Robert A. Gleason

Effects of sediment load on emergence of aquatic invertebrates and plants from wetland soil egg and seed banks

Intensive agricultural activities near prairie wetlands may result in excessive sediment loads, which may bury seed and invertebrate egg banks that are important for maintenance and cycling of biotic communities during wet/dry cycles. We evaluated effects of sediment burial on emergence of plants and invertebrates from seed and invertebrate egg banks. Sediment-load experiments, indicated that burial depths of 0.5 cm caused a 91.7% reduction in total seedling emergence and a 99.7% reduction in total invertebrate emergence. Results of our burial experiments corroborated prior research on seedling emergence. However, our study demonstrated that invertebrate emergence is also highly susceptible to the effects of burial. Our research suggests that sediment entering wetlands from agricultural erosion may also hamper successional changes throughout interannual climate cycles. Land-management strategies need to be implemented that will prevent erosion of cropland top soil from entering wetlands.

USDA conservation program and practice effects on wetland ecosystem services in the Prairie Pothole Region

Implementation of the U.S. Department of Agriculture (USDA) Conservation Reserve Program (CRP) and Wetlands Reserve Program (WRP) has resulted in the restoration of >2 million ha of wetland and grassland habitats in the Prairie Pothole Region (PPR). Restoration of habitats through these programs provides diverse ecosystem services to society, but few investigators have evaluated the environmental benefits achieved by these programs. We describe changes in wetland processes, functions, and ecosystem services that occur when wetlands and adjacent uplands on agricultural lands are restored through Farm Bill conservation programs. At the scale of wetland catchments, projects have had positive impacts on water storage, reduction in sedimentation and nutrient loading, plant biodiversity, carbon sequestration, and wildlife habitat. However, lack of information on the geographic location of restored catchments relative to landscape-level factors (e.g., watershed, proximity to rivers and lakes) limits interpretation of ecosystem services that operate at multiple scales such as floodwater retention, water quality improvement, and wildlife habitat suitability. Considerable opportunity exists for the USDA to incorporate important landscape factors to better target conservation practices and programs to optimize diverse ecosystem services. Restoration of hydrologic processes within wetlands (e.g., hydroperiod, water level dynamics) also requires a better understanding of the influence of conservation cover composition and structure, and management practices that occur in uplands surrounding wetlands. Although conservation programs have enhanced delivery of ecosystem services in the PPR, the use of programs to provide long-term critical ecosystem services is uncertain because when contracts (especially CRP) expire, economic incentives may favor conversion of land to crop production, rather than reenrollment. As demands for agricultural products (food, fiber, biofuel) increase, Farm Bill conservation programs will become increasingly important to ensure provisioning of ecosystem services to society, especially in agriculturally dominated landscapes. Thus, continued development and support for conservation programs legislated through the Farm Bill will require a more comprehensive understanding of wetland ecological services to better evaluate program achievements relative to conservation goals.

Integrating estimates of ecosystem services from conservation programs and practices into models for decision makers

Most government agencies involved in land management are seeking consistent approaches to evaluate the effects of specific management actions on ecological processes and concurrent changes on ecosystem services. This is especially true within the context of anthropogenic influences, such as land use and climate change. The Conservation Effects Assessment Project—Wetlands National Component (CEAP–Wetlands) was developed by the U.S. Department of Agriculture (USDA) to evaluate effects of conservation practices on ecosystem services including carbon sequestration for climate stability, groundwater recharge, runoff and flood attenuation, water storage, nutrient and contaminant retention, and wildlife habitat. A primary purpose of CEAP–Wetlands is to provide science-based information in an adaptive monitoring framework for use by the USDA to facilitate policy and management decisions, and to document effects of conservation programs and practices to the federal Office of Management and Budget. Herein, we propo...

Invertebrate egg banks of restored, natural, and drained wetlands in the Prairie Pothole Region of the United States

