MANTRA-O18: An Extended Version of SUTRA Modified to Simulate Salt and δ¹⁸O Transport amid Water Uptake by Plants

¹ School of Mathematical Sciences, Universiti Sains Malaysia, Penang 11800, Malaysia
² U.S. Geological Survey, Wetland and Aquatic Research Center, Gainesville, FL, USA
³ U.S. Geological Survey, Menlo Park, CA, USA
⁴ Department of Biology, University of Miami, Coral Gables, FL, USA
⁵ Jeffrey Sachs Center on Sustainable Development, Sunway University, Jalan Universiti, Bandar Sunway, 47500 Selangor, Malaysia

Contact Information: Su Yean Teh, Universiti Sains Malaysia, School of Mathematical Sciences, 11800 USM, Pulau Pinang, Malaysia, Phone: 604-6534770, Fax: 604-6570910, Email: syteh@usm.my

Abstract

Sea level rise and the increasing landward intrusion of storm surges pose the threat of replacement of salinity-intolerant vegetation of important coastal habitats by salinity-tolerant vegetation. Therefore, a means is needed to better understand the processes that influence this vegetation shift and to aid in the management of coastal resources. For this purpose, a hydrology–salinity–vegetation model known as MANTRA was developed by coupling a spatially explicit model (MANHAM) for simulation of vegetation community dynamics along coastal salinity gradients with SUTRA, a USGS groundwater flow and transport model. MANTRA has been used to project possible future changes in Coot Bay Hammock in southern Florida under conditions of gradually rising sea level and storm surges. The simulation study concluded that feasibility exists of a regime shift from hardwood hammocks to mangroves subject to a few conditions, namely severe damage to the existing hammock after a storm surge and a sufficiently persistent high salinity condition and high input of mangrove seedlings. Early detection of salinity stress in vegetation may facilitate sustainable conservation measures being applied. It has been shown that the δ¹⁸O value of water in the xylem of trees can be used as a surrogate for salinity in the rooting zone of plants, which is difficult to measure directly. Hence, the model MANTRA is revised into MANTRA-O18 by including the δ¹⁸O of the tree xylem dynamics. A simulation study by MANTRA-O18 shows that effects of increasing salinization can be detected many years before the salinity-intolerant trees are threatened with replacement.