Persistence of fertilization effects on soil organic carbon in degraded alpine wetlands in the Yellow River source region

In the restoration of degraded wetlands,fertilization can improve the vegetation-soil-microorganisms complex,thereby affecting the organic carbon content.However,it is currently unclear whether these effects are sustainable.This study employed Biolog-Eco surveys to investigate the changes in vegetation characteristics,soil physicochemical properties,and soil microbial functional diversity in degraded alpine wetlands of the source region of the Yellow River at 3 and 15 months after the application of nitrogen,phosphorus,and organic mixed fertilizer.The following results were obtained:The addition of nitrogen fertilizer and organic compost significantly affects the soil organic carbon content in degraded wetlands.Three months after fertilization,nitrogen addition increases soil organic carbon in both lightly and severely degraded wetlands,whereas after 15 months,organic compost enhanced the soil organic carbon level in severely degraded wetlands.Structural equation modeling indicates that fertilization decreases the soil pH and directly or indirectly influences the soil organic carbon levels through variations in the soil water content and the aboveground biomass of vegetation.Three months after fertilization,nitrogen fertilizer showed a direct positive effect on soil organic carbon.However,organic mixed fertilizer indirectly reduced soil organic carbon by increasing biomass and decreasing soil moisture.After 15 months,none of the fertilizers significantly affected the soil organic carbon level.In summary,it can be inferred that the addition of nitrogen fertilizer lacks sustainability in positively influencing the organic carbon content.

Dataset of Comparative Observations for Land Surface Processes over the Semi-Arid Alpine Grassland against Alpine Lakes in the Source Region of the Yellow River

Thousands of lakes on the Tibetan Plateau(TP) play a critical role in the regional water cycle, weather, and climate. In recent years, the areas of TP lakes underwent drastic changes and have become a research hotspot. However, the characteristics of the lake-atmosphere interaction over the high-altitude lakes are still unclear, which inhibits model development and the accurate simulation of lake climate effects. The source region of the Yellow River(SRYR) has the largest outflow lake and freshwater lake on the TP and is one of the most densely distributed lakes on the TP. Since 2011,three observation sites have been set up in the Ngoring Lake basin in the SRYR to monitor the lake-atmosphere interaction and the differences among water-heat exchanges over the land and lake surfaces. This study presents an eight-year(2012–19), half-hourly, observation-based dataset related to lake–atmosphere interactions composed of three sites. The three sites represent the lake surface, the lakeside, and the land. The observations contain the basic meteorological elements,surface radiation, eddy covariance system, soil temperature, and moisture(for land). Information related to the sites and instruments, the continuity and completeness of data, and the differences among the observational results at different sites are described in this study. These data have been used in the previous study to reveal a few energy and water exchange characteristics of TP lakes and to validate and improve the lake and land surface model. The dataset is available at National Cryosphere Desert Data Center and Science Data Bank.

Characteristics of grassland degradation and driving forces in the source region of the Yellow River from 1985 to 2000

The source region of the Yellow River is located in the middle east of the Tibetan Plateau in northwest China. The total area is about 51,700 km^2, mainly covered by grassland （79%）, unused land （16%） and water （4%）. The increasing land utilization in this area has increased the risk of environmental degradation. The land use/cover data （1985 and 2000） provided by the Data Center of Resources and Environment in the Chinese Academy of Sciences were used to analyze the land cover change in the source region of the Yellow River. DEM （1：250,000） data, roads and settlement data were used to analyze the spatial characteristics of grasslands degradation. The ArcGIS 9 software was used to convert data types and do the overlay, reclassification and zonal statistic analysis. Results show that grassland degradation is the most important land cover change in the study area, which occupied 8.24% of the region＇s total area. Human activities are the main causes of the grassland degradation in the source region of the Yellow River： 1） the degradation rate is higher on the sunny slope than on the shady slope; 2） the grassland degradation rate decreases with an increase in the elevation, and it has a correlation coefficient of -0.93; 3） the nearer to the settlements the grassland is, the higher the degradation rate. Especially within a distance range of 12 km to the settlements, the grassland degradation rate is highly related with the distance, with a coefficient of -0.99; and 4） in the range of 4 km, the degradation rate decreases with the increase of distance to the roads, with a correlation coefficient of -0.98. Besides some physical factors, human activities have been the most important driving forces of the grassland degradation in the source region of the Yellow River since 1985. To resolve the degradation problems, population control is essential, and therefore, it can reduce the social demand of livestock products from the grassland. To achieve sustainable development, it needs to improve the management of grassland ecosystem.

