Kingdom of Plants: A Journey Through Their Evolution. Will Benson
conifer-covered mountains. Unlike the tropics, which often have both wet and dry seasons, temperate regions have four distinct seasons of varying warmth and precipitation, and through this cycle some of nature’s most striking landscapes are created. In the mountain region of south-central China some of the most dramatic habitats of temperate vegetation can be found, nourished by the waters of the five great rivers of Asia: the Mekong, Irrawaddy, Yellow, Yangtze and Salween. These are the most biodiverse temperate habitats, and among the mountain woodlands giant pandas feed on one of the most important plants of these forests – bamboo. This mighty plant makes up a key part of the understorey of the temperate broadleaf deciduous forests.
Bamboo is a member of the grass family Poaceae. In fact, bamboo is the largest grass in the world. Separating it from all the other grasses is its tough, woody stem. This gives the strongest shoots the strength of mild steel (able to withstand around 52,000 pounds per square inch, a pressure that could crush stone), making it the strongest plant on Earth. Shooting upwards like an extending telescope, each new section of the plant extends from the centre of the old sections, and the fastest species are able to advance towards the light at a staggering rate of over 5 centimetres per hour. This amazing growing capability makes bamboo a crucial plant in its forest habitat, acting as an unrivalled soil erosion control agent. Bamboo is particularly successful at re-colonising areas of land that have previously been cleared for agriculture or cattle grazing, and the re-greening of an area of land by bamboo can help return structure and life to the forest environment.
Like palms, bamboo provides us with a vast variety of building materials and foods. Bamboo-related industries are estimated to provide a livelihood for around 1.5 billion people worldwide, making it a plant of great economic importance. In Asia it is used to create high rigs of scaffolding, some over 100 metres tall, and in Central America an area of farmed bamboo forest of just 60 hectares can provide enough material to build around a thousand small houses. But it is actually the less impressive relatives of the grass family that provide humans with an even greater service. These are the grasses that give us wheat, corn, rice and maize, and that feed the animals which give us meat, leather and wool. They are the most economically important plants on the planet, and their exploitation has shaped the face of the world as we know it.
Wild grasslands
Africa’s vast protected national parks provide a snapshot of how Earth’s ancient plains would have looked.
© Flirt/SuperStock
In their wild form grasses grow primarily in the semi-arid grasslands and savannahs that make up about 20 per cent of the Earth’s surface. In the past, thousands of grazing animals such as elk, wild horse and saiga antelope inhabited these vast grasslands. Today these wild habitats are much quieter. Hunters who roamed the grasslands some 20,000 years ago caused the mega-herbivores that once dominated the landscape to disappear. Today it is primarily livestock that inhabit these landscapes. Protected habitats such as Yellowstone National Park in the USA and the Masai Mara National Reserve in Kenya now form some of the few grassland areas where one can get a glimpse of how our grassland ecosystems would have looked without human interference.
Plants that grow in grasslands are highly resilient to drought, and are often able to withstand months without rainfall. Short hairy grasses such as june grass (Koeleria cristata), which grows in North America’s dry prairies, have shallow roots that sit just under the surface of the ground, so that as rainwater soaks into the ground it can be absorbed by the plant. Conversely, taller grasses like elephant grass (Pennisetum purpureum), which grows to around 5 metres and, as its name suggests, is a favoured food of Africa’s largest herbivore, have hair-like, branching roots reaching up to 6 metres in length, enabling them to reach sources of water held deeper in the soil. As a means of saving water, many grasses also have long, narrow leaves which lose far less water in the drying sun than larger leaves would.
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