Your thoughts on these statements please!!

Water Conducting Tissue Types (WCTT): Angiosperms (which are most broad leafed and deciduous trees) have basically two different types of wood anatomy, diffuse porous and ring porous. The deviation between wood structures relates to the diameter of the xylem vessels (water conducting tissue):

Diffuse porous: Has vessels throughout the growth increment of approximately equal diameter, and are spaced about equal distances from one another.

Ring porous: Has very large diameter vessels early in the growth increment and much smaller diameter vessels later in the growth increment.

Significance of porosity types: Researchers point to many components which will affect the moisture uptake of a tree. With a direct reference to ring and diffuse porosity of trees having a part to play in soil drying. The importance of wood porosity may not seem significant on its own, but it is "a piece in a puzzle". Ring porous trees due to the large vessels early in the growth increment, indicate that water uptake is much higher early in the growing season. This biological factor will have an impact on soil drying, if other contributory factors exacerbate the situation. However, some species do not exhibit a preference for a particular porosity type of wood. One such example is Ash. Whilst coniferous wood anatomy is very different from either diffuse or ring porous wood. There is no current available data to equate the significance of this wood type in terms of water transportation in relation to soil drying.

Paul H.

Reply to post by Paul H, on May 20, 1998 at 19:49:06:

I have one thought: large-bore conducting vessels in the spring (early increment) does not indicate greater water uptake in the spring. With additional, smaller-bore vessels coming later, this would indicate greater over-all conducting capabilities later in the increment unless the early vessels were plugged. peter t

Reply to post by Paul H, on May 20, 1998 at 19:49:06:

You wrote: Ring porous trees due to the large vessels early in the
growth increment, indicate that water uptake is much higher early in the growing season.

Why? I don't recall ever seeing anything stating this is true. It may allow faster translocation and a greater storage capacity for water, but absorption into roots is not dependent on vessel diameter of the conducting wood.

A lot of effort and research has apparently been done on the trees and their impact, but has work been done on finding other solutions, such Saturday soil modifications near structures?

Russ

Reply to post by Russ Carlson, on May 20, 1998 at 19:49:06:


I wrote it, but I didn't come up with it, that's why I am after your thoughts. I am simply looking for answers.

What is "such Saturday soil modifications near structures" ?

What difference is there between ring porous and diffuse porous in the differing species ability to abstract soil moisture, is one species greater at absorption than the other ? Or is it simply that faculatively deeper rooting species are more prone to be implicated in subsidence damage than the moderately or shallow rooting species and therefore do we discount the water conducting tissue types as "none proven" ?

Paul H.

Reply to post by Paul H, on May 21, 1998 at 14:36:14:

>>What is "such Saturday soil modifications near structures" ?

LOL! A typo. That should be "such *as soil modification" (my computer types "sa" as "Saturday")

Do you have information on rooting depth of the various tree species? I would have thught that the clay soils would inhibit deep rooting of most trees.

Sycamores and Tuliptrees (Liriodendron) are both diffuse porous, yet can absorb and translocate water as well as elms, a ring-porous tree. Although I don't have hard data, I think the available xylem thickness is a better indicator of translocation rates than cell structure.

Is there any correlation between rainfall/dryness patterns and the subsidence problems?

Russ Carlson

Reply to post by Russ Carlson, on May 21, 1998 at 15:56:36:


There is available data on the rooting depth of various species, following the storms of 1987 in the UK.

Drought conditions induce cracks within the clay component, allowing increased oxygen levels and it would seem that some trees have been found to produce a secondary ephemeral rooting layer at deeper depths (Oak being one example). Trees such as Beech, do not seem to display this characteristic and being more shallow rooted, often suffer from "drought stress." Lots more research of course, but that is true of most arboricultural studies. Soil moisture deficit analysis (UK MORECS - Meteorological Office Rainfall and Evapotranspiration Calculation System's data) do correlate with building damage claims even when trees are not involved.

Paul H.