Alan H. Taylor

• Pennsylvania State University

Burned area and proportion of high severity fire have been increasing in the western USA, and reducing wildfire severity with fuel treatments or other means is key for maintaining fire-prone dry forests and avoiding fire-catalyzed forest loss. Despite the unprecedented scope of firefighting operations in recent years, their contribution to patterns...

Predicting the trajectory of geographical events, such as wildfire spread, presents a formidable task due to the dynamic associations among influential biophysical factors. Geo-events like wildfires frequently display short and long-range spatial and temporal correlations. Short-range effects are the direct contact and near-contact spread of the fi...

Contemporary fire regimes in Californian forests are shifting, with fires becoming larger, more frequent, and increasingly severe. As landscapes transition back to active fire regimes, understanding how the physical environment and biological legacies of past disturbance interact with and determine forest development becomes an increasingly importa...

Background Fire occurrence is influenced by interactions between human activity, climate, and fuels that are difficult to disentangle but crucial to understand, given fire’s role in carbon dynamics, deforestation, and habitat maintenance, alteration, or loss. To determine the relative balance of climatic and anthropogenic influences on fire activit...

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 Forest and nonforest ecosystems of the western United States are experiencing major transformations in response to land-use change, climate warming, and their interactive effects with wildland fire. Some ecosystems are transitioning to persistent alternative types, hereafter called “vegetation type conversion” (VTC). VTC is one of the mo...

Background Wildfire smoke may dampen fire severity through effects on weather and the persistence of atmospheric inversions, but empirical work on the link between smoke and fire severity is scarce. Aims To assess the influence of daily smoke characteristics on wildfire severity in complex terrain. Methods A customised smoke detection algorithm b...

Firescapes of the Mid-Atlantic are understudied compared to other ecosystems in the United States, and little is known about the acceptance of prescribed fire as a forest management tool. Yet, this region harbors high levels of wildland-urban interface (WUI), has a close intermingling of land ownerships, and reflects substantial regional heterogene...

Wildfire is an important natural disturbance agent, shaping mixed conifer forest structure throughout the Southwestern United States. Yet, fire exclusion caused by late 19th century livestock grazing followed by human fire suppression has altered forest structure by increasing forest density, basal area, and canopy cover in recent decades. Changes...

Fire regimes in North American forests are diverse and modern fire records are often too short to capture important patterns, trends, feedbacks, and drivers of variability. Tree‐ring fire scars provide valuable perspectives on fire regimes, including centuries‐long records of fire year, season, frequency, severity, and size. Here, we introduce the...

Although the link between climate change and tundra fire activity is well‐studied, we lack an understanding of how fire, vegetation, and topography interact to either amplify or dampen climatic effects on these tundra fires at Pan‐Arctic scale. This study investigated the relative influence of fire history, climate, topography and vegetation on fir...

Wildfire sizes and proportions burned with high severity effects are increasing in seasonally dry forests, especially in the western USA. A critical need in efforts to restore or maintain these forest ecosystems is to determine where fuel build-up caused by fire exclusion reaches thresholds that compromise resilience to fire. Empirical studies iden...

https://www.sciencedirect.com/science/article/pii/S0301479721023173

Fire is a powerful natural disturbance influencing vegetation patterns across landscapes. Recent transitions from mixed-species forests to post-fire shrublands after severe wildfire is an increasingly prevalent phenomenon in pine-oak and conifer forest ecosystems in southwestern North America. However, we know little about how variation in fire sev...

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...

Fire severity patterns are driven by interactions between fire, vegetation, and terrain, and they generate legacy effects that influence future fire severity. A century of fire exclusion and fuel buildup has eroded legacy effects, and contemporary fire severity patterns may diverge from historical patterns. In recent decades, area burned and area b...

Machine learning (ML) interpretability has become increasingly crucial for identifying accurate and relevant structural relationships between spatial events and factors that explain them. Methodologically aspatial ML algorithms with an apparent high predictive power ignore non-stationary domain relationships in spatio-temporal data (e.g. dependence...

