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At least 703 records · Page 39Linked to original sources
USGS2020

Biogeography of fire regimes in western US conifer forests: A trait-based approach

Aim Functional traits are a critical link between species distributions and the ecosystem processes that structure those species’ niches. Concurrent increases in the availability of functional trait data and our ability to model species distributions present an opportunity to develop functional trait biogeography, i.e. the mapping of functional traits across space. Functional trait biogeography can improve process-based predictions about the resistance of certain species assemblages to changing environmental conditions across landscape scales. We illustrate this concept by developing the first trait-based, quantitative ranking of fire resistance (adult tree survival) in North American conifer species, and mapping that fire resistance across space. Location and Time period Western Continental United States, present-day. Major taxa studied 29 common conifer tree species. Methods We compiled six traits for each species: three relating to tree morphology and three relating to litter flammability. We combined these traits into a single fire resistance score, and used community-weighted averaging to estimate the fire resistance scores of different forest communities, using interpolated species distribution and relative abundance data. Results Species associated with historically frequent fire have high fire resistance scores (e.g., Pinus ponderosa), reflected by thick bark, tall crowns, and flammable litter. Species associated with subalpine or arid conditions have low fire resistance scores (e.g., Picea engelmannii and Pinus edulis), reflected by thin bark, short stature, poor self-pruning and low litter flammability. A map of forest community fire resistance across the western US reveals agreement with independent assessments of historical fire regimes, while also identifying areas where community-wide species traits may be mismatched with historical fire regimes. Main conclusions Quantifying the functional traits that confer resistance to tree-killing fire provides a direct link between ecosystem disturbance and community resistance. Understanding this link is critical to evaluating long-term resilience of different forest types under dynamic fire regimes. Our work represents the first known spatial representation of fire-resistance traits at a regional scale, and as such provides a link between functional traits and biogeography relevant to a critical ecosystem process.

Global Ecology and Biogeography↗
USGS1999

Seasonal relationships between precipitation, forest floor, and streamwater nitrogen, Isle Royale, Michigan

The Upper Great Lakes receive large amounts of precipitation-NH + 4 and moderate NO - 3 inputs. Increased atmospheric inorganic N input has led to concern about ecosystem capacity to utilize excess N. This paper summarizes a 5-yr study of seasonal N content and flux in precipitation, snowpack, forest floor, and streamwater in order to assess the source of inorganic N outputs in streamflow from a small boreal watershed. Average precipitation N input was 3 kg ha -1 yr -1 . The peak snowpack N content averaged 0.55 kg ha -1 . The forest floor inorganic N pool was ≈ 2 kg ha -1 , eight times larger than monthly precipitation N input. The inorganic N pool size peaked in spring and early summer. Ninety percent of the forest floor inorganic N pool was made up of NH + 4 -N. Forest floor inorganic N pools generally increased with temperature. Net N mineralization was 15 kg ha -1 yr -1 , and monthly rates peaked in early summer. During winter, the mean monthly net N mineralization rate was twice the peak snowpack N content. Streamwater NO - 3 concentration peaked in winter, and inorganic N output peaked in late fall. Beneath the dominant boreal forest species, net N mineralization rates were positively correlated ( P < 0.05) with streamwater NO - 3 concentrations. Forest floor NO - 3 pools beneath alder [ Alnus rugosa (Du Roi) Spreng] were positively correlated ( P < 0.01) to streamwater NO - 3 output. At the watershed mouth, streamwater NO - 3 concentrations were positively correlated ( P < 0.05) with precipitation NO - 3 input and precipitation amount. The relatively small snowpack N content and seasonal precipitation N input compared to forest floor inorganic N pools and net N mineralization rates, the strong ecosystem retention of precipitation N inputs, and the seasonal streamwater NO - 3 concentration and output pattern all indicated that little streamwater NO - 3 came directly from precipitation or snowmelt.

