黄河流域河南段菊科主要外来种对不同环境梯度的适应性研究 英文标题:The Adaptability of Invasion Alien Species of Composite in Response to Different Environmental Gradients in Henan Section of the Yellow River Watershed
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黄河流域河南段流经河南省21个县市，是黄河中下游重要的一段，是中华文明的发源地，同样也是我国重要的粮食产区。该区域从东向西，从平原经丘陵到山地形成了一个连续变化的环境梯度，为外来种的入侵提供了多样的生境条件。我国的188种外来入侵植物中，仅菊科植物就有49种。在黄河流域河南段的调查研究中，菊科外来种主要有小蓬草(Conyzacanadensis)、钻形紫菀(Astersubulatus)、三叶鬼针草(Bidenspilosa)、苏门白酒草(Conyzasumatrensis)、香丝草(Conyzabonariensis)和一年蓬(Erigeronannuus)共6种。在黄河流域河南段设置具代表性的29个样点，每个样点选择河滩地、农田边、人工林和撂荒地等四种常见的生境类型，每种生境设立一个大样地(20m×20m)，在大样地内用五点取样法设置小样方(1m×1m)，对每个小样方内出现的菊科外来种进行观测。观测指标包括:叶层高、花序高、径粗、叶片长宽(叶面积)、叶片厚度、叶片数和花果数等。在2010年的春季、夏季和秋季，对该区域进行调查，调查结果表明:小蓬草在黄河流域河南段分布广泛，数量较多;钻形紫菀、苏门白酒草和香丝草多分布在河滩地和人工林;三叶鬼针草基本分布在河滩地。该区域内，小蓬草的潜在危害最严重，其次是钻形紫菀，三叶鬼针草主要对河滩地形成潜在危害。根据实验中的调查以及查阅的相关资料，大致可以估计出小蓬草和钻形紫菀在该区域传播扩散的路径以及传播方式。小蓬草在1860年在烟台发现，然后在1886和1887年分别在湖北宜昌和四川南溪采到。因而小蓬草可能是从烟台经过山东境内传至黄河流域河南段，或者从四川传入陕西，由陕西传播至该区域;然后纵向传播扩散至两岸各种生境中。钻形紫菀最早于1947年在湖北武昌被报道，此后钻形紫菀所产生的大量种子可能经武汉扩散至郑州，然后在黄河流域河南段经水路或陆路扩散开来。小蓬草和钻形紫菀的种子小且轻，具有冠毛，主要通过风力传播，但是人为干扰加速了其扩散传播。小蓬草在黄河下游的平原地区广泛分布且数量较多，说明平原地区利于其传播扩散。随着海拔的升高，景观类型的变化以及热量条件的降低，河滩地小蓬草各指标表现为下降趋势;在春季，农田边的小蓬草各指标是先上升后下降的趋势，而在夏季其各指标无明显变化规律，这与农田边较强的人为干扰有关;人工林和撂荒地的小蓬草各指标均在丘陵地区达到峰值，这可能由于丘陵地区生物多样性高，群落内竞争较为激烈，致使小蓬草个体植株较大。从夏秋季小蓬草花果数的变化，得出丘陵山地地区的小蓬草较早进入繁殖期。以上说明在该区域小蓬草对景观类型的变化有较强的适应力。不同季节，小蓬草的形态差异较大。其中小蓬草的高度和茎粗随季节变化而升高，叶面积为了适应夏季高温降低蒸腾作用而减小、叶片厚度也增厚，因而资源的分配利用就体现在叶片数量上，小蓬草叶片数在夏季达到最大值。夏季有一小部分小蓬草进入繁殖期，大部分小蓬草在秋季进入繁殖的高峰期，植株叶片掉落、营养生长变缓停止而转化为繁殖力。以上说明小蓬草为适应该区域复杂的气候变化能自我调节生长的分配，尤其是叶片性状和花果数等的变化，具有较强的适应性。根据对周边环境的观察和对样地的调查结合对当地村民的询问对四种生境的干扰程度大致排序为:农田边>撂荒地>人工林>河滩地。在这四种生境中农田边和撂荒地的小蓬草由于人为施肥和灌溉的影响各形态指标均要大于河滩地和人工林，且植株较为高大粗壮、叶面积较大、叶片数较为密集;而河滩地和人工林各形态指标因季节不同大小相异，这主要和光照环境和水分条件等有关。由于人工林的郁闭度，致使小蓬草较高，但茎较细，叶面积较大，叶片较稀疏。在这四种生境类型中，干扰越强，小蓬草各形态指标越高，说明小蓬草能适应有干扰的生境。钻形紫菀对不同景观类型的适应与小蓬草的规律基本一致，其季节变化与小蓬草较一致。其中钻形紫菀叶片面积在夏季比春季要大，这主要与钻形紫菀本身叶片结构能有效防止蒸腾作用有关。在这四种生境类型中(除人工林外)，干扰越强，钻形紫菀各形态指标越高，说明其能适应较强的干扰。人工林中的钻形紫菀各指标比其他生境中的都低，这说明充足的光照对钻形紫菀的生长起到重要的作用。黄河流域河南段，从东到西形成了一个连续变化的环境梯度，小蓬草、钻形紫菀等菊科外来植物能通过调节自身生长和营养物质在各器官的分配，来适应该区域复杂的环境梯度的变化，说明其具有较强的适应性。黄河流域河南段主要在农业生态系统背景下小样方的调查研究，可为以后找出外来物种入侵与农业发展平衡之间的关系提供研究依据;并且还可以为以后在更大尺度上对入侵种研究的综合分析提供参考。此外，在黄河流域河南段对菊科具有潜在危害性的外来入侵种的调查研究，可为以后防止其爆发以及防除提供了研究基础，具有重要的意义。
The Henan section of the Yellow River Basin flows through 21 counties and cities in Henan Province, serving as a crucial segment of the middle and lower reaches of the Yellow River, the birthplace of Chinese civilization, and an important grain-producing area in China. This region forms a continuously changing environmental gradient from east to west, transitioning from plains to hills and then to mountains, providing diverse habitats for the invasion of alien species. Among the 188 alien invasive plant species in China, 49 belong to the Asteraceae family. In the survey of the Henan section of the Yellow River Basin, the main alien Asteraceae species are six: Conyza canadensis, Aster subulatus, Bidens pilosa, Conyza sumatrensis, Conyza bonariensis, and Erigeron annuus. A total of 29 representative sampling sites were established in the Henan section of the Yellow River Basin. At each site, four common habitat types were selected: river beaches, farmland edges, artificial forests, and abandoned lands. For each habitat type, a large plot (20 m × 20 m) was set up, and small quadrats (1 m × 1 m) were arranged using the five-point sampling method within the large