Thomas T Veblen

University of Colorado Boulder | CUB · Department of Geography

Over the past several decades, forests worldwide have experienced increases in biotic disturbances caused by insects and plant pathogens-a trend that is expected to continue with climate warming. Whereas the causes and effects of individual biotic disturbances are well studied, spatiotemporal interactions among multiple biotic disturbances are less...

Aim Our understanding of the mechanisms that maintain forest diversity under changing climate can benefit from knowledge about traits that are closely linked to fitness. We tested whether the link between traits and seed number and seed size is consistent with two hypotheses, termed the leaf economics spectrum and the plant size syndrome, or whethe...

Masting describes the spatiotemporal variability in seed production by a population of plants. Both abiotic and biotic factors drive masting, but the importance of these factors can vary among individuals and populations. To better understand how a changing climate, altered disturbance regimes, or novel management strategies might affect future see...

Presentation on the role of historical range of variability in decision making for climate adaptation in the Colorado Front Range

Presentation on forest ecology and adapting to climate change in the Colorado Front Range

Amplified by warming temperatures and drought, recent outbreaks of native bark beetles (Curculionidae: Scolytinae) have caused extensive tree mortality throughout Europe and North America. Despite their ubiquitous nature and important effects on ecosystems, forest recovery following such disturbances is poorly understood, particularly across region...

Recent increases in area burned, combined with poor natural regeneration in some areas, have promoted concerns about widespread forest losses throughout the western U.S. Postfire reforestation is one strategy commonly employed by land managers and land owners to facilitate forest recovery, but the area in need of planting only becomes larger each y...

Climate change is forcing shifts in wildfire regimes, altering post-fire processes, and threatening the persistence of species and ecosystems. Key to assessing the potential for post-fire conversion to an alternate vegetation type is understanding drivers of burn severity, which in turn influence the material legacies that determine post-fire recov...

Short-interval and high-severity fires combined are emerging as a catalyst of major reorganization of understory plant communities. In temperate forests of south-central Chile, concern exists about the resilience of threatened Araucaria-Nothofagus forests, including its understory community following extensive and severe fires. In this study we use...

Landscape scale forest restoration in Colorado is being driven largely by the belief that a return to forest structures that existed prior to 20th-century fire suppression will simultaneously achieve goals of improved forest health, reduced societal exposure to extreme wildfires, and enhanced forest resilience to climate change. Increasingly, the e...

The relationships that control seed production in trees are fundamental to understanding the evolution of forest species and their capacity to recover from increasing losses to drought, fire, and harvest. A synthesis of fecundity data from 714 species worldwide allowed us to examine hypotheses that are central to quantifying reproduction, a foundat...

Lack of tree fecundity data across climatic gradients precludes the analysis of how seed supply contributes to global variation in forest regeneration and biotic interactions responsible for biodiversity. A global synthesis of raw seedproduction data shows a 250‐fold increase in seed abundance from cold‐dry to warm‐wet climates, driven primarily by...

Significance Suitable habitats for forest trees may be shifting fast with recent climate change. Studies tracking the shift in suitable habitat for forests have been inconclusive, in part because responses in tree fecundity and seedling establishment can diverge. Analysis of both components at a continental scale reveals a poleward migration of nor...

We aimed to disentangle the patterns of synchronous and variable cone production (i.e. masting) and its relationship to climate in two conifer species native to dry forests of western North America. We used cone abscission scars to reconstruct ca 15 years of recent cone production in Pinus edulis and Pinus ponderosa , and used redundancy analysis t...

Despite its importance for forest regeneration, food webs, and human economies, changes in tree fecundity with tree size and age remain largely unknown. The allometric increase with tree diameter assumed in ecological models would substantially overestimate seed contributions from large trees if fecundity eventually declines with size. Current esti...

