Browsing by Subject "Prairies"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    The effects of eastern red cedar (Juniperus virginiana) invasion and removal on a dry bluff prairie ecosystem
    (2010) Pierce, Ann M; Reich, Peter B
    Eastern red cedar (Juniperus virginiana) establishment increased dramatically in the tallgrass prairie biome of North America during the last 30 years. Since many of the remaining remnant prairies occur on steep, dry, and nutrient poor sites, threatened by the invasion of native and non-native woody species, it is important to understand how an invasive species such as eastern red cedar influences key environmental factors that may determine the future trajectory of these systems and whether abiotic and biotic components of the system are resilient following cedar removal. To address these issues we: (1) investigated the influence of eastern red cedar on micro-environmental factors; (2) evaluated how these micro-environmental factors responded to eastern red cedar removal; and (3) assessed the effect of eastern red cedar on herbaceous species germination and distribution. The invasion of eastern red cedar was associated with lower surface light availability and soil temperature, as seen in prior studies, but otherwise had effects distinct from those observed in prior studies. There was no effect of cedar on soil pH, and unlike prior studies, cedar patches had higher soil moisture compared to native C4 prairie grass plots. Moreover, these effects had strong spatial signatures, with impacts of invasion on micro-environment and native vegetation differing dramatically with slope position and aspect. Three years after eastern red cedar was removed, micro-environmental factors and species composition became similar to the tree-free grass-dominated plots, indicating a significant capacity for recovery following possible cedar control. In a broader context, this study sheds light on the pathways and mechanisms driving the impacts of this biological invasion on dry, steep, nutrient poor systems and illustrates the capability of these systems to recover once the invading species is removed.
  • Thumbnail Image
    Item
    Managing conservation grasslands for bioenergy and wildlife
    (2014-02) Jungers, Jacob Michael
    Greenhouse gas emissions continue to rise while native grassland habitat continues to decline. A potential solution to both of these conservation priorities may exist in bioenergy. Various state and federal agencies maintain tracts of conservation grasslands, usually native perennial plants, for recreation and habitat. If biomass from conservation grasslands can be harvested without harming habitat and wildlife, then sales of grassland biomass to bioenergy producers may be the economic catalyst to expand conservation grassland acreage. This dissertation reports the bioenergy potential of conservation grasslands, how that potential can be improved, and possible effects of biomass harvest on grassland plants, ducks, and pheasants. Chapter one quantifies the bioenergy potential of biomass from conservation grasslands and identifies environmental characteristics that influence that potential. Chapter two reports an agronomically optimum nitrogen fertilization rate to increase bioenergy yields from switchgrass (Panicum virgatum) and mixed-species grasslands. Chapter three summarizes the effects of biomass harvest on plant diversity and species composition. Chapter four relates plant diversity and composition to duck and pheasant nest density and survival, and measures the effect of biomass harvest on both metrics of reproduction. Some major conclusion include: (1) Estimates of bioenergy potential suggest that 50% of the conservation grassland acreage within an 80 km radius of southwestern Minnesota could produce 75,700,000 liters of ethanol annually. (2) On average, bioenergy yields are predicted to increase by 52% when fertilized with agronomically optimum nitrogen rates ranging from 61 to 87 kg N ha-1. (3) Biomass harvest did not affect plant species richness, species or functional group diversity, nor change the relative abundance of the main plant functional groups in conservation grasslands. (4) Pheasant and duck nest success rates were similar in harvested and unharvested regions of conservation grasslands, but nest density was greater in unharvested regions. Overall, a substantial amount of renewable energy can be produced from harvested conservation grassland biomass without detrimental effects on plant communities or nesting pheasants and ducks.