Including Carbon Sequestration Research Articles

We need biosphere stewardship that protects carbon sinks and builds resilience

Earth’s biosphere, its extraordinary and complex web of species and ecosystems on land and in the oceans, drives the life-sustaining cycles of water and other materials that enable all life on Earth to thrive. The biosphere is also a principal driver of immense negative feedback loops in the Earth system that stabilize atmospheric CO2 concentrations and thereby global climate—including carbon sequestration by vegetation, soils, and the oceans. As such, Earth’s ecosystems have played a central role in keeping our planet’s climate system unusually stable throughout the last 11,700 years (i.e., the inter-glacial Holocene). During this epoch, global mean temperatures have oscillated only about 1 °C around the pre-industrial average, providing the unique conditions that allowed human civilizations to flourish. Today, ocean and land ecosystems remove around 50% of anthropogenic CO2 emissions from the atmosphere each year (1), an extraordinary biophysical feat, given that these emissions have risen from approximately 4 gigatonnes of carbon (GtC) per year in 1960 to around 11 GtC per year today. Put another way, half our “climate debt” is removed, for free, by the biosphere every year—a vast subsidy to the world economy. Safeguarding the biosphere from further degradation or collapse is an existential challenge for humanity. There are important steps we can take to contain the damage. Image credit: Shutterstock/Kritskiy-ua. The recent Working Group 1 report of the sixth assessment of the Intergovernmental Panel on Climate Change (IPCC) confirmed this major nature contribution to climate stability, estimating the cumulative carbon sequestration by land and oceans to be 56% of all human-caused emissions between 1850 and 2019 (2). All major global climate models whose simulations give us hope of meeting the target of the Paris Climate Agreement—to keep warming well below 2 °C—take the continued provision of this gigantic biosphere endowment for granted, merely … [↵][1]1To whom correspondence may be addressed. Email: johan.rockstrom{at}pik-potsdam.de. [1]: #xref-corresp-1-1

Seagrass contribution to blue carbon in a shallow karstic coastal area of the Gulf of Mexico.

Seagrass meadows provide multiple ecosystem services, including carbon sequestration. However, seagrass meadows are among the most threatened ecosystems worldwide. Determining the magnitude of the carbon stocks in seagrass meadows at the regional scale allows for the estimation of their global magnitude and identification of their importance in regional environmental mitigation strategies. The objective of the present study was to determine the structure of seagrass meadows in the Los Petenes Biosfera Reserve (LPBR) and evaluate their contributions to sinks of carbon in this system, located in Yucatan, which is considered the region with the largest seagrass extension in Mexico. Analyses of the seagrass meadows were executed following standardized protocols (spectral analysis, and isotope and carbon stock analyses). The LPBR stores an average of 2.2 ± 1.7 Mg C ha−1 in living biomass and 318 ± 215 Mg C ha−1 in sediment (top 1 m), and this carbon stock decreases with water depth. The seagrass community extends 149,613 ha, which represents the largest organic carbon stock (47 Tg C) documented in seagrass meadows in Mexico. Macroalgae and seagrass represent 76% of the organic carbon stored in sediment. If LPBR seagrass meadows are lost due to natural or anthropogenic impacts, 173 Tg CO2eqemissions could be released, which corresponds to the emissions generated by fossil fuel combustion of 27% of the current Mexican population. This information emphasizes the importance of seagrass meadows as a carbon sink in the region and their contribution to climate change mitigation, thus allowing for the implementation of necessary conservation strategies.

Approaches to delineate aggregates in intact soil using X-ray imaging

Soil structure refers to the spatial arrangement of primary soil particles and pores, and is known to influence a variety of soil functions including carbon sequestration and water holding capacity. At present, research in this field is often divided, focusing either on pores where pore networks are investigated in undisturbed soil or on solids where isolated soil aggregates are commonly studied. The choice of approach depends on the needs and traditions in different disciplines of soil science. While there is much debate regarding how well these viewpoints relate to each other, there have been only marginal research efforts undertaken to compare them quantitatively. In this study, we presented and evaluated methods to identify 3-D subunits in X-ray images of eight undisturbed soil samples that we interpreted as macroaggregates, and compared these to to results from drop-shatter tests. Here, we exploited the cohesive forces of water that induces shrinkage cracks under drying. Despite promising trends, comparisons between image and drop-shatter test derived aggregate properties remained inconclusive. Nevertheless, our results encourage further investigations on larger sample sets and different observation scales. The here presented and discussed aggregate delineation methods illustrate an approach to harmonize soil structure characterization in terms of both pore-networks and soil aggregation. For example, respective extended approaches may be developed to evaluate the locations of microaggregates within macroaggregates.

