Agricultural intensification continues to diminish many ecosystem services in the North American Corn Belt. Conservation programs may be able to combat these losses more efficiently by developing initiatives that attempt to balance multiple ecological benefits. In this study, we examine how seed mix design and first year management influence three ecosystem services commonly provided by tallgrass prairie reconstructions (erosion control, weed resistance, and pollinator resources). We established research plots with three seed mixes, with and without first year mowing. The grass‐dominated “Economy” mix had 21 species and a 3:1 grass‐to‐forb seeding ratio. The forb‐dominated “Pollinator” mix had 38 species and a 1:3 grass‐to‐forb seeding ratio. The grass:forb balanced “Diversity” mix, which was designed to resemble regional prairie remnants, had 71 species and a 1:1 grass‐to‐forb ratio. To assess ecosystem services, we measured native stem density, cover, inflorescence production, and floral richness from 2015 to 2018. The Economy mix had high native cover and stem density, but produced few inflorescences and had low floral richness. The Pollinator mix had high inflorescence production and floral richness, but also had high bare ground and weed cover. The Diversity mix had high inflorescence production and floral richness (comparable to the Pollinator mix) and high native cover and stem density (comparable to the Economy mix). First year mowing accelerated native plant establishment and inflorescence production, enhancing the provisioning of ecosystem services during the early stages of a reconstruction. Our results indicate that prairie reconstructions with thoughtfully designed seed mixes can effectively address multiple conservation challenges.
The conversion of tallgrass prairie to agriculture has negatively affected provisioning of ecosystem services. Successful restoration of ecosystem services could depend on management decisions applied during revegetation projects. We examined the effects of three management decisions (seed mix design, planting time, and first‐year mowing) on targeted ecosystem services (erosion control, weed resistance, and pollinator resources). We tested three seed mixes of varying diversity and grass‐to‐forb seeding ratios: Economy mix (21 species, 3:1 grass:forb), Pollinator mix (38 species, 1:3), and Diversity mix (71 species, 1:1). We established plots at two planting times (dormant‐season and spring) with or without first‐year mowing. To assess ecosystem services, we measured stem density, canopy cover, and floral density and richness of sown species in the second year after planting. The Economy mix had the highest stem density and cover but lowest floral density and richness. The Pollinator mix had the lowest stem density and cover but highest floral density. The Diversity mix had comparable stem density and cover to the Economy mix and comparable floral density and richness to the Pollinator mix. Mowing accelerated native plant establishment in all seed mixes. Dormant‐season planting improved establishment of spring and fall forbs and favored cool‐season graminoids over warm‐season grasses. All three management decisions influenced ecosystem outcomes, and comparison to a previous study revealed these effects to be robust to variation in site and climatic conditions. We recommend a diverse, balanced seed mix design, first‐year mowing, and dormant‐season planting to improve multifunctionality of conservation projects.
High‐diversity mixtures of perennial tallgrass prairie vegetation could be useful biomass feedstocks for marginal farmland in the Midwestern United States. These agroenergy crops can help meet cellulosic agrofuel targets while also enhancing other ecosystem services on the landscape. One proposed advantage of high‐diversity prairie biomass feedstocks is that they should become nutrient limited at a slower rate than monoculture feedstocks. In this study, we examine rates of soil nutrient depletion and the physiology and performance of a focal species (switchgrass, Panicum virgatum L.) in four prairie agroenergy feedstocks with different species composition and diversity. The feedstocks in this study were a 1‐species switchgrass monoculture, a 5‐species mixture of C4 grasses, a 16‐species mixture of C3 and C4 grasses, forbs, and legumes, and a 32‐species mixture of C3 and C4 grasses, forbs, legumes, and sedges. To assess feedstock effects on soil, we measured changes in soil N/P/K over a five‐year period. We also performed a greenhouse study, in which we grew switchgrass plants in field soil conditioned by each feedstock. To assess feedstock effects on plant function, we measured four physiological traits (photosynthetic rate, chlorophyll concentration, leaf florescence, leaf N concentration) on switchgrass plants within each feedstock in the field. In the soil analysis, we found that the 5‐species feedstock displayed higher rates of soil N/P/K depletion than other feedstocks. In the greenhouse analysis, we found that switchgrass plants grown in soil conditioned by the 5‐species feedstock were smaller than plants grown in soil conditioned by other feedstocks. In the physiological analysis, we found that switchgrass plants in the 5‐species feedstock had lower leaf N, photosynthesis, chlorophyll concentration, and higher florescence than switchgrass plants growing in other feedstocks. Collectively, our results show that prairie agroenergy feedstocks with different species composition and diversity have different rates of soil nutrient depletion, which influences the physiology and performance of plants within the feedstock. These differences would ultimately impact the ecosystem services (e.g., biomass production, need for fertilizer) that these prairie agroenergy feedstocks provide.
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