– Description:
– Cushion plants form large, low-growing mats up to 3m (10ft) in diameter.
– They have a compact mass of closely spaced stems with minimal apical dominance.
– Cushion plants typically die en masse rather than individual rosettes dying separately.
– Growth rates range from 0.06cm (0.02in) to 1.82cm (0.72in) per year for different species.
– Some cushion plant species can live up to 350 years, with individual plants reaching up to 3,000 years old.
– Ecology:
– Cushion plants grow in rocky, sandy soils in alpine, arctic, and subantarctic habitats.
– They are key species in climax communities and initiators of primary succession in bare habitats.
– Adaptations to harsh alpine environments include mechanisms for water retention and heat trapping.
– Cushion plants act as ecosystem engineers, altering soil conditions to facilitate species colonization.
– Some species have large flowers to attract pollinators over long distances.
– Diversity:
– About 338 cushion plant species in 78 genera have evolved globally in response to similar environmental conditions.
– Species are found in diverse plant families such as Apiaceae, Asteraceae, and Caryophyllaceae.
– Cushion plants are not endemic to a single area but are found in regions from Tasmania to the arctic tundra.
– The plant form has evolved convergently in response to specific environmental challenges.
– Various studies have been conducted on the growth, longevity, and ecological impact of cushion plants.
– References:
– Studies have been conducted on specific cushion plant species like Silene acaulis and Azorella compacta.
– Research has focused on the evolutionary aspects of cushion plants and their ecological roles.
– Cushion plants have been described as ecosystem engineers due to their impact on soil conditions.
– Various publications have explored the growth patterns, age determination, and adaptations of cushion plants.
– References include works on the impact of cushion plants on community organization and ecosystem dynamics.
– Notable Observations:
– Cushion plants actively grow in limited periods with adequate warmth and sunlight for photosynthesis.
– Adaptations for water retention include extensive root systems and reduced transpiration rates.
– The growth form of cushion plants helps trap heat, allowing them to warm above ambient temperatures.
– Some species have evolved specific mechanisms like thick hairs to conserve heat and prevent water loss.
– Cushion plants play a crucial role in increasing soil moisture and temperature, promoting species richness in harsh environments.
A cushion plant is a compact, low-growing, mat-forming plant that is found in alpine, subalpine, arctic, or subarctic environments around the world. The term "cushion" is usually applied to woody plants that grow as spreading mats, are limited in height above the ground (a few inches at most), have relatively large and deep tap roots, and have life histories adapted to slow growth in a nutrient-poor environment with delayed reproductivity and reproductive cycle adaptations. The plant form is an example of parallel or convergent evolution with species from many different plant families on different continents converging on the same evolutionary adaptations to endure the harsh environmental conditions.
