气候变化对孑遗植物银杉的潜在分布及生境破碎度的影响

以孑遗植物银杉(Cathaya argyrophylla Chun et Kuang)为研究对象,选取65个地理分布记录和19个生物气候因子(bio1—bio19),利用MaxEnt模型预测四种不同浓度路径下(RCP 2.6、RCP 4.5、RCP 6.0和RCP 8.5),银杉在2050s和2070s两个年代的潜在分布变化,并利用景观指数对气候变化情景下银杉适宜生境空间格局特征转变及生境破碎度变化进行分析。结果表明:在当前气候情景下,银杉适宜生境面积约占研究区面积的14.32%,主要分布于北纬24°—32°、东经105°—114°之间,位于四川盆地东南地区、云贵高原东北地区、南岭西段地区以及浙闽丘陵的北部地区。在未来不同气候情景下,银杉适宜生境变化特征显著,面积呈增加趋势,形状上整体呈四周向中间聚集。气候变化对银杉适宜生境的景观指数影响主要表现在斑块数量增多、斑块密度增加、面积加权平均形状指数变大,对分离度与聚散性影响较小;气候变化对银杉生境破碎化程度的影响表现在破碎化两极现象减弱,总体破碎化程度加剧。研究选取7个景观指数并结合PCA法得到综合的破碎度指数来定量分析银杉适宜生境破碎化程度变化,相比单一指标的定量评价和多个指标的定性分析,更能代表银杉生境的实际破碎化程度。

Impact of climate change on the potential distribution and habitat fragmentation of the relict plant Cathaya argyrophylla Chun et Kuang

In this study, using Cathaya argyrophylla Chun et Kuang based on 65 current geographical distribution records, and 19 bioclimatic factors based on maximum entropy models (MaxEnt), we estimated the transformation of the potential geographic distribution and habitat fragmentation of C. argyrophylla for the 2050s and 2070s under the climate change scenarios of RCP 2.6, RCP 4.5, RCP 6.0, and RCP 8.5 emission scenarios. The results showed that in the current climate conditions, the suitable habitat area of C. argyrophylla accounted for about 14.32% of the research area, and was mainly distributed at 24°-32°N and 105°-114°E, located Southeast of the Sichuan Basin, Northeast of the Yunnan-Guizhou Plateau, West of Nanling, and North of the Zhejiang-Fujian hilly region. Under the future climate scenarios, the characteristics of suitable habitat change of C. argyrophylla were obvious, and mainly manifested in increased suitable habitat areas and aggregations. Results of the landscape index and habitat fragmentation of suitable habitat for C. argyrophylla showed that climate change would lead to increased patches, patch density, and area weighted mean shape index, with less influence on the landscape division and aggregation indexes. Simultaneously, the effect of climate change on habitat fragmentation of C. argyrophylla mainly reflected on the weakening of the polarization phenomenon of habitat fragmentation, and higher overall fragmentation. In this research, seven indicators of the quantitative comprehensive analysis were more indicative than single indexes or multiple indicators of qualitative analysis, and were more representative of actual C. argyrophylla habitat fragmentation.