Range Of Natural Variability Research Articles

Natural disturbance regimes as templates for the response of bird species assemblages to contemporary forest management

AbstractAimIn managed forest landscapes, the tolerance of species to contemporary alteration of forest cover is often assumed to reflect their resilience to natural disturbances. We tested this central tenet of ecosystem‐based management by comparing the structure of forest bird assemblages among four regions with contrasting historical natural disturbance regimes.LocationCanada's boreal and northern hardwood forests.MethodsUsing point count data from four study regions across Canada, we first determined the relative sensitivity of individual bird species to the contemporary reduction of old forest cover at stand and ‘landscape‐context’ (1‐km radius) scales with log‐linear models. The richness of species most sensitive to loss of old forest (hereafter ‘sensitive species’) was then modelled as a function of landscape‐scale changes in old forest cover. Differences in the rate of decline in the richness of sensitive species with contemporary cover of old forest were compared among regions using ANCOVA. We then compared broken‐stick regression models with linear models to detect thresholds, if present, in this relationship in each region.ResultsBird assemblages from regions with relatively infrequent natural disturbances hosted more species sensitive to contemporary reduction in old forest cover. Those species were also more abundant than in regions with frequent natural disturbances, and the rate of decline in their richness with the loss of old forest was steeper in regions with infrequent natural disturbances than in those where they were frequent. However, we did not detect thresholds in this rate of decline in any study region.Main conclusionsOur findings are consistent with the contention that historical natural disturbance regimes shape the response of biota to contemporary landscape alterations through evolutionary adaptation. We argue that forest management conducted within the natural range of variability in stand and landscape structure specific to a region is likely to be ecologically sustainable.

Intra-male sperm variability: Is there heteromorphism in scorpions (Arachnida, Scorpiones)?

There is a natural range of variation in sperm morphology inside males. This variation may be adaptive or a result of poor quality control of sperm production. Sperm aggregates can also show different morphologies inside ejaculates. Preliminary analyses in scorpions suggest the existence of a sperm package morphological variation. It is unclear if this is a true polymorphism. The main purpose of this analysis is to evaluate polymorphism in sperm packages of scorpions. Some species from the order showed width variation or spatial variation that was associated to the number of folds. Some ejaculates of Bothriurus bonariensis and Brachistosternus ferrugineus males showed width dimorphism, but may be related to the natural variation of sperm width. However, sperm packages in B. ferrugineus showed lower counts of spermatozoa and the apparition of these sperm packages seemed to increase at the beginning of the reproductive season in one of the species. A marked width dimorphism of sperm packages appeared inside ejaculates of Caraboctonus keyserlingi. The adaptive significance of sperm package differences is not well understood. Differences in width may be a consequence of sperm package production errors, resulting in sperm packages with fewer spermatozoa. Sperm package polymorphism in C. keyserlingi may be linked to sperm competition risk and may be associated to other characters and strategies. Alternative hypotheses to the pattern found are further analyzed and discussed within a sexual selection framework.

Role of palaeoecology in describing the ecological character of wetlands

While it is acknowledged that changes in the condition of a wetland can be detected through contemporary monitoring programs, this paper explores the extent to which palaeoecological approaches can be used in concert with contemporary techniques to understand benchmark conditions, rates and direction of change. This is done within the context of the Ramsar Convention on Wetlands that addresses the conservation of internationally important wetlands and the wise use of all wetlands. Over time the Convention has adopted a considerable body of guidance on detecting, reporting and responding to change in ecological character. In recognition that there remain gaps in available guidance on ecological character the Convention has requested further advice on the determination of appropriate reference conditions for assessing change and establishing the range of natural variability of wetlands. As palaeoecological approaches provide a ready means of considering the trajectories of change, and the nature and drivers of change over time, they can assist in qualifying established ecological descriptions. They can also help understand the timing and nature of any departure from normal conditions, and provide early warnings of future change, especially when integrated with contemporary monitoring and modelling.

Human activities and climate variability drive fast-paced change across the world's estuarine-coastal ecosystems.

