News in 2012
Dec 10, 2012
Congratulations to Zeli Tan, who passed qualifying exams to continue his PhD program at EAPS!
Dec 10, 2012
Congratulations to Zhenong Jin, who passed qualifying exams to continue his PhD program at EAPS!
Nov 7, 2012
Congratulations to Yujie He, who successfully defended her MS thesis research. She will continue pursuing her PhD in our lab.
October 1, 2012
Welcome our newest PhD students to EBDL lab: Chang Liao, Shaoqing Liu, Jiahui Xu and Guangcun Hao!
July 14, 2012
Congratulations to Xinghua Sui, who led a study using TEM model, which was just published online in Climatic Change!
Citation:
Sui, X., G. Zhou, and Q. Zhuang (2012) Sensitivity of carbon budget to historical climate variability and atmospheric CO2 concentration in temperate grassland ecosystems in China, Climatic Change, DOI 10.1007/s10584-012-0533-2
Abstract:
Chinese temperate grasslands play an important role in the terrestrial carbon cycle. Based on the parameterization and validation of Terrestrial Ecosystem Model (TEM, Version 5.0), we analyzed the carbon budgets of Chinese temperate grasslands and their responses to historical atmospheric CO2 concentration and climate variability during 1951-2007. The results indicated that Chinese temperate grassland acted as a slight carbon sink with annual mean value of 7.3 Tg C, ranging from -80.5 to 79.6 Tg C yr-1. Our sensitivity experiments further revealed that precipitation variability was the primary factor for decreasing carbon storage. CO2 fertilization may increase the carbon storage (1.4 %) but cannot offset the proportion caused by climate variability (-15.3 %). Impacts of CO2 concentration, temperature and precipitation variability on Chinese temperate grassland cannot be simply explained by the sum of the individual effects. Interactions among them increased total carbon storage of 56.6 Tg C which 14.2 Tg C was stored in vegetation and 42.4 Tg C was stored in soil. Besides, different grassland types had different responses to climate change and CO2 concentration. NPP and RH of the desert and forest steppes were more sensitive to precipitation variability than temperature variability while the typical steppe responded to temperature variability more sensitively than the desert and forest steppes.
June 8, 2012
A study on coupled thermal and hydrological dynamics for the Arctic ecosystems has been just published, led by Yueyang.
Citation:
Jiang, Y., Q. Zhuang, and J. A. O'Donnell (2012), Modeling thermal dynamics of active layer soils and near-surface permafrost using a fully coupled water and heat transport model, J. Geophys. Res., 117, D11110, doi:10.1029/2012JD017512.
Abstract:
Thawing and freezing processes are key components in permafrost dynamics, and these processes play an important role in regulating the hydrological and carbon cycles in the northern high latitudes. In the present study, we apply a well-developed soil thermal model that fully couples heat and water transport, to simulate the thawing and freezing processes at daily time steps across multiple sites that vary with vegetation cover, disturbance history, and climate. The model performance was evaluated by comparing modeled and measured soil temperatures at different depths. We use the model to explore the influence of climate, fire disturbance, and topography (north- and south-facing slopes) on soil thermal dynamics. Modeled soil temperatures agree well with measured values for both boreal forest and tundra ecosystems at the site level. Combustion of organic-soil horizons during wildfire alters the surface energy balance and increases the downward heat flux through the soil profile, resulting in the warming and thawing of near-surface permafrost. A projection of 21st century permafrost dynamics indicates that as the climate warms, active layer thickness will likely increase to more than 3 meters in the boreal forest site and deeper than one meter in the tundra site. Results from this coupled heat-water modeling approach represent faster thaw rates than previously simulated in other studies. We conclude that the discussed soil thermal model is able to well simulate the permafrost dynamics and could be used as a tool to analyze the influence of climate change and wildfire disturbance on permafrost thawing.
May 23, 2012
Congratulations to Yujie, who won $1500 travel support to participate in a collaborative research in Alaska with Dr. Jen Harden at USGS! The support is from INTERFACE project funded by NSF
Abstract:
May 7, 2012
Yujie He was awarded a support to attend the Iowa High Performance Computing (IHPC) 2012 Summer School. Congratulations!
May 4, 2012
Congratulations to Yaling Liu, who passed qualifying exam to continue her PhD program at EAPS!
