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PATTERNS OF ROOT GROWTH, TURNOVER, AND DISTRIBUTION IN DIFFERENT AGED PONDEROSA PINE STANDS
Andersen, C P., D L. Phillips, P T. Rygiewicz, AND M. J. Storm. PATTERNS OF ROOT GROWTH, TURNOVER, AND DISTRIBUTION IN DIFFERENT AGED PONDEROSA PINE STANDS. Presented at Linking the Complexity of Forest Canopies to Ecosystem and Landscape Function, IUFRO Canopy Processes, Corvallis, OR, July 16-17, 2001.
The objectives of this study are to examine the spatial distribution of roots in relation to canopy size and tree distribution, and to determine if rates of fine root production and turnover are similar in the different aged stands. During the fall of 1998, 54 clear plexiglass tubes were installed at the Metolius old site (OS) at the base of 60 and 250+ year old trees, and 32 were installed at the young site (YS) at the base of 20+ year old trees. Maximum depth of each tube is approximately 50-65 cm depending on soil obstructions. Root video images were collected at 1.5 cm intervals along the top surface of each tube 6-7 times from May to November each year during 1999, 2000 and are images are being collected in 2001.
Analysis of images through July 2000 showed that estimates of standing crop were nearly twice as great at the young site compared to the two tree age classes at the old site. Standing crop at the young site was approximately 558 g m-2 (to 50 cm depth), while at the old site standing crop estimates averaged less than 300 g m-2. Both fine root production and turnover were higher at the young site than old site during from April through July, 2000. Both sites exhibited fairly dynamic fine root systems with >100% turnover of the initial standing crop within the first growing season, and production of enough new fine roots to replace the losses and increase the standing crop. Estimates of turnover were relatively constant from December to April at both sites, but turnover and production both increased around all three age classes between May and June, 2000. The steady increase in standing crop in all three areas suggests either that roots have not fully occupied the zone around the minirhizotron tubes, or that conditions during 1999 and 2000 were optimal for root growth at both sites.