Thomas E Kolb

Thomas E Kolb
Northern Arizona University | NAU · School of Forestry

PhD, MS Penn State

About

251
Publications
58,661
Reads
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15,346
Citations
Additional affiliations
January 1993 - present
Northern Arizona University
Position
  • Professor (Full)
January 1989 - December 1992
Pennsylvania State University
Position
  • Research Associate
January 1982 - December 1988
Pennsylvania State University
Position
  • Research Assistant

Publications

Publications (251)
Article
We report on survival and growth of ponderosa pines (Pinus ponderosa Douglas ex P. Lawson & C. Lawson) two decades after forest restoration treatments in the G. A. Pearson Natural Area, northern Arizona. Despite protection from harvest that conserved old trees, a dense forest susceptible to uncharacteristically severe disturbance had developed duri...
Article
We investigated growth and a suite of physiological and structural traits of ponderosa pine (Pinus ponderosa Lawson & C. Lawson var. scopulorum Engelm.) seedlings from different provenances using a field common garden study. Twenty-one provenances from a range of elevations across Arizona and New Mexico were planted in 2018 at a field site in the c...
Article
Linking biometric measurements of stand-level biomass growth to tower-based measurements of carbon uptake—gross primary productivity and net ecosystem productivity—has been the focus of numerous ecosystem-level studies aimed to better understand the factors regulating carbon allocation to slow-turnover wood biomass pools. However, few of these stud...
Article
Full-text available
Prolonged drought conditions in semi‐arid forests can lead to widespread vegetation stress and mortality. However, the distribution of these effects is not spatially uniform. We measured soil water potential at high spatial and temporal resolution using 112 sensors distributed across a ponderosa pine forest in northern Arizona, USA during two abnor...
Article
The cover image is based on the Original Article Combined drought and bark beetle attacks deplete non‐structural carbohydrates and promote death of mature pine trees by Nadir Erbilgin et al., https://doi.org/10.1111/pce.14197.
Article
Full-text available
We investigated early survival, growth, and carbon isotope discrimination of ponderosa pine (Pinus ponderosa Lawson & C. Lawson var. scopulorum Engelm.) seedlings from different provenances using common gardens across an elevational gradient in order to examine the potential for adaptation to extreme environments and constraints to artificial regen...
Article
Full-text available
Abstract Juvenile tree survival will play an important role in the persistence of coniferous forests and woodlands in the southwestern United States (SWUS). Vulnerability to climatic and environmental stress declines as trees grow, such that larger, more deeply rooted juveniles are less likely to experience mortality. It is unclear how juvenile con...
Article
How carbohydrate reserves in conifers respond to drought and bark beetle attacks are poorly understood. We investigated changes in carbohydrate reserves and carbon-dependent diterpene defenses in ponderosa pine trees that were experimentally subjected to two levels of drought stress (via root trenching) and two types of biotic challenge treatments...
Article
Full-text available
Drylands occupy ∼40% of the land surface and are thought to dominate global carbon (C) cycle inter-annual variability (IAV). Therefore, it is imperative that global terrestrial biosphere models (TBMs), which form the land component of IPCC earth system models, are able to accurately simulate dryland vegetation and biogeochemical processes. However,...
Article
Full-text available
Despite their sparse vegetation, dryland regions exert a huge influence over global biogeochemical cycles because they cover more than 40% of the world surface (Schimel 2010 Science 327 418-9). It is thought that drylands dominate the inter-annual variability (IAV) and long-term trend in the global carbon (C) cycle (Poulter et al 2014 Nature 509 60...
Preprint
How carbohydrate reserves change in conifers during drought and bark beetle attacks are poorly understood. We investigated changes in carbohydrate reserves and carbon-dependent terpene defenses in ponderosa pine trees experimentally subjected to two levels of drought stress (via root trenching) and two types of biotic challenge treatments (pheromon...
Article
Full-text available
Seedling emergence, survival, morphological and physiological traits, and oxidative stress resistance of southwestern white pine (Pinus strobiformis Engelm.) were studied in response to warming treatments applied during embryogenesis, germination, and early seedling growth. Daytime air temperature surrounding cones in tree canopies was warmed by +2...
Article
Full-text available
Post-fire stand water balance is a critical factor influencing tree regeneration and survival, which are often modulated by fire severity. We examined influences of the post-fire vegetation matrix and fire severity on diurnal, seasonal, and multi-year variation in evapotranspiration (ET) by analyzing the relationship between post-fire vegetation an...
Article
Full-text available
Large datasets of greenhouse gas and energy surface-atmosphere fluxes measured with the eddy-covariance technique (e.g., FLUXNET2015, AmeriFlux BASE) are widely used to benchmark models and remote-sensing products. This study addresses one of the major challenges facing model-data integration: To what spatial extent do flux measurements taken at in...
Article
In the southwestern United States, land managers are implementing large-scale forest restoration projects involving treatments designed to improve forest health, protect ecosystem services, and reduce the risk of catastrophic wildfire in overstocked ponderosa pine (Pinus ponderosa Dougl. ex P. & C. Laws.) forests. A better understanding of wood pro...
Article
Full-text available
