So Helena, I hear you want to monitor some trees.
Yes, but I could really use some advice. I want to track the trees in my city for
survival and growth but I don't know where to start.
Well you've come to the right place.
Urban tree field monitoring can serve several types of management and research goals.
And you know, the first question you need
to ask yourself is what are the goals you want to have for your monitoring?
Let's say you're trying to evaluate a program performance for tree planting.
Tracking those trees through a
particular program can produce information about its survival,
growth, health and help you understand how your program is doing.
You know another potential goal for monitoring might be to figure out what
ecological and social factors help predict tree mortality, growth or health.
Doing that kind of analysis with long-term monitoring can
help to identify trees that tend to have more health problems or higher mortality.
You know, some programs do tree monitoring with the objective to engage
local communities using volunteers to collect data.
That's called citizen science right? You got it.
So, taking a citizen science approach might not necessarily be easier
or cheaper than using paid crews, but it certainly can be a great strategy for
engaging your community. You know, municipal arborists might also
be interested in repeating street tree inventories which are then used to
manage pruning cycles or tree risk. Researchers can also use tree monitoring
to get the real world empirical data for population
projections and ecosystem service models.
I've used a program where you can input
trunk diameter and species, and it spits out how much carbon the tree will store
after a year, which is pretty interesting. Yep, I agree and so if you're monitoring
how the tree population changes over time, you can input that
information into ecosystem service models to see how the benefits are
changing over time too.
Another goal for urban tree monitoring
is for pests and diseases in our urban environment,
which if you're looking out for them can provide valuable early warnings about
threats both to our urban but also to our natural forest ecosystems.
And last but not least, monitoring can be
used to evaluate experimental tree plantings.
For example testing the performance of a new species,
new cultivars or responses to changing climate conditions.
Okay great, thanks for that overview. Now that I know what kind of projects have
benefited from long-term monitoring, I want to start monitoring our planting program.
Well, what's your goal? You know if you
have a goal it'll help
you figure out what variables you need to collect and whether or not your
project should expand beyond just collecting those basic variables.
Great question. So I'm really interested in assessing what factors are related to
young tree mortality outcomes for a planting program in my city.
Is there something in the built environment or socioeconomic factors
that impact what happens to trees? So lots of studies have been done on this topic.
The key thing for designing your monitoring program
is to align your variables collected to your goal.
Every variable should have a clear purpose related to the project goals and data
analysis plans. We should avoid collecting an exhaustive
set of variables, that laundry list because it honestly
can be counterproductive. Yeah I know. I tried that before and we
had way more data than we needed, it took us way too much time.
Exactly.
I mean for your case in addition to collecting basic tree
information such as mortality status, location,
and trunk diameter you might want to also collect extra tree
variables like height and crown width or extra site variables like the size of
your planting pit. It's starting to sound like this project
is going to take a lot of time and effort.
I wonder how much time our staff will really have to collect this data?
You know that's a really important consideration. You'll need to estimate
the time required for field work and transportation.
Collecting just that bare minimum, what I mentioned before, like mortality status
location, species, trunk diameter and site type,
approximately takes three to five minutes per tree. However once you start
adding up more tree measurements in there
like site observations, field time per tree will add up.
And I have to point out that three to five minutes per tree does not even include
the transportation time. If your trees are scattered all over the
city or you got bad traffic, your field time could dramatically increase.
Okay, so what if instead of trying to track the trees from our planting
program, I wanted to track all of the street trees in our town
to see if we're gaining population.
Lots of cities and towns are trying to figure that question out to see if new plantings are
outweighing the losses from tree deaths and removal.
So a tricky part here is figuring out how to define "tree".
There is no broadly accepted definition of tree
in botany or forestry. It's best to pick out a definition ahead of time
and stick with it to avoid confusion in the field.
Otherwise crews might not be clear about what trees are in
or out of your study. For example, maybe you limit your study to one tree whose
trunks are bigger than one inch. Or maybe you focus on street trees and
you define that as only streets in sidewalks or it could only be trees
with a fixed right-of-way distance from the road.
Huh, I never thought that the word tree could be so complicated or the meaning
of street tree. Yeah, it seems straightforward but
sometimes it's not and it's an important thing to figure out
at the start of every project that you do.
That way you're comparing apples to apples with each tree census.
You know, another important issue is to consider right from the start do you have a good
baseline record already. What are baseline records?
So baseline records are that first set of tree data relevant to your monitoring project.
It's that starting point from which all
comparisons will be made going forward. For what you're going to be doing,
the baseline data is essentially the tree planting records. If you're doing a
street tree inventory then maybe your baseline is that first inventory.
Good baseline records are essential for that data collection.
You should definitely spend some time inspecting those records to ensure that
they can be used for monitoring. Oh, I see, yes well we have the exact date
that each tree was planted and we recorded the species. It's good you have
that actual date rather than like a year or a season. Programs interested in
tracking population cycles may also really want the record of the tree
removal date as well. As far as species go
make sure that you're recording consistently with each tree species or
cultivar recorded in the exact same way. Yeah, I've already spent some
time cleaning up our program records. Sounds like that will help with
monitoring too. Definitely. So, another question for you, do you know
what kind of data system you might want to use?
I think since we'll have just two or three permanent staff members
collecting data and we already have tablets, we would probably use those.
And our city also has tree inventory software, but if we decide to do citizen
science monitoring with many volunteers, we might use paper data collection.
I'm not sure yet. There are so many software packages for urban tree
inventories but they're generally not designed for longitudinal data
collection, meaning recording information on the
same tree over time. So, you need to think about selecting one
that works for your purposes. There are also pros and cons to using
paper data collection. Best resource? Check out our urban tree
monitoring resource guide for more information.
Looks like I have some homework to do. Thank you so much for walking me through
these initial steps. Happy to help, that's why we work on the
urban tree monitoring project. Thanks Miranda, and where can I go for
more tips on how to set up a monitoring project?
You know, we have these great links for more information. We've got tips and
references in our resource guide as well as in our field guide we have
information about field methods. Have a great time monitoring your trees.