基于GIS和Maxent模型的赤水河地区濒危植物桫椤生境适宜性评价

桫椤有"蕨类植物之王"赞誉,有"活化石"之称,曾是地球上最繁盛的植物,与恐龙同期。由于地质变迁和气候变化,目前只能在极少数的"避难所"才能寻其踪迹,而赤水河地区是当下桫椤种群较为集中分布的区域。所以,了解桫椤在赤水河地区的适生区分布,对于桫椤种质资源保护、桫椤种群的恢复重建具有重要意义。基于桫椤在赤水河流域的80个桫椤分布点位、20个样地信息和22个环境因子变量,借助ArcGIS运用Maxent模型软件预测了桫椤的潜在地理分布,综合环境因子变量贡献率、刀切法检验和土地利用现状变化对赤水河地区桫椤的生境适宜性进行评价分析,确定桫椤的生境适宜潜在地理分布区域和面积。研究表明：（1）Maxent模型的预测准确度极高,模型的预测结果为"极好";（2）最暖季的降水（39.65%）、温度日平均范围（18.21%）、温度季节性变化标准差（12.69%）和降水量季节性变异性系数（6.87%）是影响桫椤生长和分布的主导环境因子,累积贡献率达77.42%,可见桫椤在生长过程中对降水、温度的变化较为敏感;（3）模型预测高适生区主要集中在四川（泸州、宜宾、自贡）、重庆、贵州（遵义）,在空间上存在明显连续性,从高适生区到不适生区呈辐射状由中心向外围逐渐递减;虽桫椤高适生区面积高达49842 km²,但现状生境破碎化,人为干扰,人工植被较多等的影响会对桫椤种群造成不利影响。综上,赤水河地区桫椤适生生境面积大、连通性好,为本地区的桫椤提供了优质的生存环境,森林的人工抚育可促进桫椤种群的延续。

Habitat suitability assessment of endangered plant Alsophila spinulosa in Chishui River area based on GIS and Maxent model

The Alsophila spinulosa is praised as "king of pteridophytes" and "living fossil". It was once the most prosperous plant on the earth, when was the same period with dinosaurs. Due to the geological changes and climate changes, the trace of Alsophila spinulosa can only be found in a few "refuges" at present, and Chishui River area is the area where the population of Alsophila spinulosa is more concentrated. Therefore, understanding the distribution of Alsophila spinulosa in Chishui River area is of great significance for protection of Alsophila spinulosa germplasm resources and the restoration and reconstruction of Alsophila spinulosa population. Based on 80 distribution points, 20 sample plots, and 22 environmental variables of Alsophila spinulosa in Chishui River Basin, the potentially geographical distribution of Alsophila spinulosa was predicted by Maxent model and ArcGIS software. The habitat suitability of Alsophila spinulosa in Chishui River region was evaluated and analyzed by combining with the contribution rate of environmental variables, knife cutting method, and land use status change. The suitable potential geographical distribution area and the area of Alsophila spinulosa habitat were determined. The results show that (1) the prediction accuracy of Maxent model is very high, and the prediction result of Maxent model is "Excellent". (2) Precipitation in the warmest quarter (39.65%), mean diurnal range (mean of monthly (max temp-min temp)) (18.21%), temperature seasonality (standard deviation×100) (12.69%), and precipitation seasonality (Coefficient of Variation) (6.87%) are the main environmental factors affecting the growth and distribution of Alsophila spinulosa. The cumulative contribution rate of the three factors is 77.42%. It shows that Alsophila spinulosa is sensitive to the changes of precipitation and temperature during the growth process. (3) The model predicts that the high suitable areas are mainly concentrated in Sichuan (Luzhou, Yibin, Zigong), Chongqing and Guizhou (Zunyi), and there is obvious continuity in space. From the high suitable areas to the unsuitable areas, they radiate and gradually decrease from the middle to the outside. Although the high suitable area of Alsophila spinulosa is as high as 49842 km², the impacts of habitat fragmentation, human disturbance and more artificial vegetation on Alsophila spinulosa population will be adverse. In conclusion, the suitable habitat area of Alsophila spinulosa in Chishui River area is large and the connectivity is good, which provides a high-quality living environment for Alsophila spinulosa in this area, and the artificial tending of forest can promote the continuation of Alsophila spinulosa population.