氮沉降对半附生和地生榕属植物种子萌发和幼苗生长的影响

Effect of Nitrogen Deposition on Seed Germination and Seedling Growth in Hemiepiphytic and Terrestrial Ficus Species

摘要:

为了解大气氮沉降对榕属(Ficus)植物种子萌发和幼苗生长的影响，分析了不同氮浓度处理(0、5、30、60、90、120 mmol/L)下4种半附生和4种地生榕属植物的早期更新过程和生长情况。结果表明，在低氮(5 mmol/L)浓度下，与对照相比，8种榕树种子的萌发率、出苗率、存活率以及萌发与出苗速度无显著差异，但根系复杂度、主根长、芽长和生物量均显著增加(P<0.05)。当氮浓度超过5 mmol/L时，所有种的种子出苗和存活率、根系和芽的生长以及生物量均显著下降。在不同氮处理下，半附生榕树的存活率和生长能力均显著高于地生榕树(P<0.05)。当氮浓度为30 mmol/L时，地生榕树的存活率、根长、根系复杂度、幼苗活力指数和生物量分别降低了43.8%、85.6%、82.3%、57.4%和57.1%。在最高氮处理下(120 mmol/L), 以上指标均降低了87%以上，半附生榕树的对应指标分别降低44.9%、90.4%、58.1%、60.2%、56.3%。这表明在大气氮沉降增加的背景下，半附生榕树具有更强的耐受性和竞争力。

Abstract:

To understand the effect of atmospheric nitrogen deposition on seed germination and seedling growth of Ficus, the early regeneration process and growth conditions of four epiphytic and four terrestrial Ficus species treated with different nitrogen concentration (0, 5, 30, 60, 90, and 120 mmol/L) were analyzed. The results showed that at a low nitrogen concentration (5 mmol/L), compared with the control, there were no significant differences in the germination rate, emergence rate, survival rate, and germination and emergence speed of eight Ficus species seeds. However, the root complexity, main root length, bud length, and biomass all significantly increased (P<0.05). When the nitrogen concentration exceeded 5 mmol/L, the emergence and survival rates of seeds, the growth of roots and buds, and the biomass of all species significantly decreased. Under different nitrogen treatments, the survival rate and growth ability of epiphytic Ficus species were significantly higher than those of terrestrial Ficus species (P<0.05). When the nitrogen concentration was 30 mmol/L, the survival rate, root length, root complexity, seedling vigor index, and biomass of terrestrial Ficus species decreased by 43.8%, 85.6%, 82.3%, 57.4%, and 57.1%, respectively. Under the highest nitrogen treatment (120 mmol/L), all these indicators decreased by more than 87%, and the corresponding indicators of epiphytic Ficus species decreased by 44.9%, 90.4%, 58.1%, 60.2%, and 56.3%, respectively. Therefore, these indicate that in the context of increasing atmospheric nitrogen deposition, epiphytic Ficus species have stronger tolerance and competitiveness.