Contribution and influencing factors of ectomycorrhizal fungi to nitrogen acquisition for Abies fargesii var. faxoniana and Betula utilis on the eastern Qingzang Plateau

doi:10.17521/cjpe.2025.0252

Abstract

Abstract:

Aims Ectomycorrhizal trees obtain nitrogen (N) through direct root uptake from soil (root pathway) and via ectomycorrhizal fungal mycelia translocated to roots (mycelia pathway). However, the relative contribution of the mycelial pathway to tree N acquisition (f_fungi) remain highly uncertain, and the key influencing factors are not well defined in natural ecosystems.

Methods In this study, we employed the ¹⁵N natural abundance method to quantify the relative contribution of the mycelial pathway to N acquisition in two ectomycorrhizal trees (Abies fargesii var. faxoniana and Betula utilis) on the eastern Qingzang Plateau. We further analyzed the influencing factors of f_fungi.

Important findings Our results showed that the contribution of mycelia pathways to total N uptake was comparable to that of root pathways in both A. fargesii var. faxoniana and B. utilis. Specifically, the mycelia pathway contributed to 33.6%-71.8% of total N uptake in A. fargesii var. faxoniana and 41.6%-63.0% in B. utilis. Moreover, the soil carbon to nitrogen ratio, mean annual temperature and soil pH were identified as a key influencing factor for f_fungi. This study provides perspectives and insights for understanding N acquisition strategies and their influencing factors in ectomycorrhizal trees within natural ecosystems.

Key words: nitrogen stable isotope, ectomycorrhizal tree, mycelia pathway, nitrogen uptake, subalpine forest

CHEN Miao, CHEN Jian, LIU Shun, XU Ge-Xi, FENG Qiu-Hong, SHI Zuo-Min. Contribution and influencing factors of ectomycorrhizal fungi to nitrogen acquisition for Abies fargesii var. faxoniana and Betula utilis on the eastern Qingzang Plateau[J]. Chin J Plant Ecol, 2026, 50(3): 731-741.

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URL: https://www.plant-ecology.com/EN/10.17521/cjpe.2025.0252

https://www.plant-ecology.com/EN/Y2026/V50/I3/731

Figures/Tables 7

Fig. 1 Location of the sampling sites in the study area. FTZ, Fengtongzhai; MYL, Miyaluo; SDG, Sandagu; SPG, Songpinggou; WL, Wolong.

Fig. 2 Soil nitrogen (N) concentration and isotopic characteristics and plant nitrogen isotopic characteristics in different forest types (mean ± SE). DON, dissolved organic nitrogen content; TDN, total dissolved nitrogen content. δ15NTDN, the stable nitrogen isotope value of soil total dissolved nitrogen; δ15Nplant, the stable nitrogen isotope value of whole-plant. Different lowercase letters denote significant differences between different forest types at p < 0.05. Different uppercase letters denote significant differences among different forms of N at p < 0.05.

Table 1 Different forms of nitrogen content and nitrogen isotope characteristics in different sites (mean ± SE, n = 4)

森林类型 Forest type	地点 Site	不同形态氮含量 Different forms of nitrogen content (mg·kg^-1)				氮同位素特征 Nitrogen isotope characteristics (‰)
森林类型 Forest type	地点 Site	NH₄⁺-N	NO₃^--N	DON	TDN	δ¹⁵N_TDN	δ¹⁵N_plant
岷江冷杉林 Abies fargesii var. faxoniana forest	WL	13.79 ± 2.79^aB	4.89 ± 0.79^aA	49.27 ± 3.12^aA	67.93 ± 4.83^aB	2.72 ± 0.64^aA	-2.51 ± 0.35^aABC
	MYL	27.70 ± 1.50^aA	0.75 ± 0.10^bA	53.95 ± 5.44^aA	82.39 ± 4.17^aAB	3.14 ± 0.62^aA	-2.71 ± 0.37^aBC
	FTZ	24.94 ± 2.62^aA	1.25 ± 0.40^bA	67.71 ± 7.45^aA	93.90 ± 8.55^aA	3.48 ± 0.38^aA	-1.59 ± 0.24^aA
	SDG	12.48 ± 0.41^aB	0.80 ± 0.17^bA	63.28 ± 8.13^aA	76.54 ± 7.93^aAB	0.93 ± 0.38^bB	-2.07 ± 0.04^bAB
	SPG	6.72 ± 1.01^aC	3.35 ± 0.97^aA	52.54 ± 3.58^aA	62.60 ± 4.05^aB	3.16 ± 0.59^aA	-3.27 ± 0.45^aC
糙皮桦林 Betula utilis forest	WL	9.09 ± 2.63^aBC	8.20 ± 1.79^aB	32.82 ± 6.16^bC	50.10 ± 7.95^bB	2.37 ± 0.14^aAB	-1.35 ± 0.60^aA
	MYL	27.42 ± 1.30^aA	5.51 ± 0.79^aB	55.28 ± 4.23^aAB	88.20 ± 3.16^aA	1.53 ± 0.60^aB	-2.52 ± 0.22^aBC
	FTZ	14.18 ± 1.52^bB	10.73 ± 3.15^aAB	72.56 ± 8.35^aA	97.47 ± 5.70^aA	3.01 ± 0.61^aAB	-1.90 ± 0.43^aAB
	SDG	13.97 ± 2.64^aB	13.63 ± 2.59^aA	51.76 ± 9.51^aB	79.35 ± 14.57^aA	2.42 ± 0.42^aAB	-3.21 ± 0.16^aC
	SPG	4.93 ± 0.71^aC	5.49 ± 1.33^aB	26.17 ± 5.96^bC	36.58 ± 6.75^bB	3.53 ± 0.77^aA	-1.75 ± 0.20^bAB

Fig. 3 Contributions of root pathway and mycelia pathway to Abies fargesii var. faxonian and Betula utilis nitrogen acquisition (mean ± SE). FTZ, Fengtongzhai; MYL, Miyaluo; SDG, Sandagu; SPG, Songpinggou; WL, Wolong. Different lowercase letters denote significant differences between different nitrogen (N) uptake pathways in a given site at p < 0.05. Different uppercase letters denote significant differences among different sites in a given forest type at p < 0.05.

Fig. 4 Difference in ffungi between Abies fargesii var. faxoniana and Betula utilis at the same site (mean ± SE). ffungi, the contribution rate of the mycelia pathway to tree nitrogen acquisition. FTZ, Fengtongzhai; MYL, Miyaluo; SDG, Sandagu; SPG, Songpinggou; WL, Wolong. Different lowercase letters denote significant differences at p < 0.05.

Fig. 5 Relationship between ffungi and climate factors, soil characteristics, and tree age. AGE, tree age; C:N, soil carbon to nitrogen ratio; DON, dissolved organic nitrogen content; ffungi, the contribution rate of the mycelia pathway to tree nitrogen acquisition; MAP, mean annual precipitation; MAT, mean annual air temperature; SBD, soil bulk density; SWC, soil water content.

Fig. 6 Relative importance of explanatory variables to ffungi. AGE, tree age; C:N, soil carbon to nitrogen ratio; DON, dissolved organic nitrogen content; ffungi, the contribution rate of the mycelia pathway to tree nitrogen acquisition; MAP, mean annual precipitation; MAT, mean annual air temperature; SBD, soil bulk density; SWC, soil water content.

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