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

[j] .草原生态系统中昆虫和草食动物的生态化学计量学研究[j] .中国农业大学学报（自然科学版），2005,(1):1 - 4。PI的问题是：与北方混合草原相比，南方干旱草原介导这些相互作用的潜在过程有多相似或有多不同？与更大尺度相关的模式是否提供了通过研究单个或附近草原无法获得的见解？作为一种优势的、多样化的地上食草动物，蚱蜢是一种很好的食草昆虫模型，可以用来评估北美大量原生草原的这些过程。该项目将考察12个地点因营养限制而对蚱蜢次生生产造成的限制，从德克萨斯州的干旱草原到新墨西哥州，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草、短草和混合草草原组成的高度动态的大陆中部地区，直到遇到南达科他州和加拿大的北部混合草系统。该样带将包括四个LTER站点（Jornada, Sevilleta， Shortgrass Steppe和Konza Prairie）。生态化学计量学为解决这些关键问题提供了主要的概念框架，利用质量平衡原理来解释营养水平之间转移的限制元素的调节。本研究将检验化学计量元素比（C:N:P）对蚱蜢二次生产的约束。一系列的预测将通过使用常见蚱蜢种类的C:N:P比率，从12个地点中摄取的食物和草进行测试。通过大型实验（火、放牧和/或添加营养物质）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.