Atym Flooded Grassland

Place

Place Name:

Atym Flooded Grassland

Biome:

Flooded Grassland

Size:

Unknown

Continent:

Unknown

Subcontinent

Unknown

Geography

The Atym Flooded Grassland is a massive, lowland alluvial plain, lying in one of the largest drainage systems on the Twilight Age world. In contrast to the fire-scorched desiccated plains of Anigar or the stark, brittle peaks of Asat, Atym is an ecosystem defined almost entirely by water, a constantly shifting hydrological realm. A mind-boggling landscape of braided river channels, ephemeral inland seas, and vast marshy lands, the boundary between soil and open water shifts continuously.

Topography and Geology

Topographically, the basin itself was formed over millions of years of silt and mud deposition from distal mountain watersheds. Being almost perfectly flat, slight variations of a few centimeters will forever doom a section of terrain to either year-round submersion or seasonable inundation; others will remain perpetually dry. The effect is a landscape of bewildering, water-cut topology, featuring a complex network of meandering distributary channels, natural levees, and higher islands of more cohesive soil.

Geologically, the region consists of loose alluvial material, high concentrations of clays, and vast deposits of organic matter and humus. Each seasonal flood buries the basin floor under fresh, hyper-fertile silt. Ancient river courses remain in the landscape in the form of paleochannels, sinuous ridges of sediment, and crescent-shaped oxbow lakes formed when an aggressive current finally cuts straight, leaving its old bed to dry and wither.

Climate and Hydrography

Hydrologically, the Atym is governed by a dramatic, seasonally exaggerated flood pulse. Fueled by melting snows from upstream and tropical wet season storms, the numerous large braided river channels will overflow, and hundreds of square miles of grassland will become a single, slow moving, inundable inland sea. The climate is intensely hot and hyper-humid. The massive amount of water at the surface helps retain heat, and morning fogs are common and thick. Storms are the most significant feature of the wet season.

Along with raising the water level rapidly, they also actively sculpt the terrain by cutting new river channels and depositing immense amounts of sediment. As the rains subside, the receding floodwaters become excruciatingly slow, leaving behind miles of mudflats and igniting rapid regrowth of grassland plains.

Traversability

Despite the seeming flatness of the open grasslands of the Atym, it is virtually impossible to travel through. The landscape deceives the observer; a firm grassland in the dry season will become an utterly submerged marsh weeks later. Treacherous mudflats are hidden beneath what appear to be solid earth, channels are deep and sudden, and travel may be impeded by a slowly growing inland sea. Instead, travelers are forced to pick their way along pre-existing natural river levees and ridges of ancient sediment-the only dry, precarious highways on the entire plain.

Plants

Floodplain Flora (Seasonal Graminoids and Inundation Ecology)

The flora of the Atym Flooded Grassland can be described as a miracle of aquatic endurance and vegetative explosion. Unlike the burned landscapes of Anigar or the sluggish growth of Asat's alpine scrub, Atym's flora only truly blossoms when fully submerged or when it is fed a fresh infusion of fertile alluvium. Vast quantities of flood-tolerant graminoids (grasses) exist on a predictable, enormous-scale boom-bust cycle. Submerged for many months of the year, these grasses maintain an enormous network of interlocking rhizomes.

When the inland sea washes over the land, its vegetation dies off on the surface but its underground root-mass lies dormant. With the receding waters, and the nutrient-rich mudflats are scorched dry, an immediate and spectacular biotic boom follows. Within a few short weeks, fertile silt gives way to an ocean of towering grass whose boundaries ebb and flow with each season.

Wetland Flora (Macrophytes and Floating Islands)

The deep oxbow lakes and permanently boggy regions host truly dense ecosystems of vegetation. Due to the strict anearobic nature of decomposing mud, the roots of these reeds, sedges, and flowers rely on specialized porous tissues called aerenchyma, to pump atmospheric oxygen from above down into the stifled root systems. The slow-moving, marshy backwaters are occupied by colonies of large floating macrophytes which interlock their buoyant bodies forming immense vegetation mats.

These drifting, living islands capture floating sediments and dead organic material which gradually builds up layer upon layer creating floating mini-islands which drift across the basin, completely separate from the substratum below.

Levee and Riverbank Flora (Riparian Corridors)

Only on elevated river levees and riparian ridges can there be found much in the way of permanent terrestrial vegetation. These narrow strips of deposited sediment are occupied by flood-tolerant shrubs and uniquely adapted, deep-rooted trees which bind the soft clay banks in place with their complex root systems which prevent their own destruction by the turbulent, powerful flood currents at peak flow. The root-systems of these species are adapted to constant burial and constantly produce new adventitious roots at higher points on their trunks to prevent suffocation, forcing them to "grow" up the continually aggrading ground over centuries.