Global application of an unoccupied aerial vehicle photogrammetry protocol for predicting aboveground biomass in non-forest ecosystems.

Non‐forest ecosystems, dominated by shrubs, grasses and herbaceous plants, provide ecosystem services including carbon sequestration and forage for grazing, and are highly sensitive to climatic changes. Yet these ecosystems are poorly represented in remotely sensed biomass products and are undersampled by in situ monitoring. Current global change threats emphasize the need for new tools to capture biomass change in non‐forest ecosystems at appropriate scales. Here we developed and deployed a new protocol for photogrammetric height using unoccupied aerial vehicle (UAV) images to test its capability for delivering standardized measurements of biomass across a globally distributed field experiment. We assessed whether canopy height inferred from UAV photogrammetry allows the prediction of aboveground biomass (AGB) across low‐stature plant species by conducting 38 photogrammetric surveys over 741 harvested plots to sample 50 species. We found mean canopy height was strongly predictive of AGB across species, with a median adjusted R 2 of 0.87 (ranging from 0.46 to 0.99) and median prediction error from leave‐one‐out cross‐validation of 3.9%. Biomass per‐unit‐of‐height was similar within but different among, plant functional types. We found that photogrammetric reconstructions of canopy height were sensitive to wind speed but not sun elevation during surveys. We demonstrated that our photogrammetric approach produced generalizable measurements across growth forms and environmental settings and yielded accuracies as good as those obtained from in situ approaches. We demonstrate that using a standardized approach for UAV photogrammetry can deliver accurate AGB estimates across a wide range of dynamic and heterogeneous ecosystems. Many academic and land management institutions have the technical capacity to deploy these approaches over extents of 1–10 ha−1. Photogrammetric approaches could provide much‐needed information required to calibrate and validate the vegetation models and satellite‐derived biomass products that are essential to understand vulnerable and understudied non‐forested ecosystems around the globe.

Vermont’s Forests Provide Many Ecosystem Services Including Carbon Sequestration and Climate Change Mitigation

Photo 1: Vista from the top of the gondola in Smugglers Notch, Mt Mansfield State Forest, Vermont. This photograph captures just how vast Vermont’s forests are. Forests account for approximately 76% of Vermont’s land area, making it the fourth most heavily forested state in the United States. Given this, policymakers in the state have identified forests as an important tool in the fight against climate change. The goal of this research was to evaluate the mitigation potential of a range of forest management scenarios applied across the state. Photo credit: Emily Stephens. Photo 2: Overlooking Nichols Pond, in Woodbury, Vermont. In addition to carbon sequestration, Vermont’s forests provide many ecosystem services including aesthetic and economic values. Vermont is one of the ultimate fall foliage destinations in the United States, with over one million visitors traveling to Vermont in October alone to take in the picturesque landscapes ablaze with autumn colors. When considering implementation of forest management practices and policies to enhance carbon sequestration, it is critical to also consider the impacts on the other benefits these forests provide. Photo credit: Emily Stephens. Photo 3: Kayaking on Groton Lake first thing in the morning, Groton State Forest, Vermont. In this study, we evaluate practical ways to sustainably manage forests and their products to reduce greenhouse gas emissions. This report can serve to inform policymakers on potential biophysical responses of Vermont's forests to various management scenarios. If a goal is to integrate carbon sequestration into broader forest management objectives, it will be important to minimize trade-offs with other ecosystem services, such as the recreational opportunities, water quality, and wildlife habitat that the state’s forests provide. Photo credit: Emily Stephens. These photographs illustrate the article “Opportunities for Forest Sector Emissions Reductions: A state-level analysis” by Alexa J. Dugan, Jeremy W. Lichstein, Al Steele, Juha M. Metsaranta, Steven Bick, David Y. Hollinger published in Ecological Applications. https://doi.org/10.1002/eap.2327

Combined Application of Biochar and Lime Increases Maize Yield and Accelerates Carbon Loss from an Acidic Soil

