Nitrogen and carbon isotopes in Finnish (Kilpisjarvi, Kevo) ectomycorrhizal fungi
We analyzed %C, %N, δ13C, δ15N, and C: N stoichiometry of 12 species of ectomycorrhizal sporocarps of collected from Betula-dominated stands in northern Finland from 1971 to 1983. These were archived specimens originally collected during fieldwork by Esteri Ohenoja and Katriina Bendiksen from the University of Oulu. We hypothesized that functional attributes of ectomycorrhizal fungi such as hydrophobicity of ectomycorrhizae and weather conditions could influence sporocarp δ13C, δ15N, and C: N. Taxa with hydrophobic ectomycorrhizae were higher in δ15N and increased more in δ13C with increasing nitrogen concentration than taxa with hydrophilic ectomycorrhizae, reflecting the uptake of 13C- and 15N-enriched organic N by hydrophobic taxa. Sporocarp δ13C correlated negatively with average daily precipitation and positively with average temperature and the daily temperature range for the three previous weeks. Sporocarp C/N correlated negatively with average daily precipitation for the three previous weeks but also negatively with the daily temperature range 4-6 weeks prior to collection. Sporocarp δ13C also correlated with site aspect, specifically Southness, with sporocarps from more southern-facing locations somewhat higher in δ13C. Similar patterns in sporocarp C/N and δ13C indicated that fungal growth and C dynamics respond rapidly to plant C supply as modulated by climate conditions. Precipitation and temperature variability appeared to affect plant photosynthesis and ectomycorrhizal carbon dynamics similarly. The attached files are: Appendix Methods-1. docx. This is the file describing isotopic analyses and standards used for quality assurance. Appendix 2-Data for regressions.txt. This is the data file used to run stepwise regression analyses. Appendix 3.xlsx. This shows the stepwise regression used for d13C (carbon isotopes) analysis. Appendix 6.xlsx. This shows the stepwise regression used for d15N (nitrogen isotopes) analysis. Appendix 7.xlsx. This shows the stepwise regression used for the natural log of C/N analysis.
Steps to reproduce
Stable isotope analyses were carried out at the University of New Hampshire. Procedures and standards are given in Data analysis was done in JMP13.0. After stepwise forward regression analysis on each of the three parameters (d13C, d15N, and log(e) of C/N), the minimum value of the Bayesian Information Criterion (BIC) was used to determine the model presented in full.