Time series of environmental measurements are essential for detecting, measuring and understanding changes in the Earth system and its biological communities. Observational series have accumulated over the past 2-5 decades from measurements across the world's estuaries, bays, lagoons, inland seas and shelf waters influenced by runoff. We synthesize information contained in these time series to develop a global view of changes occurring in marine systems influenced by connectivity to land. Our review is organized around four themes: (i) human activities as drivers of change; (ii) variability of the climate system as a driver of change; (iii) successes, disappointments and challenges of managing change at the sea-land interface; and (iv) discoveries made from observations over time. Multidecadal time series reveal that many of the world's estuarine-coastal ecosystems are in a continuing state of change, and the pace of change is faster than we could have imagined a decade ago. Some have been transformed into novel ecosystems with habitats, biogeochemistry and biological communities outside the natural range of variability. Change takes many forms including linear and nonlinear trends, abrupt state changes and oscillations. The challenge of managing change is daunting in the coastal zone where diverse human pressures are concentrated and intersect with different responses to climate variability over land and over ocean basins. The pace of change in estuarine-coastal ecosystems will likely accelerate as the human population and economies continue to grow and as global climate change accelerates. Wise stewardship of the resources upon which we depend is critically dependent upon a continuing flow of information from observations to measure, understand and anticipate future changes along the world's coastlines.

Distribution, bioavailability, and potential risk assessment of the metals in tributary sediments of Three Gorges Reservoir: The impact of water impoundment

To investigate the impact of water impoundment on the metal contamination in sediments cores from the three tributaries of Three Gorges Reservoir (TGR), the concentrations, distribution, bioavailability, and potential risk of eight trace metals between summer and winter were analyzed using sequential analysis. The mean contents of all studied metals were higher than the geochemical background value, and were higher in summer than in winter. The results of the partitioning study indicated that Cr and Ni prevailed in the residual fraction, while a small proportion was found in the easily soluble fractions. Cu and Zn were distributed mainly in the residual and reducible fraction, while Cd and Pb were predominantly associated with non-residual fractions. These observations suggested that the most easily mobilized metals in the study area were Cd and Pb. The mean enrichment factors (EF) of Cu, Zn, Cd and Hg were higher than 1.5, revealing the potential anthropogenic inputs, whilst the EF of other metals remained within the range of natural variability. The positive correlation between non-residual Cu, Zn and Cd and their EF values further indicated that anthropogenic inputs were the potentially major contributor for the enrichment of Cu, Zn and Cd in TGR sediments. The results evaluated by both potential ecological risk index and modified risk assessment code (mRAC) of all sampling sites demonstrated the relatively high potential risk of sediment contamination effect in TGR.

A proteomic analysis of seeds from Bt-transgenic Brassica napus and hybrids with wild B. juncea.

Transgene insertions might have unintended side effects on the transgenic host, both crop and hybrids with wild relatives that harbor transgenes. We employed proteomic approaches to assess protein abundance changes in seeds from Bt-transgenic oilseed rape (Brassica napus) and its hybrids with wild mustard (B. juncea). A total of 24, 15 and 34 protein spots matching to 23, 13 and 31 unique genes were identified that changed at least 1.5 fold (p < 0.05, Student’s t-test) in abundance between transgenic (tBN) and non-transgenic (BN) oilseed rape, between hybrids of B. juncea (BJ) × tBN (BJtBN) and BJ × BN (BJBN) and between BJBN and BJ, respectively. Eight proteins had higher abundance in tBN than in BN. None of these proteins was toxic or nutritionally harmful to human health, which is not surprising since the seeds are not known to produce toxic proteins. Protein spots varying in abundance between BJtBN and BJBN seeds were the same or homologous to those in the respective parents. None of the differentially-accumulated proteins between BJtBN and BJBN were identical to those between tBN and BN. Results indicated that unintended effects resulted from transgene flow fell within the range of natural variability of hybridization and those found in the native host proteomes.

