Impacts of multi-scenario land use change on ecosystem services and ecological security pattern: A case study of the Yellow River Delta

The Yellow River Delta(YRD), a critical economic zone along China's eastern coast, also functions as a vital ecological reserve in the lower Yellow River. Amidst rapid industrialization and urbanization, the region has witnessed significant land use/cover changes(LUCC), impacting ecosystem services(ES) and ecological security patterns(ESP). Investigating LUCC's effects on ES and ESP in the YRD is crucial for ecological security and sustainable development. This study utilized the PLUS model to simulate 2030 land use scenarios, including natural development(NDS), economic development(EDS), and ecological protection scenarios(EPS). Subsequently, the InVEST model and circuit theory were applied to assess ES and ESP under varying LUCC scenarios from 2010 to 2030. Findings indicate:(1) Notable LUCC from 2010 to 2030, marked by decreasing cropland and increasing construction land and water bodies.(2) From 2010 to 2020, improvements were observed in carbon storage,water yield, soil retention, and habitat quality, whereas 2020–2030 saw increases in water yield and soil retention but declines in habitat quality and carbon storage. Among the scenarios, EPS showed superior performance in all four ES.(3) Between 2010 and 2030, ecological sources, corridors, and pinchpoints expanded, displaying significant spatial heterogeneity. The EPS scenario yielded the most substantial increases in ecological sources,corridors, and pinchpoints, totaling 582.89 km^(2), 645.03 km^(2),and 64.43 km^(2), respectively. This study highlights the importance of EPS, offering insightful scientific guidance for the YRD's sustainable development.

Factors Influencing the Thermal Conductivity of Silt in the Yellow River Delta

The thermal conductivity of marine sediments is an important thermophysical parameter in the study of seafloor heat flow and marine engineering construction.Understanding the effect of thermal conductivity of marine sediments in the environment has a major engineering value and theoretical significance.In this work,a modified test method was used to measure the thermal conductivity of silt in the Yellow River Delta under different void ratios,moisture contents,temperatures,and salinities.Results showed that the thermal conductivity of silt in the Yellow River Delta decreased with the increase in the void ratio and increased with the water content.Compared with sand and clay,silt in the Yellow River Delta was the least affected by the void ratio and moisture content.Under low temperatures,the heat transfer of soil was controlled by the average velocity of the phonons;therefore,the thermal conductivity of silt in the Yellow River Estuary increased with temperature.The thermal conductivity of pore water decreased with increasing salinity.Moreover,certain salinity levels resulted in a phenomenon known as the‘compressing twin electrical layer’,which led to an increase in the contact area between soil particles.With the increase in salinity,the thermal conductivity of silt in the Yellow River Delta experiences an initial decline and a subsequent increase.The proposed thermal conductivity test method is more accurate than the existing technique,and the findings provide a basis for further study on the thermal characteristics of submarine sediments.

Effect of Hydrological Connectivity on Soil Carbon Storage in the Yellow River Delta Wetlands of China

Hydrological connectivity has significant effects on the functions of estuarine wetland ecosystem.This study aimed to examine the dynamics of hydrological connectivity and its impact on soil carbon pool in the Yellow River Delta,China.We calculated the hydrological connectivity based on the hydraulic resistance and graph theory,and measured soil total carbon and organic carbon under four different hydrological connectivity gradients(Ⅰ0‒0.03,Ⅱ0.03‒0.06,Ⅲ0.06‒0.12,Ⅳ0.12‒0.39).The results showed that hydrological connectivity increased in the north shore of the Yellow River and the south tidal flat from 2007 to 2018,which concentrated in the mainstream of the Yellow River and the tidal creek.High hydrological connectivity was maintained in the wetland restoration area.The soil total carbon storage and organic carbon storage significantly increased with increasing hydrological connectivity fromⅠtoⅢgradient and decreased inⅣgradient.The highest soil total carbon storage of 0‒30 cm depth was 5172.34 g/m^(2),and organic carbon storage 2764.31 g/m^(2)inⅢgradient.The hydrological connectivity changed with temporal and spatial change during 2007‒2018 and had a noticeable impact on soil carbon storage in the Yellow River Delta.The results indicated that appropriate hydrological connectivity,i.e.0.08,could effectively promote soil carbon storage.

