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At least 595 records · Page 33Linked to original sources

USGS2015

An integrated approach to modeling changes in land use, land cover, and disturbance and their impact on ecosystem carbon dynamics: a case study in the Sierra Nevada Mountains of California

Increased land-use intensity (e.g. clearing of forests for cultivation, urbanization), often results in the loss of ecosystem carbon storage, while changes in productivity resulting from climate change may either help offset or exacerbate losses. However, there are large uncertainties in how land and climate systems will evolve and interact to shape future ecosystem carbon dynamics. To address this we developed the Land Use and Carbon Scenario Simulator (LUCAS) to track changes in land use, land cover, land management, and disturbance, and their impact on ecosystem carbon storage and flux within a scenario-based framework. We have combined a state-and-transition simulation model (STSM) of land change with a stock and flow model of carbon dynamics. Land-change projections downscaled from the Intergovernmental Panel on Climate Change’s (IPCC) Special Report on Emission Scenarios (SRES) were used to drive changes within the STSM, while the Integrated Biosphere Simulator (IBIS) ecosystem model was used to derive input parameters for the carbon stock and flow model. The model was applied to the Sierra Nevada Mountains ecoregion in California, USA, a region prone to large wildfires and a forestry sector projected to intensify over the next century. Three scenario simulations were conducted, including a calibration scenario, a climate-change scenario, and an integrated climate- and land-change scenario. Based on results from the calibration scenario, the LUCAS age-structured carbon accounting model was able to accurately reproduce results obtained from the process-based biogeochemical model. Under the climate-only scenario, the ecoregion was projected to be a reliable net sink of carbon, however, when land use and disturbance were introduced, the ecoregion switched to become a net source. This research demonstrates how an integrated approach to carbon accounting can be used to evaluate various drivers of ecosystem carbon change in a robust, yet transparent modeling environment.

California↗

USGS2007

Interactions across spatial scales among forest dieback, fire, and erosion in northern New Mexico landscapes

Ecosystem patterns and disturbance processes at one spatial scale often interact with processes at another scale, and the result of such cross-scale interactions can be nonlinear dynamics with thresholds. Examples of cross-scale pattern-process relationships and interactions among forest dieback, fire, and erosion are illustrated from northern New Mexico (USA) landscapes, where long-term studies have recently documented all of these disturbance processes. For example, environmental stress, operating on individual trees, can cause tree death that is amplified by insect mortality agents to propagate to patch and then landscape or even regional-scale forest dieback. Severe drought and unusual warmth in the southwestern USA since the late 1990s apparently exceeded species-specific physiological thresholds for multiple tree species, resulting in substantial vegetation mortality across millions of hectares of woodlands and forests in recent years. Predictions of forest dieback across spatial scales are constrained by uncertainties associated with: limited knowledge of species-specific physiological thresholds; individual and site-specific variation in these mortality thresholds; and positive feedback loops between rapidly-responding insect herbivore populations and their stressed plant hosts, sometimes resulting in nonlinear “pest” outbreak dynamics. Fire behavior also exhibits nonlinearities across spatial scales, illustrated by changes in historic fire regimes where patch-scale grazing disturbance led to regional-scale collapse of surface fire activity and subsequent recent increases in the scale of extreme fire events in New Mexico. Vegetation dieback interacts with fire activity by modifying fuel amounts and configurations at multiple spatial scales. Runoff and erosion processes are also subject to scale-dependent threshold behaviors, exemplified by ecohydrological work in semiarid New Mexico watersheds showing how declines in ground surface cover lead to non-linear increases in bare patch connectivity and thereby accelerated runoff and erosion at hillslope and watershed scales. Vegetation dieback, grazing, and fire can change land surface properties and cross-scale hydrologic connectivities, directly altering ecohydrological patterns of runoff and erosion. The interactions among disturbance processes across spatial scales can be key drivers in ecosystem dynamics, as illustrated by these studies of recent landscape changes in northern New Mexico. To better anticipate and mitigate accelerating human impacts to the planetary ecosystem at all spatial scales, improvements are needed in our conceptual and quantitative understanding of cross-scale interactions among disturbance processes.

