The intertidal mangrove ecotone is an extremely productive and highly important ecosystem. Ecotones, also known as the edge effect or tension zones, are biodiversity hotspots characterized by abrupt physical and biological transitions. They usually occur at many spatial and time scales, ranging from ecosystems to local microbial and molecular transactions. Therefore, mangroves respond to a broad number of environmental factors like salinity, temperature, and sea-level rise through feedback loops; they can expand, tolerate and build-up their environment while storing massive amounts of blue carbon. This research focuses on three energy axes that allow mangroves to expand beyond their historical range limits, expanding into upland zones, laterally along coasts, and rising upward against sea-level rise.
Although not competitive in freshwater, mangroves can move into freshwater tree habitats by increasing the soil salinity. When there’s little freshwater precipitation during the dry season, mangroves increase their plant water uptake from the vadose zone. The saline water will infiltrate and saturate the vadose zone with saltwater below. Mangrove uptake of water laterally from neighboring cells allows it to turn a freshwater tree’s cell, which is surrounded by mangrove cells, into its own. Upland trees also have a similar mechanism to decrease the salinity in neighboring cells in reverse logic.
This gamified simulation abstracts the dynamics between abiotic environmental changes. Soil salinity and the two plant’s energies help players better understand how two trees will eventually achieve resilient bistability through a positive feedback loop by clustering even in soil with no salinity gradient. Unlike how the player strategizes sectional tree’s pattern each turn in the gamified simulation, trees in mangrove/upland-tree ecotone self organize every individual tree into the most effective pattern to take full advantage of the abiotic change to move in.
The winter climate extremes limit mangrove’s global distribution, but their nursing mechanism keeps them resilient to the extremes. Mangroves drop seeds called propagules, which typically float on the water until they can take root in a new location. Sometimes they end up near the parent tree. Mangroves found in colder environments tend to grow shorter and denser than the average mangrove. This self-organized behavior helps them create a collective canopy that generates a warmer microclimate by trapping the thermal energy released from the ground at night. When the fully grown mangroves die off during winter, nocturnal warming continues protecting mangrove propagules from the deadly freezes. Just like how birds and fish take turns leading their school or flock, mangroves decentralize their members to take turns nursing and raising to increase their resilience to the freeze and movement laterally along the coast.
Mangroves are heavily involved in soil surface elevation processes which allow them to keep up with the local sea-level rise. During slack tide, mangrove roots, trunks, and actions caused by animals living in the mangrove structural ecosystem trap sediment and create turbulence to form sediment flocs in the water. The roots and trunks also help to bind the sediment into a solid-state. Microbes living in the built-up soil beneath the mangroves feed on litter mats made from fallen leaves and tree limbs. The bi-product of this process forms sticky benthic mats, where sediment gets caught on, leading to more soil accretion. Mangrove roots and trunks also increase soil’s shear strength, decrease tide’s hydraulic stress to prevent the ground from erosion, and increase soil volume through root growth.
Since the positive feedback loop of sediment accretion takes place over a long period, a rocking table was built to simulate this process. Closely placed wooden dowels represent the mangrove’s dense roots and trunks structure, while the moving fluid plaster caused by the rocking table mimics the ocean tides. Interesting typography started to form as each plaster layer goes through a turbulent flow, trickling through the roots and hardening. While more layers of plaster need to be applied to have a more noticeable result, the hypothesis is that the dowels that trap and bind relatively more plaster at the beginning will gain in volume faster than the others over time.
The mangrove uses self-organizational energy of distribution patterns to increase the soil's salinity to intrude into upland. Its decentralized community can create a positive feedback loop to gain resilience to winter freeze and move into regions where salt marshes typically replace mangroves. Its adaptiveness to sea level rise helps it move vertically while creating a structural biodiversity hotspot for many edge species. These are all subtle but effective energies that help mangroves take full advantage of the abiotic conditions to expand beyond their typical global limits. Understanding these complex systems' energies could lead to new ways of thinking and understanding the human-built environment and its connection with nature. Some correlation that can be drawn between a mangrove forest ecotone and the future city includes buildings and regions in between, webs of transportation, movement of material, the flexibility of structure following social space, urban heat islands, and site repair.