氮添加和干旱对亚热带4种幼树生长的影响

Effects of Nitrogen Addition and Drought on Sapling Growth of Four Subtropical Tree Species

摘要:

为探究氮沉降和干旱交互作用对亚热带森林植物生长的影响，研究了亚热带4典型树种马尾松(Pinus massoniana)、杉木(Cunninghamia lanceolata)、海南红豆(Ormosia pinnata)和木荷(Schima superba)幼树生长对不同氮添加量和干旱程度的响应。结果表明，干旱和氮添加处理2.5 a对不同树种生长的影响不同。氮添加显著促进了对照和轻度干旱下木荷与杉木的总生物量、株高和基径生长，抑制了轻度干旱下马尾松的根茎生物量和基径生长，对重度干旱下4种幼树的生长均没有显著影响。氮添加和干旱处理降低了海南红豆、马尾松和杉木的株高和总生物量，且随干旱程度的加重抑制作用更明显。不施氮和干旱对木荷总生物量和株高无显著影响；氮添加和重度干旱显著降低木荷的基径和总生物量。干旱显著增加杉木根冠比，但对其他树种根冠比无显著影响。干旱和氮添加对非豆科植物(木荷)生长的促进作用均比豆科植物(海南红豆)明显，这表明氮沉降可能加剧极端干旱对亚热带部分树种生长的抑制作用。

Abstract:

To explore the effects of nitrogen deposition and drought on plant growth in subtropical forests, the responses of four typical subtropical tree species, such as Pinus massoniana, Cunninghamia lanceolata, Ormosia pinnata and Schima superba, to different nitrogen levels and drought degrees were studied. The results showed that drought and nitrogen addition treatment for 2.5 years had different effects on the growth of different tree species. Nitrogen addition significantly increased the total biomass, plant height, and basal diameter of S. superba and C. lanceolata under the control and moderate drought treatment, but constrained the root and stem biomass and basal diameter of P. massoniana under moderate drought treatment, and had no significant effect on the growth of four tree species under severe drought treatment. Drought and nitrogen addition decreased height and total biomass of O. pinnata, P. massoniana and S. superba, and the inhibition effect became more obvious with the increase of drought degree. Without nitrogen addition, drought had no significant effect on the total biomass and plant height of S. superba. However, severe drought and nitrogen addition significantly reduced the basal diameter and total biomass of S. superba. Drought significantly increased the root-shoot ratio of C. lanceolata, but had no significant effect on other tree species. Furthermore, the effects of nitrogen addition and drought on the growth of non-leguminous species (e.g., S. superba) were more obvious than that of leguminous plants (e.g., O. pinnata). Therefore, it was that nitrogen deposition might exacerbate the inhibitory effect of extreme drought on the growth of some tree species in subtropical regions.