Curtis Richardson

Duke University | DU · Division of Environmental Sciences and Policy

Peatlands represent large terrestrial carbon banks. Given that most peat accumulates in boreal regions, where low temperatures and water saturation preserve organic matter, the existence of peat in (sub)tropical regions remains enigmatic. Here we examined peat and plant chemistry across a latitudinal transect from the Arctic to the tropics. Near-su...

The southeastern US coastal plain was originally home to over one million ha of evergreen shrub bogs, locally known as pocosin. More than 70% have been drained for agriculture and forestry. These drained peatlands release GHGs to the atmosphere, mainly as CO2, which has resulted in significant concerns about their impact on climate change. Our long...

Peatlands drained for agriculture or forestry are susceptible to the rapid release of greenhouse gases (GHGs) through enhanced microbial decomposition and increased frequency of deep peat fires. We present evidence that rewetting drained subtropical wooded peatlands (STWPs) along the southeastern USA coast, primarily pocosin bogs, could prevent sig...

Peatlands are responsible for the majority of methane (CH4) emission from wetlands globally. Hydrological changes induced by climatic and anthropogenic disturbance may substantially alter CH4 emission in peatlands. Here we measured CH4 emission monthly for 1.5 years in natural, drained and restored shrub bogs in North Carolina, USA. Methane emissio...

PurposeWildfire, an increasing disturbance in peatlands, could dramatically change carbon stocks and reshape plant/microbial communities, with long-lasting effects on peatland functions. Soil fungi are important in controlling the belowground carbon and nutrient cycling in peatlands; however, the impact of altered fire regimes on these fungi is sti...

Peatlands have persisted as massive carbon sinks over millennia, even during past periods of climate change. The commonly accepted theory of abiotic controls (mainly anoxia and low temperature) over carbon decomposition cannot fully explain how vast low-latitude shrub/tree dominated (wooded) peatlands consistently accrete peat under warm and season...

Peatlands represent large terrestrial carbon banks. Given that most peat accumulates in boreal regions, where low temperatures and water saturation preserve organic matter, the existence of peat in (sub)tropical regions remains enigmatic. Here we examined peat and plant chemistry across a latitudinal transect from the Arctic to the tropics. Near-su...

Permafrost thawing may lead to the release of carbon and nitrogen in high-latitude regions of the Northern Hemisphere, mainly in the form of greenhouse gases. Our research aims to reveal the effects of permafrost thawing on CH4 and N2O emissions from peatlands in Xiaoxing’an Mountains, Northeast China. During four growing seasons (2011–2014), in si...

Purpose: Wildfire, an increasing disturbance in peatlands, could dramatically change carbon stocks and reshape plant/microbial communities, with long-lasting effects on peatland functions. Soil fungi are important in controlling the belowground carbon and nutrient cycling in peatlands; however, the impact of altered fire regimes on these fungi is s...

Worldwide, regularly recurring wildfires shape many peatland ecosystems to the extent that fire‐adapted species often dominate plant communities, suggesting that wildfire is an integral part of peatland ecology rather than an anomaly. The most destructive blazes are smoldering fires that are usually initiated in periods of drought and can combust e...

Peatlands have persisted over millennia as massive carbon sinks even during past periods of climate change. The commonly accepted theory of abiotic controls (mainly anoxia and low temperature) over carbon decomposition cannot explain how vast low-latitude wooded peatlands consistently accrete peat under warm and seasonally unsaturated conditions. S...

Many wetland systems worldwide struggle with high nutrient influx from urban and agricultural inputs that often disturbs ecosystem balance. In the Florida Everglades, concentrations above 15 μg P L⁻¹ have been shown to affect ecosystem balance and have long term effects on downstream periphyton, detritus, soil and macrophyte. Current Stormwater Tre...

