Prairie restoration for conservation purposes and ecosystem services has been increasing over the last decade, and more recently, prairie grasses are being investigated as a potential biofuel crop to provide environmental as well as economic value. Prairie grasses are planted in a variety of environmental settings, from fairly rich agricultural lands to lower fertility sites, and site conditions may influence the choice of appropriate plant materials. Both local seed collected from wildlands and commercially propagated seed have been used in restoration, but these two population sources have experienced different selective pressures. In a common garden study comparing the growth and reproductive investment of cultivated and wild-collected populations of Andropogon gerardii on two soil types, there was a significant interaction between soil type and population source. On loamy soils, cultivated populations grew larger and produced more inflorescences than wild-collected populations, but the difference was diminished on sandy soils. To investigate the mechanism behind soil type effects, we conducted two greenhouse experiments. In a nutrient addition experiment, individually potted plants were given weekly additions of N, P, and K or were unfertilized controls. In a soil moisture experiment, two plants from two different populations were planted in one pot, and three watering levels were applied. We predicted that cultivated populations would be more responsive than wild-collected populations to increases in either nutrients or moisture, or potentially both.
Results/Conclusions
In response to nutrient additions, two populations, one cultivated and one wild-collected, showed significant increases in aboveground biomass compared to control plants. In the soil moisture experiment, cultivars had greater total biomass than wild-collected populations. In planned comparisons, cultivars had significantly greater biomass than wild-collected populations in the low and high water treatments, but the two groups had equal biomass in the intermediate water treatment. A competitive effect was also demonstrated: wild-collected plants were more affected by competition when planted with cultivars than with another wild-collected plant. Different populations may have adapted to the availability of particular resources based on the environmental conditions in which they evolved, whether under natural or artificial selection.While nutrients and water did mediate plant responses, in this setting the genetic characteristics of the plants seemed to be the most important factor, such that cultivars tended to be the most productive in multiple environments. High biomass production is an advantage for biofuel production; however, in a restoration setting, these cultivars may be detrimental to biodiversity due to their competitive effects.
