Institut de Recherche sur les Forêts, Université du Québec en Abitibi-Témiscamingue, 341 rue principale Nord, Amos, Québec J9T 2L8, Canada.
Unité de recherche et de développement en agroalimentaire, Université du Québec en Abitibi-Témiscamingue, 79, Rue Côté, Notre-Dame-du-Nord, Québec J0Z 3B0, Canada.
Tree Physiol. 2024 Oct 3;44(10). doi: 10.1093/treephys/tpae120.
Fine roots play a crucial role in soil nutrient and water acquisition, significantly contributing to tree growth. Fine roots with a high specific root length (SRL) and small diameter are often considered to help trees grow fast. However, inconsistencies in the literature do not provide a clear basis on the effect of root functional traits, such as SRL or root mass density (RMD), on tree growth rate in phylogenetically related trees. Our aim was to examine relationships between tree growth rate and root functional traits, using clones displaying different growth rates in a hybrid poplar plantation located in New Liskeard, ON, Canada. Fine roots (diameter < 2 mm) samples were collected using soil cores at depths of 0-20, 20-40 and 40-60 cm, and analyzed for morphological, chemical and architectural traits. High SRL and thin fine roots were associated with the least productive clones, which is not consistent with the root economics spectrum (RES) theory. However, the most productive clone had larger fine root diameter and higher root lignin concentrations, probably reducing root construction and maintenance costs and carbon losses. Therefore, at the 0-20 and 20-40 cm depths, tree growth rates showed positive correlations with root diameter and root lignin concentrations, but negative correlations with SRL and root soluble compounds concentration. Increasing RMD at the 0-20 cm depth promoted tree growth rates, showing the importance of soil exploration in the topsoil for tree growth. We conclude that fine root variation does not always follow the RES hypothesis and argue that the rapid growth rate of trees may also be driven by fine root growth in diameter and mass in phylogenetically related trees.
细根在土壤养分和水分获取中起着至关重要的作用，对树木的生长有重要贡献。具有高比根长（SRL）和小直径的细根通常被认为有助于树木快速生长。然而，文献中的不一致性并没有为根功能特征（如 SRL 或根质量密度（RMD））对系统发育相关树木的生长速率的影响提供明确的依据。我们的目的是研究树木生长速率与根功能特征之间的关系，使用在加拿大安大略省新利斯卡德的一个杂交杨树林中表现出不同生长速率的克隆来进行研究。使用土壤芯在 0-20、20-40 和 40-60cm 的深度采集细根（直径<2mm）样本，并对其形态、化学和结构特征进行分析。高 SRL 和细根与生产力最低的克隆有关，这与根经济谱（RES）理论不一致。然而，生产力最高的克隆具有较大的细根直径和较高的根木质素浓度，这可能降低了根的构建和维护成本以及碳损失。因此，在 0-20 和 20-40cm 的深度，树木生长速率与根直径和根木质素浓度呈正相关，与 SRL 和根可溶性化合物浓度呈负相关。在 0-20cm 深度增加 RMD 促进了树木的生长速率，表明在表土中进行土壤探测对树木的生长很重要。我们得出结论，细根的变化并不总是遵循 RES 假说，并认为树木的快速生长速率也可能是由系统发育相关树木的细根直径和质量的生长所驱动。
