Mechanism of formation of sliding ground fissure in loess hilly areas caused by underground mining

Based on a shallow-buried coal seam covered with thick loose layers in hilly loess areas of western China,we developed a mechanical model for a mining slope with slope stability analysis, and studied the mechanism of formation and development of a sliding ground fissure by the circular sliding slice method.Moreover, we established a prediction model of a sliding fissure based on a mechanical mechanism,and verified its reliability on face 52,304, an engineering example, situated at Daliuta coal mine of Shendong mining area in western China. The results show that the stress state of a mining slope is changed by its gravity and additional stress from the shallow-buried coal seam and gully terrain. The mining slope is found to be most unstable when the ratio of the down-sliding to anti-sliding force is the maximum, causing local fractures and sliding fissures. The predicted angles for the sliding fissure of face 52,304 on both sides of the slope are found to be 64.2° and 82.4°, which are in agreement with the experimental data.

Dynamic Analysis of Supply and Demand Coupling of Ecosystem Services in Loess Hilly Region:A Case Study of Lanzhou,China

The relationship between the supply and demand for ecosystem services(ESs)is a key issue for the rational allocation of natural resources and optimisation of sustainable development capacity.This paper investigateed the dynamic evolution features of supply and demand of four ESs in Lanzhou of China,namely,water supply,food supply,carbon fixation and soil retention services.The crosssectional data of 2005 and 2017 were used for calculating ESs value and its supply and demand through ArcGIS software,InVEST model,elastic coefficient model and coupling coordination model.Results showed that:1)from 2005 to 2017,the supply of water supply services increased,the demand of soil retention services decreased,and the supply and demand of food supply and carbon fixation services increased.The high-value areas of service supply were mainly distributed in the rocky mountain areas in the southeast and northwest with high vegetation coverage,while the high-value areas of demand were mainly distributed in the urban areas and surrounding areas with high population density.2)There were five different types of coupling relations.Water supply service was dominated by a negative coupling type D,which means that the decrease in demand for ESs has had a positive response on the supply of ESs.Negative coupling type C was the main type of food supply and carbon fixation services,which means that the increase in demand for ESs has had a negative response on the supply of ESs.All three services were supplemented by a positive coupling type A,which means that the increase in demand for ESs has had a positive response on the supply of ESs.Soil retention service generally exhibits a positive coupling type B,which means that the decrease in demand for ESs has had a negative response on the supply of ESs.3)Over the past 12 yr,the coordination degree of supply and demand of water supply,food supply and soil retention services decreased,and the coordination degree of carbon fixation service increased.Various types of ES had a low degree of coupling and coordination,showing different characteristics of temporal and spatial evolution.The areas with imbalanced ESs supply and demand were mainly distributed in urban areas dominated by construction land.The research results are valuable to the optimisation of urban and rural ecological environments and the sustainable development of territory space under the framework of ecological civilisation,including similar ecologically vulnerable areas in other developing countries.

Spatial variability of leaf wetness under different soil water conditions in rainfed jujube (Ziziphus jujuba Mill.) in the loess hilly region, China

