Spatio-Temporal Variation of Grassland in Western Songnen Plain
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This paper analyzed temporal and spatial variation of various vegetation fractions and inner configuration of the grassland in western Songnen Plain where ecological environment was fragile based on the remote sensing data and classification of grassland resource with the support of GIS technology.It educes the quantities and characteristics of transformation among higher-coverage grassland,mid-coverage grassland,and lower-coverage grassland and other land use types from 1989 to 2001.The results indicate that the areas of three kinds of grassland are decreasing during 12 years.The transformation proportions to glebe are 77.78%,70.13% and 36.57% respectively,which illuminate that the main reason for the decrease of grassland is human's durative exploitation of grassland.The transformation proportion from grassland to saline-alkalized land increases with the decrease of grassland's vegetation fraction and is 0%,4.62%,and 32.81% for higher-coverage grassland,mid-coverage grassland and lower-coverage grassland,respectively.It shows that a crucial factor for saline-alkalized grassland is vegetation fraction.From the dynamic changing of grassland's inner configuration,we conclude that degenerative characteristic of grassland is from higher-coverage to mid-coverage and from mid-coverage to lower-coverage;moreover,the evolution is almost non-reversible under the current human activities.The degraded grassland is mostly located at the north of Zhenlai County,the south of Taonan City,the north of Tongyu County and the west of Qian'an County.Analysis of saline-alkalized grassland show that the most important reason causing saline-alkalized grassland is the continuous impact of human activities,and the status of mid-coverage grassland is the key affecting holistic quantity of grassland and the outspread speed of saline-alkalized grassland.Therefore,the only way for socio-economic and ecological environmental sustainable development is to utilize grassland resource soundly and restore the saline-alkalized grassland synthetically.At the end,the authors put forward the measures of ecological environmental restoration and grassland's sustainable development based on rational utilization of existing grassland resource and integrative prevention and rehabilitation of saline-alkalized grassland in research area.Cite
On the basis of vegetation coverage monitor and indicator evaluation systems,using GIS software and pixel dichotomy model based on vegetation indices,this study reflected the grassland coverage images in 2000,2005 and 2009 and analyzed the dynamic changes of grassland vegetation coverage in different periods at Yanchi County.The results showed that from 2000 to 2005,the areas of high,medium-high and medium coverage grassland at Yanchi County increased by 4.83,907.03 and 714.67 km2,respectively.Meanwhile,the areas of low and extremely low coverage grassland decreased by 717.83 and 908.62 km2.From 2005 to 2009 the areas of high,medium-high and medium coverage grassland continuously increased by 228.47,190.00 and 377.04 km2,respectively.Above analysis showed that the implementation of national ecological construction projects,such as Restoration Project,Natural Grassland Grazing Prohibition and Natural Grassland Rodent-free Demonstration Area,in 2000 have brought remarkable effects.The trend of grassland desertification has been controlled for the time being.
Desertification
Grassland ecosystem
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Monitoring changes of grassland resources and grasping their changing trend can be very helpful to the effective protection of grassland resources and grassland environment.However,regular monitoring over long time span is not easy to realize.In this paper,with the aid of the GIS technology and remote sensing data,the changes of grassland resources in three representative regions of Western China,Xinjiang,Tibet and Qinghai,were monitored with the 5year intervals from 1995 to 2010.Results indicate that:1)Grassland degradation is the main cause of loss of grassland resources.The main directions for the transfer out of grassland resources are bare rock gravel,Gobi and sand,etc.To control the loss of grassland resources,we must first stop the degradation of grassland resources.2)The protection of grassland resources with low coverage should be paid more attention.Compared with the high coverage grassland,the losses of the grassland with low coverage are generally more serious.3)The change of grassland resources in Xinjiang should be paid serious attention.Xinjiang is facing a serious loss of grassland resources.The lost area of grassland resources in Xinjiang came up to 8×106 hm2,and the loss of the last 5years took up 72% of the total area.While the grassland resources of Qinghai and Tibet became stable during the research period.
Grassland Degradation
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Variation of grassland area in the Duolun County of Xilin Gol League was presented by combining field survey and remote sensing technology and its causes were discussed in this study.The results of this study showed that grassland area in Duolun County was fluctuant from 1971 to 2007,indicating that the grassland area decreased from 227 640.93 ha in 1980 s to 166 929.43 ha in 1990 s,and restored to grassland area of the 1980 s in 2000 due to conversion of cropland to forest and grassland.Under the climate warming and drying,human disturbance was key factor affecting the grassland area.Plenty of grasslands were reclaimed into croplands and were substituted by the lakes and marshes in 1990 s when the climate was warm and humid,resulting in the decrease of grassland areas.In 1980 s,grassland degenerated and deserted because of overgrazing.Although the rainfall decreased,the grassland had been gradually restored because of better management from 2000 to 2007.