New Mexico↗

USGS2025

Evaluating large wood additions as a scalable method of urban stream restoration

Urbanization is associated with increased erosion and habitat homogenization in stream ecosystems. This habitat degradation often has biological consequences, such as decreased species richness. Conventional stream restoration practices are costly, and projects are limited to small areas with easy access. A scalable, low-cost method of stream restoration is needed to address the widespread degradation occurring in urban streams. Large wood (LW) is an important element in stream ecosystems that is typically abundant in forested watersheds but scarce in urban streams. LW can reduce water velocities, generate pool habitat, decrease erosion, and provide cover for aquatic organisms. In this study, we performed experimental LW installations to assess the capacity of LW restoration to improve habitat and reduce sediment transport in an urban headwater stream in Cincinnati, Ohio. We tracked the geomorphic effects of these installations using a before-after-control-impact study design in four 60-m reaches, two treatment and two control, over a 1.5-year period to investigate the following questions: (1) Will unanchored LW additions remain stable in a flashy urban stream? (2) Will LW additions increase the availability of pool habitat? (3) Will wood additions increase bed stability and modify sediment size distributions? We found that LW installations rapidly increased pool habitat availability (size) around stable jams, but a majority of the LW jams were frequently mobilized and reconfigured by high-flow events. LW additions had no significant impact on the probability of stream bed mobilization, likely due to the instability of LW; however, the distance particles traveled once mobilized significantly decreased. While LW additions can increase the availability of pool habitat in urban headwater streams, further investigation is needed to understand the stability of such structures and the environmental context where these additions will be most beneficial.

Ohio↗

USGS1989

Vegetation alteration along trails in Shenandoah National Park, Virginia

Most studies in the USA of vegetation alteration and human impact along trails have been located in large western wilderness areas. The objective of this study was to determine vegetation changes occurring along trails in an eastern ecosystem supporting second-growth deciduous forest. The location of this study was Shenandoah National Park in Virginia, which has a long history of trail use by humans. Located in different sections of the park, ten trails were chosen as study areas. In each, transects were established to measure ground flora in trailside, transition, and undisturbed areas perpendicular to the trail. Field data were collected on frequency, life-form, and percent cover for ground flora of 25 cm or less in height. Cover and species diversity increased toward the trail in eight out often cases. Competition for light and resistance to trampling were thought to influence the occurrence of plants along the transect. Plants found along the trail border were represented by low growthforms, early blooming, or graminoid characteristics, and hemicryptophyte, therophyte, or chamaephyte life-forms. Plants found in the undisturbed zone were represented by scattered cover and frequency, woody growth forms or delicate herbaceous forms, and phanerophyte or geophyte life-forms.

Virginia↗

USGS2007

Characterization of post-fire surface cover, soils, and burn severity at the Cerro Grande Fire, New Mexico, using hyperspectral and multispectral remote sensing

