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.

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.

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.

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.

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.

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.

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.

持续强降雨影响下黄土高原地形变化分布特征——以延安市顾屯流域为例

As China's Loess Plateau has lately witnessed increasingly extreme precipitation events,it is important to analyze the impact of extreme precipitation and identify the conditions for the occurrence of geological disasters.Field surveys can provide detailed geological information in this regard but are time consuming and labor intensive.In this paper,we provide a case study on the Gutun catchment of Yan'an,which was affected by prolonged heavy rainfall in July 2013.We used Digital Elevation Model(DEM)data obtained by processing ZY-03 stereo-pair images before and after the rainy season,including the period of prolonged heavy rainfall mentioned above,to analyze the topographical changes triggered by the rainfall.The results showed the following:(1)The rainy season reduced the elevation of the catchment by about 1.7 cm.The major change in its elevation ranged from-0.5 to 0 m,accounting for 38.41%of the overall area of change and dominating above 70 m of slope height.(2)The rainy season increased the average inclination of the slopes in the area from 28.81°to 28.95°,while the range of their peak inclination was mainly distributed in the range of 24°-36°.(3)Sunny and half-sunny slopes exhibited a greater loss in elevation,while shady and half-shady slopes exhibited an increase in elevation.More drastic topographical changes were observed in the shady and half-shady slopes.(4)The morphology of the area that had undergone a reduction in elevation was characterized by concave slopes,while convex slopes abounded in the area with increased elevation.(5)The sunny or shady properties of the slope aspect constituted the key factor influencing the topographical changes,followed by the height,inclination,and shape of the slopes.The work here can provide guidance for measures related to disaster prevention and mitigation.

适配性重要吗?对乡村社会空间与乡村生活圈的特征与关系进行分析

The construction of rural life circle has an essential impact on the change of rural social space.Analyzing the adaptation relationship between the two can be a new content in the study of “physical-social” space.Using social behavior as a link,we construct a logical relationship framework between rural life circle and social space.Based on the survey data of Baijia village in the loess hilly region,this paper analyzes the characteristics and adaptability of the two and discusses preliminary ideas of life circle reorganization and social space reconstruction.The study results are as follows:(1) Based on the location of four types of service facilities and the travel mode of villagers,two life circles of 15 min and 25 min have been formed in Baijia village.The rural social spaces such as communicative behavior space,health seeking behavior space,leisure behavior space,and consumption behavior space show a specific concentric circle structure and unique hierarchical structure.(2) The analysis of the adaptation between them shows that the 15 min life circle in Baijia village has a high level of adaptation to communicative and leisure behavior spaces.It plays a positive feedback role in the construction of social space.However,it has a low level of adaptability to the space of health seeking and consumption behavior spaces and has a negative feedback effect on the construction of social space.The 25 min life circle is the opposite.(3) The reorganization of facility layout,hierarchical structure,and service functions in the village life circle will lead to changes in the range,frequency,and purpose of villagers’ behavioral activities,resulting in a new social spatial pattern.These findings are important for formulating village development and construction plans,improving the settlement habitat,and reconstructing the order of social life.

黄土丘陵区雨强对水流含沙量的影响

To study the effects of changes in the rainfall intensity on sediment concentrations in the Loess Plateau,the observed rainfall intensities and sediment concentrations from three typical small watersheds were used to analyze the relationship between these parameters.The results showed that the sediment concentration generally increased with the increasing rainfall intensity on slope scale.However,at watershed scale,a significant threshold phenomenon was observed for the effects of the rainfall intensity on the sediment concentration.When the rainfall intensity exceeds the threshold,the flood sediment concentration will no longer increase with the increase in the rainfall intensity.The rainfall intensity threshold increased with increasing vegetation coverage.The rainfall intensity threshold was 10–15 mm/h during 1956–1969,reached 20 mm/h from 1990 to 1997 and is approximately 40 mm/h at present.Due to a rainfall intensity of 10–15 mm/h almost happened every year,the vegetation did not change much from the 1950s to 1980s.Sediment yield mainly depends on soil erosion caused by surface flow,but the surface flow speed does not increase indefinitely with the increase in the flow discharge.Thus,the annual maximum sediment concentration of the tributaries in the loess area has been basically stable before the 1990s.