Leaf wetness provides a wide range of benefits not only to leaves,but also to ecosystems and communities.It regulates canopy eco-hydrological processes and drives spatial differences in hydrological flux.In spite of these functions,little remains known about the spatial distribution of leaf wetness under different soil water conditions.Leaf wetness measurements at the top(180 cm),middle(135 cm),and bottom(85 cm)of the canopy positions of rainfed jujube(Ziziphus jujuba Mill.)in the Chinese loess hilly region were obtained along with meteorological and soil water conditions during the growing seasons in 2019 and 2020.Under soil water non-deficit condition,the frequency of occurrence of leaf wetness was 5.45%higher at the top than at the middle and bottom of the canopy positions.The frequency of occurrence of leaf wetness at the top,middle and bottom of the canopy positions was over 80%at 17:00‒18:00(LST).However,the occurrence of leaf wetness at the top was earlier than those at the middle and bottom of the canopy positions.Correspondingly,leaf drying at the top was also latter than those at the middle and bottom of the canopy positions.Leaf wetness duration at the middle was similar to that at the bottom of the canopy position,but about 1.46-3.01 h less than that at the top.Under soil water deficit condition,the frequency of occurrence of leaf wetness(4.92%-45.45%)followed the order of top>middle>bottom of the canopy position.As the onset of leaf wetness was delayed,the onset of wet leaf drying was advanced and the leaf wetness duration was shortened.Leaf wetness duration at the top was linearly related(R^(2)>0.70)to those at the middle and bottom of the canopy positions under different soil water conditions.In conclusion,the hydrological processes at canopy surfaces of rainfed jujube depended on the position of leaves,thus adjusting canopy structure to redistribute hydrological process is a way to meet the water need of jujube.

Effects of Plant Community Type on Soil Methane Flux in Semiarid Loess Hilly Region,Central Gansu Province,China

Methane(CH_(4))is an important greenhouse gas second only to CO_(2)in terms of its greenhouse effect.Vegetation plays an important role in controlling soil CH_(4)fluxes,but the spatial variability of soil CH_(4)fluxes during vegetation restoration in Loess Hilly Region(LHR)is not fully understood.The effects of different plant community types[Medicago sativa grassland(MS);Xanthoceras sorbifolium forestland(XS);Caragana korshinskii bushland(CK);Hippophae rhamnoides shrubland(HR);and Stipa bungeana grassland(SB)]on soil CH_(4)flux in LHR were studied via the static chamber technique.The results showed that the five plant community types were sinks of soil CH_(4)in LHR,the plant community type significantly affected the soil CH_(4)flux,and the average CH_(4)uptake from high to low was in SB,HR,CK,MS,and XS.During the whole study period,the soil CH_(4)flux showed similar interannual variation.The maximum absorption of soil CH_(4)appeared in the growing season,while the minimum appeared in winter.Soil CH_(4)uptake was positively correlated with soil temperature and soil moisture.Soil temperature and moisture are important controlling factors for the temporal variability of soil CH_(4)flux.In LHR,the Stipa bungeana grassland is the more suitable plant community type for reducing soil CH_(4)emissions.In the process of vegetation restoration in LHR,the soil CH_(4)absorption potential of different plant community types should be considered,ecological benefits should be taken into account,and vegetation more suitable for mitigating the greenhouse effect should be selected.

Impacts of Sloping Land Conversion Program on the vegetation in loess hilly and gully area of northern Shaanxi

Aiming at alleviating the serious soil erosion, the Chinese government initiated the Sloping Land Conversion Program （SLCP） in 1999. Now; after 8 years of project implementation, the ecological recovery effects of the SLCP have become the hot issue of academic circle. This paper; raking the loess hill and gully area of northern Shaanxi as an example, presents a methodology for assessing the vegetation restoration effect of SLCP with normalized difference vegetation index （NDVI）. The key components include calculation of the Growing Season NDVI （GSNDVI）, and estimation of the NVDI change induced by climate and SLCP, respectively. Based on the method, the NDVI change between 2000 and 2006 was obtained using the GSNDVI that excluded the noise from snow and ice. After the part of total NDVI change caused to： climate variation was estimated using empiric formulae, we obtained the part induced by human factors, i.e. the SLCP The human induced part of ND VI change was considered as an approximation indicating the effect of the SLCP on the vegetation. Finally, we analyzed the ND VI change characters of the whole study area, different slope lands and different land use types by spatial statistics method. Results show that the vegetation condition is significantly improved by the SLCP, particularly land types that directly involved in the SLCP, such as steeply slope farmlands, degraded grasslands, etc.

