Future changes in precipitation and water availability over the Tibetan Plateau projected by CMIP6 models constrained by climate sensitivity

Precipitation projections over the Tibetan Plateau(TP)show diversity among existing studies,partly due to model uncertainty.How to develop a reliable projection remains inconclusive.Here,based on the IPCC AR6–assessed likely range of equilibrium climate sensitivity(ECS)and the climatological precipitation performance,the authors constrain the CMIP6(phase 6 of the Coupled Model Intercomparison Project)model projection of summer precipitation and water availability over the TP.The best estimates of precipitation changes are 0.24,0.25,and 0.45 mm d^(−1)(5.9%,6.1%,and 11.2%)under the Shared Socioeconomic Pathway(SSP)scenarios of SSP1–2.6,SSP2–4.5,and SSP5–8.5 from 2050–2099 relative to 1965–2014,respectively.The corresponding constrained projections of water availability measured by precipitation minus evaporation(P–E)are 0.10,0.09,and 0.22 mm d^(−1)(5.7%,4.9%,and 13.2%),respectively.The increase of precipitation and P–E projected by the high-ECS models,whose ECS values are higher than the upper limit of the likely range,are about 1.7 times larger than those estimated by constrained projections.Spatially,there is a larger increase in precipitation and P–E over the eastern TP,while the western part shows a relatively weak difference in precipitation and a drier trend in P–E.The wetter TP projected by the high-ECS models resulted from both an approximately 1.2–1.4 times stronger hydrological sensitivity and additional warming of 0.6℃–1.2℃ under all three scenarios during 2050–2099.This study emphasizes that selecting climate models with climate sensitivity within the likely range is crucial to reducing the uncertainty in the projection of TP precipitation and water availability changes.

A study of the soil water potential threshold values to trigger irrigation of ‘Shimizu Hakuto’ peach at pivotal fruit developmental stages

Water management is an important practice that affects fruit size and quality.Effective implementation of irrigation scheduling requires knowledge of the appropriate indicators and thresholds,which are established manly based on the effects of water deficits on final fruit quality.Few studies have focused on the real-time effects of water status on fruit and shoot growth.To establish soil water potential (ψ_(soil)) thresholds to trigger irrigation of peach at pivotal fruit developmental stages,photogrammetry,^(13)C labelling,and other techniques were used in this study to investigate real-time changes in stem diameter,fruit projected area,net leaf photosynthetic rate (P_(n)),and allocation of photoassimilates to fruit under soil water potential conditions ranging from saturation to stress in 6-year-old Shimizu hakuto’peach.Stem growth,fruit growth,and P_n exhibited gradually decreasing sensitivity to water deficits during fruit developmental stages I,II,and III.Stem diameter growth was significantly inhibited whenψ_(soil)dropped to-8.5,-7.6,and-5.4 k Pa,respectively.Fruit growth rate was low,reaching zero when theψ_(soil)was-9.0 to-23.1,-14.9 to-21.4,and-16.5 to-23.3 k Pa,respectively,and P_ndecreased significantly when theψ_(soil)reached-24.2,-22.7,and-20.4 kPa,respectively.In addition,more photoassimilates were allocated to fruit under moderateψ_(soil)conditions (-10.1 to-17.0 k Pa) than under otherψ_(soil)values.Our results revealed threeψ_(soil)thresholds,-10.0,-15.0,and-15.0 kPa,suitable for triggering irrigation during stages I,II,and III,respectively.These thresholds can be helpful for controlling excessive tree vigor,maintaining rapid fruit growth and leaf photosynthesis,and promoting the allocation of more photoassimilates to fruit.

Plastic mulch increases dryland wheat yield and water-use productivity,while straw mulch increases soil water storage

