School of Forestry, Northeast Forestry University, Harbin, China.
Agricultural Research Institute, Mingora, Pakistan.
Sci Rep. 2018 Jun 29;8(1):9815. doi: 10.1038/s41598-018-27832-0.
Manchurian walnut and larch are key timber species of northeast China but information on (fine) root traits of both species is scarce. Plasticity of root traits in mixed plantations has been studied rarely although this could give important insights into mechanisms of root competition. This study examined root traits by branching order in 30-yr-old monocultures and their plasticity in mixed plantations. In monocultures, Manchurian walnut and larch differed in key fine root traits. Larch roots hold more absorptive root orders, larger diameter and lower specific root length/area. Walnut root orders featured greater cortex:stele ratios, N-concentrations and respiration rates. Under interspecific competition, the proportion of walnut root tips increased, the biomass/length of larch root orders 1-3 decreased. Larch possessed a greater morphological and anatomical plasticity of terminal root orders than walnut. Mycorrhizal colonization rates of walnut were reduced. Both species differed fundamentally in their fine root properties. Absorptive fine root orders reacted plastic under interspecific competition while traits of higher root orders remained unchanged. In mixture, larch roots possessed a greater plasticity in traits related to resource uptake (efficiency) than walnut roots whose reaction norm is suggested to be predominantly based on interference competition via juglone exudation.
胡桃楸和落叶松是中国东北的主要用材树种，但有关这两个树种的（细）根特性的信息却很少。尽管混合林分中根系性状的可塑性可以为根系竞争机制提供重要的见解，但对其研究却很少。本研究通过 30 年生的单种群落和混交林分中的分枝顺序来研究根系性状及其可塑性。在单种群落中，胡桃楸和落叶松在关键细根特性上存在差异。落叶松根具有更多的吸收根序、更大的直径和更低的比根长/面积。胡桃楸根序具有更大的皮层：中柱比、N 浓度和呼吸速率。在种间竞争下，胡桃楸根尖端的比例增加，落叶松根序 1-3 的生物量/长度减少。落叶松的终端根序具有比胡桃楸更大的形态和解剖可塑性。胡桃楸的菌根定殖率降低。这两个树种的细根特性存在根本差异。吸收细根序在种间竞争下表现出可塑性，而较高根序的特性保持不变。在混交林中，与胡桃楸相比，落叶松在与资源摄取（效率）相关的性状上具有更大的可塑性，而胡桃楸的反应规范可能主要基于通过胡桃醌的分泌进行的干扰竞争。
