Range Of Natural Variability Research Articles

Nonlinear rise in Greenland runoff in response to post-industrial Arctic warming.

The Greenland ice sheet (GrIS) is a growing contributor to global sea-level rise1, with recent ice mass loss dominated by surface meltwater runoff2,3. Satellite observations reveal positive trends in GrIS surface melt extent4, but melt variability, intensity and runoff remain uncertain before the satellite era. Here we present the first continuous, multi-century and observationally constrained record of GrIS surface melt intensity and runoff, revealing that the magnitude of recent GrIS melting is exceptional over at least the last 350 years. We develop this record through stratigraphic analysis of central west Greenland ice cores, and demonstrate that measurements of refrozen melt layers in percolation zone ice cores can be used to quantifiably, and reproducibly, reconstruct past melt rates. We show significant (P < 0.01) and spatially extensive correlations between these ice-core-derived melt records and modelled melt rates5,6 and satellite-derived melt duration4 across Greenland more broadly, enabling the reconstruction of past ice-sheet-scale surface melt intensity and runoff. We find that the initiation of increases in GrIS melting closely follow the onset of industrial-era Arctic warming in the mid-1800s, but that the magnitude of GrIS melting has only recently emerged beyond the range of natural variability. Owing to a nonlinear response of surface melting to increasing summer air temperatures, continued atmospheric warming will lead to rapid increases in GrIS runoff and sea-level contributions.

Relations of interannual differences in stream litter breakdown with discharge: bioassessment implications

AbstractEcosystem‐level processes are increasingly used by researchers and managers as indicators of ecological integrity for bioassessment, particularly in streams. However, processes like litter breakdown integrate multiple mechanistic pathways, which can vary differentially even under natural, unimpacted conditions. In particular, weather‐driven hydrologic variations may strongly influence invertebrate shredder feeding and physical abrasion, inducing high natural variability of litter breakdown rates, which may obscure the effects of anthropogenic disturbances. Yet, such variability is rarely assessed to refine benchmarks of ecological status. Here, we quantified how interannual hydrologic differences contributed to the spatio‐temporal variability of litter breakdown rate and its components (fragmentation, λF; and dissolution and microbial decomposition, λm), in low‐order unimpacted, perennial streams across three climatically similar regions in temperate Canada. We measured litter breakdown rates in coarse (5 or 10 mm; kc)‐ and fine‐mesh (0.5 mm; kf) leaf bags during fall for 2–4 yr and used variance partitioning to disentangle the variation of kc, λF, and λm, as explained by hydrologic indices (during and prior to leaf bag incubation), decomposer‐related variables, and water chemistry. Contrary to our hypotheses, interannual hydrologic variability was unrelated to λF, and poorly predicted λm and kc within regions. Within‐region spatial (i.e., across sites in a year) and temporal (across years at a site) differences in kc approximated or exceeded the range of natural variability suggested to characterize reference conditions by a popular bioassessment framework. Accordingly, we recommend site‐ and region‐specific modifications of benchmarks for reference conditions that account for interannual variability, while cautioning about their potential non‐stationarity under climate change. Composite parameters such as kc/kf and λF/λm were substantially more variable across sites, and hence are not robust assessment parameters. As the range of natural variability of litter breakdown revealed in this study can overlap with the average impacts of certain anthropogenic disturbances (e.g., nutrient enrichment) on this parameter reported by previous research, we emphasize the need to include other structural and functional indicators to ensure comprehensive stream bioassessments.