Changes in freezing and thawing indices over the source region of the Yellow River from 1980 to 2014

Freezing and thawing indices are not only of great significance for permafrost research but also are important indicators of the effects of climate change.However,to date,research on ground-surface freezing and thawing indices and their relationship with air indices is limited.Based on daily air and ground-surface temperatures collected from 11 meteorological stations in the source region of the Yellow River,the freezing and thawing indices were calculated,and their spatial distribution and trends were analyzed.The air-freezing index(AFI),air-thawing index(ATI),ground surface-freezing index(GFI),ground surface-thawing index(GTI),air thawing-freezing index ratio(Na)and surface ground thawing-freezing index ratio(Ng)were 1554.64,1153.93,1.55,2484.85,850.57℃-days and 3.44,respectively.Altitude affected the spatial distribution of the freezing and thawing indices.As the altitude increased,the freezing indices gradually increased,and the thawing indices and thawing-freezing index ratio decreased.From 1980 to 2014,the AFI and GFI decreased at rates of 8.61 and 11.06℃-days a^(-1),the ATI and GTI increased at 9.65 and 14.53℃-days a^(-1),and Na and Ng significantly increased at 0.21 and 0.79 decade^(-1).Changes in the freezing and thawing indices were associated with increases in the air and ground-surface temperatures.The rates of change of the ground surface freezing and thawing indices were faster than the air ones because the rate of increase of the groundsurface temperature was faster than that of the air and the difference between the ground surface and air increased.The change point of the time series of freezing and thawing indices occurred in 2000–2001.After 2000–2001,the AFI and GFI were lower than before the change point,and the changing trend was lower.The ATI,GTI,Na and Ng during 2001–2014 were higher,with faster rates than before.In addition,the annual thawing indices composed a greater proportion of the mean annual air temperature and mean annual ground surface temperature than the annual freezing indices.This study provides the necessary basis for research on and prediction of permafrost changes,especially changes in the depth of the active permafrost layer,climate change,and possible evolution of the ecological environment over the source region of the Yellow River on the Qinghai-Tibet Plateau.

Influencing factors of water resources in the source region of the Yellow River

Taking the source region of the Yellow River as a study area and based on the data from Madoi Meteorological Station and Huangheyan Hydrological Station covering the period 1955-2005, this paper analyses the changing trends of surface water resources, climate and frozen ground and reveals their causes. Results show that there exist frequent fluctuations from high to low water flow in the 51-year period. In general, the discharge has shown a de- clining trend in the 51 years especially since the 1990s. The annual distribution shows one peak which, year on year is getting smaller. （1） Precipitation has a significant and sustained influence on discharge. （2） A sharp rise of temperature resulted in the increase of evaporation and the decrease of discharge, which has a greater effect than on ice-snow melting. （3） Frozen ground tends to be degraded markedly. There is a significant positive correlation be- tween the permafrost thickness and the discharge. （4） Evaporation rates are significantly increasing, leading to the decrease of discharge. 70% of the discharge reduction resulted from climate change, and the remaining 30% may have been caused by human activities.

Estimation of water balance in the source region of the Yellow River based on GRACE satellite data

Water storage has important significance for understanding water cycles of global and local domains and for monitoring climate and environmental changes. As a key variable in hydrology, water storage change represents the sum of precipitation, evaporation, surface runoff, soil water and groundwater exchanges. Water storage change data during the period of 2003-2008 for the source region of the Yellow River were collected from Gravity Recovery and Climate Experiment （GRACE） satellite data. The monthly actual evaporation was estimated according to the water balance equation. The simulated actual evaporation was significantly consistent and correlative with not only the observed pan （20 cm） data, but also the simulated results of the version 2 of Simple Biosphere model. The average annual evaporation of the Tangnaihai Basin was 506.4 mm, where evaporation in spring, summer, autumn and winter was 130.9 mm, 275.2 mm, 74.3 mm and 26.1 mm, and accounted for 25.8%, 54.3%, 14.7% and 5.2% of the average annual evaporation, respectively, The precipitation increased slightly and the actual evaporation showed an obvious decrease. The water storage change of the source region of the Yellow River displayed an increase of 0.51 mm per month from 2003 to 2008, which indicated that the storage capacity has significantly increased, probably caused by the degradation of permafrost and the increase of the thickness of active layers. The decline of actual evaporation and the increase of water storage capacity resulted in the increase of river runoff.