Biochar, an ecologically friendly soil amendment, is suggested for large-scale field application for its multiple potential benefits, including carbon sequestration, crop yield improvement, and the abatement of greenhouse gas emissions. However, it is unknown how effective it is in changing soil properties and its associated yield improvement when biochar is co-applied with lime in acidic soil. Here, we examined the effects of two different biochars, i.e., rice husk biochar (RHB) and oil palm empty fruit bunches biochar (EFBB), and lime on nutrient availability, the yield of maize, and soil CO2 emission of acid soil. Biochars were applied at two different rates (10 and 15 t ha−1) in combination with two rates of lime (100% and 75%), while the recommended rate of NPK fertilizers, 100% lime, and without any amendments (control) were also included. Hybrid sweet corn was grown in pots with 20 kg soils for 75 days. Plant performance and soil analyses were performed before and after crop maize cultivation while CO2 emission was recorded. Compared to the control, combined RHB biochars with lime significantly buffered soil pH and increased nutrient availability (e.g., P by 137%), while reducing Al and Fe concentration at harvest. These changes in soil properties significantly increased maize yield (by 77.59%) and nutrient uptake compared to the control. Between the two biochars, RHB was relatively more effective in making these changes than EFBB. However, this treatment contributed to a greater carbon loss as CO2 (209% and 145% higher with RHB and EFBB) from soil than the control. We believe that biochar-mediated buffering of soil pH is responsible for this change. Our results suggest that combined biochar application could bring desirable changes in soil properties and increase crop performance, although these effects can be short-lived.

A Fused Radar–Optical Approach for Mapping Wetlands and Deepwaters of the Mid–Atlantic and Gulf Coast Regions of the United States

Tidal wetlands are critically important ecosystems that provide ecosystem services including carbon sequestration, storm surge mitigation, water filtration, and wildlife habitat provision while supporting high levels of biodiversity. Despite their importance, monitoring these systems over large scales remains challenging due to difficulties in obtaining extensive up-to-date ground surveys and the need for high spatial and temporal resolution satellite imagery for effective space-borne monitoring. In this study, we developed methodologies to advance the monitoring of tidal marshes and adjacent deepwaters in the Mid-Atlantic and Gulf Coast United States. We combined Sentinel-1 SAR and Landsat 8 optical imagery to classify marshes and open water in both regions, with user’s and producer’s accuracies exceeding 89%. This methodology enables the assessment of marsh loss through conversion to open water at an annual resolution. We used time-series Sentinel-1 imagery to classify persistent and non-persistent marsh vegetation with greater than 93% accuracy. Non-persistent marsh vegetation serves as an indicator of salinity regimes in tidal wetlands. Additionally, we mapped two invasive species: wetlands invasive Phragmites australis (common reed) with greater than 80% accuracy and deepwater invasive Trapa natans (water chestnut) with greater than 96% accuracy. These results have important implications for improved monitoring and management of coastal wetlands ecosystems.

Old-growth attributes in a maturing secondary Indiana state forest: an opportunity for balanced management1

Primary old-growth forests are rare in the state of Indiana and are found only in small, isolated patches of nature preserves. Recent research underscores the values of large tracts of secondary old-growth (referred to in this paper as “older” forests), including carbon sequestration, forest resiliency, mitigation of climate change impacts, and conservation of biological diversity. Due to historical management, many portions of Indiana state forests are maturing, and yet the “older” successional stage is underrepresented. One of these maturing forests, the site of our study, is in south-central Indiana within the Back Country Area (BCA) of the Morgan-Monroe/Yellowwood State Forest (two state forests, herein called a complex, including parcels in three counties with the largest block of forests spanning Brown and Monroe counties). Our study of the forest structure of the BCA addresses the following questions: (a) Is this mature forest developing ecological attributes of old-growth forests, thus making it a good candidate for an older forest reserve? (b) Does this forest support the plant community characteristic of natural areas of Indiana? We analyzed forest stand metrics, coarse woody debris and snags, age of the largest live trees, and the floristic quality of the herbaceous layer. We then compared these data with published accounts from Indiana nature preserves. Metrics such as tree basal area, number of large-diameter trees, and number of snags are within the range of those measured in existing old-growth forests of Indiana. Analysis of tree cores and log cross-sections shows that 78% of the sample trees were over 100 yr old, with 24% over 130 yr, which is also comparable to old-growth forest nature preserves in the state. The metrics of the Floristic Quality Assessment of the broader plant community of the BCA are comparable to or higher than the metrics from published assessments of Indiana nature preserves. Collectively, the attributes measured indicate that the BCA supports a maturing secondary forest with old-growth characteristics. In the absence of further timber harvest, the BCA as a reserve could reach older forest status within 50 yr. Our study demonstrates that the BCA forest is a prime candidate for an older forest reserve. This study of the BCA could also serve as a model for future assessments of potential older forest reserves in other state forests. Reserves of older forests free from harvest are not incompatible with other management goals and can be a valuable part of a broader-scale management plan. These forest reserves should be promoted across the state to increase the representation within Indiana's state forest system of late-successional secondary forest exhibiting ecological attributes of old-growth forests, thereby enhancing the role of state forests in biodiversity protection and climate mitigation.

