| Unreasonable development and utilization of the surface of earth leads to ecological and environmental problems such as soil erosion.As the core area of the Three Rivers Parallel World Natural Heritage Site,Nujiang Prefecture is a typical alpine valley area and is an important area for global biodiversity and the protection of ecological landscape.The transformation of land use patterns and the irrational use have caused serious ecological and environmental problems such as soil erosion in Nujiang Prefecture.In accordance with the conviction that lucid waters and lush mountains are invaluable assets.The ecological security of Nujiang Prefecture cannot be ignored.This paper focus on the transformation of land use,to quantify the temporal and spatial changes of landscape pattern security and the service value of ecosystem by dividing area into 2km'2km grid as one research unit.In this paper,the land use dynamics and land use transfer matrix are selected for the analysis of the land use status of Nujiang Prefecture in these three selected research years which is 1996,2006 and 2017.To analyze the temporal and spatial changes of landscape pattern safety(LSES)by calculating landscape fragmentation(PF),landscape vulnerability(?)and landscape marginal density(ED)in the three research years of Nujiang Prefecture.And to evaluate quantitively the value of ecosystem services of these three selected research years of Nujiang Prefecture by four indicators involving supply service(ES_pro),regulation service(ES—reg),cultural service(ES_cul),and support service(ES_sup).Finally,to analyze the correlation between land use and landscape pattern security,the level of use of land and ecosystem service value,landscape pattern security and ecosystem service value by Moran'I and Pearson correlation coefficient.The main conclusions are as follows:(1)Temporal and spatial evolution characteristics of land use:The land use pattern of Nujiang Prefecture is mainly forest land.The forest land in the three research years of 1996,2006 and 2017 accounted for more than 70%,and decreased in 2017 compared with 1996;Coverage of snow accounted for 9.91%in 1996 which is mainly distributed in the border areas of Gongshan County and Lanping County and Fugong County and decreased 5.42%of the whole state in 2017.Cultivated land accounted for 8.76%which decreased to 8.35%in 2017,grassland area accounted for 7.89%in 1996 which increased to 10.23%in 2017.The water area and construction land area accounted for less than 1%which is mainly distributed along the Nujiang River.The construction land increased gradually and the water area decreased in these three years.For dynamics,the largest change from 1996 to 2017 was construction land,which increased and transformed mainly from forest land and cultivated land.(2)Landscape pattern safety(LSES):In 2017,the landscape pattern safety index was relatively low at 0.64.The unsafe areas of Fugong County and Lishui City were mainly distributed along the Nujiang River in Lanping County,and Gongshan County takes a less relatively proportion;in 1996 and 2006,the most safe for LSES was Gongshan County.In 2007,the most safe one was Fugong County,and the safety values of all four counties and cities reduced.The area with higher fragmentation was mainly distributed along the Nujiang River and most of the areas in Lanping County.The area with more obvious fragility is the border of the Nujiang River and most of the areas in Lanping County.The areas with high density of landscape edge are mainly concentrated along the Nujiang River,the middle part of the Nujiang River,the Dulong River,the Lancang River and the Guadeng River.The highest value of LSES in 2017 is 0.83,and the value of ED,PF and V is the lowest in three years,which indicates that the grassland landscape fragmentation,fragility and marginal density are the lowest in Nujiang Prefecture and the ecological security pattern of grassland landscape is the safest followed by cultivated land.For the value of LSES the forest land is relatively the lowest,of which the ED value is relatively the highest,indicating that the edge density of the forest landscape is greater and the safety value of landscape pattern lower though the forest area is the most extensive in Nujiang.(3)Ecosystem Service Value(ESV):The value of ecosystem services in Nujiang Prefecture maintains an upward trend.In 2017,the value of the ecosystem is the highest,which is 5026.59x 103 yuan,of which the value of forest land is the highest followed by grassland,and the value of cultivated land is the lowest.The lower-value areas are mainly concentrated in the middle area of Dulong River and Nujiang in Gongshan County and the junction of Lanping County and Fugong County which are mainly snow-covered,followed by Lancang County and Guadeng River areas.It is mainly distributed along the Nu River for Gong County and Lishui City.When the land use degree is less than 2,the value of ecosystem services is on the rise.When the land use degree is greater than 2,the value of ecosystem services decreases.The area of land whose the use degree is greater than 2 in Nujiang is mainly concentrated along the Nujiang River and in most of Lanping County where are also the main developing areas of Nujiang Prefecture socially and economically and human activities are frequent and the degree of land development and utilization is great.The rational development and utilization of land shall be adjusted to ensure the maximum value of ecosystem services.(4)There is a certain correlation between landscape pattern safety and ecosystem service value,and the correlation between the two is positive.The correlation coefficient in 2017 is the maximum which is 0.266,indicating that the ecosystem service value increases with the increasing of landscape pattern security.It indicates that the landscape pattern safety and the value of ecosystem service in Nujiang Prefecture keeps a same pace.The most relevant correlation among the landscape pattern safety changes is the edge density of the landscape.(5)The correlation between landscape margin density and landscape pattern safety is the greatest which indicates that the decline of landscape pattern safety is the relative distinctly with the increase of ED value,and there is a distinctly positive correlation between ecosystem service value and four value indicators have been mentioned.There is a certain correlation between the three landscape pattern indices and the four ecological service value indices.The most relevant correlation is the landscape margin density of 2006 and the four service value indicators,all of which are negatively moderately correlated which indicates the value of support,culture,regulation,and supply services decreases with the increasing of edge density.From the above conclusions,we can more clearly understand the changes temporally and spatially in land use change,landscape pattern security and ecosystem service value in Nujiang Prefecture,and the correlation between various indicators,which can be used for the supervision of the land use of Nujiang Prefecture and provides a reference for ecological environmental management of Nujiang Prefecture. |
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