Coupled biogeochemical cycling of water, silicon and cations in a temperate forest-shale system.

温带森林-页岩系统中水、硅和阳离子的耦合生物地球化学循环。

• 批准号: 1227107
• 负责人: Louis Derry
• 金额: $ 20.12万
• 依托单位: Cornell University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-09-15 至 2016-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1227107&HistoricalAwards=false
• 关键词: Coupled; biogeochemical; cycling; water; silicon

This project is focused on understanding the linkages between water acquisition by temperate forest trees (maples, oaks) and their strategies to acquire mineral nutrients, especially calcium and silica. Trees act as powerful "pumps" to bring up soil water and groundwater, and as the soil wets and dries through the season, trees shift their water sources as needed. The investigation will employ isotopes of hydrogen and oxygen to trace those shifts in a heavily instrumented biogeochemistry study site in central Pennsylvania, part of the NSF Critical Zone Observatory network. At the same time as they acquire water, trees acquire nutrients from the soil. Investigators will test ideas about how mineral nutrient sources may change as water sources change. Trees take up nutrients they need, and when leaf drop occurs, recycle them to the soil. One question is how important is the "mining" of nutrients from deep levels in the nutrient budget. If trees cannot mine nutrients, then they are limited to the store that is in shallow soil and in standing vegetation. Some evidence suggests that in some species tree roots leak water to shallow soils - one possible explanation is that they do this to make nutrients available from otherwise dry, shallow soils during times of water stress. Strontium isotopes and the ratios of germanium to silicon and strontium to calcium will be used to test these hypotheses more explicitly. This builds on previous work on mineral nutrient cycles the investigators have carried out in tropical systems.The response of forests and of biogeochemical cycles to climate change is an important consideration because of the possible feedbacks on the carbon and water cycles. A prediction of most climate models is for more variable precipitation patterns, with increased periods of drought even under overall wetter conditions. Water and nutrient acquisition strategies for species that are better suited to these variable conditions may predict success patterns among species in adapting to climate change in temperate forests. Such species may also be able to increase their utilization of CO2 under increased CO2 levels if they are better able to acquire nutrients even under conditions of low soil water availability. It is critical to improve our understanding of the coupling between water and nutrient cycles in order to better predict the response of these important ecosystems to climate change, and their future impacts on the carbon and water cycles.

该项目的重点是了解温带林木(枫树、橡树)的水分获取与它们获取矿物质营养，特别是钙和二氧化硅的策略之间的联系。树木扮演着强大的“水泵”的角色，提高土壤水分和地下水，随着土壤在整个季节的湿润和干燥，树木根据需要改变它们的水源。这项调查将使用氢和氧的同位素来追踪这些变化，地点位于宾夕法尼亚州中部，是NSF临界区天文台网络的一部分。树木在获得水分的同时，也从土壤中获得养分。调查人员将测试有关矿物质营养来源如何随着水源变化而变化的想法。树木吸收它们所需的养分，当落叶发生时，将它们回收到土壤中。一个问题是，在营养收支中，从深层“开采”营养有多重要。如果树木不能挖掘养分，那么它们就只能储存在浅层土壤和直立的植被中。一些证据表明，在某些物种中，树根会将水分渗入浅层土壤--一个可能的解释是，它们这样做是为了在水分胁迫期间从原本干燥的浅层土壤中获得养分。锶同位素和锗与硅以及锶与钙的比率将被用来更明确地检验这些假设。这是建立在研究人员之前在热带系统开展的关于矿物营养循环的工作的基础上的。森林和生物地球化学循环对气候变化的反应是一个重要的考虑因素，因为可能会对碳循环和水循环进行反馈。大多数气候模型的预测是对更多变的降水模式的预测，即使在总体较潮湿的条件下，干旱周期也会增加。更适合这些可变条件的物种的水分和养分获取战略可以预测物种在适应温带森林气候变化方面的成功模式。如果这些物种即使在土壤水分有效性较低的情况下也能够更好地获得养分，它们也可能能够在二氧化碳水平增加的情况下增加对二氧化碳的利用。为了更好地预测这些重要生态系统对气候变化的反应及其未来对碳循环和水循环的影响，提高我们对水和水循环之间耦合的理解是至关重要的。