Changes in fire regimes can alter patterns of species dominance and forest carbon stocks by amplifying or diminishing fire vegetation feedbacks. The combined influence of 19th century forest harvesting followed by 20th century fire exclusion has caused a shift in species composition in fire adapted mixed oak forests toward fire sensitive shade tole...

Context Spatial patterns of vegetation change and fire severity are influenced by fire exclusion, topography and weather conditions during a fire. Since the late nineteenth century, fire exclusion has increased vegetation cover which could influence fire severity and post-fire vegetation composition. Objectives We use field measurements and remote...

Legacy effects from one disturbance may influence successional pathways by amplifying or buffering forest regeneration after the next disturbance. We assessed vegetation and tree regeneration in non-serotinous Sierra lodgepole pine (Pinus contorta var. murrayana) stands after a 1984 wildfire which burned with variable severity and again after a hig...

Context Spatial patterns of vegetation change and fire severity are influenced by fire exclusion, topography and weather conditions during a fire. Since the late nineteenth century, fire exclusion has increased vegetation cover which could influence fire severity and post-fire vegetation composition. Objectives We use field measurements and remote...

Fuels treatments and fire suppression operations during a fire are the two management influences on wildfire severity, yet their influence is rarely quantified in landscape-scale analyses. We leveraged a combination of datasets including custom canopy fuel layers and post-fire field data to analyse drivers of fire severity in a large wildfire in th...

Background Prescribed fire in Eastern deciduous forests has been understudied relative to other regions in the United States. In Pennsylvania, USA, prescribed fire use has increased more than five-fold since 2009, yet forest response has not been extensively studied. Due to variations in forest composition and the feedback between vegetation and fi...

Context Increases in tree cover at dry forest margins are a global phenomenon. Yet, how pre-existing tree cover interacts with terrain and water balance to influence tree cover change is not well-understood, nor whether subsequent disturbances restore prior tree cover patterns or create novel patterns. Objectives To assess how terrain, water balan...

Increasing water‐use efficiency (WUE), the ratio of carbon gain to water loss, is a key mechanism that enhances carbon uptake by terrestrial vegetation under rising atmospheric CO2 (ca). Existing theory and empirical evidence suggest a proportional WUE increase in response to rising ca as plants maintain a relatively constant ratio between the leaf...

ContextSpatial patterns of fire severity are influenced by fire-vegetation patch dynamics and topography. Since the late nineteenth century, fire exclusion has increased fuels and recent fire severity patterns may diverge from historical patterns.Objectives We used data from a 2008 wildfire burning in a landscape with known nineteenth century fire...

Summer temperatures across eastern North America (hereafter East) will soon reach a level consistently above any observation experienced during the instrumental period. Increasing temperatures will have negative impacts on natural (e.g., water, plant and animal communities) and human (e.g., health, infrastructure, economies) systems upon which the...

At semi‐arid forest margins, increasing climatic stress combined with disturbances like wildfire threatens to cause widespread forest loss. However, forest resilience is likely to vary over gradients of topoclimate and vegetation characteristics, and the influences of local climate and tree species on tree regeneration remain key uncertainties in a...

The social barriers and opportunities of prescribed fire management practices in the mid-Atlantic region are unknown. We hypothesized that there are mismatches between community perceptions of prescribed fire operations in the mid-Atlantic U.S. and the realities of its current and potential use in landscape management, but that these mismatches var...

Determining the response of forest growth and productivity to climate variability is crucial for understanding and modeling forest carbon sequestration in mesic temperate forests. Most tree-ring analyses have used monthly climate data. Daily climate data may be more appropriate to use in the determination of tree-ring response to climate because ce...

We examined the response of woody plants to internal forest disturbance during subalpine succession and its underlying driving mechanism by comparing changes in woody plant diversity of Abies-Tsuga forests after the flowering and die-back of arrow bamboo (Bashania faberi). We calculated species diversity indices (a-diversity and β-diversity) for th...

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...

Low-cost VR applications in our understanding are applications that run on inexpensive hardware, such as mobile solutions based on a combination of smartphone and VR viewer, and that can be created with relatively low costs, efforts, and VR expertise involved. We present our approach for creating such low-cost applications of real world places, dev...

