Habitat Suitability Assessment Of Reintroduced Populations Of Crested Ibis In Shaanxi

The threats to wildlife in the world is becoming more and more serious,and habitat research and conservation has attracted much more attention.Therefore,the evaluation of habitat suitability for endangered species is of great significance to wildlife protection.The Crested Ibis(Nipponia Nippon),our focal species,is one of the global endangered species,which is listed as a first-grade key protected species in China,the endangered(EN)species in Red Data Book of International Union for Conservation of Nature(IUCN),and a species in Appendix ? of CITES.The rare bird,endemic to East Asia,was once at the brink of extinction in the last century.Since the rediscovery in Yangxian County in 1981,in-situ and ex-situ conservation efforts during nearly four decades have increased the wild population from 7 to more than 3,000 individuals,and up to date,the caged and reintroduced populations are also distributed in China,Japan and South Korea.At present,Shaanxi is the only range of wild population of the Crested Ibis,as well as the region with the largest population.Since the first release in Ningshan County in 2007,further reintroductions have been subsequently carried out in Yaozhou District,Tongchuan City and Qianyang County,Baoji City.Whether the wild or the reintroduced population,the study and protection of their habitat are beneficial to the persistence or establishment of the population.However,except for wild population,few studies have involved in the habitat assessment of the reintroduced populations,especially the comparative study of habitat suitability under heterogeneous landscape conditions.In the present study,with the release sites in Shaanxi province as the study area,we give an evaluation of the habitat suitability using maximum entropy model(MaxEnt model)and 3S techniques.Through investigating,visiting of the field and the record of relevant literature from 2018 to 2019,the data of its geographical distribution point are collected.After extracting the environmental variables from remote sensing images,digital elevation model(DEM)and vectorized maps,through the interpretation and pre-selection examination of ArcGIS10.2 and MaxEnt3.4.1 software,seven environmental factors,such as altitude,slope direction,distance to the road,distance to the water,distance to the residential area annual average temperature,mean annual precipitation and habitat suitability index,are selected as environmental variables for habitat suitability assessment of Nipponia Nippon.Being processed by Maxent model,all the data are used to evaluate and analyze the habitat suitability of the reintroduced population of Nipponia Nippon in Shaanxi Province After the examination of ROC curve,the results of the model have high reliability and then generate the habitat suitability evaluation map of it.The major findings are as follows:1.The ROC curves generated by the MaxEnt in the model analysis of Ningshan County indicate the high reliability of the model evaluation results.The main environmental factors that affect the distribution of the Crested Ibis are the annual average temperature and the distance to the water,which accounts for 47.7%and 24%to the model;secondly,the contribution of altitude,slope direction and NDVI to the model is 19.9%,4.5%and 3.9%respectively.It has good adaptability in the area with low altitude,while with the altitude increasing,the adaptability decreases.Therefore,it seldom finds the distribution of it over 2876 meters above sea level;the higher the NDVI index,the higher the habitat suitability of it;and the habitat suitability decreases from the north slope to the east slope along the clockwise direction.The results of the model show that the slope,the mean annual precipitation and the distance to the settlements have no effect on the habitat suitability of the Crested Ibis.2.The ROC curves generated by the MaxEnt in the model analysis of Qianyang County indicate the high reliability of the model evaluation results.The major environmental factors that affect the distribution of the Crested Ibis are altitude and the mean annual precipitation,which accounts for 34%and 22.8%respectively,followed by the distance to the road,the annual average temperature,the slope direction,the distance to the water and the slope,whose contribution rates are 18.3%?17.3%?4.8%?1.6%and 1.2%respectively.The habitat suitability of it decreases with the increase of altitude,so it rarely distributes over 1512 meters above sea level;The habitat suitability of the Crested Ibis increases with the increase of the mean annual precipitation;the distance from the road,the lower the habitat suitability of the Crested Ibis;the habitat suitability of the Crested Ibis increases with the increase of annual average temperature;The further the distance from the road,the lower the habitat suitability of the Crested Ibis;The habitat suitability of the Crested Ibis increases with the increase of the mean annual precipitation.The habitat suitability of the Crested Ibis increases from the north slope to the east slope along the clockwise direction;the farther away from the water,the lower the habitat suitability;the steeper the slope,the higher the habitat suitability of the Crested Ibis.The results of the model show that NDVI and the distance to the settlement have no effect on the habitat suitability of the Crested Ibis.3.The ROC curves generated by MaxEnt in the model analysis of Yaozhou District indicate the high reliability of the model evaluation results.The major environmental factors that affect the distribution of the Crested Ibis are the mean annual precipitation the mean annual precipitation and the distance to the water,which accounts for46.3%and 41.9%respectively,followed by NDVI,slope direction,the distance to the road,the slope and the altitude,its contribution to the model are 7%?2.5%?1.5%?0.6%and 0.2%.The higher the mean annual precipitation,the higher the habitat suitability of the crested ibis;the further the distance from the water body,the lower the habitat suitability of the crested ibis;the higher NDVI index,the lower habitat suitability of it;the habitat suitability of the crested ibis decreased from the north slope to the east slope along the clockwise direction;the further the distance from the road,the lower the habitat suitability of it;the steeper the slope,the higher the habitat suitability of it;and the habitat suitability of it decreases with the increase of altitude.Model results show that the annual average temperature and distance to the settlements have no effect on the habitat suitability of the Crested Ibis.4.Yaozhou District(262.82km2)has the largest suitable habitat area of the Crested Ibis in the whole study area,mainly distributing on both sides of Jiuzhai River Basin and near areas,followed by Ningshan County(J67.36km2),it mai1ly distributes on both sides and adjacent areas of Changan River Basin and Meridian River Basin,while Qianyang County(143.64km2)has the smallest suitable habitat area,it mainly distributes near Fengjiashan Reservoir in Qianhe River Basin.The highly suitable habitat area of Yaaozhou District is 90.7 km2,and the continuity of suitable habitat area is high;the highly suitable habitat area of Ningshan County is 46.6 km2,and the suitable habitat presents patch distribution;the highly suitable habitat area of Qianyang County is 39.66 km2,and the suitable habitat is concentrated and continuous.Owing to the landscape heterogeneity,the factors that affect the habitat suitability of the Crested Ibis vary from each other greatly in this three areas.