Recent extreme events of drought and heat have been associated with insect-driven tree mortality. However, there is substantial uncertainty about the impact of climate variability and extreme climatic episodes on insect–host dynamics, especially over species biogeographical ranges. Here, we use climatic suitability indices derived from species dist...

Since the late 1990s, extensive outbreaks of native bark beetles (Curculionidae: Scolytinae) have affected coniferous forests throughout Europe and North America, driving changes in carbon storage, wildlife habitat, nutrient cycling, and water resource provisioning. Remote sensing is a crucial tool for quantifying the effects of these disturbances...

A Correction to this paper has been published: https://doi.org/10.1038/s41467-021-22025-2

Landsat time series (LTS) and associated change detection algorithms are useful for monitoring the effects of global change on Earth’s ecosystems. Because LTS algorithms can be easily applied across broad areas, they are commonly used to map changes in forest structure due to wildfire, insect attack, and other important drivers of tree mortality. B...

Warming temperatures and rising moisture deficits are expected to increase the rates of background tree mortality–low amounts of tree mortality (~0.5%–2% year ⁻¹ ), characterizing the forest demographic processes in the absence of abrupt, coarse‐scale disturbance events (e.g. fire). When compounded over multiple decades and large areas, even minor...

Indirect climate effects on tree fecundity that come through variation in size and growth (climate-condition interactions) are not currently part of models used to predict future forests. Trends in species abundances predicted from meta-analyses and species distribution models will be misleading if they depend on the conditions of individuals. Here...

Understanding how drivers of ecological disturbance operate across scales is important in an era of increasing disturbance activity. Severe and extensive Dendroctonus bark beetle outbreaks across western North America have left in their wake dominance by shade‐tolerant and commonly late‐seral trees such as subalpine fir (Abies lasiocarpa), which ca...

The spatial overlap of multiple ecological disturbances in close succession has the capacity to alter trajectories of ecosystem recovery. Widespread bark beetle outbreaks and wildfire have affected many forests in western North America in the past two decades in areas of important habitat for native ungu-lates. Bark beetle outbreaks prior to fire m...

Significance Forests are experiencing growing risks of drought-induced mortality in a warming world. Yet, ecosystem dynamics following drought mortality remain unknown, representing a major limitation to our understanding of the ecological consequences of climate change. We provide an emerging picture of postdrought ecological trajectories based on...

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...

Questions Increased wildfire activity is resulting in plant community‐type conversions worldwide. In some regions, fire‐sensitive forests are being replaced by flammable fire‐resilient communities, increasing the likelihood of reburning due to positive fire feedbacks. Here we evaluated whether fire severity affects postfire plant community flammabi...

1) Ongoing changes in fire regimes have the potential to drive widespread shifts in Earth’s vegetation. Plant traits and vital rates provide insight into vulnerability to fire-driven vegetation shifts because they can be indicators of the ability of individuals to survive fire (resistance) and populations to persist (resilience) following fire. 2)...

Abstract Understanding potential limitations to tree regeneration is essential as rates of tree mortality increase in response to direct (extreme drought) and indirect (bark beetle outbreaks, wildfire) effects of a warming climate. Seed availability is increasingly recognized as an important limitation for tree regeneration. High variability in see...

Fire is a powerful ecological and evolutionary force that regulates organismal traits, population sizes, species interactions, community composition, carbon and nutrient cycling and ecosystem function. It also presents a rapidly growing societal challenge, due to both increasingly destructive wildfires and fire exclusion in fire‐dependent ecosystem...

Untangling the nuanced relationships between landscape, fire disturbance, human agency, and climate is key to understanding rapid population declines of fire‐sensitive plant species. Using multiple lines of evidence across temporal and spatial scales (vegetation survey, stand structure analysis, dendrochronology, and fire history reconstruction), w...

Bamboos are a diverse and ecologically important group of plants that have the potential to modulate the structure, composition, and function of forests. With the aim of increasing the visibility and representation of bamboo in forest surveys, and to standardize techniques across ecosystems, we present a protocol for bamboo monitoring in permanent...