Seasonal snow cover in the dry forests of the American West provides essential water resources to both human and natural systems. The structure of trees and their arrangement across the landscape are important drivers of snow cover distribution across these forests, varying widely in both space and time. We used unmanned aerial vehicle (UAV) multis...
Article
Full-text available
A better understanding of carbon use efficiency (CUE) and carbon allocation during disturbance is critical to improve simulations of the global carbon cycle and understanding future climate impacts. Forest thinning of high‐stem density, high elevation dry western US forests is becoming more common to reduce severe fire danger but there are uncertai...
Article
Full-text available
Plant activity in semi-arid ecosystems is largely controlled by pulses of precipitation, making them particularly vulnerable to increased aridity that is expected with climate change. Simple bucket-model hydrology schemes in land surface models (LSMs) have had limited ability in accurately capturing semi-arid water stores and fluxes. Recent, more c...
Article
Full-text available
Ponderosa pine (Pinus ponderosa Lawson & C. Lawson var. scopulorum Engelm.) forests of the southwestern US are threatened by climate change and deforestation. Information about geographic patterns of provenance variation in budburst phenology is needed to make decisions about selecting seed sources for future planting. In this study, provenance var...
Article
Full-text available
High-elevation montane forests are disproportionately important to carbon sequestration in semi-arid climates where low elevations are dry and characterized by low carbon density ecosystems. However, these ecosystems are increasingly threatened by climate change with seasonal implications for photosynthesis and forest growth. As a result, we levera...
Article
Full-text available
Aim Climate warming is increasing fire activity in many of Earth’s forested ecosystems. Because fire is a catalyst for change, investigation of post‐fire vegetation response is critical to understanding the potential for future conversions from forest to non‐forest vegetation types. We characterized the influences of climate and terrain on post‐fir...
Article
Full-text available
Wildland fires have a multitude of ecological effects in forests, woodlands, and savannas across the globe. A major focus of past research has been on tree mortality from fire, as trees provide a vast range of biological services. We assembled a database of individual-tree records from prescribed fires and wildfires in the United States. The Fire a...
Article
Full-text available
Pinus strobiformis (P. strobiformis) faces dual threats of climate change shifting its environmental niche and mortality due to a non-native, invasive fungal pathogen. To inform efforts to sustain this species, we established three field experimental common garden trials along an elevational gradient with drought treatments to assess trait response...
Article
Full-text available
Changes in temperature and moisture as a result of climate forcing can impact performance of planted trees. Tree performance may also be sensitive to new soil conditions, for example, brought about by seeds germinating in soils different from those colonized by ancestral populations. Such “edaphic constraint” may occur with natural migration or hum...
Article
Full-text available
We used a common garden study to investigate genetic variation in spring budburst phenology, growth, and structural traits of ponderosa pine seedlings from 10 Arizona and New Mexico provenances from different elevations. Seedling were grown with ample resources for two growing seasons in a greenhouse in northern Arizona. Budburst date was measured...
Article
A recent severe drought caused widespread mortality of ponderosa pine (Pinus ponderosa) and pinyon pine (Pinus edulis) in forests and woodlands in the southwestern United States. The sustainability of these tree species in the region depends on adequate regeneration and perhaps movement to more climatologically favorable locations. We investigated...
Article
Trees in dry forests often regenerate in episodic pulses when wet periods coincide with ample seed production. Factors leading to success or failure of regeneration pulses are poorly understood. We investigated impacts of stand thinning on survival and growth of the 2013 cohort of ponderosa pine seedlings in northern Arizona. We measured seedling s...
Preprint
Full-text available
Abstract. Plant activity in semi-arid ecosystems is largely controlled by pulses of precipitation, making them particularly vulnerable to increased aridity expected with climate change. Simple bucket-model hydrology schemes in land surface models (LSMs) have had limited ability in accurately capturing semi-arid water stores and fluxes. Recent, more...
Article
Full-text available
Abstract Restoring forest ecosystems has become an increasingly high priority for land managers across the American West. Millions of hectares of forest are in need of drastic yet strategic reductions in density (e.g., basal area). Meeting the restoration and management goals requires quantifying metrics of vertical and horizontal forest structure,...
Article
Full-text available
Interactions between water stress and induced defenses and their role in tree mortality due to bark beetles are poorly understood. We performed a factorial experiment on 48 mature ponderosa pines (Pinus ponderosa) in northern Arizona over three years that manipulated a) tree water stress by cutting roots and removing snow; b) bark beetle attacks by...
Article
Key message Stand basal area of ponderosa pine ( Pinus ponderosa var. scopulorum Engelm.) in the US Southwest has little effect on the density of the wood produced, but climatic fluctuations have a strong effect. Wood density increases during drought, particularly if the drought occurs in late winter/early spring. Future droughts, as are predicted...
Article
Full-text available
Multiple lines of evidence suggest that plant water-use efficiency (WUE)—the ratio of carbon assimilation to water loss—has increased in recent decades. Although rising atmospheric CO2 has been proposed as the principal cause, the underlying physiological mechanisms are still being debated, and implications for the global water cycle remain uncerta...