Causes of Wetland Degradation and Ecological Restoration in the Yellow River Delta Region

Yellow River delta （YRD） is one of the biggest deltas that there is a large area of wetland in the world. Thanks to soil （sands） sediment carried by the Yellow River, there was averagely the newly formed land 21.3 km^2 in YRD. During the development of petroleum industry and urban expansion, wetlands were degraded due to population growth, irrational land use, in addition to adverse natural eco-environment such as lower precipitation, higher soil evaporation and soil salinazation. The major ecological measures to restore degraded wetland concerned with ensuring water supply, especially establishing perfect irrigation works; protecting virgin plant communities and assisting them to regenerate by the way of site preparation, improving living surroundings; introducing salt-tolerant plants to increase vegetation species and plant coverage, thereby enhancing the capability of wetland to combat contamination and pollution through plant remediation, uptake, absorption, etc. Finally making a comprehensive land use plan, accordingly removing deleterious facilities.

Spatial and environmental effects on plant communities in the Yellow River Delta,Eastern China

Types and structure of plant communities in the Yellow River Delta were investigated by using detrended canonical correspon-dence analyses(DCCAs) and a two-way indicator species analysis(TWINSPAN).The distribution pattern and influential factors of the plant communities were also analyzed by testing elevation, slope, soil characteristics, longitude and latitude of 134 vegetation samples collected by representative plot sampling methods.Results showed that all the 134 vegetation samples could be divided into seven vegetation groups, separately dominated by Robinia pseucdoacacia, Imperata cylindrical, Miscanthus saccharifleus, Suaeda salsa, Aeluropus sinensis, Phragmites australis and Tamarix chinensis.The vegetation distribution pattern was mainly related to elevation, ground water depth and soil characteristics such as salinity and soluble potassium.Among the factors affecting distribution pattern of the plant communities, the species matrix explained by non-spatial environmental variation accounts for 45.2% of total variation.Spatial variation and spatial-structured environmental variation explain 11.8%, and 2.2%, respectively.Remained 40.8% of undetermined variation is attributed to biological and stochastic factors.

Biogenic Sedimentary Structures of the Yellow River Delta in China and Their Composition and Distribution Characters

The biogenic sedimentary structures （i.e., the morphology and trace makers of burrows, tracks, trails and traces made by extant organisms） and their composition and distribution characters in different micro environments and sub environments of the Yellow River delta in China are described. Three ichnocoenosis can be recognized： （1） Steinichnus-like ichnocoenosis, includes F, Y-shaped traces, birds＇ footprints on bedding plane, and Y, U-shaped burrows in intrastratal bedding, produced by Coleoptera （Heteroceridae）, Orthoptera （Gryllotalpidae） and birds. It is majorly found at the delta plain point bar deposits, denoting the fresh water-related terrestrial environments. （2） Steinichnus-Psilonichnus-like ichnocoenosis, consitsis of Steinichnus-like traces on the bedding plane and Psilonichnus-like burrow which a vertical, irregularly J-, Y-, or U-shaped burrows, some of them with bulbous basal cells burrows in the intrastratal bedding, created by Coleoptera （Heteroceridae）, Orthoptera （Gryllotalpidae） and crabs. It is observed in the delta plain abandoned distributary channels, and the delta front tidal creek and subaquous distributary channels, indicating the brackish water environment. （3） Palaeophycus-like ichnocoenosis, includes the round entrance burrows or with craters-shaped loop-protrusionsand and the parallel forked trails on the bedding plane, and the U, J or vertical shaped feeding burrows are in the intrastratal bedding, majorly produced by the clam （bivalve molluscs）, gastropods and Nereis. It is present in the subaqueous interdistributary bay, reflecting the intertidal related environment.

Dynamic analysis of evapotranspiration based on remote sensing in Yellow River Delta

Evapotranspiration (ET) is an important parameter for water resource management. Compared to the traditional ET computation and measurement methods, the ET computation method based on remote sensing has the advantages of quickness, precision, raster mapping and regional scale. SEBAL, an ET computation model using remote sensing method is based on the surface energy balance equation which is a function of net radiance flux, soil heat flux, sensible heat flux and latent heat flux. The former three fluxes can be computed through the parameters retrieved from remote sensing image, then the latent heat flux can be obtained to provide energy for ET. Finally we can obtain the daily ET. In this study SEBAL was applied to compute ET in the Yellow River Delta of China where water resource faces a rigorous situation. Three Landsat TM images and meteorology data of 1999 were used for ET computation, and spatial and temporal change patterns of ET in the Yellow River Delta were analysed.