Eco-environment range in the source regions of the Yangtze and Yellow rivers

Based on geographical and hydrological extents delimited, four principles are identified, as the bases for delineating the ranges of the source regions of the Yangtze and Yellow rivers in the paper. According to the comprehensive analysis of topographical characteristics, climate conditions, vegetation distribution and hydrological features, the source region ranges for eco-environmental study are defined. The eastern boundary point is Dari hydrological station in the upper reach of the Yellow River. The watershed above Dari hydrological station is the source region of the Yellow River which drains an area of 4.49×10 4 km 2 . Natural environment is characterized by the major topographical types of plateau lakes and marshland, gentle landforms, alpine cold semi-arid climate, and steppe and meadow vegetation in the source region of the Yellow River. The eastern boundary point is the convergent site of the Nieqiaqu and the Tongtian River in the upstream of the Yangtze River. The watershed above the convergent site is the source region of the Yangtze River, with a watershed area of 12.24×10 4 km 2 . Hills and alpine plain topography, gentle terrain, alpine cold arid and semi-arid climate, and alpine cold grassland and meadow are natural conditions in the source region of the Yangtze River.

Impact of land-cover and climate changes on runoff of the source regions of the Yellow River

After dividing the source regions of the Yellow River into 38 sub-basins, thepaper made use of the SWAT model to simulate streamflow with validation and calibration of theobserved yearly and monthly runoff data from the Tangnag hydrological station, and simulationresults are satisfactory. Five land-cover scenario models and 24 sets of temperature andprecipitation combinations were established to simulate annual runoff and runoff depth underdifferent scenarios. The simulation shows that with the increasing of vegetation coverage annualrunoff increases and evapotranspiration decreases in the basin. When temperature decreases by 2℃and precipitation increases by 20%, catchment runoff will increase by 39.69%, which is the largestsituation among all scenarios.

The Impacts of Permafrost Change on NPP and Implications:A Case of the Source Regions of Yangtze and Yellow Rivers

This paper studies the relationship between net primary productivity (NPP) and annual average air temperature (GT) at 0cm above ground in permafrost regions by using revised Chikugo NPP model,cubic spline interpolating functions,and non-linear regression methods.The source regions of the Yangtze and Yellow Rivers were selected as the research areas.Results illustrate that:(1) There is significant non-linear relationship between NPP and GT in various typical years;(2) The maximum value of NPP is 6.17,5.87,7.73,and 5.41 DM·t·hm-2 ·a-1 respectively,and the corresponding GT is 7.1,10.0,21.2,and 8.9 o C respectively in 1980,1990,2000 and 2007;(3) In 1980,the sensitivity of NPP to GT is higher than in 1990,2000 and 2007.This tendency shows that the NPP presents change from fluctuation to an adaptation process over time;(4) During 1980～2007,the accumulated NPP was reduced to 8.05,and the corresponding carrying capacity of theoretical livestock reduced by 11%;(5) The shape of the demonstration region of ecological compensation system,livelihood support system,and science appraisal system in the source regions of Yangtze and Yellow Rivers are an important research for increasing the adaptation capacity and balancing protection and development.

Adaptation Management of Mountain Tourism Service: The Case of the Source Regions of the Yangtze and Yellow River

Mountain areas are often rich in ecological diversity and recreational opportunities. Mountain tourism is thought to be an effective and important means for maintaining and expanding rural economies and, thus, improving the living conditions of rural societies. As mountain tourism service research is a professional field with several disciplines involved, a multi-disciplinary management pIatform is needed and it facilitates participation in sustainable mountain development by diverse stakeholders. With the source regions of the Yangtze and the Yellow River as a case study, this paper presents a conceptual framework for an adaptation management of mountain tourism services according to technical, policy, social and economic dimensions. The framework is based on a vulnerability assessment of mountain ecosystems, and can serve as a reference for the development of tourism service in other mountain areas.

