in the upper reaches of Lijiang River basin in southern China. The results showed that,(1) Litterfall and soil physical properties differed significantly in the three typical forests. Infiltration capacity in SSF was more favorable to soil moisture than in PPF and CLF.(2) Large variations were found in soil moisture at different forest stands and depths. Due to complicated vertical structures, there were obvious differences in soil moisture from the 0-20 cm soil layer to the 50-80 cm soil layer.(3) Average soil moisture in each layer was higher in SSF than in PPF and CLF.(4) Soil moisture in different layers correlated closely with precipitation (P<0.01) and the three typical forests had the same change trends with rainfall during the studying period.(5) In topsoil, soil moisture was influe need by soil properties which were mostly determined by litterfall, while in deep soil, soil moisture was affected by variations of soil characteristics, which were mostly determined by root distribution. This study provides a scie ntific basis for better un dersta nding the relati on ships betwee n forest vegetati on and its hydrological effects, helping to facilitate water resources conservation and achieving wise forest management in the upper reaches of Lijiang River basin.

Improved spatial resolution in soil moisture retrieval at arid mining area using apparent thermal inertia

A surface soil moisture model with improved spatial resolution was developed using remotely sensed apparent thermal inertia（ATI）.The model integrates the surface temperature derived from TM/ETM＋ image and the mean surface temperature from MODIS images to improve the spatial resolution of soil temperature difference based on the heat conduction equation,which is necessary to calculate the ATI.Consequently,the spatial resolution of ATI and SMC can be enhanced from 1 km to 120 m（TM） or 60m（ETM＋）.Moreover,the enhanced ATI has a much stronger correlation coefficient（R^2） with SMC（0.789） than the surface reflectance（0.108） or the ATI derived only from MODIS images（0.264）.Based on the regression statistics of the field SMC measurement and enhanced ATI,a linear regression model with an RMS error of 1.90%was found.

Study on the subgrade deformation under high-speed train loading and water–soil interaction

It is important to study the subgrade characteristics of high-speed railways in consideration of the water–soil coupling dynamic problem,especially when high-speed trains operate in rainy regions.This study develops a nonlinear water–soil interaction dynamic model of slab track coupling with subgrade under high-speed train loading based on vehicle–track coupling dynamics.By using this model,the basic dynamic characteristics,including water–soil interaction and without water induced by the high-speed train loading,are studied.The main factors-the permeability coefficien and the porosity-influencin the subgrade deformation are investigated.The developed model can characterize the soil dynamic behaviour more realistically,especially when considering the influenc of water-rich soil.

塑性支承桩——卸荷减沉桩的概念及其工程应用

在复合桩基的基础上提出了塑性支承桩———卸荷减沉桩的概念 ,并给出了其沉降量计算的方法及工程应用的基本原则 ,工程实践验证了塑性桩概念的正确性和差异沉降控制的可能性 。

Detecting the storage and change on topsoil organic carbon in grasslands of Inner Mongolia from 1980s to 2010s

Soil carbon sequestration and potential has been a focal issue in global carbon research. Under the background of global change, the estimation of the size as well as its change of soil organic carbon（SOC） storage is of great importance. Based on soil data from the second national soil survey and field survey during 2011–2012, by using the regression method between sampling soil data and remote sensing data, this paper aimed to investigate spatial distribution and changes of topsoil（0–20 cm） organic carbon storage in grasslands of Inner Mongolia between the 1980 s and 2010 s. The results showed that：（1） the SOC storage in grasslands of Inner Mongolia between the 1980 s and 2010 s was estimated to be 2.05 and 2.17 Pg C, with an average density of 3.48 and 3.69 kg C·m–2, respectively. The SOC storage was mainly distributed in the typical steppe and meadow steppe, which accounted for over 98% of the total SOC storage. The spatial distribution showed a decreased trend from the meadow steppe, typical steppe to the desert steppe, corresponding to the temperature and precipitation gradient.（2） SOC changes during 1982–2012 were estimated to be 0.12 Pg C, at 7.00 g C·m–2·yr–1, which didn＇t show a significant change, indicating that SOC storage in grasslands of Inner Mongolia remained relatively stable over this period. However, topsoil organic carbon showed different trends of carbon source/sink during the past three decades. Meadow steppe and typical steppe had sequestered 0.15 and 0.03 Pg C, respectively, served as a carbon sink; while desert steppe lost 0.06 Pg C, served as a carbon source. It appears that SOC storage in grassland ecosystem may respond differently to climate change, related to vegetation type, regional climate type and grazing intensity. These results might give advice to decision makers on adopting suitable countermeasures for sustainable grassland utilization and protection.