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FINE ROOT TURNOVER IN PONDEROSA PINE STANDS OF DIFFERENT AGES: FIRST-YEAR RESULTS
Citation:
Andersen, C P., D L. Phillips, P T. Rygiewicz, AND M. J. Storm. FINE ROOT TURNOVER IN PONDEROSA PINE STANDS OF DIFFERENT AGES: FIRST-YEAR RESULTS. Presented at Age-Related Change in Structure and Function of Trees and Forests in the Pacific Northwest: A Synthesis of Research, Corvallis, OR, October 19, 2000.
Description:
Root minirhizotron tubs were installed in two ponderosa pine (Pinus ponderosa Laws.) Stands of different ages to examine patterns of root growth and death. The old-growth site (OS) consists of a mixture of old (>250 years) and young trees (ca.45 yrs)< and is located near clamp Sherman, OR in the Metolius Research Natural Area (RNA). A second research area is located approximately we km Se of the Metolius RNA and consists of naturally regenerated 20 yr old trees (Young Site, YS). During the fall of 1998, 54 clear plexiglass tubes were installed at the OS and 32 were installed at the YS to a depth of approximately 65 cm. The objectives were to examine the spatial distribution in relation to canopy size and tree distribution, and to determine if rates of fine root production and turnover were similar in the different aged stands.
Video images were collected monthly at 1.5 cm intervals along the top surface of each tube starting in June, 1999, approximately 88 months after installation, and digitized to follow individual roots. Preliminary results from the first growing season of image collection (June through October) showed estimates of standing crop were similar at both sites and increased 80 g m-2 to 120 g m-2 over that period. Both fine root production and turnover were slightly higher at the OS than YS. Both sites exhibited fairly dynamic fine root systems with >100% turnover of the initial standing crop within the growing season, and production of enough new fine roots to replace the losses and increase the standing crop. We anticipate that over winter, turnover will outweigh production and reduce fine root standing crop once again to a minimum before the next growing season. Data from subsequent growing seasons should verify whether this annual pattern exists, and the degree to which it is modified by year-to-year variability in water availability, plant C balance, overwinter mortality, and other factors.