Climate change in the Northeast United States: An analysis of the NARCCAP multimodel simulations

Based on the outputs from multiple regional climate models (RCMs) forced by global climate models (GCMs) in phase II of the North American Regional Climate Change Assessment Program, current simulations and future projections of surface air temperature and precipitation over the Northeast U.S. region are analyzed. We address two questions in this study: How do the combined biases from the GCM-RCM pairs compare to that from their driving GCMs? Are the future responses projected by these GCM-RCM pairs robust and consistent with that predicted by their driving GCMs? The GCM-RCM pair may produce decreased combined biases compared to the inherent biases in the driving GCM, but the possibility of compensating errors suggest that this does not necessarily imply improved representations of current climate. An RCM simulation may also impart biases which exacerbate those from the driving GCM, leading to a large combined error. The substantial underestimates of winter and summer temperature produced by Geophysical Fluid Dynamics Laboratory (GFDL) Experimental Climate Prediction-2 and GFDL Regional Climate Model version 3 are partly attributed to moderate cold biases from their driving GFDL, whereas dynamically downscaling Hadley Centre Climate Model version 3 with Hadley Centre Regional Climate Model leads to mitigated combined biases. The “probability density functions” of temperature and precipitation are estimated for each individual model pair to illustrate the temporal and spatial distributions of these two climate variables. Under the Special Report on Emissions Scenarios A2 emission scenario, the ensemble averaged changes in winter and summer temperature for the mid-21st century (2041–2070) vary between 2.5 to 3.2°C across the subregions. These warming signals are consistent and statistically significant across the model pairs and far exceed the estimated natural variability. The projected future changes in precipitation indicate generally wetter winters and drier summers, but the magnitudes, directions, and spatial distributions of precipitation changes are model-dependent. Moreover, the ensemble average summer precipitation changes (0.6 to −7.9% as estimated by percentage of present-day values) fall within the estimated range of natural variability. Different changes in moisture flux convergence-divergence appear to contribute to the disagreement of the precipitation responses between some GCM-RCM pairs and their driving GCMs. The “reliability ensemble averaging” procedure is also applied and provides a complement to a simpler averaging method to estimate the average and uncertainty range of the simulated climate changes.

Distribution and fractionation of the rare earth elements in Brazilian soils

The distribution and fractionation of Sc, Y and 14 rare earth elements (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) were investigated in 144 samples (topsoil and subsoil) from 88 sites distributed across Brazil. Although, a wide range of natural variability in REE content was observed, overall the REE median contents were relatively low compared with those reported in soils from other parts of the world. The REE contents in Brazilian soils showed significant correlation mainly with Fe, Mn and Ti oxides, as well as organic matter. REE distribution in soils basically depend on the parent material, while fractionation of individual REEs depend on soil characteristics that are partly influenced by pedogenic process. Soils developed from alkaline igneous rocks showed the highest average content of REEs followed by sedimentary rocks, unconsolidated clay sediments, metamorphic rocks, basic igneous rocks, unconsolidated sand and silt sediments, and acid igneous rocks. REE normalized patterns varied significantly within each geological formation, except for soils derived from alkaline igneous rocks. The greatest variations were observed in the light REEs. Graphic inspection using exploratory data analysis tools such as Q–Q normal plots and boxplots was effective to recognize patterns and identify different data groups, determine threshold values and thus define the range of the background REE variability. The data set generated in this study may be used as a preliminary reference for regulatory actions in the Brazilian environmental legislation.

The disturbance regime of Norway spruce forests in Bulgaria

Natural disturbances are among the most important factors that shape forest dynamics and forest landscapes. However, the natural disturbance regime of Norway spruce (Picea abies (L.) Karst.) forests in Europe is not well understood. We studied the disturbance regimes in three forest reserves in Bulgaria (Parangalitsa, Bistrishko branishte, and Beglika), which are representative of the range of conditions typical for P. abies ecosystems in central and southern Europe. Our data indicated that large-scale disturbances were most numerous in forests that were between 120 and 160 years old, those with unimodal diameter at breast height (DBH) distributions, and especially those located in vulnerable topographic settings. Wind disturbances ranged up to 60 ha, followed in one case by a 200 ha Ips typographus (Linnaeus, 1758) outbreak. Older forests and those with more complex structures (i.e., reverse-J DBH) were characterized by numerous small gaps but were also affected by a few larger disturbances. In some old-growth forests at highly productive sites, gaps could be so numerous that the long-term existence of old trees may become an exception. Over the past centuries, the natural range of variability of these Norway spruce forests in Bulgaria appears to have been shaped mostly by wind and bark beetle disturbances of various sizes.

