p-ISSN: 0972-6268 Nature Environment and Pollution Technology (Print copies up to 2016) Vol. 19 No. 4 pp. 1435-1442 2020 An International Quarterly Scientific Journal e-ISSN: 2395-3454

Original Research Paper Originalhttps://doi.org/10.46488/NEPT.2020.v19i04.009 Research Paper Open Access Journal Spatial and Temporal Changes and Driving Factors of Desertification in the Source Region of the ,

Q. G. Liu*† and Y. F. Huang** *Department of Tourism and Geography, Hefei University, Hefei 230601, China ** Department of Biology Food and Environment, Hefei University, Hefei 230601, China †Corresponding author: Q. G. Liu; [email protected]

ABSTRACT Nat. Env. & Poll. Tech. Website: www.neptjournal.com The source region of the Yellow River, located in the north-eastern edge of the -Tibet Plateau, is an important water conservation region and ecological barrier of the Yellow River. In this paper, based Received: 03-12-2019 Revised: 21-01-2020 on remote sensing technology, multi-period Landsat remote sensing images in the source region were Accepted: 01-03-2020 taken as the main information source. With the assistance of field investigation, we monitored the spatial and temporal changes of desertification in the source region from 2000 to 2019. The results Key Words: show that the area of desertification in the source region has accounted for 9.36% of the total area, of Yellow river which the light desertification land is the major portion. The desertification is mainly distributed between Desertification the southern margin of Madoi Valley basin and the northern margin of Heihe Valley basin, and is Spatial and temporal distributed on the river valleys, lakesides, ancient rivers and piedmont proluvial fan, showing the form changes of patches, sheets and belts. The growth rate of desertification in the source region was 87.47% from Remote sensing 2000 to 2010. With a high growth rate, the process of desertification was represented by the rapid spread of desertification. From 2010 to 2019, the growth rate of desertification was 37.32%, which was relatively slow. But the moderate desertification land maintained a straight linear growth trend, showing an increasing trend of desertification degree. Through the analysis of the driving factors of desertification in the source region of the Yellow River, this paper argues that the special geographical location, climatic factors, rodent damages and human activities are the main causes of desertification.

INTRODUCTION At present, the research on desertification is relatively weak in the source region of the Yellow River, which has affected Desertification is one of the major ecological and envi- the governance of desertification and the reconstruction of ronmental problems facing China. The source region of the eco-environment in alpine regions. Monitoring and assessment Yellow River is located in the northeast of the Qinghai-Tibet of desertification is an important way to scientifically and ef- Plateau, which is the transition zone from the Qinghai-Tibet fectively prevent desertification. Remote sensing with a wide Plateau to the Loess Plateau. It is an important water con- range of observations, a large amount of information, a fast servation region and ecological barrier of the Yellow River, update of data and high accuracy (Kang & Liu 2014, Ma et al. and also a sensitive area of climate changes. Due to the harsh 2016), has been widely used in the monitoring and assessment natural conditions and fragile ecological environment, and of desertification. Based on RS image processing technology, the impact of global climate changes and human activities, this paper used Landsat TM/ETM+ remote sensing images since the 1980s, many ecological and environmental problems from 2000 to 2019, analysed the spatial and temporal changes have emerged in the source region of the Yellow River, such of desertification in the source region of Yellow River since as desertification, grassland degradation, glacial recession, 2000, explored the driving factors of desertification. Base on permafrost melting, and the flow interruption of the Yellow the analysis of the development trend of desertification, this River. The overall eco-environment in the source region of the paper provides a relevant scientific and theoretical basis for Yellow River is deteriorating, and desertification is the most the restoration of desertification and eco-environment man- serious ecological and environmental problems. A series of agement in the source region of the Yellow River. ecological and environmental problems dominated by land de- sertification, have seriously affected the sustainable economic STUDY AREA development and social stability of the source region and had a certain impact on the middle and lower reaches of the Yellow The source region of the Yellow River generally refers to the River (Cheng 1998, Zeng et al. 2003, Wang et al. 2004). river basin above Duoshixia (Institute of Geography, CAS climate changes. Due to the harsh natural conditions and fragile ecological environment, and the impact of global climate changes and human activities, since the 1980s, many ecological and environmental problems have emerged in the source region of the Yellow River, such as desertification, grassland degradation, glacial recession, permafrost melting, and the flow interruption of the Yellow River. The overall eco-environment in the source region of the Yellow River is deteriorating, and desertification is the most serious ecological and environmental problems. A series of ecological and environmental problems dominated by land desertification, have seriously affected the sustainable economic development and social stability of the source region and had a certain impact on the middle and lower reaches of the Yellow River (Cheng 1998, Zeng et al. 2003, Wang et al. 2004). At present, the research on desertification is relatively weak in the source region of the Yellow River, which has affected the governance of desertification and the reconstruction of eco-environment in alpine regions. Monitoring and assessment of desertification is an important way to scientifically and effectively prevent desertification. Remote sensing with a wide range of observations, a large amount of information, a fast update of data and high accuracy (Kang & Liu 2014, Ma et al. 2016), has been widely used in the monitoring and assessment of desertification. Based on RS image processing technology, this paper used Landsat TM/ETM+ remote sensing images from 2000 to 2019, analysed the spatial and temporal changes of desertification in the source region of Yellow River since 2000, explored the driving factors of desertification. Base on the analysis of the development trend of desertification, this paper provides a relevant scientific and theoretical basis for the restoration of 1436 Q. G. Liu and Y. F. Huang desertification and eco-environment management in the source region of the Yellow River.

