Global increase in nitrogen (N) deposition influences the belowground allocation of plant photosynthates and the formation of roots and rhizosphere-associated symbionts as well as soil nutrient availability, thereby affecting the nutrient acquisition by trees. Trees obtain nutrients primarily through fine root growth or mycorrhizal symbioses. These two mechanisms have an antagonistic relationship, but how they are modified by N deposition remains unknown. Arbuscular mycorrhizae (AM) and ectomycorrhizae (EM) are the two dominant types of mycorrhizal fungi that form symbioses with the roots of most trees. However, the divergent adaptive mechanisms and nutrient acquisition strategies of trees with a symbiotic relationship with AM (AM trees) or with EM (EM trees) in response to N deposition are unclear. To clarify these points, we conducted a meta-analysis of 116 studies on global forest ecosystems. Following prolonged (>2 years) or high-load (>140 kg ha⁻¹ y⁻¹) N addition, both AM and EM trees decrease the amount of energy allocated to mycorrhizal symbioses and increasingly rely on fine roots to obtain nutrients. The faster growth of AM trees than of EM trees under N deposition is partly attributed to their divergent nutrient acquisition strategies: the fine root biomass and length decreased significantly in EM trees (−13% and −17%, respectively), but not in AM trees. Furthermore, the acid phosphatase activity increased more for the AM trees than for the EM trees (28% and 4%, respectively), indicative of a greater abundance of available P for the AM trees than for the EM trees after N addition. Consequently, AM trees have advantages in terms of root morphology and phosphatase activity over EM trees, suggesting they are better adapted to high N deposition.

氮 (N) 沉积的全球增加影响植物光合产物的地下分配以及根和根际相关共生体的形成以及土壤养分的有效性，从而影响树木对养分的获取。树木主要通过细根生长或菌根共生来获取养分。这两种机制具有拮抗关系，但它们如何被 N 沉积修饰尚不清楚。丛枝菌根 (AM) 和外生菌根 (EM) 是两种主要类型的菌根真菌，它们与大多数树木的根部形成共生关系。然而，与 AM（AM 树）或与 EM（EM 树）共生关系的树木在响应 N 沉积时的不同适应机制和养分获取策略尚不清楚。为了澄清这些要点，我们对 116 项关于全球森林生态系统的研究进行了荟萃分析。长期（>2 年）或高负荷（>140 kg ha⁻¹  y ⁻¹) N 此外，AM 和 EM 树都减少了分配给菌根共生体的能量，并越来越依赖细根来获取养分。在氮沉积下，AM 树的生长速度比 EM 树快，部分原因是它们不同的养分获取策略：EM 树的细根生物量和长度显着降低（分别为 -13% 和 -17%），但在 AM 中没有树木。此外，AM 树的酸性磷酸酶活性比 EM 树的增加更多（分别为 28% 和 4%），表明在添加 N 后，AM 树的可用 P 丰度高于 EM 树。因此，AM 树在根部形态和磷酸酶活性方面优于 EM 树，表明它们更适应高氮沉积。