Ch 14: Ecosystem

Explains biotic-abiotic interactions, vertical stratification, and functional components. Crucial for understanding spatial niche distribution of flora and fauna in tropical vs temperate forests. UPSC tests terms like standing crop and standing state here. Trap: Confusing standing crop (living biomass) with standing state (inorganic nutrients like Nitrogen and Phosphorus in soil).

Details Gross Primary Productivity (GPP), Net Primary Productivity (NPP), and Secondary Productivity. Must memorize the core equation: NPP = GPP - R. Highlights that biosphere annual NPP is 170 billion tons, but oceans contribute only 55 billion tons despite covering 70% of Earth. Trap: Assuming open oceans have higher per-unit-area productivity than tropical rain forests.

Breaks down fragmentation, leaching, catabolism, humification, and mineralization. Essential to learn chemical and climatic controls of decomposition. Warm, moist, nitrogen-rich environments accelerate it, while anaerobiosis and lignin-rich materials slow it. Frequently linked with conservation agricultural practices like zero tillage. Trap: Assuming low temperature accelerates decomposition due to microbe preservation.

Explains photosynthetically active radiation (PAR < 50%), 10% energy transfer rule, Grazing (GFC) vs Detritus (DFC) food chains, and ecological pyramids. Energy pyramids are strictly upright. Biomass pyramids in deep aquatic systems are often inverted. Trap: Believing energy pyramids can ever be inverted under any ecosystem anomalies.

Analyzes primary (thousands of years on bare rocks/lava) vs secondary succession (rapid, on abandoned fields/burned forests). Understand hydrarch and xerarch pathways, pioneer species (lichens, phytoplankton), and climax community. Trap: Believing hydrarch and xerarch successions culminate in different moisture regimes; both actually lead to a mesic climax.

Compares gaseous (carbon, nitrogen) vs sedimentary (phosphorus, sulfur) cycles. Explains soil weathering as the primary release mechanism for sedimentary nutrients. UPSC tests the absence of respiratory release in the phosphorus cycle compared to the carbon cycle. Trap: Misidentifying phosphorus as a gaseous biogeochemical cycle.

Features Robert Costanza's valuation of global ecosystem services ($33 trillion/year). Focus on the percentage allocation: soil formation takes 50%, while climate regulation and habitat are 10% each. Safe to skim general details, but memorize the specific valuation ratios for analytical prelims statements.