College of Earth Sciences, Chengdu University of Technology, Chengdu, Sichuan, China.
Key Laboratory of Mountain Surface Processes and Ecological Regulation, Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, Chengdu, Sichuan, China.
PLoS One. 2021 Feb 2;16(2):e0246433. doi: 10.1371/journal.pone.0246433. eCollection 2021.
As the two limiting nutrients for plants in most terrestrial ecosystems, nitrogen (N) and phosphorus (P) are essential for the development of succession forests. Vegetation N:P stoichiometry is a useful tool for detecting nutrient limitation. In the present work, chronosequence analysis was employed to research N and P accumulation dynamics and their stoichiometry during forest primary succession in a glacier retreat area on the Tibetan Plateau. Our results showed that: (1) total ecosystem N and P pools increased from 97 kg hm-2 to 7186 kg hm-2 and 25 kg hm-2 to 487 kg hm-2, respectively, with increasing glacier retreat year; (2) the proportion of the organic soil N pool to total ecosystem N sharply increased with increasing glacier retreat year, but the proportion of the organic soil and the vegetation P pools to the total ecosystem P was equivalent after 125 y of recession; (3) the N:P ratio for tree leaves ranged from 10.1 to 14.3, whereas the N:P ratio for total vegetation decreased form 13.3 to 8.4 and remained constant after 35 y of recession, and the N:P ratio for organic soil increased from 0.2 to 23.1 with increasing glacier retreat. These results suggested that organic soil N increased with increasing years of glacier retreat, which may be the main sink for atmospheric N, whereas increased P accumulation in vegetation after 125 y of recession suggested that much of the soil P was transformed into the biomass P pool. As the N:P ratio for vegetation maintained a low level for 35-125 y of recession, we suggested that N might be the main limiting element for plant growth in the development of this ecosystem.
作为大多数陆地生态系统中植物的两种限制养分，氮（N）和磷（P）是演替森林发育的必要条件。植被 N：P 化学计量比是检测养分限制的有用工具。在本研究中，我们采用年代序列分析方法研究了青藏高原冰川退缩区森林原生演替过程中氮和磷积累动态及其化学计量特征。结果表明：（1）随着冰川退缩年的增加，总生态系统 N 和 P 库分别从 97kg hm-2 增加到 7186kg hm-2 和 25kg hm-2 增加到 487kg hm-2；（2）随着冰川退缩年的增加，有机土壤 N 库占总生态系统 N 的比例急剧增加，但有机土壤和植被 P 库占总生态系统 P 的比例在退缩 125 年后相当；（3）树叶的 N：P 比值范围为 10.1-14.3，而总植被的 N：P 比值从 13.3 下降到 8.4，并在退缩 35 年后保持不变，有机土壤的 N：P 比值从 0.2 增加到 23.1。这些结果表明，随着冰川退缩年数的增加，有机土壤 N 增加，这可能是大气 N 的主要汇，而在退缩 125 年后，植被中 P 的积累增加表明，大部分土壤 P 已转化为生物量 P 库。由于植被的 N：P 比值在退缩 35-125 年内保持在较低水平，我们认为 N 可能是该生态系统发育过程中植物生长的主要限制元素。