Forest fires leave behind a changed ecosystem with a patchwork of surface cover that includes ash, charred organic matter, soils and soil minerals, and dead, damaged, and living vegetation. The distributions of these materials affect post-fire processes of erosion, nutrient cycling, and vegetation regrowth. We analyzed high spatial resolution (2.4??m pixel size) Airborne Visible and Infrared Imaging Spectrometer (AVIRIS) data collected over the Cerro Grande fire, to map post-fire surface cover into 10 classes, including ash, soil minerals, scorched conifer trees, and green vegetation. The Cerro Grande fire occurred near Los Alamos, New Mexico, in May 2000. The AVIRIS data were collected September 3, 2000. The surface cover map revealed complex patterns of ash, iron oxide minerals, and clay minerals in areas of complete combustion. Scorched conifer trees, which retained dry needles heated by the fire but not fully combusted by the flames, were found to cover much of the post-fire landscape. These scorched trees were found in narrow zones at the edges of completely burned areas. A surface cover map was also made using Landsat Enhanced Thematic Mapper plus (ETM+) data, collected September 5, 2000, and a maximum likelihood, supervised classification. When compared to AVIRIS, the Landsat classification grossly overestimated cover by dry conifer and ash classes and severely underestimated soil and green vegetation cover. In a comparison of AVIRIS surface cover to the Burned Area Emergency Rehabilitation (BAER) map of burn severity, the BAER high burn severity areas did not capture the variable patterns of post-fire surface cover by ash, soil, and scorched conifer trees seen in the AVIRIS map. The BAER map, derived from air photos, also did not capture the distribution of scorched trees that were observed in the AVIRIS map. Similarly, the moderate severity class of Landsat-derived burn severity maps generated from the differenced Normalized Burn Ratio (dNBR) calculation had low agreement with the AVIRIS classes of scorched conifer trees. Burn severity and surface cover images were found to contain complementary information, with the dNBR map presenting an image of degree of change caused by fire and the AVIRIS-derived map showing specific surface cover resulting from fire.

Remote Sensing of Environment↗

USGS2017

Extent of localized tree mortality influences soil biogeochemical response in a beetle-infested coniferous forest

Recent increases in the magnitude and occurrence of insect-induced tree mortality are disruptingevergreen forests globally. To resolve potentially conflicting ecosystem responses, we investigatedwhether surrounding trees exert compensatory effects on biogeochemical signatures following beetleinfestation. To this end, plots were surveyed within a Colorado Rocky Mountain watershed that expe-rienced beetle infestation almost a decade prior and contained a range of surrounding tree mortality(from 9 to 91% of standing trees). Near-surface soil horizons under plot-centered live (green) and beetle-killed (grey) lodgepole pines were sampled over two consecutive summers with variable moistureconditions. Results revealed that soil respiration was 18e28% lower beneath beetle-infested trees andcorrelated to elevated dissolved organic carbon aromaticity. While certain edaphic parameters includingpH and water content were elevated below grey compared to green trees regardless of the mortalityextent within plots, other biogeochemical responses required a higher severity of surrounding mortalityto overcome compensatory effects of neighboring live trees. For instance, C:N ratios under grey treesdeclined with increased severity of surrounding tree mortality, and the proportion of ammonium dis-played a threshold effect with pronounced increases after surrounding tree mortality exceeded ~40%.Overall, the biogeochemical response to tree death was most prominent in the mineral soil horizonwhere tree mortality had the largest affect on carbon recalcitrance and the enrichment of nitrogenspecies. These results can aid in determining when and where nutrient cycles and biogeochemicalfeedbacks to the atmosphere and hydrosphere will be observed in association with this type of ecological disturbance.

Rocky Mountain Watershed↗

USGS2017

Epicormic resprouting in fire-prone ecosystems

Many plants resprout from basal buds after disturbance, and this is common in shrublands subjected to high-intensity fires. However, resprouting after fire from epicormic (stem) buds is globally far less common. Unlike basal resprouting, post-fire epicormic resprouting is a key plant adaptation for retention of the arborescent skeleton after fire, allowing rapid recovery of the forest or woodland and leading to greater ecosystem resilience under recurrent high-intensity fires. Here we review the biogeography of epicormic resprouting, the mechanisms of protection, the fire regimes where it occurs, and the evolutionary drivers that shaped this trait. We propose that epicormic resprouting is adaptive in ecosystems with high fire frequency and relatively high productivity, at moderate–high fire intensities.

