施氮对三个南方珍稀树种幼苗生长和生物量分配的影响

为了探讨珍稀树种对短期氮素添加的响应,该文研究了氮素添加(0、0.1、0.2、0.4和0.6g·kg~(-1)土)对观光木、棱角山矾和半枫荷幼苗生长和生物量分配的影响。结果表明:3个树种幼苗对外源氮素添加的反应不同,施氮显著促进观光木幼苗株高、基径、冠幅以及全株生物量和各部分生物量的增加,中低氮促进半枫荷幼苗的生长,但高氮抑制其生长;少量施氮对棱角山矾幼苗的形态和生物量参数没有产生显著影响,中量施氮抑制其生长。氮素营养的改变显著影响3种植物幼苗的生物量分配,观光木幼苗的根生物量比和根冠比均随施氮量的增加而显著降低;除高氮处理外,半枫荷幼苗的根生物量比和根冠比均随供氮量的增加而显著升高;棱角山矾的根生物量比和根冠比均随供氮量的增加而显著升高,可能与施氮抑制其茎叶的生长有关。总的来看,观光木幼苗更能耐受高氮条件,半枫荷幼苗次之,而棱角山矾幼苗不耐高氮;但到当年生长季末,各氮处理半枫荷幼苗的株高、基径和总相对生长速率均显著大于其它两种植物。

Effects of nitrogen addition on seedling growth and biomass allocation of three rare tree species in the south of China

In order to investigate the short term response of rare tree species to nitrogen addition, the seedling growth and biomass allocation of Semiliquidambar cathayensi, Tsoongiodendron odorum, Symplocos tetagona under five soil nitrogen levels(0, 0.1, 0.2, 0.4 and 0.6g · kg 1soil) were studied for more than four months. The results showed that the seedlings of the three tree species responded differently to the different nitrogen content levels. The plant height, basal diameter, crown width, total biomass and the biomass of each organs increased significantly in the seedlings of Tsoongiodendron odorum. Low and medium nitrogen promoted and high nitrogen inhibited the growth of Semiliquidambar cathayensis seedlings. The morphology and growth parameters of Symplocos tetagona seedlings were not significantly different among low nitrogen contents, but were inhibited under medium amount of nitrogen. The biomass allocation of three species seedlings varied significantly among different nitrogen treatments. With the increase of nitrogen levels, the root mass ratio and the ratio of root / shoot of Tsoongiodendron odorum seedlings decreased significantly, and those parameters of Semiliquidambar cathayensis seedlings increased significantly with the increase of nitrogen levels except for the highest nitrogen treatment. The root biomass ratio and the ratio of root / shoot of Symplocos tetagona seedlings increased significantly with the nitrogen content, which may relate to the growth of stem and leaf that were inhibited under medium and high nitrogen levels. Overall, Tsoongiodendron odorum seedlings were more resistant to high nitrogen loads, Semiliquidambar cathayensis seedlings came to the second, and Symplocos tetagona seedlings were not resistant to high nitrogen loads. At the end of the growing season, the height, basal diameter and total biomass relative growth rate of Semiliquidambar cathayensis seedlings were significantly higher than those of the other two plant species.