外来逃逸植物肿柄菊群落建立与云南多样化地理环境耦合过程研究

Biological invasions are having a major impact on the Earth’s ecosystems, and are the serious issues that humans are facing. In the future, the problem of biological invasions will be more serious because increases in international travel and trade escalate the extent and frequency of species transfer around the world. Plant introductions have been implictated as important sources of alien plants invading other global biodiversity hotspots. Understandings of invasive mechanisms facilitate to guide the work of plant introduction and management of alien plant. We will study the coupling processes and mechanism between the diverse geographic environment of Yunnan, China, and the community establishment of Tithonia diversifolia, an alien invasive plant. Yunnan of China is a mountainous region with diverse geographic environment and climate zones. Tithonia diversifolia, an alien invasive plant species, is widely distributed in tropical, southern and central sub-tropical regions at the range of elevations of 100-2000m in Yunnan. The shrubby plant has adapted to diverse environment of Yunnan in invasive processes. Successful biological invasions involve multiple interactions between the invasive species and the physical and biological characteristics of the recipient environment. The outcome of the interactions can enhance the abilities of invasiveness and result in expansion of invasive species. In order to identify the coupling processes between diverse environment and the community establishment of T. diversifolia, we will investigate the community constructions of T. diversifolia in different invaded habitats and confirm the time of individual establishment in communities through the growth-ring analysis, then will analyze the processes of community establishment in different environment. We will also measure the contribution of seed and seeding to community establishment and analyze the relationships between seeding establishment and habitats. Additionally, we will consecutively collect the oldest individuals of T. diversifolia along the gradual transitions of elevation and climatic zones in different habitats, and verify the courses of invasion in trans-habitats and trans-climatic zones. Finally, we will deduce the historical dynamics and processes of community establishment of T. diversifolia in diverse habitats, and clarify how T. diversifolia responds to various changes of environment in processes of community establishment.

外来种入侵被认为是人类所面临最严重的全球性环境问题之一。许多外来引种植物逃逸栽培环境后通过逐步适应当地环境而变为入侵种。阐明外来植物对多种新环境的适应过程和机制，对于科学地制定引种计划和管理外来种具有重要的理论和现实意义。在云南立体气候、多样化地理环境条件下，呈灌木状生长的外来逃逸植物肿柄菊已普遍入侵多个生物气候类型区，肿柄菊与地理环境之间表现出多种适应关系。通过对不同生物气候类型和生境条件下的肿柄菊群落连续取样调查，结合植株基茎年轮分析技术，准确推算植株在任意地点的定居时间，反演肿柄菊群落在多种环境下建立的动态和过程。从群落尺度、局域尺度（相同生物气候类型）、区域尺度（跨生物气候类型）三种空间尺度上分析肿柄菊群落建立与多样化地理环境的耦合过程，探讨肿柄菊在群落建立过程中对生境变化的响应规律，从外来逃逸植物群落建立与环境耦合的时空格局角度揭示肿柄菊在云南多样化地理环境下的成功入侵机制。

肿柄菊（Tithonia diversifolia）是菊科肿柄菊属植物，在20世纪30年代前后被引入云南南部地区，目前已广泛分布于云南省热带、亚热带地区，为云南省危害较为严重的外来入侵植物之一。从不同尺度水平（群落尺度、局域尺度、区域尺度）探讨肿柄菊群落建立与云南多样化地理环境的耦合过程，能够揭示肿柄菊成功入侵过程和机制。目前肿柄菊分布区覆盖云南省71个县（区），与10多年前相比肿柄菊有明显的向北和向高海拔扩散趋势。在较低纬度和海拔区域肿柄菊的分布主要受人为干扰影响，在向更高纬度和海拔扩散的过程中气候因素影响更为突出。公路在肿柄菊的远距离扩散过程中起着重要作用，云南密集的高速公路网建设促进了肿柄菊沿公路扩散效率，加速了肿柄菊侵占新领地的过程。单优势种肿柄菊群落在建立过程中植株形态由草本状向木本状发展，群落中肿柄菊基茎较粗分枝增多会对较细分枝的产生有抑制作用，群落发展到一定阶段后群落中较粗茎级的分枝控制着群落发展，群落地上生物量会持续增加。在群落不同入侵阶段，肿柄菊生长形态变化更有利于群落的建立和巩固。随着肿柄菊群落建立时间增长，土壤中全钾和有效磷含量显著增加（P<0.05），土壤有机质、全氮和水解性氮含量有减少趋势，但表现不显著（P>0.1）。在跨区域尺度范围，肿柄菊每果序平均结实量148.4~196.4粒，每果序平均结籽量0.8~98.1粒，每果序平均结实量和结籽量在地区间都具有极显著差异（P<0.001），但结实量变异系数仅为8.1%，结籽量变异系数高达82.7%。肿柄菊平均每果序结实量与年均温和一月均温有微弱的负相关关系（P<0.1），与降雨、海拔和纬度没有相关关系；但是，肿柄菊结籽率与年均温、一月均温均有显著的正相关关系（P<0.05），与海拔高度有显著的负相关关系（P<0.05），与降雨和纬度没有相关关系（P>0.1）。说明在区域尺度范围结籽率是影响肿柄菊总体结籽量的决定因素。在肿柄菊分布的北亚热带地区结籽量的大量减少导致繁殖体压力极大降低，肿柄菊侵占新领地的能力减弱，限制了进一步向更高纬度和海拔扩散能力。