Effects of root interactions on Wyoming big sagebrush root growth

Background/Question/Methods

Root interactions can involve sophisticated behaviors including detection and reaction to interspecific and intraspecific root systems by chemical signaling. Non-resource mediated root interactions may have negative effects on resource acquisition by seedlings, particularly in resource poor ecosystems. For example, requirements for water by Artemisia tridentata ssp. wyomingensis are much more immediate than other species because it lacks stored energy in its seed. We studied effects of non-resource mediated root interactions on big sagebrush seedling establishment using root observation chambers and activated charcoal (AC). Chambers were filled with pasteurized river sand and placed in a greenhouse under natural light and temperatures ranging from 20-40°C. Finely ground AC at a ratio of 20 mL AC: 1 L sand was mixed into the sand of half the chambers. One individual of Wyoming big sagebrush was grown in root observation chambers with one of four test species:  Wyoming big sagebrush, cheatgrass (Bromus tectorum) bluebunch wheatgrass (Pseudoroegneria spicata), and desert wheatgrass (Agropyron desertorum). Chambers were watered 3 times/week and fertilized once a week. To control for the effect of AC, sagebrush seedlings were grown alone with and without AC. Root elongation of sagebrush seedlings was measured every two days.

Results/Conclusions

Preliminary results showed that activated charcoal (AC) had no effect on total sagebrush root growth in the control treatment (p = 0.14). There is an indication that the effects of competition with cheatgrass, in comparison to conspecifics, may be ameliorated with AC. Sagebrush roots grew 5-10 mm/day when grown with cheatgrass and 8-14 mm/day when grown with conspecifics, in the absence of AC (p = 0.09). Sagebrush root growth was similar when grown with cheatgrass (8-14 mm/day) or conspecifics (8-15 mm/day), with the addition of AC (p = 0.81). AC may also decrease sagebrush root growth rate (p = 0.06) when grown in competition with desert wheatgrass (6-11 mm/day with AC; 9-15 mm/day without AC). This result suggests potential chemical use by Wyoming big sagebrush in root competition that is species-specific. Further investigations to elucidate these findings are ongoing, including studying effects of competition and AC treatments on above- and below-ground biomass.