You are here:
LIFETIME AND TEMPORAL OCCURRENCE OF ECTOMYCORRHIZAE ON PONDEROSA PINE (PINUS PONDEROSA LAWS.) SEEDLINGS GROWN UNDER VARIED ATMOSPHERIC CO-2 AND NITROGEN LEVELS
Citation:
Rygiewicz, P., M. Johnson, L. M. Ganio, D. Tingey, AND M. J. Storm. LIFETIME AND TEMPORAL OCCURRENCE OF ECTOMYCORRHIZAE ON PONDEROSA PINE (PINUS PONDEROSA LAWS.) SEEDLINGS GROWN UNDER VARIED ATMOSPHERIC CO-2 AND NITROGEN LEVELS. Plant and Soil 189(2):275-287, (1997).
Description:
Climate change(elevated atmospheric CO-2,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 CO-2(ambient,525 and 700 mu-mol CO-2 mol-1)and three levels of annual nitrogen additions(0,100 and 200 kg N ha-1)in open-top chanbers.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 CO-2 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 CO-2 treatment compared with the other CO-2 treatments,and(2)intermediate N addition treatment compared with the other N addition treatments.A survival analysis on the entire 18 months 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 CO-2 treatments.