Document: WEI-3-31-19

Fine root turnover and mycorrhizal morphotypes in loblolly pine.

YANG, W.*, A.K.DUNBAR-WALLIS and M.A.TOPA

Boyce Thompson Institute for Plant Research, Ithaca, NY, USA ¹

Abstract:
Loblolly pine (Pinus taeda L.) is the most widely-planted tree species in the Atlantic Coastal Plain. Since as much as 70% of total fixed carbon can be used for fine root system (roots + mycorrhizae) production and maintenance in pine forests, genetic differences in fine root production and turnover may contribute to aboveground yield variation among fast- and slow-growing families of loblolly pine. Over a two period (1998-1999), we used minirhizotron technology to investigate fine root production and turnover in four families of 6-year-old loblolly pine in Scotland County, NC, under fertilized and ambient soil conditions. A total of 144 minirhizotron tubes were installed, and root images were recorded on a monthly basis. Data analyses indicated an interaction between family and fertilizer treatments for total fine root length and total fine root number. Fertilization increased total root length in a slow-growing family but decreased total root length in a faster-growing family. Total root number decreased in the fertilizer treatment in the two fastest-growing families, but increased in the two slowest-growing families. Because ectomycorrhizae are significant carbon sinks in pine root systems and more than 90% of short roots in these loblolly pine families were colonized, ectomycorrhizal short roots (clusters) were classified into 9 different morphotypes based mainly on color and the number of mycorrhizal root tips. The persistence of each morphotype was determined by the number of that morphotype divided by total root length. No treatment and family interactions were found. Fertilizer treatment decreased the number of mycorrhizal clusters per unit root length. Dark and brown morphotypes were dominant mycorrhizal morphotypes among all the families. Our results suggest possible genetic differences and treatment effects on root system carbon demands of loblolly pine.

Keywords: Loblolly pine, fine root turnover, mycorrhizae

This abstract is being presented at: 3:30 PM in session:
MYCORRHIZAL FUNGI