Wang Wei, Zhao Jiamin, Xing Zhen, Wang Xiangtao
College of Resources and Environmental Sciences, Tibet Agriculture and Animal Husbandry University, Nyingchi, Tibet, China.
Key Laboratory of Forest Ecology in Tibet, Ministry of Education, Xizang Agriculture and Animal Husbandry College, Nyingchi, Tibet, China.
Front Plant Sci. 2023 Apr 6;14:1092872. doi: 10.3389/fpls.2023.1092872. eCollection 2023.
Understanding vegetation C, N, and P stoichiometry helps us not only to evaluate biogeochemical cycles and ecosystem functions but also to predict the potential impact of environmental change on ecosystem processes. The foliar C, N, and P stoichiometry in Northern Tibetan grasslands, especially the controlling factors, has been highlighted in recent years. In this study, we have collected 340 plant samples and 162 soil samples from 54 plots in three grassland types, with the purpose of evaluating the foliar C, N, and P stoichiometry and underlying control factors in three grassland types along a 1,500-km east-to-west transect in the Northern Tibetan Plateau. Our results indicated that the averaged foliar C, N, and P concentrations were 425.9 ± 15.8, 403.4 ± 22.2, and 420.7 ± 30.7 g kg; 21.7 ± 2.9, 19.0 ± 2.3, and 21.7 ± 5.2 g kg; and 1.71 ± 0.29, 1.19 ± 0.16, and 1.59 ± 0.6 g kg in the alpine meadow (AM), alpine steppe (AS), and desert steppe (DS) ecosystems, respectively. The foliar C and N ratios were comparable, with values of 19.8 ± 2.8, 20.6 ± 1.9, and 19.9 ± 5.8 in the AM, AS, and DS ecosystems, respectively. Both the C/P and N/P ratios are the lowest in the AM ecosystem, with values of 252.2 ± 32.6 and 12.8 ± 1.3, respectively, whereas the highest values of 347.3 ± 57.0 and 16.2 ± 3.2 were obtained in the AS ecosystem. In contrast, the soil C, N, C/P, and N/P values decreased from the AM to DS ecosystem. Across the whole transects, leaf C, N, and P stoichiometry showed no obvious trend, but soil C and N concentrations showed an increasing trend, and soil P concentrations showed a decreasing trend with the increasing longitude. Based on the general linear model analysis, the vegetation type was the dominant factor controlling the leaf C, N, and P stoichiometry, accounting for 42.8% for leaf C, 45.1% for leaf N, 35.2% for leaf P, 52.9% for leaf C/N, 39.6% for leaf C/P, and 48.0% for leaf N/P; the soil nutrients and climate have relatively low importance. In conclusion, our results supported that vegetation type, rather than climatic variation and soil nutrients, are the major determinants of north Tibet grassland leaf stoichiometry.
了解植被的碳（C）、氮（N）和磷（P）化学计量不仅有助于我们评估生物地球化学循环和生态系统功能，还能预测环境变化对生态系统过程的潜在影响。近年来，藏北草原的叶片C、N和P化学计量，尤其是其控制因素受到了关注。在本研究中，我们从三种草地类型的54个样地中采集了340个植物样本和162个土壤样本，目的是评估藏北高原沿1500公里东西向样带的三种草地类型的叶片C、N和P化学计量及其潜在控制因素。我们的结果表明，高寒草甸（AM）、高寒草原（AS）和荒漠草原（DS）生态系统中，叶片C、N和P的平均浓度分别为425.9±15.8、403.4±22.2和420.7±30.7克/千克；21.7±2.9、19.0±2.3和21.7±5.2克/千克；以及1.71±0.29、1.19±0.16和1.59±0.6克/千克。叶片C和N的比值相当，在AM、AS和DS生态系统中的值分别为19.8±2.8、20.6±1.9和19.9±5.8。C/P和N/P比值在AM生态系统中最低，分别为252.2±32.6和12.8±1.3，而在AS生态系统中最高，分别为347.3±57.0和16.2±3.2。相比之下，从AM到DS生态系统，土壤C、N、C/P和N/P值降低。在整个样带中，叶片C、N和P化学计量没有明显趋势，但土壤C和N浓度呈增加趋势，土壤P浓度随经度增加呈下降趋势。基于一般线性模型分析，植被类型是控制叶片C、N和P化学计量的主导因素，对叶片C的贡献率为42.8%，对叶片N的贡献率为45.1%，对叶片P的贡献率为35.2%，对叶片C/N的贡献率为52.9%，对叶片C/P的贡献率为39.6%，对叶片N/P的贡献率为48.0%；土壤养分和气候的重要性相对较低。总之，我们的结果支持植被类型而非气候变异和土壤养分是藏北草原叶片化学计量的主要决定因素。