Trends in Plant Science↗

USGS2002

Scale perspectives on avian diversity in western riparian ecosystems

Conservation of riparian vegetation in western North America has, in part, emphasized providing habitats for a locally diverse avifauna. Site diversity, especially relative to the number of species present, is generally high within riparian avifaunas. Between-habitat diversity changes across a watershed, with riparian species assemblages differing most from upland assemblages at the highest and lowest elevations. This pattern can be attributed to enhanced avian movements within the riparian vegetation. The corridors for bird movements, in turn, facilitate faunal mixing on a broader scale, influencing regional diversity within landscapes. Riparian ecosystems are viewed as connectors of forests across fragmented landscapes. In western settings, however, they are highly linearized forests transecting watersheds between upland associations of high elevations and very different associations at lower elevations. Regionally, riparian vegetation represents linear islands that are internally both floristically and faunistically dynamic rather than mere bridges of homogeneous vegetation in landscape networks. The significance of riparian vegetation as habitat for western birds has been defined primarily at the local level. Conservation activities favoring site diversity are short-sighted, however, and could have severe consequences for unique elements of riparian avifaunas. Conservation actions must evaluate how local activities alter potential dispersal opportunities for ecological-generalist versus riparian-obligate species. Maintaining the character and integrity of riparian avifaunas requires planning from regional and continental perspectives.

Conservation Biology↗

USGS2022

Mercury in soils of the conterminous United States: Patterns and pools

Soils account for the largest global mercury reservoirs, but observations are sparse in many regions. The accumulation and turnover of mercury in soils determines whether they act as an atmospheric source or sink. Here, we present a spatial analysis of soil mercury from a large soil survey (three horizons, ∼4800 sites) across the conterminous United States conducted by the U.S. Geological Survey. Soil mercury pools were calculated for 11 layers, cumulatively representing the top 1 m of soil, and totaling 158 ± 2 Gg (±SD) of mercury (20.3 ± 0.2 mg m −2 ). Mercury areal density was greatest in mixed forest (27.3 ± 0.5 mg m −2 ), cropland (25.3 ± 0.3 mg m −2 ), and deciduous forest (25.6 ± 0.5 mg m −2 ) ecosystems and lowest in barren (13.5 ± 0.3 mg m −2 ) and shrubland (12.6 ± 0.2 mg m −2 ) ecosystems. Assessment of the provenance of soil mercury using bedrock titanium normalization suggests that 62%–95% of soil mercury is unexplained by parental sources.

conterminous United States↗

USGS2017

California Spotted Owl (Strix occidentalis occidentalis) habitat use patterns in a burned landscape

Fire is a dynamic ecosystem process of mixed-conifer forests of the Sierra Nevada, but there is limited scientific information addressing wildlife habitat use in burned landscapes. Recent studies have presented contradictory information regarding the effects of stand-replacing wildfires on Spotted Owls ( Strix occidentalis ) and their habitat. While fire promotes heterogeneous forest landscapes shown to be favored by owls, high severity fire may create large canopy gaps that can fragment the closed-canopy habitat preferred by Spotted Owls. We used radio-telemetry to determine whether foraging California Spotted Owls ( S. o. occidentalis ) in Yosemite National Park, California, USA, showed selection for particular fire severity patch types within their home ranges. Our results suggested that Spotted Owls exhibited strong habitat selection within their home ranges for locations near the roost and edge habitats, and weak selection for lower fire severity patch types. Although owls selected high contrast edges with greater relative probabilities than low contrast edges, we did not detect a statistical difference between these probabilities. Protecting forests from stand-replacing fires via mechanical thinning or prescribed fire is a priority for management agencies, and our results suggest that fires of low to moderate severity can create habitat conditions within California Spotted Owls' home ranges that are favored for foraging.

