基于MAXENT模型的贺兰山岩羊生境适宜性评价

生境评价对物种保护具有非常重要的意义。本研究在GIS空间技术的支持下，于2010年到2011年间，在贺兰山岩羊分布区采集其地理分布点数据以及环境变量数据，并运用MAXENT模型对贺兰山区域岩羊的生境适宜性进行评价分析。模型的评价结果达到优秀水平，研究结果表明：岩羊生境选择的主要影响因子为矿区、坡度、海拔和道路，生境适宜区主要分布于贺兰山东坡（宁夏贺兰山国家级自然保护区）的西南部，而西坡（内蒙古贺兰山国家级自然保护区）有少量分布，适宜生境面积总和为1 006.9 km2，占研究区域面积的28%。岩羊偏爱于海拔1 500－2 300 m的山势陡峭地带，建议对矿区和道路这两种人为干扰因素采取相应的措施，以提高岩羊的生境质量，促进其种群发展。

Habitat suitability assessment of blue sheep in Helan Mountain based on MAXENT modeling

Habitat evaluation has an important significance for management of wildlife populations and conservation planning. Geographic Information Systems (GIS) and abundant landscape-level data provide new opportunities for biologists to evaluate wildlife habitat quality. Maximum Entropy (MAXENT) is a recently introduced modeling technique, achieving high predictive accuracy and enjoying several additional attractive properties. With the purpose of predicting habitat for blue sheep (Pseudois nayaur) in the Helan Mountain Range, we collected the occurrence records for this species and the environmental factors, the occurrence records were collected from the study area from 2010 to 2011, and the date of environmental factors were extracted from the Thematic Mapper (TM) image of Helan Mountain in 2007. The method relies on the combined use of GIS and Maximum Entropy (MAXENT) model in this research. GIS was used to produce the data needed in the model, MAXENT can model species geographic distributions with presence-only data, and is suitable for the research because absence data are not available for blue sheep. A map indicated the distribution of habitat suitability of blue sheep in Helan Mountain generated from the data and software. In this paper, the method of Receiver Operating Characteristic (ROC) curve analysis was used to assess the accuracy of MAXENT model, the area under ROC curve (AUC) of the model was 0.915, indicating that the result of assessment was excellent, and the results showed the relationships between the distribution of blue sheep and the environmental factors, the result of Jackknife test indicated that the mining, slope, altitude and road were the main factors influencing habitat selection of blue sheep. Along with the increase of slope, distance from mine and road, the habitat suitability increased gradually, and habitat suitability decreased gradually with the increasing distance from water. Suitable habitat was mainly distributed in southwest of Ningxia Helan Mountain National Nature Reserve (east part) and lesser distributed in the Inner-Mongolia Helan Mountain National Nature Reserve (west part), with the total area of 1 006.9km², accounting for 28% of the total assessment area. Blue sheep preferred to use montane savanna dominated and the rugged slopes at elevations of 1 500-2 300 m. There were two factors interfered in achieving accurate results, one was difficult to reach occurrence points for the steep terrain, and the other was that we could not get the information of traffic flow on every road. During the research, we reduced the error by recording the nearest position to the target point and choosing the main road on the maps. The results showed that the most serious human interferences were mining and road, more regulatory actions are needed to be taken in those aspects to improve the habitat's quality as well as promote the progress of the population.