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所起的核心作用。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，关于过度的降水输入对高草草原植物群落和生态系统水平的反应的影响，我们知道的要少得多。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连续一年最潮湿的时期。这一“100-500年事件”为我们提供了一个独特的机会来研究过度降水对塔尔格拉斯草原土壤和植物过程的影响，这是一种适应水分不足的系统。我们预计，过量的降水输入将改变土壤-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烧毁的流域的旱地地点。我们要求的资金将使我们能够(1)量化创纪录的降水输入对每年燃烧和长期未燃烧的流域的高地和低地的杂草和牧草年产量的直接影响，(2)评估土壤营养库的变化，重点是短期(本生长季结束和过度降水后的下一年)N有效性的模式和植物反应，以及(3)为评估年降水量和火灾频率增加对N限制和植物反应的长期相互作用提供基础。SGER资金将对两个生长季节(1993和1994年)的反应进行更详细的衡量，并为Konza LTER计划的长期监测提供基线。在年烧和长期未烧流域的旱地和低地两个地区建立一系列配对试验区，包括对照和氮肥试验区。需要测量的响应变量将包括地上和地下植物生物量、明年春季火灾造成的N损失、N矿化速率和下一个生长季的N有效性模式、年度地上NPP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.