百山祖常绿阔叶林厚叶红淡比的萌蘖繁殖特性

Sprouting propagation characteristics of Cleyera pachyphylla in the Baishanzu subtropical evergreen forest

克隆植物在群落更新和物种多样性的维持中起着重要的作用。目前克隆生态学很少涉及自然条件下乔木的研究。通过调查百山祖5 hm2的动态监测样地中随机选取的298株厚叶红淡比母株及其产生的萌蘖情况,分析它的克隆形态可塑性、径级结构及其影响因素,以及萌蘖对母株存活的影响。结果表明:母株间所带萌蘖数量差别较大,与母株的胸径正相关;82.79%的萌蘖在距母株30 cm以内;单棵母株所发萌蘖的数量和母株—萌蘖距离在四类生境间都无显著差异,但位于母株东侧的萌蘖显著多于母株西侧的;克隆群体与整个种群的径级结构存在差异,幼苗和幼树在克隆群体所占比例高于其在整个种群中所占的比例;而母株短期存活率与其所发萌蘖数量无关。厚叶红淡比在常绿阔叶林下的克隆繁殖显示出了独特的适应性,对维持群落的稳定具有重要意义。

Sprouting extends the regeneration niche in forests. By sprouting, clonal plants play an important role in recovery of vegetation after disturbance. Many common species that make up a significant part of species diversity in forests have the potential for clonal growth or reproduction. Clonal reproduction contributes to the maintenance of species diversity, especially in clonal plant communities. Current understanding about clonal plants comes from studies of clonal herbs or shrub species in grassplot or gardens, and knowledge about clonal tree species in natural forest community is limited. Our aim is to explore the influence of habitat heterogeneity on the phenotypic plasticity of Cleyera pachyphyUa, a main clonal tree species in evergreen forests, and its advantages and disadvantages in terms of life history. A 5-hm^2（250 m x 200 m） forest dynamic plot （FDP） of Baishanzu was established in July 2003, where all trees with dbh （diameter at 1.3 m breast height）≥ 1 cm and seedlings （with true leaves and dbh ≤ 1 cm） of tree species were tagged, mapped, measured （dbh for trees and diameter at ground for seedlings）, and identified to a given species. In 2008 and 2013, all the woody plants aliveduring the previous investigation were measured, their living states were examined, and other individuals that reached 1 cm dbh during the previous 5-years were tagged, mapped, measured, and identified. In August 2011, we investigated sprouting propagation characteristics of 298 randomly selected genets of C. pachyphylla in the 5 hm2 Baishanzu forest dynamic plot （FDP）. For each genet, data of the number of sproutings, dbh, or ground diameter （when dbh 〈 1 cm） of each sprouting, and distance and direction from each sprouting to its parent ramet were collected. The habitat of each genet was classified into one of the four habitat types （Gully, Steep slope, Mild slope, and Ridge）. The data show that the amount of sprouting per genet differs among the 298 clones of C. pachyphylla. Most sprouting （82.79%） are close to （less than 30 em） their parent ramets. Our variation analysis shows there is no significant difference among four different habitats in terms of the amount of sprouting per genet and parent-daughter distance, but Spearman correlation test shows that the former is positively related to the size of parent ramet. The amount of sprouting on the eastern side of the parent ramet is significantly higher （pairwise t-test ） than that on the western side, which indicates that sprouting of C. pachyphylla is phototropic. Size distributions of the 298 clones and of the whole population are different by the X2 test. In particular, the proportions of seedlings and small saplings in clones were higher than in the whole population, which suggests the lower success of clonal propagation probably due to serious density-dependence. Logistic regression does not show significant correlation between survival of a parent ramet during 2011 to 2013 and the amount of sproutings, which indicates that the clonal propagation of C. pachyphylla is not at the cost of parent survival.