Nitrogen addition alleviates negative effects of drought on root growth but aggravates them on leaf growth of Moso bamboo (Phyllostachys edulis) seedlings

Forest ecosystems are increasingly susceptible to droughts and nitrogen (N) deposition. However, the effects of N addition on the growth of bamboo under drought stress remain unclear. This study conducted a comprehensive factorial experiment to investigate the combined effects of drought and N addition on the growth of Moso bamboo ( Phyllostachys edulis ) seedlings. Six treatment combinations were established: 0 mg·kg −1 N with 80%–85% field capacity (FC) soil moisture, 0 mg·kg −1 N with 50%–55% FC, 0 mg·kg −1 N with 30%–35% FC, 100 mg·kg −1 N with 80%–85% FC, 100 mg·kg −1 N with 50%–55% FC, and 100 mg·kg −1 N with 30%–35% FC. The results revealed that drought altered the soil microbial community structure and significantly reduced the biomass of Moso bamboo seedlings. Notably, N addition mitigated the adverse effects of drought on bamboo growth in general. Specifically, N addition alleviated the negative effects of drought on root biomass but aggravated them on leaf biomass of Moso bamboo seedlings, and with the intensification of drought stress, this effect was weakened. Furthermore, sucrose and urease exerted dominant and direct influences on the total biomass. The results underscore the pivotal role of N in facilitating plant drought tolerance, suggesting that the interplay between drought and N addition in plant growth should be considered in the context of changing environmental conditions, and offering novel perspectives on sustainable management strategies for bamboo forests.