Fig. 1: Geographic location of the study area in China. Fig. 1: Geographic location of the study area in China. 1990). To more completely study the desertification in the (Wang et al. 1998), through field investigation and laboratory source region of the Yellow River, our study focused on the analysis, and combined with the changes of vegetation, soil river basin aboveT Tehetu E Township. The study area is located and other factors, the desertification land in the source region between 33°42’~35°20’The source Nregion and of 95°52’~99°29’ the Yellow River generally E, with refers an area to the riverof basin the aboveYellow Duoshixia River (Institute can be of divided Geography into, CAS light 1990). desertification approximately 3.7×104 km2 (Fig. 1). The source region of land (LDL), moderate desertification land (MDL), severe To more completely study the desertification in the source region of the Yellow River, our study focused on the river basin above the Yellow River is bounded by Kariqiong Mountain in the desertification land (SDL) and extremely desertification land Tehetu Township. The study area is located between 33°42'~35°20' N and 95°52'~99°29' E, with an area approximately 3.7×104 west, Bayan Har Mountain2 in the south, Buqing Mountain in (EDL). All types of desertification were mainly distinguished the north and Amnekm (Fig. Machin 1). The Mountainsource region inof thethe Yellow east. RiverIt belongs is bounded byby Kariqiong the degree Mountain of inland the west,degradation. Bayan Har Mountain in the south, Buqing Mountain in the north and Amne Machin Mountain in the east. It belongs to Qinghai Province, includes most parts to Qinghai Province, includes most parts of LDL: the area of quicksand is under 5%, and there is almost and a part of and Maqen County in Golog no wind-sand flow. The vegetation coverage is over 30%, Tibetan , as well as includes a part mainly distributed in fixed coppice sandbags and sporadic of Qumarleb County and Chindu County in Yushu Tibetan grassland. Most of the surface remains in the state of native Autonomous Prefecture. grassland. There is a small amount of wind erosion and wind The source region of the Yellow River is high in the deposition, and the surface appears spot-like quicksand, northwest and low in the southeast, and the elevation of most which is equivalent to fixed sand. areas is 4,100-4,600m. The central area is relatively open, MDL: the area of quicksand is 5-25%, and the wind-sand flow with numerous lakes and marshes, surrounded by icebergs is not obvious. Semi-fixed sand and semi-naked gravel are and snow-capped peaks. The landform shows the character- distributed in patches. The vegetation coverage is 20-30%, istics of inter-distribution of low mountains, wide valleys and there are some sporadic sand dunes. Grassland has been and lake basins. The source region is a typical continental significantly degraded, and the important constructive species alpine climate, characterized by cold and dry weather, the of native vegetation has taken a secondary position, while sharp difference in temperature, much wind and snow, and the sandy vegetation has become the main species. Flaked violent climate changes. The annual mean temperature is quicksand and coppice dune have appeared in large numbers, -3.5°C, annual mean precipitation is 312 mm, and annual which is equivalent to semi-fixed sand. mean evaporation is 1,240-1,327.9 mm. The temperature and precipitation decrease from southeast to northwest, and SDL: the area of quicksand is 25-50%, the wind-sand flow the trend of precipitation increasing with altitude is also and the quicksand texture are obvious, with irregular patch obvious. Alpine cold meadow (ACM) and alpine cold steppe distribution, and the sand dunes are clearly visible. The (ACST) are the main vegetation types in the source region vegetation coverage is 10-20%, and there are coppices in of the Yellow River. the topsoil. The native vegetation no longer exists, sandy grass coppices are dominant species, and the wind erosion and wind landform are obvious. MATERIALS AND METHODS EDL: the area of quicksand is over 50%, and large areas of Desertification land classification: The classification of sand land are distributed continuously. Sand dune, dune ridge desertification land is an objective reflection of the degree and other landforms are obvious. The vegetation coverage is of land degradation. In this paper, based on the existing under 10%. The original surface form has been completely standards and methods for the division of desertification destroyed and replaced by quicksand.

Vol. 19, No. 4, 2020 • Nature Environment and Pollution Technology CHANGES OF DESERTIFICATION IN SOURCE REGION OF YELLOW RIVER 1437

