Chen Jing

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Simulating the impacts of disturbances on forest carbon cycling in North America : processes, data, models, and challenges

2011-11-08 , Liu, Shuguang , Bond-Lamberty, Benjamin , Hicke, Jeffrey A. , Vargas, Rodrigo , Zhao, Shuqing , Chen, Jing , Edburg, Steven L. , Hu, Yueming , Liu, Jinxun , McGuire, A. David , Xiao, Jingfeng , Keane, Robert , Yuan, Wenping , Tang, Jianwu , Luo, Yiqi , Potter, Christopher , Oeding, Jennifer

Forest disturbances greatly alter the carbon cycle at various spatial and temporal scales. It is critical to understand disturbance regimes and their impacts to better quantify regional and global carbon dynamics. This review of the status and major challenges in representing the impacts of disturbances in modeling the carbon dynamics across North America revealed some major advances and challenges. First, significant advances have been made in representation, scaling, and characterization of disturbances that should be included in regional modeling efforts. Second, there is a need to develop effective and comprehensive process-based procedures and algorithms to quantify the immediate and long-term impacts of disturbances on ecosystem succession, soils, microclimate, and cycles of carbon, water, and nutrients. Third, our capability to simulate the occurrences and severity of disturbances is very limited. Fourth, scaling issues have rarely been addressed in continental scale model applications. It is not fully understood which finer scale processes and properties need to be scaled to coarser spatial and temporal scales. Fifth, there are inadequate databases on disturbances at the continental scale to support the quantification of their effects on the carbon balance in North America. Finally, procedures are needed to quantify the uncertainty of model inputs, model parameters, and model structures, and thus to estimate their impacts on overall model uncertainty. Working together, the scientific community interested in disturbance and its impacts can identify the most uncertain issues surrounding the role of disturbance in the North American carbon budget and develop working hypotheses to reduce the uncertainty.

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Modified local sands for the mitigation of harmful algal blooms

2011-01-27 , Pan, Gang , Chen, Jing , Anderson, Donald M.

A new method was developed for marine harmful algal bloom (HAB) mitigation using local beach sand or silica sand modified with chitosan and polyaluminum chloride (PAC). Untreated sand was ineffective in flocculating algal cells, but 80% removal efficiency was achieved for Amphidinium carterae Hulburt and a Chlorella sp. in 3 min (t80 = 3 min) using 120 mg L-1 sand modified with 10 mg L-1 PAC and 10 mg L-1 chitosan. After several hours 92% – 96% removal was achieved. The t80 for removing A. carterae using the modifiers only (PAC and chitosan combined) was 60 min and for Chlorella sp. 120 min, times which are much slower than with the corresponding modified sand. Sands were critical for speeding up the kinetic processes of flocculation and sedimentation of algal flocs. PAC was helpful in forming small flocs and chitosan is essential to bridge the small flocs into large dense flocs. Chitosan was also important in inhibiting the escape of cells from the flocs. Chitosan and PAC used together as modifiers make it possible to use local beach sands for HAB mitigation in seawater. Economical and environmental concerns could be reduced through the use of sands and biodegradable chitosan, but the potential impacts of PAC need further study.