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Geology topics

Beth A. Middleton

Publications and source records attributed to Beth A. Middleton.

At least 37 records · Page 2Linked to original sources
USGS2022

Ventilation systems in wetland plant species

Molecular oxygen and carbon dioxide may be limited for aquatic plants, but they have various mechanisms for acquiring these gases from the atmosphere, soil, or metabolic processes. The most common adaptations of aquatic plants involve various aerenchymatic structures, which occur in various organs, and enable the throughflow of gases. These gases can be transferred in emergent plants by molecular diffusion, pressurized gas flow, and Venturi-induced convection. In submerged species, the direct exchange of gases between submerged above-ground tissues and water occurs, as well as the transfer of gases via aerenchyma. Photosynthetic O 2 streams to the rhizosphere, while soil CO 2 streams towards leaves where it may be used for photosynthesis. In floating-leaved plants anchored in the anoxic sediment, two strategies have developed. In water lilies, air enters through the stomata of young leaves, and streams through channels towards rhizomes and roots, and back through older leaves, while in lotus, two-way flow in separate air canals in the petioles occurs. In Nypa Steck palm, aeration takes place via leaf bases with lenticels. Mangroves solve the problem of oxygen shortage with root structures such as pneumatophores, knee roots, and stilt roots. Some grasses have layers of air on hydrophobic leaf surfaces, which can improve the exchange of gases during submergence. Air spaces in wetland species also facilitate the release of greenhouse gases, with CH 4 and N 2 O released from anoxic soil, which has important implications for global warming.

Diversity↗
USGS2022

Worldwide wetland loss and conservation of biodiversity and ecosystem services

Aim : Best strategies for future conservation and management to address global and regional trends in wetland loss and degradation are assessed in this article. Main concepts covered : Direct drivers of wetland loss and change include land drainage and filling, hydrologic alteration, degradation from pollutants and sediments, and conversion to agriculture, urban and industrial usage. Estimates of global wetland loss are as high as 87% since 1700 CE. All regions of the world have lost wetland area. The designation of wetland protected area reduces disturbance by humans and supports the conservation of biodiversity and habitat. Protected areas have been designated by local, state, or federal entities, NGOs (e.g., Nature Conservancy), and the Ramsar Convention on Wetlands. Protected wetlands have great value for human society. For example, wetlands such as peatland and swamp store carbon that would otherwise be released as greenhouse gases to the atmosphere. A case study of the Keoladeo National Park, Rajasthan, India underscores the importance of maintaining water supply to maintain aquatic vegetation in protected wetlands. Conclusion/outlook : Given the combined stresses of land-use and climate change to wetland protected areas, management of altered wetlands may improve their function. Beneficial management actions can include freshwater remediation of hydrologically-altered floodplains, improved wetland reserve design, assisted migration, and the softening of burning/cutting during drought. A better knowledge of potential of management actions to remediate land-use change will be helpful in addressing protected area management to promote conservation in the future.

Book chapter↗
USGS2022

Salinification of coastal wetlands and freshwater management to support resilience

Climates are rapidly changing in wetland ecosystems around the world and historical land-use change is not always given enough consideration in climate adaptation discussions. Historical changes to hydrology and other key environments can exacerbate vegetation stress; e.g., recent drought and flood episodes are likely more extreme because of climate change. The contributions of global and regional changes that affect groundwater and surface water availability all need consideration in conservation planning including sea-level rise, coastal subsidence and compaction, fluid extraction, and floodplain reengineering. Where subsidence is not too extreme, healthy coastal vegetation often can keep ahead of sea-level rise by accreting elevation through sedimentary and/or biogenic processes. Better water conservation and minimum water delivery during drought may support foundational species and avoid wetland collapse. Local approaches have been developed to rewet inland floodplains decades after their reengineering for agricultural and urban development to support biodiversity in salinified coastal wetlands. The purpose of this paper is to describe inland wetland remediation techniques that may also be useful to increase freshwater delivery to coastal wetlands experiencing salinification. While some salinified coastal ecosystems may transition in the future, attempts can be made to remediate salinification related to historical land use in support of wetland conservation, health, and sustainability.