Multilevel modelling of impacts of human and natural factors on ecosystem services change in an oasis, Northwest China

Clarifying driving mechanisms of ecosystem services changes is key to sustainable ecosystem management. This study evaluated three key ecosystem services, including carbon sequestration (proxied by net primary production, NPP), water yield, and soil conservation in Zhanyge during 1990-2015, and applied multilevel modeling to examine the impacts of sub-watershed level natural factors and county level human factors on ecosystem services changes. The results showed the ecological vulnerable Qilian mountain area possessed high values of these ecosystem services. During 1990-2015, NPP and water yield increased, and soil conservation decreased. Results of the multilevel models indicated that natural and human factors drove ecosystem service changes in various degrees and directions and it was necessary to consider the scale dependence of the driving factors at different levels. Particularly, forest land, grassland and cultivated land expansion led to increase of NPP, water yield and soil conservation, grain productivity and agricultural machinery level had negative effects on water yield, while had positive impacts on soil conservation. Overall, it is necessary to strengthen ecological protection in the Qilian mountain area and strictly control cultivated land expansion balance to maintain sustainable development of ecosystem with comprehensively considering the effects of driving factors and local conditions.

Hydrologic and geomechanical characterization of deep sedimentary rocks and basement for safe carbon sequestration in the Cook Inlet Basin, Alaska

Understanding the hydrologic and geomechanical properties of sedimentary rocks and the underlying basement is important for the success of fluid extraction and injection operations, including carbon sequestration. This study analyzes the hydrologic and geomechanical properties of the reservoir (Hemlock Formation), overlying confining unit (Tyonek Formation), and underlying confining unit/basement (Talkeetna volcanics and Mesozoic igneous intrusive - diorite). This study shows the potential of fault slip due to carbon sequestration in the Cook Inlet basin of Alaska. We integrate core, well-log, and 3D seismic data to perform hydrologic and geomechanical analysis of the deep sedimentary formations, basement, and simulation of the fault slip potential (FSP). The FSP results show that faults have the potential to slip, depending on several factors, such as the local in-situ stress conditions, pore pressure, and CO2 injection rate. The azimuth of the maximum horizontal stress (σH) with respect to fault orientation is a critical factor for fault stability in the Cook Inlet basin.

Rock Water as a Key Resource for Patchy Ecosystems on Shallow Soils: Digging Deep Tree Clumps Subsidize Surrounding Surficial Grass

AbstractMediterranean mountainous areas of shallow soil often display a mosaic of tree clumps surrounded by grass. The combined role and dynamics of water extracted from the underlying rock, and the competition between adjacent patches of trees and grass, has not been investigated. We quantified the role rock water plays in the seasonal dynamics of evapotranspiration (ET), over a patchy landscape in the context of current and past seasonal climate changes, and land‐cover change strategies. Soil water budget suggests deep water uptake by roots of trees (0.8–0.9 mm/d), penetrating into the fractured basalt, subsidized grass transpiration in spring through hydraulic redistribution. However, in summer trees used all the rock water absorbed (0.79 mm/d). A 15‐year data set shows that, with increasing seasonal drought‐severity (potential ET/precipitation) to >1.04, the vertical water flux through the bottom of the thin soil layer transitions from drainage to uptake in support of ET. A hypothetical grass‐covered landscape, with no access to deep water, would require 0.68–0.85 mm/d more than is available, forcing shortened growing season and/or reduced leaf area. Long‐term decreasing winter precipitation and increasing spring potential ET suggest drying climate, so far with stable vegetation mosaic but progressively earlier peak of grass leaf area. Intervention policies to increase water yield by reducing tree cover will curtail grass access to rock moisture, while attempting to increase tree‐related products (including carbon sequestration) by increasing forest cover will limit water availability per tree leaf area. Both changes may further reduce ecosystem stability.