Apr. 27, 2012
Xiaoliang Lu led a study entitled "Modeling methane emissions from the Alaskan Yukon River basin, 1986-2005, by coupling a large-scale hydrological model and a process-based methane model" and has been published in Journal of Geophysical Research.
Citation:
Lu, X., and Q. Zhuang (2012), Modeling methane emissions from the Alaskan Yukon River basin, 1986-2005, by coupling a large-scale hydrological model and a process-based methane model, J. Geophys. Res., 117, G02010, doi:10.1029/2011JG001843.
Abstract:
Much progress has been made in methane modeling for the Arctic. However, there is still large uncertainty in emissions estimates due to the spatial variability in water table depth resulting from complex topographic gradients, and due to variations in methane production and oxidation due to complex freezing and thawing processes. Here we extended an extant methane emission module within a biogeochemistry model, the Terrestrial Ecosystem Model (TEM), to include a large-scale hydrology model, the variable infiltration capacity (VIC) model. The VIC model provides the required inputs, including freezing and thawing fronts, soil temperature and moisture, to the methane module. The effect of topography on the redistribution of soil moisture and water table depth was explicitly modeled using the TOPMODEL approach. The coupled modeling framework was applied to the Yukon River basin at a spatial resolution of 1 km from 1986 to 2005. The simulations show that the average annual net emissions of CH4 from the region are 4.01 Tg CH4 yr-1. El Nino phenomena usually lead to positive emission anomalies, while decreases in net CH4 emissions may be associated with strong La Nina events. Precipitation was found to be more closely related to CH4 dynamics than to soil temperature and active layer depth during the study period. This study suggests that the effects of soil freezing and thawing processes and the effects of microtopography on hydrology should be considered in the quantification of CH4 emissions.
Apr. 20, 2012
A study entitled "Spatially Explicit Parameterization of a Terrestrial Ecosystem Model and Its Application to the Quantification of Carbon Dynamics of Forest Ecosystems in the Conterminous United States" by Min Chen and Qianlai Zhuang has been published in Earth Interactions.
Citation:
Chen, M., Q. Zhuang (2012) Spatially Explicit Parameterization of a Terrestrial Ecosystem Model and Its Application to the Quantification of Carbon Dynamics of Forest Ecosystems in the Conterminous United States, Earth Interactions, DOI: 10.1175/2012EI400.1.
Abstract:
The authors use a spatially explicit parameterization method and the Terrestrial Ecosystem Model (TEM) to quantify the carbon dynamics of forest ecosystems in the conterminous United States. Six key parameters that govern the rates of carbon and nitrogen dynamics in TEM are selected for calibration. Spatially explicit data for carbon and nitrogen pools and fluxes are used to calibrate the six key parameters to more adequately account for the spatial heterogeneity of ecosystems in estimating regional carbon dynamics. The authors find that a spatially explicit parameterization results in vastly different carbon exchange rates relative to a parameterization conducted for representative ecosystem sites. The new parameterization method estimates that the net ecosystem production (NEP), the annual gross primary production (GPP), and the net primary production (NPP) of the regional forest ecosystems are 61% (0.02 Pg C; 1 Pg 5 1015 g) higher and 2% (0.11 Pg C) and 19% (0.45 Pg C) lower, respectively, than the values obtained using the traditional parameterization method for the period 1948-2000. The estimated vegetation carbon and soil organic carbon pool sizes are 51% (18.73 Pg C) lower and 29% (7.40 Pg C) higher. This study suggests that, to more adequately quantify regional carbon dynamics, spatial data for carbon and nitrogen pools and fluxes should be developed and used with the spatially explicit parameterization method.
Apr. 11, 2012
Congratulations to Xiaoliang just accepted a Post-Doctoral Scientist offer from the Ecosystems Center of the Marine Biological Laboratory at Woods Hole, MA!
Apr. 11, 2012
Yujie He was just awarded with a WISP Travel Grant! She will travel to 2012 Ecological Society of America annual meeting, Portland, Oregon in August to present her study on CO2 and CH4 emissions during the Holocene Thermal Maximum in Alaska. Congratulations!
Apr. 3, 2012
Xiaoliang Lu just defended his PhD dissertation, congratulations to Dr. Xiaolang Lu!
Apr. 2, 2012
Congratulation to Qing Zhu, passed his preliminary exam and became a PhD candidate!
Apr. 2, 2012
Congratulations to Zhangcai Qin, who just passed his preliminary exam and advanced to PhD candidacy!
