The Evaluation Of Fitness And Utilization Potention Of Dikepond Based On The Theory Of Niche In Nanhai District

The dike-pond is a unique land use pattern which widely distributed in the Pearl River Delta.Since the 1990 s,With the development of urbanization and industrial,the problems such as the shrinking of dike-pond area and deteriorating of ecological environment have become increasingly prominent.Since the 17 th National Congress of the Communist Party of China,the development of ecological civilization has been continuously promoted.The dike-pond as a typical eco-friendly agriculture is of great significance to maintain regional ecological balance.Exploring and analyzing its use and changes,which is beneficial to develop and protect the dike-pond.Nanhai District,in the core of Pearl River Delta,also face a sharp drop of dike-pond,functional degradation and other issues.Therefore,this paper analyzes the spatial and temporal evolution of the dike-pond from 2006 to 2013,based on the niche theory,it evaluates the niche fitness and evolutionary momentum.Based on overlay analysis,the corresponding strategies are put forward.Based on the current land use map which interpreted from LandsatTM image of Nanhai District in 2006 and 2013,this paper analyzes the temporal and spatial evolution of dike-pond in Nanhai district in 2006 and 2013 by using GIS and mathematical analysis method.The index system was established from three dimensions: natural quality,social economy and spatial form.The temporal and spatial changes were analyzed under grid unit.By Overlay analysis to obtain suitability-potential zoning.The conclusions of this paper are as follows:(1)The land of dike-pond is mainly distributed in the southern typical dike-pond region.In 2006,2013,the area of dike-pond is 22255.78hm2,17598.43hm2,decreased 4657.35hm2,and mainly concentrated in the northern part of the study area.The dynamic change of the pond is mainly from the land for construction and the cultivated land.The dynamic change degree of the pond is significantly higher than that of the southern typical dike-pond region.The center of gravity of the dike-pond is mainly migrating southward,the migration distance of each town of northern is obviously larger than the typical dike-pond region;(2)From the natural quality of the pond,97.00% of the dike-pond land is located in the <10m elevation,and <2°slope range;surface texture,soil PH,soil organic conditions are better,more than 90.00% score>80;Profile configuration is relatively poor,more than 30.00% score <70;(3)From the spatial form,the spatial form of the dike-pond in Nanhai district is better,and the southern typical dike-pond is better than the northern.Specifically,the dike-pond is mainly high dike-pond area ratio,and the proportion of low dike-pond area ratio is decreased.The proportion of the dike-pond of high fractal dimension index area is less than 1.00%,the low fractal dimension dike-pond is improved and the overall condition is improved.The proportion of the low fragmentation index of the dike-pond are increased from 42.46% to 49.90%,the fragmentation degree is lower,but the overall fragmentation is still high,nearly 50.00% of the dike-pond is medium degree of fragmentation;The proportion of the high integrate index connectivity of the dike-pond is increased from 47.55% to 54.99%,the overall contiguous increased.(4)From the social and economic,the use grade of dike-pond concentrated in 4-8 grade,more than 50.00% of the dike-pond belongs to 6 grade;the dike-pond is mainly distributed in the range of the distance from the traffic trunk line(0-600m),from the rural settlements(0-500m),from the river(0-1500m),and within the scope of the largest reduction of dike-pond;In addition,the main distribution of the dike-pond in the range from the urban built area(0-3000m),in this range,the proportion of dike-pond increased the most.(5)The niche fitness the dike-pond in 2006 and 2013 are Presented Southern high north low differentiation rule.The niche suitability of natural quality dimension is mainly higher niche suitability,and the area of dike-pond is 8116.22hm2 and 7130.09hm2,accounting for 36.47% and 40.53% respectively.The proportion of low niche suitability is only 4.09%,8.96%.During the study period,the high suitability of the dike-pond is reduced and the low suitability is increasing.The socio-economic dimension is mainly medium niche suitability,the area is 7450.07hm2,6373.32hm2,accounting for 33.48% and 36.22%,and the proportion of high and low niche suitability is greatly reduced.The spatial form dimension is mainly niche suitability,the area is 10351.15hm2,9494.36 hm2,accounting for 46.52% and 53.96%,the lowest niche suitability is 15.21% and 12.80%,The niche suitability of dike-pond is mainly the high niche suitability,the area is 10739.81hm2 and 9494.36hm2,accounting for 48.27% and 54.63%,the low niche suitability is Accounting for,only 9.02% and 7.99%,the overall suitability increased(6)The change of fitness is mainly the grade unchanged,followed by the grade increase and the grade dropping,the area is 12721.91hm2,5569.69hm2 and 5087.05hm2,respectively.typical dike-pond region accounting for 68.25%,75.83%,47.28%,that is,the southern dike-pond region is steadily increasing,while the pond in the northern region is mainly reduced.The analysis of the change situation,the southern dike-pond region is mainly the dropping of high degree of fitness,the northern region is mainly the decline of low degree of fitness of,that is,the reason of the grade dropping in typical dike-pond region is the dike-pond degradation,while the northern region is due to loss of dike-pond.The grade increase is mainly raised to the high suitability level,and mainly concentrated in the southern typical dike-pond region.Through the analysis of the specific reasons for the increase in grade,it is found that 20.16% of the increase in the level of the dike-pond is caused by the development of the dike-pond and this way is increased to the low degree of suitability.There are 79.84% through the finishing and transformation to achieve the degree of increase,and mainly to the high degree of fitness degree upgrade.Therefore,the pond self-finishing development is the most effective way to improve the level of suitability.(7)The potential of the dike-pond in the Nanhai district is mainly the low potential,the northern potential is higher than the southern.the center of gravity of potential of the dike-pond is migrated to south,and the overall potential has been improved.The potential of the southern typical dike-pond is relatively stable.Through the overlay analysis,it can be found that the dike-pond is dominated by high niche fitness and low potential.Based on this,the niche expansion and characteristic niche strategy are proposed for the southern dike-pond.The middle should implement the ecological dislocation separation and coordinated development strategy.The north should implement the niche separation and specialization,expansion and collaborative development strategy.