Forest Ecologist Answers Tree Questions

I'm Dominick DellaSala, forest ecologist.

Let's answer your questions from the internet.

This is Forest Support.

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@unrulyObnoxious asked,

I wish there actually was a mother tree

like they showed in 'Avatar.'

I watched that movie too

and I was fascinated by it.

The mother tree was the central tree

that connected everything in ecosystems

in very vivid colors.

And I had a similar experience

when I was in the Borneo rainforest.

The fungi were all lit up in bioluminescent colors.

You didn't need a flashlight

to walk through that rainforest that night

because it was so colorful.

And those trees are very unique

to the Borneo rainforest.

When they are cut down, they don't come back

because they have very specific pollinator relationships.

So @gapher9 asks,

How do forests regenerate after fires naturally?

Seeds blown in from outside the fire zone?

One of the fascinating things about forest is

after a severe fire that kills all the trees,

it's not an ecological catastrophe.

In the ashes, they will release cones,

like the serotinous cones of Lodgepole pine

that need intense heat

to burst open their seed cones.

There are trees that will sprout after a fire,

like a Madrone.

They will take advantage

of this nutrient-rich environment

to release their seeds in a seed rain

so that their progeny will develop into the next forest.

So life and death are both important in a forest

and are both needed

for the healthy systems to function.

LeoPsy asks, What did ancient forests look like?

If we go back in time to the period of the dinosaurs,

trees were a lot different.

They were gymnosperms.

They weren't angiosperms.

So the flowering plants

had not really developed at that time.

The monkey puzzle tree is a good example of that.

It has all kinds of needles on it.

The story is that a monkey looked at the tree

and was puzzled by how it was gonna climb that tree

with all those needles on it.

@PerfectDay2Play,

How do trees access the internet on a camping trip?

They log in to the wood wide web.

Well, there is some reality to that,

even though it's a funny, corny joke.

Trees are connected through their mycorrhizal networks.

These are fungi that attach themselves

to the roots of plants

and allow them to communicate

through chemical interactions.

There has been some really interesting work done

by scientist Suzanne Simard,

where she actually described connections

on the root systems of plants

that allowed them to communicate chemically to one another.

And the closer the relationships

between mother and progeny,

the more connected the underground network was

in that fungal system.

So trees have a lot of different ways to communicate.

When there is an infestation coming,

they will release pitch that will trap insects

that are landing on the surface of the tree trunk.

And that will be a signal

to other trees in the forest

that they're under attack

so that they can prepare their defenses.

@richardbis asks,

Why do we have so many forest fires in California?

Seems like we have a lot there?

Fires have been burning in California for millennia.

If you're living in Southern California,

chances are you're experiencing fires during high winds,

the Santa Ana winds.

That will propagate fires through chaparrals, shrubby,

grassland areas.

In other areas of the state,

you're going to get fires in forests

that by and large are very beneficial

to these ecosystems.

They need fires to rejuvenate themselves

and to allow their seeds to develop into larger trees

and forest vegetation over time.

There are unfortunate consequences

when fires spill over into communities

and there are ways that we can prepare for that.

The way to do that is to make sure

that your roof is a composite or metal

that's not gonna burn.

Make sure that your open vents for ventilation

have proper screens on them.

Make sure that you're clearing a defensible space

around the home itself out to 50 to 100 feet

so that your flames will not carry from the wild areas

onto the roof and get into the vents.

@zentreya asks, My tree exploded.

What going on? [chuckles]

There is a tree that sort of explodes.

It's called the sandbox tree

and its leaves and its spine are toxic to humans.

And when it releases its seeds,

those seeds can be projected at high velocities

and cause a lot of damage to people and animals.

@TwitmoPro says,

What the [beep] do you know about forest management?

Trump is exactly right about cleaning up debris

and fallen trees from the forest floor.

It's really very simple.

Well, no, it's not simple

and Trump is not right

in cleaning up the forest floor.

