Why We Need Trees.

This article mainly concentrates on the most obvious part of any forest or woodland.. the trees.

When the land we now live on was first settled by Europeans, it was covered in the native bush – kwongan, woodlands and forests that had adapted to grow on the ancient sands, an incredible biodiversity of species with fascinating ecological connections. A particular ant is needed to pollinate a rarely flowering shrub. Orchids that look like female wasps so that the male wasps land and pollinate the flower, not the lady wasp! Thousands of amazing species all helping each other.

Paraserianthes lophantha syn Albizzia lophantha. Makes lovely mulch, attracts ladybirds.

Time and construction of homes and roads and industrial areas has seen most of the Swan coastal plain’s ancient biodiversity areas destroyed. The rare and increasingly threatened remnants need to be preserved at all costs so we have places for flora and fauna to exist. Habitat loss can mean the end of a species if it has nowhere to move to. This one reason alone is enough to stop the madness that is destroying the Beeliar woodlands and wetlands, the last parts of what  once was an extensive network of Indigenous places. The lakes have been used for millennia for the Beeliar people to live. It would have been a pretty good life, being near the coast, too. The best of both worlds.

A single tree has a lot going on day-to-day. There is so much to say about how important trees are to biodiversity, soil health and soil building, to wind and rain patterns, flood and erosion control and more. There is no way I will cover it all just here. They provide us with so many free services its just mind-boggling.

Temperature regulation

Shade is the most readily recognised service that trees provide. Sadly, too few folk will grow shade rather than nail it up as shadecloth.

Living plants cool the area better than fabric and more dense foliage provides more shade. Trees along pavements, roads and in car parks reduce

ambient air temperatures by casting shade and they add humidity to the air by transpiration. This helps to prevent the cement or bitumen heating up, reducing ground temperature by a few degrees. For this reason alone urban trees are vital.

The heat island effect happens where roads and pavements and brick homes heat up during the day and the absorbed heat is slowly released back into the surrounding environment overnight. Heat lag allows no relief on hot summer nights.

Garden/forest canopy

As UV intensity rises and summer temperatures are likely to increase it is becoming clear that we need shelter from the mighty sun. Avenues of trees and selected trees in gardens can protect low-growing plant layers from intense UV. Choosing the right trees is important though. Some trees can cause trouble if they are too big.(see this post: http://humusbeings.com/index.php/2016/12/06/nightmare-trees-right-tree-wrong-place/)

Many fruit trees are suitable for shade as well as producing food. Macadamia and pecan do well here, too.

Habitat

Euc caesia. Not much shade but pretty flowers. Attracts birds.

There are literally thousands of organisms associated with large trees. From leaf nibblers at the top, all the critters that live beneath and on the bark or inside the tree, and the fungal associations in the soil and the soil level insects and spiders. These populations help control pests on the tree and surrounds and feed it with their wastes.

Moisture capturing/evaporation.

At night leaves can catch large amounts of condensation, especially near the coast. This moisture can keep the plants alive. Certain types of foliage are better at this job than others having evolved to direct water to the base of the plant.

This capturing of moisture is termed interception. It applies to the amount of water caught by the leaves, stems, bark, animals, spiders webs etc that catch any moisture within the tree or shrub which can then be released slowly to the soil or the air through evaporation. 
One tree can catch a lot of water when it rains, which is why trees are good to get under in a rain shower. The leaf area index or leaf surface of a large tree can be 16 hectares – which can catch a lot of condensation.

This strategy can also be copied to collect water in deserts using upright ceramic walls, which trap condensation and collect it in gutters. River stones, broken roof tiles and plastic tree-bags can collect enough dew from the damp night air to keep a young plant alive.

Part of the result of this moisture catching is that when evaporation occurs the next day clouds can be reformed from the amount of water being transpired and evaporated (evapotranspiration). Cloud forming needs some water to exist already in the soil to happen and the area of trees must be 20 km2 or more, which is why clouds disappear from a landscape after extensive clearing.

Soil protection and creation.

Slowing rainfall hitting the ground is also part of the interception process. Heavy raindrops can damage bare soil surfaces.

Trees slow down the rain by reducing its impact on the ground, intercepting and redirecting it along branches to the base of the plant or out along the drip-line to its outer root area. The rain that passes through the canopy of leaves is termed throughfall and is nutrient rich, from airborne dust particles and insect and bird wastes.

Large buttress roots hold trees down by weight to prevent blowing over while others have deep clinging roots reaching down into crevasses and cracks in rock. In this and other ways trees create soil by burrowing down, breaking up rocks, allowing water into holes left by dead roots left underground; mining for their own mineral needs. Deciduous trees provide some of the best humic material for compost heaps and allow northern winter sun to warm our homes and gardens.

Soil water.

Open ground with trees or gardens on it is also able to allow rain to recharge the water table. Paving and roads stop water soaking back into the earth so “bore water” isn’t being replenished. Tree roots allow water to slowly soak down. Large amounts of water can exist in the soil, reducing the need of irrigation if enough is stored in the ground.

Windbreaks

One kilometer into a forest the air is still. Trees slow winds, dust settles out and the air is clean.

Windbreaks can be planted to mimic some effects of forests. In very windy areas, such as near the coast and on slopes, trees can be seen to be wind-blown away from the prevailing conditions. Multi-layered rows of tough species can reduce wind impact on establishing gardens.

Urban Forestry Tree products.

Quandong.

There are dozens of trees with edible products, many easy to grow for home fruit and nut supplies. Not all of these edible crops are well known. There are many hardy and less commercial types of fruit available that may not transport well, so are best grown in your own backyard, where the only fuel needed is yourself. Permaculture groups are a great source of interesting and rare species. It’s been wonderful seeing species appear and be shared that we only ever read about to start with.

We mustn’t of course forget the thousands of other products such as spices, tool handles, posts, furniture, medicine and timber and more, which trees can provide. 
But I won’t go into that now.

 

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