Wild Rice Population Dynamics and Nutrient Cycles

野生稻种群动态和养分循环

• 批准号: 0211691
• 负责人: John Pastor
• 金额: $ 54.31万
• 依托单位: University of Minnesota-Twin Cities
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-09-15 至 2007-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0211691&HistoricalAwards=false
• 关键词: Wild; Rice; Population; Dynamics; Nutrient

Populations of plants and animals typically undergo regular oscillations or boom-and-bust cycles in nature. Ecologists have long been interested in the causes of these oscillations. Ecological theory predicts that any delay in a population will cause it to oscillate. Most of the processes that have been proposed as causes of delays are purely population processes, such as delays in birth rate. But if the recycling of limiting nutrients between decaying plant material (litter) and live plants is delayed, this could also cause a population to oscillate.Wild rice is an interesting wetland plant species whose populations have long been known to oscillate. Wild rice is an annual plant and so the population must meet all its nutrients requirements for growth from the release of nutrients in decaying litter from previous years. Almost all the nutrients wild rice needs for growth are taken up in a brief window in spring-early summer of the year. But litter from the previous year decomposes so slowly that it does not even begin to release nutrients until at least the end of summer or not even until the second year of decay. We hypothesize that this delay in the recycling of nutrients through decaying litter causes wild rice populations to oscillate.Besides being ecologically interesting, wild rice is an important staple food for members of Minnesota's Ojibway (Chippewa) tribe. Wild rice harvesting is a defining feature of Ojibway society. Ojibway culture includes legends of wild rice spiritual ceremonies conducted during harvest time. Wild rice approaches sacred food status and band members identify wild rice as a symbol of what it means to be Ojibway. The Ojibway tribe manages over a dozen wild rice lakes in northeastern Minnesota for wild rice production in as natural a manner as possible. Therefore, what causes oscillations in wild rice production is of interest, culturally and scientifically, to tribal members as well as to a wider scientific community. This research will involve close collaboration with members of the Fond du Lac band of Ojibway.The effect of delays in nutrient release on wild rice population dynamics will be tested by the following three-pronged approach: (1) making long-term observations of wild rice productivity, seed production, and nutrient availability in sediments in a series of wild rice lakes; (2) manipulating litter, nutrient inputs, and seed vs. seedling establishment in large mesocosms (stock tanks) and measuring total productivity and nutrient uptake, mean plant weight and nutrient uptake, seedling emergence, and nutrient availability; and (3) constructing and testing a computer model of wild rice nutrient uptake, productivity, litter decay, and seed production and emergence.Students will be recruited from the tribal community college to assist in this work. This project will assist tribal biologists in addressing problems of natural resource management of significance to Ojibway values and show tribal students the potentials of a career in the environmental sciences. The tribe is anticipating that the results of this study will provide critical information for its development of nutrient criteria specifically for wild rice waters, and for improving management decisions from a better understanding of nutrient cycling in wild rice ecosystems.

在自然界中，动植物种群通常会经历有规律的振荡或盛衰周期。长期以来，生态学家一直对这些振荡的原因感兴趣。生态学理论预测，种群中的任何延迟都会导致它的振荡。大多数被认为是延迟原因的过程都是纯粹的人口过程，例如出生率的延迟。但是，如果腐烂的植物材料（枯枝落叶）和活植物之间的限制性营养物质的循环被延迟，这也可能导致种群振荡。野生稻是一种有趣的湿地植物物种，其种群长期以来一直被认为是振荡的。野生稻是一年生植物，因此种群必须从前几年腐烂的枯枝落叶中释放的营养物质中满足其生长所需的所有营养。几乎所有野生稻生长所需的营养都在一年中的春天初夏的短暂窗口中被吸收。但是前一年的垃圾分解得很慢，至少要到夏末，甚至要到腐烂的第二年，它才开始释放养分。我们假设，这种延迟通过腐烂的垃圾营养物质的循环导致野生稻种群振荡。除了生态上有趣，野生稻是明尼苏达州的Ojibway（齐佩瓦）部落成员的重要主食。野生稻收割是Ojibway社会的一个典型特征。Ojibway文化包括在收获季节进行的野生稻精神仪式的传说。野生稻接近神圣的食物地位，乐队成员认为野生稻是Ojibway的象征。Ojibway部落在明尼苏达州东北部管理着十几个野生稻湖，以尽可能自然的方式生产野生稻。因此，造成野生稻产量波动的原因是部落成员和更广泛的科学界在文化和科学上感兴趣的。这项研究将与Ojibway的丰迪拉克带的成员密切合作。营养释放延迟对野生稻种群动态的影响将通过以下三方面的方法进行测试：（1）对一系列野生稻湖泊的野生稻生产力，种子生产和沉积物中营养物质的有效性进行长期观察;（2）在大型围隔生态系统中操纵凋落物、养分输入以及种子与幼苗的建立（储罐）和测量总生产力和养分吸收、平均植物重量和养分吸收、出苗和养分可用性;（3）建立并测试野生稻养分吸收、生产力、凋落物腐烂、种子生产和出苗的计算机模型，将从部落社区学院招募学生协助这项工作。该项目将协助部落生物学家解决对Ojibway价值观具有重要意义的自然资源管理问题，并向部落学生展示环境科学职业的潜力。该部落预计，这项研究的结果将提供关键信息，其营养标准的发展，特别是野生稻沃茨，并改善管理决策，从更好地了解营养循环野生稻生态系统。