Chapter 21: Ecosystems of Théxar

"The Great Harmony is not a metaphor. It is an accurate description of how life is arranged. Every leaf, every beast, every microbe is part of a pattern that existed before us and will exist after." — From the treatise "Principles of Unity," Archive of the First Library

Related sections: → see [Ch.11, "Ecology"], → see [Ch.17, "Flora"], → see [Ch.18, "Fauna"] Key principle: Théxar demonstrates 10 major biomes, from equatorial jungles to polar deserts. The key difference is the sulfur cycle, linking geological, biological, and atmospheric processes into a single system.

Introduction

Théxar's ecosystems are the product of 4 billion cycles of evolution under an orange star, active tectonics, and a sulfur-rich biosphere. The fundamental difference of Théxar's ecosystems is the presence of a sulfur cycle (H₂S), parallel to the carbon cycle and playing a dominant role in a number of biomes.

Théxar has formed 10 major terrestrial biomes, 5 marine, and 3 unique ecosystems (hydrothermal vents, cave systems, subglacial lakes) without direct analogs.

21.1 Ecosystem Classification

21.1.1 Major Biomes

TABLE 21.1: Biomes of Théxar

Biome	Productivity (t C/ha/yr)	Biomass (Gt C)	Endemism
Moist jungles	18–22	820	35%
Savannas	8–12	380	18%
Temperate forests	10–14	580	24%
Taiga	4–6	210	28%
Deserts	0.5–1.5	12	42%
Steppes/grasslands	6–10	95	15%
Tundra	1–2	22	30%
Glaciers	<0.1	0.1	—
Anthropogenic	—	—	—
Mangroves	8–12	48	45%
Inland waters	4–8	35	52%

21.1.2 Sulfur Cycle

The sulfur cycle is the key difference of Théxar's ecosystems; on Théxar, sulfur is a full-fledged analog of nitrogen in biogeochemical cycles.

Fig. 21.1. Sulfur cycle of Théxar.

21.2 Trophic Levels

21.2.1 Producers

Primary production of Théxar's ecosystems is estimated at ~120 Gt C/year. The reason for high productivity is more efficient photosynthesis (4.2%).

21.2.2 Food Chains

Grazing chain (Kharak savannas):

Detrital chain (Vexar forests):

21.3 Unique Ecosystems

21.3.1 Equatorial Jungles

Théxar's jungles are the most productive terrestrial biome. Located in the equatorial belt (0°–8° latitude) in southern Kharak and northern Rhuval.

Structure:

Characteristic adaptation — H₂S air-filtration: leaves of lower layers have stomata capable of absorbing H₂S directly from the air and using it in metabolism (compensation for low light).

21.3.2 Cave Ecosystems

Théxar's karst systems (especially on the Raal plateau, Rhuval) form the largest underground ecosystems on the planet. Total explored cave length — ~69,100 мо.

Cave ecosystems have been isolated from the surface for millions of cycles. Some species show complete loss of vision and pigmentation, replaced by developed electroreception and chemosensitivity.

21.3.3 Hydrothermal Oases

At least 12 hydrothermal vent fields have been discovered on the floor of Théxar's oceans. The largest:

These ecosystems are living fossils, preserving the metabolic pathways of ancient Théxar.

21.3.4 Mangrove Forests

Théxar's mangrove ecosystems are distributed along the coasts of all three continents. Their key difference is silicon biomineralization of roots, allowing trees to grow in water with a high concentration of dissolved H₂S (up to 2.5× lethal for ordinary plants).

21.4 Seasonal Dynamics

21.4.1 Seasons on Théxar

Due to the small axial tilt (14.2°), seasonal changes are less pronounced:

21.4.2 Migrations

The Great Migration of Ghal-Shar — the largest seasonal animal movement on the planet. Twice a year, herds totaling 2–4 million individuals cross the Central Plain of Kharak, following the seasonal rains.

21.5 Invasive Species

With the development of intercontinental trade and transport, some species spread beyond their natural ranges:

Chapter Summary

Key conclusions:

1. Théxar has 10 terrestrial and 5 marine biomes with a total primary production of ~120 Gt C/year.
2. The sulfur cycle is the key difference of Théxar's ecosystems; H₂S participates in metabolism on par with carbon.
3. Endemism is highest in deserts (42%), mangroves (45%), and inland waters (52%).
4. Cave ecosystems — the largest underground biomes on the planet (33 thous. мо², 95% endemism).
5. Equatorial jungles are five-layered, with H₂S air-filtration in lower layers.
6. Great Migration of Ghal-Shar — up to 4 million individuals, 305 мо, twice a year.

Connections to other chapters:

• → see [Ch.11, "Ecology"] — overview ecology
• → see [Ch.17, "Flora"] — vegetation by biome
• → see [Ch.18, "Fauna"] — animals by ecosystem
• → see [Ch.13, "Continents"] — biome distribution
• → see [Ch.14, "Oceans"] — marine ecosystems