Plant species percent cover data: 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.

生物多样性、二氧化碳与氮素实验（BioCON，Biodiversity, CO2, and Nitrogen）是一项于1997年在明尼苏达大学雪松溪生态系统科学保护区启动的生态实验。该实验旨在探究植物群落对三种已在全球范围内发生的环境变化的响应机制，分别为氮沉降增加、大气二氧化碳浓度升高以及生物多样性丧失。

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不确定性，但也存在一些已被充分证实的科学事实，具体如下：
1. 大气中二氧化碳（CO₂）浓度持续上升。自工业革命以来，大气CO₂浓度已从约275百万分比浓度（parts per million，ppm）升至当前的约378ppm，这一变化主要源于化石燃料燃烧。预计到2050年，CO₂浓度将进一步攀升至约550ppm。CO₂是光合作用的原料，已知其会对植物的生长与发育产生影响。
2. 近年来，陆地生态系统中的氮素通量有所增加。尽管自然背景下的固氮作用水平保持稳定，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大幅增长。氮素是植物生长的关键营养元素，在诸多环境中对植物群落结构与组成发挥着至关重要的作用。
3. 生物多样性水平正在下降。尽管相关研究与数据不如CO₂和氮素研究那般完备，但现有数据表明全球物种数量正持续减少。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下降。

尽管学界对各单一因素如何影响生态系统功能已有诸多认知，但仍存在大量待解问题。此外，关于这些因素之间如何相互影响，以及生态系统同时暴露于这些变化时可能产生的涌现特性，相关数据仍十分匮乏。BioCON旨在通过在雪松溪生态系统科学保护区开展的多年期研究，解决上述问题。