Specific Leaf Area: BioCON : Biodiversity, Elevated CO2, and N Enrichment

BioCON (Biodiversity, CO2, and Nitrogen) is an ecological experiment started in 1997 at the University of Minnesota's Cedar Creek Ecosystem Science Reserve. BioCON's goal is to explore the ways in which plant communities will respond to three environmental changes that are known to be occurring on a global scale: increasing nitrogen deposition, increasing atmospheric CO2, and decreasing biodiversity. Why Biodiversity, CO2, and Nitrogen? While there are many uncertainties in global change biology, there are also some well documented facts. Some of these are: 1. The amount of carbon dioxide (CO2) in the atmosphere is rising. Since the industrial revolution, the CO2 concentration in the atmosphere has increased from approximately 275 parts per million (ppm) to about 378 ppm today. This has been largely the result of fossil fuel burning. It is expected that CO2 levels will continue to rise, and that by the year 2050 these levels will be approximately 550 ppm. CO2 is the raw material for photosynthesis and is known to affect plant growth and development. 2. The amount of nitrogen moving through terrestrial ecosystems has increased in the recent past. While natural "background" levels of nitrogen fixation have remained constant, human additions to the system through fertilizer production and fossil fuel use have increased dramatically. Nitrogen is a key nutrient for plant growth and plays a critical role in plant community structure and composition in many environments. 3. Biodiversity levels are falling. While the research and data are not as complete as they are for CO2 and nitrogen, data indicate that the number of species globally, is being reduced. Perhaps more important for ecosystem function, diversity levels on local to regional scales have fallen due to land use change, biotic invasion and many other drivers. While much is known about how each of these factors affects ecosystem functioning, many questions remain. There is also little data on how these issues affect each other, and what emergent qualities may arise when systems are exposed to these changes simultaneously. BioCON seeks to address these issues with this multi-year study at Cedar Creek Ecosytem Science Preserve.BioCON（全称为Biodiversity, CO₂, and Nitrogen，即生物多样性、二氧化碳与氮素实验）是1997年于明尼苏达大学雪松溪生态系统科学保护区启动的一项生态学野外实验。该实验的核心目标为探究植物群落对三种已被证实的全球性环境变化的响应机制：日益加剧的氮沉降、升高的大气二氧化碳浓度，以及持续衰减的生物多样性。 为何选取生物多样性、二氧化碳与氮素作为研究对象？ 尽管全球变化生物学领域尚存诸多未解的不确定性，但也存在不少已被充分验证的科学事实，具体如下： 1. 大气二氧化碳（carbon dioxide, CO₂）浓度持续攀升。自工业革命以来，大气CO₂浓度已从约275ppm（百万分比浓度，parts per million）升至当前的约378ppm，这一变化主要源于化石燃料燃烧。据预测，CO₂浓度仍将持续上升，到2050年或将达到约550ppm。CO₂是光合作用的核心原料，已知其会对植物的生长与发育产生显著影响。 2. 近数十年来，流经陆地生态系统的氮素总量不断增加。尽管自然状态下的“本底”固氮水平保持稳定，但人类通过化肥生产与化石燃料使用向生态系统输入的氮素已出现大幅增长。氮素是植物生长的关键营养元素，在多数生境中对植物群落的结构与组成均起到决定性作用。 3. 全球生物多样性水平持续下降。尽管相关研究与数据尚未达到CO₂和氮素研究的完备程度，但现有数据表明全球物种数量正在减少。而对生态系统功能而言或许更为关键的是，由于土地利用变化、生物入侵及其他诸多驱动因素，局地至区域尺度的生物多样性水平已出现明显下滑。 尽管学界对上述各因素如何单独影响生态系统功能已有较多认知，但仍有大量核心问题有待解答。同时，关于这些因素之间的交互影响，以及生态系统同时暴露于这些环境变化时可能产生的涌现特性（emergent qualities），目前相关数据仍较为匮乏。BioCON项目旨在通过这项在雪松溪生态系统科学保护区开展的多年期野外研究，对上述问题展开系统性探索。