Overgrazing
Inner mongolia
Grassland Degradation
Grassland ecosystem
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Grassland had heavily degraded in Songnen Plain,and it is important to maintain balance of ecosystem by studying on spatial-temporal dynamics and change of landscape pattern of grassland.Based on RS and GIS technique,three-period(1986,1995,2000) remote sensing images were interpreted to extract spatial information of grassland landscape in the region,and spatial-temporal dynamics of grassland and change of landscape pattern were analyzed.The results showed that grassland area decreased by 25.6%,grassland degradation is serious.Patch number of grassland decreased by 18.38%,and degree of fragmentation is enhanced,patch shape changed little.During 1986~1995,low coverage grassland rapidly developed,and high coverage grassland fast declined during 1995~2000,and it actively contributes to decrease of grassland.Grassland is mainly converted into cropland and saline-alkalized land,conversion area reaches 1116219.53hm~2 and 313708.75hm~2,respectively.From 1986 to 2000,centroids of various grasslands moved towards northeast direction,and in different stages,centroids change of each kind of grassland are irregular and multi-directional.Both natural factors and human activities result in grassland degradation in the studying region,natural factors are basic condition of grassland degradation,and human activities are crucial factors.
Grassland Degradation
Grassland ecosystem
Fragmentation
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Grassland distribution and change dynamics are main objects of desertification monitoring.By using four-period remote sensing images(1976,1996,2001,2006) and under the support of RS and GIS techniques,the spatial information of grassland during the past 30 years in Guinan County,Qinghai Province is interpreted and extracted,and the area,quality and spatial change pattern of grassland are analyzed in this paper.The results shows that: ①The grassland area was decreased by 12.62% in the past 30 years,and grassland degradation is serious,especially for high coverage grassland with a net decreasing rate of 28.87%;During 1976-1996,grassland is mainly converted into cropland,wilderness and forest land,and the converted area of the high coverage grassland occupied 85.9% of total converted area.During 1996-2006,the trend of grassland degradation is slow.②The grassland had greatly degraded from 1976 to 1996,the main reason was that 16.6% of high coverage grassland were converted into middle and low coverage grassland.In the period of 1996-2006,the change of the grassland dynamic degree was small and the area of different coverage grade grassland nearly kept stable.③The change of gravity center of grasslands is irregular and multi-directional because both natural factor and human actions take effect on grassland in the region.
Grassland Degradation
Desertification
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Grassland is a main land type in the study area,the status and trends of its degradation become a major issue of the ecological construction in China,and have been raised to the level of the needs for national ecological economic strategy.Many studies showed that grassland ecosystem degradation is,in the succession process of the climate-land cover-human activities,an indication of out of balance.Grassland degradation will lead to a series of environmental problems such as lower grassland production,land desertification,loss of biodiversity,soil degradation,loss of carbon sinks.Study areas located in the south of the head of Yangtze river.The total area is about 34 069.31km2,mainly covered by grassland(71.49%) and swamp(10.11%).The low and moderate covered grassland is 71.16% of the total grassland area.The increasing destruction of the land in this area have been kept increasing the risk of environmental degradation.Based on the TM/ETM in 1977,1990 and 2004,geographical map(1∶100 000),grassland map(1∶1000 000),and field data,the authors extract grassland degradation distribution characteristics.The Arcgis 9.1 software was used to convert data types and do the overlay.reclassification,and zonal statistic analysis.Results show that grassland degradation is the most important land cover change in the study area,which occupied 11.84% of the whole region in the former phase and 21.54% in the later phase.The areas of degraded grassland are more in the later phase than in the former phase.Grassland in the former phase became better in some regions because of the climate and glacier ablation.The degraded grassland mainly occurs in the low altitude with relatively higher population density.