Conflicting Effects of Predator Cue and Ocean Acidification on the MusselMytilus coruscusByssus Production

Understanding the impact of ocean acidification and warming on communities and ecosystems is a researcher priority. This can only be achieved through a combination of experimental and field approaches that would allow developing a mechanistic understanding of impacts across level of biological organizations. Surprisingly, most published studies are still focusing on single species responses with little consideration for interspecific interactions. In this study, the impacts of a 3 days exposure to three parameters (temperature, pH, and presence/absence of the predator cue of the crab Charybdis japonica) and their interactions on an ecologically important endpoint were evaluated: the byssus production of the mussel Mytilus coruscus. Tested temperatures (25°C and 30°C) were within the present range of natural variability whereas pH (8.1, 7.7, and 7.4) covered present as well as near-future natural variability. As expected, the presence of the crab cue induced an antipredator response in Mytilus coruscus (significant 10% increase in byssus secretion rate, 22% increase in frequency of shed byssus, and 30% longer byssus). Decreased pH but not temperature had a significant negative impact on the same endpoints (up to a 17% decrease in byssus secretion rate, 40% decrease in frequency of shed byssus, and 10% shorter byssus at pH 7.3 as compared with pH 8.1) with no significant interactions between the three tested parameters. In this study, it has been hypothesized that pH and predator cue have different modes of action and lead to conflicting functional responses (escape response versus stronger attachment). Functional consequences for ecosystem dynamics still need to be investigated.

Holocene stand-scale vegetation dynamics and fire history of an old-growth spruce forest in southern Finland

Forest vegetation composition, including dominant keystone species and floristic diversity, is driven by natural and anthropogenic disturbances. Disentangling these complex interactions to identify the role of species competition, climate and disturbances in boreal forest dynamics is challenging. Here, pollen and charcoal data are used to reconstruct Holocene vegetation and fire history at the local stand-scale within an old-growth Picea abies (Norway spruce) forest hollow in southern Finland. The aim is to reconstruct vegetation history with specific emphasis on the mid-Holocene expansion of Picea and the decline in deciduous species in relation to fire history. Early-Holocene forest development and vegetation dynamics are primarily driven by climatic variations. The spread of Picea at approximately 5,200 cal bp does not coincide with local natural or anthropogenic disturbance or a decline in deciduous species and is consistent with its regional expansion, suggesting climate as the most likely control over the late establishment of this taxon. The mid-Holocene decline in deciduous species corresponds to an increased fire frequency suggesting a higher anthropogenic disturbance (also considered as the primary reason for the loss of floristic diversity in southern Finland). The ‘natural’ fire frequency in this local stand-scale boreal forest is lower than that observed in the recent past (i.e. the time of significant anthropogenic impact), yet the present-day absence or low frequency of fire remains within the range of natural variability observed during the early- and mid-Holocene.

Holocene variations of wildfire occurrence as a guide for sustainable management of the northeastern Canadian boreal forest

Abstract Background Cumulative impacts of wildfires and forest harvesting can cause shifts from closed-crown forest to open woodland in boreal ecosystems. To lower the probability of occurrence of such catastrophic regime shifts, forest logging must decrease when fire frequency increases, so that the combined disturbance rate does not exceed the Holocene maximum. Knowing how climate warming will affect fire regimes is thus crucial to sustainably manage the forest. This study aimed to provide a guide to determine sustainable forest harvesting levels, by reconstructing the Holocene fire history at the northern limit of commercial forestry in Quebec using charcoal particles preserved in lake sediments. Methods Sediment cores were sampled from four lakes located close to the northern limit of commercial forestry in Quebec. The cores were sliced into consecutive 0.5 cm thick subsamples from which 1 cm3 was extracted to count and measure charcoal particles larger than 150 microns. Age-depth models were obtained for each core based on accelerator mass spectroscopy (AMS) radiocarbon dates. Holocene fire histories were reconstructed by combining charcoal counts and age-depth models to obtain charcoal accumulation rates and, after statistical treatment, long-term trends in fire occurrence (expressed as number of fires per 1000 years). Results Fire occurrence varied between the four studied sites, but fires generally occurred more often during warm and dry periods of the Holocene, especially during the Holocene Thermal Maximum (7000–3500 cal. BP), when fire occurrence was twice as high as at present. Conclusions The current fire regime in the study area is still within the natural range of variability observed over the Holocene. However, climatic conditions comparable to the Holocene Thermal Maximum could be reached within the next few decades, thus substantially reducing the amount of wood available to the forest industry.