Amplifying drought stress and high precipitation variability impair dryland wheat production.These problems can potentially be minimized by using plastic mulch(PM)or straw mulch(SM).Therefore,wheat grain yield,soil water storage,soil temperature and water-use productivity of PM and SM treatments were compared with no mulch(CK)treatment on dryland wheat over a period of eight seasons.Compared to the CK treatment,PM and SM treatments on average significantly increased grain yield by 12.6 and 10.5%,respectively.Compared to the CK treatment,SM treatment significantly decreased soil daily temperature by 0.57,0.60 and 0.48℃ for the whole seasons,growing periods and summer fallow periods,respectively.In contrast,compared to the CK treatment,PM treatment increased soil daily temperature by 0.44,0.51 and 0.27℃ for the whole seasons,growing periods and summer fallow periods,respectively.Lower soil temperature under SM allowed greater soil water storage than under PM.Soil water storage pre-seeding was 17%greater under the SM than under the PM treatment.Soil water storage post-harvest was similar for the PM and SM treatments,but evapotranspiration was 4.5%higher in the SM than in the PM treatment.Consequently,water-use productivity was 6.6%greater under PM than under the SM treatment.Therefore,PM treatment increased dryland wheat yield and water-use productivity,while straw mulch increased soil water storage.

Water retention behavior and shear strength of artificially cemented granite residual soil subjected to free drying

Artificially cemented soils have been widely used as filling materials in highway and railway construction.The shear strength evolution of filling materials upon moist variation can determine the stability of subgrade and embankments.This study conducted water retention tests,MIP tests,and multi-stage triaxial shear tests on cement-treated granite residual soil(GRS)to determine its water retention curve(WRC)upon free drying,pore structure,and peak shear strength qf,respectively.The water retention behavior and shear strength evolution upon free drying were modeled based on the dual-porosity structure of cement-treated GRS and the effective stress principle,respectively.Results show that the drying-WRC is bimodal and higher cement dosage yields a more severe decrease in the water retention capacity within a specific suction range.For a given confining pressure,the peak shear strength qf increased with increasing cement dosage or suction value s.The peak shear strength qf also solely depends on the suction value in the peak stress state.In addition,the cement-treated GRS has a bimodal pore size distribution curve,and its macro-and micro-void ratios remain almost unchanged after free drying.The bimodal drying-WRC of the cement-treated GRS can be modeled by differentiating the water retention mechanisms in macro-and micro-pores.Moreover,using the macro-pore degree of saturation as the effective stress parameterχ=S_(rM),the q_(f)–p′_(f)relationship(where p′_(f)is the effective mean pressure at failure)under various suction and stress conditions can be unified,and the q_(f)–s relationships at various net confining pressuresσ_(3),net can be well reproduced.These findings can help design subgrade and embankments constructed by artificially cemented GRS and assess their safe operation upon climate change.

Effects of gravel on the water absorption characteristics and hydraulic parameters of stony soil

The eastern foothills of the Helan Mountains in China are a typical mountainous region of soil and gravel,where gravel could affect the water movement process in the soil.This study focused on the effects of different gravel contents on the water absorption characteristics and hydraulic parameters of stony soil.The stony soil samples were collected from the eastern foothills of the Helan Mountains in April 2023 and used as the experimental materials to conduct a one-dimensional horizontal soil column absorption experiment.Six experimental groups with gravel contents of 0%,10%,20%,30%,40%,and 50%were established to determine the saturated hydraulic conductivity(K_(s)),saturated water content(θ_(s)),initial water content(θ_(i)),and retention water content(θ_(r)),and explore the changes in the wetting front depth and cumulative absorption volume during the absorption experiment.The Philip model was used to fit the soil absorption process and determine the soil water absorption rate.Then the length of the characteristic wetting front depth,shape coefficient,empirical parameter,inverse intake suction and soil water suction were derived from the van Genuchten model.Finally,the hydraulic parameters mentioned above were used to fit the soil water characteristic curves,unsaturated hydraulic conductivity(K_(θ))and specific water capacity(C(h)).The results showed that the wetting front depth and cumulative absorption volume of each treatment gradually decreased with increasing gravel content.Compared with control check treatment with gravel content of 0%,soil water absorption rates in the treatments with gravel contents of 10%,20%,30%,40%,and 50%decreased by 11.47%,17.97%,25.24%,29.83%,and 42.45%,respectively.As the gravel content increased,inverse intake suction gradually increased,and shape coefficient,K_(s),θ_(s),andθ_(r)gradually decreased.For the same soil water content,soil water suction and K_(θ)gradually decreased with increasing gravel content.At the same soil water suction,C(h)decreased with increasing gravel content,and the water use efficiency worsened.Overall,the water holding capacity,hydraulic conductivity,and water use efficiency of stony soil in the eastern foothills of the Helan Mountains decreased with increasing gravel content.This study could provide data support for improving soil water use efficiency in the eastern foothills of the Helan Mountains and other similar rocky mountainous areas.

