In the tropical rainforest, there always exist battles, ones to claim the tree's dead body and the vast amount of nutrients that it contains. It's a battle that is fought throughout the natural world, involving a group of organisms that humans rarely notice.
On the floor of a tropical rainforest, it's dark, humid and hot, providing ideal conditions for fungi (真菌). Humans normally think of fungi as things like this— mushrooms of one kind or another. But these are just the fruiting bodies. They exist for most of the time hidden in the leaf litter and the earth as a network of fine white threads.
The threads of competing fungi envelop their victim's body, releasing enzymes (酶) which digest the tree's tissues and unlock the nutrients within. There are a million or so different species of fungi in the tropics. Some feed on dead plants. Others eat them alive. And some reveal their existence in an eerily beautiful way. In Africa, in Congo, this is known as chimpanzee fire. The mysterious glow becomes brighter as the fungi digests the tree. When fungi have fed sufficiently, they develop their reproductive organs.
Each can produce literally billions of spores (孢子), the tiny particles that carry the species' genetic blueprint. Each spore like this has the potential to kill a tree. The spores are so light that they can be carried by the slightest air currents. At least a billion float above every square meter of rainforest.
Recently, it has been discovered that these spores do far more than just bring death and decay. They are, in fact, at the very center of the rainforest's life support system. High in the humid air, the spores combine with molecules of water. Gradually, they collect into droplets, which fall as rain when they are heavy enough. Over two-and-a-half meters of rain falls every year in a rainforest. And in the center of almost every raindrop, there is a fungal spore.
