EAGER: Does Na availability regulate tropical decomposers?

地球的大部分碳循环可以这样简单地描述：植物从大气中清除二氧化碳；动物、真菌和细菌消耗植物并将二氧化碳释放回大气。这项提议认为，钠(食盐中的钠)在调节大气二氧化碳方面扮演着一个关键的、被低估的角色。大多数植物不需要钠，但分解动物和真菌需要(在低钠生态系统中受苦，就像运动队没有佳得乐一样)。因此，低钠生态系统应该倾向于储存碳。内陆越远的生态系统在其降雨中接收的海洋来源的钠越来越少。因此，地球广袤内陆的分解者应该特别缺乏钠，不那么活跃，也不太可能向大气中释放碳。我们将通过两种方式检验这一假设。首先，在三个月内，厄瓜多尔内陆2500公里的一片5x5米的森林将接受两种治疗之一。其中一半将定期从附近的一条河流中浇水。另一半将获得含有氯化钠的河水(大约相当于一年沿海降雨量)。这项实验将测试是否有更多的森林树叶和木质凋落物在添加钠的情况下分解。其次，小规模实验将比较两种森林的生态系统响应在地理上的差异：一种是我们在厄瓜多尔的地点，另一种是距离海洋只有25公里的巴拿马。一种常见的钠补充剂-尿液-将成为实验的重点。四种治疗方法--合成尿液、不含氯化钠、氯化钠和水的尿液--将被添加到小片森林中，为期三周。如果上述假设属实，那么尿液中的氯化钠成分应该会增加厄瓜多尔森林中的分解程度。这两个实验都将监测食物链上的钠对分解节肢动物及其捕食者的影响，这些节肢动物约占热带森林生物多样性的一半。地球上的大多数陆地生态系统距离海洋足够远，可以经历钠的限制。因此，由这项提议资助的工作有可能显著增加对地球气候系统的了解。如果像目前的模型预测的那样，降雨量和分布随着全球变暖而改变，这可能意味着钠沉积的变化，这反过来可能会增加或减少大气中的二氧化碳。这项研究的生物多样性部分将收集世界上这一鲜为人知的地区的数千个标本(几乎可以肯定，还有尚未描述的物种)。研究生将接受将地球科学、进化生物学和生态系统生态学联系起来的多学科努力的培训。她将指导俄克拉荷马大学的一名本科生，这名本科生将加入我们的实地考察，亲身体验生物多样性科学。

Much of Earth's carbon cycle can be described briefly thus: plants scrub carbon dioxide from the atmosphere; animals, fungi, and bacteria consume plants and release carbon dioxide back into the atmosphere. This proposal posits that sodium (the Na in NaCl, or table salt) plays a key, under-appreciated role in regulating atmospheric carbon dioxide. Most plants don't need sodium, but decomposer animals and fungi do (and suffer in low-sodium ecosystems like a sports team deprived of Gatorade). Low-sodium ecosystems should thus tend to store carbon. Ecosystems farther inland receive less and less ocean source sodium in their rainfall. Decomposers of earth's vast continental interior should thus be especially sodium deprived, less active, and less likely to release carbon back into the atmosphere. We will test this hypothesis in two ways. First, for three months, 5 x 5 m patches in an Ecuador forest 2500 km inland will receive one of two treatments. Half will be regularly watered from a nearby river. The other half will get river water charged with NaCl (about the amount found in a year's worth of coastal rainfall). This experiment will test if more of a forest's leaf and woody litter decomposes with added sodium. Second, small-scale experiments will compare how ecosystem responses vary geographically between two forests: one, our site in Ecuador, the other in Panama, only 25 km from the ocean. A common sodium supplement-urine-will be the experimental focus. Four treatments--synthetic urine, urine sans NaCl, NaCl, and water--will be added to small patches of forest for three weeks. If the above hypothesis is true, the NaCl component of urine should increase decomposition more in the Ecuador forest. Both experiments will monitor sodium effects up the food web on decomposer arthropods and their predators, which comprise about half the biodiversity in a tropical forest.Most of Earth's terrestrial ecosystems are far enough from the ocean to experience sodium limitation. The work funded by this proposal thus has the potential to significantly increase understanding of the Earth's climate system. If the amount and distribution of rainfall changes with global warming, as predicted by current models, this may mean changes in sodium deposition, which in turn could increase or decrease atmospheric carbon dioxide. The biodiversity part of this study will collect thousands of specimens (and, almost certainly, species not yet described) in this poorly understood part of the world. A graduate student will be trained in a multidisciplinary endeavor linking earth science, evolutionary biology, and ecosystem ecology. She in turn will mentor an undergraduate from the University of Oklahoma, who will join us in the field and experience biodiversity science first hand.