Michigan↗
USGS2019

Seasonality and prevalence of pollen collected from Hawaiian nectarivorous birds

Hawaiian nectarivorous forest birds play a vital ecological role as pollinators in Hawaiian ecosystems. However, little is known about what nectar resources are utilized by Hawai‘i’s nectarivorous birds, how seasonality influences nectar availability, and how nectar preference differs by bird species. We sampled pollen from the heads of ‘i‘iwi (Drepanis coccinea), ‘apapane (Himatione sanguinea), Hawai‘i ‘amakihi (Chlorodrepanis virens), and the non-native Japanese white-eye (Zosterops japonicas) captured at Hakalau Forest National Wildlife Refuge on Hawai‘i Island. ‘Ōhi‘a (Metrosideros polymorpha) was the most prevalent pollen species, observed throughout the sampling period while other pollen species were more seasonal in occurrence. Consistent with the peak flowering phenology of the plant species, pollen from koa (Acacia koa), māmane (Sophora chrysophylla), and gorse (Ulex europaeus) plant species were more commonly sampled from birds in the winter months, while ‘ōhelo (Vaccinium reticulatum), ‘ākala (Rubus hawaiensis), and blackberry (Rubus argutus) were more prevalent during the spring months. We also found an association between bird species and pollen resources, with ‘i‘iwi and Hawai‘i ‘amakihi having a higher diversity of pollen than ‘apapane and Japanese white-eye, which primarily had just ‘ōhi‘a. These results demonstrate that ‘ōhi‘a is likely the most important nectar resource for Hawai‘i’s nectar feeding birds, but seasonally abundant nectar may be important for some species.

Hawaii↗
USGS2018

Herbicides and herbivory interact to drive plant community and crop‐tree establishment

Land management practices often directly alter vegetation structure and composition, but the degree to which ecological processes such as herbivory interact with management to influence biodiversity is less well understood. We hypothesized that large herbivores compound the effects of intensive forest management on early seral plant communities and plantation establishment (i.e., tree survival and growth), and the degree of such effects is dependent on the intensity of management practices. We established 225 m 2 wild‐ungulate (deer and elk) exclosures, nested within a manipulated gradient of management intensity (no‐herbicide Control, Light herbicide, Moderate herbicide and Intensive herbicide treatments), replicated at the scale of whole harvest units (10‐19 ha). Vegetation structure, composition and crop‐tree responses to herbivory varied across the gradient of herbicide application during the first two years of stand establishment, with herbivory effects most evident at intermediate herbicide treatments. In the Moderate herbicide treatment – which approximates treatments applied to > 2.5 million hectares in Pacific Northwest U.S.A. – foraging by deer and elk resulted in simplified, low‐cover plant communities more closely resembling the Intensive herbicide treatment. Herbivory further suppressed the growth of competing vegetation in the Light herbicide treatment, improving crop‐tree survival, and providing early evidence of an ecosystem service. By changing community composition and vegetation structure, intensive forest management alters foraging selectivity and subsequent plant‐herbivore interactions; initial shifts in early seral communities are likely to influence understory plant communities and tree growth in later stages of forest development.

Oregon↗
USGS2021

Regeneration trends along climate gradients in Taxodium distichum forests of the southeastern United States

The development of relict vegetation at the edges of some ecosystems has taken place particularly in environments where the regeneration of foundational species is declining. As an important stage of regeneration in the Taxodium distichum , this study explored the relationship of cone volume and seed number across environmental gradients in the Mississippi River Alluvial Valley (MRAV) and northern Gulf of Mexico Coast (GOM) in a long-term network of forested wetlands (North American Baldcypress Swamp Network (NABCSN)) from 2007 to 2019. Resembling spheroids, the volumes of Taxodium distichum cones were based on the measured dimensions of the cones collected in swamps across southeastern environmental gradients. Cones with larger volumes also had larger numbers of seeds (r 2 = 0.423, F = 113.9, p < 0.0001; Linear regression equation: Seed number per cone = 9.8925223 + 0.8854056* Cone volume cm 3 ). Mean cone volumes were related to water availability with highest volumes in locations with moderate amounts of total annual precipitation (e.g., White River National Wildlife Refuge (NWR) Arkansas, Tensas NWR Louisiana, and Morgan Brake NWR Mississippi), and longer periods of annual percent time of site drawdown. Cone volume was high in 2018 following the 2017 mega-flood in the Mississippi River Alluvial Valley (MRAV) generated by Hurricane Harvey. Mean annual air temperature was not related to cone volume. Along the Gulf Coast, mean cone volume increased from east to west from Florida to Texas. Especially near the edge of the range of T. distichum forests, smaller cones may be related to regeneration failure and lower seed numbers to support regeneration. A better understanding of regeneration constraints can inform managers of the emergence of relict status in these forests.

