Southern Flow Corridor effectiveness monitoring, 2015-2017: Blue carbon and sediment accretion
Abstract and Figures
This report provides the results of ecosystem restoration effectiveness monitoring conducted by our team during 2015-2017 at the Southern Flow Corridor Landowner Preferred Alternative (hereafter, "SFC") project site and reference sites. This report describes two main monitoring activities: 1) measurements of sediment accretion using feldspar marker horizon plots and sediment stakes, and 2) collection of deep soil cores to determine "blue carbon" sequestration rates. In addition to the monitoring described in this report, other monitoring conducted by our team at the SFC site and reference sites includes baseline monitoring conducted during 2013-2014 (reported in Brown et al. 2016); and year 2 post-restoration monitoring conducted during 2017-2018 (reported in Janousek et al. 2021). The overall monitoring program is described in the SFC Effectiveness Monitoring Plan (Brophy and van de Wetering 2014).
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... While supporting infrastructure has been installed (e.g., scour protection aprons between the road and river edge), those features are beginning to fail and there is significant deterioration of older road segments (Tillamook Estuary Partnership (TEP), 2022). Flood risk in Tillamook is increasing, and projections include increased erosion that could increase damages and costs to properties and structures (Komar et al., 2004;Oregon Department of Fish and Wildlife (ODFW), 2006;Brophy et al., 2019b). The TEP team recognized that there were multiple stakeholders for the TRW Restoration project with diverse benefits, and interests beyond the need to reduce and mitigate flooding. ...
Framing ecological restoration and monitoring goals from a human benefits perspective (i.e., ecosystem services) can help inform restoration planners, surrounding communities, and relevant stakeholders about the direct benefits they may obtain from a specific restoration project. We used a case study of tidal wetland restoration in the Tillamook River watershed in Oregon, USA, to demonstrate how to identify and integrate community stakeholders/beneficiaries and the environmental attributes they use to inform the design of and enhance environmental benefits from ecological restoration. Using the U.S. Environmental Protection Agency’s Final Ecosystem Goods and Services (FEGS) Scoping Tool, we quantify the types of ecosystem services of greatest common value to stakeholders/beneficiaries that lead to desired benefits that contribute to their well-being in the context of planned uses that can be incorporated into the restoration project. This case study identified priority stakeholders, beneficiaries, and environmental attributes of interest to inform restoration goal selection. This novel decision context application of the FEGS Scoping Tool also included an effort focused on how to communicate the connections between stakeholders, and the environmental attributes of greatest interest to them using heat maps.
... Deep A horizons are a common feature of grasslands, but they, like other terrestrial ecosystems, typically have relatively low rates of soil C sequestration, particularly compared with marineinfluenced wetlands (Mcleod et al., 2011;Schlesinger, 1990;Schlesinger & Amundson, 2018). Other former estuarine wetlands in Oregon that are diked and in agricultural use can have substantial rates of soil C accumulation, presumably because of periodic overtopping of the dikes and associated sedimentation (Brophy et al., 2017(Brophy et al., , 2018. However, the landowner has only observed one brief (<1 h) and spatially limited (∼30 m) episode of tidal overtopping of the dike in over 20 yr (L. ...
Restoring coastal wetland habitats is important for returning many ecosystem services. However, very little is known about whether these restoration events return soil microbial functions and C storage to reference‐level capacity. We compared soil microbial function (microbial enzyme activity, catabolic responses to C substrates, CH4 and CO2 gas production) and soil C storage attributes (percent C, bulk density, and C density) in disturbed, restored, and reference wetlands in freshwater and saline coastal Oregon wetland complexes. We found that diking and draining fresh and saline wetlands can cause significant decreases in historic sediment C pools, but that restoration can return the capacity for C sequestration. We also found that restoration partially returned physicochemical soil properties and microbial functions to reference levels in freshwater wetlands, indicating a trajectory of recovery of ecosystem function. However, this trajectory was less discernable in the saline wetland complex where the restored marsh was an unvegetated mudflat and will likely require decades to millennia to succeed to the high‐marsh characteristics of the reference marsh, suggesting that filling subsided restored sites to elevations typical of intact salt marshes may more quickly return soil ecosystem function.
A summary of the current understanding of the climate mitigation potential of Oregon’s coastal and marine habitats (October 2022).
This study identified and characterized 6035 ac of current and likely former tidal wetlands in the emergent, shrub, and forested classes in the Tillamook Bay estuary, Oregon, USA, divided the wetlands into 92 “sites” suitable for action planning purposes, and used ecological criteria to prioritize the sites for conservation and restoration activities. The project is intended for use in strategic planning of voluntary conservation and restoration efforts; products are not intended for regulatory use.
Estuarine habitat restoration is a top priority for U.S. coastal regions. However, many projects fail or cannot be evaluated, in part because of a lack of reference conditions datasets from least-disturbed sites to guide restoration design, evaluation, and adaptive management (National Research Council 2001). In the Pacific Northwest, region-wide reference datasets on physical and biological attributes are lacking for the tidal wetland habitats that are the most likely target of restoration (e.g., emergent, scrub-shrub and forested intertidal wetlands). This data gap is caused in part by the high costs and limited accuracy of available methods for monitoring key habitat drivers. This project addressed these constraints by developing and evaluating the following tools:
1) A restoration practitioner survey which gathered input from active practitioners on data gaps, monitoring practices and restoration priorities. These results offer important guidance for research, outreach and education.
2) A temperature sensor method for generating spatially explicit data on tidal inundation regime, a major ecosystem driver in estuarine wetlands.
3) A reference conditions database developed from key physical and biological characteristics measured at six least-disturbed (unimpacted) estuarine wetlands in Oregon. Other sites are being added to the database, and practitioners are actively using the data to improve design, evaluation and management of tidal wetland restoration projects in Oregon and the Pacific Northwest.
