Vegetation Classification Schemes
The systematic categorization of plant life is essential for understanding the relationship between biology, climate, and geology. Over the last century, scientists have developed various classification schemes to organize the diverse array of plant formations found across the globe. These systems range from broad climatic models to detailed ecological analyses of soil and species composition.
Key Facts
- Climatic Influence: Many schemes, such as Köppen and Walter & Lieth, link vegetation directly to temperature and precipitation patterns.
- Ecological Diversity: Systems like Warming's focus on hydrophilous (water-loving) and xerophilous (drought-tolerant) adaptations.
- Zonobiomes: The Walter & Lieth system identifies nine major global biomes based on moisture and cold stress.
- Physiognomy: Modern approaches, such as Oliveira-Filho, categorize vegetation by its physical appearance (physiognomy) and substrate.
- Species Composition: The Braun-Blanquet method prioritizes which specific plant species coexist within a community.
Climate-Based Classification Systems
Köppen (1884)
While primarily a climate classification, the Köppen system is deeply intertwined with vegetation studies. It divides the world into five main classes:
- Class A (Tropical): Includes tropical rainforest (Af), monsoon (Am), and savanna (Aw, As).
- Class B (Dry): Covers deserts (BWh, BWk) and semi-arid regions (BSh, BSk).
- Class C (Temperate): Includes humid subtropical, oceanic, and Mediterranean climates.
- Class D (Continental): Covers humid continental and subarctic regions.
- Class E (Polar): Includes tundra (ET), ice caps (EF), and alpine regions.
Walter & Lieth (1960–1967)
The Heinrich Walter scheme focuses on the seasonality of temperature and precipitation to define nine major zonobiomes. These boundaries are determined by moisture and cold stress, which dictate plant form.
| Zonobiome | Climate Characteristics | Zonal Soil Type | Vegetation Type |
|---|---|---|---|
| ZB I | Equatorial, always moist | Equatorial brown clays | Evergreen tropical rainforest |
| ZB III | Subtropical, arid | Serosemes, sierozemes | Desert vegetation |
| ZB VI | Nemoral, winter freezing | Forest brown earths | Deciduous temperate forest |
| ZB VIII | Boreal, cold temperate | Podsols | Taiga (needle-leaved forest) |
| ZB IX | Polar, long cold winters | Tundra humus (permafrost) | Low evergreen vegetation |
Ecological and Formation-Based Schemes
Warming (1895, 1909)
Warming introduced oecological classes based on water availability and soil conditions. He categorized plants as hydrophytes (water-based) or xerophilous (dry-adapted). His system further divides dry-adapted plants into those affected by acid soil (oxylophytes), cold soil (psychrophytes), saline soil (halophytes), rocks (lithophytes), or sand (psammophytes).
Schimper (1898, 1903) and Schimper & Faber (1935)
Schimper focused on climatic chief formation types, distinguishing between woodland, grassland, and desert. Later, with Faber, the system was refined into 15 distinct formation types, including monsoon forests, summer-green deciduous forests, and cold deserts.
Ellenberg & Mueller-Dombois (1967)
This scheme simplifies vegetation into seven formation classes, ranging from closed forests (Class I) and woodlands (Class II) to aquatic plant formations (Class VII).
Modern and Specialized Approaches
Oliveira-Filho (2009, 2015)
Primarily applicable to the Neotropical region, this system uses six hierarchical attributes: basic physiognomy, climatic regime, leaf flush regime (e.g., evergreen or deciduous), thermal realm, elevation range, and substrate (e.g., sandy, rocky, or marshy).
The Braun-Blanquet Method
Unlike broad zonal schemes, the Braun-Blanquet method focuses on the composition of plant species. By analyzing which species grow together in specific plots, researchers can determine how environmental factors influence community patterns.
Other Notable Contributions
Numerous other scholars have contributed to the field, including Grisebach (1872), Tansley and Chipp (1926), and Beard (1944, 1955). In the 1960s, A. W. Kuchler performed an extensive global review of vegetation maps to standardize terminology across continents.
Frequently Asked Questions
What is the difference between a biome and a formation?
A biome, such as those in the Walter & Lieth system, is a large-scale regional unit defined by climate and dominant plant forms. A formation refers more specifically to the physical structure and appearance of the vegetation, such as a "thorn forest" or "shrubland."
How does the Köppen system relate to vegetation?
Although it is a climate classification, the boundaries Köppen established for temperature and precipitation closely align with the natural distribution of global vegetation types.
What are xerophilous species?
Xerophilous species are plants adapted to survive in environments with limited water availability, such as deserts, saline soils, or rocky terrains.
What does the Braun-Blanquet method measure?
It measures the specific composition of plant species within a community to understand the patterns of coexistence and the environmental factors that drive them.
What is a zonobiome?
A zonobiome is a global vegetation unit defined by the interaction of climate (temperature and precipitation) and the resulting zonal soil type.