Productivity and diversity of annually harvested reconstructed prairie communities

Abstract

1. Biofuel production from cellulosic feedstocks may increase during the next century.To be sustainable, this production should protect environmental quality and biodiversity. Fertilized mixed-species prairie can deliver substantial quantities of cellulosic ethanol per unit land area with minimal losses of NO 3 -N in drainage water, but the long-term maintenance of biodiversity in such systems has been uncertain.2. We report how nitrogen, phosphorus, and potassium fertilizer application, precipitation, and time affected the species composition and productivity of reconstructed prairie communities harvested annually as biofuel feedstocks over a 9-year period.3. Results indicated that both precipitation and fertilizer application drove aboveground biomass production, with the greatest response to fertilizer occurring in wetter than average years. Fertilization reduced species richness, but increased species evenness. Consequently, Simpson's diversity index did not differ between the fertilized and unfertilized communities, though it declined in both communities over time. 4.A total of 59 plant species was recorded, with eight of them explaining most of the differences in vegetation cover between the fertilized and unfertilized treatments.After 9 years, the high fertility community was dominated by the C4 grass Andropogon gerardii, the C3 grass Elymus canadensis, and the non-leguminous forbs Heliopsis helianthoides, Helianthus maximiliani, and Monarda fistulosa, whereas the low fertility community was dominated by the C4 grasses A. gerardii and Sorghastrum nutans, the C3 grass E. canadensis, and the non-leguminous forb M.fistulosa. Fertilization increased the abundance of flowering forbs available to pollinators in the early, middle and late portions of the growing season. Synthesis and applications.Results of our study suggest that maintenance of reasonably high levels of productivity and biodiversity are possible in fertilized prairie communities harvested annually for bioenergy, with plant cover more evenly distributed among different functional groups. In the future, if policy and markets favour biofuels and better delivery of ecosystem services from harvested land, prairie-based feedstocks could become part of a renewable energy portfolio that fosters biodiversity and contributes to the provision of floral resources for pollinators. K E Y W O R D Sbiofuel, cellulosic ethanol, community dynamics, prairie vegetation, productivity, soil fertility, species diversity, succession | 331Journal of Applied Ecology KORDBACHEH Et Al.

Helianthus maximiliani and species fine‐scale spatial pattern affect diversity interactions in reconstructed tallgrass prairies

“…As in other studies (Dickson & Busby, ; Kordbacheh, Jarchow, English, & Liebman, ; Nemec, Allen, Helzer, & Wedin, ; Seahra et al, ), a productive Heliantheae forb initially dominated our experimental tallgrass prairies reconstructed on a former agricultural field. To address this statistically, we allowed diversity effects in our DI models to differ in H. maximiliani plots and treated these plots with a different variance structure.…”

“…While many studies have demonstrated this effect (Cardinale et al, ; Isbell, Polley, & Wilsey, ; Seahra et al, ), our study is unique in that we quantified specific species contributions to diversity effects. Specifically, we found that including H. maximiliani can enhance diversity effects, albeit it can appear that it outcompetes others based on its initially high biomass production (Dickson & Busby, ; Kordbacheh et al, ; Nemec et al, ). Second, because species broad functional identities (cool‐season, warm‐season, forb, legume) were not informative, managers may best approach planning for tallgrass prairie diversity effects by keeping individual species characteristics, as opposed to their broad functional identities, in mind.…”

“…In the context of the SPaCE experiment, we previously reported that this species contributed to strong selection effects in the first and second growing seasons (McKenna & Yurkonis, ). In general, the early dominance of H. maximiliani in reconstructed grasslands has been correlatively attributed to strong competitive and potentially allelopathic effects on co‐occurring species (Dickson & Busby, ; Kordbacheh et al, ; Macías, Torres, JoséM, Molinllo, & Castellano, ; Nemec et al, ). However, evidence of a direct effect on other species is lacking in the literature.…”

Mechanisms underlying limited soil carbon gains in perennial and cover‐cropped bioenergy systems revealed by stable isotopes

“…The relative increase of C 3 plants observed in the fertilized prairie is consistent with previous findings elsewhere and may be linked to the increased N requirement (i.e., lower C/N ratio and N‐use efficiency) of C 3 versus C 4 plants (Wedin & Tilman, ). Averaged over the first 9 years of the study, the Pr treatment had 23% C 3 versus 77% C 4 cover, while PrF had 39% C 3 and 61% C 4 cover (Kordbacheh et al, ). This difference in plant cover was closely reflected in the δ 13 C values of respiration in 0–25 cm soil, where C 3 contributions to CO 2 were estimated at 20% and 47% in Pr and PrF, respectively (Figure a).…”

“…All the corn treatments received a consistent rate of N fertilizer (urea ammonium nitrate) at the time of corn planting, but variable amounts of fertilizer were side‐dressed into each corn treatment after emergence based on the results of a late‐spring nitrate test. Thus, nitrogen addition in all the corn treatments ranged from 105 to 221 kg N ha −1 year −1 (Jarchow et al, ; Kordbacheh et al, ).…”