Managing conservation grasslands for bioenergy and wildlife.

摘要

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.