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At least 721 records · Page 40Linked to original sources
USGS1991

Effects of submersed macrophytes on dissolved oxygen, pH and temperature under different conditions of wind, tide and bed structure

Seasonal data on diurnal dissolved-oxygen concentration (DO), pH, temperature and chlorophyll-a were collected and species composition and vertical structure of macrophyte beds were analyzed in the tidal Potomac River during the 1987 growing season. The relationships among these variables and physical and climatic factors were analyzed. Elevated surface temperatures, DO and pH were found in macrophyte beds in June and August; surface temperatures were also elevated in the dense Hydrilla verticillata dominated bed in October-November after senescence had begun. Bottom DO, pH and temperature were lower than surface values. Bottom temperatures in vegetated sites were highly variable compared with bottom temperatures in unvegetated sites.

Journal of Freshwater Ecology↗
USGS2026

Lost in translation: Reconciling different streamflow permanence data products

The objective of this study is to provide a framework to reconcile streamflow permanence products that provide information on whether a stream is perennial or nonperennial. Accurate classification of streams as perennial or nonperennial is important for a variety of land and water resource management decisions. However, resource managers are challenged with how to reconcile different streamflow permanence information to determine if it is sufficient to avoid field verification, which can be prohibitively costly and time consuming. The study evaluates two datasets for the Pacific Northwest Region, U.S., the National Hydrography Dataset Plus High Resolution (NHDPlus HR) hydrographic classification and the PRObability of Streamflow PERmanence (PROSPER) model output, which differ in structure, output type, and temporal and spatial resolution. The framework includes a two-level evaluation that involves assessing agreement between the two datasets and evaluating the reliability of the two datasets. Summarized at a regional scale, the two datasets agree for 68% of flowlines with higher agreement for nonperennial streams. PROSPER nonperennial stream classifications may be considered generally reliable in arid regions relative to other ecoregions within the Pacific Northwest study area but less reliable for high elevation mountain regions and larger streams and rivers. More than 75% of NHDPlusHR classifications may be considered reliable when evaluating reliability based on approximate climate conditions associated with the year that the NHDPlus HR classification was assigned. The decision procedure is reproducible, flexible to varying criteria of end user applications, and is intended to help provide cost saving opportunities for land managers by providing information for more strategic field verification of streamflow class determination based on available yet imperfect data sources.

California, Idaho, Montana, Nevada, Utah, Washingt↗
USGS2010

The role of C 3 and C 4 grasses to interannual variability in remotely sensed ecosystem performance over the US Great Plains

Time integrated normalized difference vegetation index (ΣNDVI) derived from National Oceanic and Atmospheric Administration (NOAA) Advanced Very High Resolution Radiometer (AVHRR) multi-temporal imagery over a 10-year period (1989–1998) was used as a surrogate for primary production to investigate the impact of interannual climate variability on grassland performance for central and northern US Great Plains. First, the contribution of C 3 and C 4 species abundance to the major grassland ecosystems of the US Great Plains is described. Next, the relation between mean ΣNDVI and the ΣNDVI coefficient of variation (CV ΣNDVI) used as a proxy for interannual climate variability is analysed. Results suggest that the differences in the long-term climatic control over ecosystem performance approximately coincide with changes between C 3 - and C 4 -dominant grassland classes. Variation in remotely sensed net primary production over time is higher for the southern and western plains grasslands (primarily C 4 grasslands), whereas the C 3 -dominated classes in the northern and eastern portion of the US Great Plains, generally show lower CV ΣNDVI values.

International Journal of Remote Sensing↗
USGS2024

Automated Cropland Fallow Algorithm (ACFA) for the Northern Great Plains of USA

Cropland fallowing is choosing not to plant a crop during a season when a crop is normally planted. It is an important component of many crop rotations and can improve soil moisture and health. Knowing which fields are fallow is critical to assess crop productivity and crop water productivity, needed for food security assessments. The annual spatial extent of cropland fallows is poorly understood within the United States (U.S.). The U.S. Department of Agriculture Cropland Data Layer does provide cropland fallow areas; however, at a significantly lower confidence than their cropland classes. This study developed a methodology to map cropland fallows within the Northern Great Plains region of the U.S. using an easily implementable decision tree algorithm leveraging training and validation data from wet (2019), normal (2015), and dry (2017) precipitation years to account for climatic variability. The decision trees automated cropland fallow algorithm (ACFA) was coded on a cloud platform utilizing remotely sensed, time-series data from the years 2010–2019 to separate cropland fallows from other land cover/land use classes. Overall accuracies varied between 96%-98%. Producer’s and user’s accuracies of cropland fallow class varied between 70-87%.