Arkansas, Florida, Illinois, Kentucky, Louisiana, ↗
USGS2015

Critical loads of atmospheric deposition to Adirondack lake watersheds: A guide for policymakers

Acid deposition is sometimes referred to as “acid rain,” although part of the acid load reaches the surface by means other than rainfall. In the eastern U.S., acid deposition consists of several forms of sulfur and nitrogen that largely originate as emissions to the atmosphere from sources such as electricity-generating facilities (coal, oil, and natural gas), diesel- and gasoline-burning vehicles, some agricultural activities, and smokestack industries. Acid deposition is known to cause deleterious effects to sensitive ecosystems of which the Adirondack region of New York State provides several well-known and well-studied examples. This largely forested region includes abundant lakes, streams, and wetlands and possesses several landscape features that result in high ecosystem sensitivity to acid deposition. These features include bedrock that weathers slowly, steep slopes, and thin, naturally acidic soils. An ecosystem is described as sensitive to, or affected by, acid deposition if prolonged exposure to acid deposition has resulted in detrimental ecosystem effects. Soils, streams, and lakes that are less sensitive are better able to buffer acid deposition. A principal reason that acidification is a concern for resource managers is because of the changes induced in native biota and their habitat on land and in water. As the chemistry of soils and surface waters in sensitive landscapes changes in response to prolonged exposure to acid deposition, organisms that cannot tolerate high acidity, such as sugar maple trees and many species of fish and aquatic insects, may be gradually eliminated from the ecosystem. Other biota such as red spruce may experience increased stress and reduced growth rates as a result of acidification, exposing these species to increased susceptibility to disease and other natural stressors and perhaps increased mortality. The ecological effects of acid deposition have been documented by extensive research that began in the U.S. in the 1970s and continues today. This report does not provide a detailed discussion of these ecological effects, but interested readers can refer to four publications that provide good summaries of current scientific knowledge of these effects, including extensive reference to previous research in the Adirondacks (Driscoll et al. 2001, Jenkins et al. 2007, Burns et al. 2011, Sullivan 2015).

New York↗
USGS2017

The Upper Mississippi River System—Topobathy

The Upper Mississippi River System (UMRS), the navigable part of the Upper Mississippi and Illinois Rivers, is a diverse ecosystem that contains river channels, tributaries, shallow-water wetlands, backwater lakes, and flood-plain forests. Approximately 10,000 years of geologic and hydrographic history exist within the UMRS. Because it maintains crucial wildlife and fish habitats, the dynamic ecosystems of the Upper Mississippi River Basin and its tributaries are contingent on the adjacent flood plains and water-level fluctuations of the Mississippi River. Separate data for flood-plain elevation (lidar) and riverbed elevation (bathymetry) were collected on the UMRS by the U.S. Army Corps of Engineers’ (USACE) Upper Mississippi River Restoration (UMRR) Program. Using the two elevation datasets, the U.S. Geological Survey (USGS) Upper Midwest Environmental Sciences Center (UMESC) developed a systemic topobathy dataset.

Illinois, Iowa, Minnesota, Missouri, Wisconsin↗
USGS2019

Effect of permafrost thaw on plant and soil fungal community in the boreal forest: Does fungal community change mediate plant productivity response?

Permafrost thaw is leading to rapid shifts in boreal ecosystem function. Permafrost thaw affects soil carbon turnover through changes in soil hydrology, however, the biotic mechanisms regulating plant community response remain elusive. Here, we measured the response of fungal community composition and soil nutrient content in an intact permafrost plateau forest soil and an adjacent thermokarst bog using barcoded amplicon targeting ITS2 and 28S rRNA genes. Next, we used the soils from the permafrost plateau and the thermokarst bog as soil inoculum in a greenhouse experiment to measure whether shifts in fungal community and soil water level regulate plant productivity. Overall, we found that fungal community composition differed significantly between the thawed and intact permafrost sites, but soil nutrient content did not. Relative abundance of mycorrhizal fungal taxa decreased while relative abundance of putative fungal pathogens increased with permafrost thaw. In the greenhouse, we found that ecto- and arbuscular associated host plants had higher productivity in permafrost-intact soils relative to thawed soils. However, productivity of non-mycorrhizal tussock grass was more affected by soil water levels than soil communities. Our results suggest that fungal communities are crucial in mediating plant response to permafrost thaws inducing hydrology changes.

