State Key Laboratory of Subtropical Silviculture, College of Environment and Resources, College of Carbon Neutrality, Zhejiang A&F University, Hangzhou 311300, China.
State Key Laboratory of Subtropical Silviculture, College of Environment and Resources, College of Carbon Neutrality, Zhejiang A&F University, Hangzhou 311300, China.
Sci Total Environ. 2024 Jun 1;927:172424. doi: 10.1016/j.scitotenv.2024.172424. Epub 2024 Apr 15.
Atmospheric nitrogen (N) deposition inevitably alters soil nutrient status, subsequently prompting plants to modify their root morphology (i.e., adopting a do-it-yourself strategy), mycorrhizal symbioses (i.e., outsourcing strategy), and root exudation (i.e., nutrient-mining strategy) linking with resource acquisition. However, how N deposition influences the integrated pattern of these resource-acquisition strategies remains unclear. Furthermore, most studies in forest ecosystems have focused on understory N and inorganic N deposition, neglecting canopy-associated processes (e.g., N interception and assimilation) and the impacts of organic N on root functional traits. In this study, we compared the effects of canopy vs understory, organic vs inorganic N deposition on eight root functional traits of Moso bamboo plants. Our results showed that N deposition significantly decreased arbuscular mycorrhizal fungi (AMF) colonization, altered root exudation rate and root foraging traits (branching intensity, specific root area, and length), but did not influence root tissue density and N concentration. Moreover, the impacts of N deposition on root functional traits varied significantly with deposition approach (canopy vs. understory), form (organic vs. inorganic), and their interaction, showing variations in both intensity and direction (positive/negative). Furthermore, specific root area and length were positively correlated with AMF colonization under canopy N deposition and root exudation rate in understory N deposition. Root trait variation under understory N deposition, but not under canopy N deposition, was classified into the collaboration gradient and the conservation gradient. These findings imply that coordination of nutrient-acquisition strategies dependent on N deposition approach. Overall, this study provides a holistic understanding of the impacts of N deposition on root resource-acquisition strategies. Our results indicate that the evaluation of N deposition on fine roots in forest ecosystems might be biased if N is added understory.
大气氮（N）沉降不可避免地改变土壤养分状况，随后促使植物改变其根系形态（即采用自助策略）、菌根共生（即外包策略）和根系分泌物（即养分挖掘策略）与资源获取相联系。然而，N 沉降如何影响这些资源获取策略的综合模式尚不清楚。此外，森林生态系统中的大多数研究都集中在林下 N 和无机 N 沉降上，忽略了树冠相关过程（例如，N 截留和同化）以及有机 N 对根功能特性的影响。在这项研究中，我们比较了树冠与林下、有机与无机 N 沉降对毛竹植物八种根系功能特性的影响。我们的结果表明，N 沉降显著降低了丛枝菌根真菌（AMF）的定殖，改变了根系分泌物释放率和根系觅食特性（分枝强度、比根面积和根长），但不影响根组织密度和 N 浓度。此外，N 沉降对根系功能特性的影响随沉降方式（树冠与林下）、形式（有机与无机）及其相互作用而显著变化，表现出强度和方向的变化（正/负）。此外，在树冠 N 沉降下，比根面积和根长与 AMF 定殖呈正相关，在林下 N 沉降下，与根系分泌物释放率呈正相关。在林下 N 沉降下，而不是在树冠 N 沉降下，根特性的变化被分为协同梯度和保守梯度。这些发现意味着依赖 N 沉降方式的养分获取策略的协调。总体而言，本研究提供了对 N 沉降对根资源获取策略影响的全面理解。我们的研究结果表明，如果在林下添加 N，对森林生态系统细根的 N 沉降评估可能存在偏差。
