Nicholas Povak

• PhD
• PostDoc Position at US Forest Service

Background Record fire years in recent decades have challenged post-fire forest recovery in the western United States and beyond. To improve management responses, it is critical that we understand the conditions under which management can mitigate severe wildfire impacts, and when it cannot. Here, we evaluated the influence of top-down and bottom-u...

Introduction Growing concerns about fire across the western United States, and commensurate emphasis on treating expansive areas over the next 2 decades, have created a need to develop tools for managers to assess management benefits and impacts across spatial scales. We modeled outcomes associated with two common forest management objectives: fire...

Context Consistent with the diversity-stability hypothesis, high wildlife diversity has been associated with increased resilience and stability of ecosystem services and functions. Nevertheless, ecological non-stationarity associated with climate change challenges the concept of stability. Furthermore, ambiguity surrounding appropriate diversity me...

Background Modern land management faces unprecedented uncertainty regarding future climates, novel disturbance regimes, and unanticipated ecological feedbacks. Mitigating this uncertainty requires a cohesive landscape management strategy that utilizes multiple methods to optimize benefits while hedging risks amidst uncertain futures. We used a proc...

With the onset of rapid climate change and the legacy of past forest management and fire suppression policies, the capacity for forested landscapes to maintain core functionality and processes is being challenged. As such, managers are tasked with increasing the pace and scale of management to mitigate negative impacts of future large disturbances...

As disturbances continue to increase in magnitude and severity under climate change, there is an urgency to develop climate-informed management solutions to increase resilience and help sustain the supply of ecosystem services over the long term. Towards this goal, we used climate analog modeling combined with logic-based conditions assessments to...

Introduction Forest landscapes offer resources and ecosystem services that are vital to the social, economic, and cultural well-being of human communities, but managing for these provisions can require socially and ecologically relevant trade-offs. We designed a spatial decision support model to reveal trade-offs and synergies between ecosystem ser...

Aim Managers are increasingly facing an uncertain future given changing climates and ecological trajectories. The interacting effects of climate, natural disturbance, and management actions complicate future projections, and there is a need for approaches that integrate these factors—especially for predicting future vegetation and species richness....

The Tahoe-Central Sierra Initiative (TCSI) Blueprint for Resilience (hereafter TCSI Blueprint) is a set of strategy maps that identify opportunities for forest protection and adaptation across a 978 381-ha (2.4 million-ac) region of the central Sierra Nevada. The TCSI partners, along with scientists and forest managers versed in the concept of resi...

Background Climate is a main driver of fire regimes, but recurrent fires provide stabilizing feedbacks at several spatial scales that can limit fire spread and severity—potentially contributing to a form of self-regulation. Evaluating the strength of these feedbacks in wildland systems is difficult given the spatial and temporal scales of observati...

Here, we present a detailed characterization of REBURN — a geospatial modeling framework designed to simulate reburn dynamics over large areas and long time frames. We interpret fire-vegetation dynamics for a large testbed landscape in eastern Washington State, USA. The landscape is comprised of common temperate forest and nonforest vegetation type...

With the onset of rapid climate change and the legacy of past forest management and fire suppression policies, the capacity for forested landscapes to maintain core functionality and processes is being challenged. As such, managers are tasked with increasing the pace and scale of management to mitigate negative impacts of future large disturbances...

Abstract With climate change and ongoing impacts from human development and resource extraction, US federal land management agencies are acutely concerned with managing for healthy aquatic ecosystems in the Southern Appalachian Mountain (SAM) Region. Here, we describe development of a spatial decision support application to assess the biological an...

Increasing fire severity and warmer, drier postfire conditions are making forests in the western United States (West) vulnerable to ecological transformation. Yet, the relative importance of and interactions between these drivers of forest change remain unresolved, particularly over upcoming decades. Here, we assess how the interactive impacts of c...

Background: Historically, reburn dynamics from cultural and lightning ignitions were central to the historical ecology of fire in the western United States (wUS), whereby past fire effects limited future fire growth and severity. Over millennia, reburns created heterogenous patchworks of vegetation and fuels that provided avenues and impediments to...