Saline-alkali land in the Yellow River Delta: amelioration zonation based on GIS

Soil salinization is one of the major land degradation types and has greatly influenced sustainable agricultural development. Zonation of saline-alkali land is the precondition for effective amelioration. The present situation of saline-alkali land is monitored by remote sensing image processing. Causes for land salinization are analyzed, especially the two key factors, ground water depth and its mineralization degree, are analyzed by using long-term observation data. Previously, zonation of saline-alkali soil was made descriptively and artificially. Based on the present situation of saline-alkali land, ground water depth and ground water mineralization degree, the zonation of saline-alkali land for amelioration in the Yellow River Delta was completed quantitatively. Four different types of saline-alkali land amelioration zones are delineated, namely, easy ameliorated zone, relatively difficult ameliorated zone, difficult ameliorated zone and unfavorable ameliorated zone. Countermeasures for ameliorating saline-alkali soils are put forward according to ecological conditions of different saline-alkali land zones.

Effects of Tidal Channels and Roads on Landscape Dynamic Distribution in the Yellow River Delta, China

Landscape characters in estuarine regions generally controlled by tidal regimes and human activities like road construction.In this work,tidal channels and road construction in the Yellow River Delta(YRD)were extracted by visual interpretation methods so as to decipher impacts of tidal channel development and road construction on landscape patch change during 1989–2016.Spatial distribution history of three wetlands,which covered by Phragmites australis(freshwater marsh,FM),Suaeda salsa(salt marsh,SM),and mudflats(MD)were also established.Results indicated that tidal channel,number,frequency,and fractal dimension were all the maximum in 2003,and the minimum in 1998,respectively.Road length,number,and density showed increasing trend during 1989–2016.MD were the predominant landscape type,followed by FM and SM during 1989-2016.Principal component analysis implied two extracted factors,F1 and F2,which could represent 91.93% of the total variations.F1 mainly proxied tidal channel development,while F2 represented road construction.A multiple linear regression analysis showed positive effects of both F1 and F2 on FM patch numbers and negative impacts on SM patch areaes with R^2 values of 0.416 and 0.599,respectively.Tidal channels were negatively related to MD patch numbers,while roads were positively related to that.In any case,road construction showed larger impacts on landscape type shifting than that of tidal channel development in the YRD.

Increased salinity and groundwater levels lead to degradation of the Robinia pseudoacacia forest in the Yellow River Delta

Forest degradation is a worldwide problem,although its causes vary due to geographical and climatic differences and man-made causes.In recent years,the Robinia pseudoacacia forest in the Yellow River Delta has suffered severe degradation.The causative mechanisms were investigated in the field over two years,and the results show that increased forest degradation was reflected by increased tree mortality,high leaf and soil sodium salt levels and groundwater depth.Average tree diameters decreased,and leaf chlorophyll and soil microbial contents decreased.Redundancy discriminate analysis(RDA)showed that degradation of the forest was correlated positively with soil salt content,but negatively with groundwater depth.Correlation analysis showed that 0.79%–0.95%soil salt content and above 1.20 m groundwater depth caused the death of R.pseudoacacia trees due to localized anthropogenic economic activities,such as rice farming,that disrupted the original water–salt balance.Measures are recommended to prevent further degradation and restore degraded forests.

A Preliminary Study of Rill Marks in the Yellow River Delta

In recent years, the flow of the Yellow River has often been interrupted, which has resulted in exposure of channel bars and point bars, and even extensive exposure of the riverbed. Consequently, a large number of rill marks have developed. They are diverse in morphology. According to the hydrodynamic types of their formation, they can be grouped into 6 categories, i. e. the wave eroded, backwash, seepage, rain eroded, water drainage and runoff rill marks. Morphologically, they can be divided into more than ten types: the linear, tooth shaped, comb shaped, fence like, ear like, braided, branched, leaf like, flower like, root like, dendritic, net like, radial etc. Their cross sections include the broad u type (the width/depth ratio is over 2, and may reach 10—20), U type (width/depth ratio from 1 to 2), V type, Ω type and ( type. Their occurrences may be attributed to the variations in composition, grain size, color, fabric and morphology. They have 5 scales: the micro scale (length and width within 1 cm), small scale (length and width within 10 cm), medium scale (length and width ranging from 10—100cm), large scale (length and width 1—5 m) and giant-scale (length or width over 5 m).

