Tallgrass Prairie Center: The Weeds of CRP Polinator Habitat

An investigation of weed species and their impact on pollinator habitat

Assessing Productivity in Prairie Biomass Feedstocks with Different Levels of Diversity

High-diversity mixtures of tallgrass prairie vegetation provide many ecosystem services and could be effective biomass feedstocks for marginal farmland in Iowa. In this study, we measured productivity in four prairie biomass feedstocks with different diversity: 1, 5, 16, and 32 species. Each feedstock was replicated four times on three soil types (48 research plots, 0.33 – 0.56 ha each). For the past seven years, we have monitored productivity in these feedstocks by harvesting tissue from randomly selected quadrats. In addition to continuing the productivity survey, we examined the efficacy of remote sensing (NDVI) and leaf area index (LAI) imaging for estimating productivity in 2015 and 2016. Across soil types, the 1-, 16-, and 32-species feedstocks are equally productive and outperform the 5-species feedstock. Regions with high LAI correspond with regions of high productivity at the plot- and quadrat-level. NDVI does not correspond with productivity at the plot- or quadrat-level. The low predictive power of our regressions suggests that neither metric is a suitable replacement for annual biomass harvest

The fifth leaf and spike organs of barley (Hordeum vulgare L.) display different physiological and metabolic responses to drought stress

Background: Photosynthetic organs of the cereal spike (ear) provide assimilate for grain filling, but their response to drought is poorly understood. In this study, we characterized the drought response of individual organs of the barley spike (awn, lemma, and palea) and compared them with a vegetative organ (fifth leaf). Understanding differences in physiological and metabolic responses between the leaf and spike organs during drought can help us develop high yielding cultivars for environments where terminal drought is prevalent. Results: We exposed barley plants to drought by withholding water for 4 days at the grain filling stage and compared changes in: (1) relative water content (RWC), (2) osmotic potential (Ψs), (3) osmotic adjustment (OA), (4) gas exchange, and (5) metabolite content between organs. Drought reduced RWC and Ψs in all four organs, but the decrease in RWC was greater and there was a smaller change in Ψs in the fifth leaf than the spike organs. We detected evidence of OA in the awn, lemma, and palea, but not in the fifth leaf. Rates of gas exchange declined more rapidly in the fifth leaf than awn during drought. We identified 18 metabolites but, only ten metabolites accumulated significantly during drought in one or more organs. Among these, proline accumulated in all organs during drought while accumulation of the other metabolites varied between organs. This may suggest that each organ in the same plant uses a different set of osmolytes for drought resistance. Conclusions: Our results suggest that photosynthetic organs of the barley spike maintain higher water content, greater osmotic adjustment, and higher rates of gas exchange than the leaf during drought. Keywords: Barley, Awn, Leaf, Lemma, Palea, Drought, Water status, Gas exchange, Metabolite

Productivity and resistance to weed invasion in four prairie biomass feedstocks with different diversity

High-diversity mixtures of native tallgrass prairie vegetation should be effective biomass feedstocks because of their high productivity and low input requirements. These diverse mixtures should also enhance several of the ecosystem services provided by the traditional monoculture feedstocks used for bioenergy. In this study, we compared biomass production, year-to-year variation in biomass production, and resistance to weed invasion in four prairie biomass feedstocks with different diversity: one species – a switchgrass monoculture; five species – a mix of C4 grasses; 16 species – a mix of grasses, forbs, and legumes; and 32 species – a mix of grasses, forbs, legumes, and sedges. Each diversity treatment was replicated four times on three soil types for a total of 48 research plots (0.33–0.56 ha each). We measured biomass production by harvesting all plant material to ground level in ten randomly selected quadrats per plot. Weed biomass was measured as a subset of total biomass. We replicated this design over a five-year period (2010–2014). Across soil types, the one-, 16-, and 32-species treatments produced the same amount of biomass, but the one-species treatment produced significantly more biomass than the five-species treatment. The rank order of our four diversity treatments differed between soil types suggesting that soil type influences treatment productivity. Year-to-year variation in biomass production did not differ between diversity treatments. Weed biomass was higher in the one-species treatment than the five-, 16-, and 32-species treatments. The high productivity and low susceptibility to weed invasion of our 16- and 32-species treatments supports the hypothesis that high-diversity prairie mixtures would be effective biomass feedstocks in the Midwestern United States. The influence of soil type on relative feedstock performance suggests that seed mixes used for biomass should be specifically tailored to site characteristics for maximum productivity and stand success

Species composition influences soil nutrient depletion and plantphysiology in prairie agroenergy feedstocks

High-diversity mixtures of perennial tallgrass prairie vegetation could be useful biomass feed-stocks for marginal farmland in the Midwestern United States. These agroenergy crops can help meet cel-lulosic agrofuel targets while also enhancing other ecosystem services on the landscape. One proposedadvantage of high-diversity prairie biomass feedstocks is that they should become nutrient limited at aslower rate than monoculture feedstocks. In this study, we examine rates of soil nutrient depletion and thephysiology and performance of a focal species (switchgrass,Panicum virgatumL.) in four prairie agroen-ergy feedstocks with different species composition and diversity. The feedstocks in this study were a1-species switchgrass monoculture, a 5-species mixture of C4grasses, a 16-species mixture of C3and C4grasses, forbs, and legumes, and a 32-species mixture of C3and C4grasses, forbs, legumes, and sedges. Toassess feedstock effects on soil, we measured changes in soil N/P/K over afive-year period. We also per-formed a greenhouse study, in which we grew switchgrass plants infield soil conditioned by each feed-stock. To assess feedstock effects on plant function, we measured four physiological traits (photosyntheticrate, chlorophyll concentration, leafflorescence, leaf N concentration) on switchgrass plants within eachfeedstock in thefield. In the soil analysis, we found that the 5-species feedstock displayed higher rates ofsoil N/P/K depletion than other feedstocks. In the greenhouse analysis, we found that switchgrass plantsgrown in soil conditioned by the 5-species feedstock were smaller than plants grown in soil conditionedby other feedstocks. In the physiological analysis, we found that switchgrass plants in the 5-species feed-stock had lower leaf N, photosynthesis, chlorophyll concentration, and higherflorescence than switchgrassplants growing in other feedstocks. Collectively, our results show that prairie agroenergy feedstocks withdifferent species composition and diversity have different rates of soil nutrient depletion, which influencesthe physiology and performance of plants within the feedstock. These differences would ultimately impactthe ecosystem services (e.g., biomass production, need for fertilizer) that these prairie agroenergyfeedstocks provide

Wild bee visitors and floral source associations in the Conservation Reserve Program habitat in NE Iowa

The spreadsheet documents data collected in the study described in the manuscript “Wild bee visitors and their association with sown and unsown floral resources in reconstructed pollinator habitats within an agriculture landscape”. Data included in the spreadsheet shows the name of each collected wild bee specimen and the flower species where the bee was collected. Data were used to construct the bee-pollinator network and calculate the network metrics for each study site

Wild bee visitors and floral source associations in the Conservation Reserve Program habitat in NE Iowa

The spreadsheet documents data collected in the study described in the manuscript “Wild bee visitors and their association with sown and unsown floral resources in reconstructed pollinator habitats within an agriculture landscape”. Data included in the spreadsheet shows the name of each collected wild bee specimen and the flower species where the bee was collected. Data were used to construct the bee-pollinator network and calculate the network metrics for each study site