Biogeochemical cycling in central Ontario sugar maple forests

随着气候变化，安大略省南部的阔叶林已经并将继续受到多种环境压力，包括酸沉积、氮含量升高和微量金属沉积。这些应激源可以单独或协同作用，破坏这些重要自然生态系统的生态完整性。这种生态完整性的一个关键衡量标准是养分循环；例如，土壤酸化会改变盐基阳离子和微量金属循环，而氮沉积增加的长期输入可能会扰乱这些系统的氮循环。最终，生物地球化学循环的变化可能导致其他生态参数的破坏，如物种组成的变化，并导致森林健康的恶化。以前对安大略省森林生物地球化学循环的研究大多集中在前寒武纪地盾上覆的地区，那里的酸性土壤占主导地位；对该地区南部的生物地球化学循环知之甚少，这最终可能对氮等污染物更敏感。这项工作的总体短期目标是描述安大略省南部五个以糖枫为主的地点主要营养物质和微量金属的生物地球化学循环，这些地点是安大略省环境部森林健康监测计划的一部分。这些地点在土壤化学、气候和污染负荷方面各不相同，预计将有截然不同的生物地球化学循环。已经开发了一些生物地球化学模型，以评估森林生态系统对一些污染物(酸沉积、氮、痕量金属)的动态响应，这些污染物需要详细的特定地点的输入数据。多种型号(如Magic、VSD、For Safe等)将在研究地点进行评估，这些地点代表了在安大略省糖枫森林观察到的土壤、气候和大气沉积的范围。长期目标是利用动态生物地球化学模型对安大略省阔叶林在不断变化的气候下对酸、氮和金属沉积的反应进行区域评估。

Hardwood forests in southern Ontario have been, and will continue to be, subjected to a multitude of environmental stressors including acid deposition, elevated nitrogen and trace metal deposition along with climate change. The stressors can act individually and in concert to disrupt the ecological integrity of these important natural ecosystems. A key measure of this ecological integrity is nutrient cycling; acidification of soils for example can alter base cation and trace metal cycling while chronic inputs of elevated nitrogen deposition can disrupt the nitrogen cycling of these systems. Ultimately, alterations in biogeochemical cycling may lead to the disruption of other ecological parameters such as alterations in species composition and lead to a deterioration of forest health. Most previous studies on forest biogeochemical cycling in Ontario have generally focused on regions overlying the Precambrian Shield, where acid soils dominate; little is known about biogeochemical cycling in the southern part of the region, which may ultimately be more sensitive to polutants such as nitrogen. The overall short-term objective of this work is to characterize the biogeochemical cycling of major nutrients and trace metals at five sugar maple dominated sites in southern Ontario that are part of the Ontario Ministry of Environment's forest health monitoring program. The sites vary in terms of soil chemistry, climate and pollution loadings and are expected to have contrasting biogeochemical cycling. A number of biogeochemical models have been developed to assess the dynamic response of forest ecosystems to a number of pollutants (acid deposition, nitrogen, trace metals) which require detailed site-specific input data. Several models (e.g. (MAGIC, VSD, FORSAFE etc.) will be evalauted at the study sites, which represent the range of soil, climate and atmospheric deposition observed in Ontario's sugar maple forests. The long-term objective is to undertake a regional assessment of the response of Ontario's hardwood forests to acid, nitrogen and metal deposition under a changing climate using dynamic biogeochemical models.