When the sun goes down at the end of the day, what happens in the forest?
Many of us may think as we settle in for the evening that plants will also be taking it easy during the night – the hard day’s work of photosynthesis is over and surely it’s time for them to stand tall and relax! But this often isn’t the case. In the forest things are often just getting started – life for the trees is one big around the clock party!
So what is really happening out in the forest at night? Are the animals really the stars of the show? Or are they just bit-players in a much bigger drama? Are the animal’s mere pawns in a game that is being played out by higher life forms- that is to say the Trees (if you’ll pardon the pun)?
We know that fruit and nectar eating birds are on the day shift for spreading the seed and pollen of various trees and plants. However, we are often completely unaware (because we are curled up in front of the telly or in bed or both) of the important role our fellow mammals play in the dispersal and pollination workforce for our local forest plants at night. For instance are you aware that most eucalypt cross-pollination occurs at night courtesy of the much maligned, flying foxes. In a recent study of flying foxes Pteropus sp. it became apparent that eucalypt flowers where at their most receptive to cross-pollination during the hours of darkness. These trees rely upon flying foxes and other blossom bats to facilitate some serious genetic interchange over the vast distances that they travel in search of food. Some local eucalypts that attract nectar-feeding bats include Flooded Gum – Eucalyptus grandis, Tallow wood – Eucalyptus microcorys and the Pink Blood Wood – Eucalyptus intermedia.
Mammals aren’t the only creatures of the bush being enticed into working for the plants during the night. As the sun sets in the forest, the air can become thick with the intoxicating perfumes of some forest plants and although humans may appreciate these scents the real targets of these perfumes are the moths. Just like some humans use perfumes for the purposes of romance, these night time flower scents are designed to attract moths to their flowers and so spread their pollen from flower to flower – the moths thus play an unwitting role in the love lives of plants. The moths are rewarded with a small prize of nectar for their work, but not too much, just enough to get them to the next flower! Some night/evening perfumed flowers are Wilkea – Wilkea macrophylla, Native Jasmine’s – Jasminum sp., Mat rush’s – Lomandra sp., and Musk wood – Alangium villosum.
The flowers of the night are often white to reflect whatever light is available ie. “by the light of the silvery moon”. Flowers aimed at the moth demographic are often small simple flowers such as Chain fruit Alyxia ruscifolia, Banana bush Tabernaemontana pandaqui and Native currant Carissa ovata. Flowers aimed at the larger mammalian pollinators such as flying foxes, possums and many other nectar-loving marsupials often carry a larger reward of nectar to satisfy these sugar-hungry mammals. The flowers are brush-like in design to cover the snouts of the foraging animal in pollen. Flowers of the family Myrtaceae such as Eucalyptus sp., Syzygium sp. are typical of the flowers designed to attract mammals.
Crucial to the health of most forests is their relationship with mycorrhizal fungi. Mycorrhizal fungi actually engage in a symbiotic relationship with plant roots whereby they form a protective sheath over the plant roots and make more water and trace elements available to the plant through their hyphae (a fine network of tissue, that comprises the fungi feeding organ). In return, they receive carbohydrates from the plants. What has all this got to do with the night time activities of the forest, I hear you say? Now here’s the really amazing bit! Some of the mycorrhizal fungi have truffle like fruiting bodies. These truffles are an important food source for about 37 native mammals that include wallabies, bandicoots, rodents, potoroos and bettongs. The nocturnal bettongs and potoroos are specialist truffle eaters. Bettongs in particular have a specialised digestive system for making the most of the truffles they eat. The spores of truffles pass safely through the digestive systems of the animals and are deposited in a neat little fertiliser package ready to colonise new ground. These animals are crucial to the spread of some of these mycorrhizal fungi and in turn the fungi are crucial as a food source to the animals. What a wonderful case of mutual benefit!
However what happens when small marsupials such as the bettongs and potoroos become extinct in an area, due to habitat loss and feral animal predation? It could be speculated that not only do we lose some of our wonderful local fauna but that mycorrhizal fungi populations will be affected, by the loss of their main dispersal agent. Flowing on from that, tree health will be affected. The old analogy about ecology being like a spider web becomes more and more relevant in a story like this, because removing one thread often has serious effects on all the other threads and the web as a whole.
So we must all do what we can to maintain the diversity of our local ecosystems and be awed and thankful for the amazing local environment that we live and work in.
References:
Wildlife of Greater Brisbane, QLD Museum Publication
Tropical Topics, Wet tropics Management Authority
Thanks to Les Hall for his information re. flying foxes and eucalypt pollination and Jim Reside for his information on the importance of small marsupials and truffles.
by Spencer Shaw