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29
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October 2008 - September 2017
Publications
Publications (29)
The thermal regime in the sediment column below shallow bodies of water in Arctic permafrost controls benthic habitats and permafrost stability. We present a robust, portable device that measures detailed temperature–depth profiles of the near-surface sediments in less than 1 h. Test campaigns in the Canadian Arctic and on Svalbard have demonstrate...
The thermal regime in the sediment column below shallow water bodies in Arctic permafrost controls benthic habitats and permafrost stability. We present a robust, portable device that measures detailed temperature-depth-profiles of the near-surface sediments in less than 1 hour. Test campaigns in the Canadian Arctic and on Svalbard have demonstrate...
Permafrost thaw in northern ecosystems may cause large quantities of carbon (C) to move from soil to atmospheric pools. Because soil microbial communities play a critical role in regulating C fluxes from soils, we examined microbial activity and greenhouse gas production soon after permafrost thaw and ground collapse (into collapse‐scar bogs), rela...
Boreal forests in permafrost regions make up around one-third of the global forest cover and are an essential component of regional and global climate patterns. Further, climatic change can trigger extensive ecosystem shifts such as the partial disappearance of near-surface permafrost or changes to the vegetation structure and composition. Therefor...
Boreal forests in permafrost regions make up around one-third of the global forest cover and are an essential component of regional and global climate patterns. Further, climatic change can trigger extensive ecosystem shifts such as the partial disappearance of near surface permafrost or changes to the vegetation structure and composition. Therefor...
Climate warming in regions of ice‐rich permafrost can result in widespread thermokarst development, which reconfigures the landscape and damages infrastructure. We present multisite time series observations which couple ground temperature measurements with thermokarst development in a region of very cold permafrost. In the Canadian High Arctic betw...
Permafrost warming has the potential to amplify global climate change, because when frozen sediments thaw it unlocks soil organic carbon. Yet to date, no globally consistent assessment of permafrost temperature change has been compiled. Here we use a global data set of permafrost temperature time series from the Global Terrestrial Network for Perma...
Recent observations of near-surface soil temperatures over the circumpolar Arctic show accelerated warming of permafrost-affected soils. The availability of a comprehensive near-surface permafrost and active layer dataset is critical to better understanding climate impacts and to constraining permafrost thermal conditions and its spatial distributi...
Recent observations of near-surface soil temperatures over the circumpolar Arctic show accelerated warming of permafrost-affected soils. A comprehensive near-surface permafrost temperature dataset is critical to better understand climate impacts and to constrain permafrost thermal conditions and spatial distribution in land system models. We compil...
Permafrost temperatures are increasing in Alaska due to climate change and in
some cases permafrost is thawing and degrading. In areas where degradation
has already occurred the effects can be dramatic, resulting in changing
ecosystems, carbon release, and damage to infrastructure. However, in many areas
we lack baseline data, such as subsurface te...
Permafrost temperatures are increasing in Alaska due to climate change and in some cases permafrost is thawing and degrading. In areas where degradation has already occurred the effects can be dramatic, resulting in changing ecosystems, carbon release, and damage to infrastructure. Yet in many areas we lack baseline data, such as subsurface tempera...
The Global Terrestrial Network for Permafrost (GTN-P) provides the first
dynamic database associated with the Thermal State of Permafrost (TSP) and
the Circumpolar Active Layer Monitoring (CALM) programs, which extensively
collect permafrost temperature and active layer thickness (ALT) data from
Arctic, Antarctic and mountain permafrost regions. Th...
ABSTRACT
The Global Terrestrial Network for Permafrost (GTN-P, gtnp.org) established the new ‘dynamic’ GTN-P Database (gtnpdatabase.org), which targets the Essential Climate Variable (ECV) permafrost, described by the thermal state of permafrost (TSP) and active layer thickness (ALT). This paper outlines the requirements for assessing the GTN-P dat...
The Global Terrestrial Network for Permafrost (GTN-P) provides the first dynamic database associated with the Thermal State of Permafrost (TSP) and the Circumpolar Active Layer Monitoring (CALM) programs, which extensively collect permafrost temperature and active layer thickness data from Arctic, Antarctic and Mountain permafrost regions. The purp...
Quantifying the response of soil respiration to past environmental conditions is critical for predicting how future climate and vegetation change will impact ecosystem carbon balance. Increased shrub dominance in semiarid grasslands has potentially large effects on soil carbon cycling. The goal of this study was to characterize the effect of antece...
Measurements of stable isotopes of atmospheric water vapor can aid in
quantifying spatial and temporal variation in sources of vapor and can
help constrain the modern δ18O fields in global climate models.
Vapor isotope data is sparse for Arctic and sub-Arctic regions. However,
these data - particularly from the ecosystem boundary layer and lower
tr...
Riparian evapotranspiration (ET) is a major component of the surface and subsurface water balance for many semiarid watersheds. Measurement or model-based estimates of ET are often made on a local scale, but spatially distributed estimates are needed to determine ET over catchments. In this paper, we document the ET that was quantified over 3 years...
Recent studies have illuminated the process of hydraulic redistribution, defined as the translocation of soil moisture via plant root systems, but the long-term ecohydrologic significance of this process is poorly understood. We investigated hydraulic redistribution (HR) by Prosopis velutina Woot. (velvet mesquite) in an upland savanna ecosystem ov...
We investigated how the distribution of precipitation over a growing season influences the coupling of carbon and water cycle
components in a semiarid floodplain woodland dominated by the deep-rooted velvet mesquite (Prosopis velutina). Gross ecosystem production (GEP) and ecosystem respiration (R
eco) were frequently uncoupled because of their dif...
Key to evaluating the consequences of woody plant encroachment on water and carbon cycling in semiarid ecosystems is a mechanistic understanding of how biological and non-biological processes influence water loss to the atmosphere. To better understand how precipitation is partitioned into the components of evapotranspiration (bare-soil evaporation...
A number of recent studies have illuminated that plant root systems in dryland ecosystems often facilitate soil moisture redistribution, but the hydrologic significance of this process is poorly understood. In dryland ecosystems this may be an important interaction as water is often the limiting factor in biomass accumulation. We are studying the w...
Precipitation pulses are the primary drivers of carbon cycling in
deserts, and many components, such as soil respiration, may be a
function of plant community composition. Drylands are experiencing
substantial vegetation change, such as the encroachment of woody plants
into historic grasslands, potentially altering soil biogeochemistry
through litt...
Understanding and modeling water exchange in arid and semiarid ecosystems is complicated by the very heterogeneous distribution of vegetation and moisture inputs, and the difficulty of measuring and validating component fluxes at a common scale. We combined eddy covariance (EC), sap flow, and stable isotope techniques to investigate the responses o...
Hydraulic redistribution may have important consequences for ecosystem water balance where plant root systems span large gradients in soil water potential. To assess seasonal patterns of hydraulic redistribution, we measured the direction and rate of sap flow in tap‐roots, lateral roots and main stems of three mature Prosopis velutina Woot. trees o...
Downward redistribution of soil water through plant roots has important consequences for water and nutrient balance of arid and semi-arid ecosystems. Nevertheless, information on the seasonal patterns and magnitudes of redistribution is lacking for all but a few plant species. We measured sap flow in the taproot and three main lateral roots of a 10...
Establishment and recruitment of walnut trees (Juglans spp.) has declined in semiarid riparian systems over the last century. Juglans spp. may have important impacts on hydrologic processes in these riparian systems, including the redistribution of shallow soil water to subsurface zones through their root systems. To assess the potential impact of...
