The role of abiotic factors on belowground meristem dynamics and tiller initiation in tallgrass prairie ecosystems

Background/Question/Methods

Belowground populations of meristems play a key role in the population dynamics of aboveground tillers in tallgrass prairie ecosystems. Having a sound understanding of the environmental cues that regulate bud bank dynamics is essential to predicting rangeland responses to environmental change. The purpose of our study was to assess the role of nitrogen, light availability and spectral quality (R:FR ratio) as cues for the outgrowth of dormant buds  and tiller emergence in three C₄ native perennial grass species (Andropogon gerardii, Schizachyrium scoparium, Panicum virgatum) and three C₃ native perennial grasses ( Koeleria macrantha, Elymus canadensis, and Dicanthelium oligosanthes). Perennating organs from these grasses were placed into vermiculite and maintained in controlled environmental chambers under varying light and nitrogen conditions at optimal temperatures for four to six weeks. At the conclusion of the study period, plants were washed and the number of live buds and live tillers were counted and recorded. Data were analyzed using ANOVA and a Fisher LSD multiple comparison test (p < 0.05).

Results/Conclusions

We observed strong species-specific responses to nitrogen availability, light quantity, and light spectral quality. Some species responded to the presence or absence of light, while others responded to spectral quality. For example, reduced R:FR light ratio and low nitrogen stimulated release of buds from dormancy and tiller initiation in A. gerardii, but maintained bud dormancy in S. scoparium and P. virgatum.  Among the C₃ grasses, reduced R:FR light ratios maintained bud dormancy in E. canadensis but stimulated bud release and tiller initiation in D. oligosanthes. However, low nitrogen coupled with increased light availability stimulated the release of buds into new tillers in all three species of C₃ grasses. Significant differences were observed between functional groups for each of the environmental cues tested. These species-specific responses to environmental cues may have important impacts on plant community composition in response to environmental change. Our results indicate alterations in nitrogen or light availability may affect plant species composition, relative abundance, and diversity, rather than shifts among functional groups.