Effect of Saline Water on Soil Acidity, Alkalinity and Nutrients Leaching in Sandy Loamy Soil in Rwamagana Bella Flower Farm, Rwanda

The necessity to saline and sodic waters is sometimes used for irrigating agricultural activities under certain circumstances, but it is important to note that the use of these waters comes with specific considerations and limitations. One way to decrease undesirable effects of sodic waters on the physical and chemical properties of soils is to apply organic and chemical amendments within the soil. This study aimed to assess the effectiveness of saline water on soil acidity, alkalinity and nutrients leaching in sandy loamy soil at Bella flower farm, in Rwamagana District, Rwanda. The water used was from the Muhazi Lake which is classified as Class I (Saline water quality). Column leaching experiments using treated soils were then conducted under saturated conditions. The soil under experimental was first analyzed for its textural classification, soil properties and is classified as sandy loamy soil. The t-test was taken at 1%, 5% and 10% levels of statistical significance compared to control soil. The results indicated that the application of saline water to soils caused an increase in some soil nutrients like increase of Phosphorus (P), Potassium (K+), Magnesium (Mg2+), Sulphur (S), CN ratio and Sodium (Na+) and decreased soil texture, physical and chemical properties and remained soil nutrients. Consequently, the intensive addition of saline water leachates to soil in PVC pipes led to decreased of soil EC through leaching and a raiser Soluble Sodium Percentage (SSP). The rate of saline water application affected the increase accumulation of SAR and Na% in the top soil layers. The study indicated that saline water is an inefficient amendment for sandy soil with saline water irrigation. The study recommends further studies with similar topic with saline water irrigation, as it accentuated the alkalinity levels.

AHFO-based soil water content sensing technology considering soil-sensor thermal contact resistance

The actively heated fiber-optic(AHFO)technology has become emerged as a research focus due to its advantages of distributed,real-time measurement and good durability.These attributes have led to the gradual application of AHFO technology to the water content measurement of in situ soil.However,all existing in situ applications of AHFO technology fail to consider the effect of soilesensor contact quality on water content measurements,limiting potential for the wider application of AHFO technology.To address this issue,the authors propose a method for determining the soilesensor thermal contact resistance based on the principle of an infinite cylindrical heat source.This is then used to establish an AHFO water content measurement technology that considers the thermal contact resistance.The reliability and validity of the new measurement technology are explored through a laboratory test and a field case study,and the spatial-temporal evolution of the soil water content in the case is revealed.The results demonstrate that method for determining the soilesensor thermal contact resistance is highly effective and applicable to all types of soils.This method requires only the moisture content,dry density,and thermal response of the in situ soil to be obtained.In the field case,the measurement error of soil water content between the AHFO method,which takes into account the thermal contact resistance,and the neutron scattering method is only 0.011.The water content of in situ soil exhibits a seasonal variation,with an increase in spring and autumn and a decrease in summer and winter.Furthermore,the response of shallow soils to precipitation and evaporation is significant.These findings contribute to the enhancement of the accuracy of the AHFO technology in the measurement of the water content of in situ soils,thereby facilitating the dissemination and utilization of this technology.

Estimation and mapping of water erosion and soil loss:Application of Gavrilovic erosion potential model(EPM)using GIS and remote sensing in the Assif el mal Watershed,Western high Atlas

Water erosion is a serious problem that leads to soil degradation,loss,and the destruction of structures.Assessing the risk of erosion and determining the affected areas has become crucial in order to understand the main factors influencing its evolution and to minimize its impacts.This study focuses on evaluating the risk of erosion in the Assif el mal watershed,which is located in the High Atlas Mountains.The Erosion Potential Model(EPM)is used to estimate soil losses depending on various parameters such as lithology,hydrology,topography,and morphometry.Geographic information systems and remote sensing techniques are employed to map areas with high erosive potential and their relationship with the distribution of factors involved.Different digital elevation models are also used in this study to highlight the impact of data quality on the accuracy of the results.The findings reveal that approximately 59%of the total area in the Assif el mal basin has low to very low potential for soil losses,while 22%is moderately affected and 19.9%is at high to very high risk.It is therefore crucial to implement soil conservation measures to mitigate and prevent erosion risks.