Ecosystem Health and Sustainability↗
USGS2021

A U.S.-China EcoPartnership study of disturbed wetland vegetation in West Dongting Lake, China

West Dongting Lake in China is important for human livelihoods and habitat of migratory waterfowl and other wildlife. The waterway re-engineering and agriculture intensification have contributed to changes in hydrology, sediment, and vegetation on the floodplain. This paper describes an EcoPartnership program conducted by the U.S. Geological Survey, Wetland and Aquatic Research Center, and Beijing Forestry University. It focused on the development of a wetland ecosystem network in West Dongting Lake with technical support from the U.S. partner using a number of related studies to examine wetland vegetation dynamics from upstream to downstream along the tributaries. The results of U.S. studies showed that the regeneration potential of species might be altered by changes in climate and local environment, and seed bank depletion by germination may be a major conservation threat in a future with recurring droughts in swamps of the southeastern United States. In the monsoonal wetlands of West Dongting Lake, the soil seed bank could be used as a seed source for revegetation after hydrologic restoration with the introduction of certain foundational species and the removal of poplar plantations. Also, West Dongting Lake is at high ecological risk of mercury pollution. Wetland ecosystem monitoring may allow managers to use the information to predict effects of climate change, water level and flow changes on sedimentation, and to manage for desired vegetation to support waterfowl and ecosystem services. The cooperation of two countries through the EcoPartnership program is now well established and poised for extensive research projects in the future.

West Dongting Lake↗
USGS2021

Restoration of mangrove forest

Mangrove forests occur worldwide along tropical coasts in inundated soils where primary production and anaerobic conditions contribute to the building of soil organic matter (Also see Mangroves Hot-spot, Volume 2). Note that peat may accumulate in certain coastal mangrove (Middleton and McKee, 2001). The actual amount of soil organic matter stored in these wetlands depends on the balance between primary production and decomposition processes (Middleton and McKee, 2001; Kolka et al., 2018; Middleton, 2020). The restoration of mangroves can increase carbon stocks both in soil and aboveground biomass (Wickland et al., 2013; Chimner et al., 2017; Friess et al., 2019). While tropical inland peatland forests may have higher carbon sequestration rates than mangrove swamps, methane (CH4) emissions are generally lower in mangrove swamp, so that these wetlands have greater carbon sequestration potential (Kolka et al., 2018; Al-Haj and Fulweiler, 2020). Mangroves and forested boreal and temperate peatlands tend to store more carbon than non-forested peatlands (Kolka et al., 2018).

Book chapter↗
USGS2020

Trends of litter decomposition and soil organic matter stocks across forested swamp environments of the southeastern US

A common idea in the discussion of soil carbon processes is that litter decomposition rates and soil carbon stocks are inversely related. To test this overall hypothesis, simultaneous studies were conducted of the relationship of environmental gradients to leaf and wood decomposition, buried cloth decomposition and percent soil organic matter in Taxodium distichum swamps across the Mississippi River Alluvial Valley (MRAV) and northern Gulf of Mexico (GOM) of the US. Decomposition of leaf tissue was 6.2 to 10.9 times faster than wood tissue. Both precipitation and flooding gradients were negatively related to leaf and wood litter decomposition rates based on models developed using Stepwise General Model Selection (MRAV vs. GOM, respectively). Cotton cloth should not be used as a proxy for plant litter without prior testing because cloth responded differently than plant litter to regional environmental gradients in T . distichum swamps. The overall hypothesis was supported in the MRAV because environments with higher precipitation (climate normal) had lower rates of decomposition and higher percent soil organic matter. In the MRAV, higher levels of percent soil organic matter were related to increased 30-year climate normals (30 year averages of precipitation and air temperature comprising southward increasing PrinComp1). Soil organic carbon % in inland vs. coastal T . distichum forests of the MRAV were comparable (range = 1.5% to 26.9% vs. 9.8 to 31.5%, respectively). GOM swamps had lower rates of litter decomposition in more flooded environments. Woody T . distichum detritus had a half-life of up to 300 years in the MRAV, which points to its likely role in the maintenance of inland “teal” soil organic carbon. This unique study can contribute to the discussion of approaches to maintain environments conducive to soil carbon stock maximization.

