三峡库区消落带外来植物入侵与景观基质组成结构的关联性

Relationship between alien plant invasion and landscape matrix in the water-level fluctuating zone of the Three Gorges Reservoir,China

外来物种入侵过程不仅受入侵地生境的影响,也受到周边景观基质的影响。厘清景观基质对外来入侵物种的影响,对于外来物种的入侵管控具有重要意义。本研究针对长江三峡库区消落带植物群落开展调查,评估三峡库区消落带外来植物入侵现状;在岸线以上(含消落带)2000 m范围内划分出10个景观格局尺度,采用14个指标分析景观基质组成结构;通过主成分分析和相关分析,探究景观基质组成结构对外来植物入侵的影响以及空间尺度效应。结果表明:三峡库区消落带外来入侵植物共17科36属42种,其分布呈现出以涪陵为界的特征,涪陵至三峡大坝的外来入侵物种多于涪陵至江津段。整体上(2000 m尺度内),景观基质破碎化程度越高,外来植物入侵难度越大;景观连通性越高,外来植物越容易入侵。大尺度上(1200~2000 m)的景观组成结构对入侵植物多样性的影响明显大于小尺度(200~1000 m),其中,1200~1400 m尺度的影响最强,呈明显的空间尺度效应。不同入侵植物受景观基质组成结构的影响也表现出尺度效应。其中,苍耳和大狼把草与景观组成结构指标在各个尺度下均表现出弱相关性,而狼把草及小蓬草与景观基质组成结构表现出强相关性。景观基质组成结构与外来植物入侵密切关联,且具明显尺度效应。外来植物入侵可追溯到大尺度的景观基质,以小尺度内草地、森林等斑块类型为"脚踏石"过渡,最终达到消落带。针对消落带外来植物的管控,应该在强化消落带生境管理的基础上,加强景观基质不同尺度上的土地利用管理和优化,形成多元化的综合管控模式。

Invasive process of alien species is affected by not only the invaded habitats,but also the surrounding landscape matrix.Understanding the effects of landscape matrix on alien species is of great significance for controlling invasive alien species.We surveyed plant communities along the water-level fluctuating zone(WLFZ)of the Three Gorges Reservoir.Invasive status of alien plant species was evaluated.Totally 10 spatial scales of the surrounding landscape matrix in the scope of 2000 m(including WLFZ)were classified,and 14 landscape indices were applied to analyze the landscape matrix composition and configuration.Using the principal component analysis and correlation analysis,the effects of landscape matrix on the alien invasive plant species and associated scale effect were tested.Results showed that a total of 42 alien invasive plant species were found in the WLFZ,belonging to 17 families and 36 genera.Fuling was a dividing place to differentiate invasive species distribution.The number of the alien invasive species between Fuling and the Three Gorges Dam was found more than that between Fuling and Jiangjin.For the all scales(within 2000 m).The higher the landscape matrix fragmentation was,the more difficult the alien species invading.The higher landscape connectivity was,the easier the alien species invading.The effects of landscape matrix composition and configuration on the invasive plant diversity at large scales(1200-2000 m)was more significant than those at small scales(200-1000 m),in which landscape matrix composition and configuration at 1200-1400 m showed the strongest effect,demonstrating a significant spatial scale effect.Different invasive plant species showed the scale effects of landscape matrix composition and configuration.At all scales,Xanthium strumarium and Bidens frondosa showed weak correlations with landscape indices,but Bidens tripartita and Erigeron canadensis showed strong correlations.Landscape matrix was closely related to invasive plant species,and demonstrated a significant scale effect.The alien invasive plant species could be traced to the landscape matrix at large scales.Grassland and forest patches at the small scales could be used as the‘stepping stone’for the alien species transiting before they arrived at the WLFZ.In order to control alien plants in the WLFZ,land-use management and optimization should be strengthened at different scales of landscape matrix on the basis of enhancement of habitat management.A diversified comprehensive control for alien species should thus be taken into account.