Biomass Production Varies Among Native Prairie-Grass Species

Native grasslands provide a multitude of benefits to society including forage production, wildlife habitat, and nutrient and CO2 sequestration. There has been increasing interest in using native perennial grassland plantings to produce cellulose-based biofuels. However, there is little information on how biomass production might vary among different native species in a comparable field setting in Western Iowa. Perennial warm-season grasses such as big bluestem, Indian grass, switchgrass, little bluestem or side-oats grama often dominate prairies. In Western Iowa, all five of these species dominate in at least some grassland plantings. In an ongoing study, we are studying how different warm-season grasses vary in their biomass production, weed suppression, and rare prairie species recruitment. Prairie species recruitment will be reported in more detail in future reports. Here, focus is on the differences in biomass production and weed suppression among grass species

An Empirical Comparison of Beta Diversity Indices in Establishing Prairies

Whittaker (1960, 1972) first proposed the idea that species diversity has spatial components, with alpha diversity estimating diversity within individual stands (or communities) and beta diversity estimating the number of community types in an area (or in Whittaker’s terminology, ‘‘differentiation of communities along gradients’’). These two values combined make up gamma diversity. Beta diversity is important because it provides the conceptual link between local and regional diversity, more directly measures how soil types, disturbance, and dispersal affect diversity, and is helpful in understanding why species loss is sometimes smaller than predicted by theory (Wilsey et al. 2005). Many interesting and longstanding questions are applied across scales, such as how much diversity is found within islands vs. across islands? Is the number of habitat types (i.e., beta) within islands key to explaining diversity at larger scales or is it the greater population sizes found on large islands? Furthermore, a consideration of both alpha and beta is necessary for understanding how diversity arises and is maintained in diverse systems. For example, in the northern Great Plains, we have found that remnant prairies can contain over 120 plant species within a small area (Wilsey et al. 2005); this occurs because of high diversity at the neighborhood scale where 20–25 species are found per square meter (Martin et al. 2005), and from species accumulation across neighborhoods (i.e., beta)

Native cover crops and timing of planting: Effects on 15N uptake, weed invasion and prairie establishment

Cover crops have been used for several purposes in prairie restorations. This project looked at whether the assumed benefits are supported by research results

Dominant Grass Effects on Diversity and Functioning of Restored Grassland

Native grasslands provide a multitude of benefits to society including forage production, wildlife habitat, and nutrient and CO2 uptake and storage. There has been continuing interest within the conservation community in restoring grasslands to maximize these multiple benefits. In addition to achieving the most common objectives of reducing soil erosion and increasing organic carbon and nutrient availabilities, restored grasslands also produce important wildlife habitat, and they have the potential to uptake and store greenhouse gases like CO2 . Grassland plantings have been found to increase game and non-game bird abundance and diversity and to improve deer habitat

Importance of Species Replication in Understanding Plant Invasions into North American Grasslands

The global homogenization of the Earth’s biota is expected to increase due to the increase in movement of people and goods between regions, and many introduced species are having a negative economic impact. The increase of introduced species can be thought of as a major global change, because ecosystems throughout the world are now impacted by exotics [1, 2]. Grasslands, which cover roughly 25% of the globe, contain perhaps the most disrupted and homogenized communities in the world. Native grasslands have been lost because of land conversion, and native species have been replaced or displaced with introduced grasses and legumes. Many species were intentionally introduced during the early 20th century to prevent erosion or to improve grazing, and many have undoubtedly done so. However, as management objectives for grasslands have expanded to include wildlife habitat, biodiversity, and C sequestration, it has become critical to understand how introduced species are affecting these new objectives as well. For example, Christian and Wilson [3] found that areas in Saskatchewan, Canada, dominated by the introduced forage grass Agropyron cristatum are sequestering less C into their soils compared to developing native prairie stands with similar land use histories

Quantifying Species Interactions in Experimental Native vs. Exotic Grassland Plant Communities

Native ecosystems are currently being replaced by novel, exotic-dominated ecosystems worldwide. Exotic ecosystems differ from native ecosystems in several important ways. For example, exotic ecosystems are often less diverse than native ecosystems, and often contain species without a shared evolutionary history. Previously we found that biodiversity rapidly declined in experimental exotic communities because the mechanisms that maintained diversity in experimental native communities were reduced. Further investigation is needed to explicitly quantify species interactions in native vs. exotic communities. Here we test the hypothesis that exotic species will exhibit more competition, or less facilitation, than ecologically similar native species

Native Cover Crops and Timing of Planting: Three Years of Establishment

Deciding when and how to plant prairie to simultaneously establish native prairie seedlings and prevent weed (non-prairie species) invasion can be challenging. Planting cover crops is an increasingly common management practice for prairie plantings. The idea is based on the assumption that the cover plant will act as a nurse plant to prairie seedlings and will have a positive effect on seedling recruitment by increasing weed suppression. This is predicted to lead to reduced weed biomass and increased prairie establishment in restoration plantings. However, the evidence supporting these benefits is mostly anecdotal and has been challenged by some

Priority effects are affected by precipitation variability and are stronger in exotic than native grassland species

Exotic perennial grassland species often green up earlier than their native counterparts, allowing them to gain an advantage by dominating resources early (priority effects). Precipitation variability is expected to increase with climate change, and may alter the strength of priority effects. We hypothesized that exotics will have stronger priority effects than natives, precipitation variability will impact the strength of priority effects, and precipitation variability will impact the priority effects of native species more than those of exotics. We seeded one of five native or five exotic grassland species from the Central U.S. spanning multiple functional groups 28 days prior to a native seed mix. Priority effect strength was determined by how much establishment and diversity was reduced in the mix compared to controls (no species seeded before mix). We crossed these priority effect treatments with three water variability treatments, one low variability, and two high variability with alternate timing. Exotic species had stronger priority effects than natives, and decreased diversity and establishment from the seed mix. High variability precipitation when the growing season began dry significantly increased priority effects compared to low variability and high variability beginning wet. We found no significant evidence for a more pronounced impact of precipitation on native species, but trends suggest future studies may reveal significant interactions. Although future research in the field over multiple growing seasons is needed, our results suggest priority effects of exotics in Central U.S. grasslands are independent of precipitation timing and therefore likely to persist under changing climates

Plant Species Effects on Diversity and Weed Invasion Resistance in Restored Grasslands

Native grasslands provide a multitude of benefits to society including forage production, wildlife habitat, and nutrient and CO2 sequestration. There has been continuing interest in restoring grasslands to maximize these multiple benefits within the conservation community. There are presently many ongoing prairie restoration projects, and many more are being started throughout Iowa. Warm-season grasses such as big bluestem, indian grass, switchgrass, little bluestem, or side-oats grama often dominate prairies. In western Iowa, all five of these species are dominant, at least in some patches of grassland. Diversity is what most people are most concerned with when they restore or reconstruct prairie. However, species diversity in prairies is mainly from various forbs. Most prairie restorations become heavily dominated by one or a few grass species without a wide diversity of legumes and forbs. We suggest that understanding how dominant warm-season grasses suppress total plant diversity and prevent weed invasions is a key issue for developing better restoration plans

Improving Prairie Restorations

Deciding when and how to plant prairie to simultaneously establish native prairie seedlings and prevent weed (non-prairie species) invasion can be challenging. Planting cover crops is an increasingly common management practice for prairie plantings. The idea is based on the assumption that the cover plant will act as a nurse plant to prairie seedlings and will have a positive effect on seedling recruitment by increasing weed suppression. This is predicted to lead to reduced weed biomass and increased prairie establishment in restoration plantings