Seasonal Adaptations (The Flood Pulse and Vegetative Fragmentation)

Biological life in Atym can only develop on the "flood pulse"-there is no possible terrestrial permanance, and existence is characterized by hyper-flexibility and reproduction at any cost. Seeds of some species are dormant, buoyant, waterborne seed-banks buried under many feet of water that will only sprout once exposed to open air. Others utilize the destructive floodwaters for vegetative propagation, intentionally cleaving stems and rhizomes that will then travel miles downriver before rooting to reproduce clone populations far downstream. Ultimately the seasonal inundation of the landscape is not an obstacle but rather the fundamental force driving the ecosystem and its life-cycle.

Animals

Floodplain Fauna (Alluvial Plains and Semi-Aquatic Species)

Life here is totally attuned to the powerful, pulsating heartbeat of the inland sea. Unbound by the altitude-locked migration routes of Asat, or the fire-chasing herds of Anigar, Atym is a world where the ground under foot is never fixed. This ecosystem teems with vast herds of nomadic grazers, semi-aquatic scavengers, and highly motile predators adept at a complex, fluid world of water and mud. Navigating the shifting alluvial silt without drowning or succumbing to the deep mud is managed by plains-dwelling ungulates by the use of specialized adaptations, elongated limbs and splayed, widespread hooves acting as terrestrial snowshoes over the thick mud.

The intense sun beating down on the baked mudflats after the floodwaters painfully retreat sparks colossal, region-wide grazing migrations, due to a phenomenal upsurge in fresh vegetation growth. Because there are almost no permanent cover areas, the predators in this zone are equally nomadic and essentially mobile tracking units, trailing the herds along the constantly changing boundaries of the waterline.

Wetland Fauna (Marsh and Benthic Species)

The largest concentrations of life are found in the deep oxbow lakes, the permanent marshes, and inundated depressions, which sustain a fiercely competitive world of amphibious herbivores, benthic invertebrates, filter feeders and aquatic predators who wait in ambush. The complex, water-logged reeds necessitate specialized morphology- hydrophobous pelage, splayed, webbed digits, laterally compressed tails for propulsion and sealable nostrils and ear apertures.

These tall, intricate reed complexes serve as essential nursery grounds, shielding young animals from enormous predators while providing homes to enormous insect colonies. On the muddy bottom, the vast decomposer communities vigorously process the detritus flushed out by the annual floodwaters, completely recycling dead organic matter.

River Fauna (Channel and Pelagic Species)

The wide, braided river channels serve as biologic superhighways through the floodplain. These deep-water artery systems support massive pelagic river species and aquatic apex predators who are adapted to surviving the fast, overwhelming currents. Lateral movement dominates river ecology in Atym. In the wet season, when floods violently over-top the channels, aquatic life spreads out across hundreds of miles into the submerged grasslands to feed and breed.

When dry season descends, millions of aquatic life forms are forceably funneled back into the main river channels; this catastrophic event causes intense predatory bottlenecks at every river intersection, where aquatic hunters are drawn by the colossal densities of migrating prey, and gorge to bursting.

Behavioral Cycles (The Flood Pulse and Ephemeral Refugia)

The life of Atym is completely tied to the immense expansion and contraction of the "flood pulse." The rising floodwater initiates a simultaneous dual migration. As the water rises, terrestrial creatures are ruthlessly driven to the small, elevated levees and silt islands to serve as temporary, desperately needed micro-refugia from drowning. Simultaneously, the aquatic communities spill over the edge of their channels and flood the plains. When the floodwater recedes, the reverse process is incredibly swift. Vast quantities of fish, amphibian and invertebrates are stranded by the vanishing floodwaters into transient pools of water.

These dying pools become feeding hotspots for the entire ecosystem, drawing vast number of predators and scavengers of all types to feast upon their struggling aquatic prey. Consequently, survival at Atym requires extraordinary motility; a world in which all life races against the sinking earth, only to be forced into battle against the returning waters in an unending cycle of deluge and drying.

Historical Timeline of Ages

Age Name	Dates	Controller
Stone Age	Before 1E 0	Unknown
Copper Age	1E 1–1E 2200	Unknown
Bronze Age	1E 2200–1E 4400	Unknown
Iron Age	2E 0–2E 700	Unknown
Ancient Age	2E 700–2E 2200	Unknown
Middle Age	3E 0–3E 2050	Unknown
Early Modern Age	3E 2050–3E 2600	Unknown
Industrial Age	3E 2600–3E 2700	Unknown
Machine Age	3E 2700–3E 2800	Unknown
Atomic Age	3E 2800–3E 2850	Unknown
Space Age	3E 2850–3E 2875	Unknown
Information Age	3E 2875–3E 2900	Unknown
Genetic Age	3E 2950–3E 3000	Unknown
Awakening Age	3E 3000–3E 3415	Unknown
Twilight Age	4E 0–4E 500

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