plot. Observations were conducted on alien Asteraceae species present in each small quadrat. Observation indicators included height of the leaf layer, inflorescence height, stem diameter, leaf length and width (leaf area), leaf thickness, number of leaves, and number of flowers and fruits. Surveys were conducted in spring, summer, and autumn of 2010. The survey results showed that Conyza canadensis was widely distributed and abundant in the Henan section of the Yellow River Basin; Aster subulatus, Conyza sumatrensis, and Conyza bonariensis were mostly distributed in river beaches and artificial forests; Bidens pilosa was basically distributed in river beaches. In this region, Conyza canadensis poses the most severe potential harm, followed by Aster subulatus, while Bidens pilosa mainly causes potential harm to river beaches. Based on the field surveys and relevant literature consulted, the spread paths and modes of Conyza canadensis and Aster subulatus in this region can be roughly estimated. Conyza canadensis was first discovered in Yantai in 1860, and then collected in Yichang, Hubei and Nanxi, Sichuan in 1886 and 1887, respectively. Thus, Conyza canadensis may have spread to the Henan section of the Yellow River Basin via Shandong Province from Yantai, or introduced from Sichuan to Shaanxi and then to this region; subsequently, it spread longitudinally to various habitats on both banks of the river. Aster subulatus was first reported in Wuchang, Hubei in 1947. Since then, the large number of seeds produced by Aster subulatus may have spread from Wuhan to Zhengzhou, and then dispersed via water or land routes in the Henan section of the Yellow River Basin. The seeds of both Conyza canadensis and Aster subulatus are small and light, with pappus, and are mainly dispersed by wind, but human disturbance accelerates their spread. Conyza canadensis is widely distributed and abundant in the plain areas of the lower Yellow River, indicating that plain areas are conducive to its spread and diffusion. With the increase of altitude, changes in landscape types, and decrease of heat conditions, the various indicators of Conyza canadensis in river beaches show a downward trend. In spring, the indicators of Conyza canadensis at farmland edges first increased and then decreased, while there was no obvious regular change in summer, which is related to the strong human disturbance at farmland edges. The indicators of Conyza canadensis in artificial forests and abandoned lands reached their peaks in hilly areas, which may be because hilly areas have high biodiversity and intense intraspecific and interspecific competition within the community, resulting in larger individual plants of Conyza canadensis. From the changes in the number of flowers and fruits of Conyza canadensis in summer and autumn, it can be concluded that Conyza canadensis in hilly and mountainous areas enters the reproductive period earlier. The above indicates that Conyza canadensis has strong adaptability to changes in landscape types in this region. The morphology of Conyza canadensis varies greatly across different seasons. The height and stem diameter of Conyza canadensis increase with seasonal changes. To adapt to the high summer temperatures and reduce transpiration, leaf area decreases and leaf thickness increases, so the allocation and utilization of resources are reflected in the number of leaves, which