The Condor↗

USGS2018

A dirty dozen ways to die: Metrics and modifiers of mortality driven by drought and warming for a tree species

Tree mortality events driven by drought and warmer temperature, often amplified by pests and pathogens, are emerging as one of the predominant climate change impacts on plants. Understanding and predicting widespread tree mortality events in the future is vital as they affect ecosystem goods and services provided by forests and woodlands, including carbon storage needed to help offset warming. Additionally, if extensive enough, tree die-off events can influence not only local climate but also climate and vegetation elsewhere via ecoclimate teleconnections. Consequently, recent efforts have focused on improving predictions of tree mortality. One of the most commercially important genera of trees is Pinus , and the most studied species globally for drought-induced tree mortality is piñon pine, Pinus edulis . Numerous metrics have been developed in association with predicting mortality thresholds or variations in mortality for this species. In this article, we compiled metrics associated with drought and warming related mortality that were developed for P. edulis or for which P. edulis was a key example species used in a calculation or prediction. We grouped these metrics into three categories: (i) those related to simple climate variables, (ii) those related to physiological responses, and (iii) those that require multi-step calculations or modeling using climate, ecohydrological, and/or ecophysiological data; and we identified the spatial-temporal scale of each of these metrics. We also compiled factors shown to modify rates or sensitivities of mortality. The metrics to predict mortality include empirical ones which often have implicit linkages to expected mechanisms, and more mechanistic ones related to physiological drivers. The metrics for P. edulis have similarities with those available for other species of Pinus . Expected future mortality events will provide an opportunity to observationally and experimentally test and compare these metrics related to tree mortality for P. edulis via near-term ecological forecasting. The metrics for P. edulis may also be useful as potential analogs for other genera. Improving predictions of tree mortality for this species and others will be increasingly important as an aid to move toward anticipatory management.

Frontiers in Forests and Global Change↗

USGS2016

Landscape effects of wildfire on permafrost distribution in interior Alaska derived from remote sensing

Climate change coupled with an intensifying wildfire regime is becoming an important driver of permafrost loss and ecosystem change in the northern boreal forest. There is a growing need to understand the effects of fire on the spatial distribution of permafrost and its associated ecological consequences. We focus on the effects of fire a decade after disturbance in a rocky upland landscape in the interior Alaskan boreal forest. Our main objectives were to (1) map near-surface permafrost distribution and drainage classes and (2) analyze the controls over landscape-scale patterns of post-fire permafrost degradation. Relationships among remote sensing variables and field-based data on soil properties (temperature, moisture, organic layer thickness) and vegetation (plant community composition) were analyzed using correlation, regression, and ordination analyses. The remote sensing data we considered included spectral indices from optical datasets (Landsat 7 Enhanced Thematic Mapper Plus (ETM+) and Landsat 8 Operational Land Imager (OLI)), the principal components of a time series of radar backscatter (Advanced Land Observing Satellite—Phased Array type L-band Synthetic Aperture Radar (ALOS-PALSAR)), and topographic variables from a Light Detection and Ranging (LiDAR)-derived digital elevation model (DEM). We found strong empirical relationships between the normalized difference infrared index (NDII) and post-fire vegetation, soil moisture, and soil temperature, enabling us to indirectly map permafrost status and drainage class using regression-based models. The thickness of the insulating surface organic layer after fire, a measure of burn severity, was an important control over the extent of permafrost degradation. According to our classifications, 90% of the area considered to have experienced high severity burn (using the difference normalized burn ratio (dNBR)) lacked permafrost after fire. Permafrost thaw, in turn, likely increased drainage and resulted in drier surface soils. Burn severity also influenced plant community composition, which was tightly linked to soil temperature and moisture. Overall, interactions between burn severity, topography, and vegetation appear to control the distribution of near-surface permafrost and associated drainage conditions after disturbance.