Using paleoecology to improve reference conditions for ecosystem-based management in western spruce-moss subdomain of Québec

Ecosystem based management in Québec is framed by reference conditions defining percentage of old-growth forest (>100-years-old) and forest composition characterizing pre-industrial forest landscapes. In the western spruce-moss bioclimatic subdomain (154 184 km2) a fire cycle estimated at 150 years was used to target that 49% of the landscape has to be composed of old-growth forest. Yet, this target was developed using past (19th–20th C.) climate and vegetation data and assume that environment and ecosystem processes are homogeneous for the entire western spruce-moss bioclimatic subdomain. The wide spatial and narrow temporal windows limit the application of reference conditions under ongoing climate change.Our aim was to classify current vegetation heterogeneity of the western spruce-moss subdomain into homogeneous zones and to study the long-term history of fire and vegetation within these zones. This approach will help to refine forest management targets that are based upon short-term records by providing a long-term perspective that is needed for the forests to be managed within their natural range of variability. Modern forest inventories data were used along with climate, physical variables, and natural and human disturbances to study the current vegetation-environment interactions among the western spruce-moss subdomain. We also used 18 published sedimentary pollen and charcoal series to reconstruct Holocene vegetation and Fire Return Intervals (FRI).Contemporary data revealed 4 zones with homogeneous interactions between vegetation and environment. Pollen analysis revealed three long-term vegetation paths: early successional species dominance, late to early species transition and late successional species dominance. These suggest that modern forest composition results from Holocene trajectories occurring within each zone. Holocene mean FRI (mFRI) ranged from 222 to 258 years across the subdomain, resulting in old-growth forests ranging between 64% and 68%, depending upon the zone.Paleoecological and contemporary results support that to make forest management more sustainable, current landscape heterogeneity that arises from millennial forest composition trajectories and fire cycle dynamics should be taken into account by down-scaling the previously established reference conditions.

Have some landscapes in the eastern Canadian boreal forest moved beyond their natural range of variability?

BackgroundIn the context of ecosystem management, the present study aims to compare the natural and the present-day forested landscapes of a large territory in Quebec (Canada). Using contemporary and long-term fire cycles, each natural forest landscape is defined according to the variability of its structure and composition, and compared to the present-day landscape. This analysis was conducted to address the question of whether human activities have moved these ecosystems outside the range of natural landscape variability.MethodsThe study encompassed a forested area of 175 000 km2 divided into 14 landscapes. Using a framework that integrates fire cycles, age structure and forest dynamics, we characterized the forest composition and age structures that resulted from three historical fire cycles (110, 140, and 180 years) representative of the boreal forest of eastern Canada. The modeled natural landscapes were compared with present-day landscapes in regard to the proportion of old-growth forests (landscape level) and the proportion of late-successional forest stands (landscape level and potential vegetation type).ResultsFour landscapes (39%) remain within their natural range of variability. In contrast, nine landscapes (54%) show a large gap between natural and present-day landscapes. These nine are located in the southern portion of the study area, and are mainly associated with Abies-Betula vegetation where human activities have contributed to a strong increase in the proportion of Populus tremuloides stands (early-successional stages) and a decrease of old-growth forest stands (more than 100 years old). A single landscape (7%), substantially changed from its potential natural state, is a candidate for adaptive-based management.ConclusionComparison of corresponding natural (reference conditions) and present-day landscapes showed that ten landscapes reflecting an important shift in forest composition and age structure could be considered beyond the range of their natural variability. The description of a landscape’s natural variability at the scale of several millennia can be considered a moving benchmark that can be re-evaluated in the context of climate change. Focusing on regional landscape characteristics and long-term natural variability of vegetation and forest age structure represents a step forward in methodology for defining reference conditions and following shifts in landscape over time.

Six Centuries of Upper Indus Basin Streamflow Variability and Its Climatic Drivers

