[CANUFNET] FW: Tree Mortality Information Bulletin - Version 2

[Barwinsky, Martha]

The information in the bulletin is very useful but I also agree with
Anita's comments. There needs to be more emphasis placed on the urban
conditions in which the trees grow that predisposes them to secondary
problems and subsequent decline. Our challenge is to provide the best
growing conditions possible for the trees (under our influence) to
withstand the weather extremes (beyond our control). For example, the
increased use of de-icing salt, poorly located trees (even though they
were once in a good location until the area around them was further
developed...), and poor soil conditions (re: soil quality and soil
volume) wreaks havoc on many of our trees growing on regional streets in
Winnipeg. There are only so many years of extreme weather conditions and
secondary pest problems that trees growing in these urban conditions can
tolerate before they really decline.

Martha Barwinsky
City Forester
ph: (204) 986-3701
 

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-----Original Message-----
From: canufnet-bounces at list.web.net
[mailto:canufnet-bounces at list.web.net] On Behalf Of Anita Schill
Sent: June 29, 2010 9:28 PM
To: Canadian Urban Forest Network
Cc: 'Keith Anderson'
Subject: Re: [CANUFNET] FW: Tree Mortality Information Bulletin -
Version 2

Sorry I don't buy into this. Trees are being planted in soil that is not
conducive to plant growth to say it nicely. Trees are also being planted
too deep and developing girdling roots. Trees and the soil they're in
are being coated with de-icing salts. Trees are not being watered. The
bulletin neglects to add that in September only 2mm of rainfall was
experienced in Calgary. Did people water their trees? 

"Why do some plants on the same street, even within the same species,
have no problem surviving extreme weather conditions while others don't?
As a living organism each one will react differently to environmental
conditions - it could be genetics, location, injury, stress or even how
it was maintained that contributes to how well it survives. Even plant
scientists who conduct research into plant hardiness find the answer to
this question challenging."

This is the key statement - location, stress, injury, maintenance......
isn't that what our industry is about?  Weather is a small part of the
picture. A healthy tree will get stronger when it is exposed to weather
challenges; a tree that is already in decline for reasons that ARE often
discoverable will die a few years earlier than it would have anyway.
Anita Schill
________________________________________
From: canufnet-bounces at list.web.net [canufnet-bounces at list.web.net] On
Behalf Of For Trees [trees at fortrees.ca]
Sent: Tuesday, June 29, 2010 7:13 PM
To: 'Canadian Urban Forest Network'
Cc: 'Keith Anderson'
Subject: [CANUFNET] FW: Tree Mortality Information Bulletin - Version 2

Here is a LANTA bulletin that has been circulating relating to the topic
of winter kill on the prairies.

[cid:image005.jpg at 01CB17BF.1A292E90][cid:image006.jpg at 01CB17BF.1A292E90]
Gerard Fournier
Board Certified Master Arborist #PR-0130BT
Tree Canada Community Advisor-Southern Alberta

President
For Trees Company Ltd.
1-877-390-TREE (Alberta toll-free)
http://www.fortrees.ca<http://www.fortrees.ca/>



From: Cheryl - LANTA Administration [mailto:admin at landscape-alberta.com]
Sent: June-29-10 10:34 AM
To: Cheryl - LANTA Administration
Subject: Tree Mortality Information Bulletin - Version 2

To: LANTA Members:

Below, and attached printable pdf, is an updated Tree Mortality
Information Bulletin. We have built upon the first Bulletin sent last
week and now included more details about plant dormancy, the effects of
weather and weather data from across Alberta during the time in
question.  We hope you can use this information when discussing the
subject with your clients. (Thanks to all members who provided feedback
to the first bulletin - much appreciated.)


PLANT INFORMATION BULLETIN - HIGH MORTALITY IN URBAN TREES

Urban tree and shrub mortality rates in Alberta have spiked this year
due to a combination of weather events that occurred between September
2009 and May 2010.

What happened to cause such an increased loss of plants? The answer is
not an easy one to explain as there are many factors to take into
consideration. Plants are complex organisms and a basic understanding of
their physiology is needed before an explanation as to why so many
"prairie hardy" plants did not survive the 2010 spring season.

The life of trees occurs in cycles. In early spring, as days begin to
get longer and the weather is warmer, the tree is pulling all of its
energy together for growth. As the weather continues to warm the tree
begins to grow rapidly, taking advantage of the long days and optimum
sunlight. For most trees, growth ceases by August. From this point until
fall, the objective of the tree is to prepare for winter. During fall, a
tree stores up food and energy reserves - everything that is needed for
next spring's growth. Between fall and spring is the period known as
dormancy.