Data sources and processing: In this paper, Landsat TM images. The DDI values of different desertification types images obtained in 2000 and 2010, and Landsat ETM+ were calculated, and the monitoring indicators of different images obtained in 2019 were used to establish databases desertification types were finally determined (Table 1). Based for desertification monitoring. To reduce the influence of on the monitoring indicators given in Table 1, the spatial seasonal aspect and cloud cover on monitoring, remote distribution characteristics of desertification in 2000, 2010 sensing images with cloud cover less than 10% in sum- and 2019 were obtained. Using the change monitoring tool in mer and autumn were selected as far as possible. ATCOR ENVI software, the raster data of desertification distribution atmospheric correction module of PCI image processing during our study period were statistically analysed, the software was used for radiation correction to obtain surface transfer matrix of desertification was obtained, and the reflectance images. The geometric correction was based on temporal changes of desertification were further analysed. the topographic map with a scale of 1:50,000, control points were selected from the topographic map, and the quadratic RESULTS AND ANALYSIS polynomial re-sampling was selected to correct them. The correction accuracy was controlled within 0.5 pixels, and the The spatial changes of desertification:In this paper, the ground resolution was controlled within 30m×30m. Then, remote sensing monitoring results of desertification in 2000, with the support of ARC/INFO software, based on the data of 2010 and 2019 in the source region of the Yellow River soil, vegetation and meteorology in the source region of the were obtained. Based on the monitoring results in 2019, the Yellow River, the human-computer interactive interpretation current situation and spatial distribution characteristics of was used to extract the data. desertification in the source region were analysed. In 2019, Desertificationsurface reflectance images. difference The geometric index correction model: was based In onthis the topographicpaper, the map withthe a scale area of 1:50,000, of desertification control points in the source region has reached surface reflectance images. The geometric correction was based on the topographic2 map with a scale of 1:50,000, control points normalizedwere selected fromdifferential the topographic vegetation map, and the quadraticindex polynomial(NDVI) rereflecting-sampling was select3,519.97kmed to correct them., accountingThe correction for 9.36% of the total area, among vegetationaccuracy was controlledcoveragewere selectedwithin was 0.5 frompixels, adopted the and topographic the groundto indicate resolution map, and wasthe the controlled deserti quadratic within- polynomial 30m×30m.which theThen,re-sampling LDL with the was wassupport selectthe of edlargest, to correct accounting them. The correction for 45.82% of ficationARC/INFO degree,software,accuracy based because on was the controlleddata vegetation of soil, vegetationwithin coverage 0.5 and pixels, meteorology andis thegenerally in theground source resolution regionthe o ftotal the was Yellow areacontrolled River, of desertification, the within human 30m×30m.- theThen, withMDL thefollowed, support of account- computer interactive interpretation was used to extract the data. ing for 26.20%. The area of the SDL was close to that of considered as ARC/INFOa good indicator software, of based desertification. on the data of soil, The vegetation NDVI and meteorology in the source region of the Yellow River, the human- was calculated using reflectance data from infrared and the EDL, accounting for 13.80% and 14.18% respectively. Desertification differencecomputer index interactive model: In interpretation this paper, the normalized was used differential to extract vegetation the data. index (NDVI) reflecting vegetation near-infrared bands of Landsat TM/ETM+ images after ra- According to the China Desertification Census data in 2015, coverage was adopted to indicate the desertification degree, because vegetation coverage is generally considered as a good diation and geometric correction. The surface albedo of the the total area of desertification on the Qinghai-Tibet Plateau indicator of desertification. The NDVI was calculated using reflectance data from infrared and near-infrared bands of Landsat2 study area wasDesertification estimated by difference using Landsat index model TM :data In this inversion paper, the normalizedreached differential 313,274.62 vegetation km index, accounting (NDVI) reflecting for 13.96% vegetation of the total TM / ETM+ images after radiation and geometric correction. The surface albedo of the study area was of estimated the plateau. by using Landsat According to the above data, the area model (1) establishedcoverage wasby Liangadopted (2000).to indicate the desertification degree, because vegetation coverage is generally considered as a good TM data inversion model (1) established by Liang (2000). ratio of desertification in the source region of the Yellow albedo indicator of desertification. The NDVI was calculated using reflectance River is data slightly from … infraredlower(1) thanand near the-infrared average bands level of Landsat of the whole Based on the𝑇𝑇𝑇𝑇 spatial1 characteristics𝑇𝑇𝑇𝑇3 of Albedo𝑇𝑇𝑇𝑇4 -NDVI, a desertification𝑇𝑇𝑇𝑇5 difference𝑇𝑇𝑇𝑇7 …(1) index model in the study area was established. = 0.356𝜌𝜌 TM+ 0 ./130 ETM+𝜌𝜌 images+ 0.373 𝜌𝜌after +radiation0.085𝜌𝜌 and+ geometric0.072𝜌𝜌 −correction.0.0018 TheQinghai-Tibet surface albedo of Plateau. the study area was estimated by using Landsat The model was used to obtain multi-temporal desertification index images. The detailed process was referred to relevant literature Based on the spatial characteristics of Albedo-NDVI, a (Zeng et al. 2006).TM The datadesertification inversion difference model (1)index established model can beby expressed Liang (2000). as: However, the distribution of all types of desertification desertification difference index model in the study area was DDI 1.3437NDVI-albedo in the source region…(2) was relatively concentrated. Except for established. Thealbedo model was used to obtain multi-temporal de- …(1) Monitoring= information extraction: According to the data obtained from two field surveysa insmall 2018 and area 2019 of, combined desertification with to the west of the Eling Lake, Based on the𝑇𝑇𝑇𝑇 spatial1 characteristics𝑇𝑇𝑇𝑇3 of Albedo𝑇𝑇𝑇𝑇4 -NDVI, a desertification𝑇𝑇𝑇𝑇5 difference𝑇𝑇𝑇𝑇7 index model in the study area was established. sertificationthe map data of theindex vegetation= images.0.356 type,𝜌𝜌 soil The type+ 0 anddetailed.130 geology𝜌𝜌 of+process the0.373 study𝜌𝜌 area,was through+referred0.085 the𝜌𝜌 means most+ of0 visual.072 of𝜌𝜌 interpretation, the −rest0.0018 were the typical distributed to the east of the Eling Lake. to samplerelevant areas ofliterature differentThe model desertification (Zeng was used et types toal. obtain were2006). selected multi The- temporaland desertificationdetermined desertification on Landsat ETM+indexFrom images.images the obtain Theperspectiveed detailed in 2019. process With of geomorphicwas referred to relevantunits, literaturedesertification difference index model can be expressed as: the support of image(Zeng processing et al. 2006). software, The the desertification connection between difference the typical index sample model areas wascan and be theconcentrated expressed desertification as: difference between the southern margin of Madoi index images was established to determine the position of the typical sample areas on the desertificationwide valley differen basince index andimages. the northern margin of Heihe River DDI 1.3437NDVI-albedo …(2) …(2) The DDI values of different desertification types were calculated, and the monitoring indicatorswide of different valley desertification basin. It types was in the form of patches, sheet and Mowerenitoring finally determined informationMonitoring =(Table 1). information Based extraction: on the monitoring extracti onAccording indicators: According given into Table thethe data1, the obtained spatialbands, distrib fromdistributedution two characteristics field alongsurveys of the in 201 low8 andmountains 2019, combined and hills with that run datadesertification obtained in 2000,the from map 2010 datatwo and of 2019field the were vegetation surveysobtained. type, Using in soil the2018 type change andand monitoring geology 2019, toolof the innorthwest studyENVI software,area, throughto