The impact of land-use legacies and recent management on natural disturbance susceptibility in mountain forests

Mountain forests provide a wide range of ecosystem services, including carbon sequestration and protection from natural hazards. Forest cover in the European Alps has increased over the last century, but in recent years, these forests have experienced an increasing rate of natural disturbances by agents such as windthrow, bark beetle outbreaks, and forest fires. These disturbances pose a challenge for forest management, making it important to understand how site and stand characteristics, land use legacies and recent management influence disturbance probability. We combined a dataset of forest disturbances detected from space with in-situ forest management records, allowing us to differentiate between different types of disturbances for the Canton of Graubünden, Switzerland, in the years 2005–2018. The resulting dataset of over 28′000 attributed disturbance patches (corresponding to a disturbed forest area of ca. 23′600 ha) was combined with information on topography, forest structure, and historical forest cover. A machine-learning approach was used to investigate the non-linear and interacting relationships between potential drivers and disturbance occurrence. Natural disturbances (especially windthrow and bark beetle outbreaks) were most common at lower elevations, on shallow and south-facing slopes, and in even-aged, spruce-dominated stands with a closed canopy. Forests established in the 20th century were significantly more susceptible to natural disturbances than forests that were already present before 1880, which may be due to the uniform age and vertical structure of secondary forests, as well as legacy effects of former agricultural use. On the other hand, forest management more often took place in forests present before 1880. Management interventions (such as thinning) in turn increased the susceptibility to natural disturbances in the short term. This finding emphasizes the need to balance short-term increases in disturbance susceptibility with long-term benefits in forest resilience when planning management interventions in mountain forests. Our findings highlight the importance of considering multiple interactive drivers, including management and land-use history, for understanding forest disturbance regimes.

Mariculture research of Macrocystis pyrifera and Saccharina latissima in Southeast Alaska

AbstractThere has been increasing interest in Alaska regarding the commercial mariculture of kelp. Kelp farming can be an economic engine for coastal communities of Alaska. Other benefits include ecosystem services, including carbon sequestration and mitigation of eutrophication. In support of this interest, several kelp species have been examined for commercial potential. In the 1980s–1990s, experiments were performed on the giant kelp Macrocystis pyrifera. Female gametophytes were exposed to varying levels of chelated iron. Relatively low levels of chelated iron (1–5 μM) stimulated the onset of oogenesis. In contrast, higher iron concentrations inhibited egg production. Outplant experiments with Macrocystis in Sitka, AK showed growth in the winter and spring, slowing down to zero growth by the end of summer. Fertilizing outplants in August allowed plants to survive and grow during the ensuing winter. Mariculture experiments with Saccharina latissima carried out near Juneau, Alaska showed exponential growth for seeded lines set out from September to March. Optimal growth occurred for outplants in October–November, with growth rates of up to 5% per day. The best growth occurred when lines were 2–3 m below the surface. Growth rates declined in May–June corresponding to a decrease in inorganic nitrogen in the water. Slower growth also resulted in severe fouling.

Controls on soil microbial carbon use efficiency over long-term ecosystem development

Carbon use efficiency—the proportion of substrate carbon that is converted to microbial biomass—is an important control on many ecosystem properties including carbon sequestration and nutrient cycling. Although CUE varies widely across terrestrial ecosystems, a coherent understanding of edaphic controls on CUE is lacking, thereby limiting the accuracy of global carbon models. The objective of this study was to determine how microbial CUE changes with long-term soil development and nutrient availability. Soil was collected across the chronosequence and fertility gradient at Jug Handle State Natural Reserve (the “Ecological Staircase”) in Mendocino County, CA. These soils exhibit a range in pH (3.29–6.59), litter quantity and quality (litter C:N, 32–70), and clay content (14.13–87.30%), while other factors such as modern-day climate, potential biota, and parent material are common to all sites. CUE varied significantly with soil and ecosystem development; the relationship was unimodal over geological time with CUE peaking at intermediate aged soils. Soil organic matter (SOM) content and pH were the most important variables each accounting for 30% of the variation in CUE across sites. Soil pH had a quadratic relationship with CUE, peaking at pH 4.7. Litter carbon to phosphorus (C:P) and nitrogen to phosphorus (N:P) ratios were also significant factors (Pearson’s r = 0.57 and 0.39 respectively). These results demonstrate that CUE changes in complex ways with soil fertility and long-term ecosystem development, and that edaphic factors such as SOM, pH, and litter quality need to be taken into account when predicting CUE for a given system.

