Does Fill Really Kill?

[Guy Meilleur]

Recent issue of Journal of Arboriculture had an interesting piece of research done by Costello et al in California. One foot of fill packed down on the roots of cherry trees.

The result?? The trees with the fill did better than the trees with no fill! I mention this because last time a thread on filling came around there was a dogmatic majority (you know who you are) who insisted that adding dirt on top of tree roots was always an evil and fatal thing to do. A few of us said in some cases it helps the tree.

Read it and weep. Whaddya say now, guys?

 

[NickfromWI]

They only dealt with cherry trees? What if it's species specific. As long as the article doesn't try to generalize the results of that study to all trees, then good!

If fill needs to be added to the base of a tree for whatever reason, do so as gradually as possible.

love
nick

 

[ORclimber]

I agree with Nick. Redwood trees can grow adventitious roots after landslides. Some plants like rice can transport oxygen down stems to roots. Lots of genetic variables.

 

[John Paul Sanborn]

There was a small study a few years ago with white pine done in Siuth Carolina (I think) where they found sevearal feet of fill did nothing over the duration of the study.

The conjecture was that there was no prefill compaction, thuouhg that was not studied subsequently.

Then Smiley has shown with (Yellow?) pine that clearing the basal flair will show a marked change in vitality.

A phytoremediation study talked about at the WAA conferance was burtying willow and poplar 4 feet deep. They are rooting into the contamitnated soil and existing 4 years later (not thriving though).

IMO it is a long term issue and the very high increased risk of girdling roots will decreas the trees life expectancey.

In feild truals they have statistics, same in large plots. In a landscape we are lucky if the client is able to risk 3 palnts. We have to give the plant an optimal (not perfect) site to grow in.

When doing basal fill you have to let the client know that there is a good chance that you will be killing that tree.

 

[NeTree]

Sounds more like rolling the dice... I'd rather not fill and risk it.

 

[murphy4trees]

I think the type of fill is at least as important as the type of tree...
Most roots need O2.... Grading over the root zone with a heavy clay will reduce the O2 getting to the roots.... Most all the subsoil around here is heavy clay.... I hear the topsoil in some parts of Ca. is 8' deep....
Guy... you trying to start trouble again???

 

[jmchristopher]

Fill kills?

The assertion that "fill kills" is sometimes shorthand for saying that the whole constellation of neglect that accompanies fill also often includes compaction, basal trauma, soil contamination and God knows what else. If preservation efforts are led by some subcontractor up on a D3, results are usually poor as far as the trees see things.

 

[Kneejerk Bombas]

I haven't seen the article so I don't want to comment directly, other than to say there are a lot of variables involved which could explain the unexpected results.

Which edition was the article?

 

[tshanefreeman]

In addition to the comments already posted and discussed/disputed, one should also consider the type and manner in which the fill is distributed. 'Soil Science' teaches of the negative impacts of impermeable layers which are formed when differing soil aggregates are stacked on top of each other. An over-simplified example of this would be a layer of clay under sand under clay under silt. Such an inconsistent soil structure would dramatically hinder the infiltration of not only water but also oxygen. Each horizon has to reach its field capacity (must become saturated) before the excess moisture can infiltrate into the subsequent horizons below. As a result, burried rootzones may become stressed from lack of moisture or excess moisture, depending on the horizon that the rootzone occupies! However, if the existing soil is studied before hand, and care is taken in choosing a comparable fill, then the likelyhood of compounding problems will be reduced. As a result, I too feel as though there are far to many variable to simply state that fill will/will not have a direct influence on a tree's vigor!

 

[Sylvatica]

The cherries, well aware of their reputation as pain-in-the-neck trees, wanted to go against the common presumption and confuse us. They just wanted to be difficult and throw the research on its head.

Seriously though, there is a neighborhood in my area which was built from the late 30's to the early 50's. Surprisingly, as many mature trees as possible were left during construction. Many trees were welled with circular or square stone walls and over-graded 12"-24" deep with foundation backfill across essentially the entire rhizosphere. Pin, white & red oaks 30"+ Ø, eastern red cedars 24" Ø, big shagbarks. I wasn't there, but I'm sure they were marching all over the place with small dozers, spreading and grading. The trees are in great condition regardless.

Logic or at least common belief would seem to hold that gas exchange would have been altered to a harmful or fatal degree.

 

[John Paul Sanborn]

What is the soil type in the area, if it is sandy then it's less likely to compact.

 

[Ax-man]

Originally posted by Sylvatica


Seriously though, there is a neighborhood in my area which was built from the late 30's to the early 50's. Surprisingly, as many mature trees as possible were left during construction. Many trees were welled with circular or square stone walls and over-graded 12"-24" deep with foundation backfill across essentially the entire rhizosphere. Pin, white & red oaks 30"+ Ø, eastern red cedars 24" Ø, big shagbarks. I wasn't there, but I'm sure they were marching all over the place with small dozers, spreading and grading. The trees are in great condition regardless.

.

____________________________________________________

During the time period you stated, many construction activities were performed by gangs of laborers, rather than with the heavy equipment, that we see on sites today. Doing construction work with manual labor and the small equipment of the time would be a big variable in filling around trees, compared to what is in use today to complete the same tasks for construction of homes.

 

[ORclimber]

Originally posted by Mike Maas


Which edition was the article?

Jan. '04 Page 19

They were using Loam to fill 12". Young trees.