Role of permafrost in resilience of social-ecological system and its spatio-temporal dynamics in the source regions of Yangtze and Yellow Rivers

Permafrost is one of the key components of terrestrial ecosystem in cold regions. In the context of climate change, few studies have investigated resilience of social ecological system(SER) from the perspective of permafrost that restricts the hydrothermal condition of alpine grassland ecosystem. In this paper, based on the structural dynamics, we developed the numerical model for the SER in the permafrost regions of the source of Yangtze and Yellow Rivers, analyzed the spatial-temporal characteristics and sensitivity of the SER, and estimated the effect of permafrost change on the SER. The results indicate that: 1) the SER has an increasing trend, especially after 1997, which is the joint effect of precipitation, temperature, NPP and ecological conservation projects; 2) the SER shows the spatial feature of high in southeast and low in northwest,which is consistent with the variation trends of high southeast and low northwest for the precipitation, temperature and NPP, and low southeast and high northwest for the altitude; 3) the high sensitive regions of SER to the permafrost change have gradually transited from the island distribution to zonal and planar distribution since 1980, moreover, the sensitive degree has gradually reduced; relatively, the sensitivity has high value in the north and south, and low value in the south and east; 4) the thickness of permafrost active layer shows a highly negative correlation with the SER. The contribution rate of permafrost change to the SER is-4.3%, that is, once the thickness of permafrost active layer increases 1 unit, the SER would decrease 0.04 units.

Different Responses of Vegetation to Frozen Ground Degradation in the Source Region of the Yellow River from 1980 to 2018

Frozen ground degradation under a warming climate profoundly influences the growth of alpine vegetation in the source region of the Qinghai-Tibet Plateau.This study investigated spatiotemporal variations in the frozen ground distribution,the active layer thickness(ALT)of permafrost(PF)soil and the soil freeze depth(SFD)in seasonally frozen soil from 1980 to 2018 using the temperature at the top of permafrost(TTOP)model and Stefan equation.We compared the effects of these variations on vegetation growth among different frozen ground types and vegetation types in the source region of the Yellow River(SRYR).The results showed that approximately half of the PF area(20.37%of the SRYR)was projected to degrade into seasonally frozen ground(SFG)during the past four decades;furthermore,the areal average ALT increased by 3.47 cm/yr,and the areal average SFD decreased by 0.93 cm/yr from 1980 to 2018.Accordingly,the growing season Normalized Difference Vegetation Index(NDVI)presented an increasing trend of 0.002/10 yr,and the increase rate and proportion of areas with NDVI increase were largest in the transition zone where PF degraded to SFG(the PF to SFG zone).A correlation analysis indicated that variations in ALT and SFD in the SRYR were significantly correlated with increases of NDVI in the growing season.However,a rapid decrease in SFD(<-1.4 cm/10 yr)could have reduced the soil moisture and,thus,decreased the NDVI.The NDVI for most vegetation types exhibited a significant positive correlation with ALT and a negative correlation with SFD.However,the steppe NDVI exhibited a significant negative correlation with the SFD in the PF to SFG zone but a positive correlation in the SFG zone,which was mainly limited by water condition because of different change rates of the SFD.

The heterogeneity of hydrometeorological changes during the period of 1961-2016 in the source region of the Yellow River, China

Runoff in the source region of a river makes up most of water resources in the whole basin in arid and semi-arid areas. It is very important for water resources management to timely master the latest dynamic changes of the runoff and quantitatively reveal its main driving factors. This paper aims to discover the variation heterogeneity of runoff and the impacts of climatic factors on this runoff in the source region of the Yellow River(SRYR) in China from 1961 to 2016. We divided SRYR into four sub-regions, and analyzed changes of their contributions to total runoff in SRYR. We also revealed the impacts of precipitation, temperature and potential evapotranspiration on runoff in each sub-region by constructing the regression relationships between them at multiple temporal scales. The changes of runoff in the four sub-regions and their contributions to the total runoff were not exactly consistent. The climatic variables’ changes also have heterogeneity, and runoff was mainly affected by precipitation compared to influences of temperature or potential evapotranspiration. Their impacts on runoff have spatiotemporal heterogeneity and can be reflected by very significant-linear regression equations.It provided a simple method to predict headwater runoff for better water management in the whole basin.

Changes in stress within grassland ecosystems in the three counties of the source regions of the Yangtze and Yellow Rivers

Based on a database of more than 40 years of second production process and energy flow records for Maduo,Qumalai and Yushu counties,a dynamic model of the stress within grassland ecosys-tems was established using a nonlinear regression method for this source regions of the Yangtze and Yel-low Rivers.The results show that dynamic curves of stress within grassland ecosystems in the three coun-ties were in the shape of an inverted 'U' during the period 1965-2007.It also revealed that the variation in actual amount of livestock inventories reflected the general trends of the stress within the grassland eco-systems in the source regions,although there were many other factors for the increase or reduction in grassland ecosystem stress.