Our understanding of the full range of natural variability in streamflow, including how modern flow compares to the past, is poorly understood for the Upper Indus Basin (UIB) because of short instrumental gauge records. To help address this challenge, we use Hierarchical Bayesian Regression (HBR) with partial pooling to develop six centuries long (1394-2008 C.E.) streamflow reconstructions at three UIB gauges (Doyian, Gilgit, and Kachora), concurrently demonstrating that HBR can be used to reconstruct short records with interspersed missing data. At one gauge (Partab Bridge), with a longer instrumental record (47 years), we develop reconstructions using both Bayesian Regression (BR) and the more conventionally used Principal Components Regression (PCR). The reconstructions produced by PCR and BR at Partab Bridge are nearly identical and yield comparable reconstruction skill statistics, highlighting that the resulting tree-ring reconstruction of streamflow is not dependent on the choice of statistical method. Reconstructions at all four reconstructions indicate flow levels in the 1990s were higher than mean flow for the past six centuries. While streamflow appears most sensitive to accumulated winter (January-March) precipitation and summer (MJJAS) temperature, with warm summers contributing to high flow through increased melt of snow and glaciers, shifts in winter precipitation and summer temperatures cannot explain the anomalously high flow during the 1990s. Regardless, the sensitivity of streamflow to summer temperatures suggests that projected warming may increase streamflow in coming decades, though long-term water risk will additionally depend on changes in snowfall and glacial mass balance.

Detection of continental-scale intensification of hourly rainfall extremes

Temperature scaling studies suggest that hourly rainfall magnitudes might increase beyond thermodynamic expectations with global warming1–3; that is, above the Clausius–Clapeyron (CC) rate of ~6.5% °C−1. However, there is limited evidence of such increases in long-term observations. Here, we calculate continental-average changes in the magnitude and frequency of extreme hourly and daily rainfall observations from Australia over the years 1990–2013 and 1966–1989. Observed changes are compared with the uncertainty from natural variability and expected changes from CC scaling as a result of global mean surface temperature change. We show that increases in daily rainfall extremes are consistent with CC scaling, but are within the range of natural variability. In contrast, changes in the magnitude of hourly rainfall extremes are close to or exceed double the expected CC scaling, and are above the range of natural variability, exceeding CC × 3 in the tropical region (north of 23° S). These continental-scale changes in extreme rainfall are not explained by changes in the El Nino–Southern Oscillation or changes in the seasonality of extremes. Our results indicate that CC scaling on temperature provides a severe underestimate of observed changes in hourly rainfall extremes in Australia, with implications for assessing the impacts of extreme rainfall. Theory predicts that hourly rainfall extremes may increase with anthropogenic warming. Observations from Australia suggest changes two to three times above the Clausius–Clapeyron rate, above that expected from natural variability.

Antarctic and global climate history viewed from ice cores.

A growing network of ice cores reveals the past 800,000 years of Antarctic climate and atmospheric composition. The data show tight links among greenhouse gases, aerosols and global climate on many timescales, demonstrate connections between Antarctica and distant locations, and reveal the extraordinary differences between the composition of our present atmosphere and its natural range of variability as revealed in the ice core record. Further coring in extremely challenging locations is now being planned, with the goal of finding older ice and resolving the mechanisms underlying the shift of glacial cycles from 40,000-year to 100,000-year cycles about a million years ago, one of the great mysteries of climate science.

Incubation temperature impacts nestling growth and survival in an open-cup nesting passerine.

For oviparous species such as birds, conditions experienced while in the egg can have long‐lasting effects on the individual. The impact of subtle changes in incubation temperature on nestling development, however, remains poorly understood, especially for open‐cup nesting species with altricial young. To investigate how incubation temperature affects nestling development and survival in such species, we artificially incubated American robin (Turdus migratorius) eggs at 36.1°C (“Low” treatment) and 37.8°C (“High” treatment). Chicks were fostered to same‐age nests upon hatching, and we measured mass, tarsus, and wing length of experimental nestlings and one randomly selected, naturally incubated (“Natural”), foster nest‐mate on days 7 and 10 posthatch. We found significant effects of incubation temperature on incubation duration, growth, and survival, in which experimentally incubated nestlings had shorter incubation periods (10.22, 11.50, and 11.95 days for High, Low, and Natural eggs, respectively), and nestlings from the Low treatment were smaller and had reduced survival compared to High and Natural nestlings. These results highlight the importance of incubation conditions during embryonic development for incubation duration, somatic development, and survival. Moreover, these findings indicate that differences in incubation temperature within the natural range of variation can have important carryover effects on growth and survival in species with altricial young.

