PARENT SESSION
Poster Session # 15: Plant Ecology.
Wednesday, August 6 Presentation from 5:00 PM to 6:30 PM. SITCC Exhibit Hall B.
Fine root distribution and life-span in three co-occurring Great Basin life forms.
Peek, Michael*,1, Leffler, Josh1, Ivans, Carolyn1, 2, Ryel, Ron1, Caldwell, Martyn1, 1 Department of Forest, Range and Wildlife Sciences and The Ecology Center, Logan, UT2 Department of Biological Sciences, Richmond, KY
ABSTRACT- Plant investment below-ground is considerable, particularly in arid environments as evidenced by high root:shoot ratios. Low water and nutrient availability contributes to the large investment in root structures in these systems. Fine roots play a major role in acquiring these essential resources, yet a paucity of information exists on the distribution and longevity of fine roots. Minirhizotrons provide a valuable means of non-destructively examining fine roots over time. We examined fine roots in three co-occuring Great Basin plant species of contrasting life form; the perennial shrub Artemisia tridentata, the perennial grass, Agropyron desertorum and the invasive annual grass Bromus tectorum. Fine root length, diameter and life-span were followed for each species from a depth of 5 cm to 120 cm during the 2001 and 2002 growing seasons. All species exhibited flexibility in fine root length distribution with depth. In 2001, a year of reduced winter precipitation relative to 2002, fine roots were found deeper in the soil profile. In 2001, Bromus had 75% of total root length reach a depth of 45 cm, whereas in 2002, 75% of the root total length only reached a depth of 30 cm. Agropyron and Artemisia showed similar trends with 75 % of total root length reaching a greater depth in 2001 (43 cm and 50 cm, respectively), than in 2002 (35 and 37 cm, respectively). Mean fine root diameter (mm) was not significantly different between the two perennials in either year (∼ 0.26), but fine roots were significantly smaller for the annual (0.21±0.004, 2001; 0.23±0.004, 2002). Surprisingly, mean diameter did not positively correlate with fine root life-span. Artemisia, with the largest fine root diameters, had had shorter life spans in both years than the two grasses. Interestingly, there was apparent persistence of fine roots after seed set and shoot senescence of the annual, Bromus tectorum. Flexible rooting distributions combined with persistent fine roots may facilitate water and nutrient acquisition in these nutrient-poor environments.
Key words: bromus tectorum, minirhizotron, artemisia tridentata, agropyron desertorum