The Effects of Natural Capital Protection on Pastoralist's Livelihood and Management Implication in the Source Region of the Yellow River, China

The interaction among different livelihood capitals is a key to generate a deeper understanding of the livelihood sustainability.In this paper,we use net income per capita(economic capital),meat and milk production per capita(physical capital),and areas of fenced pasture,livestock shelter,grassland rodent control and planted grassland(physical capital) as proxy indicators of livelihood promotion,livelihood provision,and livelihood protection respectively.By developing a correlation model between pastoralists' livelihood protection and improvement,we found that(1) there is a statistically significant correlation between the pastoralists' livelihood protection and promotion;(2) based on the maximum effect of pastoralists' livelihood promotion and provision,there is a benchmark in the effect of the intervention intensity of livelihood capital(grassland resource protection) on livelihood improvement;(3) on basis of two indicators,i.e.net income per capita and meat production per capita,the reasonable scales of fenced pasture,livestock shelter and planted grassland are less than 843,860 and 46 thousand hectares(hm2) per year respectively.With the marginal effect of livelihood protection,moderately decreased areas of fenced pasture and planted grassland,and increased area of livestock shelter is a critical to ensure pastoralist's livelihood sustainability.

Evolution of the freeze-thaw cycles in the source region of the Yellow River under the influence of climate change and its hydrological effects

As an important water source and ecological barrier in the Yellow River Basin,the source region of the Yellow River(above the Huangheyan Hydrologic Station)presents a remarkable permafrost degradation trend due to climate change.Therefore,scientific understanding the effects of permafrost degradation on runoff variations is of great significance for the water resource and ecological protection in the Yellow River Basin.In this paper,we studied the mechanism and extent of the effect of degrading permafrost on surface flow in the source region of the Yellow River based on the monitoring data of temperature and moisture content of permafrost in 2013–2019 and the runoff data in 1960–2019.The following results have been found.From 2013 to 2019,the geotemperature of the monitoring sections at depths of 0–2.4 m increased by 0.16°C/a on average.With an increase in the thawing depth of the permafrost,the underground water storage space also increased,and the depth of water level above the frozen layer at the monitoring points decreased from above 1.2 m to 1.2–2 m.64.7%of the average multiyear groundwater was recharged by runoff,in which meltwater from the permafrost accounted for 10.3%.Compared to 1960-1965,the runoff depth in the surface thawing period(from May to October)and the freezing period(from November to April)decreased by 1.5 mm and 1.2 mm,respectively during 1992–1997,accounting for 4.2%and 3.4%of the average annual runoff depth,respectively.Most specifically,the decrease in the runoff depth was primarily reflected in the decreased runoff from August to December.The permafrost degradation affects the runoff within a year by changing the runoff generation,concentration characteristics and the melt water quantity from permafrost,decreasing the runoff at the later stage of the permafrost thawing.However,the permafrost degradation has limited impacts on annual runoff and does not dominate the runoff changes in the source region of the Yellow River in the longterm.

Climate transformation to warm-humid and its effect on river runoff in the source region of the Yellow River

The change characteristics and trends of the regional climate in the source region of the Yellow River, and the response of runoff to climate change, are analyzed based on observational data of air temperature, precipitation, and runoff at 10 main hydrological and weather stations in the region. Our results show that a strong signal of climate shift from warm-dry to warm-humid in the western parts of northwestern China （Xinjiang） and the western Hexi Corridor of Gansu Province occurred in the late 1980s, and a same signal of climate change occurred in the mid-2000s in the source region of the Yellow River located in the eastern part of northwestern China. This climate changeover has led to a rapid increase in rainfall and stream runoff in the latter region. In most of the years since 2004 the average annual precipitation in the source region of the Yellow River has been greater than the long-term average annual value, and after 2007 the runoff measured at all of the hydrologic sections on the main channel of the Yellow River in the source region has also consistently exceeded the long-term average annual because of rainfall increase. It is difficult to determine the prospects of future climate change until additional observations and research are conducted on the rate and temporal and spatial extents of climate change in the region. Nevertheless, we predict that the climate shift from warm-dry to warm-humid in the source region of the Yellow River is very likely to be in the decadal time scale, which means a warming and rainy climate in the source region of the Yellow River will continue in the coming decades.

