PNET-BGC: MODELING BIOGEOCHEMICAL PROCESSES (GBONDO-TUGBAWA ET AL. 2001)

This archived model product contains the directions, executables, and procedures for running PnET-BGC to recreate the results of Gbondo-Tugbawa, S.S., C.T. Driscoll , J.D. Aber and G.E. Likens. 2001. The evaluation of an integrated biogeochemical model (PnET-BGC) at a northern hardwood forest ecosystem. Water Resources Research 37:1057-1070. Gbondo-Tugbawa et al,. 2001 Excerptfrom Abstract: An integrated biogeochemical model (PnET-BGC) was formulated to simulate chemical transformations of vegetation, soil, and drainage water in northern forest ecosystems. The model operates on a monthly time step and depicts the major biogeochemical processes, such as forest canopy element transformations, hydrology, soil organic matter dynamics, nitrogen cycling, geochemical weathering, and chemical equilibrium reactions involving solid and solution phases. The model was evaluated against soil and stream data at the Hubbard Brook Experimental Forest, New Hampshire. Model predictions of concentrations and fluxes of major elements generally agreed reasonably well with measured values, as estimated by normalized mean error and normalized mean absolute error. Model output of soil base saturation and stream acid neutralizing capacity were sensitive to parameter values of soil partial pressure of carbon dioxide, soil mass, soil cation exchange capacity, and soil selectivity coefficients of calcium and aluminum. PnET-BGC can be used as a tool to evaluate the response of soil and water chemistry of forest ecosystems to disturbances such as clear-cutting, climatic events, and atmospheric deposition.PnET-BGC, was used to investigate inputs and dynamics of S in a northern hardwood forest at the Hubbard Brook Experimental Forest (HBEF) (Gbondo-Tugbawa et al., 2002). The changes in soil S pools and stream-water were simulated to assess the response 22 SO4 to both atmospheric S deposition and forest clear-cutting disturbances. Watershed studies across the northeastern United States have shown that stream losses of exceed atmospheric sulfur (S) deposition. Understanding the processes responsible for this additional source of S is critical to quantifying ecosystem response to ongoing and potential future controls on SO2 emission.本归档模型产品包含用于运行PnET-BGC模型（PnET-BGC）以复现Gbondo-Tugbawa、S.S.、C.T. Driscoll、J.D. Aber及G.E. Likens于2001年发表于《Water Resources Research》（37卷：1057-1070）的论文《北方硬木森林生态系统中集成生物地球化学模型（PnET-BGC）的评估》的研究成果所需的操作指南、可执行程序与运行流程。以下为Gbondo-Tugbawa等人2001年研究的摘要节选：本研究构建了集成生物地球化学模型（integrated biogeochemical model）PnET-BGC，用于模拟北方森林生态系统中植被、土壤与排水的化学转化过程。该模型以月为时间步长，刻画了核心生物地球化学过程，包括林冠元素转化、水文循环、土壤有机质动态、氮循环、地球化学风化以及涉及固相与液相的化学平衡反应。研究以新罕布什尔州哈伯德布鲁克实验林（Hubbard Brook Experimental Forest）的土壤与溪流监测数据对该模型进行了验证。通过归一化平均误差与归一化平均绝对误差评估可知，模型对主要元素浓度与通量的预测结果与实测值整体吻合度较好。模型输出的土壤盐基饱和度与溪流酸中和能力结果，对土壤二氧化碳分压、土壤质量、土壤阳离子交换量以及钙与铝的土壤选择性系数等参数取值较为敏感。PnET-BGC模型可作为评估森林生态系统土壤与水化学对皆伐、气候事件及大气沉降等干扰响应的工具。后续Gbondo-Tugbawa等人（2002）依托哈伯德布鲁克实验林（HBEF）的北方硬木森林场景，使用PnET-BGC模型开展了硫（S）的输入与动态变化研究。该研究通过模拟土壤硫库与溪流水体的变化，评估了硫酸根（SO4）对大气硫沉降与森林皆伐干扰的响应。美国东北部的多项流域研究表明，溪流的硫流失量超过了大气硫沉降量。明确该额外硫来源背后的过程机制，对于量化生态系统对当前及未来潜在二氧化硫（SO2）排放管控措施的响应至关重要。