What is dormancy? It is a period when the tree's physical life cycle is
temporarily stopped to help the tree minimize metabolic activity. Plants
prepare themselves for dormancy by going through a process termed
"hardening off," which is triggered in plants by the gradual decrease in
day-time temperatures and the length of daylight (photoperiod). Within
the plant, chlorophyll production slowly decreases, antifreeze proteins
develop and leaves prepare to drop (abscission). This is known as
predictive dormancy and occurs when an organism enters a dormant phase
before the onset of adverse conditions.  As you will read later,
changing the environmental conditions around the tree may alter the time
of year when it goes into dormancy.

When spring approaches, dormancy begins to come to an end and the
physiological process is reversed. Metabolic activity begins again
triggered by lengthening daylight and a gradual increase in temperature.

It is the period between fall and the following spring that is of
interest in the examination of tree mortality, especially the period
just before the onset of dormancy and the period when dormancy is broken
in spring.

As mentioned above there are many factors that influence when a tree
enters the dormancy period, one of which is temperature. (Other factors
may include stress and too much water/fertilizer applied prior to leaf
drop.) In an average season the reduction in temperature during fall
(September/October) is gradual. If, however, temperatures are above or
below 'average' this may have an impact as to when and how well a tree
enters its dormant period.

Temperatures across Alberta in September 2009 were well-above average
and this would have had an influence on some plants not fully "hardening
off" before the cold weather arrived. In other words, the onset of
dormancy would have been retarded.

For this bulletin, temperatures were reviewed in Grande Prairie,
Edmonton, Red Deer, Calgary and Lethbridge. The highest temperatures
recorded for September 2009 were: Grande Prairie 28C, Edmonton 33C, Red
Deer 33C, Calgary 32C and Lethbridge 33C. The mean maximum temperature
in these five locations was 6.6C above the combined average of 13.6C.*

The above average warm weather continued into the first week of October
2009 and then in all locations plunged to well below 0C. The sub-zero
temperatures lasted for a week and were accompanied by strong winds -
combined this is called an advective freeze. The lowest temperatures
recorded during this period were: Grande Prairie -9C, Edmonton -10C,
Red Deer -14C, Calgary -16C and Lethbridge -17C. The mean minimum
temperature in these five locations was -7.2C below the combined average
of +5C.*

The late onset of dormancy, caused by late fall warm weather and the
sudden and extreme drop in temperatures will have had an impact on the
physiology of some plants and may have caused extensive tissue damage.
This is called Consequential dormancy and occurs when organisms enter a
dormant phase after adverse conditions have arisen. This is what, in our
opinion, we believe happened in October 2009 - as indicated by leaves
frozen in-situ on some plants. The result of the tissue damage was not
seen until this past spring, when many plants failed to break dormancy
as they normally would.

A compounding factor in some tree & shrub mortality are adverse weather
conditions during late winter and early spring periods when plants are
coming out of dormancy. Plant growth in spring is stimulated by
lengthening daylight hours and slowly increasing temperatures. If
temperatures rise too quickly and too early in the dormancy cycle, some
plants may begin cell growth too soon. If temperatures drop below
freezing after cell development begins, tissue damage is therefore
possible.

Weather records indicate that this did happen in most locations this
past spring, although it is difficult to know whether this is when the
cell damage occurred or whether it was during the fall conditions noted
above. Regardless, when combined with all these environmental
conditions, many plants were unable to survive and leaf-out this spring.

Another contributing cause of tree mortality is drought. Although 2010
has so far been wet, successive dry years since 2001 have taken a
significant toll on a number of tree species throughout the province.
Many drought-stressed trees (ash in particular) have also been attacked
by an insect called the cottony psyllid (Psyllopsis discrepans) and this
has further contributed to some tree mortality.

Why do some plants on the same street, even within the same species,
have no problem surviving extreme weather conditions while others don't?
As a living organism each one will react differently to environmental
conditions - it could be genetics, location, injury, stress or even how
it was maintained that contributes to how well it survives. Even plant
scientists who conduct research into plant hardiness find the answer to
this question challenging.

Please contact your local garden centre, contractor or plant supplier
for more information.

* Weather data provided by Weather Underground


Landscape Alberta Nursery Trades Association (LANTA)
200, 10331-178 Street, Edmonton
Alberta, T5S 1R5 Canada
Phone: 1-800-378-3198. 780-489-1991
Fax: 780-444-2152
www.landscape-alberta.com<http://www.landscape-alberta.com>

2010 Green Industry Show & Conference
Edmonton Expo Centre
November 18th & 19th 2010
www.greenindustryshow.com<http://www.greenindustryshow.com>

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