Wednesday, August 8, 2012

Compacted Soils

There is no question that trees growing in compacted soils generally won't grow as well as trees in a lower bulk density soil.  Compacted soils adversely affect root tip elongation, affect gas exchange, and disrupt water availability.

In the latest edition of Arboriculture and Urban Forestry a study performed by Barbara A. Fair, James D. Metzger, and James Vent  concludes  water availability in compacted soils may be the limiting factor for tree growth.  They found carbon dioxide levels were 5-18 times higher in compacted soils compared to atmospheric concentrations, while O2 concentrations were similar to atmospheric levels despite density.

This tells us that water management is increasingly important in our urban landscapes.  Often tree owners tell me they irrigate, but the irrigation is usually too little or way too much based upon the site.  Getting the correct amount of water in compacted soils can be a tricky code to break.  Think of a line of plants along a slight grade change.  Many times you will see the trees on the high side parched for water, while the trees in the low area are sitting in saturated soils well above field capacity.