The Effects of Varying Nitrogen Amounts on the Growth and Leaf Morphology of Cattail Species

In Iowa, there are three types of cattails (Typha spp.): Typha latifolia (broadleaf), Typha angustifolia (narrow leaf), and Typha x glauca. T. latifolia is native to Iowa, while T. angustifolia and T. x glauca are not native. Cattails are found in wetlands, highly productive ecosystems that provide many services such as water filtration and flood control. However, Typha are opportunistic and invasive: if left uncontrolled, Typha grows rapidly by clonal reproduction, quickly dominating the ecosystem, lowering overall diversity and hurting the wetland’s conservation value. Being able to easily identify these taxa will improve the pace of future research. The purpose of this study is to understand the effects of different nitrogen amounts on the growth and morphology of each Typha taxon. In order to achieve this, Typha was grown in 1.75-m mesocosms and in 25-cm pots with different amounts of fertilizer. Leaf length and width were measured, and a taxon was assigned based on those measurements. Leaves from these individuals were sampled, ground up for DNA extraction, purified, amplified by PCR, and sequenced. The data show how each taxon’s leaf height and width responds to differing nitrogen amounts

Sown and Unsown Floral Resources Both Support Bee Abundance

The recent decline in native bee populations across the Midwest has been linked to the drastic decrease of prairie habitats and pollinator floral resources. Since the agricultural revolution, grassland areas have been removed and replaced with row crops to meet the needs of expanding markets, including the production of ethanol. In response to the loss of these (and other) essential pollinators, the Conservation Reserve Program administered by the USDA initiated a pollinator habitat initiative called CP-42. Despite efforts to assess the program\u27s success, there is still much that needs to be learned about restoring prairie habitats for bees. With CP-42, we do not know if sown plants are having any effect on pollinators compared to the effects of unsown plants. As a result, the seed mixes are not being improved to optimize the habitat. Since 2016, researchers from UNI Tallgrass Prairie Center and Biology Department have been collecting data on the composition and bee utilization of floral resources in CP-42 fields. In the summer of 2019, we surveyed bee populations and floral resources at 9 sites in northeast Iowa. The floral resources were specified as sown or unsown based on whether that species was included in the planted seed mix. We hypothesized that there is a positive correlation between the overall densities of floral resources and bees. Additionally, we hypothesized that the abundance of sown flowers would have a more positive relationship with bee abundance, compared to the relationship between unsown flower and bee abundance. As expected, a significant positive relationship was found between overall floral abundance and bee abundance of each site. However, analysis comparing the bee and floral abundance from sown and unsown species at each site showed no statistical difference between sown and unsown species. While the CP-42 plantings are attracting bee pollinators, the lack of additional benefit from sown species suggests that seed mixes are not resulting in the most optimal floral resources

Collecting Carbon: An Analysis of Soil Carbon in Conservation Reserve Program Fields and Agricultural Fields

Intensive agricultural practices are associated with detrimental effects to the environment including, but not limited to, increasing the rate of soil erosion, introducing pollutants to water supply, reduced habitat for various species, and reduced atmospheric carbon sequestration in soils. The Conservation Reserve Program allows farmers to enroll sensitive lands into the program and out of circulation for agricultural purposes. It has been shown to increase soil carbon sequestration, reduce erosion, increase water and air quality, and provide habitat restoration for displaced species, along with other benefits

Evaluating vegetation response subsequent to CRP mid-contract management across the western United States: Draft Project Report

It is impossible to explicitly state the degree to which mid-contract management (MCM) impacts the benefits that CRP enrollments provide due to the size of the program and variety of management prescriptions. But it is well documented that all native grasslands evolved with some type of ecological disturbance and the relatively good health of the grassland correlates with its disturbance regime. Concomitantly, all grassland bird communities have habitat requirements that evolved in conjunction with disturbance (primarily grazing). While natural-disturbance regimes may be desirable from an ecological prospective, dependence on natural disturbances to meet specific conservation objectives is unrealistic. Management policies are needed to encourage efforts to preserve and enhance grassland habitat by managing for heterogeneity while offsetting principal threats such as invasion of noxious plant species and woody vegetation. The accumulation of dead vegetation (litter), in the absence of management, greatly retards growth in the spring, prevents the emergence of some plants, reduces flowering, decreases productivity and promotes monocultures. Perpetuation of diversity in grass-species composition is a fundamental goal for trying to sustain desirable habitat for grassland-dependent wildlife. In the absence of natural disturbance, this goal is only accomplished through some form of prescribed management. And while some types of management are superior at replicating historic disturbances (grazing, burning), other forms of management (haying, mowing, disking) accomplish at least some level of necessary disturbance

Biochar amendment of grassland soil may promote woody encroachment by Eastern Red Cedar

Although carbon (C) additions to soil have been used in restoration to combat invasive species through changes in soil nitrogen (N) availability, carbon amendments to soil derived from plant material can impact soil N availability in a species-specific manner. As such, amendment-driven feedbacks on N may impact invasive species success and woody encroachment. Soil amendments like biochar, which is often added to soil to increase C storage in grassland systems, may unintentionally encourage woody encroachment into these grasslands by changing soil N dynamics. Few studies have examined biochar impacts on non-agricultural species, particularly invasive species. Woody encroachment of Eastern Red Cedar (Juniperus virginiana) into grasslands provides an ideal context for examining the impact of biochar in grasslands. In the greenhouse, we examined the effect of biochar or leaf litter derived from native and exotic grasses on J. virginiana seedling growth. Juniperus virginiana seedlings grew 40% bigger in biochar amended soil as compared to seedlings grown in litter amended soil. Additionally, we found a more than 2 order of magnitude increase in available NH4+ in the biochar treatments compared to the litter amended soils. Furthermore we found that biochar feedstock type did not have an impact on the effect of biochar, as both native and exotic grass biochar had similar impacts on soil N levels and J. virginiana growth. Our work suggests that once grassland litter is converted to biochar, species impacts on soil N may disappear. In conclusion, our data suggests soil amendments of biochar may encourage woody encroachment into grasslands