Alaska↗
USGS2020

Simulation modeling of complex climate, wildfire, and vegetation dynamics to address wicked problems in land management

Complex, reciprocal interactions among climate, disturbance, and vegetation dramatically alter spatial landscape patterns and influence ecosystem dynamics. As climate and disturbance regimes shift, historical analogs and past empirical studies may not be entirely appropriate as templates for future management. The need for a better understanding of the potential impacts of climate changes on ecosystems is reaching a new level of urgency, especially in highly perturbed or vulnerable ecological systems. Simulation models are extremely useful tools for guiding management decisions in an era of rapid change, thus providing potential solutions for wicked problems in land management—those that are difficult to solve and inherently resistant to easily definable solutions. We identify three experimental approaches for landscape modeling that address management challenges in the context of uncertain climate futures and complex ecological interactions: (1) an historical comparative approach, (2) a future comparative approach, and (3) threshold detection. We provide examples of each approach from previously published studies of simulated climate, disturbance, and landscape dynamics in forested landscapes of the western United States, modeled with the FireBGCv2 ecosystem process model. Cumulatively, model outcomes indicate that typical land management strategies will likely not be sufficient to counteract the impacts of rapid climate change and altered disturbance regimes that threaten the stability of ecosystems. Without implementation of new, adaptive management strategies, future landscapes are very likely to be different than historical or contemporary ones, with significant and sometimes persistent changes triggered by interactions of climate and wildfire.

Montana, New Mexico, Wyoming↗
USGS2012

Effects of native forest restoration on soil hydraulic properties, Auwahi, Maui, Hawaiian Islands

Over historic time Hawai'i's dryland forests have been largely replaced by grasslands for grazing livestock. On-going efforts have been undertaken to restore dryland forests to bring back native species and reduce erosion. The reestablishment of native ecosystems on land severely degraded by long-term alternative use requires reversal of the impacts of erosion, organic-matter loss, and soil structural damage on soil hydraulic properties. This issue is perhaps especially critical in dryland forests where the soil must facilitate native plants' optimal use of limited water. These reforestation efforts depend on restoring soil ecological function, including soil hydraulic properties. We hypothesized that reforestation can measurably change soil hydraulic properties over restoration timescales. At a site on the island of Maui (Hawai'i, USA), we measured infiltration capacity, hydrophobicity, and abundance of preferential flow channels in a deforested grassland and in an adjacent area where active reforestation has been going on for fourteen years. Compared to the nearby deforested rangeland, mean field-saturated hydraulic conductivity in the newly restored forest measured by 55 infiltrometer tests was greater by a factor of 2.0. Hydrophobicity on an 8-point scale increased from average category 6.0 to 6.9. A 4-point empirical categorization of preferentiality in subsurface wetting patterns increased from an average 1.3 in grasslands to 2.6 in the restored forest. All of these changes act to distribute infiltrated water faster and deeper, as appropriate for native plant needs. This study indicates that vegetation restoration can lead to ecohydrologically important changes in soil hydraulic properties over decadal time scales.

Hawai'i↗
USGS2014

Changes in the structure and function of northern Alaskan ecosystems when considering variable leaf-out times across groupings of species in a dynamic vegetation model

The phenology of arctic ecosystems is driven primarily by abiotic forces, with temperature acting as the main determinant of growing season onset and leaf budburst in the spring. However, while the plant species in arctic ecosystems require differing amounts of accumulated heat for leaf-out, dynamic vegetation models simulated over regional to global scales typically assume some average leaf-out for all of the species within an ecosystem. Here, we make use of air temperature records and observations of spring leaf phenology collected across dominant groupings of species (dwarf birch shrubs, willow shrubs, other deciduous shrubs, grasses, sedges, and forbs) in arctic and boreal ecosystems in Alaska. We then parameterize a dynamic vegetation model based on these data for four types of tundra ecosystems (heath tundra, shrub tundra, wet sedge tundra, and tussock tundra), as well as ecotonal boreal white spruce forest, and perform model simulations for the years 1970 -2100. Over the course of the model simulations, we found changes in ecosystem composition under this new phenology algorithm compared to simulations with the previous phenology algorithm. These changes were the result of the differential timing of leaf-out, as well as the ability for the groupings of species to compete for nitrogen and light availability. Regionally, there were differences in the trends of the carbon pools and fluxes between the new phenology algorithm and the previous phenology algorithm, although these differences depended on the future climate scenario. These findings indicate the importance of leaf phenology data collection by species and across the various ecosystem types within the highly heterogeneous Arctic landscape, and that dynamic vegetation models should consider variation in leaf-out by groupings of species within these ecosystems to make more accurate projections of future plant distributions and carbon cycling in Arctic regions.

