So, are you trying to monitor the urban trees?
Want to track mortality or survival rates?
We're going to review some fundamental components to urban tree monitoring,
recording mortality status.
Isn't that easy? Just call the tree alive or dead.
Not quite. You may think a tree is either alive or dead,
but often it's not that simple. Things are a bit
more nuanced and that's what we're here to talk about.
So trees have this amazing ability to bounce back
after near-death experiences. So we have to be
careful when recording mortality information. Trees can be
almost dead but actually still alive, and they may seem dead in one year and then
come back to life in another year. Trees can be cut down to the stump but
have new sprouts. And that's why we need to carefully
consider how to record mortality status. The mortality status variable is
considered a core part of any project that seeks to monitor change over time
in our urban forests. Recording mortality status accurately is
absolutely critical to urban tree monitoring studies.
If you want to understand the mortality of trees that you plant or manage in a
city town or suburb, mortality status should
be the centerpiece of your data collection.
Ah yeah, I've heard some planting programs reporting mortality or survival
rates as a way of talking about the performance of their programs.
Um-hum. Some other practical applications of mortality studies
are to figure out why the trees have died, generate a list of trees that need
to be replaced, or give feedback to a property owner.
Each of these objectives depends on accurately recording the status of a
tree. Tree managers might also be doing a repeat
inventory of all the street trees in a particular city or neighborhood, and
wondering whether new plantings balance out trees that have been lost.
All right, you've convinced me that this is an important part of urban tree
monitoring. So what do I need to record?
Great question. Let's get into the different categories
within the mortality status variable.
The mortality status of this tree is alive,
but that's fairly obvious because it has green leaves.
So what about trees that are extremely unhealthy and and might even look like
they're dying? Oh they're not dead yet.
Extremely unhealthy trees such as those with no leaves but live buds
or green tissue under the bark, are included in the alive category.
But I thought that we could lump dead and dying trees together?
In our urban tree monitoring field guide we purposefully consider
dying trees to still be alive. This is because sometimes those very unhealthy
trees can bounce back in the next season. And, because trees are not categorized as
standing dead until they are all the way dead.
We can call a tree standing dead when it has no green leaves,
no like buds, no green tissue under the bark.
Standing dead trees are also supposed to have an intact trunk
and be more than a foot tall. Shorter than a foot, we call it a stump.
So, what would you say we have here?
This tree has a dead trunk and branches but it has a few green sprouts
shooting out from the base of the tree. We would still record this
as standing dead, because if the sprouts continue to grow
they will form essentially new trunks different from the ones we've been
tracking to this point. A new trunk means a new tree
which means a completely new record in the database. Well, this one seems easier
it's a stump. Correct, now you're getting it.
Okay, but what about trees that are missing or removed?
I should call those dead right? That's a great question.
We're actually not going to call missing trees dead. Let's say you're doing a
monitoring project and checking on trees from a planting program.
You've got the address and other location information that's telling you
there should be a tree in that spot. So, two categories can apply here.
It might take some sleuthing to figure
out if the tree was removed or never planted.
Both categories require that there's no sign of a stump
or a standing dead tree. If a tree has been removed
since the previous observation at that spot you can categorize it as removed.
If a tree was designated to go into the ground but never made it,
it's listed as never planted. For example, maybe this address was on an
original planting list but on the day of the planning the homeowner didn't want
that tree, or maybe there was an unexpected problem with utilities under the ground.
A final category in mortality status is
unknown. Sometimes trees are inaccessible due to
property access or construction, or maybe the location information is not
good; it's hard to tell which tree is part of the study.
Careful notes should be taken to explain what happened so that the project
supervisor can decide how to deal with this tree when it comes time to analyze
the data. Okay, I see recording mortality status
involves a lot more than simply a dead or alive. What are all those categories again?
Oh this is a test! the categories are
alive, standing dead, stump, removed, never planted
and unknown. Okay let's recap.
In this short video we touched upon only one element of urban tree
monitoring: recording mortality status, but there's so much
more to learn if you want to run your own monitoring project.
For more tips check out the links below and thanks for watching