Arkansas, Florida, Illinois, Louisiana, Mississipp↗
USGS2020

Carbon stock trends of baldcypress knees along climate gradients of the Mississippi River Alluvial Valley using allometric methods

Carbon stock trends of the knees of Taxodium distichum likely vary across climate gradients of the southeastern United States and contribute an unknown quantity of “teal” carbon to inland freshwater wetlands. Knee metrics (e.g., density, height, biomass) were measured in mixed T. distichum swamps across the Mississippi River Alluvial Valley (MRAV) from Illinois to Louisiana. Based on their geometric similarity to a cone, the biomasses of field knees were estimated by relating the volume of their measured field dimensions to lab-measured water displacement volume and biomass via volume/mass regressions (biomass (g) = 7.2230149 + 0.292902 × volume). Knees had greater height in flooded conditions (maximum height = 163 cm; Goose Lake, Arkansas), and also in climate normal environments of mid-range precipitation and temperature (p < 0.0001). Overall, knee biomass ha−1 was 7.5 times greater in flooded vs. not flooded conditions (34.6 ± 7.3 vs. 4.6 ± 1.0 Mg ha−1, respectively). The overall mean of knee carbon biomass stock was substantial (flooded vs. not flooded conditions: 18.1 ± 3.7 Mg C ha−1 to 2.9 ± 0.7 Mg C ha−1, respectively; knee/tree live standing biomass: 17.9–5.2%, respectively). Clearly, T. distichum knees should not be ignored in blue (teal) carbon discussions of wetlands. Because knees respond to climate normal conditions, hotter/drier environments in the MRAV could lead to a decline in the contribution of knee carbon stock in the southeastern United States.

Mississippi River Alluvial Valley↗
USGS2020

Spatial distribution of heavy metals in the West Dongting Lake floodplain, China

The protection of Dongting Lake is important because it is an overwintering and migration route for many rare and endangered birds of East Asia and Australasia, but an assessment of heavy metal contamination in West Dongting Lake is lacking. A total of 75 sediment samples (five sites x three sediment depths x five repeats) were collected in West Dongting Lake in January 2017 to assess the spatial distribution and ecological risk of heavy metal in West Dongting Lake. Heavy metal values varied by sediment depth including As, Cd, Zn, and Cu, with depth giving an indication of recent vs. historical deposition. The major input of Hg, Cu, Ni may come from continued anthropogenic activities related to regional industrial activities within Yuan River and Li River whereas, the major sources of spread Cd pollution may be from agricultural fertilizers.

West Dongting Lake floodplain↗
USGS2019

Plot Locator: An app for locating plots in the field

PREMISE: One of the challenges in field biology is locating previously sampled plots. The Plot Locator app was developed to assist field biologists with plot identification and location, with or without GPS or online connectivity. METHODS AND RESULTS: The Plot Locator Android app helps users locate field plots by creating a searchable database that stores study area information, such as site/plot names and numbers, distances from landmarks, optional cardinal directions and GPS coordinates, and field notes. A GPS assist and Google Maps can also be used with the app when connectivity is available. All study location data and field notes are stored in a downloadable CSV file on the user’s device. CONCLUSIONS: The Plot Locator app provides a comprehensive searchable database of study area information, plot location information, and location aids, which are easily accessed in the field.