Hydrometeorological conditions preceding wildfire, and the subsequent burning of a fen watershed in Fort McMurray, Alberta, Canada

Abstract. The destructive nature of the ∼ 590 000 ha Horse river wildfire in the Western Boreal Plain (WBP), northern Alberta, in May of 2016 motivated the investigation of the hydrometeorological conditions that preceded the fire. Historical climate and field hydrometeorological data from a moderate-rich fen watershed were used to (a) identify whether the spring 2016 conditions were outside the range of natural variability for WBP climate cycles, (b) explain the observed patterns in burn severity across the watershed, and (c) identify whether fall and winter moisture signals observed in peatlands and lowland forests in the region are indicative of wildfire. Field hydrometeorological data from the fen watershed confirmed the presence of cumulative moisture deficits prior to the fire. Hydrogeological investigations highlighted the susceptibility of fen and upland areas to water table and soil moisture decline over rain-free periods (including winter), due to the watershed's reliance on supply from localized flow systems originating in topographic highs. Subtle changes in topographic position led to large changes in groundwater connectivity, leading to greater organic soil consumption by fire in wetland margins and at high elevations. The 2016 spring moisture conditions measured prior to the ignition of the fen watershed were not illustrated well by the Drought Code (DC) when standard overwintering procedures were applied. However, close agreement was found when default assumptions were replaced with measured duff soil moisture recharge and incorporated into the overwintering DC procedure. We conclude that accumulated moisture deficits dating back to the summer of 2015 led to the dry conditions that preceded the fire. The infrequent coinciding of several hydrometeorological conditions, including low autumn soil moisture, a modest snowpack, lack of spring precipitation, and high spring air temperatures and winds, ultimately led to the Horse river wildfire spreading widely and causing the observed burn patterns. Monitoring soil moisture at different land classes and watersheds would aid management strategies in the production of more accurate overwintered DC calculations, providing fire management agencies early warning signals ahead of severe spring wildfire seasons.

Chronological study to estimate the range of natural variations in size and proportion of letters in handwriting

The exigency of computational approaches in detection of authenticity of handwriting is currently one of the imperative objective in forensic investigation. The most common pending errors made during investigation process are the utilisation of only known conventional methods of examination. The study was conducted with the objective of determining the range of natural variation in handwriting considering a period crevice of every two years. The instability of the factor, “Size and Proportion” of letters served as an indicator. Samples were collected at time intervals of two years irrespective of age from 20 individuals. “Autodesk Computer Aided Drafting” software was used to set the range of natural variations. The unique detectable range of natural variation after two years, then four years and finally after 6 years in genuine writing was found. The technique helps in solving the cases aiing in contemporary writings and could be served as a non-destructive method of examination.

Expanding Our Understanding of Forest Structural Restoration Needs in the Pacific Northwest

Ecological departure, or how much landscapes have changed from a natural range of variation (NRV), has become a key metric in forest planning and restoration efforts. In this study we define forest restoration need as the specific change in structural stage abundance necessary to move landscapes into the NRV. While most restoration projects in the forested ecosystems of the Pacific Northwest, USA (Oregon and Washington) have embraced this paradigm, our understanding of what treatments to apply where, when, and at what magnitude is evolving and continues to be refined. We build on a body of existing LANDFIRE/Fire Regime Condition Class (FRCC) work on ecological departure to assess the ecological departure of all forested landscapes in the region. Moreover, we assess departure in moister forests west of the Cascade crest, and compare them with fire-dependent forests east of the crest and in southwest Oregon. These “moister Westside” forests have received relatively less attention in a fire ecology context, and we hypothesize restoration needs there are quite different. We show a substantial need for disturbance-related treatments in the drier fire-dependent portion of this region (east of the Cascade crest plus southwest Oregon), with over half of this treatment type falling on Federally-administered land. On the Westside the need for succession is more pronounced. The lack of pronounced disturbance need west of the Cascade crest suggests restoration there may require strategies more nuanced than in the fire-dependent zone.

