ABSTRACT
We conducted a short-term field hydroponic 15N labeling experiment to study the effects of different nitrogen (N) addition treatment on the N uptake preference and rate of plant fine roots in a temperate old growth forest in 2018. The results indicated that the N preference of dominant tree species for different N chemical forms was not influenced by the N addition, with the N acquisition pattern being ammonium > nitrate > glycine. However, N addition altered the plant's N uptake rates. Under low N treatment, the uptake rates of glycine for three target tree species significantly increased. Both low and medium N additions significantly enhanced the NH4–N uptake rate, but had little impact on the NO3–N uptake rate. Conversely, high N addition exerted negative effects on NO3–N and NH4–N uptake rate. Different tree species may flexibly adapt to new environmental conditions by adapting to their root morphology and the relationship between plant growth and N uptake. N addition has pronounced effects on N uptake rate and root morphology traits of dominant tree species. Overall, this study contributes to a deeper understanding of the response of N uptake patterns in temperate forests to long-term N addition.
Acknowledgments
We gratefully acknowledge Professor Xingliang Xu from the Institute of Geographic Sciences and Natural Resource Research, Chinese Academy of Science for his advice about field experiment design and Professor Yunting Fang from the Institute of Applied Ecology, Chinese Academy of Science for their comments and suggestions on an earlier draft of this manuscript.
Disclosure statement
No potential conflict of interest was reported by the author(s).
Availability of data and material
Data are available from the corresponding author on reasonable request.
Contributions of all authors
QW and GL designed the study, awarded funding, supervised data collection and edited the manuscript. YX, GL, QW, GY and WS contributed to the whole manuscript preparation and design and wrote the main manuscript text. YX, GL, QW, GY and WS prepared all figures. GL, YX, WS, GY and QW prepared the field experiments, prepared the tables and collected the literature. All authors reviewed the manuscript.