Process-based Forest Landscape Models (FLMs) rely on first principles to simulate ecological patterns and processes, making them uniquely powerful for forecasting ecological dynamics under unprecedented climatic and disturbance regimes. Persistent challenges with any ecological forecasting model are calibration (“tuning” the model) and validation (...

Suppl to Furniss et al 2022 Ecol Mod paper, https://doi.org/10.1016/j.ecolmodel.2022.110099

Decision-making resource stewardship models rely on statistical relationships between management actions and ecosystem services provisioning. The operationalization of management actions benefits from models capable to isolate synergic statistical relationships from trade-offs. We showcase two existing watershed planning studies requiring spatiotem...

Active forest management is applied in many parts of the western United States to reduce wildfire severity, mitigate vulnerability to drought and bark beetle mortality, and more recently, to increase snow retention and late-season streamflow. A rapidly warming climate accelerates the need for these restorative treatments, but the treatment priority...

In the western US, wildfires are modifying the structure, composition, and patterns of forested landscapes at rates that far exceed mechanical thinning and prescribed fire treatments. There are conflicting narratives as to whether these wildfires are restoring landscape resilience to future climate and wildfires. To evaluate the landscape-level wor...

Post-fire landscapes are the frontline of forest ecosystem change. As such, they represent opportunities to foster conditions that are better adapted to future climate and wildfires with post-fire management. In western US landscapes, post-fire management has been mostly defined by short-term emergency mitigation measures, salvage harvest to recove...

Invasive species alter hydrologic processes at watershed scales, with impacts to biodiversity and the supporting ecosystem services. This effect is aggravated by climate change. Here, we integrated modelled hydrologic data, remote sensing products, climate data, and linear mixed integer optimization (MIP) to identify stewardship actions across spac...

Direct link until Dec 30, 2021: https://authors.elsevier.com/a/1e7Nw1L%7EGwQxlY We evaluated the effects of postfire management on forest structure in mixed-conifer forests of northeastern Washington, USA. Postfire treatments were harvest-only, harvest combined with planting, planting-only, and postfire prescribed fire. We used aerial light detect...

Author direct link, available until mid-Dec, 2021: https://authors.elsevier.com/a/1d-zm1L%7EGwQxUc We investigated the relative importance of daily fire weather, landscape position, climate, recent forest and fuels management, and fire history to explaining patterns of remotely-sensed burn severity – as measured by the Relativized Burn Ratio – in...

We review science‐based adaptation strategies for western North American (wNA) forests that include restoring active fire regimes and fostering resilient structure and composition of forested landscapes. As part of the review, we address common questions associated with climate adaptation and realignment treatments that run counter to a broad conse...

Implementation of wildfire‐ and climate‐adaptation strategies in seasonally dry forests of western North America is impeded by numerous constraints and uncertainties. After more than a century of resource and land use change, some question the need for proactive management, particularly given novel social, ecological, and climatic conditions. To ad...

The purpose of this initial assessment, part two of the Roadmap to Resilience, is to understand key aspects of current forest and landscape conditions, including fire and beetle/drought risk and biomass-processing capacity, across the TCSI area to establish the need and urgency for restoration based on a scientific foundation. We defined resilience...

Nearshore ecosystems (e.g., mangrove forests, sea grass beds, coral reefs) are some of the most biologically diverse and ecologically productive on Earth, while providing essential goods and services to human communities. Because these ecosystems are subject to threats from both land and sea, their conservation and management requires a ridge to re...

Abstract Following a wildfire, regeneration to forest can take decades to centuries and is no longer assured in many western U.S. environments given escalating wildfire severity and warming trends. After large fire years, managers prioritize where to allocate scarce planting resources, often with limited information on the factors that drive succes...

Large wildfires (>50,000 ha) are becoming increasingly common in semiarid landscapes of the western United States. Although fuel reduction treatments are used to mitigate potential wildfire effects, they can be overwhelmed in wind‐driven wildfire events with extreme fire behavior. We evaluated drivers of fire severity and fuel treatment effectivene...

Context As the frequency of large, severe fires increases, detecting the drivers of spatial fire severity patterns is key to predicting controls provided by weather, fuels, topography, and management. Objectives Identify the biophysical and management drivers of severity patterns and their spatial variability across the 2013 Rim Fire, Sierra Nevad...