Alaska↗

USGS2002

Produced water and hydrocarbon releases at the Osage-Skiatook petroleum environmental research sites, Osage County, Oklahoma: Introduction and geologic setting

In February 2001, the USGS started studies of the impacts of produced water and hydrocarbon releases at 2 research sites adjacent to Skiatook Lake in southeastern Osage County near Tulsa, Oklahoma. Both sites are in a dissected area of modest relief underlain by interbedded shale, siltstone, and sandstone. Thicker resistant sandstone units typically form the hill crests. Hillslopes are underlain by shale, siltstone, and thin sandstone beds. Core drilling during February and March of 2002 indicates that the depth of weathering of the bedrock is about 10-25 m on the ridges and 5-6 m in small stream valleys. These sites are located in the Cross Timbers ecosystem area of northeastern Oklahoma. Oak forests cover the hillslopes. Grassslands occur on most ridge crests. Site "A" is an area where produced water and hydrocarbon releases occurred primarily 60-85 years ago. The site is located in section 13, T22N, R10E. The entire site is underlain by 1) a surface layer of eolian sand of varying thickness (maximum observed about 80 cm); 2) colluvium that ranges from large boulders of sandstone to thin, granule-pebble conglomerate; 3) weathered shale, siltstone, and sandstone; and 4) underlying unweathered bedrock. Much of the site appears to have been impacted by early salt-water releases that killed the oak forest, however a few oak trees persist as single trees or clumps of trees within the original kill area. The gently sloping upper part of the site is slightly eroded in places and has been mostly revegetated with grasses, forbs, sumac, and a few trees. The lower, steeper, more heavily salt-impacted portion has been eroded to depths of as much as 2 m. This area drains into the Cedar Creek arm of Skiatook Lake. Oil from two redwood tanks at the top of the site was transported via ditch to two roadside pits at mid-site. Oil spills from pipeline breaks and tank batteries (no longer present) are scattered around the site. Most of the oil is highly weathered however, one pit contains what appears to be relatively fresh asphaltic tank bottom material. Site "B" is located in sections 29 and 32, T22N, R10E. It includes an active production tank battery and adjacent large pit, two injection well sites, one with an adjacent small pit, and an old tank battery. All of these sites are within 45 m of the shoreline of the lake (at normal pool elevation). The pit associated with the active tank battery is within 15 m of the lake. Two small creeks cross the northern and southern parts of the site. The upper part of the site is characterized by a thin surface layer of eolian sand mixed with sandstone-clast colluvium underlain by weathered and unweathered shale whereas the lower part of the site is underlain by 1) a surface layer of eolian sand (20-70 cm thick); 2) colluvial apron and alluvial deposits of varying thickness comprised of sandstone pebbles, cobbles, and boulders with a fine sand matrix; 3) weathered shale; and 4) unweathered bedrock. Three salt scars extend downslope from the active tank battery, the injection well/pit, and the old tank battery to the lake edge. The area underlain by shallow saline ground water is substantially larger than the salt-scarred areas. Dissolved hydrocarbons can be detected in the shallow ground water below the active pit.

Oklahoma↗

USGS2020

Local to landscape-level controls of water fluxes through Hawaiian forests: Effects of invasive animals and plants on soil infiltration capacity across substrate and moisture gradients