Global Change Biology↗
USGS2020

Frequent burning causes large losses of carbon from deep soil layers in a temperate savanna

Fire activity is changing dramatically across the globe, with uncertain effects on ecosystem processes, especially below‐ground. Fire‐driven losses of soil carbon (C) are often assumed to occur primarily in the upper soil layers because the repeated combustion of above‐ground biomass limits organic matter inputs into surface soil. However, C losses from deeper soil may occur if frequent burning reduces root biomass inputs of C into deep soil layers or stimulates losses of C via leaching and priming. To assess the effects of fire on soil C, we sampled 12 plots in a 51‐year‐long fire frequency manipulation experiment in a temperate oak savanna, where variation in prescribed burning frequency has created a gradient in vegetation structure from closed‐canopy forest in unburned plots to open‐canopy savanna in frequently burned plots. Soil C stocks were nonlinearly related to fire frequency, with soil C peaking in savanna plots burned at an intermediate fire frequency and declining in the most frequently burned plots. Losses from deep soil pools were significant, with the absolute difference between intermediately burned plots versus most frequently burned plots more than doubling when the full 1 m sample was considered rather than the top 0–20 cm alone (losses of 98.5 Mg C/ha [−76%] and 42.3 Mg C/ha [−68%] in the full 1 m and 0–20 cm layers respectively). Compared to unburned forested plots, the most frequently burned plots had 65.8 Mg C/ha (−58%) less C in the full 1 m sample. Root biomass below the top 20 cm also declined by 39% with more frequent burning. Concurrent fire‐driven losses of nitrogen and gains in calcium and phosphorus suggest that burning may increase nitrogen limitation and play a key role in the calcium and phosphorus cycles in temperate savannas. Synthesis . Our results illustrate that fire‐driven losses in soil C and root biomass in deep soil layers may be critical factors regulating the net effect of shifting fire regimes on ecosystem C in forest‐savanna transitions. Projected changes in soil C with shifting fire frequencies in savannas may be 50% too low if they only consider changes in the topsoil.

Minnesota↗
USGS2007

Adapting to the reality of climate change at Glacier National Park, Montana, USA

The glaciers of Glacier National Park (GNP) are disappearing rapidly and likely will be gone by 2030. These alpine glaciers have been continuously present for approximately 7,000 years so their loss from GNP in another 25 years underscores the significance of current climate change. There are presently only 27 glaciers remaining of the 150 estimated to have existed when GNP was created in 1910. Mean annual temperature in GNP has increased 1.6°C during the past century, three times the global mean increase. The temperature increase has affected other parts of the mountain ecosystem, too. Snowpacks hold less water equivalent and melt 2+ weeks earlier in the spring. Forest growth rates have increased, alpine treelines have expanded upward and become denser, and subalpine meadows have been invaded by high elevation tree species. These latter responses can be mostly attributed to longer growing seasons and warmer temperatures. Ecosystem modeling of possible future changes in the GNP mountain environments suggest that increased tree growth rates and evapotranspiration will reduce soil moisture and streamflow. The drier forests, with more wood, will burn more frequently and with greater severity, leading to degradation in air quality and increased risk to people and infrastructure. Management of forest fires is an important issue in the arid western United States. In 2003, 13% of GNP’s 4,082 km 2 was burned in three large fires and numerous smaller fires. Managers can accomplish some of their goals, such as preserving threatened wildlife populations, by altering their management of fires. In 2003, intense efforts were successfully made to divert the fires away from valuable grizzly bear ( Ursus arctos horribilis ) habitat that contained huckleberry plants ( Vaccinium spp .) necessary to ensure bear survival through the winter.