New Perspectives on Observed and Simulated Antarctic Sea Ice Extent Trends Using Optimal Fingerprinting Techniques*

Abstract Using optimal fingerprinting techniques, a detection analysis is performed to determine whether observed trends in Southern Ocean sea ice extent since 1979 are outside the expected range of natural variability. Consistent with previous studies, it is found that for the seasons of maximum sea ice cover (i.e., winter and early spring), the observed trends are not outside the range of natural variability and in some West Antarctic sectors they may be partially due to tropical variability. However, when information about the spatial pattern of trends is included in the analysis, the summer and autumn trends fall outside the range of internal variability. The detectable signal is dominated by strong and opposing trends in the Ross Sea and the Amundsen–Bellingshausen Sea regions. In contrast to the observed pattern, an ensemble of 20 CMIP5 coupled climate models shows that a decrease in Ross Sea ice cover would be expected in response to external forcings. The simulated decreases in the Ross, Bellingshausen, and Amundsen Seas for the autumn season are significantly different from unforced internal variability at the 95% confidence level. Unlike earlier work, the authors formally show that the simulated sea ice response to external forcing is different from both the observed trends and simulated internal variability and conclude that in general the CMIP5 models do not adequately represent the forced response of the Antarctic climate system.

Comparative analysis of genetically modified brown rice with conventional rice varieties for the safety assessment

Compositional analysis of genetically modified (GM) rice (OsCK1), non-GM comparator and reference rice as commercial rice was conducted for the safety assessment. The tolerance intervals (TI) of commercial rice were also set to illustrate compositional variability. GM rice, non-GM rice and reference rice were compared using principal component analysis (PCA) and partial least squares-discriminant analysis (PLS-DA) to assess the impact of genetic modification vs. environmental influence on the rice component. Seventeen components in forty-six analysed components were significantly different between GM rice and non-GM rice. But, the mean ranges of the seventeen components were all within those of the reference TIs. These results demonstrate that the nutrition components of GM rice (OsCK1) fell within the range of natural variability and were biologically equivalent to non-GM rice. In addition, multivariate analysis by PCA and PLS-DA revealed that environmental factors such as growing locations were important due to the variability of the rice metabolite profiles. These comparisons lead to the conclusion that disease-resistant transgenic rice (OsCK1) is compositionally equivalent to and as safe and nutritious as conventional rice varieties grown commercially.

How unusual is the 2012–2014 California drought?

AbstractFor the past three years (2012–2014), California has experienced the most severe drought conditions in its last century. But how unusual is this event? Here we use two paleoclimate reconstructions of drought and precipitation for Central and Southern California to place this current event in the context of the last millennium. We demonstrate that while 3 year periods of persistent below‐average soil moisture are not uncommon, the current event is the most severe drought in the last 1200 years, with single year (2014) and accumulated moisture deficits worse than any previous continuous span of dry years. Tree ring chronologies extended through the 2014 growing season reveal that precipitation during the drought has been anomalously low but not outside the range of natural variability. The current California drought is exceptionally severe in the context of at least the last millennium and is driven by reduced though not unprecedented precipitation and record high temperatures.

