光照与土壤氮素资源变化下芒萁单优层片发育机制及扩散模式

Dicranopteris dichotoma is a perennial evergreen pteridophyte herbaceous plants with clonal propagation property and intensive growth pattern of sporophyte pinnae. As a result, they formed monodominant herbaceous synusium in numerous habitats of subtropics mountain hilly area.Their monodominant synusium habitat effect was so obvious that it poses a serious obstacle for broad-leaved forest to regenerate. However, the current study on the formation mechanism of its monodominant synusium is constrained to clonal ramet. In consequence, such research result is circumstantial. This application approaches monodominant synusium of D. dichotoma on the assumption that the overgrowth of D. dichotoma monodominant synusium is subject to clonal integration between D. dichotoma mother plant and clonal ramet. Therefore, three factors namely light, nitrogen addition and acidizing fluid will be measured and controlled during the experiment while indoor light quality control, experiment sunflecks simulation technology, and stability isotope double mark method will also be employed. It will analyse the clonal integration process between D. dichotoma mother plant and clonal ramet under the condition of full gloss, poor nitrogen as well as that of weak light, and rich nitrogen. In addition, analysis will also be made on the nitrogen distribution and accumulation pattern between D. dichotoma sporophyl, rhizome and adventitious root in summer and winter, as well as on the adaptive strategies of coniferous community from full gloss to weak light habitat at understorey. The results will reveal the developmental mechanism and dispersion pattern of D. dichotoma monodominant synusium. It is estimated that the study would provide the theory basis for zonal forest vegetation restoration of subtropics mountain hilly area and enrich the reproductive ecology theory system and study case of pteridophyte.

芒萁是一种多年生常绿蕨类草本植物，具克隆繁殖特性且孢子体羽叶密集生长，在亚热带低山丘陵区多种生境形成单优草本层片。芒萁单优层片定居者效应显著，严重阻碍阔叶森林的更新过程。然而，已有芒萁单优层片形成机理的研究材料仅限于克隆分株，结果研究结论有一定的局限性。本研究以芒萁单优层片为研究对象，基于芒萁母株、克隆分株间的克隆整合过程影响芒萁单优层片发育的科学假设，采取光照+氮素添加+酸液三因素控制试验、室内光质调控、实验光斑模拟技术和稳定性同位素双标法相结合的方法，分析全光+贫氮生境变化至弱光+富氮生境条件下芒萁母株分株之间克隆整合过程、芒萁孢子叶与根状茎及不定根之间氮素夏冬季节轮回分配积累模式和对全光至针叶树群落下层弱光生境的适应对策，揭示芒萁单优层片的发育机制和扩散模式。通过本项研究，预计可为亚热带低山丘陵区地带性森林植被恢复提供理论依据，并丰富蕨类植物繁殖生态学理论体系和研究案例。

芒萁单优层片定居者效应突显，严重阻碍亚热带低山丘陵区森林更新过程。本项目以芒萁为研究对象，构建光强+氮素等双因素控制试验，采用稳定性同位素双标法、固定样地调查相结合的方法，研究内容包括：芒萁形态指标与分株数量输出、光合生理参数变化、光斑响应、生物量分配、克隆整合机制、羽叶与根状茎间氮素季节积累模式。主要研究结果如下：.1）L2处理芒萁LCP和Rd分别减小至6.80-8.31 μmol·m-2·s-1和0.40-0.72 μmol·m-2·s-1，Pn出现最大值；芒萁羽叶色素含量和Chl a/b比值均随光强减弱而增加；CK与L3处理均能诱发芒萁羽叶活性氧含量增加。L2为芒萁最适生长光强，而盛夏全光引起芒萁枯死。.2）遮荫+酸液处理芒萁Pn均高于CK。弱光和强酸处理LSP比CK降低43.38%，LCP低至6.67μmol·m-2·s-1，弱酸性土壤+高度遮荫能增强芒萁的耐荫性。.3）未施氮和施氮的L2处理芒萁芽数分别高达21个和35.6个；施氮显著提高不同遮荫芒萁克隆分株数和芽数（p<0.05）。未施氮+L2处理芒萁生物量各参数最大，而施氮+L1处理芒萁生物量参数最大。芒萁地上生物量高比例分配于羽叶，地下生物量高比例分配根状茎。.4）春、夏季马尾松群落、疏灌草丛和林缘生境的芒萁羽叶全氮含量较高，而马尾松群落和疏灌草丛生境的芒萁根状茎全氮含量以夏季最高，林缘则以秋季最高。.5）N1、N2、N3处理芒萁克隆片段的13C吸收量分别为N0的1.50倍、2.82倍和2.34倍。N1、N2处理芒萁子株13C优先积累于根状茎。N1和N2处理碳素整合作用较显著，施氮处理向顶性碳输送特征明显。.N1处理芒萁子株吸收氮素主要积累于细根（31.73%）和根状茎（46.23%）；N2处理芒萁子株15N分配量高于N1，主要分配于根状茎（29.91%）、上层羽叶（16.84%）和根状茎生长端。母株的15N主要分配积累于上层羽叶和根状茎。N2处理氮素垂直输送特征显著，子株与母株间氮素整合作用明显。N3处理15N主要积累于芒萁子株根状茎（48.97%）。.基于碳氮克隆整合驱动、羽叶与根状茎、细根间N轮回分配和广生态幅组合特性，较全面地揭示芒萁单优层片形成的机制，并为芒萁单优层片调控和退化植被恢复提供一定的理论依据。