Soil Oxygen: The Real Limiting Factor For Urban Trees

Among some of the common questions regarding urban trees:

1. Why can’t we save all the rain during the winter months for the trees during the summer droughts?
2. Why most trees do not have deep roots?
3. Why compacted soils are bad for your landscape?
4. Why do trees love grow roots under sidewalks in between concrete and compacted soils?
5. We all know overwatering creates an anaerobic condition that is bad for roots. But how long does it take for the process to start? When your plants are overwatered, you have two options: drain the water to save the plants (wastewater) OR save the water (waste the plants). What makes Plant Available Water different from the water applied to the soils?
6. Why volcano mulching is bad for your trees while foot-deep leaf litter in natural forests is good for the trees? What is the difference between double/triple shredded mulch versus arborist chips? Stockpiled topsoils are commonly sold to the landscaping companies.
7. Why high salinity soil is bad for trees?
8. Is stockpiled topsoil still the same topsoil?
9. Should you remove or retain steel wire baskets at planting? Do the wire baskets rust away before they limit root growth and/or straggle trees?

What is the one thing in common for all of these questions? 

Soil Oxygen.

When soil oxygen is low, it not only affects the growth of tree roots, but also significantly affect the soil microbiome and soil health. Then can we measure soil oxygen? Conventionally, it is very cost-prohibitive and inconvenient to measure soil oxygen with expensive laboratory equipment. So it is rarely discussed and prescribed in tree planting projects. In this talk, we will demonstrate a novel, easy, fast, low-cost, and convenient way of measuring soil oxygen. This will add a tool to the arborist’s toolbox for diagnosis of tree problems. With this new tool, arborists will be able to have a better insight of the root causes instead of just suspecting, prescribe the often neglected soil oxygen, grow better trees, and serve their customers better.

Learning Objectives:

1. Learn some of the common problems we encounter in landscape and the common ways to get around these problems
2. Discuss the misunderstandings, e.g. volcano-mulching and their effect on the landscape designs, as well as the potential benefits of the design.
3. Demonstrate why soil oxygen is the real limiting factor and how fast it start to affect the plant lives.
4. Learn some new methods and technologies that can not only address and alleviate the problems, but also make landscape designs better suited for the beautification and the long term benefits of green infrastructure.

1 Approved CEU/PDH for ISA and LACES