Good soil, gardeners say, should resemble chocolate cake – in both its color and its crumbliness. Good soil has lots of air in it. Why?
First, because these channels and pockets of air also serve as pathways and holding places for water. As discussed in the previous post, we want water to move down into soil. Loose soil structure helps that to happen. Soil that is dense and hard will resist water, leaving it pooled on the surface, where it will either cause flooding, or run off to cause flooding somewhere else.
Second, because the air spaces in soil provide room for roots. Plant roots grow easily through loose soil. Under these conditions, plants are able to find nutrients, absorb water, and anchor themselves securely. In contrast, roots struggle to penetrate soil without air, leaving the plants sickly and weak.
Soil without air is compacted soil. Soil compaction is events and processes that lead to compacted soil.
What kinds of things cause soil compaction? One major perpetrator is development: covering soil with pavement is, of course, not good for the soil. Another cause is heavy vehicles. A bulldozer or brush hog may be the fastest way to clear a site of unwanted vegetation and prepare it for new plantings, but these huge machines also cause serious damage to the soil on the site, making it more difficult for the new plantings to get a start in life.
Even lighter vehicles are tough on soil. ATVs can cause compaction and damage, which is one reason some people oppose the use of ATVs in natural areas. And finally, a person on foot is heavy enough to squash down soil and destroy those crucial air pockets.
For this reason, treehuggers may want to curb their desire to hug trees. When we walk up to a tree’s trunk, we are stepping on its critical root zone – the area directly under the tree’s canopy, where its roots are most actively performing their vital functions. Compacting the soil in this area can be very detrimental to a tree’s health. While some tree species – such as those that have evolved to live in perennially soggy areas – are adapted to compacted soil and able to withstand those conditions, many other species suffer from the suffocation of their roots.
Humans like hugs. Trees are indifferent to them. In a few weeks, That Blog will look at simple things tree lovers can do that trees will really appreciate.