Meristic and morphometric characters of Leptopelis natalensis tadpoles (Amphibia: Anura: Arthroleptidae) from Entumeni Forest reveal variation and inconsistencies with previous descriptions

The tadpole of Leptopelis natalensis is described based on a series of 32 specimens from Entumeni Forest, KwaZulu-Natal, South Africa. Previous descriptions are brief, lack morphometric data, or are based on specimens of imprecise origin. The tadpole resembles other Leptopelis tadpoles and is generally in agreement with existing accounts, although some differences exist. Some of these differences seem to fall within the range of natural variation. Others, such as the presence of a fifth anterior row of keratodonts, might be indicative of variation at the population level and should be considered in future taxonomic revisions. Leptopelis natalensis tadpoles seem to be most readily distinguished by their more narrowly keratinized beaks from the geographically overlapping or adjacent L. mossambicus and L. xenodactylus .

Los fenómenos pluviométricos extremos en el escenario de cambio climático antropogénico en Galicia. Gestión de la incertidumbre

Los riesgos vinculados al cambio climático derivados de episodios extremos, como olas de calor o eventos de precipitación extrema ya son considerados en los informes del PCC como moderados (nivel de confianza alto) y altos, en caso de producirse un calentamiento adicional de 1ºC. La abundancia y regularidad de las precipitaciones caracterizan la realidad climática gallega, aunque en el rango de variabilidad natural de este meteoro, se registran episodios excepcionales, bien por su baja frecuencia de aparición, bien por el volumen de agua precipitada. Las proyecciones regionales de los modelos predictivos apuntan a un posible incremento de fenómenos extremos de precipitación y de una mayor irregularidad de los aportes. Aunque, dada la propia naturaleza de este meteoro, estas proyecciones se mueven todavía en un grado de confianza bajo. En el presente trabajo, además de hacer balance de situación de estos posibles escenarios de cambio y las consecuencias que se deriven de él, también se reflexiona sobre la urgente necesidad de modificar las políticas medioambientales tanto a escala gallega como global.

Monthly paleostreamflow reconstruction from annual tree-ring chronologies

Paleoclimate reconstructions are increasingly used to characterize annual climate variability prior to the instrumental record, to improve estimates of climate extremes, and to provide a baseline for climate-change projections. To date, paleoclimate records have seen limited engineering use to estimate hydrologic risks because water systems models and managers usually require streamflow input at the monthly scale. This study explores the hypothesis that monthly streamflows can be adequately modeled by statistically decomposing annual flow reconstructions. To test this hypothesis, a multiple linear regression model for monthly streamflow reconstruction is presented that expands the set of predictors to include annual streamflow reconstructions, reconstructions of global circulation, and potential differences among regional tree-ring chronologies related to tree species and geographic location. This approach is used to reconstruct 600 years of monthly streamflows at two sites on the Bear and Logan rivers in northern Utah. Nash-Sutcliffe Efficiencies remain above zero (0.26–0.60) for all months except April and Pearson’s correlation coefficients (R) are 0.94 and 0.88 for the Bear and Logan rivers, respectively, confirming that the model can adequately reproduce monthly flows during the reference period (10/1942 to 9/2015). Incorporating a flexible transition between the previous and concurrent annual reconstructed flows was the most important factor for model skill. Expanding the model to include global climate indices and regional tree-ring chronologies produced smaller, but still significant improvements in model fit. The model presented here is the only approach currently available to reconstruct monthly streamflows directly from tree-ring chronologies and climate reconstructions, rather than using resampling of the observed record. With reasonable estimates of monthly flow that extend back in time many centuries, water managers can challenge systems models with a larger range of natural variability in drought and pluvial events and better evaluate extreme events with recurrence intervals longer than the observed record. Establishing this natural baseline is critical when estimating future hydrologic risks under conditions of a non-stationary climate.

