Tank Bromeliads as a Water Reservoir Used by Humans: An Important Overlooked Ecosystem Service in Xerophytic Forests

The Bromeliaceae are known for providing numerous ecosystem services. Tank bromeliads that collect water in the bases of their leaves have been an important source of water for people in semiarid regions such as the Gran Chaco. In this large area characterized by xerophytic vegetation grows Aechmea distichantha, the only Chaquenian terrestrial tank bromeliad. We carried out a literature review on water consumption from this tank bromeliad by people in this region. Then, we analyzed the variations in the amount of water stored in the tanks of plants from observational studies as well as the effects of the amount and frequency of water addition on the hydrology of water retained in the tank from an irrigation experiment study. We found 85 reports on the consumption of water from A. distichantha plants by people, including several Indigenous Groups, Criollos, and Soldiers. According to these reports, the tank accumulates about a liter of relatively fresh and clear water that lasts for several weeks. Our observational study showed a large variation in the amount of water held in the tank among years and sites, and our irrigation experiment showed that even plants receiving low and unevenly distributed rainfall conserved some water in their tanks. All these results support the importance of this tank bromeliad for surviving when moving in Eastern Chaco during dry periods until the beginning of the twentieth century. At present, it seems that people living in sedentarism no longer frequently use it for water provision, highlighting that the relative importance of a plant species for providing ecosystem services depends on the historical context.