Moisture delivery in California is largely regulated by the strength and position of the North Pacific jet stream (NPJ), winter high-altitude winds that influence regional hydroclimate and forest fire during the following warm season. We use climate model simulations and paleoclimate data to reconstruct winter NPJ characteristics back to 1571 CE to...

Knowledge of how tree groups and gaps are formed and maintained in frequent-fire forests is key to managing for heterogeneous and resilient forest conditions. This research quantifies changes in tree group and gap spatial structure and abundance of ponderosa pine (Pinus ponderosa) and California black oak (Quercus kelloggii) with stand development...

The primacy of past human activity in triggering change in earth’s ecosystems remains a contested idea. Treating human-environmental dynamics as a dichotomous phenomenon – turning “on” or “off” at some tipping point in the past – misses the broader, longer-term, and varied role humans play in creating lasting ecological legacies. To investigate the...

Knowledge of historical forest conditions and disturbance regimes improves our understanding of landscape dynamics and provides a frame of reference for evaluating modern patterns, pro- cesses, and their interactions. In the western United States, understanding historical fire regimes is particularly important given ongoing climatic changes and the...

Dendroecology is the science that dates tree rings to their exact calendar year of formation to study processes that influence forest ecology (e.g., Speer 2010 [1], Amoroso et al., 2017 [2]). Reconstruction of past fire regimes is a core application of dendroecology, linking fire history to population dynamics and climate effects on tree growth and...

In fire-prone forests, self-reinforcing fire behavior may generate a mosaic of vegetation types and structures. In forests long subject to fire exclusion, such feedbacks may result in forest loss when surface and canopy fuel accumulations lead to unusually severe fires. We examined drivers of fire severity in one large (>1000 km2) wildfire in the w...

Most atmospheric models, including the Weather Research and Forecasting (WRF) model, use a spherical geographic coordinate system to internally represent input data and perform computations. However, most geographic information system (GIS) input data used by the models are based on a spheroid datum because it better represents the actual geometry...

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Arrow bamboo (Bashania faberi) is one of the major staple-food species for wild giant panda (Ailuropoda melanoleuca). In the spring of 1983, massive flowering and die-off of arrow bamboos occurred in Wolong, Sichuan. The goal of this study is to understand the natural regen- eration process of arrow bamboo, a dominant understory species beneath the...

Numerical atmospheric models can generate simulations at very high spatial and temporal resolutions. Many of such models, including the Weather Research and Forecasting (WRF), assume a spherical geographic coordinate system to represent the data and for their computations. However, most if not all Geographic Information System (GIS) data use a sphe...

Significance Twenty-first–century climate change is projected to increase fire activity in California, but predictions are uncertain because humans can amplify or buffer fire–climate relationships. We combined a tree-ring–based fire history with 20th-century area burned data to show that large fire regime shifts during the past 415 y corresponded w...

Quantifying historical fire regimes provides important information for managing contemporary forests. Historical fire frequency and severity can be estimated using several methods; each method has strengths and weaknesses and presents challenges for interpretation and verification. Recent efforts to quantify the timing of historical high-severity f...

Additional age structure plots with fire history Illustration of the range of age structure and possible stand age values associated with frequent fire regimes (Figure A). Black lines represent fire years and green lines represent tree establishment dates (= sample date–breast height age–correction factor [5 years a-h, 8 years i-l]). Red vertical l...

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...

We examined the suitability of two deciduous arctic shrubs (Salix glauca L. and Betula nana L., hereafter Salix and Betula, respectively) for dendroclimatological analysis at two sites in West Greenland. Chronologies were successfully cross-dated, and the oldest covered the period 1954–2010 (Expressed Population Signal [EPS] > 0.85, 1977–2010). Dis...

The number of large, high-severity fires has increased in the western United States over the past 30 years due to climate change and increasing tree density from fire suppression. Fuel quantity, topography, and weather during a burn control fire severity, and the relative contributions of these controls in mixed-severity fires in mountainous terrai...

