光照和氮磷供应比对木荷生长及化学计量特征的影响

光照和养分限制是影响林下植物生长和更新的关键影响因素，以亚热带主要常绿树种木荷（Schima superba）实生幼苗为试验对象，研究了不同光照（全光照、遮阴即45%全光照）和N、P供应比例（5，15，45）对幼苗生长和化学计量特征的影响。结果表明：（1）遮阴不仅严重抑制了木荷各器官和单株生物量积累，更加剧了P限制。尽管N、P添加对木荷生长没有显著促进作用，但N、P供应比例为5时的性状组合更有利于木荷后期生长，但高N、P供应比例可能导致P限制。（2）遮阴下叶N、P含量显著增加，但叶C/N和C/P比显著降低；不同光照处理组中各器官及总N含量均随N、P供应比例增大而显著增加，而C/N比逐渐降低；P的分配格局发生改变，全光照组各器官P含量为茎 > 叶 > 根，遮阴组各器官P含量为根 > 茎 > 叶。（3）随N、P供应比例增加或光照强度降低，木荷均趋向降低根冠比和根质比、增加叶质比或茎质比。（4）木荷生物量与各器官N、P含量、叶质比呈极显著负相关，而与C/N和C/P比及根冠比、茎质比、根质比呈极显著正相关。光强和N、P比例变化均显著影响了木荷幼苗的养分利用特征，因而木荷作为伴生树种优化林分环境对其早期生长具有重要意义。

Effects of light and N-P supply ratios on growth and stoichiometric of Schima superba

Light and nutrient limitation are two key factors affecting the growth and regeneration of understory plants. In this study, the growth and stoichiometric traits of Schima superba'' seedlings, a dominant evergreen tree species in the subtropical area, were studied under different light conditions (full light, shading of 45% full light) and N-P supply ratio (5, 15, 45). The results showed that: (1) shading not only significantly inhibited the biomass accumulation of different organs and individual plants of S.superba, but also increased P limitation. Although N and P additions did not notably promote the growth of S.superba, the growth performance was more beneficial to the later growth when the N-P supply ratio was 5, but high N-P supply ratio might lead to P limitation. (2) Shading significantly increased the content of leaf N and P, but markedly decreased the leaf C/N and C/P ratio. The content of N in each organ or whole plants increased notably with the increase of N-P supply ratio in different light treatments, while the C/N ratio gradually reduced. The distribution patterns of P element changed, and the order of the P content in full light group followed by stem > leaf > root, and that in shading group was root > stem > leaf. (3) With the increase of N-P supply ratio or the decrease of light intensity, S.superba tended to decrease the root-shoot ratio and root biomass ratio, and increase the leaf biomass ratio and stem biomass ratio. (4) The biomass of S.superba was markedly and negatively correlated with N and P content of each organ and leaf biomass ratio, while it was notably positively correlated with C/N and C/P ratio, root-root ratio, stem biomass ratio and root biomass ratio. Overall, both the change of light intensity and N-P supply ratio significantly affected the nutrient utilization characteristics of S.superba seedlings. Our results indicate that it is critically important to adjust the stand environment for the early growth of S.superba as a nurse tree species.