Applications in Plant Science↗
USGS2019

Perspective: Developing flow policies to balance the water needs of humans and wetlands requires a landscape scale approach inclusive of future scenarios and multiple timescales

Maintenance of the natural flow regime is essential for continued wetland integrity; however, the flow regime is greatly influenced by both natural and anthropogenic forces. Wetlands may be particularly susceptible to altered flow regimes as they are directly impacted by water flows at a variety of time scales. In Puerto Rico, contemporary water management is decreasing freshwater recharge to wetlands and contributes to the salinization of important coastal wetlands as sea levels rise. Further, downscaled climate models predict an increase in drought frequency, intensity, and duration by mid-century. Conflicts over water allocation seem imminent between human and ecological needs. Current minimum flow policies are insufficient given the complexities of ecosystem processes and the changes in precipitation patterns and sea level rise that are expected in the future. Improved flow policies need to be established that reflect the functional relationships between specific representative ecological resources and components of the natural flow regime across all relevant time scales. Similarly, flow policies need to be developed within a landscape scale to implicitly address the socio-ecological trade-offs as well as the complexities of water management. Multi-disciplinary collaborations will be essential for increasing our resiliency to anticipated future changes.

Wetlands↗
USGS2019

Morphology and genetics of Lythrum salicaria from latitudinal gradients of the Northern Hemisphere grown in cold and hot common gardens

The aim of this project was to compare the phenotypic responses of global populations of Lythrum salicaria in cold/dry and hot/humid environments to determine if phenotypic plasticity varied between the native and invasive ranges, and secondarily if this variation was linked to genetic diversity. Common garden studies were conducted in Třeboň, Czech Republic, and Lafayette, Louisiana, USA (cold/dry vs. hot/humid garden, respectively), using populations from latitudinal gradients in Eurasia and North America. Lythrum salicaria seeds collected from the same maternal plants across these latitudinal gradients were germinated and grown in Třeboň and Lafayette. Tissue masses (above-, below-ground, inflorescence and total) of these individuals were assessed at the end of each growing season (2006–2008). Worldwide field measurements of L . salicaria height were made by volunteers from 2004–2016. Biomass and height data were analyzed using the General Linear Model framework and multivariate techniques. Molecular markers (amplified fragment length polymorphisms) of individuals used in the common garden study were analyzed using traditional genetic diversity metrics and Bayesian clustering algorithms in STRUCTURE. Reaction norms were developed from differences in maternal plant responses in Třeboň versus Lafayette. In the common garden studies, stem/leaf, root and total biomass generally were highest for individuals grown from seeds collected in the southern part of the range in the cold garden, particularly by the third year of the study. In contrast, inflorescence biomass in the cold garden was higher by the third year in individuals from mid-latitude populations. As measured by volunteers, plants were taller in Eurasia than in North America moving from north to south with the pattern switching southward of 40°N latitude. Genetic diversity was similar between native and non-native invasive populations regardless of geographical origin of the seed and was not significantly different in the GLM Select model (p > 0.05). Reaction norm slopes showed that Eurasia had larger values than North America for reaction norms for above-ground and total biomass. Plants from the seeds of mother plants from Turkey had wide variation in total biomass when grown in Třeboň versus Lafayette; this variation in response within certain populations may have contributed to the lack of population-level differences in plasticity. These results indicate no loss of genetic diversity for L . salicaria during its North American invasion, nor reduction in plastic tissue allocation responses to a varying environment, which may help explain some of its invasive qualities and which could be of adaptive value under changing future environments.

PLoS ONE↗
USGS2019

Invasive plant species

Invasive species may be one of the worts environmental problems facing the conservation of natural areas, because of their role in changing ecosystem function. At the same time, invasive species cause much human suffering and economic loss. The approach to eliminating invasive species can be improved by a better understanding of the various types of invasive species, and the scientific hypotheses surrounding their ability to invade novel environments. Despite the billions of dollars spent each year, invasive species are difficult if not impossible to eliminate after they have established. Various methods of eliminating plant species from natural communities are described in this review. An increased understanding of the nature of invasive species including their genetic relationship to their progenitors, hypotheses regarding their invasive qualities, and effective approaches for their removal from ecosystems are all sorely needed. Volunteers can help in the invasive species effort by working on local plant/animal removal projects, reporting invasive species sightings to appropriate officials, or working with scientists to collect basic data for ecological research.