International Journal of Digital Earth↗
USGS2016

How will predicted land-use change affect waterfowl spring stopover ecology? Inferences from an individual-based model

Habitat loss, habitat fragmentation, overexploitation and climate change pose familiar and new challenges to conserving natural populations throughout the world. One approach conservation planners may use to evaluate the effects of these challenges on wildlife populations is scenario planning. We developed an individual-based model to evaluate the effects of future land use and land cover changes on spring-migrating dabbling ducks in North America. We assessed the effects of three Intergovernmental Panel on Climate Change emission scenarios (A1B, A2 and B1) on dabbling duck stopover duration, movement distances and mortality. We specifically focused on migration stopover duration because previous research has demonstrated that individuals arriving earlier on the nesting grounds exhibit increased reproductive fitness. Compared to present conditions, all three scenarios increased stopover duration and movement distances of agent ducks. Although all three scenarios presented migrating ducks with increased amounts of wetland habitat, scenarios also contained substantially less cropland, which decreased overall carrying capacity of the study area. Synthesis and applications . Land-use change may increase waterfowl spring migration stopover duration in the midcontinent region of North America due to reduced landscape energetic carrying capacity. Climate change will alter spatial patterns of crop distributions with corn and rice production areas shifting to different regions. Thus, conservation planners will have to address population-level energetic implications of shifting agricultural food resources and increased uncertainty in yearly precipitation patterns within the next 50 years.

Journal of Applied Ecology↗
USGS2021

More than one way to kill a spruce forest: The role of fire and climate in the late-glacial termination of spruce woodlands across the southern Great Lakes

In the southern Great Lakes Region, North America, between 19,000 and 8,000 years ago, temperatures rose by 2.5–6.5°C and spruce Picea forests/woodlands were replaced by mixed-deciduous or pine Pinus forests. The demise of Picea forests/woodlands during the last deglaciation offers a model system for studying how changing climate and disturbance regimes interact to trigger declines of dominant species and vegetation-type conversions. The role of rising temperatures in driving the regional demise of Picea forests/woodlands is widely accepted, but the role of fire is poorly understood. We studied the effect of changing fire activity on Picea declines and rates of vegetation composition change using fossil pollen and macroscopic charcoal from five high-resolution lake sediment records. The decline of Picea forests/woodlands followed two distinct patterns. At two sites (Stotzel-Leis and Silver Lake), fire activity reached maximum levels during the declines and both charcoal accumulation rates and fire frequency were significantly and positively associated with vegetation composition change rates. At these sites, Picea declined to low levels by 14 kyr BP and was largely replaced by deciduous hardwood taxa like ash Fraxinus , hop-hornbeam/hornbeam Ostrya/Carpinus and elm Ulmus . However, this ecosystem transition was reversible, as Picea re-established at lower abundances during the Younger Dryas. At the other three sites, there was no statistical relationship between charcoal accumulation and vegetation composition change rates, though fire frequency was a significant predictor of rates of vegetation change at Appleman Lake and Triangle Lake Bog. At these sites, Picea declined gradually over several thousand years, was replaced by deciduous hardwoods and high levels of Pinus and did not re-establish during the Younger Dryas. Synthesis . Fire does not appear to have been necessary for the climate-driven loss of Picea woodlands during the last deglaciation, but increased fire frequency accelerated the decline of Picea in some areas by clearing the way for thermophilous deciduous hardwood taxa. Hence, warming and intensified fire regimes likely interacted in the past to cause abrupt losses of coniferous forests and could again in the coming decades.