the southeast, raster the datameans of and of visual distributed interpretation, in the the rivertypical valleys, desertification distribution during our study period were statistically analysed, the transfer matrix of desertification was obtained, combined withsample the areasmap of data different of thedesertification vegetation types type, were selectedsoil andlakesides, determined ancient on Landsat rivers ETM+ and images piedmont obtained proluvium in 2019. With fans, etc. typeand theand temporal geology changes of of desertificationthe study werearea, further through analysed . the means of the support of image processing software, the connection betweenAccording the typical sampleto the areasadministrative and the desertification division, difference the distribution visualET interpretation, N N the typical sample areas of different of desertification in the source region was concentrated in index images was established to determine the position of the typical sample areas on the desertification difference index images. desertificationThe spatial changes of types desertification were: In selected this paper, the and remote determinedsensing monitoring on results Madoiof desertification County. in 2000, The 2010 area and of desertification in Madoi County Landsat2019 in th ETM+e sourceThe region images DDI of thevalues Yellowobtained of Riverdifferent werein 2019. desertificationobtained. With Based ontypesthe the support monitoringwere calculated, resultsaccounted in and 2019, the the monitoring current for 85.07% situation indicators and of that of different in the sourcedesertification region. types All types ofspatial image distribution processingwere characteristics finally software, determined of desertification the (Table connection in the 1). source Based region onbetween the were monitoring analysed the. In indicators 2019,of desertificationthe area given of desertification in Table in1, in the theMadoi spatial distribCountyution were characteristics more than of 78% of typicalsource region sample has reached areas 3,519.97km and the2, desertificationaccounting for 9.36% of differencethe total area, amongindex which the LDL was the largest, accounting desertification in 2000, 2010 and 2019 were obtained. Using thosethe change in the monitoring source region.tool in ENVI In order software, of proportion, the raster data from of large imagesfor 45.82% was of the established total area of desertification, to determine the MDL followed,the position accounting of for 2the6.20%. Theto area small, of the theySDL was were close LDL,to that MDL, SDL and EDL respectively. typicalof the EDL, sample accountingdesertification areas for 13.80%on the distribution and desertification 14.18% respectively.during our Accordingstudydifference period to the wereindex China statistically Desertification The analysedLDL Census and, thedata the transfer in 2015, MDL matrixthe were of de thesertification main ones, was obtained, and the SDL 2 total area of desertificationand the ontemporal the Qinghai changes-Tibet Plateauof desertification reached 313,274.62 were further km , accou analysednting for. 13.96% of the total area of the plateau. According to the above data, the area ratio of desertification in the source region of the Yellow River is slightly lower than the average levelET of the whole N Qinghai N-Tibet Plateau. Nature Environment and Pollution Technology • Vol. 19, No. 4, 2020 However, the distribution of all types of desertification in the source region was relatively concentrated. Except for a small area of desertificationThe to spatial the west changes of the Eling of desertification Lake, most of the: restIn this were paper, distributed the remote to the east sensing of the monitoringEling Lake. From results the of desertification in 2000, 2010 and 2019 in the source region of the Yellow River were obtained. Based on the monitoring results in 2019, the current situation and spatial distribution characteristics of desertification in the source region were analysed. In 2019, the area of desertification in the source region has reached 3,519.97km2, accounting for 9.36% of the total area, among which the LDL was the largest, accounting for 45.82% of the total area of desertification, the MDL followed, accounting for 26.20%. The area of the SDL was close to that of the EDL, accounting for 13.80% and 14.18% respectively. According to the China Desertification Census data in 2015, the total area of desertification on the Qinghai-Tibet Plateau reached 313,274.62 km2, accounting for 13.96% of the total area of the plateau. According to the above data, the area ratio of desertification in the source region of the Yellow River is slightly lower than the average level of the whole Qinghai-Tibet Plateau. However, the distribution of all types of desertification in the source region was relatively concentrated. Except for a small area of desertification to the west of the Eling Lake, most of the rest were distributed to the east of the Eling Lake. From the 1438 Q. G. Liu and Y. F. Huang and the EDL also occupy a large proportion. The proportion depends on which process was dominant. The expansion of of desertification land in Madoi County was much higher desertification indicated its spread and aggravation, while than the average level of Qinghai-Tibet Plateau. The area the reversal of desertification indicated improving in natural of desertification in Maqen County accounted for 11.71% environmental conditions, weakening in human activities, of that in the source region. The remaining three counties, and reducing in the area of desertification in the source Qumarleb County, Chindu County and Darlag County, had a region. To effectively analyse the process of desertification very small area of desertification. Overall, the average degree in the source region, according to the characteristics of the of desertification in the source region was not the highest in dynamic changes of desertification, the desertification in the the Qinghai-Tibet Plateau. However, from the local area, the 2000s was divided into three types: expansion type, reversal degree of desertification and damage in the source region type and stabilization type. The expansion type refers to the was relatively high. region where the area of desertification expanded and degree The dynamic changes of desertification in the 2000s: of desertification increased. The reversal type refers to the The monitoring results of desertification from 2000 to 2010 region where the process of desertification reversed, the area (Table 2 and Table 3) show that the area of desertifica- of desertification reduced and the degree of desertification tion in the source region increased from 1,474.71km2 to weakened. The stabilization type refers to the region where 2,768.61km2, with a growth rate of 87.47% and an annual the desertification was maintaining its initial state. mean growth rate of 21.87%. Among them, the SDL in- The monitoring results of two-time phases in 2000 and creased the fastest, with an annual mean growth rate of 2010 were analysed by GIS spatial superposition, taking 69.52%. The MDL and the LDL were followed, with an annual mean growth rate of 28.62% and 25.32%, respective- 2000 as the benchmark, and this paper concluded that the area of expansion type desertification was 1,938.8km2 from ly. The EDL increased more slowly, with an annual mean 2 growth rate of only 0.71%. It can be seen that the changes 2000 to 2010, of which 1,401.54km was transferred from 2 of desertification in the source region in the 2000s, not only the original non-desertification, and the remaining 537.26km showed the rapid spread of desertification but also showed was from the original desertification aggravated by different that the degree of desertification increased year by year. degrees. The area of expansion type desertification accounted The dynamic analysis of desertification mentioned above for 36.43% of the total area of desertification. The area of 2 only reflected the overall situations of desertification in the reversal type desertification was 319.73km , accounting source region of the Yellow River. In fact, in the process for 21.68%. The area of stabilization type desertification of dynamic changes of desertification, the expansion and was 617.72km2, accounting for 41.89%. In the 2000s, the reversal of desertification were two coexisting processes annual mean expansion rate of desertification was 32.86%, at the same time, and the final result of desertification while the annual mean reversal rate was only 5.42%, and