Above- and belowground biomass and soil respiration in a low-input perennial biofuel production system

Backgroud Global climate change largely depends on the atmospheric carbon balance, of which soil respiration is a significant component. Native perennial prairie vegetation is being tested as an alternative to corn for renewable biofuel production. Mixtures of this vegetation are considered ‘carbon negative’ because net CO2 sequestration exceeds atmospheric release1. Studies have shown that aboveground biomass and the rate of carbon sequestration are both increased by planting a diverse mixture of species versus a monoculture1. Research Question: How does the diversity of biofuel vegetation mixtures affect soil respiration, aboveground biomass and belowground biomass

Soil Organic Carbon Accumulation in Restored Native Prairies Over Time

With the recent focus on the causes and effects of climate change, the relationship between agriculture and climate change has become an important concern. Conventional farming maximizes crop production at the expense of ecosystem services like soil carbon storage. As the human population grows, it is vital to develop practices that balance crop production and ecosystem services. We investigated organic carbon accumulation in restored prairie soil over the course of a decade. Our goal was to determine how organic carbon levels and soil bulk density changed over time, and how that change was influenced by species diversity and soil depth. We hypothesized that more organic carbon would be stored in soil over time, and bulk density would decrease, both of which we found to be true. We also hypothesized that the amount of organic carbon stored would increase with greater species diversity (1-species, and 5-, 16-, and 32-species mixes) and it would decrease with soil depth. Our results showed us that species diversity has no noticeable effect on organic carbon levels, with the 5-species mix being the exception, as it stored very low levels of organic carbon. In both soil depths (0-7.5 cm and 7.5-15.0 cm), bulk density increased the first 5 years, then decreased drastically over the next 6 years, but when we compared 0-7.5 cm and 7.5-15.0 cm depths with each other, we found an overall decrease. We concluded that organic carbon accumulation increases over time in restored prairie soil regardless of species diversity or soil depth

Effectiveness of cattail (Typha spp.) management techniques depends on exogenous nitrogen inputs

Wetlands occupy a position in the landscape that makes them vulnerable to the effects of current land use and the legacies of past land use. Many wetlands in agricultural regions like the North American Midwest are strongly affected by elevated nutrient inputs as well as high rates of invasion by the hybrid cattail Typha × glauca. These two stressors also exacerbate each other: increased nutrients increase invasion success, and invasions increase nutrient retention and nutrient loads in the wetland. This interaction could create a positive feedback that would inhibit efforts to manage and control invasions, but little is known about the effects of past or present nutrient inputs on wetland invasive plant management. We augmented a previously-published community-ecosystem model (MONDRIAN) to simulate the most common invasive plant management tools: burning, mowing, and herbicide application. We then simulated different management strategies and 3 different durations in low and high nutrient input conditions, and found that the most effective management strategy and duration depends strongly on the amount of nutrients entering the wetland. In high-nutrient wetlands where invasions were most successful, a combination of herbicide and fire was most effective at reducing invasion. However, in low-nutrient wetlands this approach did little to reduce invasion. A longer treatment duration (6 years) was generally better than a 1-year treatment in high-nutrient wetlands, but was generally worse than the 1-year treatment in low-nutrient wetlands. At the ecosystem level, we found that management effects were relatively modest: there was little effect of management on ecosystem C storage, and while some management strategies decreased wetland nitrogen retention, this effect was transient and disappeared shortly after management ceased. Our results suggest that considering nutrient inputs in invaded wetlands can inform and improve management, and reducing nutrient inputs is an important component of an effective management strateg

Plant Size and Competitive Dynamics along Nutrient Gradients

Resource competition theory in plants has focused largely on resource acquisition traits that are independent of size, such as traits of individual leaves or roots or proportional allocation to different functions. However, plants also differ in maximum potential size, which could outweigh differences in module-level traits. We used a community ecosystem model called mondrian to investigate whether larger size inevitably increases competitive ability and how size interacts with nitrogen supply. Contrary to the conventional wisdom that bigger is better, we found that invader success and competitive ability are unimodal functions of maximum potential size, such that plants that are too large (or too small) are disproportionately suppressed by competition. Optimal size increases with nitrogen supply, even when plants compete for nitrogen only in a size-symmetric manner, although adding size-asymmetric competition for light does substantially increase the advantage of larger size at high nitrogen. These complex interactions of plant size and nitrogen supply lead to strong nonlinearities such that small differences in nitrogen can result in large differences in plant invasion success and the influence of competition along productivity gradients

Density and Diversity of Bees in the Midwestern Agricultural Landscape: Influence of Surrounding Agricultural Land Use and Biofuel Candidate Crops

Recent trends in land management practices have led to dramatic population decline in bees and other insect pollinators (Cameron et al. 2011). Concerns about “Colony Collapse Disorder” in domestic honeybees, for example, have received widespread high-profile attention in the scientific community. While concerns have centered mainly on the domestic honeybee, native bees also provide indispensable, cost-free pollination services to crops production. Despite the value of native bee species, little is known about them in the Midwest region, and recent studies suggest their populations may be in decline specifically due to a lack of native vegetation in this highly agricultural landscape. Vegetable farms and lands managed for cellulosic biofuels have the potential to provide usable habitat, but their utility is not well understood