Reliable predictions of the environmental fate and risk of engineered nanomaterials (ENMs) require a better understanding of ENM reactivity in complex, biologically active systems for chronic low-concentration exposure scenarios. Here, simulated freshwater wetland mesocosms were dosed with ENMs to assess how their reactivity and seasonal changes in...

Peatlands play a key role in the global carbon cycle, sequestering and releasing large amounts of carbon. Despite their importance, a reliable method for the quantification of peatland thickness and volume is still missing, particularly for peat deposits located in the tropics given their limited accessibility, and for scales of measurement represe...

Wetland ecosystems comprise only 3–5 percent of the world’s land surface, but their unique habitats and specialized and rare species have garnered the attention of biologists for centuries. The use of wetlands in Europe and Asia has a deep history, as draining peat bogs, marshes, mires, and swamps for fuel, timber, and agricultural crops was common...

The majority of annual sediment flux is transported during storm events in many watersheds across the world. Using X‐ray diffraction, we analyzed the mineralogy of grab samples of suspended sediment during different stages of storm hydrographs in the Southern Piedmont. Mineralogy of suspended sediment changes drastically from quartz‐dominated durin...

Typha is an iconic wetland plant found worldwide. Hybridization and anthropogenic disturbances have resulted in large increases in Typha abundance in wetland ecosystems throughout North America at a cost to native floral and faunal biodiversity. As demonstrated by three regional case studies, Typha is capable of rapidly colonizing habitats and form...

Increased dissolved reactive phosphorus (DRP) fluxes in the Maumee River in the Western Lake Erie watershed have been cited as a cause of recent hypoxia and toxic algal blooms in Western Lake Erie. Dissolved reactive P is operationally defined as the molybdate‐reactive P that passes through a 0.45‐μm filter. Unfortunately, this 0.45‐μm cutoff is no...

Recent research suggested that iron oxidation may protect carbon from drought-accelerated decomposition in wetlands by promoting the sorption of lignin derivatives and decreasing phenolic oxidase activities. Here we examined whether this mechanism exists in organic-rich peatlands, which store over 30% of the world's soil carbon, by simulating droug...

Limiting climate warming to <2°C requires increased mitigation efforts, including land stewardship, whose potential in the United States is poorly understood. We quantified the potential of natural climate solutions (NCS)—21 conservation, restoration, and improved land management interventions on natural and agricultural lands—to increase carbon st...

Trace metals associated with nanoparticles are known to possess reactivities that are different from their larger-size counterparts. However, the relative importance of small relative to large particles for the overall distribution and biouptake of these metals is not as well studied in complex environmental systems. Here, we have examined differen...

Despite the rapid rise in diversity and quantities of engineered nanomaterials produced, the impacts of these emerging contaminants on the structure and function of ecosystems have received little attention from ecologists. Moreover, little is known about how manufactured nanomaterials may interact with nutrient pollution in altering ecosystem prod...

During nanoparticle environmental exposure, presence in the water column is expected to dominate long distance transport as well as initial aquatic organism exposure. Much work has been done to understand potential ecological and toxicological effects of these particles. However, little has been done to date to understand the comparative persistenc...

Authigenic nanoparticles containing iron (Fe) and phosphorus (P) have been identified at the anoxic/oxic interface of various aquatic ecosystems, forming upon the oxidation of reduced Fe. Little is known about the prevalence of these authigenic nanoparticles in streams, their impact on biogeochemical fluxes, or the bioavailability of P associated w...

Particulate phosphorus (PP) is often the largest component of the total phosphorus (P) load in stormwater. Fine-resolution measurement of particle sizes allows us to investigate the mechanisms behind the removal of PP in stormwater wetlands, since the diameter of particles influences the settling velocity and the amount of sorbed P on a particle. I...

Tropical wetlands are thought to be the most important source of interannual variability in atmospheric methane (CH4) concentrations, yet sparse data prevents them from being incorporated into Earth system models. This problem is particularly pronounced in the neotropics where bottom-up models based on water table depth are incongruent with top-dow...