Indiana, Michigan, Ohio↗
USGS2003

Lake Ontario: Food web dynamics in a changing ecosystem (1970-2000)

We examined stressors that have led to profound ecological changes in the Lake Ontario ecosystem and its fish community since 1970. The most notable changes have been reductions in phosphorus loading, invasion by Dreissena spp., fisheries management through stocking of exotic salmonids and control of sea lamprey ( Petromyzon marinus ), and fish harvest by anglers and double-crested cormorants ( Phalacrocorax auritus ). The response to these stressors has led to ( i ) declines in both algal photosynthesis and epilimnetic zooplankton production, ( ii ) decreases in alewife ( Alosa pseudoharengus ) abundance, ( iii ) declines in native Diporeia and lake whitefish ( Coregonus clupeaformis ), ( iv ) behavioral shifts in alewife spatial distribution benefitting native lake trout ( Salvelinus namaycush ), threespine stickleback ( Gasterosteus aculeatus ), and emerald shiner ( Notropis atherinoides ) populations, ( v ) dramatic increases in water clarity, ( vi ) predation impacts by cormorants on select fish species, and ( vii ) lake trout recruitment bottlenecks associated with alewife-induced thiamine deficiency. We expect stressor responses associated with anthropogenic forces like exotic species invasions and global climate warming to continue to impact the Lake Ontario ecosystem in the future and recommend continuous long-term ecological studies to enhance scientific understanding and management of this important resource.

Canadian Journal of Fisheries and Aquatic Sciences↗
USGS2006

Multiphase, multicomponent parameter estimation for liquid and vapor fluxes in deep arid systems using hydrologic data and natural environmental tracers

Multiphase, multicomponent numerical models of long-term unsaturated-zone liquid and vapor movement were created for a thick alluvial basin at the Nevada Test Site to predict present-day liquid and vapor fluxes. The numerical models are based on recently developed conceptual models of unsaturated-zone moisture movement in thick alluvium that explain present-day water potential and tracer profiles in terms of major climate and vegetation transitions that have occurred during the past 10 000 yr or more. The numerical models were calibrated using borehole hydrologic and environmental tracer data available from a low-level radioactive waste management site located in a former nuclear weapons testing area. The environmental tracer data used in the model calibration includes tracers that migrate in both the liquid and vapor phases (δD, δ 18 O) and tracers that migrate solely as dissolved solutes (Cl), thus enabling the estimation of some gas-phase as well as liquid-phase transport parameters. Parameter uncertainties and correlations identified during model calibration were used to generate parameter combinations for a set of Monte Carlo simulations to more fully characterize the uncertainty in liquid and vapor fluxes. The calculated background liquid and vapor fluxes decrease as the estimated time since the transition to the present-day arid climate increases. However, on the whole, the estimated fluxes display relatively little variability because correlations among parameters tend to create parameter sets for which changes in some parameters offset the effects of others in the set. Independent estimates on the timing since the climate transition established from packrat midden data were essential for constraining the model calibration results. The study demonstrates the utility of environmental tracer data in developing numerical models of liquid- and gas-phase moisture movement and the importance of considering parameter correlations when using Monte Carlo analysis to characterize the uncertainty in moisture fluxes.

Vadose Zone Journal↗
USGS2023

Combining expert knowledge of a threatened trout distribution with sparse occupancy data for climate-related projection

Objective To evaluate the vulnerability of Bull Trout Salvelinus confluentus to potential climate changes across its range in Oregon, we compiled disparate expert knowledge of the distribution of spawning and rearing and combined these probabilistic statements as data along with documented records of breeding and rearing in a joint occupancy model. Methods The joint expert knowledge–occupancy model, which was based on discrete patches of cold water (≤13°C) suitable for spawning and rearing, permitted the association of true occupancy with climate and other explanatory variables while accounting for variation in detection probability. We then applied estimated relationships of patch occupancy with explanatory variables to projected coldwater patch configurations in the years 2040 and 2080. Result Projections of the kilometers of occupied coldwater patch in future decades suggest precipitous declines if current relationships of occupancy with environmental variables are maintained. Impacts of climate changes in future decades manifest directly through the outright loss of coldwater patches and increases in winter high flows but also indirectly by increased isolation. Conclusion Combining probabilistic statements of species distributions from knowledgeable experts with sparse occupancy data may be a robust and timely alternative when large numbers of repeated occupancy surveys are infeasible.