Analogous to ‘seed banks,’ ‘egg banks’ are important for seasonal succession and maintenance of invertebrate species diversity throughout wet and dry cycles in the prairie pothole region. Further, recruitment of invertebrates from relic egg banks in the sediments and dispersal of eggs into wetlands is believed to be important for reestablishment of invertebrates in recently restored wetlands. Although tens-of-thousands of wetlands have been restored in the prairie pothole region of the United States, studies have not been conducted to evaluate the recovery of invertebrate egg banks in restored wetlands. We used taxon richness and abundance as indicators of potential egg bank recovery and compared these parameters in restored wetlands to those of non-drained and drained wetlands with a history of cultivation and also to reference wetlands with no history of cultivation. We found few significant differences among wetland categories within three physiographic regions (Glaciated Plains, Missouri Coteau, and Prairie Coteau). Most statistical comparisons indicated that restored wetlands had invertebrate egg banks similar to reference, nondrained, and drained wetlands. The one exception was drained seasonal wetlands in the Glaciated Plains, which had significantly lower taxon richness and invertebrate abundance than the other wetland categories. Trends did suggest that invertebrate egg bank taxon richness and abundance are increasing in restored seasonal wetlands relative to their drained analogues, whereas a similar trend was not observed for restored semi-permanent wetlands. Although recovery was not related to years since restoration, comparisons of restored wetlands with reference wetlands suggest that recovery potential may be inversely related to the extent of wetland drainage and intensive agriculture that varies spatially in the prairie pothole region. Our research suggests that periodic drawdowns of semi-permanent restored wetlands may be needed to promote production and development of invertebrate egg banks. Inoculation of restored wetlands may also be needed in areas where extensive wetland drainage has resulted in fewer wetland habitats to provide sources of passively dispersed eggs to newly restored wetlands.

Effects of land use on greenhouse gas fluxes and soil properties of wetland catchments in the Prairie Pothole Region of North America

Wetland restoration has been suggested as policy goal with multiple environmental benefits including enhancement of atmospheric carbon sequestration. However, there are concerns that increased methane (CH4) emissions associated with restoration may outweigh potential benefits. A comprehensive, 4-year study of 119 wetland catchments was conducted in the Prairie Pothole Region of the north-central U.S. to assess the effects of land use on greenhouse gas (GHG) fluxes and soil properties. Results showed that the effects of land use on GHG fluxes and abiotic soil properties differed with respect to catchment zone (upland, wetland), wetland classification, geographic location, and year. Mean CH4 fluxes from the uplands were predictably low (<0.02 g CH4 m(-2) day(-1)), while wetland zone CH4 fluxes were much greater (<0.001-3.9 g CH4 m(-2) day(-1)). Mean cumulative seasonal CH4 fluxes ranged from roughly 0-650 g CH4 m(-2), with an overall mean of approximately 160 g CH4 m(-2). These maximum cumulative CH4 fluxes were nearly 3 times as high as previously reported in North America. The overall magnitude and variability of N2O fluxes from this study (<0.0001-0.0023 g N2O m(-2) day(-1)) were comparable to previously reported values. Results suggest that soil organic carbon is lost when relatively undisturbed catchments are converted for agriculture, and that when non-drained cropland catchments are restored, CH4 fluxes generally are not different than the pre-restoration baseline. Conversely, when drained cropland catchments are restored, CH4 fluxes are noticeably higher. Consequently, it is important to consider the type of wetland restoration (drained, non-drained) when assessing restoration benefits. Results also suggest that elevated N2O fluxes from cropland catchments likely would be reduced through restoration. The overall variability demonstrated by this study was consistent with findings of other wetland investigations and underscores the difficulty in quantifying the GHG balance of wetland systems.

Greenhouse gas fluxes of grazed and hayed wetland catchments in the U.S. Prairie Pothole Ecoregion

Wetland catchments are major ecosystems in the Prairie Pothole Region (PPR) and play an important role in greenhouse gases (GHG) flux. However, there is limited information regarding effects of land-use on GHG fluxes from these wetland systems. We examined the effects of grazing and haying, two common land-use practices in the region, on GHG fluxes from wetland catchments during 2007 and 2008. Fluxes of methane (CH4), nitrous oxide (N2O), and carbon dioxide (CO2), along with soil water content and temperature, were measured along a topographic gradient every other week during the growing season near Ipswich, SD, USA. Closed, opaque chambers were used to measure fluxes of soil and plant respiration from native sod catchments that were grazed or left idle, and from recently restored catchments which were seeded with native plant species; half of these catchments were hayed once during the growing season. Catchments were adjacent to each other and had similar soils, soil nitrogen and organic carbon content, precipitation, and vegetation. When compared with idle catchments, grazing as a land-use had little effect on GHG fluxes. Likewise, haying had little effect on fluxes of CH4 and N2O compared with non-hayed catchments. Haying, however, did have a significant effect on combined soil and vegetative CO2 flux in restored wetland catchments owing to the immediate and comprehensive effect haying has on plant productivity. This study also examined soil conditions that affect GHG fluxes and provides cumulative annual estimates of GHG fluxes from wetland catchment in the PPR.