Quantifying variability of forested riparian buffer (FRB) vegetation structure with variation in adjacent land use supports an understanding of how anthropogenic disturbance influences the ability of riparian systems to perform ecosystem services. However, quantifying FRB structure over large regions is a challenge and requires efficient data colle...

2014. Ice storms generate spatially heterogeneous damage patterns at the watershed scale in forested landscapes. Ecosphere 5(11): Abstract. The effects of large-scale disturbances play a pivotal role in shaping ecosystem structure and function. Interactions between disturbances and a multitude of biophysical factors at different scales generate spa...

The diverse forest types of the southwestern US are inseparable from fire. Across climate zones in California, Nevada, Arizona, and New Mexico, fire suppression has left many forest types out of sync with their historic fire regimes. As a result, high fuel loads place them at risk of severe fire, particularly as fire activity increases due to clima...

We investigated relationships between tree-ring δ13C and growth, and flux tower estimates of gross primary productivity (GPP) at Harvard Forest from 1992 to 2010. Seasonal variations of derived photosynthetic isotope discrimination (Δ13C) and leaf intercellular CO2 concentration (ci ) showed significant increasing trends for the dominant deciduous...

Forest conditions prior to extensive land clearing are often used as a point-of-reference by ecologists and resource managers for characterizing the historical range of variability in forest conditions shaped by intact disturbance regimes. Quantitative data on forest reference conditions can be developed from forest surveys and reconstructions usin...

QuestionsWhat were the characteristics of pre-Anglo-American (reference) forests before logging, grazing and fire exclusion, and how have they changed? What were the structural characteristics of canopy and surface fuels and potential fire behaviour in reference forests, and how do they compare to contemporary forests? How might information from re...

Reconstructions of dry western U.S. forests in the late 19th century in Arizona, Colorado, and Oregon based on General Land Office records were used by Williams and Baker (2012; Global Ecology and Biogeography, 21, 1042--1052; hereafter W&B) to infer past fire regimes with substantial moderate and high severity burning. The authors concluded that c...

Ordination (DCA), direct gradient analysis, and stand structural analysis were used to identify compositional and structural patterns in 35 ecotonal red firmountain hemlock stands in Lassen Volcanic National Park, California. Mountain hemlock-dominated sites were high in altitude, mesic, and soils were coarse textured and low in nutrients. Red fir...

Estimates of canopy height (H) and fractional canopy cover (FC) derived from lidar data collected during leaf-on and leaf-off conditions are compared with field measurements from 80 forested riparian buffer plots. The purpose is to determine if existing lidar data flown in leaf-off conditions for applications such as terrain mapping can effectively...

Fire managers often need data that is spatially explicit at a fine scale (30 m) but is also laborious and time consuming to collect. This study integrates Landsat 5 imagery and topographic information with plot and tree based data to model and map four key canopy fuels variables: Canopy Bulk Density (CBD), Canopy Cover (CC), Canopy Base Height (CBH...

Background/Question/Methods Forested riparian buffers (FRB) perform numerous critical ecosystem services. However, globally, FRB spatial configuration and structure have been modified by anthropogenic development resulting in widespread ecological degradation as seen in the Gulf of Mexico and the Chesapeake Bay. Riparian corridors within develope...

Pre Euro-American settlement forest structure and fire regimes for Jeffrey pine-white fir, red fir-western white pine, and lodgepole pine forests were quantified using stumps from trees cut in the 19th century to establish a baseline reference for ecosystem management in the Lake Tahoe Basin. Contemporary forests varied in different ways compared t...

This paper reviews recent research from California on geographic variability in mixed conifer (MC) forest fire regimes. MC forests are typically described as having experienced primarily frequent, low to moderate severity burns prior to fire suppression that created a mosaic of vegetation patches with variable structure. Research throughout Califor...

The goal of this study was to identify the influence of interannual and interdecadal climate variation and changes in land use on fire regimes in fire prone mixed conifer forests in the central Sierra Nevada in Yosemite National Park, California. We quantified fire frequency, fire return interval, fire extent, and season of fire for a 400 year peri...