Given the potential effect of invasive plants and animals to water fluxes through forests, the invasive-driven degradation of native ecosystems is a topic of great concern for many downstream land and water managers. The infiltration rate determines the partitioning between runoff and infiltration into soil in Hawaiian forests and beyond. Thus, to explore the ecohydrological effects of plant and animal invasion in mesic and wet forests in Hawaii, we measured soil infiltration capacity in multiple fenced (i.e., ungulate-free)/unfenced and native/invaded forest sites along moisture and substrate age gradients across the islands of Hawai‘i and Kaua‘i. We also characterized forest composition and structure and soil characteristics at these sites to assess the direct and vegetation-mediated impacts of invasive species on infiltration capacity. Infiltration capacity is highly variable across forested sites and the wider landscape. Much of this variability is determined by a complex set of soil, vegetation, and disturbance factors that affect infiltration capacity at the immediate surrounding of measurement plots. Consequently, the effect of any given factor can be masked by variability in other factors. However, by controlling for variability in soil and vegetation conditions at a local plot level, we found that the presence of invasive species in forests has complex and sometimes non-intuitive effects on infiltration. Our final models showed that invasive ungulates negatively affect soil infiltration capacity consistently across the wide moisture and substrate age gradients considered. Additionally, because several soil characteristics known to be affected by ungulates were associated with local infiltration rates (e.g., soil organic matter, bare soil cover, soil depth), the long-term secondary effects of high ungulate densities in Hawaiian forests may be higher than effects observed in this study. These results provide clear evidence for land managers that ungulate control efforts likely improve ecohydrologic function to mesic and wet forest systems critical to protecting downstream and nearshore resources and maintaining groundwater recharge. Compared to ungulate effects, the effect of invasive plants on water infiltration capacity in Hawaiian forests appeared much more complex. In general, elements of forest structure including increased canopy, understory and floor cover, greater presence of large roots, and lower grass and bare soil covers were positively associated with water infiltration. Whether native or not, a plant species’ potential to alter infiltration rates in Hawaiian forests was likely to depend on its physiognomy and how it affects forest community structure. For instance, while the cover of native dominant tree ‘ōhi‘a, Metrosideros polymorpha, was found to be positively associated with infiltration capacity (perhaps as an indicator of overall forest integrity), invasive Himalayan ginger, Hedychium gardnerianum, was also positively correlated with infiltration capacity, possibly due to preferential flow channels created by the presence of large root mats. Few studies have conducted comprehensive integrated ecological and hydrological sampling in forests of high conservation value. While we show there are large benefits to understanding how conservation efforts may help shape water fluxes, we also found that the commonly used study design for infiltration studies used here and elsewhere (i.e., adjacent paired sites) could be modified to provide more accurate effects of invasion in future studies for ecosystems in Hawaii and beyond.

Hawaii↗

USGS2015

The vulnerability of Indo-Pacific mangrove forests to sea-level rise

Sea-level rise can threaten the long-term sustainability of coastal communities and valuable ecosystems such as coral reefs, salt marshes and mangroves. Mangrove forests have the capacity to keep pace with sea-level rise and to avoid inundation through vertical accretion of sediments, which allows them to maintain wetland soil elevations suitable for plant growth. The Indo-Pacific region holds most of the world’s mangrove forests, but sediment delivery in this region is declining, owing to anthropogenic activities such as damming of rivers. This decline is of particular concern because the Indo-Pacific region is expected to have variable, but high, rates of future sea-level rise. Here we analyse recent trends in mangrove surface elevation changes across the Indo-Pacific region using data from a network of surface elevation table instruments. We find that sediment availability can enable mangrove forests to maintain rates of soil-surface elevation gain that match or exceed that of sea-level rise, but for 69 per cent of our study sites the current rate of sea-level rise exceeded the soil surface elevation gain. We also present a model based on our field data, which suggests that mangrove forests at sites with low tidal range and low sediment supply could be submerged as early as 2070.

Indo-Pacific region↗

USGS2017

Hawai`i forest bird monitoring database: Database dictionary

Between 1976 and 1981, the U.S. Fish and Wildlife Service (now U.S. Geological Survey – Pacific Island Ecosystems Research Center [USGS-PIERC]) conducted systematic surveys of forest birds and plant communities on all the main Hawaiian Islands, except O‘ahu, as part of the Hawai‘i Forest Bird Surveys (HFBS). Results of this monumental effort have guided conservation efforts and provided the basis for many plant and bird recovery plans and land acquisition decisions in Hawai‘i. Unfortunately, these estimates and range maps are now seriously outdated, hindering modern conservation decision-making and recovery planning. HFBIDP staff work closely with land managers and others to identify the location of bird populations in need of protection. In addition, HFBIDP is able to assess field collection methods, census areas, and survey frequency for their effectiveness. Survey and geographical data are refined and released in successive versions, each more inclusive, detailed, and accurate than the previous release. Incrementally releasing data gives land managers and survey coordinators reasonably good data to work with early on rather than waiting for the release of ‘perfect’ data, ‘perfectly’ analyzed. Consequently, summary results are available in a timely manner.