Methane emissions and dissolved methane in porewater at 10 to 15 cm depth from three sites at the CICRA Peatland in Madre de Dios, Peru. (XLSX)

Soil chemistry data from three sites at the CICRA in Madre de Dios, Peru. (XLSX)

The storage of coal combustion residue (CCR) in surface water impoundments may have an impact on nearby water quality and aquatic ecosystems. CCR contains leachable trace elements that can enter nearby waters through spills and monitored discharge. It is important, therefore, to understand their environmental fate in affected systems. This experime...

The Everglades is the largest subtropical wetlands in the United States. It has been designated an International Biosphere Reserve, a World Heritage Site, and a Wetland of International Importance, in recognition of its significance to all the people of the world. However, the Everglades have undergone radical changes in both water flow and water q...

Aquatic herbivores impose top-down control on the structure of wetland ecosystems, but the biogeochemical consequences of herbivory on methane (CH4) and nitrogen (N) are poorly known. To investigate the top-down effects of waterfowl on wetland biogeochemistry we implemented exclosure experiments in a major waterfowl overwintering wetland in the Sou...

Hydrologically controlled moist-soil impoundment wetlands provide critical habitat for high densities of migratory bird populations. Nutrients exported from heavily used impoundments by prescribed seasonal drawdown of surface water may contribute to the eutrophication of aquatic ecosystems. To investigate the relative importance of nutrient export...

Pocosins, an Algonquin Indian word means swamp-on-a- hill. These evergreen shrub-bog ecosystems occur on the southeastern coastal plain of the USA from Virginia to north Florida and once covered more than one million hectares in North Carolina alone. A broad definition of pocosins would include all shrub and forested bogs, as well as Atlantic white...

The Mesopotamian marshes of Iraq were once the largest wetland in the Middle East and home to an ancient civilization of Marsh Dwellers know as the Madan. By 2000, after massive drainage by the Iraqi government only 7 % remained. This environmental genocide resulted in the near extinction of numerous endemic species of birds and mammals as well as...

Static chambers used for sampling methane (CH4) in wetlands are highly sensitive to soil disturbance. Temporary compression around chambers during sampling can inflate the initial chamber CH4 headspace concentration and/or lead to generation of non-linear, unreliable flux estimates that must be discarded. In this study, we tested an often-used rubb...

Impounded and hydrologically managed ‘moist-soil’ wetlands built to support migratory bird populations have been overlooked as potential hotspots for methane (CH4) emission and nitrogen pollution. Through two years of field investigation we found that a moist-soil impoundment at Mattamuskeet National Wildlife Refuge in North Carolina emits more CH4...

Over the past several decades there has been a massive increase in coastal eutrophication, which is often caused by increased runoff input of nitrogen from landscape alterations. Peatlands, covering 3% of land area, have stored about 12–21% of global soil organic nitrogen (12–20 Pg N) around rivers, lakes and coasts over millennia and are now often...

The Everglades is the largest subtropical wetlands in the United States. It has been designated an International Biosphere Reserve, a World Heritage Site, and a Wetland of International Importance, in recognition of its significance to all the people of the world. However, the Everglades have undergone radical changes in both water flow and water q...

There is concern that widespread restoration and/or creation of freshwater wetlands may present a radiative forcing hazard because of the potential for methane (CH4) emissions. Yet data on greenhouse gas (GHG) emissions from restored wetlands are sparse and there has been little investigation into the GHG effects of amending wetland soils with orga...

Wetland habitats for migratory waterfowl provide a myriad of ecosystem services, but potentially represent a significant source of the greenhouse gas, methane (CH4). Remote sensing studies implicate freshwater wetlands of the neotropics as major contributors to global CH4, but field data remains insufficient to corroborate. Furthermore there is lit...

Herbivorous waterfowl exert consumptive control on aquatic vegetation, serve as nutrient vectors linking agricultural and wetland systems, and bioturbate wetland sediments. Yet there has been little investigation into how waterfowl influence the emissions of greenhouse gases from wetlands. We tested for the effects of waterfowl activity on methane...