Monitoring of winter wheat distribution and phenological phases based on MODIS time-series： A case study in the Yellow River Delta, China

Accurate winter wheat identification and phenology extraction are essential for field management and agricultural policy making. Here, we present mechanisms of winter wheat discrimination and phenological detection in the Yellow River Delta（YRD） region using moderate resolution imaging spectroradiometer（MODIS） time-series data. The normalized difference vegetation index（NDVI） was obtained by calculating the surface reflectance in red and infrared. We used the Savitzky-Golay filter to smooth time series NDVI curves. We adopted a two-step classification to identify winter wheat. The first step was designed to mask out non-vegetation classes, and the second step aimed to identify winter wheat from other vegetation based on its phenological features. We used the double Gaussian model and the maximum curvature method to extract phenology. Due to the characteristics of the time-series profiles for winter wheat, a double Gaussian function method was selected to fit the temporal profile. A maximum curvature method was performed to extract phenological phases. Phenological phases such as the green-up, heading and harvesting phases were detected when the NDVI curvature exhibited local maximum values. The extracted phenological dates then were validated with records of the ground observations. The spatial patterns of phenological phases were investigated. This study concluded that, for winter wheat, the accuracy of classification is 87.07%, and the accuracy of planting acreage is 90.09%. The phenological result was comparable to the ground observation at the municipal level. The average green-up date for the whole region occurred on March 5, the average heading date occurred on May 9, and the average harvesting date occurred on June 5. The spatial distribution of the phenology for winter wheat showed a significant gradual delay from the southwest to the northeast. This study demonstrates the effectiveness of our proposed method for winter wheat classification and phenology detection.

Formation of Equilibrium Beach Profile of the Abandoned Yellow River Delta Coast in North Jiangsu

The abandoned Yellow River Delta coast is a typical erodible silty and muddy coast in China. The paper analyses the marine dynamic characteristics and the mechanism of beach erosion of this area. Analysis and calculation show that in this sea area wave and tidal current action should be considered. Based on the above analysis, an equilibrium beach profile calculation model is developed, in which the wave-current interaction is considered while sediment supply and sediment re-deposition are neglected. The model consists of four parts: (1) calculation of wave parameters, (2) calculation of velocity due to wave-current interaction at different water depth, (3) calculation of friction velocity and shear stress at different water depths, and (4) calculation of the amount of sediment erosion, erosion intensity and variation of beach profile. Calculated results are in good agreement with observed data. Finally, the evolution tendency is discussed and the equilibrium beach profile of this coast is calculated. B

Energy partitioning and evapotranspiration in a black locust plantation on the Yellow River Delta,China

Plantations of woody tree species play a crucial role in ecological security along coastal zones.Understanding energy partitioning and evapotranspiration can reveal land–atmosphere interaction processes.We investigated energy fluxes,evapotranspiration,and their related biophysical factors using eddy covariance techniques in a black locust(Robinia pseudoacacia L.)plantation in 2016,2018,and 2019 on the Yellow River Delta.Downward longwave radiation offsets 84–85%of upward longwave radiation;upward shortwave radiation accounted for 12–13%of downward shortwave radiation.The ratio of net radiation to downward radiation was 18–19%over the three years.During the growing season,latent heat flux was the largest component of net radiation;during the dormant season,the sensible heat flux was the dominant component of net radiation.The seasonal variation in daily evapotranspiration was mainly controlled by net radiation,air temperature,vapor pressure deficit,and leaf area index.Black locust phenology influenced daily evapotranspiration variations,and evapotranspiration was greater under sea winds than under land winds because soil water content at 10-cm depth was greater under sea winds during the day.Seasonal patterns of daily evaporative fraction,Bowen ratio,crop coefficient,Priestley–Taylor coefficient,surface conductance,and decoupling coefficient were mainly controlled by leaf area index.The threshold value of daily surface conductance was approximately 8 mm sover the plantation.

