EAGER: Does Na availability regulate tropical decomposers?

地球的碳循环可以简单地描述为：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中。这一提议假定钠（NaCl或食盐中的钠）在调节大气二氧化碳方面起着关键的、未被充分认识的作用。 大多数植物不需要钠，但分解动物和真菌需要（并在低钠生态系统中遭受损失，就像运动队失去佳得乐一样）。因此，低钠生态系统应该倾向于储存碳。更远的内陆生态系统在降雨中接受的海洋来源的钠越来越少。因此，地球广阔大陆内部的分解者应该特别缺乏钠，不太活跃，也不太可能将碳释放回大气。我们将从两个方面来检验这个假设。首先，在三个月内，厄瓜多尔内陆2500公里森林中的5 × 5米斑块将接受两种治疗之一。 其中一半将定期从附近的河流中取水。另一半将得到含有氯化钠的河水（大约是一年的沿海降雨量）。这个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后分解。第二，小规模实验将比较两个森林的生态系统反应在地理上的差异：一个是我们在厄瓜多尔的站点，另一个是巴拿马，距离海洋只有25公里。一种常见的钠排泄物-尿-将是实验的重点。四种处理方法--合成尿液、无氯化钠尿液、氯化钠尿液和水--将被添加到小块森林中三周。如果上述假设是真的，尿液中的氯化钠成分应该会增加厄瓜多尔森林中的分解。这两项实验都将监测钠对分解节肢动物及其捕食者的食物网的影响，这些节肢动物占热带森林生物多样性的一半左右。地球上大多数陆地生态系统距离海洋足够远，都受到钠的限制。因此，这项提案资助的工作有可能大大增加对地球气候系统的了解。如果降雨量和分布随着全球变暖而变化，正如目前的模型所预测的那样，这可能意味着钠沉积的变化，这反过来又可能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在世界上这一鲜为人知的地区收集数千个标本（几乎可以肯定，还有尚未描述的物种）。一个研究生将在一个多学科的奋进连接地球科学，进化生物学和生态系统生态学的培训。反过来，她将指导一名来自俄克拉荷马州大学的本科生，他将加入我们的行列，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.