School of Geographical Sciences, Hebei Key Laboratory of Environmental Change and Ecological Construction, Hebei Normal University, Shijiazhuang, Hebei 050024, China; Qianyanzhou Ecological Research Station, Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China.
Qianyanzhou Ecological Research Station, Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China.
Sci Total Environ. 2023 Feb 25;861:160661. doi: 10.1016/j.scitotenv.2022.160661. Epub 2022 Dec 5.
Nitrogen (N) is a major element limiting plant growth and metabolism. Nitrogen addition can influence plant growth, N uptake, and species interactions, while phosphorus (P) addition may affect N acquisition. However, knowledge of how nutrient availability influences N uptake and species interactions remains limited and controversial. Here, pot experiments were conducted for 14 months, in which conifers (Pinus massoniana and Pinus elliottii) and broadleaved trees (Michelia maudiae and Schima superba) were planted in monoculture or mixture, and provided additional N and P in a full-factorial design. Nitrogen addition increased the biomass, but P addition did not significantly affect the biomass of the four subtropical species. Combined N and P (NP) addition had no additive effect on plant biomass over N addition. Total plant biomass was significantly positively correlated to root traits (branching intensity and root tissue density) and leaf traits (net photosynthetic rate, stomatal conductance, and transpiration rate), but negatively correlated to root diameter in response to nutrient addition. Plant uptake rates of NH or NO were not altered by N addition, but P or NP additions decreased NH uptake rates and increased NO uptake rates. Neighboring conifers significantly inhibited NH and NO uptake rates of the two broadleaf species, but neighboring broadleaves had no effects on the N uptake rates of pine species. The effects of nutrient additions on interspecific interactions differed among species. Nitrogen addition altered the interaction of P. elliottii and M. maudiae from neutral to competition, while P addition altered the interaction of P. massoniana and M. maudiae from neutral to favorable effects. Increasing nutrient availability switched the direction of interspecific interaction in favor of pines. This study provides insights into forest management for productivity improvement and optimizing the selection of broadleaf species regarding differences in soil fertility of subtropical plantations.
氮（N）是限制植物生长和代谢的主要元素。氮添加可以影响植物生长、N 吸收和物种相互作用，而磷（P）添加可能会影响 N 的获取。然而，养分供应如何影响 N 吸收和物种相互作用的知识仍然有限且存在争议。在这里，进行了为期 14 个月的盆栽实验，其中针叶树（马尾松和湿地松）和阔叶树（深山含笑和木荷）在单种或混种中种植，并在完全因子设计中添加额外的 N 和 P。氮添加增加了生物量，但 P 添加并未显著影响四种亚热带物种的生物量。N 和 P 的组合（NP）添加对植物生物量的影响没有超过 N 添加的附加效应。总植物生物量与根特性（分枝强度和根组织密度）和叶特性（净光合速率、气孔导度和蒸腾速率）呈显著正相关，但与养分添加时的根直径呈负相关。氮添加没有改变植物对 NH 或 NO 的吸收速率，但 P 或 NP 添加降低了 NH 的吸收速率，增加了 NO 的吸收速率。相邻的针叶树显著抑制了两种阔叶树种对 NH 和 NO 的吸收速率，但相邻的阔叶树对松树种的 N 吸收速率没有影响。养分添加对种间相互作用的影响因物种而异。氮添加改变了湿地松和深山含笑的相互作用从中性到竞争，而 P 添加改变了马尾松和深山含笑的相互作用从中性到有利影响。增加养分供应改变了种间相互作用的方向，有利于松树种。本研究为提高生产力和优化亚热带人工林土壤肥力差异下阔叶树种选择的森林管理提供了思路。