Spatial-temporal variations in near-surface soil freeze-thaw cycles in the source region of the Yellow River during the period 2002–2011 based on the Advanced Microwave Scanning Radiometer for the Earth Observing System(AMSR-E) data

Detecting near-surface soil freeze-thaw cycles in high-altitude cold regions is important for understanding the Earth＇s surface system, but such studies are rare. In this study, we detected the spatial-temporal variations in near-surface soil freeze-thaw cycles in the source region of the Yellow River（SRYR） during the period 2002–2011 based on data from the Advanced Microwave Scanning Radiometer for the Earth Observing System（AMSR-E）. Moreover, the trends of onset dates and durations of the soil freeze-thaw cycles under different stages were also analyzed. Results showed that the thresholds of daytime and nighttime brightness temperatures of the freeze-thaw algorithm for the SRYR were 257.59 and 261.28 K, respectively. At the spatial scale, the daily frozen surface（DFS） area and the daily surface freeze-thaw cycle surface（DFTS） area decreased by 0.08% and 0.25%, respectively, and the daily thawed surface（DTS） area increased by 0.36%. At the temporal scale, the dates of the onset of thawing and complete thawing advanced by 3.10（±1.4） and 2.46（±1.4） days, respectively; and the dates of the onset of freezing and complete freezing were delayed by 0.9（±1.4） and 1.6（±1.1） days, respectively. The duration of thawing increased by 0.72（±0.21） day/a and the duration of freezing decreased by 0.52（±0.26） day/a. In conclusion, increases in the annual minimum temperature and winter air temperature are the main factors for the advanced thawing and delayed freezing and for the increase in the duration of thawing and the decrease in the duration of freezing in the SRYR.

Biological Characteristics of Carex brunnescens for Sand Fixation in the Source Region of the Yellow River

Carex brunnescens, a pioneer plant that has an excellent ability to fix sand in the source region of the Yellow River （Maqu）, plays an important role in maintaining the ecosystem stability of alpine grassland in Maqu. In this study, the biological characteristics （phonological characters, the growth process of overground and underground organs, and the morphological characters of underground organs） of C. brunnescens were studied by a field observation experiment. The results showed that C. brunnescens had the characteristics of turning green earlier than other plants, a long growth period, and two flowering and fruiting cycles. The leaf width, length and number of a single plant, and the density, coverage and leaf density of community increased significantly from the leaf extension period to the fruit mature period and then tended to be stable in the withering period, while the plant height and leaf area of a single plant and the leaf area of community rose significantly at first and then decreased. Underground stems （horizontal and vertical stems） and roots of C. brunnescens could survive in sand at a depth of 0-60 cm. The number of middle roots （0.2-0.5 mm in diameter） was the largest in all soil layers （0-20, 20-40 and 40-60 cm）, and the total length of fine roots （〈0.2 mm） were the maximum in the sand at a depth of 20-40 cm, while the total length of middle roots was the maximum in the sand layer at a depth of 0-20 cm. The length, fresh weight and dry weight of the main root, horizontal and vertical stems was the maximum in the sand layer at a depth of 10-30 cm and was the minimum in the sand layer at a depth of 40-50 cm. It is concluded that C. brunnescens can well adapt to the alpine sand habitat of Maqu, can be used as the constructive species for ecological restoration in the alpine desertified grassland of Maqu, and has good popularization and application prospects.

Soil hydraulic conductivity and its influence on soil moisture simulations in the source region of the Yellow River——take Maqu as an example

Saturated hydraulic conductivity and unsaturated hydraulic conductivity which are influenced by soil are two important factors that affect soil water transport.In this paper,data supplied by the Chinese Academy of Sciences are used to determine true unsaturated hydrology values.Furthermore,in combination with observed,model simulation and experimental data,an improved saturated hydraulic conductivity parameterization scheme is carried out in CLM4.5 at a single point in the summer.The main results show that:(1)After improving saturated hydraulic conductivity in CLM4.5 through a parameterization modification,it is found that shallow layer soil moisture increases compared to the initial value;and(2)The numerical values of unsaturated hydraulic conductivities in the model are obviously larger than experimental values.By substituting the BrooksCorey soil water characteristic curve into the Mualem model,the value of unsaturated hydraulic conductivity is modified;(3)By using the modified value,it is found that the attenuating magnitude of simulated soil moisture caused by each rainfall event is reduced.The soil moisture variation in shallow layers(5,10 and 20 cm)could be better displayed.