Table 1: Desertification detecting indicator in the source region of the Yellow River.

Desertification type LDL MDL SDL EDL DDI value 51-63 43-50 34-42 23-33

Table 2: Desertification land in the source region of the Yellow River from 2000 to 2010 (unit: km2). Desertification type 2000 2010 Area Change Change rate % Annual change rate % EDL 417.34 429.11 11.77 2.82 0.70 SDL 95.21 360.00 264.79 278.10 69.52 MDL 295.43 633.61 338.18 114.47 28.62 LDL 666.73 1,341.89 675.16 101.26 25.32 Total 147.71 2,764.61 1,289.90 87.47 21.87

Table 3: Transfer Matrix of desertification land conversion in the source region of the Yellow River from 2000 to 2010 (unit: km2). 2010 2000 Water area EDL SDL MDL LDL Non-desertification Water area 1,411.92 5.92 4.45 4.88 6.88 36.81 EDL 12.02 267.65 65.72 38.65 21.46 11.84 SDL 2.18 23.74 31.09 24.11 11.47 2.62 MDL 6.24 59.00 80.67 91.74 46.65 11.13 LDL 12.97 45.35 107.55 220.96 227.24 52.84 Non-desertification 65.83 27.45 70.52 253.27 1,028.19 33,196.91

Vol. 19, No. 4, 2020 • Nature Environment and Pollution Technology CHANGES OF DESERTIFICATION IN SOURCE REGION OF YELLOW RIVER 1439

Table 4: Desertification land in the source region of the Yellow River from 2010 to 2019 (unit: km2).

Desertification type 2010 2019 Area Change Change rate % Annual change rate % EDL 429.11 499.10 69.99 16.31 1.63 SDL 360.00 486.10 126.10 35.03 3.50 MDL 633.61 922.07 288.46 45.53 4.55 LDL 1,341.89 1,612.70 270.81 20.18 2.02 Total 2,764.61 3,519.97 755.36 37.32 2.73

Table 5: Transfer matrix of desertification land conversion in the source region of the Yellow River from 2010 to 2019 (unit: km2).