Soil Physical Properties of Different Land Use Types in Loess Hilly Region

[Objectives]To explore the impact of land use changes on physical properties of soil in loess hilly region.[Methods]The methods of field sampling and indoor analysis were adopted.Farmland in a small watershed in the middle of the Loess Plateau,grassland that had been abandoned for 7 years,grassland that had been abandoned for 30 years,jujube orchard and ditch were sampled,and the particle composition(clay,silt and sand)and moisture changes of the soil in the top 0-100 cm were studied.[Results]In the small watershed,the top 0-100 cm of the soil was composed of 14%clay,70%silt and 16%sand.The contents of clay,silt and sand in the grassland that had been abandoned for 30 years varied greatly,while varied little in the land of other use types.The soil moisture content of grassland that had been abandoned for 30 years,jujube orchard,grassland that had been abandoned for 7 years,farmland and ditch increased with the increase of depth,with means of 10.29%,11.66%,10.08%,11.43%and 11.34%,respectively.[Conclusions]This study provides a theoretical basis for the growth of crops of different land use types in the loess hilly region.

Structure and governance model of rural social space quality:A case study of Longxi County in the Loess Hilly Area of China

The rural social space quality is an important indicator to measure the living standard and thinking ideas and so forth of rural residents in a certain region.In this paper,213 administrative villages in Longxi County of the Loess Hilly Area,China are taken as evaluation units to construct the evaluation model of the rural social space quality.This paper deeply analyzed the variation patterns and their formation mechanism of the rural social space quality at a village scale,and proposed a governance model based on the rural social space quality.The results show that:(1)the social space quality levels of individual administrative villages show a gradually decreasing trend from the township seats to outward.The eastern part of Longxi County has a relatively high education level and living standard,and the western part has a relatively high population stability level and income level.(2)The rural social space quality is mainly in a ring structure,supplemented by the interlaced structure.The core area is the towns and their surrounding areas,while the transition area,marginal area,and other areas are expanded around the core area.(3)Social forces and spatial effects jointly shape the variation of the rural social space quality.Social organizations provide a driving force for the allocation of elements,and interweaving with the spatial effects lead to the differences in the social space quality.(4)The governance models of the rural social space quality are constructed based on the principles of retaining the rural“people”,optimizing the rural“land”,and developing the rural“industry”,so as to improve the rural centripetal force,core force,inner thrust,and source power.

Characteristics of soil nutrients and their relationship with soil microbial properties in Artemisia sacrorum communities in the loess hilly region

Artemisia sacrorum communities with different growth years were selected to analyse soil nutrient characteristics,the variation in soil microbial properties,and their relationships in the loess hilly region.The results showed that with an increase in the number of growth years,soil microbial biomass carbon and nitrogen contents as well as soil phosphatase and urease activities initially decreased and then increased in the A.sacrorum communities.The soil organic carbon,organic nitrogen,and total nitrogen contents as well as soil respiration rate showed an increasing trend and reached a maximum at age(a)37.The soil available phosphorus content first decreased and then increased,with the lowest level observed at 18 a.By contrast,soil available potassium initially increased and then decreased.Soil microbial biomass carbon had a significant positive correlation with soil organic carbon,total nitrogen and organic nitrogen,while soil respiration had a significant positive correlation with organic nitrogen,soil phosphatase and organic carbon.Soil respiration had a highly significant positive correlation with organic carbon and total nitrogen,while soil phosphatase had a highly significant positive correlation with total nitrogen and organic nitrogen.In the A.sacrorum communities,the soil organic carbon and total nitrogen contents were mainly affected by soil respiration,soil available potassium content was mainly affected by soil urease activity,and soil organic nitrogen content was mainly affected by soil phosphatase activity.These findings indicate that soil basal respiration,urease activity and phosphatase activity were the major microbial factors affecting the characteristics of the soil nutrients in the A.sacrorum communities.In conclusion,the natural restoration process of A.sacrorum communities can enhance soil microbial activity and improve soil quality.