Montana↗
USGS2025

Experimental warming alters free-living nitrogen fixation in a humid tropical forest

Microbial nitrogen (N) fixation accounts for c. 97% of natural N inputs to terrestrial ecosystems. These microbes can be free-living in the soil and leaf litter (asymbiotic) or in symbiosis with plants. Warming is expected to increase N-fixation rates because warmer temperatures favor the growth and activity of N-fixing microbes. We investigated the effects of warming on asymbiotic components of N fixation at a field warming experiment in Puerto Rico. We analyzed the function and composition of bacterial communities from surface soil and leaf litter samples. Warming significantly increased asymbiotic N-fixation rates in soil by 55% (to 0.002 kg ha −1 yr −1 ) and by 525% in leaf litter (to 14.518 kg ha −1 yr −1 ) . This increase in N fixation was associated with changes in the N-fixing bacterial community composition and soil nutrients. Our findings suggest that warming increases the natural N inputs from the atmosphere into this tropical forest due to changes in microbial function and composition, especially in the leaf litter. Given the importance of leaf litter in nutrient cycling, future research should investigate other aspects of N cycles in the leaf litter under warming conditions.

Luquillo Experimental Forest, northeastern Puerto ↗
USGS2023

Proximity to roads does not modify inorganic nitrogen deposition in a topographically complex, high traffic, subalpine forest

Vehicles are an important source for N deposition that may negatively impact roadside ecosystems. While elevated roadside N deposition has been found in many locations, it is not yet known if vehicle emissions cause measurable increases of N deposition in complex, mountainous terrain adjacent to roads. To address this, this study investigated the effect of vehicle N emissions on throughfall (through trees) and open N deposition in a high traffic corridor in mountainous terrain of Rocky Mountain National Park, Colorado, USA. We measured bulk (wet + dry) atmospheric N deposition in throughfall and open samplers along two transects of 750 (throughfall) and 225 (open) m moving away from the road using ion exchange resin (IER) collectors. Contrary to most studies of roadside N deposition, we found no influence of road proximity on inorganic N deposition in throughfall or open sites, possibly due to terrain complexity. Interactions with vegetation modified regional N deposition; throughfall sites had 69% higher nitrate (NO 3 − ) deposition than open sites and larger trees were associated with higher ammonium (NH 4 + ) deposition as compared to smaller trees. When comparing to regional sites that are part of national monitoring networks, we confirmed that our estimates were unaffected by vehicle emissions as our throughfall IER collectors had similar total inorganic N deposition as wet + dry deposition from regional sites (8.64–13.56 vs 10.72–12.14 g N ha −1 day −1 , respectively). These findings do not negate vehicles as a local source of N emissions but suggest elevated N deposition adjacent to busy roads cannot be assumed for complex terrains. Instead, environmental variables may be more important drivers than proximity to roads in topographically complex ecosystems.

Colorado↗
USGS2023

Relative effectiveness of a radionuclide (210Pb), surface elevation table (SET), and LiDAR at monitoring mangrove forest surface elevation change

Sea-level rise (SLR) is one of the greatest future threats to mangrove forests. Mangroves have kept up with or paced past SLR by maintaining their forest floor elevation relative to sea level through root growth, sedimentation, and peat development. Monitoring surface elevation change (SEC) or accretion rates allows us to understand mangrove response to SLR and prioritizes resilient ecosystems for conservation or vulnerable ecosystems for restoration. We compared three methods to measure SEC and accretion in mangrove forests: 210 Pb, surface elevation tables (SETs), and a terrestrial light detection and ranging system (compact biomass LiDAR—CBL). Lead-210 accretion rates were not significantly different than SET SEC rates and differences between the two methods (− 2 to 2 mm/year) were within the error of our measurements. Lead-210 only measures accretion in the upper meter of sediment and cannot capture deeper subsurface processes (e.g., subsidence, compaction) that SETs can. The lack of differences suggests the following: (1) surface processes in the active root zone are influencing forest floor elevation more than subsurface processes, (2) subsurface processes were not large enough to effect elevation, or (3) the SETs were not installed deep enough to capture subsurface processes. CBL SEC rates did not differ significantly from SET SEC rates. The larger spatial scale of the CBL scans resulted in significantly different SEC rates from some of the plots. This was due to the CBL measuring areas missed by the SET. The greater number of points measured by CBL (~ 30,000 vs 36) increased precision and lowered standard error. The traditional SET/rSET method is currently 3–10 × cheaper than the 210 Pb or CBL method, respectively, and can accurately track changes in forest floor elevation. Costs of the use of LiDAR are likely to decrease in the future with the advent of newer and more cost-effective technology.

Estuaries and Coasts↗
USGS1991

Chloride cycling in two forested lake watersheds in the west-central Adirondack Mountains, New York, U.S.A.