Large-Scale High-Resolution Coastal Mangrove Forests Mapping Across West Africa With Machine Learning Ensemble and Satellite Big Data

Coastal mangrove forests provide important ecosystem goods and services, including carbon sequestration, biodiversity conservation, and hazard mitigation. However, they are being destroyed at an alarming rate by human activities. To characterize mangrove forest changes, evaluate their impacts, and support relevant protection and restoration decision making, accurate and up-to-date mangrove extent mapping at large spatial scales is essential. Available large-scale mangrove extent data products use a single machine learning method commonly with 30 m Landsat imagery, and significant inconsistencies remain among these data products. With huge amounts of satellite data involved and the heterogeneity of land surface characteristics across large geographic areas, finding the most suitable method for large-scale high-resolution mangrove mapping is a challenge. The objective of this study is to evaluate the performance of a machine learning ensemble for mangrove forest mapping at 20 m spatial resolution across West Africa using Sentinel-2 (optical) and Sentinel-1 (radar) imagery. The machine learning ensemble integrates three commonly used machine learning methods in land cover and land use mapping, including Random Forest (RF), Gradient Boosting Machine (GBM), and Neural Network (NN). The cloud-based big geospatial data processing platform Google Earth Engine (GEE) was used for pre-processing Sentinel-2 and Sentinel-1 data. Extensive validation has demonstrated that the machine learning ensemble can generate mangrove extent maps at high accuracies for all study regions in West Africa (92%–99% Producer’s Accuracy, 98%–100% User’s Accuracy, 95%–99% Overall Accuracy). This is the first-time that mangrove extent has been mapped at a 20 m spatial resolution across West Africa. The machine learning ensemble has the potential to be applied to other regions of the world and is therefore capable of producing high-resolution mangrove extent maps at global scales periodically.

Biochar for sustainable soil management

Biochar for sustainable soil management

Chlorella vulgaris as a Model Organism for Microgravity Cultivation in a CubeSat

Chlorella vulgaris is one of the most common and characterized algae genus with several applications, including carbon sequestration, biofuel, food production and wastewater treatment. Chlorella sp. are considered suitable to be used as model organisms in space research due to their cultivation flexibility. Many studies have been carried out to ensure better conditions for supporting human life on long-term missions in deep space or on planetary surfaces, minimizing the need for resupplies. Regardless of the resilience of the genus Chlorella to space conditions has already been demonstrated, model organisms are useful in the improvement of new technologies. This research aimed to develop the culture conditions and a monitoring system for C. vulgaris, under microgravity, using an image capture device for CubeSats. The image acquisition system consisted of a digital microscope, with remote access, a Single Board Computer, a monitoring computer, and an image processing algorithm. Three microalgae colonies, under laboratory conditions, were evaluated in real time (every 30 minutes) using the size of the colonies as a parameter for evaluating growth rates. The highest microalgae biomass production for the three monitored colonies (C1-C3) was: increase of 28% for C1 after 90 h; 21% for C2 after 84 h; and 36% for C3 after 120 h. The results indicated that the system was able to monitor the growth of microalgae colonies. A specific support is being developed, which allows the installation of this image acquisition system for algae cultivation in a CubeSat, for future studies of algae growth in real microgravity conditions.

Integrated phytomanagement of a carbon tetrachloride-contaminated site in Murdock, Nebraska (USA)

The application of a large-scale ( ca . 59,000 m 2 ) integrated phytomanagement system at a carbon tetrachloride (CCl 4 )-impacted site at Murdock, Nebraska, USA, was assessed in terms of its effectiveness in mitigating site risk, and realizing wider social and environmental benefits. Volatile Organic Compound (VOCs) concentrations (including CCl 4 ) measured in surface water, groundwater, air and vegetation samples show that the Murdock system has achieved effective risk management over the 10+ year period since its implementation, with the phytomanagement component of the remediation system (consisting of a mixed stand of dominantly Niobe willow ( Salix x ‘Niobe’ ) and Eastern Cottonwood ( Populus deltoides )) removing 300g–600g of CCl 4 annually. Eastern Cottonwood played an increasing role in CCl 4 removal over time, from 55% of the total mass removal in 2008 to 69% in 2014. Using a site design focused on enhancement of the social and physical environment, in addition to risk mitigation, has enabled realization of a range of wider social and environmental benefits, which include carbon sequestration of ca. 77 tons CO 2 /ha/y, and educational and recreational benefits. The phytomanagement system applied at Murdock has incurred significant installation, and on-going monitoring and maintenance, effort and costs (exceeding $1.5 million) highlighting the importance of (a) sustained stakeholder engagement to ensure continued local community support, and (b) effective site design to realize as full a range of core (i.e. risk mitigation) and wider benefits as possible, to increase the overall value proposition of such schemes. • Large-scale phytomanagement was successfully applied at a CCl 4 -impacted site. • Effective risk management has been achieved over the 10+ years since implementation. • Ca. 300g–600g CCl 4 has been removed annually via plant uptake and translocation. • Effective design can realize significant socio-economic and environmental benefit.

