Regulation of the Growth and Activity of Leaf-Decomposing Fungi by Dissolved Nutrients (N and P) in Streams

小行星9407232 本研究的目的是研究溶解性营养物质（N和P）在调节叶分解溪流真菌的生长和活性的作用。大多数溪流真菌群落的定量研究都发生在高营养浓度的溪流中。因此，鲜为人知的是，即使我们目前的理解流生态系统功能的低营养浓度的流中的真菌活动来自这样的系统的研究。将测定营养物浓度极低的硬水和软水水流中的真菌生长和孢子形成速率、真菌生物量浓度和真菌产量，并与营养物浓度较高的水流中的类似数据进行比较。最近，已经描述了通过测定14 C-乙酸酯掺入麦角固醇的速率来估计天然真菌群落的瞬时生长速率的方法。这种方法已被改编用于流真菌群落，并将用于分解落叶在研究流。这些数据以及作为真菌生物量衡量标准的麦角固醇含量的测定将有助于估计叶片降解期间和年周期内溪流中的真菌产量。上述比较研究将使用这两种产量估计数。N和P的影响将直接在田间试验中测量，其中流经河边人工渠道的水将用N、P或两者的营养物质进行修正，并确定真菌群落的响应。将构建环境模拟实验室研究中生长在落叶层上的营养贫乏和营养丰富的溪流中的真菌分离株的有机物预算，以确定真菌是否表现出不同的资源分配策略，以应对不同的营养浓度。 该项目将提供第一个研究工作，集中在溪流中真菌群落结构和生物量的营养限制的作用。PI将使用一种新的技术来测量真菌的生长速度和群落结构。

9407232 Subberkropp This study is designed to examine the role of dissolved nutrients (N and P) in regulating the growth and activity of leaf-decomposing stream fungi. Most quantitative studies of stream fungal communities have occurred in streams with high nutrient concentrations. Consequently, little is known concerning fungal activities in streams with low nutrient concentrations even though much of our current understanding of stream ecosystem function has come from studies of such systems. Rates of fungal growth and sporulation, concentrations of fungal biomass and fungal production in both hardwater and softwater streams with very low nutrient concentrations will be determined and compared with similar data from streams containing higher nutrient concentrations. Recently, a method for estimating instantaneous growth rates of natural fungal communities by determining rates of incorporation of 14C-acetate into ergosterol has been described. This method has been adapted for use with stream fungal communities and will be used on decomposing leaf litter in the study streams. These data, together with determination of ergosterol contents as a measure of fungal biomass will allow estimation of fungal production during leaf degradation and in streams over an annual cycle. Both types of production estimates will be used in the comparative studies mentioned above. The effects of N and P will be measured directly in field experiments in which water flowing through streamside artificial channels will be amended with N, P or both nutrients and the response of fungal communities determined. Organic matter budgets for fungal isolates from nutrient poor and nutrient rich streams growing on leaf litter in environmental simulating laboratory studies will be constructed to determine if fungi exhibit different strategies of resource allocation in response to varying nutrient concentrations. %%% This project will provide the first research effort concentrating on the role of nutrient limitation of fungal community structure and biomass in streams. The PI will be using a novel technique to measure fungal growth rates and community structure.