Lifetime and temporal occurrence of ectomycorrhizae on ponderosa pine (Pinus ponderosa Laws.) seedlings grown under varied atmospheric CO₂ and nitrogen levels

• Published in: Plant and soil Vol. 189; no. 2; pp. 275 - 287
• Main Authors: Rygiewicz, Paul T., Johnson, Mark G., Ganio, Lisa M., Tingey, David T., Storm, Marjorie J.
• Format: Journal Article
• Language: English
• Published: Dordrecht Kluwer Academic Publishers 01.02.1997; Springer; Springer Nature B.V
• Subjects: Agronomy. Soil science and plant productions; Atmospherics; Biological and medical sciences; Carbon dioxide; Economic plant physiology; Forest soils; Fundamental and applied biological sciences. Psychology; Fungi; Mycorrhizae; Pine trees; Plant roots; Plants; Root tips; Seedlings; Soil ecology; Symbiosis (nodules, symbiotic nitrogen fixation, mycorrhiza...); Nitrogen fertilization; Symbionte; Life history; Open top chamber; Minirhizotron; Root; Plant juvenile growth stage; Carbon dioxide; Basidiomycetes; Source sink relationship; Carbon balance; Fungi; Medium enrichment; Ambient air concentration; Lifetime; Pinus ponderosa; Softwood forest tree; Gymnospermae; Mycorrhiza; Ectomycorrhiza; Coniferales; Spermatophyta; Thallophyta
• ISSN: 0032-079X; 1573-5036
• DOI: 10.1023/A:1004210709108

Climate change (elevated atmospheric CO₂, and altered air temperatures, precipitation amounts and seasonal patterns) may affect ecosystem processes by altering carbon allocation in plants, and carbon flux from plants to soil. Mycorrhizal fungi, as carbon sinks, are among the first soil biota to receive carbon from plants, and thereby influence carbon release from plants to soil. One step in this carbon release is via fine root and mycorrhizal turnover. It is necessary to know the lifetime and temporal occurrence of roots and mycorrhizae to determine the capacity of the soil ecosystem to sequester carbon assimilated aboveground. In this study, ponderosa pine (Pinus ponderosa Laws) seedlings were grown under three levels of atmospheric CO₂ (ambient, 525 and 700 µmol CO₂ mol⁻¹) and three levels of annual nitrogen additions (0,100 and 200 kg N ha⁻¹) in open-top chambers. At a two-month frequency during 18 months, we observed ectomycorrhizal root tips observed using minirhizotron tubes and camera. The numbers of new mycorrhizal root tips, the numbers of tips that disappeared between two consecutive recording events, and the standing crop of tips at each event were determined. There were more mycorrhizal tips of all three types seen during the summer compared with other times of the year. When only the standing crop of mycorrhizal tips was considered, effects of the CO₂ and N addition treatments on carbon allocation to mycorrhizal tips was weakly evident. However, when the three types of tips were considered collectively, tips numbers flux of carbon through mycorrhizae was greatest in the: (1) high CO₂ treatment compared with the other CO₂ treatments, and (2) intermediate N addition treatment compared with the other N addition treatments. A survival analysis on the entire 18 month cohort of tips was done to calculate the median lifetime of the mycorrhizal root tips. Average median lifetime of the mycorrhizal tips was 139 days and was not affected by nitrogen and CO₂ treatments.