凋落物覆盖及掩埋对不同质量的藜蒴种子萌发和幼苗生长的影响

The impacts of seed mass,litter cover and burial on seedling emergence and early development of Castanopsis fissa

以南亚热带常见的先锋乡土树种藜蒴(Castanopsis fissa)为研究对象,通过室内萌发试验,分析了种子质量、凋落物覆盖和掩埋对种子萌发及幼苗早期生长的影响。结果表明,藜蒴种子能否成功萌发并形成幼苗的决定性因素是种子的掩埋深度。掩埋显著抑制了藜蒴种子萌发及形成幼苗的过程,随掩埋深度的增大,这种抑制作用越明显。掩埋对幼苗的存活和生物量没有显著影响,但可提高幼苗根部生物量的分配。深度掩埋时,质量大的种子在幼苗形成过程中具明显优势;而置于土壤表层或浅埋的种子成苗率与种子质量的相关性较低。大质量种子形成的幼苗更易于存活,在生物量的积累方面也表现出一定的优势。凋落物覆盖未抑制幼苗的出土,且对幼苗的存活和生长具有明显的促进作用,表现在可提高幼苗的相对生长率以及生物量的积累。另外,凋落物的覆盖明显提高了幼苗生物量在其冠部的分配。因而,若利用直接播撒藜蒴种子的方式改造南亚热带退化草坡,理论上应尽可能选用大质量的种子直接播种于地表,并覆以原有的地表凋落物,以促进藜蒴幼苗成功建立。

The impacts of seed mass, litter covering and burial on seed germination and seedling development of Castanopsis fissa, an important pioneer species commonly used in the restoration of degraded subtropical grassland in southern China, were investigated by placing seeds of three weight classes at four positions （0 cm above the soil, 0, 2 and 5 cm beneath soil） with or without litter cover. Results showed that seedling emergence was restrained by burial significantly, and the negative effect was intensified with burial depth increased. Meanwhile, burial increased biomass allocation to roots of seedlings. Large seeds predominated in seedling emergence when buried 2 and 5 cm beneath soil, while no distinct advantages of large seeds over small ones were observed in seedling emergence when seeds placed on the soil surface or 0 cm beneath. In the early stage of development, seedlings originated from large seeds held higher survivor rates than that from small seeds and accumulated more biomass. The presence of leaf litter could facilitate seedling establishment for it increased seedling emergence rate, survivor rate, relative growth ratio and biomass accumulation. Meanwhile, litter cover increased biomass allocation to the shoots of seedlings significantly. Therefore, to rehabilitate the shrubland in southern China with Castanopsis fissa as a pioneer indigenous species through direct seeding, large seeds should be selected to place on soil surface and then covered by former litter in order to facilitate seedling establishment.