Decoupling of uptake‐ and transport‐related traits in absorptive roots across coexisting herbaceous species in alpine meadows

• Published in: The Journal of ecology Vol. 112; no. 4; pp. 770 - 783
• Main Authors: Zheng, Zhi, Wang, Cong, Wang, Yidi, Zhang, Yurui, Valverde‐Barrantes, Oscar J., Zhang, Wen‐Hao, Kong, Deliang
• Format: Journal Article
• Language: English
• Published: Oxford Blackwell Publishing Ltd 01.04.2024
• Subjects: Absorptivity; Anatomical structures; Arbuscular mycorrhizas; Branching; Cells; Climate change; Climatic extremes; Colonization; Decoupling; Diameters; Foraging; Foraging behavior; Fungi; Meadows; Moisture content; Nutrient availability; Nutrient uptake; Nutrients; Plateaus; Roots; Soil water; Tibetan Plateau
• ISSN: 0022-0477; 1365-2745
• DOI: 10.1111/1365-2745.14268

Abstract The anatomical structure of roots determines their function. Coexisting species complementarily forage nutrients by roots themselves (e.g. root strategy) and their fungal partners (e.g. mycorrhizal strategy), leading to a trade‐off between root strategy and mycorrhizal strategy. However, few studies have specifically evaluated whether and how the root anatomical structures are involved in this trade‐off, especially for species in alpine ecosystems limited by extreme climate. Here, absorptive root anatomical and chemical traits and three key root traits commonly associated with nutrient foraging strategies, that is root strategy indicated by first‐order root length and root branching intensity and mycorrhizal strategy indicated by arbuscular mycorrhizal fungal colonization, were examined across 68 herbaceous species in alpine meadows of the Tibetan Plateau. We observed that absorptive roots with higher branching intensity had more protoxylem poles, thinner cortices and smaller cortical cells, whereas absorptive roots with higher mycorrhizal colonization and longer first‐order roots consistently had thicker cortices and larger cortical cells. Unexpectedly, root cortical traits responsible for nutrient uptake were decoupled from stelar traits specialized in water and nutrient transportation. The decoupling may be related to the non‐coordinated changes in soil water and nutrient availability in the meadows of the Tibetan Plateau. In addition, we found that root cortical thickness and stelar radius increased at a similar rate rather than well‐reported different rates with increasing root diameter. Synthesis : Our results demonstrate that root internal makeup plays an integral role in forming the diverse nutrient foraging strategies in below‐ground. These findings provide new insights into our understanding of plant coexistence and the responses of alpine meadows to climate change on the Tibetan Plateau. 摘要 根解剖结构决定根功能。共存物种通过根策略和菌根策略互补地觅食养分，从而导致根策略和菌根策略的权衡。但很少有研究关注根解剖结构是否且如何决定根策略和菌根策略之间的权衡，特别是受极端气候限制的高寒生态系统的物种。 在本研究中，我们测定青藏高原高寒草甸68个常见草本植物吸收根的解剖性状、化学性状、以及表征养分觅食策略的三个关键性状。其中根觅食策略用根分支强度和一级根长度表征，菌根策略用菌根侵染率表征。 结果发现，分支较强的吸收根有多的原生木质部脊、薄的皮层、小的皮层细胞。菌根侵染率高，且一级根长的根有较厚皮层和大的皮层细胞。而且发现，这些吸收根负责养分吸收的皮层性状与负责水分和养分运输的中柱性状是相互独立的。这种皮层性状和中柱性状独立也许与青藏高原高寒草甸水分和养分非协同变化有关。此外，发现随根直径增加，皮层厚度和中柱大以呈相似的速率增加，这不同于以往报道的异速增加。 总之，本研究重点强调根内部结构组成也许在形成地下多样化的养分觅食策略中起着极其重要作用。因此，这些发现有助于理解青藏高原物种共存及其对气候变化的响应。