GCSE geography revision. The living world - section B

Climate characteristics of tropical rainforests

Year-round warmth averaging around $27\,^\circ\text{C}$ and high annual precipitation exceeding $2000\,mm$, without distinct cold or dry seasons.

Nutrient profile of tropical rainforest soils (latosols)

Relatively infertile and acidic because heavy rainfall continuously leaches soluble nutrients downward, leaving nutrients concentrated mainly in a thin surface layer of decomposing leaf litter.

Drip tips

Foliage adaptation featuring elongated, downward-pointing leaf apexes that channel heavy precipitation off quickly to inhibit fungal disease and prevent stem breakage.

Buttress roots

Massive, ridge-like surface structures that stabilize tall canopy trees in shallow soils while absorbing nutrients concentrated in the topsoil.

Epiphytes

Plants that perch harmlessly on tree trunks and high branches to access sunlight, absorbing moisture and nutrients directly from the air and rainfall.

Primary driver of Amazon deforestation

Commercial cattle ranching for beef production, which accounts for the vast majority of cleared forest, followed by extensive commercial soy farming.

Environmental impacts of tropical deforestation

Widespread soil erosion from torrential rains stripping uncovered soil, dramatic biodiversity loss, and reduced regional moisture cycling alongside increased greenhouse gas emissions.

Debt-for-nature swap

A financial arrangement in which a portion of a developing nation's foreign debt is cancelled or reduced in exchange for documented investments in local conservation reserves.

Selective logging

A sustainable timber harvesting method where only designated mature trees are extracted, preserving canopy cover, soil stability, and underlying habitats.

Aridity threshold for hot deserts

Regions receiving under $250\,mm$ of annual precipitation, where potential evapotranspiration greatly exceeds precipitation.

Diurnal temperature range in hot deserts

Large daily shifts often exceeding $30\,^\circ\text{C}$, with daytime temperatures over $40\,^\circ\text{C}$ and nighttime temperatures near freezing due to clear skies lacking cloud insulation.

Succulence in desert vegetation

Fleshy structural tissues specialized for storing retained moisture, shielded by thick waxy cuticles and sharp spines that deter herbivores and minimize transpiration.

Phreatophytes (deep tap roots)

Desert plants equipped with vertical root structures that bore down to depths of up to $50\,m$ to access moisture from subterranean aquifers.

Desertification

The gradual degradation of productive semi-arid and dry sub-humid land into barren, unproductive desert terrain.

Anthropogenic causes of desertification

Overgrazing by livestock, continuous overcultivation, population pressure, and firewood harvesting that strip vegetation and expose loose topsoil to erosion.

Magic stones (stone lines)

Low lines of rocks stacked along farmland contour lines to decelerate surface runoff, trap fertile silt, and increase water infiltration into arid soils.

Economic opportunities in the Thar Desert

Substantial solar and wind power generation, mineral quarrying for limestone and gypsum, commercial tourism, and canal-fed crop cultivation via the Indira Gandhi Canal.

Development challenges in hot deserts

High ambient heat causing heat illness and high evaporation, chronic water deficits for agriculture and industry, and mobile dunes that obstruct transport routes.