2019 2010 Water area EDL SDL MDL LDL Non-desertification Water area 1,401.59 13.24 9.42 16.72 10.72 59.30 EDL 10.97 300.11 65.84 35.92 13.35 2.92 SDL 15.05 92.44 129.01 89.54 32.58 1.38 MDL 16.07 52.62 156.89 261.22 145.26 1.55 LDL 15.53 26.29 106.87 400.22 789.36 3.62 Non-desertification 41.03 14.40 18.07 118.45 621.43 32,498.74 the annual mean expansion rate was six times of the annual in the source region was in the stage of development to mean reversal rate. Therefore, in the 2000s, the process strong development, which was consistent with the overall of desertification in the source region not only shows the situations of desertification development in the whole Qing- rapid spread of desertification but also shows the increasing hai-Tibet Plateau. If the situations should be not controlled, degree of desertification year by year, reflecting the serious the desertification in the source region will expand further. degradation of land and the worsening of eco-environment in the source region during this period. DRIVING FACTORS OF DESERTIFICATION The dynamic changes of desertification in the 2010s: In Table Desertification is a complex process of land degradation. 4 and Table 5, the monitoring results of desertification from Its expansion and reversal are influenced by both natural 2010 to 2019 show that desertification in the source region was conditions and human activities. When natural conditions further expanded in the 2010s. From 2010 to 2019, the desertifi- deteriorate and the intensity of human activities exceeds the cation expanded by 755.36km2, with an annual mean expansion environmental carrying capacity, desertification will inten- rate of 2.73%, which was lower than that in the 2000s. In the sify and expand. On the contrary, when natural conditions 2010s, the changes of desertification were characterized by the improve and human activities are effectively controlled, rapid growth of MDL and SDL. The annual mean expansion desertification can be reversed. Due to the special geo- rate of EDL reached 1.63%, exceeding that in the 2000s. graphical location of the source region, the climate changes, Taking 2010 as the benchmark, the desertification in rodent damages and human activities are the main causes of the 2010s was divided into three types: expansion type, desertification. reversal type and stability type. The area of expansion type desertification was 1,607.69km2, of which 772.37km2 was Climatic factors: The source region of the Yellow River transferred from the original non-desertification, and the re- is located in the hinterland of the Qinghai-Tibet Plateau. maining 835.32km2 was aggravated by different degrees. In Under special geographical conditions, it has formed a the 2010s, the annual mean expansion rate of desertification special climate. Climate changes in the source region are was 5.82%, while the annual mean reversal rate was 1.63%, an important cause of desertification. There are two main and the annual mean expansion rate was about four times of aspects of climate change, one is rising temperatures, and the the annual mean reversal rate. From the above analysis, it other is declining precipitation. According to meteorological shows that although the expansion rate of desertification in data, the annual mean temperature in the source region has the 2010s was lower than that in the 2000s, the desertification been increasing slowly in the past 60 years (Fig. 2), and the in the source region still maintained a trend of continuous temperature increased by 0.382°C per 10a. The variation expansion in the 2010s, with the aggravation of the deserti- trends of annual mean temperature are bounded by 1986. fication as the main factor. In the 2010s, the desertification Before 1986, the temperature decreased by 0.149°C per 10a.

Nature Environment and Pollution Technology • Vol. 19, No. 4, 2020 1440 Q. G. Liu and Y. F. Huang

-1.0

-2.0

-1.0 ) ℃ -3.0 -2.0 )

℃ -4.0 -3.0 Temperature( -5.0 -4.0

Temperature( -6.0 -5.0 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015

-6.0 Fig.1960 2:Fig. The1965 2: change The1970 change 1975of annual of 1980annual mean1985 mean temperature1990 temperature1995 2000from from 19602005 1960 to2010 2019 to 2019..2015

Fig. 2: The change of annual mean temperature from 1960 to 2019. 600

500 600 ) 400 500

) 300 400

200 300 Precipitation(mm 200 100

Precipitation(mm 100 0 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015 0