Effect of Root Architecture on Structural Stability and Erodibility of Topsoils during Concentrated Flow in Hilly Loess Plateau

Traditional vegetation techniques for the control of concentrated flow erosion are widely recognized, whereas only a few studies have experimentally investigated the impacts of belowground roots on the erodibility of topsoils in semi-arid areas. To quantify the effects of root architectures on soil erodibility and its relevant structural properties, simulated flow experiments were conducted at six-week intervals from 18 July to 20 October in 2012 in the hilly Loess Plateau. Five treatments were: 1) bare(control), 2) purple alfalfa(Medicago sativa), representing tap roots(T), 3) switchgrass(Panicum virgatum), representing fibrous roots(F), 4) purple alfalfa and switchgrass, representing both tap and fibrous roots(T + F), and 5) natural recovery(N). For each treatment, soil structural properties and root characteristics were measured at an interval of six weeks. Soil anti-scouribility was calculated. Results showed that grass planting slightly reduced soil bulk density, but increased soil aggregate content by 19.1%, 10.6%, 28.5%, and 41.2% in the treatments T, F, T + F, and N, respectively. Soil shear strength(cohesion and angle of internal friction(φ)) significantly increased after the grass was planted. As roots grew, soil cohesion increased by 115.2%–135.5%, while soil disintegration rate decreased by 39.0%–58.1% in the 21 th week compared with the recorded value in the 9th week. Meanwhile, root density and root surface area density increased by 64.0%–104.7% and 75.9%–157.1%, respectively. No significant differences in soil anti-scouribility were observed between the treatments of T and F or of T + F and N, but the treatments of T + F and N performed more effectively than T or F treatment alone in retarding concentrated flow. Soil aggregation and root surface-area density explained the observed soil anti-scouribility during concentrated flow well for the different treatments. This result proved that the restoration of natural vegetation might be the most appropriate strategy in soil reinforcement in the hilly Loess Plateau.

Aridity trend and response to vegetation restoration in the loess hilly region of northern Shaanxi Province

Detecting variation trend in dry-wet conditions can provide information for devel- oping strategic measures to mitigate the impacts of global warming, particularly in dry regions Taking the hilly region of northern Shaanxi on the Loess Plateau as a case area, this study analyzed the trend of aridity variation during 1981-2012, and explored the effect of vegetation restoration promoted by the Grain-for-Green （GFG） program implemented in 1999. The re- sults indicated that the aridity in the region was non-significantly increased by 0.88% per year during 1981-2012, showing a drying trend. This drying trend and amplitude were changed by the influence of vegetation restoration promoted by the GFG program, based on two findings. The first one was that the aridity variation tended to increase during 1981-1999 while it turned to decrease during 2000-2012, with the regional mean relative change rate changed from 2.45% to -1.06%. This distinction was more remarkable in the loess gully region, where the vegetation was improved more obviously. The second one was that the mean vegetation coverage as indicated by EVI increased by 0.90% to 4.32% per year at county level, while the aridity decreased by 0.14% to 2.32% per year during 2000-2012. The regression analysis using the mean county data indicated that the change rate of aridity was negatively related to that of EVI with the coefficient of determination （R2） of 0.56, illustrating that around half of the aridity decline was explained by the EVI change. The mechanism of this effect was compli- cated, but it was found that the wind speed decline induced by the vegetation improvement could be an important contributor. It is concluded that the region became drier during 1981-2012, but the eco-restoration reduced the drying speed. However, this conclusion is involved in uncertainties, and further study based on experiments is needed to confirm the effect of the GFG-promoted vegetation restoration.

