Yan Tao, Wang Liying, Wang Peilin, Zhong Tianyu
State Key Laboratory of Herbage Improvement and Grassland Agro-ecosystems, College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou, China.
Qingyuan Forest CERN, National Observation and Research Station, Shenyang, China.
Front Plant Sci. 2023 Dec 5;14:1282884. doi: 10.3389/fpls.2023.1282884. eCollection 2023.
Leaf functional traits play critical roles in plant functioning. Although the functional traits of overstory trees have been extensively studied, minimal research has been conducted regarding understory species, despite the understory layer is an important component of temperate forests. Such insufficiency limit the broader understanding of processes and functions in forest ecosystems, particularly when under the increasing atmospheric nitrogen (N) deposition. Here, we investigated the responses of 18 leaf functional traits in six understory herbaceous species within young and mature stands (three species per stand) in larch () plantations that subjected to 12 years of anthropogenic N addition. We found that N addition did not significantly impact the photosynthetic traits of understory herbaceous species in either stand; it only led to increased chlorophyll content in Jacq. Similarly, with the exception of decreases in the predawn leaf water potential of L., N addition did not significantly affect leaf hydraulic traits. With the exception of changes to adaxial epidermis thickness in Ser. (decreased) and (increased), N addition had negligible effects on leaf anatomical traits and specific leaf area, however, interspecific variations in the plasticity of leaf anatomical traits were observed. Stable responses to N addition were also observed for nonstructural carbohydrates (NSC) and their components (soluble sugars and starch), with the exception of L., which exhibited increases in NSC. Overall, our results suggest that the functional traits of understory herbaceous species exhibit stability under conditions of long-term N enrichment in temperate plantations.
叶片功能性状在植物功能中起着关键作用。尽管对上层树木的功能性状已进行了广泛研究，但对于林下物种的研究却很少，尽管林下层是温带森林的重要组成部分。这种不足限制了对森林生态系统过程和功能的更广泛理解，尤其是在大气氮（N）沉降增加的情况下。在此，我们调查了在经过12年人为添加氮的落叶松人工林中，幼龄林和成熟林（每个林分三种物种）内六种林下草本物种的18个叶片功能性状的响应。我们发现，添加氮对任一林分林下草本物种的光合性状均无显著影响；仅导致兴安升麻（Cimicifuga dahurica）的叶绿素含量增加。同样，除了毛脉酸模（Rumex gmelinii）黎明前叶片水势降低外，添加氮对叶片水力性状无显著影响。除了酸模叶蓼（Polygonum lapathifolium）（降低）和酸模（Rumex acetosa）（增加）的近轴表皮厚度发生变化外，添加氮对叶片解剖性状和比叶面积的影响可忽略不计，然而，观察到叶片解剖性状可塑性的种间差异。对于非结构性碳水化合物（NSC）及其组分（可溶性糖和淀粉），除了毛脉酸模表现出NSC增加外，对添加氮也观察到稳定的响应。总体而言，我们的结果表明，在温带人工林长期氮富集条件下，林下草本物种的功能性状表现出稳定性。
