Assessments of wetland restorations in the prairie region are not done routinely and no accepted ... more Assessments of wetland restorations in the prairie region are not done routinely and no accepted assessment framework exists. Wetland assessment protocols in the U.s. have varied over time from those emphasizing social significance to those attempting to quantify functions of wetlands from hydrogeomorphic considerations. A conceptual framework for restoration decision-making is presented that is based on optimizing wetland restoration success at both the landscape and site scales. This framework uses societal concerns, knowledge of factors that limit ecosystem recovery, and data on losses of different types of wetlands locally and regionally to establish restoration goals and guide site selection. These goals in turn generate restoration expectations or targets. Currently, restoration expectations are usually formulated only at the basin scale. Prairie pothole wetlands, however, were historically part of wetland complexes. Consequently, restoration efforts should focus on restoring ...
The number of dominant vegetation types (wet prairies, sawgrass flats, ridges and sloughs, slough... more The number of dominant vegetation types (wet prairies, sawgrass flats, ridges and sloughs, sloughs, and tree islands) historically and currently found in the Everglades, FL, USA, as with other wetlands with standing water, appears to be primarily a function of the magnitude of interannual water-level fluctuations. Analyses of 40 years of water-depth data were used to estimate the magnitude of contemporary (baseline) water-level fluctuations in undisturbed ridge and slough landscapes. Baseline interannual water-level fluctuations above the soil surface were at least 1.5 m. Predicted changes in interannual water-level fluctuations in 2060 were examined for seven climate change scenarios. When rainfall is predicted to increase by 10 %, the wettest scenario, the interannual range of water-level fluctuation increases to 1.8 m above the soil surface in sloughs. When rainfall is predicted to decrease by 10 % and temperatures to increase by 1.5 °C, the driest scenario, the range of interann...
Vallisneria americana declined in backwaters of the Upper Mississippi River, U.S.A., after a drou... more Vallisneria americana declined in backwaters of the Upper Mississippi River, U.S.A., after a drought in 1988. To determine whether viable seeds of V. americana occurred in the seed bank of navigation pool 7, Lake Onalaska, the upper 5 cm of sediment was collected from 103 sites in May 1990. These sediment samples were kept in pots at a depth of 0.4, 0.8, and 1.2 m in an outdoor pond for 12 weeks. Vallisneria americana seeds germinated from sites throughout the lake, and some seedlings produced overwintering buds by the end of the study. Seeds, spores, or fragments of 12 other species of aquatic plants also germinated. Seed germination trials with fresh and stored seeds in both greenhouse and ponds in which light availability was reduced with shade cloths indicated that seed germination was insensitive to light level. To determine the light requirements for seedling survival and bud production, sediment from Lake Onalaska was incubated in ponds under neutral density shade screens red...
Hundreds of wetlands comprising thousands of hectares have been restored in the Midwestern United... more Hundreds of wetlands comprising thousands of hectares have been restored in the Midwestern United States. In nearly all cases, restoration consisted of simply restoring wetland hydrology. For this reason, the success of these restorations relies on natural colonization. We compared the structure and composition of the vegetation in two types of wetlands: 10 natural wetlands and 17 five-to-seven-year-old restored wet-
In this study, we examined the effects of water depth and temperature on seedling recruitment fro... more In this study, we examined the effects of water depth and temperature on seedling recruitment from a prairie wetland seed bank. We collected seed-bank samples from natural and restored prairie pothole wetlands in northwestern Iowa and combined them into a single sample. We examined seedling recruitment from this seed-bank sample in an experimental study using a factorial design of 4
After channellization of the Kissimmee River, the primary land use of the drained floodplain was ... more After channellization of the Kissimmee River, the primary land use of the drained floodplain was cattle pasture but included sod farms. A project to restore the river began in 1999. One of its goals is to reestablish the three dominant, pre-channelization vegetation types (wetland shrub, broadleaf marsh, and wet prairie) in areas where they previously were found. We investigated whether
Abstract Between 1987 and 1991, 1892 prairie potholes were restored in northern Iowa, southern Mi... more Abstract Between 1987 and 1991, 1892 prairie potholes were restored in northern Iowa, southern Minnesota, and southeastern South Dakota by state and federal agencies, most as part of the Conservation Reserve Program. The total area covered by these restored ...
Abstract The biologically mediated transfer of nutrients from one part of a landscape to another ... more Abstract The biologically mediated transfer of nutrients from one part of a landscape to another may create nutrient gradients or subsidize the productivity at specific locations. If limited, this focused redistribution of the nutrient may create non-random landscape patterns that are ...