1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015 Fig. 3: The change of annual mean precipitation from 1960 to 2019. Fig. 3:Fig. The 3: Thechange change of ofannual annual mean mean precipitation precipitation from from 1960 1960 to to2019. 2019. An important consequence of climate change is the impact on the permafrost environment. There is a large area of permafrost An importantSince consequence1986,in the thesource temperature region of climateof the increased Yellow change River. by 0.557°Cis Permafrost the impact per has 10a. an on important themafrost permafrost influence in some on environment.the areas. growth As of a result,alpine There meadow the water is vegetation.a large content area On of plant of permafrost Therefore, the increasing stage of annual mean temperature in roots decreased, swamps and lakes dried up, soil structure and in the source regionthe oneof thehand, Yellow the permafrost River. can Permafrost effectively prevent has ansurface important water and influence soil water from on infiltrating,the growth thereby of alpine increasing meadow the water vegetation. On the source region mainly occurred after 1986. The change of composition changed, and finally, desertification intensified. the one hand, the permafrost can effectively prevent surface water and soil water from infiltrating, thereby increasing the water annual meancontent precipitation of the plant root in the area. source On the region other ishand, also the obvious permafrost has Anotherthe function important of gathering consequence nutrients from of climatethe upper change layers, is the content of (Fig.the plant 3),because and root the lower area. inter-annual soil On temperature the changeother is conducive hand,is over the 300mm.to thepermafrost accumulation The hasimpact of theorganic on function thematter. water Manyof environment. gathering studies have nutrients Accordingshown that from theto themean the survey upper layers, because lowerannual soil mean temperature precipitation is inconducive the source toregion the isaccumulation 312 mm, data, of organic the lake areamatter. decreased Many by studies 0.54% havefrom 1970shown to 1980,that the mean and the temperatureannual mean of theevaporation upper permafrost is over has 1,240 increased mm, by causing 0.2-0.3 °C in the past 60 years due to climate warming, resulting in large- temperature of the upper permafrost has increased by 0.2-0.3°C inwhile the pastthe lake 60 yearsarea decreased due to climate by 9.3% warming, from 1980 resulting to 1990. in large- serious scalewater thawing shortage. of permafrost, Since 2000, and even the the five-year disappearance drought of permafrost The waterin some level areas. of As the a result,lake generally the water content decreased of plant by roots2-3m, and scale thawing of permafrost, and even the disappearance of permafrost in some areas. As a result, the water content of plant roots has causeddecreased, changeable swamps windyand lakes weather dried up, and soil acceleratedstructure and compositionthe the lake changed, shrank and aboutfinally ,20-30m. desertification From intensified. 1990 to 2019, the area decreased, processswamps of and desertification. lakes dried up, soil structure and compositionof swamp changed, and lake and both finally decreased, desertification by about 10%, intensified. while the Another important consequence of climate change is the impact on the water environment. According to the survey data, the An important consequence of climate change is the reduction of river area was the highest, reaching over 22%. Another important consequence of climate change is the impact on the water environment. According2 to the survey data, the impact lakeon thearea permafrostdecreased by 0.54%environment. from 1970 There to 1980, is while a large the lake Thearea decreasedarea of swamp by 9.3% shrank from 1980by nearly to 1990. 200 The km water, and level the ofnumber lake area decreased by 0.54% from 1970 to 1980, while the lake areaof lakes decreased decreased by by 9.3% 49. from 1980 to 1990. The water level of area of permafrostthe lake generally in the decreased source byregion 2-3m, of and the the Yellow lake shrank River. about 20-30m. From 1990 to 2019, the area of swamp and lake both the lake generallyPermafrost decreased has an importantby 2-3m, influence and the lake on the shrank growth about of 20Rodent-30m. damages: From 1990 Rodent to 2019, damages the are area the of main swamp biological and lake both decreased by about 10%, while the reduction of river area was the highest, reaching over 22%. The area of swamp shrank by decreased byalpine about meadow 10%, vegetation. while the On reduction the one hand, of river the permafrost area was thedisasters highest, that reaching destroy theover grassland 22%. The ecology area in of the swamp source shrank by can effectivelynearly 200 prevent km2, and surface the number water of lakes and decreasedsoil water by 49.from region of the Yellow River. The rodent damages in the source nearly 200 km2, and the number of lakes decreased by 49. infiltrating,Rodent thereby damages increasing: Rodent damagesthe water are content the main of biological the plant disasters region that have destroy a thelong gra hisslandstory, ecology but they in the have source been region especially of Rodent damagesroot area.: RodentOn the other damages hand, theare permafrost the main has biological the function disasters serious that since destroy 1985. the The gra mainssland rodents ecology in the in source the source region region of the Yellowof River. gatheringthe The Yellow nutrients rodent River. damages from The rodent the upperin damages the layers, source in the because source region region lower have have a alongare long Myospalax history,history, but butthey baileyi theyhave been andhave especiallyOchotona been especially serious curzoniae since 19serious,85. among since 1985. soil temperature is conducive to the accumulation of organic which Ochotona curzoniae is the most widely distributed The main rodents Thein themain source rodents inregion the source are region Myospalax are Myospalax baileyi baileyi and and Ochotona Ochotona curzoniae curzoniae, amon, gamon whichg Ochotona which curzoniaeOchotona is the curzoniae is the matter. Many studies have shown that the mean temperature and the most harmful. According to statistics, the area of the most widely distributed and the most harmful. According to statistics, the area of the grassland affected by rodent damages in the most widelyof distributedthe upper permafrost and the most has increased harmful. by According 0.2-0.3°C toin statistics,the grassland the area affected of the by grassland rodent damages affected in the by source rodent region damages is in the 4 2 4 2 source regionpast is 60 149.95×10 yearssource due region to4 climateishm 149.95×102, accounting warming,hm , accounting resulti for ng65.20% forin large-scale65.20% of theof the natural natural149.95×10 grassland.grassland.hm The, accounting Theaverage average density for 65.20% ofdensity rodent of holes ofthe rodentnaturalis 3,750- grassholes- is 3,750- 2 thawing of permafrost,2 and even the disappearance2 of per- land. The average density of rodent holes is 3,750-7,050/hm , 7,050/hm2, and the7, 050/hmserious, and area the isserious 19,860/hm area is 192,860/hm. Rodents. Rodents feed feed on on the the roots roots and and stems stems of plants, of plants, and cut offand the cut roots, off causing the roots, large causing large

