Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China.
Department of Biological Sciences, Tennessee State University, Nashville, Tennessee, United States of America.
PLoS One. 2013 Dec 27;8(12):e84130. doi: 10.1371/journal.pone.0084130. eCollection 2013.
Establishing seedlings in subtropical plantations is very important for forest health, succession and management. Information on seedling nutrient concentrations is essential for both the selection of suitable indigenous tree species to accelerate succession of the established plantation and sustainable forest management. In this study, we investigated the concentrations of nitrogen ([N]), phosphorus ([P]), and N:P ratio in leaves, stems and roots of seedlings of three indigenous tree species (Castanopsis chinensis, Michelia chapensis and Psychotria rubra) transplanted with removing or retaining understory vegetation and litter at two typical subtropical forest plantations (Eucalyptus plantation and native species plantation). We also measured the relative growth rate (RGR) of seedling height, and developed the relationships between RGR and leaf [N], [P] and N:P ratio. Results showed that treatments of understory vegetation and associated litter (i.e. removal or retained) generally had no significant effects on leaf [N], [P], N:P ratio and RGR of the transplanted tree seedlings for the experimental period. But among different species, there were significant differences in nutrient concentrations. M. chapensis and P. rubra had higher [N] and [P] compared to C. chinensis. [N] and [P] also varied among different plant tissues with much higher values in leaves than in roots for all indigenous species. RGR of indigenous tree seedlings was mostly positively correlated with leaf [N] and [P], but negatively correlated with leaf N:P ratio. Considering the low [P] and high N:P ratio observed in the introduced indigenous tree seedlings, we propose that the current experimental plantations might be P limited for plant growth.
在亚热带人工林建立幼苗对于森林健康、演替和管理非常重要。有关幼苗养分浓度的信息对于选择适宜的乡土树种以加速已建立的人工林演替和可持续森林管理至关重要。在这项研究中，我们调查了三种乡土树种（锥栗、乐昌含笑和岭南紫珠）幼苗叶片、茎和根中的氮 ([N])、磷 ([P]) 和 N:P 比，这些幼苗在两种典型的亚热带人工林（桉树人工林和乡土树种人工林）中进行了去除或保留林下植被和凋落物的处理。我们还测量了幼苗高度的相对生长率 (RGR)，并建立了 RGR 与叶片 [N]、[P] 和 N:P 比之间的关系。结果表明，在实验期间，林下植被和相关凋落物（即去除或保留）的处理一般对移栽树木幼苗的叶片 [N]、[P]、N:P 比和 RGR 没有显著影响。但在不同物种之间，养分浓度存在显著差异。乐昌含笑和岭南紫珠的 [N] 和 [P] 均高于锥栗。[N] 和 [P] 在不同植物组织中也存在差异，所有乡土树种的叶片中含量均远高于根部。乡土树种幼苗的 RGR 与叶片 [N] 和 [P] 呈正相关，但与叶片 N:P 比呈负相关。考虑到引入的乡土树种幼苗中观察到的低 [P] 和高 N:P 比，我们提出当前的实验人工林可能受到植物生长的磷限制。
