Geography – Vegetation, soils and ecosystems in tropical environments | e-Consult

Tropical Rainforests: Characterized by high temperatures (averaging 25-30°C), consistently high rainfall (2000-10000mm annually), and nutrient-poor soils. Vegetation is dominated by tall, broadleaf evergreen trees forming a closed canopy, limiting light penetration to the forest floor. This results in distinct vertical stratification: emergent layer, canopy, understory, and forest floor. Adaptations include: buttsroots for stability in shallow soils, drip tips to facilitate water runoff, aerial roots for nutrient absorption and support, and large leaves to maximize light capture. The high humidity also supports epiphytes like orchids and ferns. The closed canopy reduces evapotranspiration, contributing to the rainforest's high humidity. Nutrient-poor soils are rapidly replenished by decomposition and nutrient uptake by the dense vegetation.

Savannas: Found in tropical regions with distinct wet and dry seasons. Temperatures are high, but seasonal rainfall is significantly less than in rainforests (500-1200mm annually). Vegetation is dominated by grasses, with scattered trees or shrubs. Trees are often drought-resistant and have adaptations like thick bark, deep roots, and small leaves or spines to reduce water loss. Grasses are adapted to fire and grazing, with extensive root systems. Adaptations include: thick bark to resist fire, deep taproots to access groundwater, spines to deter herbivores, and seasonal leaf shedding to conserve water. The seasonal drought influences the distribution and type of vegetation, with areas closer to water sources supporting denser tree growth.

Comparison: Both ecosystems experience high temperatures. However, the key difference lies in rainfall. Rainforests have consistent high rainfall leading to dense, evergreen vegetation, while savannas have seasonal rainfall resulting in grasslands with scattered trees. Soil conditions differ significantly, with rainforests having nutrient-poor soils and savannas having more fertile soils due to seasonal decomposition. Both ecosystems exhibit adaptations to water availability and nutrient limitations, but the specific adaptations differ based on the prevailing conditions.

Contrast: The closed canopy of the rainforest contrasts sharply with the open canopy of the savanna. The dominance of trees versus grasses is a major difference. The level of biodiversity is significantly higher in rainforests. The rainforest is less affected by fire than the savanna, which is a frequent occurrence in savannas and shapes the vegetation composition.