@article{ryu_chen_noormets_bresee_ollinger_2008, title={Comparisons between PnET-Day and eddy covariance based gross ecosystem production in two Northern Wisconsin forests}, volume={148}, ISSN={["1873-2240"]}, DOI={10.1016/j.agrformet.2007.08.005}, abstractNote={Abstract The PnET-Day model was independently parameterized to compare with estimated eddy covariance gross ecosystem production (GEP; gC m −2  day −1 ) in a mature mixed hardwood and a mature red pine ( Pinus resinosa ) forest in Northern Wisconsin during the growing season of 2002 and 2003. The mature hardwood forest was dominated by Populus tremuloides , Populus grandidentata , Betula papyrifera , Quercus rubra , Acer rubrum , and Acer saccharum . We evaluated the model's capability to predict the seasonal and interannual dynamics of GEP and explored the sources of discrepancy between PnET-Day and eddy covariance GEP estimates. GEP was directly estimated from the two eddy-flux towers, one for each forest type, during 2002 and 2003. PnET-Day growing season GEP for the mature hardwood forest was 12% higher in 2002 and 12% lower in 2003 than eddy covariance GEP estimates, while the modeled growing season GEP of the mature red pine forest was overestimated by 43 and 32% compared to eddy covariance GEP in 2002 and 2003, respectively. The disagreement between the two methods was attributed to year-to-year variability in foliage biomass and foliar nitrogen (N) in the mature hardwood forest and to high foliage biomass and specific leaf weight in the mature red pine forest (>50% larger than red pine in Harvard Forest where the model was developed and validated). The difference between PnET-Day and eddy covariance GEP estimates was greatest in May in the hardwood forest, primarily due to the discrepancy between the true and parameterized foliage onset day. Our results suggest that improved prediction of foliage onset is necessary to improve PnET-Day estimation of GEP in a hardwood forest.}, number={2}, journal={AGRICULTURAL AND FOREST METEOROLOGY}, author={Ryu, Soung-Ryoul and Chen, Jiquan and Noormets, Asko and Bresee, Mary K. and Ollinger, Scott V.}, year={2008}, month={Feb}, pages={247–256} }
 @inproceedings{yang_sharma_burns_cheng_2008, title={Hydrolysis and fermentation of new switchgrass germplasm for bioethanol production}, volume={083799}, booktitle={Proceedings of the ASABE Annual International Meeting (Providence, Rhode Island)}, author={Yang, Y. and Sharma, R. R. and Burns, J. C. and Cheng, J. J.}, year={2008} }
 @inproceedings{keshwani_cheng_li_burns_chiang_2007, title={Microwave pretreatment of switchgrass to enhance enzymatic hydrolysis}, volume={077127}, DOI={10.13031/2013.23472}, abstractNote={Switchgrass is a promising lignocellulosic biomass for fuel-ethanol production. However, pretreatment of lignocellulosic materials is necessary to improve its susceptibility to enzymatic hydrolysis. The objectives of this study were to examine the feasibility of microwave pretreatment to enhance enzymatic hydrolysis of switchgrass and to determine the optimal pretreatment conditions. Switchgrass samples immersed in water, dilute sulfuric acid and dilute sodium hydroxide solutions were exposed to microwave radiation at varying levels of radiation power and residence time. Pretreated solids were enzymatically hydrolyzed and reducing sugars in the hydrolysate were analyzed. Microwave radiation of switchgrass at lower power levels resulted in more efficient enzymatic hydrolysis. The application of microwave radiation for 10 minutes at 250 watts to switchgrass immersed in 3% sodium hydroxide solution (w/v) produced the highest yields of reducing sugar. Results were comparable to conventional 60 minute sodium hydroxide pretreatment of switchgrass. The findings suggest that combined microwave-alkali is a promising pretreatment method to enhance enzymatic hydrolysis of switchgrass.}, booktitle={Proceedings of the ASABE Annual International Meeting (Minneapolis, Minnesota)}, author={Keshwani, D. R. and Cheng, J. J. and Li, L. and Burns, J. C. and Chiang, V.}, year={2007} }