Relationship between drought and soil erosion based on the normalized differential water index(NDWI)and revised universal soil loss equation(RUSLE)model

The Langat River Basin in Malaysia is vulnerable to soil erosion risks because of its exposure to intensive land use activities and its topography,which primarily consists of steep slopes and mountainous areas.Furthermore,climate change frequently exposes this basin to drought,which negatively affects soil and water conservation.However,recent studies have rarely shown how soil reacts to drought,such as soil erosion.Therefore,the purpose of this study is to evaluate the relationship between drought and soil erosion in the Langat River Basin.We analyzed drought indices using Landsat 8 satellite images in November 2021,and created the normalized differential water index(NDWI)via Landsat 8 data to produce a drought map.We used the revised universal soil loss equation(RUSLE)model to predict soil erosion.We verified an association between the NDWI and soil erosion data using a correlation analysis.The results revealed that the southern and northern regions of the study area experienced drought events.We predicted an average annual soil erosion of approximately 58.11 t/(hm^(2)·a).Analysis of the association between the NDWI and soil erosion revealed a strong positive correlation,with a Pearson correlation coefficient of 0.86.We assumed that the slope length and steepness factor was the primary contributor to soil erosion in the study area.As a result,these findings can help authorities plan effective measures to reduce the impacts of drought and soil erosion in the future.

Current Status and Challenges of the Water and Soil Conservation in Hotan County, Xinjiang

In order to thoroughly analyze the current status and challenges faced by the water and water conservation in Hotan County of Xinjiang,the use situation of water resources,the effectiveness and shortcomings of water and soil conservation work in the region are reviewed.Hotan County has achieved several remarkable achievements in the soil and water conservation project,daily management and maintenance,and ecological restoration projects.Some measures,such as terrace construction,slope protection engineering,and the construction of windproof and sandwood belts,have also had a positive impact on improving the quality of surface water resources while effectively curbing soil erosion.But there are also lack of operating policy detailed rules and implementation plans,and planning and design of some water and soil conservation projects lack of integrity and systematicness,application and promotion of new technologies,and soil loss management and ecological recovery effect assessment lack of comprehensive assessment indicators and methods.It has caused some water and soil conservation works to fail to be effectively implemented.In this regard,countermeasures and suggestions are put forward,such as strengthening the planning and management of water and soil conservation,promoting the technology and measures of water and soil conservation,increasing investment and funding support,and strengthening publicity education and personnel training.

Effects of Typical Soil and Stratification Thickness on Water Infiltration Characteristics in Central Ningxia

In order to compare the influence of different soil types and stratification on water infiltration capacity,two main types of soil in the desert steppe,sierozem(S)and aeolian sandy soil(A),were selected,and infiltration simulation tests were conducted on homogeneous soil and layered soil(layer thickness 5,10,and 20 cm),respectively.The results show that during the whole experiment,there was a small difference between S5A95(aeolian sandy soil 95 cm thick was covered with sierozem 5 cm thick)and S10A90(aeolian sandy soil 90 cm thick was covered with sierozem 10 cm thick)in the wetting front process,infiltration rate and cumulative infiltration,but there was a significant difference between S5A95 and S20A80(aeolian sandy soil 80 cm thick was covered with sierozem 20 cm thick).In the initial infiltration stage,there was no significant difference between A5S95(sierozem 95 cm thick was covered with aeolian sandy soil 5 cm thick)and A10S90(sierozem 90 cm thick was covered with aeolian sandy soil 10 cm thick).However,with the increase of infiltration time,the wetting front process,A5S95,A10S90 and A20S80 had significant differences in terms of wetting front process,infiltration rate and cumulative infiltration.The infiltration capacity of A was significantly higher than that of S.Combined with linear R 2 value and model parameters,the three infiltration models were comprehensively compared,and the fitting process and results of the general empirical model for the infiltration process of homogeneous soil and layered soil showed good results.Three models were used to simulate the water infiltration process of layered soil with different textures,and the order of the effect is as follows:general empirical model>Kostiakov model>Philip model.Soil type and layer thickness had a great influence on water infiltration process.When sierozem was covered with aeolian sandy soil 20 cm thick,the infiltration capacity was the best.As aeolian sandy soil was covered with sierozem 10 cm thick,the infiltration effect was the worst.Therefore,once coarse graying occurs on the surface of sierozem(the thickness of sand is more than 20 cm)or when the content of fine particles overlying aeolian sandy soil(the thickness of silt and clay soil is more than 10 cm)during ecological restoration is high,the soil hydrological characteristics will change significantly,which may lead to changes in vegetation types and even ecosystem structure.