Anticipating future forest-fire regimes under changing climate requires that scientists and natural resource managers understand the factors that control fire across space and time. Fire scars – proxy records of fires, formed in the growth rings of long-lived trees – provide an annually accurate window into past low-severity fire regimes. In wester...

Forests characterized by mixed-severity fires occupy a broad moisture gradient between lower elevation forests typified by low-severity fires and higher elevation forests in which high-severity, stand replacing fires are the norm. Mixed-severity forest types are poorly documented and little understood but likely occupy significant areas in the west...

The fire history and stand structure (size, age, horizontal pattern) of red fir (Abiesmagnifica A. Murr) forests were studied in two 3.0-ha plots and a larger study area (400 ha) on the Swain Mountain Experimental Forest to identify the fire regime and the effects of fire on stand structure. The fire record in stumps spanned the period 1740–1985. F...

Rocky Mountain lodgepole pine, (Pinus contorta var. latifolia) regenerates quickly after high severity fire because seeds from serotinous cones are released immediately post-fire. Sierra lodgepole pine (P. contorta var. murrayana) forests burn with variable intensity resulting in different levels of severity and because this variety of lodgepole pi...

Characterization of riparian buffers is integral to understanding the landscape scale impacts of disturbance on wildlife and aquatic ecosystems. Riparian buffers may be characterized using in situ plot sampling or via high resolution remote sensing. Field measurements are time-consuming and may not cover a broad range of ecosystem types. Further, s...

Background/Question/Methods Carbon dynamics in forested ecosystems are recognized as an important component of the global carbon cycle and are influenced by tree growth, regeneration and disturbance events. Fire suppression has altered forests through the process of woody encroachment and infilling, however few studies have been able to identify...

Questions: Did fire regimes in old-growth Pinus ponderosa forest change with Euro-American settlement compared to the pre-settlement period? Do tree age structures exhibit a pattern of continuous regeneration or is regeneration episodic and related to fire disturbance or fire-free periods? Are the forests compositionally stable? Do trees have a clu...

Question: How does competition between quaking aspen (Populus tremuloides) and white fir (Abies concolor) affect growth and spatial pattern of each species? Location: The northern Sierra Nevada, California, USA. Methods: In paired plots in mixed aspen- (n=3) or white fir-dominated (n=2) stands, we mapped trees and saplings and recorded DBH, height,...

We examined tree diameter, age structure, and successional trends in 100 montane forest plots to identify the effects of variation in the return interval, severity, and extent of fires on forest structure and dynamics in the southern Cascade Range, California. We classified 100 forest plots into 8 groups based on stand structural characteristics. M...

Fire is recognized as a keystone process in dry mixed-conifer forests that have been altered by decades of fire suppression, Restoration of fire disturbance to these forests is a guiding principle of resource management in the U.S. National Park Service. Policy implementation is often hindered by a poor understanding of forest conditions before fir...

Despite a strong anthropogenic fingerprint on 20th Century wildland fire activity in the American West, climate remains a main driver. A better understanding of the spatio-temporal variability in fire-climate interactions is therefore crucial for fire management. Here, we present annually resolved, tree-ring based fire records for four regions in t...

Fire is an ecologically significant process in the fire-prone ponderosa pine and mixed conifer forests of the northern Sierra Nevada. Fire regimes are influenced by processes that operate over a range of scales that can be grouped broadly as bottom-up (e.g., topography, forest type) or top-down (e.g., climate variation, human land use) controls. To...

Outside of the immediate coastal environments, little is known of fire history in the North Coast Range of California. Fire scar specimens were collected from ponderosa pine (Pinus ponderosa C. Lawson), sugar pine (Pinus lambertiana Douglas), incense cedar (Calocedrus decurrens [Torr] Florin), and Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco)...

We here present a reconstruction (1725–1999) of the winter Pacific North American (PNA) pattern based on three winter climate sensitive tree ring records from the western USA. Positive PNA phases in our record are associated with warm phases of ENSO and PDO and the reorganization of the PNA pattern towards a positive mode is strongest when ENSO and...