Project of “Three Networks Greening” based on optimal allocation in the Yellow River Delta,China (Dongying section)

We have used the Yellow River Delta （Dongying section） as our study area to address the project of ＂Three Networks Greening＂ （TNG）. With the use of GIS technology and from an ecological point of view, an optimal allocation scheme of land resources is constructed and applied to guide the adjustment of land resources. Given this scheme, we have calculated that the area of land suitable for forest and shrubs without greening is 2256 km^2. Simultaneously, acting on the layout of the TNG project, afforestation site types are prepared and improved. Soil types, microrelief, salinity and underwater levels are combined as major classification factors and irrigation conditions as a reference to classify sites into eight types. In this way, land suitable for forest and grass is afforested given particular planting patterns. Finally, by overlaying this forestry site type map with the TNG plan map, some suggestions and strategies are proposed and used to direct the TNG project. An ecological oasis of the Yellow River Delta should be the result.

Effect of Penetration Rates on the Piezocone Penetration Test in the Yellow River Delta Silt

Partial drainage often occurs during piezocone penetration testing on Yellow River Delta silt because of its intermediate physical and mechanical properties between those of sand and clay.Yet,there is no accurate understanding for the range of penetra-tion rates to trigger the partial drainage of silt soils.In order to fully investigate cone penetration rate effects under partial drainage condi-tions,indoor 1 g penetration model tests and numerical simulations of cavity expansion at variable penetration rates were carried out on the Yellow River Delta silt.The boundary effect of the model tests and the variation of key parameters at the different cavity ex-pansion rates were analyzed.The 1 g penetration model test results and numerical simulations results consistently indicated that the penetration rate to trigger the partially drainage of typical silt varied at least three orders of magnitude.The numerical simulations also provide the reference values for the penetration resistance corresponding to zero dilation and zero viscosity at any given normalized penetration rate for silt in Yellow River Delta.These geotechnical properties can be used for the design of offshore platforms in Yel-low River Delta,and the understanding of cone penetration rate effects under the partially drained conditions would provide some technical support for geohazard evaluation of offshore platforms.

Transgressive Events since the Late Pleistocene in the Yellow River Delta: Grain-size Distribution and Palynological Results

This study deals with the relationship between sea-level changes and paleoclimatic fluctuations based on the analysis of stratigraphy, grain sizes, palynology, and radiometric dating of the Yellow River delta since the Late Pleistocene. Evidence from the sedimentary record, grain sizes, and pollen provides a paleoenvironmental history of the Late Pleistocene from the boreholes of the delta. Based on a combination of grain-size analysis with lithological studies, marine deposit units contain the intervals of 13.85–16.9, 18.5–19.69, 27.9–34.8, 36.4–37.2, 48.4–51.6, and 54.1–55.9 m, and transitional facies units contain the intervals of 10.25–13.85, 16.9–18.5, 19.69–27.9, 34.8–36.4, 37.2–48.4, 51.6–54.1, and 55.9–60 m, compared with fluvial(terrestrial facies) deposit units(3.36–10.25 m). Based on pollen analysis and pollen assemblages, there were three warm-wet periods from 9.1–0.16 ka BP, 16.1–60 ka BP, and 90.1–94.6 ka BP From the top to the bottom of the borehole, the paleoclimate has an evident fluctuation: warm and moist(Holocene Optimum) —cool and dry(Younger Dryas Event)—mild semi cool—cool and dry—warm and moist. There were three warm-wet periods from 9.1–0.16 ka BP, 16.1–60 ka BP, and 90.1–94.6 ka BP, corresponding to the Holocene Optimum stage, MIS 3, and MIS 5, respectively. The warm period allowed monsoonal evergreen and broadleaved deciduous forests that corresponded to Holocene hypsithermal climatic conditions and the Late Pleistocene climatic Optimum. Three warm-wet periods occurred in marine deposit units from 9.1–0.16 ka BP, 60.1–16.1 ka BP, and 94.6–90.1 ka BP. These periods correspond to the Cangzhou transgression, Xianxian transgression, and Huanghua transgression, respectively. From 90.1–60.1 ka BP, 17.5–9.1 ka BP, and 0. 16 ka BP–1855 AD, three dry and cold phases are recognized. The phases indicate the fluvial(flood plain) sedimentary environment, corresponding to cooler and mild dry periods based on palynological results and grain-size distribution.