reaches its maximum in summer. A small portion of Conyza canadensis enters the reproductive period in summer, while most enter the peak reproductive period in autumn, when plant leaves fall, vegetative growth slows down and stops, and shifts to reproductive capacity. The above indicates that Conyza canadensis can self-regulate the allocation of growth, especially changes in leaf traits and number of flowers and fruits, to adapt to the complex climate changes in this region, showing strong adaptability. Based on observations of the surrounding environment, surveys of the sample plots, and inquiries with local villagers, the disturbance degree of the four habitats can be roughly ranked as: farmland edges > abandoned lands > artificial forests > river beaches. In these four habitats, the morphological indicators of Conyza canadensis in farmland edges and abandoned lands are higher than those in river beaches and artificial forests due to the effects of human fertilization and irrigation, and the plants are taller and thicker, with larger leaf area and denser leaves. The morphological indicators of river beaches and artificial forests vary with seasons, which is mainly related to light environment and water conditions. Due to the canopy closure of artificial forests, Conyza canadensis in artificial forests is taller, but has thinner stems, larger leaf area, and sparser leaves. In these four habitat types, the stronger the disturbance, the higher the morphological indicators of Conyza canadensis, indicating that Conyza canadensis can adapt to disturbed habitats. The adaptation of Aster subulatus to different landscape types is basically consistent with that of Conyza canadensis, and its seasonal changes are also similar to those of Conyza canadensis. The leaf area of Aster subulatus is larger in summer than in spring, which is mainly related to the leaf structure of Aster subulatus itself that effectively prevents transpiration. In these four habitat types (except artificial forests), the stronger the disturbance, the higher the morphological indicators of Aster subulatus, indicating that it can adapt to strong disturbance. The indicators of Aster subulatus in artificial forests are lower than those in other habitats, indicating that sufficient light plays an important role in the growth of Aster subulatus. The Henan section of the Yellow River Basin forms a continuously changing environmental gradient from east to west. Alien Asteraceae plants such as Conyza canadensis and Aster subulatus can adapt to the complex changes in the environmental gradient of this region by regulating their own growth and the allocation of nutrients to various organs, indicating their strong adaptability. This survey study in the Henan section of the Yellow River Basin, mainly based on small quadrat investigations under the background of agricultural ecosystems, can provide a research basis for future studies to identify the relationship between alien species invasion and the balance of agricultural development; it can also provide references for comprehensive analysis of invasive species studies at larger scales in the future. In addition, the survey and study of potentially harmful alien invasive Asteraceae species in the Henan section of the Yellow River Basin provide a research foundation for future prevention of their outbreak and control, which is of great significance.
