Plasticity in nitrogen form uptake and preference in response to long-term nitrogen addition of the main tree species in a temperate old growth forest

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.

KEYWORDS:

• Nitrogen addition
• nitrogen uptake rate
• ¹⁵N Labeling experiment
• root morphology
• temperate old growth forest

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.

Additional information

Funding

This research was supported by grants from the National Natural Science Foundation of China (42230703, 42377477).