 @inbook{silbernagel_chen_noormets_song_2006, title={Conducting sound ecological studies at the landscape scale: hypotheses, experiments and challenges}, booktitle={Ecology of Hierarchical Landscapes: From Theory to Application}, publisher={Carbondale, IL: Nova Publishing}, author={Silbernagel, J. and Chen, J. and Noormets, A. and Song, B.}, editor={J. Chen, S. C. Saunders and K. D. Brosofske and Crow, T. R.Editors}, year={2006}, pages={283–297} }
 @article{deforest_noormets_mcnulty_sun_tenney_chen_2006, title={Phenophases alter the soil respiration-temperature relationship in an oak-dominated forest}, volume={51}, ISSN={["1432-1254"]}, DOI={10.1007/s00484-006-0046-7}, abstractNote={Soil respiration (SR) represents a major component of forest ecosystem respiration and is influenced seasonally by environmental factors such as temperature, soil moisture, root respiration, and litter fall. Changes in these environmental factors correspond with shifts in plant phenology. In this study, we examined the relationship between canopy phenophases (pre-growth, growth, pre-dormancy, and dormancy) and SR sensitivity to changes in soil temperature (T(S)). SR was measured 53 times over 550 days within an oak forest in northwest Ohio, USA. Annual estimates of SR were calculated with a Q(10) model based on T(S) on a phenological (PT), or annual timescale (AT), or T(S) and soil volumetric water content (VWC) on a phenological (PTM) or annual (ATM) timescale. We found significant (p<0.01) difference in apparent Q(10) from year 2004 (1.23) and year 2005 (2.76) during the growth phenophase. Accounting for moisture-sensitivity increased model performance compared to temperature-only models: the error was -17% for the ATM model and -6% for the PTM model. The annual models consistently underestimated SR in summer and overestimated it in winter. These biases were reduced by delineating SR by tree phenophases and accounting for variation in soil moisture. Even though the bias of annual models in winter SR was small in absolute scale, the relative error was about 91%, and may thus have significant implications for regional and continental C balance estimates.}, number={2}, journal={INTERNATIONAL JOURNAL OF BIOMETEOROLOGY}, author={DeForest, Jared L. and Noormets, Asko and McNulty, Steve G. and Sun, Ge and Tenney, Gwen and Chen, Jiquan}, year={2006}, month={Nov}, pages={135–144} }
 @inbook{noormets_ewers_sun_mackay_zheng_mcnulty_chen_2006, title={Water and carbon cycles in heterogeneous landscapes: an ecosystem perspective}, ISBN={1600210473}, booktitle={Ecology of Hierarchical Landscapes: From Theory to Application}, publisher={Carbondale, IL: Nova Publishing}, author={Noormets, A. and Ewers, B. and Sun, G. and Mackay, S. and Zheng, D. and McNulty, S. and Chen, J.}, editor={J. Chen, S. C. Saunders and K. D. Brosofske and Crow, T. R.Editors}, year={2006}, pages={89–123} }
 @article{zheng_chen_noormets_euskirchen_le moine_2005, title={Effects of climate and land use on landscape soil respiration in northern Wisconsin, USA: 1972 to 2001}, volume={28}, ISSN={["1616-1572"]}, DOI={10.3354/cr028163}, abstractNote={Changes in climate and land use affect soil respiration rates (SRR) significantly, but studies of these effects across entire landscapes are rare. We simulated responses of landscape mean SRR (LMSRR) to such changes from May to October over a 30 yr period in a managed, predominantly forested landscape in northern Wisconsin, USA, using: (1) 6 satellite-derived land-cover maps (1972, 1978, 1982, 1987, 1992, and 2001); (2) monthly air temperature data in the corresponding years of the cover maps; and (3) SRR models driven by soil temperature (Ts) at 5 cm depth. LMSRR seemed to increase linearly by 77% from 0.625 in May to 1.104 g CO2 m -2 h -1 in July, and then decreased at an increasing rate to 0.411 g CO2 m -2 h -1 in October. LMSRR was more sensitive to an increase of mini- mum temperature than that of mean or