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Q90 (IAS/2021) Environment & Ecology › Ecology & Ecosystem Basics › Tropical rainforest ecology Official Key

“Leaf litter decomposes faster than in any other biome and as a result the soil surface is often almost bare. Apart from trees, the vegetation is largely composed of plant forms that reach up into the canopy vicariously, by climbing the trees or growing as epiphytes, rooted on the upper branches of trees.” This is the most likely description of

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Q. “Leaf litter decomposes faster than in any other biome and as a result the soil surface is often almost bare. Apart from trees, the veget…

At a glance

Origin: Mixed / unclear origin Fairness: Low / Borderline fairness Books / CA: 0/10 · 0/10

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This is a classic 'Sitter' found verbatim in standard texts like Majid Hussain and implied strongly in GC Leong. It tests the fundamental ecological mechanic of nutrient cycling: Heat + Moisture = Rapid Decomposition. If you missed this, you are skipping the conceptual basics of Biome Ecology.

How this question is built

This question can be broken into the following sub-statements. Tap a statement sentence to jump into its detailed analysis.

Statement 1: In the coniferous forest biome, does leaf litter decompose faster than in any other biome?
Statement 2: In the coniferous forest biome, is the soil surface often almost bare as a result of rapid leaf litter decomposition?
Statement 3: In the coniferous forest biome, is vegetation apart from trees largely composed of climbers and epiphytes rooted on upper branches?
Statement 4: In the dry deciduous forest biome, does leaf litter decompose faster than in any other biome?
Statement 5: In the dry deciduous forest biome, is the soil surface often almost bare as a result of rapid leaf litter decomposition?
Statement 6: In the dry deciduous forest biome, is vegetation apart from trees largely composed of climbers and epiphytes rooted on upper branches?
Statement 7: In the mangrove forest biome, does leaf litter decompose faster than in any other biome?
Statement 8: In the mangrove forest biome, is the soil surface often almost bare as a result of rapid leaf litter decomposition?
Statement 9: In the mangrove forest biome, is vegetation apart from trees largely composed of climbers and epiphytes rooted on upper branches?
Statement 10: In the tropical rain forest biome, does leaf litter decompose faster than in any other biome?

Statement 1

In the coniferous forest biome, does leaf litter decompose faster than in any other biome?

Origin: Weak / unclear Fairness: Borderline / guessy

Indirect textbook clues

Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 3: MAJOR BIOMES > 1. Tropical Evergreen Rainforest Biome > p. 5

Strength: 5/5

“In the equatorial evergreen rainforest biome, as many as 3000 species may be found in a few square kilometres. Te ground surface is generally covered only by a thin litter of leaves. Dead plant matter (leaves, etc.) rapidly decomposes, because the warm temperatures and abundant moisture promote its breakdown by bacteria. Nutrients released by decay are quickly absorbed by roots. As a result, the soil is low in organic matter (humus). Many species of plants and animals in this very diverse ecosystem still have not been identifed or named by ecologists. In the equatorial rainforest, because of the competition for light, ecological niches are distributed vertically rather than horizontally.”

Why relevant

States that in equatorial evergreen (tropical) rainforests dead plant matter 'rapidly decomposes' because warm temperatures and abundant moisture promote bacterial breakdown.

How to extend

A student could compare tropical warm/wet conditions (high decomposition) with coniferous climate to judge relative rates.

Certificate Physical and Human Geography , GC Leong (Oxford University press 3rd ed.) > Chapter 23: The Cool Temperate Continental (Siberian) Climate > Relationship between Glimate and Natural Vegetation > p. 220

Strength: 5/5

“4. Leaves are small, thin, leathery and needle-shaped. This is to check excessive transpiration. The leaf surface is reduced to the minimum, as transpiration can be quite rapid in the warm summer due to intense continental heating. 5. There is little undergrowth. The podzolized soils of the coniferous forests are poor. They are excessively leached and very acidic. The evergreen leaves provide little leaf-fall for humus formation, and the rate of decomposition of the leathery 'needles' in a region of such low temperature is slow. All these factors are deterrents to the growth of much undergrowth 23. B Winter in a coniferous forest.”

Why relevant

Notes that coniferous forests have leathery needle litter, low temperatures and acidic, podzolized soils, and that decomposition of needles in such low temperatures is slow.

How to extend

Combine this pattern (cold + acidic + needle litter → slow decomposition) with regional climate maps to infer slower rates than warmer biomes.

Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 30: Climatic Regions > Characteristics Of Coniferous Forests > p. 469

Strength: 4/5

“• Coniferous forests are of moderate density and are more uniform. Almost all conifers are evergreen. There is no annual replacement of new leaves as in deciduous trees. The same leaf remains on the tree for as long as five years.• Conifers are conical in shape with sloping branches that prevent snow accumulation. Their shape also offers little grip to the violent winds. Food is stored in the trunks, and the bark is thick to protect the trunk from excessive cold.• Transpiration can be quite rapid in the warm summer. So, leaves are small, thick, leathery and needleshaped to check excessive transpiration. • The soils of the coniferous forests are poor.”

Why relevant

Highlights that coniferous soils are poor and that conifers are evergreen with long-lived needle leaves (less annual leaf-fall), implying different litter quality and soil conditions affecting decomposition.

How to extend

Use the link between litter type/soil fertility and decomposition to compare with biomes that produce more labile (fast-decaying) litter.

Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 3: MAJOR BIOMES > 11. Tundra and Alpine Tundra Biomes Tudra biome > p. 18

Strength: 4/5

“During the short summer, evergreen plants develop on the ground like cushions. Tese fowering herbaceous plants include moss campions (silence acaulis). Some plants grow on the ground, like tussocks, while other vegetation on the ground surface horizontally, like mats, or compact turf. Te primary productivity in tundra biome is extremely low because of low temperatures, permafrost condition of soils, minimum sunlight and insolation. Te harsh climate results into poor vegetation, dry areas produce little litter, but wet litter accumulates to form peat and swamps and there is very little nutrient release to vegetation. It is thus clear that the scarcity of food makes the tundra animals migratory.”

Why relevant

Describes tundra as very cold with permafrost where wet litter can accumulate as peat and 'there is very little nutrient release to vegetation', implying very slow decomposition in cold biomes.

How to extend

A student can place tundra and coniferous biomes on a temperature gradient to evaluate whether coniferous decomposition might be similarly slow or intermediate.

Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 3: Terrestrial Ecosystems > 3.2. FOREST ECOSYSTEM > p. 24

Strength: 3/5

“The forest ecosystem includes a complex assembly of different kinds of biotic communities. Optimum conditions such as temperature and ground moisture are responsible for the establishment of forest communities. The nature of soil, climate and local topography determine the distribution of trees and their abundance in the forest vegetation. Forests may be evergreen or deciduous. They are distinguished on the basis of leaf into broad{eafed or needle leafed coniferous forests in the case of temperate areas. The forest ecosystems have been classified into three major categories: cbniferous forest, temperate forest and tropicai forest. All these forest biomes are generally arranged on a gradient from north to south latitude or from high to lower altitude.”

Why relevant

Classifies forests by leaf type (broad-leaf vs needle-leaf) and links forest distribution to temperature and moisture — factors that influence decomposition rates.

How to extend

Use this classification plus basic climate facts (temperature/moisture differences among biomes) to predict which biomes favour faster litter breakdown.

Statement analysis