This is not just going out there with some rake

or the forest floor that get the leaves off the ground.

What Trump is doing is clear-cut logging

that actually will make fire more prevalent

in those forests.

There's about 760 million acres of forest

in the United States,

most of which are under private ownership.

There's about 190 million plus acres

of the national forest system.

They are not all protected like national parks.

Most of them are open for a whole variety of uses,

including logging.

When you log a forest,

a lot of that logging slash,

the twigs, the leaves are left on the ground.

Some of it's treated,

but a lot of it's left on the ground

and that provides the kindling

for these fast-moving fires.

So the Trump executive logging orders,

which is directing the federal agencies

to do more logging,

is actually gonna make them more prone to forest fires

by taking out the big old trees

that are the most fire resistant parts of the forest

and leaving a lot of flammable logging slash behind.

Eric Hovind asked,

What do tree rings really prove?

Well, tree rings are a living record

of the tree's growth patterns.

So this tree is about 30 years old

when I count up all the rings.

The tighter the rings are on this,

it means that the conditions for growth during that year

weren't as good.

It might have been a drought.

The wider the rings means that the tree was doing better,

the conditions were more favorable,

and the living part is the outermost section

that has the xylem and the phloem,

which is the tree circulatory system

that is passing nutrients

to different parts of the tree and water.

The other thing we can note from this

is the bark of the tree.

So the bigger the tree,

the more bark it will lay down.

The more insulated it is from most forest fires.

If there was a forest fire, there will be scars

that have been laid down across the rings

so that you can actually determine

what year the fire was occurring in

that affected this tree.

So Pundit Review ask,

Is Smokey the Bear full of [beep]?

Nine out of 10 wildfires are caused by humans.

#SmokeThis.

When you add up all the fires across the nation,

roughly nine out of 10 have a human cause to them

and it's associated with high road densities,

population centers that have access to wild areas

that can cause a fire accidentally.

Let me address the second part of this question.

Smokey Bear would appear in posters and logos

and his motto was, Only you can prevent forest fires.

And it was really targeting campfires,

but then it got blown out of proportion

and became the symbol for the Forest Service policy

to put out every fire start by 10 AM the next day,

which is destructive and catastrophic to ecosystems

that need fire to balance out their growth

and rejuvenation and aging processes.

HairyAwareness asks,

How much of a dent in climate change

will MrBeast's 20 million trees project make?

Planting trees is a good idea in the right places,

but it is not going to make as big of a dent

in the climate crisis as protecting our existing forest,

especially the old-growth forest.

So an old-growth forest is a biological cathedral.

The tall, wide, big trees in those forests

are really important habitat

and they also represent

the accumulation of atmospheric carbon

that you see in their trunks.

There's no replacing those trees

by planting the little seedlings

that will take hundreds of years

to start accumulating that carbon.

@oliverhangout asks,

I have to do a presentation in biology

and I have to present nine slides

about the [beep] boreal forest.

Like what the [beep] is a boreal forest?

They are cool forests found in places that are very cold.

As you can see, the green area on this illustration

just below the Arctic Circle is where these forests occur.

They have all kinds of different tree species

growing in some extreme conditions

where we get a lot of snowfall.

You'll get conifer trees like pines

and you'll get some hardwoods like aspens.

They are the places where most of our migratory birds

wind up during the breeding season.

The boreal will support up to a billion birds

during the summertime.

There are other kinds of forests

that exist around the planet.

The next latitudinal zone are the temperate regions.

In the United States, most of our forests are temperate.

If you go to the Appalachian Trail

or the Pacific Crest Trail

and you're hiking through those areas in the forest,

you're in a temperate zone.

The temperate forests have all kinds

of really interesting tree species.

They're a mixture of oaks, conifers, and aspens.

It's really quite biodiverse.

And there's a subportion of the world's temperate forests

that are actually temperate rainforest.

An example would be the Olympic Peninsula in Washington

or the Tongass rainforest in Alaska.

The trees are enormous.