maximum temperature, suggesting that future climate change might impact SRR in high-latitude forests more than other biomes. LMSRR in September over the study period was similar to that of June but with 92% higher variation, while both landscape mean air temperature and precipitation in September had lower variation than in June. This indicates that the topsoil layer functions differently during soil warming and cooling phases. Changes in land cover composition from 1972 to 2001 increased LMSRR by 2.8 to 3.1% while 2°C differences in growing season mean air temperature increased the SRR by 6.7 to 7.0%. The combined effects of both vari- ables on the SRR are more complex, varying from 3.8 to 10.0%.}, number={2}, journal={CLIMATE RESEARCH}, author={Zheng, DL and Chen, JQ and Noormets, A and Euskirchen, ES and Le Moine, J}, year={2005}, month={Mar}, pages={163–173} }
 @article{chen_brosofske_noormets_crow_bresee_le moine_euskirchen_mather_zheng_2004, title={A working framework for quantifying carbon sequestration in disturbed land mosaics}, volume={33}, ISSN={["0364-152X"]}, DOI={10.1007/s00267-003-9131-4}, journal={ENVIRONMENTAL MANAGEMENT}, author={Chen, Jiquan and Brosofske, Kimberley D. and Noormets, Asko and Crow, Thomas R. and Bresee, Mary K. and Le Moine, James M. and Euskirchen, Eugenie S. and Mather, Steve V. and Zheng, Daolan}, year={2004}, month={Jul}, pages={S210–S221} }
 @misc{noormets_zhou_chen_2004, title={EC_Processor}, author={Noormets, A. and Zhou, R. and Chen, J.}, year={2004} }
 @article{chen_frey_2004, title={Optimization under variability and uncertainty: A case study for NOx emissions control for a gasification system}, volume={38}, ISSN={["1520-5851"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-10644257613&partnerID=MN8TOARS}, DOI={10.1021/es0351037}, abstractNote={Methods for optimization of process technologies considering the distinction between variability and uncertainty are developed and applied to case studies of NOx control for Integrated Gasification Combined Cycle systems. Existing methods of stochastic optimization (SO) and stochastic programming (SP) are demonstrated. A comparison of SO and SP results provides the value of collecting additional information to reduce uncertainty. For example, an expected annual benefit of 240,000 dollars is estimated if uncertainty can be reduced before a final design is chosen. SO and SP are typically applied to uncertainty. However, when applied to variability, the benefit of dynamic process control is obtained. For example, an annual savings of 1 million dollars could be achieved if the system is adjusted to changes in process conditions. When variability and uncertainty are treated distinctively, a coupled stochastic optimization and programming method and a two-dimensional stochastic programming method are demonstrated via a case study. For the case study, the mean annual benefit of dynamic process control is estimated to be 700,000 dollars, with a 95% confidence range of 500,000 dollars to 940,000 dollars. These methods are expected to be of greatest utility for problems involving a large commitment of resources, for which small differences in designs can produce large cost savings.}, number={24}, journal={ENVIRONMENTAL SCIENCE & TECHNOLOGY}, author={Chen, JJ and Frey, HC}, year={2004}, month={Dec}, pages={6741–6747} }
 @article{noormets_chen_bridgham_weltzin_pastor_dewey_lemoine_2004, title={The effects of infrared loading and water table on soil energy fluxes in northern peatlands}, volume={7}, ISSN={["1435-0629"]}, DOI={10.1007/s10021-004-0013-2}, number={5}, journal={ECOSYSTEMS}, author={Noormets, A and Chen, JQ and Bridgham, SD and Weltzin, JF and Pastor, J and Dewey, B and LeMoine, J}, year={2004}, month={Aug}, pages={573–582} }
 @inproceedings{mota_cheng_reyes f. l._2003, title={Quantifying nitrifying bacteria in bioreactors treating swine wastewater}, booktitle={2003 Quad Conference (Blacksburg, VA)}, author={Mota, C. R. and Cheng, J. and Reyes F. L.}, year={2003} }