Global mycorrhizal status drives leaf δ15N patterns

Nitrogen (N) availability, which can be represented by the natural
abundance of the stable N isotope δ15N, is crucial to understanding
ecosystem-level N dynamics. Specific ecosystems are dominated by different
types of mycorrhizae, which can relate to biogeochemistry and affect
ecosystem functioning. However, few studies have addressed the impacts of
different mycorrhizal associations on variations in foliar δ15N due to
climatic and soil physicochemical factors; prior instances of foliar δ15N
modeling have not included mycorrhizal types. Here, we used
machine learning to produce a global map of foliar δ15N based on climatic,
edaphic, vegetation, and dominant mycorrhizal factors. The
predicted global average foliar δ15N value was 0.69‰. Plants in tropical
areas were predicted to have significantly larger foliar δ15N values than
plants from subtropical, temperate, and boreal areas. The mean annual
temperature was identified as the primary driver of spatial foliar δ15N
patterns. These results provide isotopic evidence of greater N limitations
in temperate and boreal regions than tropical or subtropical regions.
Furthermore, non-mycorrhizal plant species had the highest foliar δ15N
values, followed by plants associated with arbuscular mycorrhizae, orchid
mycorrhizae, ectomycorrhiza, then ericoid mycorrhizae.  Overall,
changes in foliar δ15N were predicted to be closely associated with the
type of mycorrhizal association. This study highlights the importance of
incorporating mycorrhizal data to accurately assess patterns of foliar
δ15N on a global scale. Ultimately, our findings contribute to a greater
understanding of N cycling dynamics across plant types and global
ecosystems.

氮（N）有效性可通过稳定氮同位素δ¹⁵N的自然丰度表征，是理解生态系统尺度氮循环动态的关键。不同菌根（mycorrhizae）类型主导特定生态系统，其与生物地球化学过程密切相关，并会影响生态系统功能。然而，鲜有研究探讨不同菌根共生类型在气候与土壤理化因子影响下对叶片δ¹⁵N变异的调控作用；此前的叶片δ¹⁵N建模研究均未纳入菌根类型这一变量。本研究基于气候、土壤、植被以及优势菌根因子，借助机器学习（machine learning）方法构建了全球叶片δ¹⁵N分布图谱。模型预测的全球叶片δ¹⁵N平均值为0.69‰。热带地区植物的叶片δ¹⁵N值显著高于亚热带、温带与寒带植物。年均温被确定为驱动叶片δ¹⁵N空间分布格局的核心因子。本研究结果为温带与寒带地区氮限制程度高于热带及亚热带地区提供了同位素证据。此外，非菌根植物的叶片δ¹⁵N值最高，其次依次为丛枝菌根（arbuscular mycorrhizae）植物、兰科菌根（orchid mycorrhizae）植物、外生菌根（ectomycorrhiza）植物与欧石楠类菌根（ericoid mycorrhizae）植物。总体而言，叶片δ¹⁵N的变化与菌根共生类型密切相关。本研究强调，在全球尺度下准确评估叶片δ¹⁵N分布格局时，纳入菌根相关数据具有重要意义。最终，本研究结果有助于深化对不同植物类型与全球生态系统氮循环动态的认知。

搜集汇总

背景与挑战

背景概述

该数据集通过机器学习方法，基于全球气候、土壤、植被和优势菌根类型等数据，生成了叶片δ15N（氮稳定同位素）的全球分布图，揭示了菌根类型是驱动叶片δ15N空间变化的关键因素。数据集包含叶片δ15N观测值及17个环境预测变量，用于分析氮循环动态和生态系统功能，特别强调了菌根数据在评估全球氮模式中的重要性。