Response of soil respiration to environmental and photosynthetic factors in different subalpine forest-cover types in a loess alpine hilly region

Soil respiration(Rs)is important for transport-ing or fixing carbon dioxide from the atmosphere,and even diminutive variations can profoundly influence the carbon cycle.However,the R_(s) dynamics in a loess alpine hilly region with representative sensitivity to climate change and fragile ecology remains poorly understood.This study investigated the correlation and degree of control between R_(s) and its photosynthetic and environmental factors in five subalpine forest cover types.We examined the correlations between R_(s) and variables temperature(T_(10)) and soil moisture content at 10 cm depth(W_(10)),net photosynthetic rate(P_(n))and soil properties to establish multiple models,and the variables were measured for diurnal and monthly vari-ations from September 2018 to August 2019.The results showed that soil physical factors are not the main drivers of R_(s) dynamics at the diel scale;however,the trend in the monthly variation in R_(s) was consistent with that of T_(10)and P_(n).Further,R_(s) was significantly affected by pH,providing further evidence that coniferous forest leaves contribute to soil acidification,thus reducing R_(s).Significant exponential and linear correlations were established between R_(s) and T_(10)and W_(10),respectively,and R_(s) was positively correlated with P_(n).Accordingly,we established a two-factor model and a three-factor model,and the correlation coefficients(R_(2))was improved to different degrees compared with models based only on T_(10) and W_(10).Moreover,temperature sensitivity(Q_(10))was the highest in the secondary forest and lowest in the Larix principis-rupprechtii forest.Our findings suggest that the control of R_(s) by the environment(moisture and tempera-ture)and photosynthesis,which are interactive or comple-mentary effects,may influence spatial and temporal homeo-stasis in the region and showed that the models appropriately described the dynamic variation in R_(s) and the carbon cycle in different forest covers.In addition,total phosphorus(TP)and total potassium(TK)significantly affected the dynamic changes in R_(s).In summary,interannual and seasonal variations in forest R_(s) at multiple scales and the response forces of related ecophysiological factors,especially the interactive driving effects of soil temperature,soil moisture and photo-synthesis,were clarified,thus representing an important step in predicting the impact of climate change and formulating forest carbon management policies.

Study on the Climate Changes Characteristics in the Hilly Region of the Loess Plateau and Its Influence on Agricultural Production

[Objective] The aim was to study the climate changes characteristics in the hilly region of the loess plateau and its influence on agricultural production.[Method] Taking Yan’an City as an example,and by dint of temperature and precipitation in nine meteorological stations from 1957 to 2007 and accumulated anomaly curve,linear regression and relevant analysis,the climate changes characteristics in 51 years in Yan’an were expounded.The climate changes in the hilly region of the loess plateau were studied and its influences on agricultural production were concluded.[Result] The characteristics of climate changes in the hilly region were as follow:high temperature in winter and warm winter trend was clearly;the temperature in spring enhanced fast and the drought disaster was increasing worse;rainy days occurred now and then in autumn.The climate changes had different levels of influences on agricultural production in Yan’an City.Because of rising temperature in winter,facility agriculture was vigorously developed and the apple range expanded;in the meantime,because of rising temperature in spring,drought was worsen and sowing in spring can not proceed;constant rain in autumn damaged the quality of date.[Conclusion] The study provided theoretical basis for the regional agricultural production and agricultural structure adjustment.

Hydrological cycle research by D&^(18)O tracing in small watershed in the loess hilly region

The objective of this study was to determine the mechanisms of the hydrologic cycle in the loess area in China.Sixty eight water samples from precipitation,soil water of the 0-4 m layer,surface water in the valley,ground water(spring and well)were collected and the Deuterium(D)and Oxygen-18(^(18)O)of these water samples were analyzed to interpret the relationship among those waters in the watershed in the loess hilly region during 2005-2009.The results show that:the D&^(18)O of precipitation in Yangou was consistent with that of Xi,an,apparently the north migration of water vapor in Xi^an;according to the correlations among the differential waters in D&^(18)O,confirmed that precipitation recharge could account for most of the sources of valley flow,with part of the recharge water going to soil water recharge.The D&^(18)O of groundwater were very close to that of precipitation,likely the soil preferential flow was dominant in groundwater recharge although the infiltration had a certain lag.Under the influence of rainfall and evaporation,the response of the soil moisture profile,and its D&^(18)O profile were different.The soil moisture had the strong influenced layer in the 60-160 cm range,a weak impacted layer in 60 l60 cm,and a stable layer below l60 cm.It was shown that the soil evaporation depth could be up to l60 cm because the D&^(18)O changed in that depth.The study could increase our understanding of the magnitude and pattern of the hydrologic cycle,which should improve water resources management in the watershed scale.