Understanding how severe disturbances and their interactions affect forests is key to projecting ecological change under a warming climate. Substantial increases in some biotic disturbances, such as bark beetle outbreaks, in temperate forest ecosystems may compromise recovery to a forest vegetation type (i.e., physiognomic recovery or resilience),...

Forested fire refugia (trees that survive fires) are important disturbance legacies that provide seed sources for post-fire regeneration. Conifer regeneration has been limited following some recent western fires, particularly in ponderosa pine (Pinus ponderosa) forests. However, the extent, characteristics, and predictability of ponderosa pine fire...

Burn severity, which can be reliably estimated by validated spectral indices, is a key element for understanding ecosystem dynamics and informing management strategies. However, in North Patagonian forests, where wildfires are a major disturbance agent, studies aimed at the field validation of spectral indices of burn severity are scarce. The aim o...

Climate warming is contributing to increases in wildfire activity throughout the western U.S., leading to potentially long‐lasting shifts in vegetation. The response of forest ecosystems to wildfire is thus a crucial indicator of future vegetation trajectories, and these responses are contingent upon factors such as seed availability, interannual c...

Climate-induced increases in tree mortality are reported for many forests worldwide. Understanding the potential effects on carbon pools requires long-term monitoring of changes in forest biomass. We measured aboveground biomass (AGB) of living trees over a 34-year period (1982–2016) in permanent plots with varying stand ages, species compositions,...

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...

Climate change is increasing fire activity in the western United States, which has the potential to accelerate climate-induced shifts in vegetation communities. Wildfire can catalyze vegetation change by killing adult trees that could otherwise persist in climate conditions no longer suitable for seedling establishment and survival. Recently docume...

Recent shifts in global forest area highlight the importance of understanding the causes and consequences of forest change. To examine the influence of several potential drivers of forest cover change, we used supervised classifications of historical (1938–1940) and contemporary (2015) aerial imagery covering a 2932‐km2 study area in the northern F...

Increasing evidence indicates that forest disturbances are changing in response to global change, yet local variability in disturbance remains high. We quantified this considerable variability and analyzed whether recent disturbance episodes around the globe were consistently driven by climate, and if human influence modulates patterns of forest di...

[This corrects the article DOI: 10.1371/journal.pone.0201195.].

Studies of forest dynamics commonly assume that species composition of the seedling bank reflects the composition of the future forest canopy. However, many forest types exhibit persistent differences in relative dominance of species in the seedling bank versus the forest canopy. Species-specific differences in tree vital rates (e.g. in-growth, mor...

For millennia, wildfires have markedly influenced forests and non-forested landscapes of the western United States (US), and they are increasingly seen as having substantial impacts on society and nature. There is growing concern over what kinds and amounts of fire will achieve desirable outcomes and limit harmful effects on people and nature. More...

In recent decades large fires have affected communities throughout central and southern Chile with great social and ecological consequences. Despite this high fire activity, the controls and drivers and the spatiotemporal pattern of fires are not well understood. To identify the large-scale trends and drivers of recent fire activity across six regi...

Pre-screening of variables for model comparison using importance values for variables included in final GLM and GAM model comparison. Highly correlated variables (Pearson’s correlation coefficient > 0.60) and variables with importance values < 0.05 were not included in model comparison. (DOCX)

Comparison of Random Forests variable importance values for the entire study area and the North and South bioclimatic zone models. Variables ranked according to their Random Forests variable importance values shown as the estimated mean decrease in accuracy (MDA). (DOCX)

Spatial distribution of the probability of fire occurrence based on best GLM. (EPS)

Summary of GAM model comparison for study area and North and South bioclimatic zone model sets. Model AIC, delta AIC between best model and model shown, % deviance explained, model r-squared, degrees of freedom and predictor variables included in each model. All continuous variables were significant at the p < 0.0001 significance level. (DOCX)