Oregon↗
USGS2003

Climate change and Arctic ecosystems: 1. Vegetation changes north of 55°N between the last glacial maximum, mid-Holocene, and present

A unified scheme to assign pollen samples to vegetation types was used to reconstruct vegetation patterns north of 55??N at the last glacial maximum (LGM) and mid-Holocene (6000 years B.P.). The pollen data set assembled for this purpose represents a comprehensive compilation based on the work of many projects and research groups. Five tundra types (cushion forb tundra, graminoid and forb tundra, prostrate dwarf-shrub tundra, erect dwarf-shrub tundra, and low- and high-shrub tundra) were distinguished and mapped on the basis of modern pollen surface samples. The tundra-forest boundary and the distributions of boreal and temperate forest types today were realistically reconstructed. During the mid-Holocene the tundra-forest boundary was north of its present position in some regions, but the pattern of this shift was strongly asymmetrical around the pole, with the largest northward shift in central Siberia (???200 km), little change in Beringia, and a southward shift in Keewatin and Labrador (???200 km). Low- and high-shrub tundra extended farther north than today. At the LGM, forests were absent from high latitudes. Graminoid and forb tundra abutted on temperate steppe in northwestern Eurasia while prostrate dwarf-shrub, erect dwarf-shrub, and graminoid and forb tundra formed a mosaic in Beringia. Graminoid and forb tundra is restricted today and does not form a large continuous biome, but the pollen data show that it was far more extensive at the LGM, while low- and high-shrub tundra were greatly reduced, illustrating the potential for climate change to dramatically alter the relative areas occupied by different vegetation types.

Journal of Geophysical Research D: Atmospheres↗
USGS1996

Potential climatic impacts of vegetation change: A regional modeling study

The human species has been modifying the landscape long before the development of modern agrarian techniques. Much of the land area of the conterminous United States is currently used for agricultural production. In certain regions this change in vegetative cover from its natural state may have led to local climatic change. A regional climate version of the Colorado State University Regional Atmospheric Modeling System was used to assess the impact of a natural versus current vegetation distribution on the weather and climate of July 1989. The results indicate that coherent regions of substantial changes, of both positive and negative sign, in screen height temperature, humidity, wind speed, and precipitation are a possible consequence of land use change throughout the United States. The simulated changes in the screen height quantities were closely related to changes in the vegetation parameters of albedo, roughness length, leaf area index, and fractional coverage.

Journal of Geophysical Research D: Atmospheres↗
USGS2015

Plant-plant interactions in a subtropical mangrove-to-marsh transition zone: effects of environmental drivers

Questions Does the presence of herbaceous vegetation affect the establishment success of mangrove tree species in the transition zone between subtropical coastal mangrove forests and marshes? How do plant–plant interactions in this transition zone respond to variation in two primary coastal environmental drivers? Location Subtropical coastal region of the southern United States. Methods We conducted a greenhouse study to better understand how abiotic factors affect plant species interactions in the mangrove-to-marsh transition zone, or ecotone. We manipulated salinity (fresh, brackish or salt water) and hydrologic conditions (continuously saturated or 20-cm tidal range) to simulate ecotonal environments. Propagules of the mangroves Avicennia germinans and Laguncularia racemosa were introduced to mesocosms containing an established marsh community. Both mangrove species were also introduced to containers lacking other vegetation. We monitored mangrove establishment success and survival over 22 mo. Mangrove growth was measured as stem height and above-ground biomass. Stem height, stem density and above-ground biomass of the dominant marsh species were documented. Results Establishment success of A. germinans was reduced under saturated saltwater conditions, but establishment of L. racemosa was not affected by experimental treatments. There was complete mortality of A. germinans in mesocosms under freshwater conditions, and very low survival of L. racemosa . In contrast, survival of both species in monoculture under freshwater conditions exceeded 62%. The marsh species Distichlis spicata and Eleocharis cellulosa suppressed growth of both mangroves throughout the experiment, whereas the mangroves did not affect herbaceous species growth. The magnitude of growth suppression by marsh species varied with environmental conditions; suppression was often higher in saturated compared to tidal conditions, and higher in fresh and salt water compared to brackish water. Conclusions Our results indicate that herbaceous marsh species can suppress mangrove early seedling growth. Depending on species composition and density, marsh plants can slow mangrove landward migration under predicted climate change scenarios as salinity in freshwater and oligohaline wetlands increases with rising sea levels. Change in the relative coverage of mangrove forests and marshes will depend on both the ability of marsh species to migrate further inland as mangroves advance, and the ability of shoreline mangroves to adjust to rising sea level through accretionary processes.

