Diversity of Humid Tropical Forests

• Humid tropical forests encompass a vast array of forest types  due to their complex interplay of latitude, longitude, soil composition, and climatic conditions.
• This complexity leads to a mosaic of vegetation types, each contributing to the exuberant diversity found in tropical regions.
• Understanding the vast diversity of tropical forests can be challenging. On this page, we will focus specifically on the forest types found in Odzala-Kokoua National Park.
• The park showcases various forest ecosystems, each contributing to the region's rich biodiversity.
• For those interested in a deeper exploration of tropical forest classification globally, I recommend visiting (Science Direct - Tropical Forests).
• The terms "primary forest" and "secondary forest" are outdated, as they oversimplify the complex, diverse processes and human influences on forests, often leading to misunderstandings. For more information, see (Springer: Rethinking Forest Landscapes) and (World Agroforestry: Secondary Forest).
• Humid tropical forests, such as those in Odzala-Kokoua National Park, are characterized by their high rainfall and humidity. These conditions support dense, diverse canopies due to constant water availability, high humidity reducing water loss, rapid nutrient cycling, and high biodiversity.

Characteristics of Humid Tropical Forests

Humid tropical forests have the following characteristics:

Fire Sensitivity: They generally do not burn naturally; if they do, it is usually due to human intervention, and the fires can be highly destructive. Unlike savannah trees, these forests are very sensitive to fire.

Angiosperm Dominance: Primarily composed of flowering plants known as angiosperms, these plants develop seeds within an ovary that matures into fruit. Angiosperms are crucial for biodiversity, providing diverse habitats and food sources for numerous animals. Their flowers also facilitate complex pollination relationships.

Nutrient Recycling: The trees largely sustain themselves by continuously recycling their own organic matter. Therefore, they are less dependent on the underlying soils, except in extreme cases such as rocky or heavily leached soils.

Dominant Forest Structures in Odzala-Kokoua National Park

The majority of Odzala-Kokoua National Park is covered by a semi-evergreen humid tropical forest, which represents a transitional ecosystem between tropical evergreen forests (commonly referred to as "tropical rainforests") and tropical deciduous forests. This forest type features a combination of both evergreen species (trees that retain their leaves year-round, typical of what is generally known as tropical rainforests) and deciduous species (trees that shed their leaves seasonally). This mix of trees and other plants enables the tropical forest to adapt to the varying rainfall patterns within the park, making it a distinct and resilient ecosystem.

Within these forest, two main forest structures dominate: closed-canopy forests and Marantaceae forests:

1.  Closed-Canopy Forest

Closed-canopy forests are characterized by a dense canopy that limits light penetration to the forest floor, resulting in a relatively open understory.

• Structure: The canopy is dense with trees reaching heights of 20-30 meters, and emergent trees rising up to 40-50 meters. This structure creates a layered habitat that supports a wide range of species.
  
  
• Biodiversity: These forests are rich in biodiversity, with over 350 species of trees and shrubs. The dense canopy provides habitats for various birds, mammals, and insects, while the open understory supports smaller plants and ground-dwelling animals.
  
  
• Canopy Competition: The dense forest canopy fosters intense competition among plants for sunlight, driving adaptation and growth strategies
  

2. Marantaceae Forests

• Structure: Characterized by a sparse tree cover (open canopy) and dense understory thickets, reaching heights of 1-4 meters, dominated by plants belonging to the Marantaceae family. This creates a unique habitat structure distinct from closed-canopy forests.
  
  
• Protection and Refuge: The dense understory thickets of Marantaceae forests provide crucial habitats, offering both protection and refuge for various species. These forests are particularly vital for endangered western lowland gorillas and forest elephants, giving them essential shelter and a secure habitat.
  
  
• Food Resources: Marantaceae plants are a reliable, year-round food source. Gorillas feed on the leaves, stems, and fruits of these plants, while elephants forage through the dense vegetation.

  To dive deeper into the fascinating world of Marantaceae forests and their ecological significance, I  recommend the following link: Cambridge University Press: Marantaceae forest; gorillas
  

(3.) Mosaic Forests

These forests feature a mix of closed-canopy forests, savannahs, and other vegetation types due to variations in soil composition and water availability, creating a complex and dynamic landscape​. The areas accessible to park visitors are predominantly covered by mosaic forests.

• Characteristics: These forests include patches of closed-canopy forests, open areas, and other vegetation types. This diversity creates a complex and dynamic landscape.
  
  
• Visitor Experience: Mosaic forests offer visitors a chance to experience a variety of habitats within a relatively small area, showcasing the ecological diversity of the park.

Seed dispersal

• In tropical forests, animals play a crucial role in seed dispersal. Forest elephants act as key 'gardeners,' consuming large amounts of fruit and dispersing seeds. Their preference for certain fruits significantly influences the composition of tree species in their environment, shaping the forest structure.
  
• Birds, primates, and bats are particularly important for spreading epiphyte seeds, which are essential for the forest's layered architecture.
  
• Additionally, forest elephants and buffaloes have shaped the landscape over centuries by creating extensive networks of trails, further influencing plant distribution and forest dynamics.

• Biomass is the dry weight of all living or recently living organisms in an environment, crucial for carbon storage and energy flow in ecosystems.
• Scientists estimate the Earth's total biomass at approximately 550 billion tonnes, with plants contributing about 80% and bacteria about 15%. Tropical forests, which account for 40-50% of the world's terrestrial biomass, are home to over 50% of all species on Earth.
• The remaining biomass consists of fungi, animals, and viruses, with human biomass representing only 0.01%—equivalent to the total biomass of all termites!

(PNAS-Biomass distribution on Earth)