An applied research on remote sensing classification in the Loess Plateau

Dae to complex terrain of the Loess Plateau, the classification accuracy is unsatisfactory when a single supervised classification is used in die remote sensing investigation of the sloping field. Taking the loess hill and gully area of northern Shaanxi Province as a test area, a research was conducted to extract sloping field and other land use categories by applying an integrated classification. Based on an integration of supervised classification aad unsupervised classification, sampling method is remarkably unproved. The results show that the classification accuracy is satisfactory by the method and is of critical significance in obtaining up-to-date information of the sloping field, which should be helpful in the state key project of converting farmland to forest and grassland on slope land in this area. This research sought to improve the application accuracy of image classification in complex terrain areas.

Freeze–thaw effects on erosion process in loess slope under simulated rainfall

Seasonal freeze–thaw processes have led to severe soil erosion in the middle and high latitudes.The area affected by freeze–thaw erosion in China exceeds 13%of the national territory.So understanding the effect of freeze–thaw on erosion process is of great significance for soil and water conservation as well as for ecological engineering.In this study,we designed simulated rainfall experiments to investigate soil erosion processes under two soil conditions,unfrozen slope(UFS)and frozen slope(FS),and three rainfall intensities of 0.6,0.9 and 1.2 mm/min.The results showed that the initial runoff time of FS occurred much earlier than that of the UFS.Under the same rainfall intensity,the runoff of FS is 1.17–1.26 times that of UFS;and the sediment yield of FS is 6.48–10.49 times that of UFS.With increasing rainfall time,rills were produced on the slope.After the appearance of the rills,the sediment yield on the FS accounts for 74%–86%of the total sediment yield.Rill erosion was the main reason for the increase in soil erosion rate on FS,and the reduction in water percolation resulting from frozen layers was one of the important factors leading to the advancement of rills on slope.A linear relationship existed between the cumulative runoff and the sediment yield of UFS and FS(R2>0.97,P<0.01).The average mean weight diameter(MWD)on the slope erosion particles was as follows:UFS0.9(73.84μm)>FS0.6(72.30μm)>UFS1.2(72.23μm)>substrate(71.23μm)>FS1.2(71.06μm)>FS0.9(70.72μm).During the early stage of the rainfall,the MWD of the FS was relatively large.However,during the middle to late rainfall,the particle composition gradually approached that of the soil substrate.Under different rainfall intensities,the mean soil erodibility(MK)of the FS was 7.22 times that of the UFS.The ratio of the mean regression coefficient C2(MC2)between FS and UFS was roughly correspondent with MK.Therefore,the parameter C2 can be used to evaluate soil erodibility after the appearance of the rills.This article explored the influence mechanism of freeze–thaw effects on loess soil erosion and provided a theoretical basis for further studies on soil erosion in the loess hilly regions.

