三裂叶豚草入侵对退化河岸带植被群落演替与土壤养分的影响及机制——以辽河干流为例

Effects of Ambrosia trifida Invasion on Vegetation Succession and Soil Nutrients in the Enclosed Riparian Ecosystems—A Case Study of Liaohe River Main Stream

河岸带生态系统是地球上生物多样性最高的生态系统之一,但同时也是最容易受外来物种入侵的生态系统之一,明确生物入侵对退化河岸带植被群落及土壤养分的影响,有助于探索退化河岸带植被群落自然演替过程中植被群落和土壤养分变化的影响因子及机制。以2012年开始实施围封管理的辽河干流河岸带植被群落为研究对象,沿辽河干流河岸带设置20个长期观测点位,对比分析2012~2017年优势入侵植物三裂叶豚草入侵与非入侵样地土壤养分、群落多样性和本地物种特征的差异,探讨三裂叶豚草入侵对辽河干流河岸带植被群落多样性、本地物种特征及土壤养分等的影响及机制;通过比较分析辽河干流河岸带植被群落三裂叶豚草与本地物种植物有关叶片形态、养分和光合作用等叶片性状差异,从叶片功能性状角度揭示三裂叶豚草入侵对本地物种生长的影响。结果表明:三裂叶豚草具有显著高于本地物种的叶面积、叶片氮含量、叶绿素含量和最大净光合速率,从而提升自身对光照资源的获取能力;三裂叶豚草具有显著低于本地物种的叶片碳含量和碳氮比,从而降低了叶片建成成本,提高资源利用效率,增加了自身的入侵性,表现为三裂叶豚草入侵样地本地物种的平均高度、总盖度和个体数量显著低于非入侵样地。三裂叶豚草入侵加剧了围封的退化河岸带土壤中SAN、SAP、STK的消耗,但与围封初期土壤养分相比,结果未表现出统计学显著。

Riparian ecosystem is one of the ecosystems with the largest biodiversity in the earth,meanwhile it is one of the most vulnerable ecosystem to exotic species invasion.Clarifying the effects of exotic species invasion on the vegetation community and soil nutrients is helpful to explore the driving factors and influence mechanism of secondary succession in the degraded riparian from the perspective of biological invasion.Liaohe river main stream,serving as the range of the research,has been enclosed for secondary succession since 2012,twenty long-term monitoring plots were set in the riparian corridors.In order to explore the effects and mechanism of A.trifida invasion on plant diversity,native species characteristics and soil nutrients in the main stream,the plant diversity,native species characteristics and soil nutrients between invaded samples and non-invaded samples were compared in this study.This study attempt to reveal the effect of A.trifida invasion on the growth of native species from the perspective of leaf functional traits,the differences on leaf morphology,nutrients,and photosynthesis were compared between the A.trifida and cooccurring native species.The results showed A.trifida incurred higher leaf nitrogen content,maximum net photosynthetic rate,leaf areas and chlorophyll content comparatively to the co-occurring natives,while lower leaf nitrogen content and carbon nitrogen ratio,which promoted its stronger competition for light resources and lower leaf construction cost.The average height,total coverage and number of plant individuals of the natives were significantly lower in A.trifida invaded plots thanin non-invaded plots.In the meanwhile,compared with the soil nutrients concentration in the early stage of secondary succession,the invasion of A.trifida increased the consumption of soil available nitrogen,soil available phosphorus and soil total potassium of plant community in the degrade riparian corridors after 6 years enclosure.