Data from: Taxonomic effect on plant base concentrations and stoichiometry at the tips of the phylogeny prevails over environmental effect along a large scale gradient

Despite the well-known importance of all elements to plant growth and nutrient fluxes in ecosystems, most studies to date have been restricted to the roles of foliar nitrogen (N) and phosphorus (P). Much less is known about cycling and pools of base cations in ecosystems and the drivers of variation in cation concentrations among plant species, even though these cations are paramount for plant and ecosystem function. In particular, little is known about the contributions of taxonomic position and environmental variation on base cation concentrations. The extent to which concentrations of elements in plants are determined by phenotypic response to their availability in current environments versus by inherent species-specific uptake and processing adaptations, should be most directly evident at the tips of the phylogeny, where inherent variation among species should reflect relatively recent adaptation to environmental variation since their common ancestry. To test this hypothesis, we explored the geographic pattern and the effects of taxonomy, climate and soil on concentrations and stoichiometry of the base cations potassium (K), sodium (Na), calcium (Ca) and magnesium (Mg) across a lineage of Artemisia species and their close relatives across northern China. We found that species identity explained the largest proportion of the total variance for all four base cations (38.3–53.8%) and their stoichiometry (35.2–59.6%). K, Na and Ca concentrations increased significantly with climate seasonality, while Ca concentration decreased with annual temperature and precipitation. Plant K concentration, K:Ca and K:Mg were negatively correlated with soil organic carbon concentrations, but positively with soil pH. Our results suggest that taxonomy still needs to be fully considered for interpreting variation in vegetation nutrition and stoichiometry along broad geographical gradients even for species at the tips of the phylogeny.

尽管所有元素对植物生长及生态系统养分通量的重要性已广为人知，但迄今为止绝大多数研究仍仅聚焦于叶片氮（N）与磷（P）的功能角色。关于生态系统中碱基阳离子（base cations）的循环与库，以及植物物种间阳离子浓度变异的驱动因子，我们的认知仍较为匮乏，尽管这些阳离子对植物与生态系统功能而言极为关键。尤为值得注意的是，我们对分类学地位与环境变异对碱基阳离子浓度的贡献机制仍知之甚少。植物体内元素浓度究竟在多大程度上由当前环境中元素有效性介导的表型响应决定，抑或是由物种固有的吸收与代谢适应策略所塑造，这一问题在系统发育（phylogeny）末端的类群中体现得最为直接——相较于共同祖先，这些物种间的固有变异应反映了其近期对环境变异的适应性演化。为验证这一假说，我们探究了中国北方地区蒿属（Artemisia）类群及其近缘物种谱系内，碱基阳离子钾（potassium, K）、钠（sodium, Na）、钙（calcium, Ca）与镁（magnesium, Mg）的浓度与化学计量比的地理格局，以及分类学、气候与土壤因子的影响。研究结果显示，物种身份可解释四种碱基阳离子总变异的最大比例（38.3%–53.8%），其化学计量比的变异解释比例则为35.2%–59.6%。钾、钠与钙浓度随气候季节波动性显著升高，而钙浓度则随年平均温度与年降水量增加而降低。植物钾浓度、钾钙比（K:Ca）与钾镁比（K:Mg）与土壤有机碳浓度呈显著负相关，却与土壤pH值呈显著正相关。本研究结果表明，即便针对系统发育末端的物种，在解释大地理梯度下植被营养与化学计量比的变异时，仍需充分纳入分类学因素以作考量。