Over millennia peatlands have stored 600–700 gigatonnes of carbon, which is close to the atmopheric carbon pool and exceeds that of global vegetation. The on-going climatic changes, especially drought and warming, are exposing peatlands to decreases in C sequestration or an increase in greenhouse gas fluxes loss or both , a critically situation wor...

Peatlands store one-third of global soil carbon 1. Drought/drainage coupled with climate warming present the main threat to these stores 1–4. Hence, understanding drought eeects and inherent feedbacks related to peat decomposition has been a primary global challenge 5,6. However, widely divergent results concerning drought in recent studies 3,7–11...

In the United States, aquatic mercury contamination originates from point and non-point sources to watersheds. Here, we studied the contribution of mercury in urban runoff derived from historically contaminated soils and the subsequent production of methylmercury in a stream-wetland complex (Durham, North Carolina), the receiving water of this runo...

Few studies have assessed whether restored streams and riparian floodplains support reference communi-ties of certain groups of freshwater organisms, such as turtles. This exploratory study compared turtle assemblages in six reference and six restored streams in the North Carolina Piedmont, which were assessed using standard trapping prac-tices wit...

Radiative forcing feedbacks from wetlands have been an important component of past climate change and will likely be so in the future, so accurately assessing the carbon (C) and radiative balances of wetlands remains an important research priority. This commentary shows that the paper by Mitsch et al. (Landscape Ecol 28:583–597, 2013) seriously und...

Earth System Models (ESMs) predict increased frequency of extreme wet and dry periods in the subtropics and tropics over the next century, resulting in uncertain carbon (C) budgets and greenhouse gases (GHG) fluxes. Globally, approximately 1/3 of peat stores are found in subtropical and tropical peatlands (STPs) formed from high-lignin woody biomas...

Background/Question/Methods It is well known that the frequency and magnitude of disturbance drive responses in aquatic ecosystems. With chemical contaminants prone to sequestration in sediments, a low concentration press-exposure may have greater long-term impacts than a high concentration pulse-exposure. One such class of contaminants are engin...

Climate change is predicted to impact river systems in the southeastern USA through alterations of temperature, patterns of precipitation and hydrology. Future climate scenarios for the southeastern USA predict (1) surface water temperatures will warm in concert with air temperature, (2) storm flows will increase and base flows will decrease, and (...

Peatlands store one third of global soil carbon. Drought/drainage coupled with climate warming presents a vital threat to those stores. Understanding drought effects and inherent feedbacks related to peat decomposition has been a major global challenge. Here, linking field and microcosm experiments, we show a previously unrecognized mechanism that...

Shifts in climate and land-use are important drivers of invasive species establishment in riparian ecosystems. Climate change will impact southeastern river systems by altering water temperature and hydrology. Such alterations will disturb floodplain plant communities making them more vulnerable to establishment of invasive species. Differential re...

Methane (CH₄) flux from freshwater wetlands has been linked to primary production and is greatly enhanced by the presence of aerenchymous emergent vegetation. Migratory waterfowl are capable of enhancing primary productivity by providing nutrient subsidies, and drastically altering the density and community structure of vegetation throug...

The use of antimicrobial silver nanoparticles (AgNPs) in consumer-products is rising. Much of these AgNPs are expected to enter the wastewater stream, with up to 10% of that eventually released as effluent into aquatic ecosystems with unknown ecological consequences. We examined the AgNP impacts on aquatic ecosystems by comparing the effects of two...

Fens represent a large array of ecosystem services, including the highest biodiversity found among wetlands, hydrological services, water purification and carbon sequestration. Land-use change and drainage has severely damaged or annihilated these services in many parts of North America and Europe; restoration plans are urgently needed at the lands...