Journal of Vegetation Science↗
USGS2026

Patterns of recent brook trout invasion in bull trout streams in relation to habitat, source connectivity, biotic resistance, and disturbance

Knowledge of which habitats are at risk of invasion by nonnative species is essential to conservation, but a changing climate often complicates assessments of where future invasions may occur. Nonnative brook trout Salvelinus fontinalis threaten cold-adapted native salmonids throughout western North America, and the extent of future invasions in coldwater streams is recognized as an area of uncertainty with important consequences. We addressed this uncertainty using spatial-stream-network (SSN) modeling to develop a species distribution model (SDM) for brook trout in Idaho, creating high-resolution prediction maps of suitable (i.e., invadable) habitat under baseline (1990–2015) and future (2080s) climate scenarios, and querying predictions within natal bull trout S. confluentus habitat patches (stream–subwatershed scale) for each scenario. Results indicated that brook trout will experience a net loss of suitable habitat in Idaho, but a large increase of suitable habitat in cold streams. The total proportion of bull trout habitat invadable by brook trout increased from 0.33 during the baseline scenario to 0.44 during the future scenario—a result of upstream expansions of brook trout habitat that were partially offset by contractions in bull trout habitat. Changes in the proportion of invadable habitat varied widely among bull trout patches. Between scenarios, the largest increases in suitable habitat occurred in small, low-gradient, unconfined streams with mean August water temperatures of 7–9 °C during the baseline period. A relatively small proportion of patches contained the majority of invadable habitat in both scenarios, particularly patches in “U-shaped” glacial valleys. A changing climate will broadly increase the threat that brook trout pose to bull trout, but the degree of change experienced by individual populations will vary with local context. The high-resolution prediction maps created by our SSN model will help conservation planners identify and prioritize control efforts on the small proportion of brook trout populations that most threaten bull trout.

Idaho↗
USGS2007

Modelingevapotranspirationina sub-tropical climate

Evapotranspiration (ET) loss is estimated at about 80-85% of annual precipitation in South Florida. Accurate prediction of ET is important during and beyond the implementation of the Comprehensive Everglades Restoration Plan (CERP). In the USDA's Everglades Agro-Hydrology Model (EAHM) the soil water intake is linked with the soil water redistribution, soil evaporation, plant transpiration, subsurface lateral flow and subsurface drainage to calculate daily root zone soil water content. Hydrometeorological data from three sites with different soil moisture content and vegetal cover were used to evaluate the EAHM ET routine. In general, the EAHM water balance sub-model simulated the daily ET with acceptable accuracy in the area with standing water (Everglades) while using the Penman method. However, in the area with grass cover, there was a discrepancy between the model simulated and measured ET using either the Penman or the Priestley-Taylor method. The results indicated that in the region with two distinct climate patterns: dry (low humidity, more wind, and less precipitation) and wet (high humidity, less wind and more rainfall) such as South Florida, a combination method like Penman should be used for prediction of daily ET. However, in order to improve the predictability of the ET methods, information about surface albedo is needed for land surfaces with grass vegetation during the growing season.

Journal of Environmental Hydrology↗
USGS2021

Is there enough water? How bearish and bullish outlooks are linked to decision-maker perspectives on environmental flows

Policies that mandate environmental flows (e-flows) can be powerful tools for freshwater conservation, but implementation of these policies faces many hurdles. To better understand these challenges, we explored two key questions: (1) What additional data are needed to implement e-flows? and (2) What are the major socio-political barriers to implementing e-flows? We surveyed water and natural resource decision makers in the semi-arid Red River basin, Texas-Oklahoma, USA, and used social network analysis to analyze their communication patterns. Most respondents agreed that e-flows can provide important benefits and identified the same data needs. However, respondents sharply in their beliefs on other issues, and a clustering analysis revealed two distinct groups of decision makers. One cluster of decision makers tended to be bearish, or pessimistic, and believed that: current flow conditions are not adequate, there are many serious socio-political barriers to implementation, water conflicts will likely increase in the future, and climate change is likely to exacerbate these issues. The other cluster of respondents was bullish, or optimistic: they foresaw fewer future water conflicts and fewer socio-political barriers to implementation. Despite these differences, both clusters largely identified the same data needs and barriers to e-flows implementation. Our social network analysis revealed that the frequency of communication between clusters was not significantly different than the frequency of communication within clusters. Overall, our results suggest that the different perspectives of decision-makers could complicate efforts to implement e-flows and proactively plan for climate change. However, there are opportunities for collaboration on addressing common data needs and barriers to implementation. Overall, our study provides a key socio-environmental perspective on e-flows implementation from a semi-arid and socio-politically complex river basin and contextualizes the many challenges facing e-flows implementation in river basins globally.