Evaluating recharge to an ephemeral dryland stream using a hydraulic model and water, chloride and isotope mass balance

Dewatering associated with mining below water table to achieve dry mining conditions may exert significant pressure on water balance in terms of lowering the water table and change in the dynamics of interactions between surface water and groundwater. The discharge of surplus mine water into ephemeral streams may also affect the water balance, by elevating groundwater levels and altering the exchange rate between streams and underlying aquifers. However, it is unclear whether volumes and recharge processes are within the range of natural variability. Here, we present a case study of an ephemeral creek in the semi-arid Hamersley Basin of northwest Australia that has received continuous mine discharge for more than six years. We used a numerical model coupled with repeated measurements of water levels, chloride concentrations and the hydrogen and oxygen stable isotope composition (δ2H and δ18O) to estimate longitudinal evapotranspiration and recharge rates along a 27 km length of Weeli Wolli Creek. We found that chloride increased from 73 to 120 mg/L across this length, while δ18O increased from −8.2‰ to −7.00‰. Groundwater is directly connected to the creek for the first 13 km and recharge rates are negligible. Below this point, the creek flows over a highly permeable aquifer and water loss by recharge increases to a maximum rate of 4.4 mm/d, which accounts for ∼65% of the total water discharged to the creek. Evapotranspiration losses account for the remaining ∼35%. The calculated recharge from continuous flow due to surplus water discharge is similar to that measured for rainfall-driven flood events along the creek. Groundwater under the disconnected section of the creek is characterised by a much lower Cl concentration and more depleted δ18O value than mining discharge water but is similar to flood water generated by large episodic rainfall events. Our results suggest that the impact of recharge from continuous flow on the water balance of the creek has not extended beyond 27 km from the discharge point. Our approach using a combination of hydrochemical and isotope methods coupled with classical surface flow hydraulic modelling allowed evaluation of components of the water budget otherwise not possible in a highly dynamic system that is mainly driven by infrequent but large episodic floods.

A new approach to evaluate forest structure restoration needs across Oregon and Washington, USA

Widespread habitat degradation and uncharacteristic fire, insect, and disease outbreaks in forests across the western United States have led to highly publicized calls to increase the pace and scale of forest restoration. Despite these calls, we frequently lack a comprehensive understanding of forest restoration needs. In this study we demonstrate a new approach for evaluating where, how much, and what types of restoration are needed to move present day landscape scale forest structure towards a Natural Range of Variability (NRV) across eastern Washington, eastern Oregon, and southwestern Oregon. Our approach builds on the conceptual framework of the LANDFIRE and Fire Regime Condition Class programs. Washington–Oregon specific datasets are used to assess the need for changes to current forest structure resulting from disturbance and/or succession at watershed and regional scales.Across our analysis region we found that changes in current structure would be needed on an estimated 4.7million+ ha (40% of all coniferous forests) in order to restore forest structure approximating NRV at the landscape scale. Both the overall level and the type of restoration need varied greatly between forested biophysical settings. Regional restoration needs were dominated by the estimated 3.8+ million ha in need of thinning and/or low severity fire in forests that were historically maintained by frequent low or mixed severity fire (historical Fire Regime Group I and III biophysical settings). However, disturbance alone cannot restore NRV forest structure. We found that time to transition into later development structural classes through successional processes was required on approximately 3.2million ha (over 25% of all coniferous forests). On an estimated 2.3million ha we identified that disturbance followed by succession was required to restore NRV forest structure.The results of this study are intended to facilitate the ability of local land managers to incorporate regional scale, multi-ownership context into local forest management and restoration. Meeting the region-wide restoration needs identified in this study will require a substantial increase in the pace and scale of restoration treatments and coordination amongst governments, agencies, and landowners.

Effectiveness of fuel reduction treatments: Assessing metrics of forest resiliency and wildfire severity after the Wallow Fire, AZ