Grassland Degradation
Desertification
Land Cover
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By using three-period(1986,2000,2009) remote sensing images,with the support of RS and GIS,spatial information of grassland landscape in Taipusi from 1986 to 2009 is extracted,spatio-temporal dynamics of grassland and change of grassland landscape patterns are analyzed.The results showed that from 1986 to 2000,the areas of grassland decreased about 307.67 km2 and degraded seriously.Many grasslands are converted into cropland.The ecological environment has became deterioration.From 2000 to 2009,grassland areas have increased,the parts of the increase areas are mainly from cropland.In the past twenty years,the low salt meadow continued to increase,and the low land meadow decreased rapidly.Based on the analysis above,human activities and natural factors are the main factors that resulted in the degradation of the grassland.Natural factor takes some driving acting,but human actions are the dominating driving power.
Ecotone
Grassland Degradation
Animal Husbandry
Inner mongolia
Driving factors
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Grassland had heavily degraded in west Jilin province during 1980-2000,and it is of great importance to the sustainable development of stockbreeding and eco-environment through study ing on spatio-temporal dynamic change of grassland in this region.By using three-period(1980,1995,2000)remote sensing images and with the support of RS and GIS,spatial information of grassland landscape in west Jilin province in the past 20 years is interpreted and extracted,dynamic spatio-temporal change of grassland landscape patterns of Jilin province is analyzed.The results show:(1)In the past 20 years,40.70% of the grassland decreased,and grassland degradation is serious,especially for high coverage grassland with a net decreasing rate of 51.96%.(2)From 1980 to 1995,the total dynamic degree of grassland is accordant with the dynamic degree of high coverage grassland,so high coverage grassland has a strong effect on change of the whole grassland.During 1995-2000,both dynamic degree of various grasslands and total dynamic degree are negative,the speed of low coverage grassland degradation is the fastest,the total dynamic degree approximates the dynamic degree of high coverage grassland and moderate coverage grassland,and the two types of grasslands heavily affect change of the whole grassland.(3)Grassland is mainly converted into cropland and saline-alkalized land,the converted area reaches 475 799.43hm2 and 303 182.06hm2 respectively.(4)In the last 20 years,the center of gravity of all kinds of grasslands moved towards northeast direction,and in different phases,the change of center of gravity of each kind of grassland is irregular and multi-directional.As far as grassland degradation in the study area is concerned,natural factor takes certain driving action,but human actions are the dominating driving power.
Grassland Degradation
Degree (music)
Grassland ecosystem
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This paper is to analyze the changes of landscape pattern in Shanghaimiao in the last 5 years,by using the 2002 and 2006 ETM/SPOT remote sensing data and combining with field investigation.The results show that: ① The structure of landuse had changed greatly in Shang haimiao : the area of woodland,high coveraged grassland,low coveraged grassland was decreased;the area of middle coveraged grassland,desert land and urban land was increased,most of the woodland revert to high covered grassland and middle covered grassland;and high covered grassland reverted to middle covered grassland and woodland,this indicated that Shanghaimiao has the two trends include woodland revert to grassland and high coverage grassland revert to low coveraged grassland.② The complexity and fragmentation degree of the patch shape of theShang haimiao in 2006 is higher than in 2002,this will lead land more desertification.
Desertification
Fragmentation
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Grassland is an important ecosystem; the spatiotemporal evolution trend of grassland and its impacts on climatic factors play an irreplaceable role in maintaining regional sustainable development and ecological balance. In this paper, based on the remote sensing images of 1990, 2000, 2010, 2020, and 3S technology, we use the methods of dynamic rate and transfer matrix to analyze the spatiotemporal evolution trend of the northern Songnen Plain (China). The method of grey correlation is used to analyze the impact of climate factors on it. The results showed that the grassland changed dramatically and unevenly across the three periods of 1990–2000, 2000–2010, and 2010–2020, with the biggest change in the last period. The internal conversion of grassland mainly occurred between H-grassland (high coverage grassland) and M-grassland (medium coverage grassland), while the transformation rarely occurred in L-grassland (low coverage grassland) due to its small area. There has been a transfer-in from cultivated land, woodland, and unused land to H-grassland and M-grassland. The grassland transfer-out was mainly from H-grassland and M-grassland to cultivated land and unused land. What’s more, the transformation mainly occurred in Daqing City, Suihua City, Qiqihar city, as well as occurring in the west of Harbin and the southwest of Heihe city. Climate change has exacerbated the reduction of grassland areas. In summary, the spatiotemporal change rates of grassland area in the north of Songnen Plain initially showed a mild decrease and were then followed by a rapid decrease. Climate factors were of great significance to the spatiotemporal changes of grassland, and precipitation had a greater impact on the reduction of grassland. The results can provide meaningful information for grassland change, grassland protection, and management in the northern Songnen Plain.
Grassland ecosystem
Grassland Degradation
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