Modelling the effects of inter-observer variation on colour rendition

The colour rendition characteristics of light sources are quantified with measures based on CIE standard observers, which are reasonable representations of population averages. However, even among people with normal colour vision, the natural range of variation in colour sensitivity means any individual may see something different than the standard observer. Modelling results quantify the effects of these inter-observer differences on colour rendition measures defined by IES TM-30-15. In general, inter-observer differences tend to be smaller for light sources with high colour fidelity values, and they are affected by spectral characteristics of different lighting technologies. The magnitude of variation in colour rendition measures, up to 5–10 units in IES TM-30-15 ( Rf, Rg), measures is compared with other sources of variability and ambiguity.

Terrestrial Condition Assessment for National Forests of the USDA Forest Service in the Continental US

The terrestrial condition assessment (TCA) evaluates effects of uncharacteristic stressors and disturbance agents on land-type associations (LTAs) to identify restoration opportunities on national forest system (NFS) lands in the United States. A team of agency scientists and managers, representing a broad array of natural resource disciplines, developed a logic structure for the TCA to identify appropriate data sources to support analyses. Primary national data sources included observed insect- and pathogen-induced mortality, key critical loads for soil and the atmosphere, long term seasonal departures in temperature and precipitation, road densities, uncharacteristic wildfires, historical fire regime departure, wildfire potential, insect and pathogen risk, and vegetation departure from natural range of variability. The TCA was implemented with the ecosystem management decision support (EMDS) system, a spatial decision support system for landscape analysis and planning. EMDS uses logic models to interpret data, synthesizes information over successive layers of logic topics, and draws inferences about the ecological integrity of LTAs as an initial step to identifying high priority LTAs for landscape restoration on NFS lands. Results from the analysis showed that about 74 percent of NFS lands had moderate or better overall ecological integrity. Major impacts to ecological integrity included risk of mortality due to insects and disease, extent of current mortality, extent of areas with high and very high wildfire hazard potential, uncharacteristically severe wildfire, and elevated temperatures. In the discussion, we consider implications for agency performance reporting on restoration activities, and subsequent possible steps, including strategic and tactical planning for restoration. The objective of the paper is to describe the TCA framework with results from a national scale application on NFS lands.

History of Tree Growth Declines Recorded in Old Trees at Two Sacred Sites in Northern China.

Old forests are an important component in sacred sites, yet they are at risk of growth decline from ongoing global warming and increased human activities. Growth decline, characterized by chronic loss of tree vigor, is not a recent phenomenon. Knowledge of past occurrence of declines is useful for preparing conservation plans because it helps understand if present day forests are outside the natural range of variation in tree health. We report a dendroecological study of growth decline events in the past two centuries at two sacred sites, Hengshan and Wutaishan, in Shanxi province of northern China. Tree rings collected at both sites show distinct periods of declining growth evident as narrow rings. These occurred in the 1830s in both sites, in the 1920s in Wutaishan and in the 2000s in Hengshan. By comparing the pattern of grow declines at the two sites, we hypothesize that resistance of tree growth to external disturbances is forest size dependent, and increased human activity might be a factor additional to climatic droughts in causing the recent strong growth decline at Hengshan Park. Despite these past declines, the forests at both sites have high resilience to disturbances as evidenced by the ability of trees to recover their growth rates to levels comparable to the pre-decline period. Managers should consider reducing fragmentation and restoring natural habitat of old forests, especially in areas on dry sites.

Using Paleoecology to Inform Land Management as Climates Change: An Example from an Oak Savanna Ecosystem.

