A5034863694- Tree-ring climate responses
- Ecology and Vegetation Dynamics Studies
- Plant Water Relations and Carbon Dynamics
- Forest ecology and management
- Fire effects on ecosystems
- Geology and Paleoclimatology Research
- Cryospheric studies and observations
- Climate change and permafrost
- Species Distribution and Climate Change
- Rangeland and Wildlife Management
- Coastal wetland ecosystem dynamics
- Forest Insect Ecology and Management
- Forest Ecology and Biodiversity Studies
- Forest Management and Policy
- Genetic diversity and population structure
- Remote Sensing in Agriculture
- Remote Sensing and LiDAR Applications
- Animal Ecology and Behavior Studies
- Occupational Health and Safety Research
- Landslides and related hazards
- Botany and Plant Ecology Studies
- Forest Biomass Utilization and Management
- Coastal and Marine Dynamics
- Wildlife Ecology and Conservation
- Botany, Ecology, and Taxonomy Studies
Iscte – Instituto Universitário de Lisboa
2024
Texas A&M University
2012-2022
Mitchell Institute
2013-2020
Umeå University
2011
Mount Allison University
2011
Shell (Netherlands)
2004
University of South Carolina
1996-1998
University of Iowa
1994-1997
Columbia College - South Carolina
1997
Summary Transitions between major vegetation types, such as the tree line, are useful systems for monitoring response of to climate change. Tree lines have, however, shown equivocal responses considered be primarily thermally controlled, although recent work has highlighted importance biotic factors. Dispersal limitation and invasibility tundra matrix have been implicated here we propose herbivory an additional control at some lines. We a conceptual model in which differing relative impacts...
Shrub expansion is a global phenomenon that occurring on savannas, rangelands, and grasslands. In addition, this an increasingly documented occurrence in the Arctic. Numerous recent studies have strived to pinpoint drivers of phenomenon, quantify changes, understand their implications for regional land use, disturbance regimes, nutrient cycling. Inquiry into these topics has been facilitated by technological developments satellite remote sensing, aerial photograph analysis, computer...
Because of the difficulties involved with separating natural fluctuations in climatic variables from possible directional changes related to human activities (e.g., heightened atmospheric CO 2 concentrations fossil fuel consumption), some researchers have focused on developing alternative indicators detect hypothesized climate changes. It has, for example, been suggested that locations ecotones, transitions between adjacent ecosystems or biomes, should be monitored. is assumed climate,...
Recent climate warming and scenarios for further have led to expectations of rapid movement ecological boundaries. Here we focus on the circumarctic forest-tundra ecotone (FTE), which represents an important bioclimatic zone with feedbacks from forest advance corresponding tundra disappearance (up 50% loss predicted this century) driving widespread climatic changes. We address FTE history relations over 20th century, using response data 151 sites across area site-specific data. Specifically,...
Globally, treeline ecotones vary from abrupt lines to extended zones of increasingly small, stunted and/or dispersed trees. These spatial patterns contain information about the processes that control dynamics. Describing these consistently along ecologically meaningful dimensions is needed for generalizing hypotheses and knowledge controlling expected shifts globally. However, existing categorizations treelines are very loosely defined, leading ambiguities in their use interpretation. To...
Shrub expansion is a global phenomenon that gaining increased attention in the Arctic. Recent work employing use of oblique aerial photographs suggested consistent pattern positive change shrub cover across North Slope Alaska. The greatest amounts occurred valley slopes and floodplains. We studied association between topographically derived hydrologic characteristics five areas northern Alaska 1970s 2000s. Change total ranged from − 0.65% to 46.56%. floodplain 3.38% 76.22%. Shrubs are...
Abstract Alpine treelines are expected to advance higher elevations in conjunction with global warming. Nevertheless, the importance of treeline reproductive patterns and seed dispersal within alpine ecotone remains unresolved. In this study, we address two research questions at mountain hemlock on Kenai Peninsula, Alaska: (1) What is primary mode reproduction (2) seeds leading recruitment derived from local populations or they arriving more distant sources? To answer these questions,...
Conifer mountain forests influence a large portion of the World's human population by providing host critical economic, sociological, and ecosystem services. Although causes elevational, transitional boundaries these (i.e. upper lower timberlines) have been questioned for over century, investigations focused predominately on growth limitations saplings or mature trees at alpine boundary. Yet, elevational movement timberlines is dependent initially new seedling establishment in favorable...
Abstract. Growth of coniferous trees at alpine treeline locations has traditionally been viewed as primarily temperature dependent. In this study, we use a physiologically mechanistic process model, ATE‐BGC (Alpine Treeline Ecotone ‐ BioGeochemical Cycles), to study the effects suite environmental variables on carbon balance krummholz growth forms subalpine Abies lasiocarpa under conditions representative in Glacier National Park, Montana, USA. We perform sensitivity analysis determine...
The response of treeline-forming species to global climate change is uncertain. While numerous treeline have recently experienced range advance along their upper elevational boundary, this has been species- and region-dependent. Making an accurate prediction how taxa will respond essential for conservation land management, as likely result in a loss alpine biodiversity through habitat fragmentation. Predicting any requires understanding the current physical climatic determinants its...
Recent increases in deciduous shrub cover are a primary focus of terrestrial Arctic research. This study examined the historic spatial patterns expansion on North Slope Alaska to determine potential for phase transition from tundra shrubland. We variability landscape-scale tall nine sites within river valleys Brooks Range and uplands (BRNS) between 1950s circa 2010 by calculating percent (PCTCOV), patch density (PADENS), size (CVSIZE), mean nearest neighbor distance (MEDIST) multi-scale...
Many hypotheses have been put forward to explain the structure and position of alpine treelines. The spatial complexity ecotone, ranging from sharp boundaries networks tree patches within a heath matrix, may why no consensus has reached. In this paper, we discuss factors abiotic disturbances herbivory that help understand treeline ecotone in Fennoscandia. is dominated by mountain birch (Betula pubescens ssp. tortuosa), show wide range structures. We influence topography, seed limitations,...
The alpine treeline is a potentially sensitive indicator of vegetation response to climate change. However, there not generally accepted single hypothesis that explains position and pattern at multiple scales. Recently set five hypotheses has been proposed for explanations (Körner, 2003b). impacts animals are explicitly included in any these hypotheses, however, they can should be included. In this review we discuss Körner's explain how animal activity within them make more applicable...
Abstract We used LANDIS, a model of forest disturbance and succession, to simulate successional dynamics forests in the southern Appalachian Mountains. The simulated environments are based on Great Smoky Mountains landscapes studied by Whittaker. focused consequences two contrasting regimes—fire exclusion versus frequent burning—for Yellow pine ( Pinus L., subgenus Diploxylon Koehne) oak Quercus L.) that occupy dry mountain slopes ridgetops. These ecosystems conservation priority, declines...
Untangling alternative historic dispersal pathways in long-lived tree species is critical to better understand how temperate may respond climatic change. However, disentangling these often difficult. Emerging genomic technologies and landscape genetics techniques improve our ability assess natural systems. We address the question what degree have microrefugial patches long-distance been responsible for colonization of mountain hemlock (Tsuga mertensiana) on Alaskan Kenai Peninsula.We used...