Module 6: Biological Diversity and Biomes

Comprehensive review flashcards covering biodiversity concepts, biome characteristics, fire ecology, disturbance dynamics, invasive species, and climate change impacts.

How is biological diversity defined in the lecture notes?

The variability among living organisms in an area and the ecological complexes of which they are part, representing the totality of genes, species, and ecosystems.

Which four components define biological diversity?

1. Number of species; 2. Diversity of types; 3. Genetic diversity; 4. Ecological or structural diversity.

What are the three core attributes of biodiversity, and what outcome is each linked to?

1. Composition (linked to species persistence); 2. Function (linked to ecosystem functioning); 3. Structural/heterogeneity (linked to resilience to environmental change).

What is a keystone species, and what examples are listed in the lecture?

A species whose removal causes the environment to respond significantly, either positively or negatively. Examples include African savannah elephants, sea otters, ants in fynbos, Pacific salmon (slalom), and red mangrove trees in the tropics.

How is functional biodiversity defined?

The component of biodiversity that influences an ecosystem's productivity and other aspects of performance and ecosystem services.

What does structural biodiversity describe, and what factors determine habitat heterogeneity?

It describes how patchy the landscape is and how connected those patches are. Habitat heterogeneity is driven by slope, soil depth, altitude, and soil types.

What is a biome, and what determines its classification?

A broad ecological unit characterized by unique dominant forms of plant life and prevailing climate. Biomes are determined by plant growth forms and major climatic features, not floristically.

How do phanerophytes and geophytes differ in their location of apical buds and regenerative ability after disturbance?

Geophytes keep their apical bud protected below the ground in the soil to regenerate after disturbances; phanerophytes hold their apical buds high above the ground and evolved without high stress, meaning most do not regenerate if cut.

What are the six major drivers of plant diversity in the Fynbos biome?

1. Heterogeneity of habitats; 2. Nutrient-poor soils; 3. Adaptation to fire; 4. Hot dry summers; 5. High endemism; 6. Long evolutionary history.

What are the four primary causes of local variation in plant diversity within the Fynbos biome?

1. Heterogeneity of habitats (slope, soil types, soil depth, altitude); 2. Alien invasive species; 3. Fire frequency; 4. Land use (urbanization and agriculture).

Which three indicative plant taxa are used to identify the Fynbos biome?

Protea, Restio, and Erica.

What specialized vegetative structures enable fynbos plants to regenerate following a fire?

Above-ground epicormic buds on stems and underground lignotubers.

What unique global ecological status does the Succulent Karoo biome hold?

It is recognized as a global biodiversity hotspot and is the only arid biodiversity hotspot in the world.

What is the primary land-use practice and major disturbance factor in the Succulent Karoo biome?

Livestock grazing; while it can stimulate plant growth when properly managed, unmanaged grazing destroys the vegetation's capacity to regenerate.

Why is the Grassland biome considered the most disturbed biome in South Africa?

It experiences intensive transformation from mining, urban and industrial expansion, conversion of its rich soils for crop agriculture, and woody shrub encroachment.

Which three environmental factors maintain grass dominance and prevent tree establishment in the Grassland biome?

Frost, fire, and grazing.

What are the key ecological characteristics of the Savanna biome in South Africa?

It is the largest biome in South Africa, contains over $5700$ species, ranges from sea level to $2000\,\text{m}$ in altitude, receives summer rainfall, experiences $0\text{--}120$ days of frost, and supports diverse browsers and grazers.
Excellent rangeland

Has the big five (lion, leopard, rhino, buffalo, elephant)

Good rangelands, browsers and grazers (browsers are ones that look and reach for trees while grazers are on the ground. Thus diet is different) We see difference in animal anatomy and physiogoly based on them being browsers/ grazers

Savana trees have evolved structures to protect their buds and can regenerate after a fire

What are three critical ecological functions of fire across biomes?

1. Acting as a mineralizing agent; 2. Causing scarification to break seed dormancy; 3. Reducing inter-plant competition.

How do abiotic and biotic factors collaborate to maintain the Savanna biome?

Abiotically,

-           Seasonal rainfall supporting wet season and limiting dry season

-           Soil often nutrient-poor and well frained, favoruting grasses

-           Fire then prevents overgrowth and help grasses to regenerate quickly

Biotically, grazers (zebras, antelopes) suppress grass overgrowth while browsers (elephants, giraffes) consume young trees and shrubs, maintaining open structure.

What limitations of protected areas contribute to ongoing biodiversity decline?

1. Reserve fragmentation and small size; 2. Severe local pollution; 3. Inability to capture micro-scale vegetation turnover that changes within meters; 4. Poor reserve management.

What traits make invasive pine trees competitive, and what negative impacts do they exert on ecosystems?

They exhibit high growth rates and lack native predators or diseases. They shade out native plants, acidify soils by increasing anions such as oxalate and malate, deplete soil seed banks, and increase transpiration rates.

How do invasive Australian acacias modify soil chemistry compared to invasive pines?

They possess strong $N_2$-fixing capabilities, high relative growth rates, and high carbon allocation, which increases soil nutrient levels and makes the soil nutrient-rich.

Which four indigenous or non-invasive acacia species are identified in the notes?

V. karroo, V. tortilis, V. nigrescens, and V. nilotica.

How does elevated atmospheric $CO_2$ favor woody trees over grasses in grassland ecosystems?

Grasses are predominantly $C_4$ plants that do not gain a photosynthetic advantage from elevated $CO_2$, whereas trees are $C_3$ plants that respond positively to elevated $CO_2$, allowing woody plants to expand and encroach into grasslands.

What climatic and environmental changes are projected to drive biodiversity loss according to the notes?

A temperature rise of $1\text{--}3\,^\circ\text{C}$, disrupted regional rainfall patterns with prolonged droughts and intense storm events, more frequent and intense wildfires, and woody alien plant encroachment.

What are characteristics of fynbos?

Some parts of the biome gets rainfall throughout the year

Winter rainfall mostly in the west, brings stress to plants

Hot dry summer (excellent thermoregulation system)

Infertile acidic soils

Shrubs with small, hard and thick leaves (sclerophyllous) adapted to fire, high biodiversity, and many endemic species.

What is the plant composition in the karoo?

Succulents shurbs (chametophytes)

Geophytes

woody shrubs

pernimial grasses annuals

What are characterisitcs of the succulent karoo biome?

Winter rainfall region

considered a biodiveristy hotspot, only arid hotspot in the world

very dry areas

dominated by dwarf, succulent shrubs adapted to survive dry summers and harsh conditions, with a wide variety of endemic species.

What are characterisitcs of grasslands?

Topography is mostly flat

Landscape heteogenity is very low

includes some escaprments

Areas has a single layer of grasses

trees usually absent due to fire disturbances (these trees dont regenerate)

Most plants are grasses and geophytes

biome burns regularly, therefore very few woody plants

summer rainfall area

What re major threats to grasslands

Mining , urban and industrial expansion

shrub encroachment

What grazers are typically found in grasslands

Black wildebeest, blesbok and Eland