Shrub/Tree and sedge/grass peatlands cover millions of hectares throughout the South Atlantic coast (SAC) that range from the Great Dismal Swamp in VA, through North Carolina, into the lower Atlantic coastal plain, the Okefenokee Swamp in Georgia, to the Cladium dominated Florida Everglades. These peatlands store about 1/5 of soil carbon in peatlan...

Over the past several decades there has been a massive increase in coastal eutrophication, especially along the north Atlantic coasts of North American and Europe, leading to widespread “dead zones” with cascading environmental consequences. Such eutrophication is often caused by increased nitrogen input. Peatlands, covering 3% of land area, store...

Background/Question/Methods Peatlands, covering 3% of land area, not only store one-third of all terrestrial soil carbon but also contain vast amounts of organic nitrogen, amounting to approximately 12-21% global soil N (12-20 Pg N). Generally, peatlands are important sinks of nitrogen with low mineralization rates because of waterlogged conditio...

Background/Question/Methods Natural peatlands are threatened by projected increases in prolonged droughts and increased temperatures according to recent IPCC models. Millions of hectares of former peatlands have also been drained and converted to agriculture and forestry in the U.S. However, while drought and drainage promotes the decomposition o...

We present the design for an innovative integrated stream and wetland restoration project recently constructed at the Duke University Wetland Center’s Stream and Wetland Assessment and Management Park (SWAMP) located in Durham, NC, USA. The design objective of this restored riparian system is to replicate the water quality functions occurring behin...

Addition of organic matter (OM) to created wetlands has been shown to increase soil C, N, P, microbial biomass and denitrification enzyme activity. But few studies have measured its impact on greenhouse gas fluxes. Our objective was to determine how emissions of CO2, CH4 and N2O vary with respect to different loading rates (0, 56, 112, 224 or 336 M...

Background & aims Plants may have dissimilar effects on ecosystem processes because they possess different attributes. Given increasing biodiversity losses, it is important to understand which plant traits are key drivers of ecosystem functions. To address this question, we studied the response of two ecosystem functions that remove nitrogen (N) fr...

Background: Variation in microbial metabolism poses one of the greatest current uncertainties in models of global carbon cycling, and is particularly poorly understood in soils. Biological Stoichiometry theory describes biochemical mechanisms linking metabolic rates with variation in the elemental composition of cells and organisms, and has been w...

Comparisons of microbial biomass C∶N∶P stoichiometric ratios with corresponding soil C∶N∶P stoichiometry. Relationships between microbial and soil stoichiometry are shown for A) C∶N ratios, B) C∶P ratios, and C) N∶P ratios. Soil and microbial stoichiometry were log10 transformed for normality. No regression fits are shown as none of these relations...

Contribution of soil C∶N and C∶P ratios to variation in N∶P ratios across global soils. Relationships of soil N∶P with A) soil C∶N and B) soil C∶P were determined seperately for only litter and humic horizons, and for all other soils exclusive of forest litter and humus. SMA fits for litter and humic horizons are shown with dotted black lines with...

Flow of included studies for used as data sources for the meta-analysis. (PDF)

Summary of SMA regressions of log10-transformed relationships among soil C and soil stoichiometry, paired analysis of soil stoichiometric ratios, and comparisons of soil and microbial stoichiometry. SMA regression fits for these relationships correspond with data presented in Figs. S1, S2, S3. Bivariate relationships were significant (P<0.001) for...

SMA parameter estimates for simultaneous fitting of microbial biomass C and P scaling relationships by land use and vegetation categories. Regression lines are compared by category in Fig. 3B, and data and regression fits are plotted by category in Fig. S4B. The simultaneous SMA relationships for microbial biomass C and P scaling were tested for di...

SMA parameter estimates for simultaneous fitting of microbial biomass C and P scaling relationships by climate categories. The simultaneous SMA relationships were tested for differences in intercepts (P<0.001) and slopes (P<0.001), and significantly different intercept and slope groups were determined by multiple comparisons in SMATR v.3.0, by cont...