ECO-ENVIRONMENT CHANGE AND SOIL EROSION PROCESS IN THE RECLAIMED FORESTLAND OF THE LOESS PLATEAU

Serious soil erosion has made the eco-environment fragile in the Loess Plateau. Based on the 10-year data observed from 1989 to 1998 in the Ziwuling Survey Station in loess hilly region, the eco-environment change and soil erosion process in reclaimed forestland were studied in this paper. The results showed that the intensity of man-made soil erosion caused by forestland reclamation was 1000 times more than that of the natural erosion. From the analysis of soil physical and mechanical properties, in the 10th year after forestland was reclaimed, the clay content and physical clay content decreased 2.74 percentage point and 3.01 percentage point respectively, the >0.25mm waterstable aggregate content decreased 31.59 percentage point, the soil bulk density increased and soil shear strength decreased, all of which were easier to cause soil erosion. The correlation analysis showed that >0.25mm waterstable aggregate content was the key factor affecting soil erosion, and the secondary factors were soil coarse grain and soil shear strength. The relation between the >0.25mm waterstable aggregate content, the soil sheer strength and the soil erosion intensity were analyzed, which showed that the first year and the seventh erosion year were the turn years of the soil erosion intensity after the forestland was reclaimed, revealed that the change of eco-environment was the main cause to accelerate soil erosion, and the worse environment caused soil erosion to be serious rapidly.

Spatial Equity Evaluation of Rural Eldercare Service Resources Based on Accessibility: A Case Study of Huanxian County of Gansu Province, China

Safeguarding the elderly population in the countryside is an inherent requirement for alleviating social conflicts in rural areas and effectively carrying out China’s Rural Revitalization.The existing spatial mismatch between rural elderly service facilities and pop-ulation distribution in China aggravates the imbalance of facility resource space,how to improve the accuracy of demand and supply results and better measuring the spatial fairness of elderly service is significant to realize the optimal allocation of rural elderly service.Based on the above,this study pays attention to the refined needs of the elderly population,and focuses on the spatial equity of the rural elderly facilities,to make up for the short boards of the basic public services in the countryside and realize the all-round rural revitalization.This study takes Huanxian County in the hilly loess area of Longdong,China as an example and explores the spatial equity of rural elderly services by using the Urban Spatial Network Analysis(UNA)to measure the accessible quantity and supply capacity of elderly services.The results found that there were 553 rural eldercare service facilities in Huanxian County,including 285 eldercare facilities and 268 medical and health facilities,and the spatial distribution is characterized by a southward shift in the east and uneven regional distribution.Overall,the supply capacity of rural pension services was generally good,with the township center as the gathering point and spreading out in a faceted manner,with nearby townships forming a contiguous area;however,there were strong contrasts and obvious differences in the strength of supply capacity.However,the spatial equity of rural eldercare service was poor.In 42.05%of the eld-erly population grid cells,eldercare service spatial equity was extremely low.The spatial distribution also presented a northern preference over the southern,a western preference over the eastern,and a concentration along the highway.The study explored the realization of spatial equity in the optimal allocation of rural elderly services based on paying attention to the refined needs of the rural elderly pop-ulation,a vulnerable group,to provide a reference for solving the shortcomings of basic public services in rural areas.The fair allocation of rural elderly services demands that the spatial optimization of facility layout be organically coordinated with policy,management,and post-maintenance,and all elements in the rural territorial system be fully mobilized to achieve the basic guarantee of China’s rural elderly problems.

The effects of land use and its patterns on soil properties in a small catchment of the Loess Plateau

Due to relatively strong human activities in the hilly area of Loess Plateau, the natural vegetation has been destroyed, and landscape pattern based on agricultural land matrix was land use mosaic composing of shrub land, grassland, woodland and orchard. This pattern has an important effect on soil moisture and soil nutrients. The Danangou catchment, a typical small catchment, was selected to study the effects of land use and its patterns on soil moisture and nutrients in this paper. The results are as follows: The comparisons of soil moisture among seven land uses for wet year and dry year were performed: (1) the average of soil moisture content for whole catchment was 12.11% in wet year, while it was 9.37% in dry year; (2) soil moisture among seven land uses was significantly different in dry year, but not in wet year; (3) from wet year to dry year, the profile type of soil moisture changed from decreasing type to fluctuation-type and from fluctuant type to increasing type; (4) the increasing trend in soil moisture from the top to foot of hillslope occurred in simple land use along slope, while complicated distribution of soil moisture was observed in multiple land uses along slope. The relationships between soil nutrients and land uses and landscape positions were analysed: (1) five nutrient contents of soil organic matter (SOM), total N (TN), available N (AN), total P (TP) and available P (AP) in hilly area were lower than that in other areas. SOM content was less than 1%, TN content less than 0.07%, and TP content between 0.05% and 0.06%; (2) SOM and TN contents in woodland, shrub land and grassland were significantly higher than that in fallow land and cropland, and higher level in soil fertility was found in crop-fruit intercropping land among croplands; (3) soil nutrient distribution and responses to landscape positions were variable depending on slope and the location of land use types.

