Institute of Tibet Plateau Ecology, Tibet Agriculture & Animal Husbandry University, Nyingchi, Tibet 860000, China; CAS Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization & Ecological Restoration and Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610041, China.
CAS Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization & Ecological Restoration and Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610041, China.
Sci Total Environ. 2022 Nov 25;849:157906. doi: 10.1016/j.scitotenv.2022.157906. Epub 2022 Aug 6.
Increasing atmospheric nitrogen (N) deposition has resulted in phosphorus (P) limitation in multiple terrestrial ecosystems, yet how plants coordinate aboveground and belowground strategies to adapt to such P deficiency remains unclear. In this study, we conducted a field N fertilization experiment in two alpine coniferous plantations (Picea asperata Mast. and Pinus armandii Franch.) with different soil N availability on the eastern Tibetan Plateau of China, to examine N addition effects on plant nutrient limiting status and plant adaptive strategies corresponding to aboveground P conservation and belowground P acquisition. The results showed that N addition aggravated P deficiency in both plantations, as indicated by decreased needle P concentrations and increased N:P ratios, and that plant strategies for addressing such P deficiency differed in the two plantations with different initial soil N availabilities. In the P. asperata plantation with relatively high N availability, significantly enhanced needle phosphatase activity and shifts in P fraction allocation (downregulation of the structural P fraction and increased allocation to the residual P fraction) co-occurred with increased rhizosphere effects on phosphatase activity under N addition, indicating a synergistic strategy of aboveground P conservation and belowground P mining to alleviate P deficiency. In the P. armandii plantation with relatively low N availability, however, N addition only enhanced phosphatase activity and increased allocation to residual P fraction in the aboveground but had little effect on belowground P acquisition-associated traits, suggesting a decoupling relationship between aboveground P conservation and belowground P acquisition. This study highlights the vital significance of initial soil nutrient availability in regulating the coordination of aboveground and belowground strategic alternatives, emphasizing the need to integrate soil nutrient conditions for a holistic understanding of forest adaptation to anthropogenic N enrichment.
大气氮（N）沉降增加导致多个陆地生态系统出现磷（P）限制，但植物如何协调地上和地下策略以适应这种 P 缺乏仍不清楚。在这项研究中，我们在中国青藏高原东部的两个高山针叶林（云南松和华山松）中进行了野外 N 施肥实验，这些林分具有不同的土壤 N 有效性，以研究 N 添加对植物养分限制状况的影响以及与地上 P 保护和地下 P 获取相对应的植物适应策略。结果表明，N 添加加剧了两个林分的 P 缺乏，表现为针叶 P 浓度降低和 N：P 比值增加，并且具有不同初始土壤 N 有效性的两个林分中，植物应对这种 P 缺乏的策略也不同。在 N 有效性相对较高的云南松林分中，与 N 添加下根际对磷酸酶活性的增强以及 P 分配的变化（结构 P 分配减少和残余 P 分配增加）同时发生，表明了地上 P 保护和地下 P 挖掘的协同策略可以缓解 P 缺乏。然而，在 N 有效性相对较低的华山松林分中，N 添加仅增强了地上部分的磷酸酶活性和对残余 P 分配的增加，但对与地下 P 获取相关的特性几乎没有影响，这表明地上 P 保护和地下 P 获取之间存在解耦关系。这项研究强调了初始土壤养分有效性在调节地上和地下战略选择的协调中的重要意义，强调需要整合土壤养分条件，以全面了解森林对人为 N 富集的适应。
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