Characteristics of In-Situ Soil Water Hysteresis Observed through Multiple-Years Monitoring

A soil water retention curve (SWRC) is an essential soil physical property for analyzing transport and retention of water in a soil layer. A SWRC is often described as a single-valued function that relates the soil water potential ψ to volumetric water content θ of the soil. However, an in-situ ψ − θ relation should show soil water hysteresis, though this fact is often neglected in analyses of field soil water regimes while long-term in-situ soil water hysteresis is not well characterized. This study aimed at probing and characterizing in-situ ψ − θ relations. The developments of large hysteresis in the in-situ ψ − θ relations were observed only a few times during the study period of 82 months. Any of the large hysteretic behaviors in the ψ − θ relations began with an unusually strong continual reduction in ψ. The completion of a hysteresis loop required a recorded maximum rainfall. Because the study field had very small chances to meet such strong rainfall events, it took multiple years to restore the fraction of soil water depleted by the unusually strong continual reduction in ψ. While wetting-drying cycles had occurred within a certain domain of ψ, hysteretic behaviors tended to be so small that the in-situ ψ − θ relation can be approximated as a single-valued function of θ(ψ). These observed patterns of the in-situ ψ − θ relations were characterized by kinds of difference in dθ/dψ between a drying process and a wetting process at a given ψ. Thus, more amounts of experimental facts about wetting SWRCs in parallel with drying SWRCs should be needed for correct modelling, analyzing, and predicting soil water regimes in fields. It is also necessary to increase our understandings about the long-term trends of occurrences of extreme weather conditions associated with possible change in climate.

Response of plant physiological parameters to soil water availability during prolonged drought is affected by soil texture

Soil water deficit is increasingly threatening the sustainable vegetation restoration and ecological construction on the Loess Plateau of China due to the climate warming and human activities.To determine the response thresholds of Amygdalus pedunculata(AP)and Salix psammophila(SP)to soil water availability under different textural soils,we measured the changes in net photosynthetic rate(Pn),stomatal conductance(Gs),intercellular CO2 concentration(Ci),leaf water potential(ψw),water use efficiency(WUE)and daily transpiration rate(Td)of the two plant species during soil water content(SWC)decreased from 100%field capacity(FC)to 20%FC in the sandy and loamy soils on the Loess Plateau in the growing season from June to August in 2018.Results showed that Pn,Gs,WUE and Td of AP and SP remained relatively constant at the beginning of soil water deficit but decreased rapidly as plant available soil water content(PASWC)fell below the threshold values in both the sandy and loamy soils.The PASWC thresholds corresponding to Pn,Gs and Ci of AP in the loamy soil(0.61,0.62 and 0.70,respectively)were lower than those in the sandy soil(0.70,0.63 and 0.75,respectively),whereas the PASWC thresholds corresponding to Pn,Gs and Ci of SP in the loamy soil(0.63,0.68 and 0.78,respectively)were higher than those in the sandy soil(0.58,0.62 and 0.66,respectively).In addition,the PASWC thresholds in relation to Td and WUE of AP(0.60 and 0.58,respectively)and SP(0.62 and 0.60,respectively)in the loamy soil were higher than the corresponding PASWC thresholds of AP(0.58 and 0.52,respectively)and SP(0.55 and 0.56,respectively)in the sandy soil.Furthermore,the PASWC thresholds for the instantaneous gas exchange parameters(e.g.,Pn and Gs)at the transient scale were higher than the thresholds for the parameters(e.g.,Td)at the daily scale.Our study demonstrates that different plant species and/or different physiological parameters exhibit different thresholds of PASWC and that the thresholds are affected by soil texture.The result can provide guidance for the rational allocation and sustainable management of reforestation species under different soil conditions in the loess regions.

