Human Activity Intensity And Ecological Effect Of Coastal Wetlands In The Yellow River Delta

The Yellow River Delta coastal wetland has high ecological service value,owing to its rich resources,such as oil,salt,aquaculture and so on.However it is highly susceptible to human activities because of its special geographical location.Nowadays,frequent human activities,coupled with intense reclamation activities,poses a threat to landscape pattern and ecological environment of coastal wetlands.However,little is known about the effect from natural and anthropogenic causes on the Yellow River Delta coastal wetland.Therefore,the human activity intensity index system was constructed based on the data from 1989 to 2017,using Arc GIS spatial analysis technology combined with field investigation.Meanwhile,the vegetation and soil conditions in the study area were investigated and analyzed.The results are as follows:(1)From 1989 to 2017,the natural wetland area decreased from 96%to 62%,while the artificial ones increased by 15.95%,thus the total wetland area decreased with an average annual rate of 37.06 km~2.By 2017,the coastal wetland in the Yellow River Delta was still dominated by natural wetlands,accounting for 62.11%of the total wetland area.Natural wetland landscape type was mainly composed of vegetation,which accounts for 56.75%of natural wetland,while breeding pool was the main artificial wetland landscape type,accounting for 60.8%of the whole artificial wetland.(2)It is obvious that natural wetland was transformed into constructed wetland and non-wetland landscape type.From 1989 to 1999,in the natural wetland,mudflat and vegetation were transformed into Salina land(artificial wetland)and cultivated land(non-wetland landscape type),with change area of 16.4km~2 and 442.4km~2respectively.Among them,the mudflat and vegetation in the natural wetland were transformed into salt field in the cultivated land and constructed wetland in the non-wetland landscape types from 1989 to 1999,and the conversion area reached16.4km~2 and 442.4km~2 respectively;subsequently,from 1999 to 2009,68.24 km~2 of mudflat was transformed into the breeding pool.What's more,the bare land,water area and vegetation were transformed into cultivated land by 62.19 km~2,10.2 km~2 and 530.4km~2 respectively.In addition,from 2009 to 2017,the change area from vegetation to cultivated land reached 241.13 km~2.(3)The intensity of human activities in the coastal wetlands of the Yellow River Delta increas with increasing distance from the coastline and is enhanced year by year.(4)In terms of the distribution of natural vegetation in the study area,the biodiversity of the inland area without interference from human activities was higher than the estuary area and the vegetation types are mostly herbs with short flowering period,dwarf phenotype,and poor adaptability to environment.The vegetation in the estuary area,however,was dominated by plants with salt tolerance and wind resistance(Phragmites australis,Suaeda salsa).(5)The growth of vegetation is closely related to the nutrients in the soil and the various nutrient elements from the same source in the soil can interact with each other.Our results showed that the growth of vegetation in the study area was significantly positively correlated with available potassium and organic matter in the soil(p<0.05)and negatively correlated with available phosphorus and TN(p<0.01).Under the long-term scale,the change of coastal wetland landscape type was affected by the combined influence of natural processes and anthropogenic activities and the latter promoted the evolution of coastal wetland landscape.Our results showed that the relationship between anthropogenic activities and soil factors and the growth of vegetation has not reached a significant level in the short term.