气候变化对四合木适生区及空间迁移的影响

Impacts of climate change on the suitable habitats and spatial migration of Tetraena mongolica

四合木(Tetraena mongolica)是中国特有的孑遗种植物,被誉为植物中的“大熊猫”,由于早期过度放牧、滥垦乱伐等人为因素,使这一物种一度濒临灭绝。预测气候变化对分布范围的影响可为四合木的野生资源保存与可持续利用提供科学基础和参考依据。利用27个地理分布点和从Worldclim网站下载的18个环境因子数据,基于优化后的MaxEnt模型预测四合木在中国的地理分布格局和限制其分布的主导环境因子。结果表明,通过调用R平台ENMeaval程序包进行模型优化,最终确定FC=LQHPT,RM=4,优化参数后的模型精度优于默认参数下的模型精度。优化后的MaxEnt模型预测测试数据集和训练数据集AUC值均在0.98以上;现代四合木潜在地理分布的总的适生区面积约为124.45×10^(4) km^(2),高适生区面积约为3.35×10^(4) km^(2),高适生区主要集中于内蒙古阿拉善左旗、鄂托克旗以北,黄河上游达拉特旗以南,乌海市、巴彦淖尔市以东,鄂尔多斯市以西;宁夏回族自治区北部石嘴山市及贺兰山北麓也有少量分布。最干月降水量(36.95%)、年降水量(14.83%)、表层土壤有机碳含量(11.21%)、海拔(9.38%)、最干季度平均气温(6.28%)、年均温(5.49%)、人类活动因子(3.10%)、表层土砾石含量(3.01%)、等温性(2.44%)、表层土壤碳酸盐或石灰含量(2.32%)、表层土壤酸碱度(2.02%)和最冷月最低气温(1.32%)是影响四合木分布的主要环境因子。分析发现,随着气候暖化,四合木新增适生面积将会逐步缩减,现代潜在高适生区可能依然是其未来的避难所,其分布重心可能将会向东迁移。本研究为进一步明确四合木适宜栖息地在中国的地理分布格局和制定有效的保护策略提供了科学参考。

Tetraena mongolica is an endemic relict plant species in China and is known as the“giant panda”of the plant world.Due to human activities such as excessive grazing,over-cultivation,and deforestation in the early stages,this species was once on the brink of extinction.Predicting the impact of climate change on its distribution range can provide a scientific basis and reference for the conservation and sustainable utilization of wild resources of Tetraena mongolica.Using 27 geographical distribution points and environmental data from 18 factors downloaded from the WorldClim website,the dominant environmental factors restricting the distribution pattern of Tetraena mongolica in China were predicted based on the optimized MaxEnt model.The results showed that by calling the ENMeval package in the R platform for model optimization,the model accuracy with optimized parameters(FC=LQHPT,RM=4)was higher than that with default parameters.The Area Under Curve values of the optimized MaxEnt model for the test dataset and the training dataset were both above 0.98.The total suitable area for the potential geographic distribution of modern Tetraena mongolica was approximately 124.45×10^(4) km^(2),with a high suitability area of about 3.35×10^(4) km^(2).The high suitability area was mainly concentrated in the north of Alxa Zuoqi and Etoke Banner in the Inner Mongolia,south of the upper reaches of the Yellow River,east of Wuhai City and Bayan Nur City,and west of Ordos City.There were also a few distributions in Shizuishan City in the northern Ningxia Hui Autonomous Region and at the northern foot of Helan Mountain.The main environmental factors affecting the distribution of Tetraena mongolica were the driest month precipitation(36.95%),annual precipitation(14.83%),surface soil organic carbon content(11.21%),elevation(9.38%),average temperature of the driest quarter(6.28%),annual average temperature(5.49%),human activity factor(3.10%),surface gravel content(3.01%),isothermality(2.44%),surface soil carbonate or lime content(2.32%),surface soil PH(2.02%),and lowest temperature of the coldest month(1.32%).The analysis revealed that with climate warming,the additional suitable area for Tetraena mongolica would gradually shrink,and the current potential high suitability area might still be its future refuge.Its distribution center might shift eastward.The study provides a scientific reference for further clarifying the geographical distribution pattern of the suitable habitats for Tetraena mongolica in China and formulating effective protection strategies.