Spatial Availability of Nitrogen and Pesticides in the Surface Layers of Agricultural Soils of Tropical Hydrosystems in the Wet Season: Case of the BéréWatershed in Côte d’Ivoire (West Africa)

The objective of this study was to assess the contribution of the spatial organization of cropping systems and the physicochemical properties of surface layers of the agricultural zones soils in tropical hydrosystems to the spatial availability of nitrogen and pesticides during the wet season, such as the Béré watershed (BW) in C?te d’Ivoire. For this purpose, after mapping the spatial distribution of the BW cropping systems based on the likelihood classification methodology of satellite images of the study area, 27 samples from the 0 - 20 cm horizon of the soil surface layers of the agricultural areas were taken during the wet and agricultural season of the year 2016. The Kjeldahl method has been used to evaluate the total nitrogen concentration and high-performance liquid chromatography (HPLC) chain made it possible for the analysis of pesticide residues in the soil solutions. Geostatistical analysis and processing of spatial data and physicochemical and agrochemical soil parameters revealed that two major agricultural areas stand out in the BW, namely the Béré upstream watershed (BUW) dominated at 32.65% by annual croppings (maize, cotton, rainfed or lowland rice, market gardening, etc.) and the Béré downstream watershed (BDW) by large areas of perennial croppings (cashew nuts, cocoa, etc.), i.e. 21.47%. Agricultural soils in BW are usually of the moderately desaturated ferralitic type with a low acid pH and a quite strong temperature, such as those of tropical soils’ characteristics. However, agricultural soils in the BUW are characterized by higher proportions of sand and coarse sand. The parameters such as total porosity, cation exchange capacity, clay, organic matter, silt, fine silt, coarse silt, and potassium ions, are higher in the soils of the agricultural area of the BDW. Moreover, soils in the agricultural areas of the BUW are less rich in total nitrogen (0.84 g·kg-1) in contrast to those of the BDW (1.2 g·kg-1). On the other hand, the median concentrations of total pesticides remain very high in the BUW (193.80 μg·kg-1) in front of those of the BDW (94.81 μg·kg-1). In addition, the biological family of herbicides was the most notable in BW. The chemical families of triazines (100% detection;79.37 μg·kg-1) are the most important in the agricultural area of the BUW with the very significant presence of active molecules of pesticides such as simazine (92.86% detection;13.17 μg·kg-1). However, in the BDW, urea substitute (100% detection;44.02 μg·kg-1) dominate, including the active substance chlortoluron (84.62% detection;10.12 μg·kg-1). The presence and abundance of nitrogen and pesticides in the soils of the agricultural areas of BW are strongly linked to the intensive use of these agrochemicals in cropping systems in recent decades in West African countries, even though most of the active molecules found are forbidden in several countries, especially in European countries. These are applied to tropical agricultural soils with physicochemical characteristics favorable to their retention in wet weather, as confirmed by the case of BW’s agricultural soils. Therefore, the BW’s water resources present worrying risks of contamination during rainy events that deserve to be assessed and monitored. Hence the need to take mitigating measures to this effect in order to preserve the quality of the environment.

Effects of soil temperature and soil water content on soil respiration in three forest types in Changbai Mountain

Soil incubation experiments were conducted in lab to delineate the effect of soil temperature and soil water content on soil respirations in broad-leaved/Korean pine forest (mountain dark brown forest soil), dark coniferous forest (mountain brown coniferous forest soil) and erman's birch forest (mountain soddy forest soil) in Changbai Mountain in September 2001. The soil water content was adjusted to five different levels (9%, 21%, 30%, and 43%) by adding certain amount of water into the soil cylinders, and the soil sample was incubated at 0, 5, 15, 25 and 35°C for 24 h. The results indicated that in broad-leaved/Korean pine forest the soil respiration rate was positively correlated to soil temperature from 0 to 35°C. Soil respiration rate increased with increase of soil water content within the limits of 21% to 37%, while it decreased with soil water content when water content was over the range. The result suggested the interactive effects of temperature and water content on soil respiration. There were significant differences in soil respiration among the various forest types. The soil respiration rate was highest in broad-leaved/Korean pine forest, middle in erman's birch forest and the lowest in dark coniferous forest. The optimal soil temperature and soil water content for soil respiration was 35°C and 37% in broad-leaved/Korean pine forest, 25°C and 21% in dark coniferous forest, and 35°C and 37% in erman's birch forest. Because the forests of broad-leaved/Korean pine, dark coniferous and erman's birch are distributed at different altitudes, the soil temperature had 4–5°C variation in different forest types during the same period. Thus, the soil respiration rates measured in brown pine mountain soil were lower than those in dark brown forest and those measured in mountain grass forest soil were higher than those in brown pine mountain soil. Key words Soil temperature - Soil water content - Soil respiration - The typical forest ecosystem in Changbai Mountain CLC number S7118.51 Document code A Foundation item: This study was supported by grant from the National Natural Science Foundation of China (No. 30271068), the grant of the Knowledge Innovation Program of Chinese Academy of Sciences (KZ-CX-SW-01-01B-12) and the grant from Advanced Programs of Institute of Applied Ecology Chinese Academy of Sciences.Biography: WANG Miao (1964-), male, associate professor in Institute of Applied Ecology, Chinese Academy of Science, Shenyang 110016, P. R. China.Responsible editor: Song Funan