Article
The mechanisms of plant trait adaptation and acclimation are still poorly understood and, consequently, lack a consistent representation in terrestrial biosphere models (TBMs). Despite the increasing availability of geo‐referenced trait observations, current databases are still insufficient to cover all vegetation types and environmental conditions...
Presentation
water relations study of SWWP seedlings in a common garden
Thesis
Global climate change is having profound and widespread effects on plant growth and survival. For the southwestern United States, warmer temperatures, more variable precipitation and more extreme droughts are expected. As plant populations experience these changes they may adapt and persist in place or may experience increasing environmental stress...
Article
Full-text available
Classical niche partitioning theory posits increased competition for and partitioning of the most limiting resource among coexisting species. Coexisting plant species may vary in rooting depth, reflecting niche partitioning in water source use. Our goal was to assess the soil water partitioning of woody plant communities across northern Arizona alo...
Article
Full-text available
Stomatal response to environmental conditions forms the backbone of all ecosystem and carbon cycle models, but is largely based on empirical relationships. Evolutionary theories of stomatal behaviour are critical for guarding against prediction errors of empirical models under future climates. Longstanding theory holds that stomata maximise fitness...
Poster
Full-text available
This poster describes results of a brief greenhouse experiment designed to understand how the physiology and morphology of 6-month old southwestern white pine (P. strobiformis) seedlings is influenced by controlled drought and warming.
Article
Full-text available
Climate change is expected to lead to increases in drought frequency and severity, with deleterious effects on many ecosystems. Stomatal responses to changing environmental conditions form the backbone of all ecosystem models, but are based on empirical relationships and are not well-tested during drought conditions. Here, we use a dataset of 34 wo...
Data
Supporting information document contains Table A and Figures A-D. (DOCX)
Article
Full-text available
Widespread tree mortality associated with drought has been observed on all forested continents and global change is expected to exacerbate vegetation vulnerability. Forest mortality has implications for future biosphere-atmosphere interactions of carbon, water and energy balance, and is poorly represented in dynamic vegetation models. Reducing unce...
Chapter
Full-text available
Evapotranspiration (ET) is a major component of the water budget in most forests, in many cases exceeding 70% of annual precipitation. Due to limitations in time and resources, input data necessary to model ET are not always available for a study site, but offsite data from meteorological networks may be a suitable substitute. In this study, we eva...
Article
Full-text available
The North American Monsoon delivers warm season precipitation to much of the southwestern United States, yet the importance of this water source for forested ecosystems in the region is not well understood. While it is widely accepted that trees in southwestern forests use winter precipitation for earlywood production, the extent to which summer (m...
Article
Full-text available
Wetland indicator status (WIS) describes the habitat affinity of plant species and is used in wetland delineations and resource inventories. Understanding how species-level functional traits vary across WIS categories may improve designations, elucidate mechanisms of adaptation, and explain habitat optima and niche. We investigated differences in s...
Article
Full-text available
2017. Prototype campaign assessment of disturbance-induced tree loss effects on surface properties for atmospheric modeling. Ecosphere 8(3): Abstract. Changes in large-scale vegetation structure triggered by processes such as deforestation, wild-fires, and tree die-off alter surface structure, energy balance, and associated albedo—all critical for...
Article
Full-text available
Comparisons of community-level functional traits across environmental gradients have potential for identifying links among plant characteristics, adaptations to stress and disturbance, and community assembly. We investigated community-level variation in specific leaf area (SLA), plant mature height, seed mass, stem specific gravity (SSG), relative...
Article
Full-text available
Global-scale studies suggest that dryland ecosystems dominate an increasing trend in the magnitude and interannual variability of the land CO2 sink. However, such analyses are poorly constrained by measured CO2 exchange in drylands. Here we address this observation gap with eddy covariance data from 25 sites in the water-limited Southwest region of...
Article
Full-text available
Widespread tree mortality associated with drought has been observed on all forested continents and global change is expected to exacerbate vegetation vulnerability. Forest mortality has implications for future biosphere–atmosphere interactions of carbon, water and energy balance, and is poorly represented in dynamic vegetation models. Reducing unce...
Article
Full-text available
Understanding the magnitude and pattern of intraspecific variation in tree adaptation to drought is needed to evaluate forest capacity to respond to climate change and for management planning. This understanding is important for species growing at ecotonal sites near the trailing edge of their geographic range where impacts of climate warming are p...
Article
Full-text available
IntroductionUnderstanding the differences in carbon and water vapor fluxes of spatially distributed evergreen needleleaf forests (ENFs) is crucial for accurately estimating regional or global carbon and water budgets and when predicting the responses of ENFs to current and future climate. Methods We compared the fluxes of ten AmeriFlux ENF sites to...