In this chapter, we explain how to create and work with the main types of data in R: vectors, matrices, and data frames. In addition, we briefly explain how to create lists and merge them with data frames. At the end of the chapter, we discuss how to deal with missing data and outliers in data sets.

In this chapter we deal with basic and more advanced numerical analysis and with graphical representation of the results. As the input data, we create vectors, matrices, and data frames directly in R (using the procedures described in Chap. 1), but we also import data files already created in Excel. R supports creating input data within the program...

In this chapter, we show how to create maps. The chapter is divided in three parts; it deals with mapping on different scales, and explains how to perform the mapping process when input data are: (1) inserted manually or (2) drawn from an R package.

Two main groups of statistical tests are parametric and nonparametric tests (Good, 2005). Parametric tests assume that the underlying data are normally distributed and nonparametric tests start off with the assumption that the underlying data do not have a normal distribution (Adler, 2012). Assuming that data are normally distributed is usually cor...

A common motivation of ecological research is to identify the main environmental drivers of ecological processes using empirical modeling. By developing statistical relationships between patterns and processes, empirical models serve two main functions: (1) making accurate predictions over space and time, and (2) making inferences regarding how eco...

This textbook covers R data analysis related to environmental science, starting with basic examples and proceeding up to advanced applications of the R programming language. The main objective of the textbook is to serve as a guide for undergraduate students, who have no previous experience with R, but part of the textbook is dedicated to advanced...

The TCSI’s Framework for Promoting Socio-ecological Resilience across Forested Landscapes in the Sierra Nevada (Framework) provides a structure for assessing landscape conditions, setting objectives, designing projects, and measuring progress towards social-ecological resilience. The Framework offers a shared vision for landscape-scale resilience t...

Most wildfires in North America are quickly extinguished during initial attack (IA), the first phase of suppression. While rates of success are high, it is not clear how much IA suppression reduces annual fire risk across landscapes. This study introduces a method of estimating IA effectiveness by pairing burn probability (BP) analysis with contain...

Before the advent of intensive forest management and fire suppression, western North American forests exhibited a naturally occurring resistance and resilience to wildfires and other disturbances. Resilience, which encompasses resistance, reflects the amount of disruption an ecosystem can withstand before its structure or organization qualitatively...

Wildfire ecosystems are thought to be self-regulated through pattern-process interactions between ignition frequency and location, and patterns of burned and recovering vegetation. Yet, recent increases in the frequency of large wildfires call into question the application of self-organization theory to landscape resilience. Topography represents a...

Non-native species invasions, growing human populations, and climate change are central ecological concerns in tropical island communities. The combination of these threats have led to losses of native biota, altered hydrological and ecosystem processes, and reduced ecosystem services. These threats pose complex problems to often underfunded manage...

Following changes in vegetation structure and pattern, along with a changing climate, large wildfire incidence has increased in forests throughout the western U.S. Given this increase there is great interest in whether fuels treatments and previous wildfire can alter fire severity patterns in large wildfires. We assessed the relative influence of p...

Increasingly, objectives for forests with moderate- or mixed-severity fire regimes are to restore successionally diverse landscapes that are resistant and resilient to current and future stressors. Maintaining native species and characteristic processes requires this successional diversity, but methods to achieve it are poorly explained in the lite...

Recent and projected increases in the frequency and severity of large wildfires in the western U.S. makes understanding the factors that strongly affect landscape fire patterns a management priority for optimizing treatment location. We compared the influence of variations in the local environment on burn severity patterns on the large 2013 Rim fir...

Stream-dwelling species in the U.S. southern Appalachian Mountains region are particularly vulnerable to climate change and acidification. The objectives of this study were to quantify the spatial extent of contemporary suitable habitat for acid-and thermally sensitive aquatic species and to forecast future habitat loss resulting from expected temp...

More than a century of forest and fire management of Inland Pacific landscapes has transformed their successional and disturbance dynamics. Regional connectivity of many terrestrial and aquatic habitats is fragmented, flows of some ecological and physical processes have been altered in space and time, and the frequency, size and intensity of many d...

The historical range of variability (HRV) has been a core theme of landscape ecology and natural resource management for at least two decades. Early papers that allude to the applicability of historical ecology to management go back more than five decades. However, application of the concepts to management has not been without caveat and controvers...

