LTER Cross-Site: Ecological Stoichiometry of North American Grassland Grasshoppers (Acrididae) Along a Latitudinal Gradient

乔恩，ANTHONYDEB 0087253《北美草原蝗虫(蝗科)沿纬度梯度的生态化学计量学》草原生态系统中的昆虫食草动物在初级生产力、植物种类组成和营养动态的可变马赛克中遇到了广泛不同的食物质量。PI问：与北方混草草原相比，南方干旱草原调解这些相互作用的潜在过程有多相似或有多大不同？与更大规模相关的模式是否提供了通过研究单一或附近草原无法获得的洞察力？作为优势和多样化的地上食草动物，蝗虫是一种很好的模式昆虫食草动物，可以在北美大量的本土草原上评估这些过程。从德克萨斯州的干旱草原到新墨西哥州的干旱草原，再到俄克拉荷马州、堪萨斯州、科罗拉多州和内布拉斯加州的高度活跃的中大陆地区，直至遇到南达科他州和加拿大的北部混合草地系统，PI将审查由于营养限制而对蝗虫次级生产造成的限制。这一样带将包括4个LTER站点(Jornada、Sevilleta、Shortgras草原和Konza Prairie)。生态化学计量学为解决这些关键问题提供了基本的概念框架，利用质量平衡原理来解释限制元素在营养水平之间转移的调节。这项研究将检验化学计量元素比率(C：N：P)对蝗虫次生生产力的限制。一系列预测将使用12个地点中每个地点常见蝗虫物种、摄取的食物和草的C：N：P比率进行验证。通过大型实验(火、放牧和/或营养添加)操纵食品质量的站点提供了更好地确定因果关系的机会。

JOERN, ANTHONYDEB 0087253"Ecological stoichiometry of North American grassland grasshoppers (Acrididae) along a latitudinal gradient"Insect herbivores in grassland ecosystems encounter widely varying food quality embedded in a variable mosaic of primary production, plant species composition and nutrient dynamics. The PI's asked: how similar or how different are the underlying processes mediating these interactions in southern arid grassland compared to northern mixed-grass prairie? Do patterns associated with larger scales provide insight that cannot be obtained by studying a single or nearby grasslands? As dominant and diverse aboveground herbivores, grasshoppers are an excellent model insect herbivore to evaluate these processes for a wide array of native North American grasslands. The PI will examine constraints on grasshopper secondary production resulting from limiting nutrients across twelve sites ranging from arid grasslands in Texas to New Mexico, through a highly dynamic mid-continent set of sites comprising tallgrass, shortgrass and mixed grass prairies in Oklahoma, Kansas, Colorado and Nebraska until northern mixed grass systems in South Dakota and Canada are encountered. Four LTER sites will be included in this transect (Jornada, Sevilleta, Shortgrass Steppe and Konza Prairie).Ecological stoichiometry provides the primary conceptual framework for addressing these key issues, employing the principle of mass balance to account for the regulation of limiting elements in their transfer between trophic levels. This research will examine stoichiometric elemental ratios (C:N:P) as a constraint on secondary production in grasshoppers. A series of predictions will be tested using C:N:P ratios of common grasshopper species, ingested food and grass from each of twelve sites. Sites that manipulate food quality with large experiments (fire, grazing and/or nutrient additions) provide an opportunity to better identify causal relationships.