The chemistry of precipitation, throughfall, soil water, ground water, and surface water was evaluated in two forested lake-watersheds over a 4-yr period to assess factors controlling C1- cycling. Results indicate that C1- cycling in these watersheds is more complex than the generally held view of the rapid transport of atmospherically derived C1- through the ecosystem. The annual throughfall Cl- flux for individual species in the northern hardwood forest was 2 to 5 times that of precipitation (56 eq ha-1), whereas the Na+ throughfall flux, in general, was similar to the precipitation flux. Concentrations of soil-water Cl- sampled from ceramic tension lysimeters at 20 cm below land surface generally exceeded the Na+ concentrations and averaged 31 ??eq L-1, the highest of any waters sampled in the watersheds, except throughfall under red spruce which averaged 34 ??eq L-1. Chloride was concentrated prior to storms and mobilized rapidly during storms as suggested by increases in streamwater Cl- concentrations with increasing flow. Major sources of Cl- in both watersheds are the forest floor and hornblende weathering in the soils and till. In the Panther Lake watershed, which contains mainly thick deposits of till( > 3 m), hornblende weathering results in a net Cl- flux 3 times greater than that in the Woods Lake watershed, which contains mainly thin deposits of till. The estimated accumulation rate of Cl- in the biomass of the two watersheds was comparable to the precipitation Cl- flux.The chemistry of precipitation, throughfall, soil water, ground water, and surface water was evaluated in two forested lake-watersheds over a 4-yr period to assess factors controlling Cl- cycling. Results indicate that Cl- cycling in these watersheds is more complex than the generally held view of the rapid transport of atmospherically derived Cl- through the excosystem. The annual throughfall Cl- flux for individual species in the northern hardwood forest was 2 to 5 times that of precipitation (56 eq ha-1), whereas the Na+ throughfall flux, in general, was similar to the precipitation flux. Concentrations of soil-water Cl- sampled from ceramic tension lysimeters at 20 cm below land surface generally exceeded the Na+ concentrations and averaged 31 ??eq L-1, the highest of any waters sampled in the watersheds, except throughfall under red spruce which averaged 34 ??eq L-1. Chloride was concentrated prior to storms and mobilized rapidly during storms as suggested by increases in streamwater Cl- concentrations with increasing flow. Major sources of Cl- in both watersheds are the forest floor and hornblende weathering in the soils and till. In the Panther Lake watershed, which contains mainly thick deposits of till (> 3 m), hornblende weathering results in a net Cl- flux 3 times greater than that in the Woods Lake watershed, which contains mainly thin deposits of till. The estimated accumulation rate of Cl- in the biomass of the two watersheds was comparable to the precipitation Cl- flux.

Water, Air, & Soil Pollution↗
USGS2021

Hawai‘i forest review: Synthesizing the ecology, evolution, and conservation of a model system

As the most remote archipelago in the world, the Hawaiian Islands are home to a highly endemic and disharmonic biota that has fascinated biologists for centuries. Forests are the dominant terrestrial biome in Hawai‘i, spanning complex, heterogeneous climates across substrates that vary tremendously in age, soil structure, and nutrient availability. Species richness is low in Hawaiian forests compared to other tropical forests, as a consequence of dispersal limitation from continents and adaptive radiations in only some lineages, and forests are dominated by the widespread Metrosideros species complex. Low species richness provides a relatively tractable model system for studies of community assembly, local adaptation, and species interactions. Moreover, Hawaiian forests provide insights into predicted patterns of evolution on islands, revealing that while some evidence supports “island syndromes,” there are exceptions to them all. For example, Hawaiian plants are not as a whole less defended against herbivores, less dispersible, more conservative in resource use, or more slow-growing than their continental relatives. Clearly, more work is needed to understand the drivers, sources, and constraints on phenotypic variation among Hawaiian species, including both widespread and rare species, and to understand the role of this variation for ecological and evolutionary processes, which will further contribute to conservation of this unique biota. Today, Hawaiian forests are among the most threatened globally. Resource management failures – the proliferation of non-native species in particular – have led to devastating declines in native taxa and resulted in dominance by novel species assemblages. Conservation and restoration of Hawaiian forests now rely on managing threats including climate change, ongoing species introductions, novel pathogens, lost mutualists, and altered ecosystem dynamics through the use of diverse tools and strategies grounded in basic ecological, evolutionary, and biocultural principles. The future of Hawaiian forests thus depends on the synthesis of ecological and evolutionary research, which will continue to inform future conservation and restoration practices.

Hawaii↗