Application of ^(137)Cs fingerprinting technique to interpreting sediment production records from reservoir deposits in a small catchment of the Hilly Loess Plateau,China

According to variations of 137Cs and clay contents, 44 flood couplets were identified in a profile of res- ervoir deposit with a vertical length of 28.12 m in the Yuntaishan Gully. Couplet 27 at the middle of the profile had the highest average 137Cs content of 12.65 Bq·kg?1, which indicated the 1963s' deposits, then 137Cs content decreased both downward and upward in the profile. The second top and bottom couplets had average 137Cs contents of 2.15 Bq·kg?1 and 0.92 Bq·kg?1, respectively. By integrated analysis of reservoir construction and management history, variations of 137Cs contents over the profile, sediment yields of flood couplets and rainfall data during the period of 1958-1970, individual storms related to the flood couplets were identified. 44 floods with a total sediment yield of 2.36×104 m3 occurred and flood events in a year varied between 1 and 10 times during the period of 1960-1970. 7-10 flood events occurred during the wet period of 1961-1964 with very wet autumn, while only 1-2 events during the dry period of 1965-1969. Average annual specific sediment yield was 1.29×104 t·km?2·a?1 for the Yuntaishan Gully during the period of 1960-1970, which was slightly higher than 1.11 ×104 t·km?2·a?1 for the Upper Yanhe River Basin above the Ganguyi Hydrological Station and slightly lower than 1.40 ×104 t·km?2·a?1 for the nearby Zhifang Gully during the same period. Annual specific sediment yields for the Yuntaishan Gully were correlated to the wet season's rainfalls well.

Effects of soil drought on photosynthetic traits and antioxidant enzyme activities in Hippophae rhamnoides seedlings

Water deficit is one of the major limiting factors in vegetation recovery and reconstruction in the semi-arid area of loess hilly regions. Leaf photosynthesis in Hippophae rhamnoides Linn., a common tree grown in this region, decreases under water stress, but the mechanism responsible is not clear. The objective of this study was to investigate the effects of drought stress on photosynthesis and the relationship between photosynthetic variables and soil water contents to help us better understand the photophysiological characteristics of H. rhamnoides under water stress and guide cultivation in the loess hilly region. Here,gas exchange, chlorophyll fluorescence and antioxidant enzyme activity in leaves of 3-year-old saplings of H.rhamnoides grown in pots were tested under eight soil water conditions. When soil water content（RWC） was between 38.9 and 70.5 %, stomatal limitation was responsible for the reduced net photosynthetic rate（PN）.When RWC was lower than 38.9 %, nonstomatal limitation was the main factor restricting PN. Moderate water stress improved the water use efficiency（WUE） of the leaf.Water stress significantly influenced fluorescence variables and the antioxidant enzyme system. When RWC was between 38.9 and 70.5 %, nonphotochemical quenching（NPQ） increased and then decreased, indicating that thermal energy dissipation was a significant photoprotection mechanism. Antioxidant enzymes were activated when RWC ranged from 48.3 to 70.5 %; under severe water stress（RWC ／ 38.9 %）, the antioxidant enzyme system was damaged, the activity of the antioxidant enzymes declined, and membranes were damaged. In the semiarid loess hilly region, RWC between 58.6 and 70.5 % was the economic water threshold value that maintained higher WUE and PN, and the maximum soil water deficit level that could sustain H. rhamnoides was RWC of 38.9 %.