Critical effects on the photosynthetic efficiency and stem sap flow of poplar in the Yellow River Delta in response to soil water

To explore the critical relationships of photosynthetic efficiency and stem sap flow to soil moisture,two-year-old poplar saplings were selected and a packaged stem sap flow gauge,based on the stem-heat balance method,and a CIRAS-2 portable photosynthesis system were used.The results show that photosynthetic rates(P_(n)),transpiration rates(T_(r)),instantaneous water use efficiency(WUE)and the stem sap flow increased initially and then decreased with decreasing soil water,but their critical values were different.The turning point of relative soil water content(W_(r))from stomatal limitation to nonstomatal limitation of P_(n)was 42%,and the water compensation point of P_(n)was 13%.Water saturation points of P_(n)and T_(r)were 64%and 56%,respectively,and the WUE was 71%.With increasing soil water,the apparent quantum yield(AQY),light saturation point(LSP)and maximum net photosynthetic rate(P_(n)max)increased first and then decreased,while the light compensation point(LCP)decreased first and then increased.When W_(r)was 64%,LCP reached a lower value of 30.7µmol m^(-2)s^(-1),and AQY a higher value of 0.044,indicating that poplar had a strong ability to utilize weak light.When W_(r)was 74%,LSP reached its highest point at 1138.3µmol·m^(-2)s^(-1),indicating that poplar had the widest light ecological amplitude and the highest light utilization efficiency.Stem sap flow and daily sap flow reached the highest value(1679.7 g d^(-1))at W_(r)values of 56%and 64%,respectively,and then declined with increasing or decreasing W_(r),indicating that soil moisture significantly affected the transpiration water-consumption of poplar.Soil water was divided into six threshold grades by critical values to maintain photosynthetic efficiency at different levels,and a W_(r)of 64-71%was classified to be at the level of high productivity and high efficiency.In this range,poplar had high photosynthetic capacity and efficient physiological characteristics for water consumption.The saplings had characteristics of water tolerance and were not drought resistant.Full attention should be given to the soil water environment in the Yellow River Delta when planting Populus.

In Situ Observation of Silt Seabed Pore Pressure Response to Waves in the Subaqueous Yellow River Delta

The in situ pore pressure response of silt under wave action is a complex process.However,this process has not been well studied because of limited field observation techniques.The dynamic response process is closely related to engineering geological hazards;thus,this process must be urgently explored.A long-term in situ observational study of the silt sediment pore water pressure response process under wave action was conducted in the subaqueous Yellow River Delta.The response characteristics of pore water pressure are affected by tidal level and wave height.Tidal level affects the overall trend of the pore water pressure response,while wave height influences the amplitude of the pore water pressure response.This study revealed a significant lag effect in the pore pressure response.The transient pore pressure in the seabed did not respond immediately to the wave-induced pressure stress on the seabed surface.This phenomenon may be attributed to the change in soil permeability.The maximum response depth was approximately 0.5 m with a 2 m wave height.A concept model of silt soil pore pressure response under different types of wave action was developed.The accumulation rate of the pore pressure is less than the dissipation rate;thus,the developed model highlights the oscillation pore pres-sure response mechanism.The highlighted response process is of considerable importance to transient liquefaction and the startup process of pore pressure response.

Simulating Potential Distribution of Tamarix chinensis in Yellow River Delta by Generalized Additive Models

There are typical ecosystems of littoral wetlands in the Yellow River Delta.In order to study the relationships between Tamarix chinensis and environmental variables and to predict T.chinensis potential distribution in the Yellow River Delta,641 vegetation samples and 964 soil samples were collected in the area in October of 2004,2005,2006 and 2007.The contents of soil organic matter,total phosphorus,salt,and soluble potassium were determined.Then,the analyzed data were interpolated into spatial raster data by Kriging interpolation method.Meanwhile,the digital elevation model,soil type map and landform unit map of the Yellow River Delta were also collected.Generalized Additive Models(GAMs) were employed to build species-environment model and then simulate the potential distribution of T.chinensis.The results indicated that the distribution of T.chinensis was mainly limited by soil salt content,total soil phosphorus content,soluble potassium content,soil type,landform unit,and elevation.The distribution probability of T.chinensis was produced with a lookup table generated by Grasp Module(based on GAMs) in software ArcView GIS 3.2.The AUC(Area Under Curve) value of validation and cross-validation of ROC(Receive Operating Characteristic) were both higher than 0.8,which suggested that the established model had a high precision for predicting species distribution.