Apr. 2, 2012
Yueyang Jiang has successfully defended his PhD dissertation! Congratulations Dr. Jiang!
Feb. 14, 2012
Yueyang led a study, entitled "Uncertainty analysis of vegetation distribution in the northern high latitudes during the 21st century with a dynamic vegetation model", has just been published in the journal, Ecology and Evolution.
Citation:
Jiang, Y., Q. Zhuang, S. Schaphoff, S. Sitch, A. Sokolov, D. Kicklighter, and J. Melillo (2012). Uncertainty analysis of vegetation distribution in the northern high latitudes during the 21st century with a dynamic vegetation model, ecology and Evolution, doi: 10.1002/ece3.85.
Abstract:
His study aims to assess how high-latitude vegetation may respond under various climate scenarios during the 21st century with a focus on analyzing model parameters induced uncertainty and how this uncertainty compares to the uncertainty induced by various climates. The analysis was based on a set of 10,000Monte Carlo ensemble Lund-Potsdam-Jena (LPJ) simulations for the northern high latitudes (45oN and polewards) for the period 1900 to 2100. The LPJ Dynamic Global Vegetation Model (LPJ-DGVM) was run under contemporary and future climates from four Special Report Emission Scenarios (SRES), A1FI, A2, B1, and B2, based on the Hadley Centre General Circulation Model (GCM), and six climate scenarios, X901M, X902L, X903H, X904M, X905L, and X906H from the Integrated Global System Model (IGSM) at the Massachusetts Institute of Technology (MIT). In the current dynamic vegetation model, some parameters are more important than others in determining the vegetation distribution. Parameters that control plant carbon uptake and light-use efficiency have the predominant influence on the vegetation distribution of both woody and herbaceous plant functional types. The relative importance of different parameters varies temporally and spatially and is influenced by climate inputs. In addition to climate, these parameters play an important role in determining the vegetation distribution in the region. The parameter-based uncertainties contribute most to the total uncertainty. The current warming conditions lead to a complexity of vegetation responses in the region. Temperate trees will be more sensitive to climate variability, compared with boreal forest trees and C3 perennial grasses. This sensitivity would result in a unanimous northward greenness migration due to anomalous warming in the northern high latitudes. Temporally, boreal needle-leaved evergreen plants are projected to decline considerably, and a large portion of C3 perennial grass is projected to disappear by the end of the 21st century. In contrast, the area of temperate trees would increase, especially under the most extreme A1FI scenario. As the warming continues, the northward greenness expansion in the Arctic region could continue.
Feb. 14, 2012
Yueyang led another study, entitled "Modeling Large Fire Frequency and Burned Area in Canadian Terrestrial Ecosystems with Poisson Models", has been published in the journal, Environmental Modeling & Assessment.
Citation:
Jiang, Y., Q. Zhuang, and D. Mandallaz (2012). Modeling Large Fire Frequency and Burned Area in Canadian Terrestrial Ecosystems with Poisson Models, Environ Model Assess, DOI 10.1007/s10666-012-9307-5.
Abstract:
Large wildland fires are major disturbances that strongly influence the carbon cycling and vegetation dynamics of Canadian boreal ecosystems. Although large wildland fires have recently received much scrutiny in scientific study, it is still a challenge for researchers to predict large fire frequency and burned area. Here, we use monthly climate and elevation data to quantify the frequency of large fires using a Poisson model, and we calculate the probability of burned area exceeding a certain size using a compound Poisson process. We find that the Poisson model simulates large fire occurrence well during the fire season (May through August) using monthly climate, and the threshold probability calculated by the compound Poisson model agrees well with historical records. Threshold probabilities are significantly different among different Canadian ecozones, with the Boreal Shield ecozone always showing the highest probability. The fire prediction model described in this study and the derived information will facilitate future quantification of fire risks and help improve fire management in the region.
Jan. 30, 2012
Congratulations to Yujie He, who has been selected and supported to participate in the DOE workshop "Strategies to promote integrated experiment-model approaches to terrestrial ecosystem study" that will be held in Washington DC!
Jan. 20, 2012
A great article highlighting a recent paper (PCCRC paper 1147) led by EAS grad student Xudong Zhu, Rising methane emissions in response to climate change in Northern Eurasia during the 21st century
Abstract:
Featured in environmental research web.The article is also copied below, and you can read the full paper here.