Collaborative Proposal - Quantifying the footprint of a dominant organism: Biogeochemical impacts of leaf cutter ants in a lowland tropical forest ecosystem

合作提案 - 量化优势生物的足迹：低地热带森林生态系统中切叶蚁的生物地球化学影响

• 批准号: 1442568
• 负责人: Thomas Harmon
• 金额: $ 13.77万
• 依托单位: University of California - Merced
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-06-01 至 2019-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1442568&HistoricalAwards=false
• 关键词: Collaborative; Proposal; Quantifying; footprint; dominant

This project will provide information on the contribution of an ecologically important ant guild to the carbon cycle and will help improve predictions of future carbon dynamics in tropical forests. One of the most conspicuous features of a tropical forest is the abundance of leaf cutter ants. Despite their prominence, little is known about the overall contribution of leaf cutter ants to carbon and nutrient cycles in tropical ecosystems. These tropical and subtropical forested ecosystems cover 17% of the Earth's land mass and store approximately 40% of all carbon and are an important determinant of the global carbon cycle. Leaf cutters are the dominant herbivores in tropical forest ecosystems, bringing 10-50 % of all surrounding vegetation into the nest, fertilizing nest soils, and promoting the release of carbon dioxide and methane into the atmosphere. The network of leafcutter ant trails extend throughout the forest and workers walk single-file, carrying pieces of leaves into their nests, where special fungi break down the plant material and produce hyphae, on which the ants feed. Leaf cutter ant nests are massive in size and during nest construction and maintenance ants mix leaf particles into the soil and alter soil chemistry. Leaf cutter ant activities have the possibility of controlling aspects of ecosystem dynamics, though the degree of their influence has not been quantified. The project will focus on the role of leafcutter ant nests as hotspots of carbon dioxide and methane emissions and the role of nests in altering soil chemistry and creating heterogeneity in carbon (C), nitrogen (N), and phosphorus (P) in the soil across the landscape. The work will be conducted at La Selva Biological Research Station, Costa Rica, which is an epicenter of tropical scientific research, hosting a large number of student groups, researchers from all over the world. The project will characterize C dynamics on leafcutter ant nests and differentiate the sources of carbon dioxide and methane emissions between the activities of ants, fungi, the nest microbial community, and roots and hyphae. The N, and P biogeochemistry of active leafcutter ant nests will be quantified as well as the soil legacy effects after nests are abandoned. The project uses a multi-faceted approach, including coupling continuous measurements of soil carbon dioxide emissions with discrete measures of methane efflux, stable C isotopes of carbon dioxide to determine sources, soil C and N pools and fluxes, estimates of root and fungal biomass, and microbial community and functional indices. Measurements will be performed on ant nests, paired non-nest sites, and along a sequence of nests abandoned at different times in the past to quantify how long the impact of altered biogeochemistry persists in areas occupied by nests. These biogeochemical fluxes will be incorporated into an ecosystem model to estimate C flux at local-to-regional scales. The project will strengthen international collaborations by working with researchers and students from the US, Costa Rica, and New Zealand. In addition to training a postdoctoral researcher and mentoring several REU students, project scientists will conduct an annual workshop to introduce students and researchers to cutting edge field instrumentation and analysis techniques and provide opportunities to use these new approaches at La Selva. La Selva Biological Research Station is an epicenter of tropical scientific research, hosting a large number of student groups, researchers from all over the world, and serving as a center for ecotourism, thus the proposed research will be widely disseminated.

该项目将提供关于具有重要生态意义的蚂蚁行会对碳循环的贡献的信息，并将有助于改进对热带森林未来碳动态的预测。 热带森林最显著的特征之一是大量的切叶蚁。尽管他们的突出，很少有人知道切叶蚁的碳和营养循环在热带生态系统的整体贡献。这些热带和亚热带森林生态系统覆盖了地球陆地面积的17%，储存了大约40%的碳，是全球碳循环的重要决定因素。切叶蚁是热带森林生态系统中占主导地位的食草动物，将周围所有植被的10- 50%带入巢穴，破坏土壤，并促进二氧化碳和甲烷释放到大气中。切叶蚁的足迹网络遍布整个森林，工人们排成一列，把一片片的树叶搬进巢穴，在那里，特殊的真菌分解植物材料，产生菌丝，蚂蚁以菌丝为食。切叶蚁的巢穴是巨大的，在筑巢和维护过程中，蚂蚁将树叶颗粒混合到土壤中，改变土壤的化学性质。切叶蚁活动有可能控制生态系统动态的各个方面，尽管其影响程度尚未量化。该项目将重点关注切叶蚁巢穴作为二氧化碳和甲烷排放热点的作用，以及巢穴在改变土壤化学和在整个景观的土壤中创造碳（C），氮（N）和磷（P）异质性方面的作用。这项工作将在哥斯达黎加的拉塞尔瓦生物研究站进行，该研究站是热带科学研究的中心，接待了来自世界各地的大量学生团体和研究人员。 该项目将描述切叶蚁巢穴的碳动力学特征，并区分蚂蚁，真菌，巢穴微生物群落以及根和菌丝活动之间的二氧化碳和甲烷排放源。将量化活跃的切叶蚁巢的N和P的地球化学以及巢被遗弃后的土壤遗留效应。该项目采用多方面的方法，包括将土壤二氧化碳排放量的连续测量与甲烷排放量的离散测量相结合，二氧化碳的稳定碳同位素，以确定来源，土壤C和N库和通量，根和真菌生物量的估计，以及微生物群落和功能指数。将对蚁巢、成对的非蚁巢地点以及沿着过去不同时间遗弃的一系列蚁巢进行测量，以量化改变的地球化学影响在蚁巢占据的地区持续多久。这些碳地球化学通量将被纳入生态系统模型，以估计在本地到区域尺度的碳通量。该项目将通过与来自美国、哥斯达黎加和新西兰的研究人员和学生合作来加强国际合作。除了培训博士后研究员和指导几个REU学生，项目科学家将举办年度研讨会，向学生和研究人员介绍尖端的现场仪器和分析技术，并提供机会在拉塞尔瓦使用这些新方法。拉塞尔瓦生物研究站是热带科学研究的中心，接待了来自世界各地的大量学生团体和研究人员，并作为生态旅游中心，因此拟议的研究将得到广泛传播。