Diversity and enzyme activity of ectomycorrhizal fungal communities following nitrogen fertilization in an urban-adjacent pine plantation

Rapid economic development and accelerated urbanization in China has resulted in widespread atmospheric nitrogen (N) deposition. One consequence of N deposition is the altera-tion of mycorrhizal symbioses that are critical for plant resource acquisition (nitrogen, N, phos-phorus, P, water). In this study, we characterized the diversity, composition, and functioning of ectomycorrhizal (ECM) fungal communities in an urban-adjacent Pinus elliottii plantation under ambient N deposition (~24 kg N ha^-1 year^-1), and following N fertilization (low N, 50 kg N ha^-1 year^-1; high N, 300 kg N ha^-1 year^-1). ECM functioning was expressed as the potential activities of extracellular enzymes required for organic N (protease), P (phosphomonoesterase), and recalci-trant polymers (phenol oxidase). Despite high ambient N deposition, ECM community composi-tion shifted under experimental N fertilization, and those changes were linked to disparate levels of soil minerals (P, K) and organic matter (but not N), a decline in acid phosphatase (AP), and an in-crease in phenol oxidase (PO) potential activities. Based on enzyme stoichiometry, medium-smooth exploration type ECM species invested more in C acquisition (PO) relative to P (AP) following high N fertilization than other exploration types. ECM species with hydrophilic mantles also showed higher enzymatic PO:AP ratios than taxa with hydrophobic mantles. Our findings add to the ac-cumulating evidence that shifts in ECM community composition and taxa specialized in organic C, N, and P degradation could modulate the soil nutrient cycling in forests exposed to chronic ele-vated N input.