Oak savanna, a transitional ecosystem between open prairie and dense oak forest, was once widespread in Minnesota. Upon European settlement much of the oak savanna was destroyed. Recently, efforts to restore this ecosystem have increased and often include the reintroduction of fire. Though fire is known to serve an important role within oak savannas, there are currently few studies which address fire regimes on timescales longer than the last century. This research presents a paleoecological history of Sherburne National Wildlife Refuge (SNWR) in MN, USA, spanning the last ~8000 years. The objectives of this study were to use charcoal, pollen, and magnetic susceptibility of lake sediments collected from Johnson Slough (JS) within the refuge to evaluate the natural range of variability and disturbance history of the oak savanna within the refuge, assess the success of current restoration strategies, and add to the regional paleoecological history. The mid/late Holocene period of the JS record shows a period of high fire activity from ca. 6500 to 2600 cal year BP, with a shift from prairie to oak savanna occurring over this same period. A (possibly agricultural) disturbance to JS sediments affected the period from ca. 2600 cal year BP to 1963 AD, which includes the time of Euro-American settlement. However, the destruction and subsequent restoration of the oak savanna is evident in a pollen ratio of Quercus:Poaceae, indicating that current restoration efforts have been successful at restoring the oak savanna to within the natural range of variability seen just prior to destruction.

Natural variability of biochemical biomarkers in the macro-zoobenthos: Dependence on life stage and environmental factors.

Biomarkers are widely used in ecotoxicology as indicators of exposure to toxicants. However, their ability to provide ecologically relevant information remains controversial. One of the major problems is understanding whether the measured responses are determined by stress factors or lie within the natural variability range. In a previous work, the natural variability of enzymatic levels in invertebrates sampled in pristine rivers was proven to be relevant across both space and time. In the present study, the experimental design was improved by considering different life stages of the selected taxa and by measuring more environmental parameters. The experimental design considered sampling sites in 2 different rivers, 8 sampling dates covering the whole seasonal cycle, 4 species from 3 different taxonomic groups (Plecoptera, Perla grandis; Ephemeroptera, Baetis alpinus and Epeorus alpicula; Tricoptera, Hydropsyche pellucidula), different life stages for each species, and 4 enzymes (acetylcholinesterase, glutathione S‐transferase, alkaline phosphatase, and catalase). Biomarker levels were related to environmental (physicochemical) parameters to verify any kind of dependence. Data were statistically elaborated using hierarchical multilevel Bayesian models. Natural variability was found to be relevant across both space and time. The results of the present study proved that care should be paid when interpreting biomarker results. Further research is needed to better understand the dependence of the natural variability on environmental parameters. Environ Toxicol Chem 2017;36:3158–3167. © 2017 SETAC

Boreal bryophyte response to natural fire edge creation

AbstractQuestionChanges in species richness and composition in plant communities as a result of edge creation are well documented in anthropogenically modified landscapes, but what happens after natural disturbance? We investigate the responses of boreal bryophytes to edge creation in a post‐wildfire residual forest patch system.LocationBoreal black spruce–feather moss forest, western Québec, Canada.MethodsBryophyte community was sampled in 50‐m2 plots: 117 plots in 39 undisturbed forest cores (control) and 108 plots in 30 residual forest patches from wildfire, divided into 48 core plots, 30 north‐facing edge plots and 30 south‐facing edge plots. Temporal, severity, spatial and structural characteristics of the stands were also recorded to explain bryophyte community composition.ResultsResidual edges and cores were more species‐rich than undisturbed cores, particularly north‐facing edges, but community composition differed between undisturbed and residual cores. Indicator species of undisturbed cores and residual edges differed in their species traits. Spatial variables explained variations in composition, with a larger difference between core and edge communities in patches over 3 ha compared to smaller patches.ConclusionWe observed community composition change in response to natural edge creation. While edge influence is reduced in large patches, the bryophyte community remains distinct from undisturbed cores. This community change is a ‘control’ in studies of boreal bryophyte response to anthropogenic edge creation, and suggests that we should consider the natural range of variability. Finally, this study emphasizes that forest remnants do not substitute for continuous and undisturbed forests.