Book chapter↗
USGS2018

Introduction to the Wetland Book 1: Wetland structure and function, management, and nethods

The Wetland Book 1 is designed as a ‘first port-of-call’ reference work for information on the structure and functions of wetlands, current approaches to wetland management, and methods for researching and understanding wetlands. Contributions by experts summarize key concepts, orient the reader to the major issues, and support further research on such issues by individuals and multidisciplinary teams. The Wetland Book 1 is organized in three parts - Wetland structure and function; Wetland management ; and Wetland methods - each of which is divided into a number of thematic sections. Each section starts with one or more overview chapters, supported by chapters providing further information and case studies on different aspects of the theme.

Book chapter↗
USGS2018

Succession in ecological education

As complex and dynamic systems, wetlands offer the opportunity to investigate and incorporate the ecological concept of succession in educational settings. For example, the well-known, classic hydrosere concept is illustrated in numerous ecology and life-science textbooks. In this chapter, the drawbacks of using the hydrosere successional concept are assessed, and two examples of using wetlands to illustrate the process of succession for educational purposes are described. In each case, the premise and approach is that students best “learn ecology by doing ecology.”

Book chapter↗
USGS2018

Coastal estuaries and lagoons: The delicate balance at the edge of the sea

Coastal communities are increasingly concerned about the dynamic balance between freshwater and saltwater because of its implications for societal, economic, and ecological resources. While the mixing of freshwater and saltwater sources defines coastal estuaries and lagoons, sudden changes in this balance can have a large effect on critical ecosystems and infrastructure. Any change to the delivery of water from either source has the potential to affect the health of both humans and natural biota and also to damage coastal infrastructure. This fact sheet discusses the potential of major shifts in the dynamic freshwater-saltwater balance to alter the environment and coastal stability.

Fact Sheet↗
USGS2018

Wetlands in a changing climate: Science, policy and management

Part 1 of this review synthesizes recent research on status and climate vulnerability of freshwater and saltwater wetlands, and their contribution to addressing climate change (carbon cycle, adaptation, resilience). Peatlands and vegetated coastal wetlands are among the most carbon rich sinks on the planet sequestering approximately as much carbon as do global forest ecosystems. Estimates of the consequences of rising temperature on current wetland carbon storage and future carbon sequestration potential are summarized. We also demonstrate the need to prevent drying of wetlands and thawing of permafrost by disturbances and rising temperatures to protect wetland carbon stores and climate adaptation/resiliency ecosystem services. Preventing further wetland loss is found to be important in limiting future emissions to meet climate goals, but is seldom considered. In Part 2, the paper explores the policy and management realm from international to national, subnational and local levels to identify strategies and policies reflecting an integrated understanding of both wetland and climate change science. Specific recommendations are made to capture synergies between wetlands and carbon cycle management, adaptation and resiliency to further enable researchers, policy makers and practitioners to protect wetland carbon and climate adaptation/resiliency ecosystem services.

Wetlands↗
USGS2018

Effects of sediment application on Nyssa aquatica and Taxodium distichum saplings

The decline of Taxodium distichum forests along the Gulf Coast of North America is partly due to elevation loss and subsequent flooding. In many coastal wetlands, a common approach for coastal restoration is to rebuild elevation through the application of dredge material, but this technique has not been used widely in coastal forests due to concerns of negatively impacting trees. This experiment explored growth responses of Nyssa aquatica and T. distichum saplings to applications of low salinity dredge material (0.08 ± 0.001 ppt) in a greenhouse setting. Compared to controls, saplings of T. distichum grown in 7 and 15 cm sediment depths had greater final height, and increased stem and total biomass. In contrast, N. aquatica did not respond to sediment application. The absence of a negative response to sediment application in these two species indicates that dredge material application has the potential to improve the ecosystem health of sinking swamp forests by raising their elevation. We recommend that field trials applying sediment additions in coastal forests include careful monitoring of ecosystem responses, including seed bank expression, seedling regeneration, and root and canopy production.

Wetlands↗