Landscape-scale wildfire has occurred in higher frequencies across the planet. Fuel reduction treatments to fire-adapted systems have been shown to reduce the impact to human values-at-risk. However, few studies have examined if these treatments contribute to ecosystem resilience, or the capacity of a system to absorb perturbation and return to a similar set of structures or processes. We defined short-term metrics of resiliency to test the hypothesis that fuel reduction treatments in mixed conifer forests increased a fire-adapted system’s resiliency to uncharacteristically severe wildfire. In addition, we tested the hypothesis that fuel reduction treatments reduced burn severity, thereby increasing protection for adjacent human communities. We examined a mixed conifer forested landscape in the southwestern U.S. that was burned by a landscape-scale “mega-fire” in 2011; fuel reduction treatments had been established around communities in the 10years prior to the fire. Fire effects were highly variable in both treated and untreated forests. However, analysis of resiliency metrics showed that: (a) treated units retained a higher proportion of large trees and had post-fire tree densities within the natural range of variability; (b) the understory herbaceous community had significantly higher cover of native grasses in the treated units, but no significant differences in nonnative cover between treated and untreated units; and (c) high-severity patch sizes were significantly larger in untreated stands and covered a larger proportion of the landscape than historical reference conditions. Fire severity, as defined by overstory mortality and basal area loss, was significantly lower in treated units; on average, trees killed per hectare in untreated units was six times the number of trees killed in treated units. Fuel reduction treatments simultaneously reduced fire severity and enhanced short-term metrics of ecosystem resiliency to uncharacteristically severe fire.

Regional Forest Landscape Restoration Priorities: Integrating Historical Conditions and an Uncertain Future in the Northern Rocky Mountains

National law and policy direct the management of the National Forests, with restoring resilient forest conditions being an overarching theme. Climate is a major driver of disturbances that affect ecosystems, especially those with vegetation that show large departures from historical conditions. Drought, fire, insects, and diseases are common forest stressors whose impacts are being exacerbated by climate change. These stressors are threatening the ecosystem services that people value in the forests of the northern Rocky Mountains. The forests of most concern are the dry ponderosa pine and Douglas-fir, moist western white pine mixed with western larch, and cool lodgepole pine mixed with quaking aspen and whitebark pine. Potential reductions in some ecosystem services pose a challenge in terms of not only direct biophysical consequences but also social and economic values that flow from these forests. Values at risk include forest integrity, wildlife habitat, watershed condition, fish habitat, recreation opportunities and investments, community infrastructure, and public safety. This article describes a decision support tool developed by the USDA Forest Service Northern Region in 2010 to support integrated restoration planning. The Northern Region's Integrated Restoration and Protection Strategy (IRPS) is premised on identifying historical conditions through application of the natural range of variability, comparing them with current conditions, and considering a broader range of future issues, including climate change. The IRPS assists managers in the complex task of evaluating factors that influence national forest planning efforts. The assessment and IRPS, by integrating ecological, social, and economic considerations, will help managers of national forests prioritize restoration opportunities using increasingly scarce financial resources. The IRPS will be most beneficial when associated with planning silvicultural practices and fire management directed at restoring the forests of the Northern Region to a more resilient condition.

Ecological site‐based assessments of wind and water erosion: informing accelerated soil erosion management in rangelands.

Accelerated soil erosion occurs when anthropogenic processes modify soil, vegetation, or climatic conditions causing erosion rates at a location to exceed their natural variability. Identifying where and when accelerated erosion occurs is a critical first step toward its effective management. Here we explored how erosion assessments structured in the context of ecological sites (a land classification based on soils, landscape setting, and ecological potential) and their vegetation states (plant assemblages that may change due to management) can inform systems for reducing accelerated soil erosion in rangelands. We evaluated aeolian horizontal sediment flux and fluvial sediment erosion rates for five ecological sites in southern New Mexico, USA, using monitoring data and rangeland-specific wind and water erosion models. Across the ecological sites, plots in shrub-encroached and shrub-dominated vegetation states were consistently susceptible to aeolian sediment flux and fluvial sediment erosion. Both processes were found to be highly variable for grassland and grass–succulent states across the ecological sites at the plot scale (0.25 ha). We identified vegetation thresholds that define cover levels below which rapid (exponential) increases in aeolian sediment flux and fluvial sediment erosion occur across the ecological sites and vegetation states. Aeolian sediment flux and fluvial erosion in the study area could be effectively controlled when bare ground cover was <20% of a site or the cover of canopy interspaces >100 cm in length was less than ∼35%. Land use and management activities that alter cover levels such that they cross thresholds, and/or drive vegetation state changes, may increase the susceptibility of areas to erosion. Land use impacts that are constrained within the range of natural variability should not result in accelerated soil erosion. Evaluating land condition against the erosion thresholds identified here will enable identification of areas susceptible to accelerated soil erosion and the development of practical management solutions.