Background/Question/Methods We studied whether the biophysical setting or experienced fire history exerted greater control over the physical structure of forests in Yosemite National Park, California, USA. In mountainous regions, topography creates a mosaic of biophysical settings that vary in precipitation, temperature, heat load, and slope posi...

Accurate estimates of soil mineral weathering are required for regional critical load (CL) modeling to identify ecosystems at risk of the deleterious effects from acidification. Within a correlative modeling framework, we used modeled catchment-level base cation weathering (BCw) as the response variable to identify key environmental correlates and...

In many industrialized regions of the world, atmospherically deposited sulfur derived from industrial, nonpoint air pollution sources reduces stream water quality and results in acidic conditions that threaten aquatic resources. Accurate maps of predicted stream water acidity are an essential aid to managers who must identify acid-sensitive streams...

While fire shapes the structure of forests and acts as a keystone process, the details of how fire modifies forest structure have been difficult to evaluate because of the complexity of interactions between fires and forests. We studied this relationship across 69.2 km2 of Yosemite National Park, USA, that was subject to 32 fires ⩾40 ha between 198...

Background/Question/Methods Prior to European settlement and 20th century management, low- to moderate-severity fires frequently occurred across the landscape, maintaining a significant area in old park-like and multi-story forest patches. Old multi-story forest patches, resulting from protracted fire-free intervals, were structurally complex, an...

Hemlock (Tsuga canadensis) plays a unique role in Eastern forests, producing distinctive biogeochemical, habitat, and microclimatic conditions and yet has begun a potentially irreversible decline due to the invasive hemlock woolly adelgid (Adelges tsugae; HWA) that causes foliar damage, crown loss, and mortality of host trees. Understanding the reg...

We present foundational work on the use of niche modeling to predict continuous surfaces of acid neutralizing capacity (ANC) and base cation weathering (BCw) within the southern Appalachian Mountain Region of the United States. Predicted ANC and BCw surfaces are subsequently used to estimate steady-state critical loads (CLs) of atmospheric sulfur d...

First introduced by Holling (1973), the term “resilience” has been used widely in the ecological literature, but it is not always defined and is rarely quantified. Holling suggested that ecological resilience is the amount of disturbance that an ecosystem could withstand without changing self-organized processes and structures. His description sugg...

Mechanical thinning and prescribed burning practices are commonly used to address tree stocking, spacing, composition, and canopy and surface fuel conditions in western US mixed conifer forests. We examined the effects of these fuel treatments alone and combined on snag abundance and spatial pattern across 12 10-ha treatment units in central Washin...

Background/Question/Methods Ecological resilience has been described as the amount of disturbance that an ecosystem could withstand without changing self-organized processes and structures. Wildfires are an important disturbance process in most western US ecosystems and are integral in shaping spatial and temporal vegetation patterns. It is theoriz...

Forest thinning and prescribed fires are practices used by managers to address concerns over ecosystem degradation and severe wildland fire potential in dry forests. There is some debate, however, about treatment effectiveness in meeting management objectives as well as their ecological consequences. The purpose of this study was to assess changes...

Wildfires are an important disturbance in many western US ecosystems and are integral in shaping spatial and temporal vegetation patterns. Ecological resilience has been described as the amount of disturbance that an ecosystem could withstand without changing self-organized processes and structures. Inherent in resilient systems are observable self...

Background/Question/Methods: Mechanisms for resilience must exist for ecosystems to persist across space and time, often in the face of substantial disturbance, climatic, and environmental fluctuation. Furthermore, resilience mechanisms must occur at spatio-temporal scales that can reinforce the patterns, processes, and interactions that operate in...

Intensive silvicultural treatments can sometimes prevent the conversion of an oak (Quercus spp.) forest to a forest composed of mesophytic competitors following harvest, but the required labor is a disincentive for many private landowners. In this study, shelterwood removal, commercial clear-cutting, understory control, and oak underplanting were c...

Forest thinning and prescribed fire practices are widely used, either separately or in combination, to address tree stocking, species composition, and wildland fire concerns in western US mixed conifer forests. We examined the effects of these fuel treatments alone and combined on dwarf mistletoe infection severity immediately after treatment and f...

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