Effect of Different Vegetation Types on Soil Erosion by Water

The C factor in Universal Soil loss Equation reflecting the effect of vegetation on soil erosion by water is one of the important parameters for estimating soil erosion rate and selecting appropriate land use patterns. In this study, the C factor for nine types of grassland and woodland was estimated from 195 plot-year observation data of six groups of soil erosion experiments on Loess Plateau. The result indicates that the effects of woodland and grassland on soil erosion keep approximately uniform after two or three years' growth. The estimated woodland C factor ranges from 0.004 to 0.164, and the grassland C factor ranges from 0.071 to 0.377, showing that the effect of woodland and grassland on soil conservation is greatly better than that of cropland. The study results can be used to compare or estimate the soil loss from land with different vegetation cover, and are the useful references for land use pattern selection and the project of returning cropland to forest or grassland.

Study on the Forest Vegetation and Its Water and Soil Conservation Value in Fuxian Lake Drainage Area in Yunnan Province

By using French SPOT5 satellite remote sensing image to contrast on the spot,the forest vegetation in Fuxian Lake basin was categorized into 23 forest types,6 vegetation subtypes,5 vegetation types,and the areas were respectively calculated.The tree species structure and the coverage degree of every kind of forest vegetation were investigated,and the characteristics of forest vegetation were analyzed.The results showed that the soil conservation amount of forest in Fuxian Lake basin was 137.50×106 t/a,and the soil conservation value was 622.30×106 yuan/a.Moreover,the water source conservation value was 506.84×106 yuan/a.

Water content and modulus relationship of a compacted unsaturated soil

In order to assess the performance of the embankment soil under various climate conditions during the period of service, the modulus behaviour of an unsaturated compacted soil is evaluated using the constant water content triaxial test. Since the water content measurement method is simple and economical and it is used widely in engineering, the soil suction is replaced by the water content and the relationship between the water content and the modulus is developed. The compacted samples are prepared with different compacted water contents, and samples with a similar water content subjected to drying or wetting procedures prior to the triaxial test are also investigated. The effect of the water content and the confining pressure on the modulus is analyzed. The results show that the modulus decreases with the increase in the water content and a power function can be proposed to quantitatively describe the relationship between the modulus and the water content in the range of the measured water content. The modulus increases with the increase in the confining pressure of the compacted soil. However, the effect of the water content on the modulus is more pronounced than that of the confining pressure. This research can be referenced for the compacted embankment soil assessment in-service period.

Substantive Characteristics of Water and Soil Conservation and Ecological Civilization Construction in China

Water and soil conservation is an important part of eco-civilization con-struction. It is a major part of eco-construction and lifeline of social and economy development. Therefore, water and soil conservation is of great significance in maintaining eco-safety. The research concluded status quo and characters of water and soil losses in China and analyzed water and soil conservation and construction of eco-civilization from the perspectives of water and soil conservation and con-struction of eco-civilization.

Effect of Mulberry(Morus alba Linn) on Soil and Water Conservation

Rational development and utilization of hilly land is an effective measure for raising land productivity, developing countryside economy, increasing peasants＇ income, conserving soil and water, and improving eco-environment. The growth and root distribution of mulberry trees were studied. Various indexes including soil physical characters and hydrological status, water infiltration rate, water and soil loss and soil erosion amount were tested. The results indicated that mulberry trees had the effects of intercepting rainfall, improving soil infiltration rate, decreasing soil erosion amount, and conserving water and soil