4) A web portal (http://oregonexplorer.info), which provides restoration practitioners with easy access to reference conditions data and metadata.
The results represent substantial improvements over existing technologies, and have broad applicability.
To obtain geospatial data from this project, scroll to the bottom of the following web page: https://ir.library.oregonstate.edu/concern/datasets/zw12zb20h
This project mapped potential future tidal wetlands (known as "Landward Migration Zones" or "LMZs") for 23 estuaries on the coast of Oregon, USA south of the Columbia River. The mapped LMZs are at appropriate elevations to support vegetated tidal wetlands, but may currently lack a connection to tidal waters (e.g. they might be behind a dike or tide gate). Mapping these areas helped identify lands vulnerable to SLR. This project used an elevation-based method (modified bathtub method) to map current and future tidal wetlands. Elevation was obtained from LIDAR; projected SLR was obtained from recent, authoritative, and region-specific scientific literature. LMZs were modeled for six SLR scenarios that could be expected between the date of the study (2017) and the year 2160, but this study did not assume any specific timeframe for the scenarios modeled. Both lower and upper boundaries for LMZs were mapped, to allow estimation of areas that would be lost due to conversion from vegetated tidal wetland to mudflat under each SLR scenario.
We used a first-of-its-kind comprehensive scenario approach to evaluate both the vertical and horizontal response of tidal wetlands to projected changes in the rate of sea-level rise (SLR) across 14 estuaries along the Pacific coast of the continental United States. Throughout the U.S. Pacific region, we found that tidal wetlands are highly vulnerable to end-of-century submergence, with resulting extensive loss of habitat. Using higher-range SLR scenarios, all high and middle marsh habitats were lost, with 83% of current tidal wetlands transitioning to unvegetated habitats by 2110. The wetland area lost was greater in California and Oregon (100%) but still severe in Washington, with 68% submerged by the end of the century. The only wetland habitat remaining at the end of the century was low marsh under higher-range SLR rates. Tidal wetland loss was also likely under more conservative SLR scenarios, including loss of 95% of high marsh and 60% of middle marsh habitats by the end of the century. Horizontal migration of most wetlands was constrained by coastal development or steep topography, with just two wetland sites having sufficient upland space for migration and the possibility for nearly 1:1 replacement, making SLR threats particularly high in this region and generally undocumented. With low vertical accretion rates and little upland migration space, Pacific coast tidal wetlands are at imminent risk of submergence with projected rates of rapid SLR.
Coastal marshes are considered to be among the most valuable and vulnerable ecosystems on Earth, where the imminent loss of ecosystem services is a feared consequence of sea level rise. However, we show with a meta-analysis that global measurements of marsh elevation change indicate that marshes are generally building at rates similar to or exceeding historical sea level rise, and that process-based models predict survival under a wide range of future sea level scenarios. We argue that marsh vulnerability tends to be overstated because assessment methods often fail to consider biophysical feedback processes known to accelerate soil building with sea level rise, and the potential for marshes to migrate inland.
Tidal wetlands are highly sensitive to processes that affect their elevation relative to sea level. The surface elevation table–marker horizon (SET–MH) method has been used to successfully measure these processes, including sediment accretion, changes in relative elevation, and shallow soil processes (subsidence and expansion due to root production). The SET–MH method is capable of measuring changes at very high resolution (±millimeters) and has been used worldwide both in natural wetlands and under experimental conditions. Marker horizons are typically deployed using feldspar over 50-by 50-cm plots, with replicate plots at each sampling location. Plots are sampled using a liquid N 2 cryocorer that freezes a small sample, allowing the handling and measurement of soft and easily compressed soils with minimal compaction. The SET instrument is a portable device that is attached to a permanent benchmark to make high-precision measurements of wetland surface elevation. The SET instrument has evolved substantially in recent decades, and the current rod SET (RSET) is widely used. For the RSET, a 15-mm-diameter stainless steel rod is pounded into the ground until substantial resistance is achieved to establish a benchmark. The SET instrument is attached to the benchmark and leveled such that it reoccupies the same reference plane in space, and pins lowered from the instrument repeatedly measure the same point on the soil surface. Changes in the height of the lowered pins reflect changes in the soil surface. Permanent or temporary platforms provide access to SET and MH locations without disturbing the wetland surface. Abbreviations: MH, marker horizon; PVC, polyvinyl chloride; RSET, rod surface elevation table; SET, surface elevation table.
The Pacific Northwest has few wetlands, many of which have been lost since European settlement. As a result, state and national policy has the goal of no overall net loss of the nation's remaining wetlands base, as defined by acreage and function. However, techniques and results of restoration and creation methods used to achieve "no net loss' are often unsuccessful. Nevertheless, salt marsh restoration was attempted in the Salmon River estuary by breaching dikes that enclosed a pasture, resulting in changes in wetland characteristics that are described. Some guidelines are developed and explanations given to aid wetland managers in carrying out successful coastal salt marsh restoration actions. -Authors
(1) Holme Post is a firm datum near the western margin of the East Anglian Fenlands from which the lowering of the peat surface throughout 130 years of drainage has been registered. A detailed account of this unique record of peat wastage, and its relationship to the land-drainage measures which have chiefly controlled it, is presented. (2) After a discussion of the origin and founding of the Post, the relevant drainage history is described. Four stages of drainage, corresponding to successive pump installations at the nearby Whittlesey Mere Pumping Station, are identified, and their intimate connection with the wastage records is demonstrated. An account is also given of the various types of land-use to which the area has been put. Finally, the observed wastage rates for each stage are summarized. (3) Possible steps are outlined which could contribute towards the amelioration of the current problems arising from peat wastage in the black Fens generally.