Assessments of wetland restorations in the prairie region are not done routinely and no accepted ... more Assessments of wetland restorations in the prairie region are not done routinely and no accepted assessment framework exists. Wetland assessment protocols in the U.s. have varied over time from those emphasizing social significance to those attempting to quantify functions of wetlands from hydrogeomorphic considerations. A conceptual framework for restoration decision-making is presented that is based on optimizing wetland restoration success at both the landscape and site scales. This framework uses societal concerns, knowledge of factors that limit ecosystem recovery, and data on losses of different types of wetlands locally and regionally to establish restoration goals and guide site selection. These goals in turn generate restoration expectations or targets. Currently, restoration expectations are usually formulated only at the basin scale. Prairie pothole wetlands, however, were historically part of wetland complexes. Consequently, restoration efforts should focus on restoring ...
The number of dominant vegetation types (wet prairies, sawgrass flats, ridges and sloughs, slough... more The number of dominant vegetation types (wet prairies, sawgrass flats, ridges and sloughs, sloughs, and tree islands) historically and currently found in the Everglades, FL, USA, as with other wetlands with standing water, appears to be primarily a function of the magnitude of interannual water-level fluctuations. Analyses of 40 years of water-depth data were used to estimate the magnitude of contemporary (baseline) water-level fluctuations in undisturbed ridge and slough landscapes. Baseline interannual water-level fluctuations above the soil surface were at least 1.5 m. Predicted changes in interannual water-level fluctuations in 2060 were examined for seven climate change scenarios. When rainfall is predicted to increase by 10 %, the wettest scenario, the interannual range of water-level fluctuation increases to 1.8 m above the soil surface in sloughs. When rainfall is predicted to decrease by 10 % and temperatures to increase by 1.5 °C, the driest scenario, the range of interann...
Vallisneria americana declined in backwaters of the Upper Mississippi River, U.S.A., after a drou... more Vallisneria americana declined in backwaters of the Upper Mississippi River, U.S.A., after a drought in 1988. To determine whether viable seeds of V. americana occurred in the seed bank of navigation pool 7, Lake Onalaska, the upper 5 cm of sediment was collected from 103 sites in May 1990. These sediment samples were kept in pots at a depth of 0.4, 0.8, and 1.2 m in an outdoor pond for 12 weeks. Vallisneria americana seeds germinated from sites throughout the lake, and some seedlings produced overwintering buds by the end of the study. Seeds, spores, or fragments of 12 other species of aquatic plants also germinated. Seed germination trials with fresh and stored seeds in both greenhouse and ponds in which light availability was reduced with shade cloths indicated that seed germination was insensitive to light level. To determine the light requirements for seedling survival and bud production, sediment from Lake Onalaska was incubated in ponds under neutral density shade screens red...
Hundreds of wetlands comprising thousands of hectares have been restored in the Midwestern United... more Hundreds of wetlands comprising thousands of hectares have been restored in the Midwestern United States. In nearly all cases, restoration consisted of simply restoring wetland hydrology. For this reason, the success of these restorations relies on natural colonization. We compared the structure and composition of the vegetation in two types of wetlands: 10 natural wetlands and 17 five-to-seven-year-old restored wet-
In this study, we examined the effects of water depth and temperature on seedling recruitment fro... more In this study, we examined the effects of water depth and temperature on seedling recruitment from a prairie wetland seed bank. We collected seed-bank samples from natural and restored prairie pothole wetlands in northwestern Iowa and combined them into a single sample. We examined seedling recruitment from this seed-bank sample in an experimental study using a factorial design of 4
After channellization of the Kissimmee River, the primary land use of the drained floodplain was ... more After channellization of the Kissimmee River, the primary land use of the drained floodplain was cattle pasture but included sod farms. A project to restore the river began in 1999. One of its goals is to reestablish the three dominant, pre-channelization vegetation types (wetland shrub, broadleaf marsh, and wet prairie) in areas where they previously were found. We investigated whether
Abstract Between 1987 and 1991, 1892 prairie potholes were restored in northern Iowa, southern Mi... more Abstract Between 1987 and 1991, 1892 prairie potholes were restored in northern Iowa, southern Minnesota, and southeastern South Dakota by state and federal agencies, most as part of the Conservation Reserve Program. The total area covered by these restored ...
Abstract The biologically mediated transfer of nutrients from one part of a landscape to another ... more Abstract The biologically mediated transfer of nutrients from one part of a landscape to another may create nutrient gradients or subsidize the productivity at specific locations. If limited, this focused redistribution of the nutrient may create non-random landscape patterns that are ...
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Papers by Arnold Valk