Journal of Environmental Management↗
USGS2019

Hydrologic resilience from summertime fog and recharge: A case study for coho salmon recovery planning

Fog and low cloud cover (FLCC) and late summer recharge increase stream baseflow and decrease stream temperature during arid Mediterranean climate summers, which benefits salmon especially under climate warming conditions. The potential to discharge cool water to streams during the late summer (hydrologic capacity; HC) furnished by FLCC and recharge were mapped for the 299 subwatersheds ranked Core, Phase 1, or Phase 2 under the National Marine Fisheries Service Recovery Plan that prioritized restoration and threat abatement action for endangered Central California Coast Coho Salmon evolutionarily significant unit. Two spatially continuous gridded datasets were merged to compare HC: average hrs/day FLCC, a new dataset derived from a decade of hourly National Weather Satellite data, and annual average mm recharge from the USGS Basin Characterization Model. Two use‐case scenarios provide examples of incorporating FLCC‐driven HC indices into long‐term recovery planning. The first, a thermal analysis under future climate, projected 65% of the watershed area for 8–19 coho population units as thermally inhospitable under two global climate models and identified several units with high resilience (high HC under the range of projected warming conditions). The second use case investigated HC by subwatershed rank and coho population, and identified three population units with high HC in areas ranked Phase 1 and 2 and low HC in Core. Recovery planning for cold‐water fish species would benefit by including FLCC in vulnerability analyses.

California↗
USGS2024

Projected changes in mangrove distribution and vegetation structure under climate change in the southeastern United States

Aim The climate change-induced transition from grass-dominated marshes to woody-plant-dominated mangrove forests has the potential to impact the ecosystem goods and services provided by coastal wetlands. To better anticipate and prepare for these impacts, there is a need to advance understanding of future changes in mangrove distribution and coastal wetland vegetation structural properties due to warming winters. Location Southeastern United States. Time Period Recent (1981–2010) and future (2071–2100). Major Taxa Studied Coastal wetland vegetation. Methods We estimated changes in mangrove distribution and coastal wetland vegetation structure using known climate-ecological relationships, recent climate data for the period 1981–2010, and future projected climate data for the period 2071–2100. We quantified potential changes in mangrove presence, mangrove relative abundance, coastal wetland vegetation height, and coastal wetland vegetation aboveground biomass under two Shared Socio-Economic Pathway scenarios (SSPs; SSP2-4.5 and SSP5-8.5), which correspond to intermediate and high greenhouse gas emissions scenarios, respectively. Results Our analyses indicate that mangrove presence and relative abundance will dramatically increase in the northern Gulf of Mexico and the southeast Atlantic coast of the United States, particularly under the high emissions scenario. Because of the higher stature of mangroves relative to salt marsh vegetation, this expansion will cause a transformative change in coastal wetland vegetation height and aboveground biomass in many areas. However, along the arid southern Texas coast, low precipitation and high salinities are expected to constrain mangrove expansion and growth. Main Conclusions Our results show where and to what extent climate change, in the form of winter temperature warming, is projected to enable the transition from shorter, grass-dominated salt marshes to taller, woody plant-dominated mangrove forests in the southeastern United States, with consequent impacts on ecosystem goods and services.

Journal of Biogeography↗
USGS2007

A stand-replacing fire history in upper montane forests of the southern Rocky Mountains

Dendroecological techniques were applied to reconstruct stand-replacing fire history in upper montane forests in northern New Mexico and southern Colorado. Fourteen stand-replacing fires were dated to 8 unique fire years (1842–1901) using four lines of evidence at each of 12 sites within the upper Rio Grande Basin. The four lines of evidence were ( i ) quaking aspen ( Populus tremuloides Michx.) inner-ring dates, ( ii ) fire-killed conifer bark-ring dates, ( iii ) tree-ring width changes or other morphological indicators of injury, and ( iv ) fire scars. The annual precision of dating allowed the identification of synchronous stand-replacing fire years among the sites, and co-occurrence with regional surface fire events previously reconstructed from a network of fire scar collections in lower elevation pine forests across the southwestern United States. Nearly all of the synchronous stand-replacing and surface fire years coincided with severe droughts, because climate variability created regional conditions where stand-replacing fires and surface fires burned across ecosystems. Reconstructed stand-replacing fires that predate substantial Anglo-American settlement in this region provide direct evidence that stand-replacing fires were a feature of high-elevation forests before extensive and intensive land-use practices (e.g., logging, railroad, and mining) began in the late 19th century.

Canadian Journal of Forest Research↗