What a Bizarre Underworld

Most visitors don't know much about the goings-on in the underworld of the national park. Go and marvel at the small and big miracles of decay, whimsical creepy-crawlies and nail-biting predator-prey encounters in the "Wurzelhöhle" (root den) in the National Park Centre.

25 million leaves fall onto each hectare of the forest floor of the national park every year. Where do they all disappear to? Surely they should be piling up year after year! But no, an army of hundreds of thousands busy little insects, worms and woodlice take care of the forest's organic waste. Every animal has a specific task in this process: shredding, eating, converting material, making leaf pulp. At the end of the cycle, the pretty green beech leaves from the summer will have been turned into nutrient-rich humus, which can then be re-used by the ecosystem.

But that is not all – who could have guessed that plants communicate with one another, above and below ground! Above ground, trees warn each other via volatile organic compounds, so-called green-leaf volatiles, of insect damage and store repellents in the leaves in order to spoil the parasites' meal. Elm trees even use green-leaf volatiles to target and attract predatory insects, who in turn kill the attacking leaf eaters. The saliva exposed the attacking species and the anti-volatile is tailor-made for it. Also, when the roots of neighbouring plants touch, they are not only used for water and nutrient uptake, but also for alert eavesdropping. For example, information on impending draughts are passed up and on via chemical substances in order to arrange the required precautionary measures.

The roots of the beeches in Hainich also play host to a very useful partnership, a symbiosis that has advantages for both parties. The partner is mycorrhizal mycelium, which connect to the fine ends of the roots. That means one partner is fully dependent on the other and yet it is a win-win situation for both: The fungus helps the tree not only with its uptake of water and nutrients, it also repels germs or even secretes substances that are poisonous to herbivores. In return, the tree provides the fungus with products of photosynthesis, which, being a fungus, it cannot produce itself.