Plant Communities and Rainforest Structure

Plant Communities

• A community is an association of interacting species in a defined area.
• Ecologists study plant communities in various locations like mountains, riversides, areas after deforestation, or gaps in the forest.
• Communities consist of numerous species that may interact in multiple ways.
• Community ecologists study how abiotic and biotic environmental factors affect community structure.
• Community structure includes species count, relative abundance of species, and the types of species.

Rainforest Structure

• Images show a diagram of a rainforest, identifying different zones (emergents, canopy, understory, leaf litter zone) and specific plant and animal life within each zone.
• Examples of plants include orchids, vines, basket ferns, palm trees, juvenile trees, elkhorn ferns, tree ferns, strangler figs, king ferns, bracket fungi, wait-a-while, and buttress roots.

After Gap Formation - Plant Community

• Images depict a forest community in the aftermath of a forest gap, showing the types of vegetation and environment.

Species Abundance

• Most species have moderate abundance; a few are abundant and a few are rare.
• Relative abundance is a crucial aspect of community structure.
• Graphs show how plant and bird species numbers relate to their percentage coverage or the number of individuals in a community.

Species Diversity

• Species diversity is a combination of species number (species richness) and their relative abundance (species evenness).
• Higher species diversity occurs in complex environments.
• Intermediate levels of disturbance often increase diversity.

Species Diversity Index

• The Shannon-Wiener index (H') calculates species diversity.
• The formula for H' is: H’ = - Σ pᵢ logₑ Pᵢ, where pᵢ is the proportion of the ith species and s is the number of species.
• The minimum value of H' is 0, occurring in a community with only one species and increases as species richness and evenness increase.

Foliage Height Diversity and Bird Species Diversity

• Bird species diversity typically increases with greater foliage height diversity.
• Plant communities with lower foliage height diversity often have lower bird species diversity.
• Forests with greater foliage height diversity support more bird species.

Variation in Vegetation

• Variations in soil type and moisture conditions lead to different vegetation types across a gradient.

Fertilization and Plant Diversity

• Plant diversity has declined progressively after long-term fertilization, as shown by rank-abundance curves.
• Declining species richness and evenness are observed in cases of fertilization.

Nutrient Availability and Environmental Complexity

• Increased nutrient availability reduces the number of limiting nutrients, often making light the sole limiting resource.
• This can lead to a dominance for algal or plant species best suited for competing for light, thus lowering species diversity.

Explore the diverse interactions within plant communities and the intricate structure of rainforests. This quiz covers the composition of different ecological zones, the species present, and community dynamics in various habitats. Test your knowledge on how abiotic and biotic factors shape these vibrant ecosystems.