Microbiome and nitrate removal processes by microorganisms on the ancient Preah Vihear temple of Cambodia revealed by metagenomics and N-15 isotope analyses

Preah Vihear temple is one of the most significant representatives of the ancient Angkorian temples listed as United Nations Educational, Scientific and Cultural Organization (UNESCO) World Heritage Sites. The surfaces of this Angkor sandstone monument are covered with deteriorated materials, broadly called "sediments" here, resulting from a long time of weathering of the sandstone. The sediments might adversely affect the ancient sandstone substratum of this cultural heritage, and the potential risk from them is essential information for current strategies and on-going protection and management. The extracted DNA from the sediment samples of this temple was used for Illumina high-throughput sequencing analysis, resulting in approximately 12 Gb of metagenomic dataset. The results of this shotgun metagenomic analysis provided a thorough information of the phylogenetic groups presented in the microbiome of the sediment samples, indicating that potential metabolic activities, involving different geomicrobiological cycles, may occur in this microbiome. The phylogenetic result revealed that the majority of metagenomic reads were affiliated with Proteobacteria, Acidobacteria, Actinobacteria, and Bacteroidetes at the phylum level. The metabolic reconstruction results indicated that the important geomicrobiological cycling processes include carbon sequestration, and nitrogen and sulfur transformation as the potentially active ones in the sediments of the sampling sites. Specifically, the dissimilatory nitrate reduction to ammonium (DNRA) and the newly discovered complete ammonia oxidation (comammox) were retrieved from this metagenomic dataset. Furthermore, the genetic information on the presence of acid-producing processes by sulfur- and ammonia-oxidizing bacteria and archaea in this metagenomic dataset suggested that the microbial flora in these samples has the potential to participate in the degradation of sandstone cultural heritage by producing acids. N-15 isotope amendment and incubation analysis results confirmed the presence of active denitrification, but not anammox activity at this temple. These results are important for our knowledge on the microbial community composition and microbial biodeterioration processes affecting this sandstone cultural heritage and will aid in the protection and management of the ancient Preah Vihear temple.Key Points• Microbiota on Preah Viher temple was analyzed using NGS.• Nitrate-N transformation by DNRA, comammox, and denitrifcation was detected.• N-15 isotope analysis confirmed the active denitrifcation, but not Anammox.• Accumulation of nitrate is a result of less active removal by denitrification.

Ungrazed salt marsh has well connected soil pores and less dense sediment compared with grazed salt marsh: a CT scanning study

Salt marshes provide various ecosystem functions and services including flooding protection, wildlife habitats, and carbon storage. These functions and services could, however, be strongly impacted by anthropogenic activities such as livestock grazing – a common practice in the Wadden Sea salt marshes located in North west of Europe. To assess the impact of grazing on soil parameters, a total number of eight soil cores (⌀: 18 cm; L: 50 cm) were collected in areas with and without livestock grazing, and scanned using a Computed Tomography (CT) to characterize soil parameters including soil macroporosity, sediment density, and pores connectivity. Subsequently, sub-samples were taken for determination of soil moisture content (%) and bulk density (g cm−3). To account for the impact of grazing on soil drainage after tidal inundations, water table relative to soil surface was monitored during two flooding events. Our results demonstrated that grazed salt marsh has higher top-soil bulk density, and lower macroporosity and pore connectivity, than ungrazed marsh, due to soil compaction by livestock grazing. Moreover, grazed marsh has slower water drainage and that might keep the soil waterlogged for a longer period of time which has implications on lowering decomposition rate due to lower soil redox. This study provides evidence that grazing alters physical soil parameters in salt marsh. Consequently, grazing needs to be accounted for when evaluating how land use impacts ecosystem services and functions including carbon sequestration.