SGER: Effects on Record Precipitation Inputs on Soil-Plant Nitrogen Relationships in Tallgrass Prairie

9321592布莱尔我们对高草生态系统的结构和功能的概念性理解是基于极端多变的气候，特别是降水，在这个系统中发挥的核心作用。 以前的研究已经证明了季节性缺水和长期干旱对养分循环过程和植物反应的重要性。 然而，对高草草原过量降水输入对植物群落和生态系统水平响应的影响知之甚少。 在Konza Prairie LTER站点，我们目前正在经历自1890年开始收集当地天气数据以来最潮湿的连续一年。 这一“100-500年事件”为我们提供了一个独特的机会，以研究过量降水对高草草原土壤和植物过程的影响，这是一个适应水分亏缺的系统。 我们预计，过量的降水输入改变土壤-植物N的关系，增加N的损失和N的限制，最大的后续影响发生在每年燃烧的流域高地网站。 我们要求提供资金，以便（1）量化创纪录的降水输入对每年燃烧和长期未燃烧流域的高地和低地地区的杂类草和草年产量的直接影响，这些流域目前没有用核心LTER基金进行测量，（2）评估土壤养分库的变化，重点是短期内氮素有效性和植物响应的模式（生长季节结束后和降水过多后的一年），和（3）提供了一个基础，以评估长期的相互作用，提高年降水量和火灾频率对氮限制和植物的反应。 SGER的资金将提供两个生长季节（1993年和1994年）的反应更详细的测量，并提供了一个基线的长期监测的Konza LTER计划。 我们将在每年燃烧和长期未燃烧的流域的高地和低地地区建立一系列成对的实验区，包括对照区和氮肥区。 要测量的响应变量将包括地上和地下植物生物量，氮损失火明年春天，氮矿化率和氮的可用性模式，在下一个生长季节，每年的地上净初级生产力，和植物群落组成。

9321592 Blair Our conceptual understanding of the structure and function of tallgrass ecosystems is based on the central role that an extremely variable climate, particularly precipitation, plays in this system. Previous research has documented the importance of seasonal water deficits, and longer-term droughts, on nutrient cycling processes and plant responses. However, much less is known about the impacts of excessive precipitation inputs on plant communities and ecosystem-level responses in tallgrass prairie. At the Konza Prairie LTER site we are currently experiencing the wettest consecutive one-year period since local weather data collections began in 1890. This "100-500 year event" has presented us with an unique opportunity to examine the effects of excess precipitation on soil and plant processes in tallgrass prairie, a system adapted to moisture deficits. We expect excess precipitation inputs to alter soil-plant N relationships and to increase N losses and N limitations, with greatest subsequent impacts occurring on the upland sites of annually burned watersheds. We request funding which will allow us to (1) quantify the immediate effects of record precipitation inputs on annual production of forbs and grasses on upland and lowland sites of annually burned and long-term unburned watersheds that are not currently measured with core LTER funds, (2) evaluate changes in soil nutrient pools, with emphasis on patterns on patterns of N availability and plant responses in the short term (end of this growing season and the year following excess precipitation), and (3) provide a basis for evaluating longer-term interactions of elevated annual precipitation and fire frequency on N-limitations and plant responses. SGER funding will provide for more detailed measurement of responses over two growing seasons(1993 and 1994), and provide a baseline for longer-term monitoring by the Konza LTER program. We will establish a series of paired experimental plots in both upland and lowland areas of annually burned and long-term unburned watersheds, consisting of control and N fertilized plots. Response variables to be measured will include above-and below-ground plant biomass, N losses to fire next spring, rates of N mineralization and patterns of N availability in the next growing season, annual above-ground NPP, and plant community composition.