Vol. 19, No. 4, 2020 • Nature Environment and Pollution Technology CHANGES OF DESERTIFICATION IN SOURCE REGION OF YELLOW RIVER 1441 and the serious area is 19,860/hm2. Rodents feed on the roots minerals, as well as wild animals such as Gymnocypris and stems of plants, and cut off the roots, causing large areas przewalskii, Vulpes corsac and Vulpes vulpes are the main of grassland to wither and die, resulting in degradation and objects for local residents to engage in sideline business. desertification of grassland. More than 50% of the “black soil According to the data of the grassland general station of type” degraded grassland in the source region is caused by Qinghai province, since 1980, sand gold production has rodent damages. According to the measurement, the water started in the area around Daqing Mountain, and thousands content of the surface soil of the secondary bare land on of gold miners from other places have flocked to the area the shady and sunny slopes affected by rodent damages is to collect gold and salt, catch fish and hunt natural enemies 22.18% and 29.27% lower than that of the native grassland of wild rodents. Excessive mining, indiscriminate digging respectively. These rodent holes and “black soil beach” in and illegal hunting have destroyed large areas of grassland the grassland become the breach of wind erosion, creating vegetation, reduced the natural enemies of rodents, damaged conditions for wind erosion, and accelerating degradation the ecosystem, and further led to soil erosion and desertifica- and desertification of grassland. tion. The grassland on both sides of the river has degenerated, Human activities: Human activities are one of the important the function of water conservation has declined, which has factors affecting the ecological environment in the source artificially aggravated the land desertification. region, which are closely related to the changes of desertifi- cation. Especially in the process of economic development, DISCUSSION AND CONCLUSIONS human factors have become the leading factors affecting the Distribution of desertification land: The area of changes of desertification (Chen et al. 2016). Unreasonable desertification land in the source region of the Yellow human activities destroy the surface ecosystem and lead to River accounts for 9.36% of the total area, which is about desertification. 4.59% lower than that in the whole Qinghai-Tibet Plateau. The industrial structure of the source region is dominated by However, the desertification land in the source region of the animal husbandry. Most of the economic income of herdsmen Yellow River is concentrated in Madoi County. The area of depends on animal husbandry, and expanding the number of desertification land in Madoi County accounts for 14.3% of livestock is the main way of economic growth. Since the end the total area, which is higher than that in the whole Qing- of 1960s, the animal husbandry in the source region has de- hai-Tibet Plateau. The proportion is higher in the Huanghe veloped rapidly, the number of livestock has multiplied, and Township and Heihe Township, where the desertification is the grassland has been in the state of overloading, resulting concentrated. Therefore, on the whole, the area of desertifi- in the continuous degradation of the grassland. In the source cation land in the source region is small, but the distribution region, the area of grassland is small in winter and spring, of desertification land is relatively concentrated. In some the grazing time is long, and the overloading is more serious. areas, the proportion of desertification land is high, and the Especially in the beach near the water source, the middle and degree of desertification is also high. lower part of the hillside and the two sides of the river valley, The general situation of desertification expansion: During the overloading of grassland is frequent, which aggravates the 20 years from 2000 to 2019, the area of desertification the load of grassland in winter and spring. According to the land in the source region of the Yellow River increased by investigation of Wang (2001) on the grassland in the source 2,045.26km2. Among them, LDL accounts for 46.25%, MDL region of the Yellow River, the theoretical stocking rate of accounts for 30.64%, SDL accounts for 19.11%, and EDL the local grassland was 667,000 sheep units in winter and accounts for the smallest proportion, only 4%. The results 3,048,900 sheep units in summer. From 2000 to 2019, the show that the desertification in the source region is increasing overloading rate of grassland in summer and winter in the rapidly, among which LDL and MDL are expanding signifi- source region reached 66.98% and 100% respectively. In cantly. Since the 2000s, the process of desertification in the winter and spring, the quantity of forage grass is the low source region has presented a trend of rapid development, quantity and poor quality, and in summer and autumn, the but the development of desertification in different periods amount of forage is many quantities and high quality, which showed different characteristics. In the 2000s, the growth rate leads to the vicious cycle of livestock being fat in autumn, of desertification was high, and the process of desertification thin in winter and death in spring. was characterized by the rapid spread of desertification land. Another reason for the destruction of natural resources In the 2010s, the growth rate of desertification slowed down and the ecological environment by human activities is the relatively, but MDL maintained a linear growth trend. In the improper use of water and soil resources, excessive mining, past 20 years, although there is a certain reversal of deser- and indiscriminate digging. The source region of the Yel- tification in some areas, on the whole, the source region is low River is rich in natural resources. Gold, salt and other dominated by the expansion of desertification.

Nature Environment and Pollution Technology • Vol. 19, No. 4, 2020 1442 Q. G. Liu and Y. F. Huang

The results of driving force analysis of desertification:In Cheng, G. 1998. Some understandings about the eco-environmental the past 20 years, the desertification in the source region was protection and buildings in the source region of and Yellow attributed to the unreasonable exploitation and utilization of rivers. Advance in Earth Sciences, 13(suppl.): 1-5. Institute of Geography, CAS. 1990. The Atlas of Qinghai-Tibetan Pla- grassland resources under the background of the warming teau. Science Press, pp. 77-79. and drying trend of the alpine ecological environment, which Kang, W. and Liu, S. 2014. A review of remote sensing monitoring and further exacerbated the process of grassland degradation and quantitative assessment of aeolian desertification. Journal of Desert land desertification. Due to the combined action of natural Research, 34(5): 1222-1229. Liang, S. 2000. Narrowband to broadband conversions of land surface and human factors, many lakes and wetlands in the source albedo I: Algorithms. Remote Sensing of Environment, 76: 213-238. region have shrunk or even dried up, causing a series of eco- Ma, Y., Sha, Z., Chen, X. and Fu, G. 2016. Desertificated land changes logical environment problems such as grassland degradation, in Gonghe basin from 1990 to 2010. Journal of Arid Land Resources land desertification and soil erosion. and Environment, 30(2): 176-181. Wang, G. 2001. Eco-environmental degradation and causal analysis in the source region of the Yellow River. Environmental Geology, ACKNOWLEDGEMENT 40(7): 884-890. Wang, G., Ding, Y., Wang, J. and Liu, S. 2004. Land ecological changes This research was financially supported by the Project of and evolutional patterns in the source regions of the Yangtze and Anhui Education Department (No. SK2018A0603). The Yellow rivers in recent 15 years. Acta Geographica Sinica, 59(2): work was facilitated by the Qinghai Department of Lands, 163-173. Environment and Resources and the Project of Scientific Wang, T., Wu, W. and Wang, X. 1998. Remote sensing monitoring and assessing sandy desertification: An example from the sandy deserti- Research and Development Foundation of Hefei University fication region of northern China. Quaternary Sciences, 2: 108-118. (No. 20RW06ZDA). Zeng, Y., Feng, Z. and Cao, G. 2003. Land-cover change and its impacts on environment in the upper reach of the Yellow River, northeast REFERENCES Qinghai-. Mountain Research and Development, 23(4): 353-361. Chen, L., Ding, W., Geng, Y. and Zhao, C. 2016. Dynamic change trend of Zeng, Y., Xiang, N. and Feng, Z. 2006. Albedo-NDVI space and remote desertification in during 1975-2015. Desert and Oasis sensing synthesis index models for desertification detection. Scientia Meteorology, 10(5): 64-71. Geographica Sinica, 26(1): 75-81.

Vol. 19, No. 4, 2020 • Nature Environment and Pollution Technology