Technical Report↗

USGS2020

Changes in ecosystem nitrogen and carbon allocation with black mangrove (Avicennia germinans) encroachment into Spartina alterniflora salt marsh

Increases in temperature are expected to facilitate encroachment of tropical mangrove forests into temperate salt marshes, yet the effects on ecosystem services are understudied. Our work was conducted along a mangrove expansion front in Louisiana (USA), an area where coastal wetlands are in rapid decline due to compounding factors, including reduced sediment supply, rising sea level, and subsidence. Marsh and mangrove ecosystems are each known for their ability to adjust to sea-level rise and support numerous ecosystem services, but there are some differences in the societal benefits they provide. Here, we compare carbon and nitrogen stocks and relate these findings to the expected effects of mangrove encroachment on nitrogen filtration and carbon sequestration in coastal wetlands. We specifically evaluate the implications of black mangrove ( Avicennia germinans ) encroachment into Spartina alterniflora -dominated salt marsh. Our results indicate that black mangrove encroachment will lead to increased aboveground carbon and nitrogen stocks. However, we found no differences in belowground (that is, root and sediment) nitrogen or carbon stocks between marshes and mangroves. Thus, the shift from marsh to mangrove may provide decadal-scale increases in aboveground nitrogen and carbon sequestration, but belowground nitrogen and carbon sequestration (that is, carbon burial) may not be affected. We measured lower pore water nitrogen content beneath growing mangroves, which we postulate may be due to greater nitrogen uptake and storage in mangrove aboveground compartments compared to marshes. However, further studies are needed to better characterize the implications of mangrove encroachment on nitrogen cycling, storage, and export to the coastal ocean.

Louisiana↗

USGS2012

Sinks for nitrogen inputs in terrestrial ecosystems: a meta-analysis of 15 N tracer field studies

Effects of anthropogenic nitrogen (N) deposition and the ability of terrestrial ecosystems to store carbon (C) depend in part on the amount of N retained in the system and its partitioning among plant and soil pools. We conducted a meta-analysis of studies at 48 sites across four continents that used enriched 15 N isotope tracers in order to synthesize information about total ecosystem N retention (i.e., total ecosystem 15 N recovery in plant and soil pools) across natural systems and N partitioning among ecosystem pools. The greatest recoveries of ecosystem 15 N tracer occurred in shrublands (mean, 89.5%) and wetlands (84.8%) followed by forests (74.9%) and grasslands (51.8%). In the short term (<1 week after 15 N tracer application), total ecosystem 15 N recovery was negatively correlated with fine-root and soil 15 N natural abundance, and organic soil C and N concentration but was positively correlated with mean annual temperature and mineral soil C:N. In the longer term (3–18 months after 15 N tracer application), total ecosystem 15 N retention was negatively correlated with foliar natural-abundance 15 N but was positively correlated with mineral soil C and N concentration and C: N, showing that plant and soil natural-abundance 15 N and soil C:N are good indicators of total ecosystem N retention. Foliar N concentration was not significantly related to ecosystem 15 N tracer recovery, suggesting that plant N status is not a good predictor of total ecosystem N retention. Because the largest ecosystem sinks for 15 N tracer were below ground in forests, shrublands, and grasslands, we conclude that growth enhancement and potential for increased C storage in aboveground biomass from atmospheric N deposition is likely to be modest in these ecosystems. Total ecosystem 15 N recovery decreased with N fertilization, with an apparent threshold fertilization rate of 46 kg N·ha -1 ·yr -1 above which most ecosystems showed net losses of applied 15 N tracer in response to N fertilizer addition.

Ecology↗