喀斯特地区飞机草与本土植物间水分利用关系研究

The invasion of alien species is known as the second large factor caused the decrease of biological diversity over the world. It threatens the ecosystem security and brings seriously damage. The effects of increased globalization, international trade, tourism, transport and travel have dramatically enhanced the spread of invasive plant species which can lower biological diversity, alter ecosystem function, change resource availability, and influence human health. Human influence often contributes to the disturbance of habitats, making them more susceptible to invasion, facilitating many alien plants by freeing nutrients and by changing natural disturbance regimes. Chromolaena odorata is one of the most hazardous invasive weeds and widely distributes in south of China, causing serious damages to agricultural production and human health.. The karst region is one of the most vulnerable eco-environments in China. Due to the particularly geological property, soil hydrology is known to be an important environmental variable that affects the distribution and survivorship of vegetation in karst ecosystem. The invasion of C. odorata in karst area intensifies the vulnerability of ecosystem. The water use relationship between C. odorata and native species has yet to be determined.. Under different C. odorata invaded areas, we will determine whether water niche differentiations of C. odorata and native species in karst area are related to the water stress and the root distribution patterns. Drought stress of C. odorata will be explored by conducting physiology measurements, including photosynthesis rate, plant water potential and biomass allocation. Soil physico-chemical properties will also be conducted that including bulk density, porosity, water content, TOC, TP and TN. Stable isotopes are used to trace the path of different water sources to investigate the difference in water use strategies between C. odorata and native species. D and 18O values within plant xylem water and soil water will be measured when physiology measurements and soil analyses during the growing season and dry and wet seasons. Species composition will be investigated in different C. odorata invaded sites..This study will demonstrate the water use relationships between C. odorata and native species in karst region, and reveal the invasive mechanism of C. odorata deeply. This study is helpful to our understanding on the invasive process of alien species and has profound significance to the treatment of alien species and the protection of ecosystem.

外来生物入侵是导致全球生物多样性降低的第二大因素，严重威胁着生态系统安全。喀斯特地区是我国主要的生态环境脆弱区之一，该地区土壤层浅薄、土壤持水能力弱，水分是限制该地区植被生长和分布的主要环境因子。飞机草作为我国主要的外来有害入侵杂草，在喀斯特地区的入侵导致生态系统更为脆弱。在入侵过程中，飞机草与本土植物之间的水分利用关系尚不清楚。本项目以喀斯特地区飞机草与本土植物为研究对象，在飞机草不同入侵程度下，同步观测土壤理化性状和植物抗逆生理生态指标。稳定同位素技术与传统方法相结合，定量计算植物对各种水源利用比例；基于生态位分化理论，探讨飞机草与本土植物的水分利用关系，从水分利用角度揭示飞机草入侵机制，预测飞机草入侵趋势，为飞机草防治、生态系统保护和植被恢复提供重要的理论依据。

外来生物入侵是导致全球生物多样性降低的第二大因素，严重威胁着生态系统安全。飞机草作为我国主要的外来有害入侵杂草，在喀斯特地区的入侵导致生态系统更为脆弱。在入侵过程中，飞机草与本土植物之间的水分利用关系尚不清楚。本项目以飞机草为研究对象，在飞机草不同入侵程度下，分析植物群落结构和土壤理化性质变化。通过控制实验，研究飞机草对水分胁迫的生理响应机制。基于稳定同位素技术，定量计算植物对各种水源利用比例；基于生态位分化理论，探讨飞机草与本土植物的水分利用关系，从水分利用角度揭示飞机草入侵机制。本课题主要研究工作和成果包括：（1）喀斯特地区飞机草不同入侵程度下植被分布特征。对飞机草入侵区生态系统调查结果表明当飞机草入侵超过一定程度后，导致本土植物的生物多样性降低，破坏植物本土群落结构；同时导致土壤物理结构恶化、肥力下降。（2）飞机草生理生态特征对水分胁迫的响应。水分胁迫会导致飞机草生物量下降，但地下和地上生物量比升高；飞机草叶绿素a、叶绿素b和总叶绿素含量受水分胁迫后显著降低，光合作用减弱，飞机草最大净光合速率、光饱和点和水分利用效率等随着土壤含水量降低而减小；飞机草通过提高SOD和POD等抗氧化酶活性来减小水分胁迫对细胞膜系统造成的伤害。（3）飞机草与本土植物水分利用策略研究。飞机草具有灵活的水分转换能力，不同生境中的飞机草主要水分来源有所不同，一般在降雨少的时候以土壤水为主，在降雨较多的季节飞机草优先利用雨水或泉水。本土植物黄荆条、香薷、地桃花同样具有转换主要水分来源的能力，同样在降雨较多的季节优先选择利用雨水或泉水；黄荆条和地挑花与飞机草之间存在水分生态位分化，水资源竞争较少，而香薷与飞机草水分来源相同，水分竞争激烈。此外，黄荆条和飞机草在干湿季主要水分来源不同，存在明显水分生态位分化，避免飞机草入侵过程中与本土植物进行水分竞争，有利于飞机草入侵和扩散。