They grow to over 200 feet tall.

They are as wide as this table.

Those rainforests are absorbing so much carbon

and giving so much habitat to the salmon

that will use those rainforests.

They'll come up the streams and spawn

and then their carcasses will be eaten by eagles.

The eagles will poop out their remains

and that will be fertilizer for the rainforest trees.

Now, if we get further south into the Southern Hemisphere,

now we're talking tropical rainforests,

which have all kinds of unique tropical species

in a very wet and hot environment.

If we go over to Europe

where there are only small fragments of rainforests

like in the UK, the trees are much shorter.

They only grow to maybe 30 feet tall

instead of 300 feet tall,

but they're still rainforest

because they're blanketed by rainy conditions.

They're just different in terms of the height of trees

and the type of tree species there.

Here's a question from Quora.

Is it true that there is a forest

that is a single living organism?

Arguably, forests are interconnected superorganisms.

If you look at an aspen forest,

it could have originated from a single aspen tree

that would send out its below-ground runners, its suckers

that would then come up through the soil

and be an entire group of trees from the single organism.

Spontaneouslypiqued ask,

How do forests return so quickly

to the Northeastern United States

which had been almost completely deforested?

The Northeastern forests were almost completely deforested

over 100 years ago

and that led to almost the entire elimination

of old-growth virgin ancient forest.

However, there's been a century or so

of no logging activity in some of those forests

that are now maturing

and returning to older characteristics.

So most of the forests that you get in the Adirondacks

or the Appalachia region

had been logged over a century ago,

so they're really secondary forests.

And that's the beauty of forests.

If we allow them to recover,

if we don't log them the second time through,

they will develop those attributes

that make them uniquely old.

PrivateTumbleweed asked,

Is it [beep]

that there are more trees on the planet right now

than there has ever been in all of history?

Well, yeah, it is [beep].

We've been deforesting the planet for thousands of years.

The scale of that deforestation has increased.

And so currently we're down to about a third

of what the forests were on the planet

before all of this widespread deforestation had taken place.

And of that group,

only about 28% are considered primary forests.

Those are forests that have never been logged.

So that's why you can't just say we're planting trees

and just counting that there are more trees we planted now

than ever in history.

It's because the quality is really important.

You can't plant an old-growth forest.

It takes centuries for those forests to develop.

@MatthewEGunter asked,

Do rainforests create rain

or does rain create rainforest?

It's actually both.

Trees are remarkable because they take in rain and use it

and then they go through evapotranspiration

where water evaporates, returns to the atmosphere

and becomes the water cycle again.

So the two are connected.

And so when rainforests are cut down,

they can actually change the regional climate.

But when that rainforest is removed,

we see more droughts.

@seahaze55 asked,

Are they still burning the Amazon rainforest down?

So this is a pretty general map of the Amazon rainforest.

You can see in green color areas that are still intact.

They haven't been logged.

And then you see these other areas in orange

that represent deforestation that has occurred.

Rainforests are being cut down, burned,

and cattle are then grazed over the area

and that then triggers these droughts

that we're now seeing in the Amazon Basin

because we don't have the return of water

to the hydrosphere and the atmosphere.

So if that keeps happening,

the Amazon will eventually flip

into a drought-stricken savanna

and lose all the rainforest benefits.

That could happen within the next couple of decades

depending on the speed at which climate change progresses

across the planet.

@Jamesrus42,

Without cheating,

in what country is the oldest forest in the world?

Approximately 180 million years old.

Well, I think of the Danum Valley,

which has trees that are hundreds of millions of years old.

The trees are called dipterocarps.

They can be over 300 feet tall.

They're also the home of the orangutan,

which is an endangered animal

that will raise its family

in the upper canopies of these rainforests.

@wya42wallabyway asks,

Trees suck in CO2, right?

So where does it go?

Do they just hold their breath?

Through the miracle of photosynthesis,

they will absorb carbon dioxide.

When it's absorbed by the tree, it makes its food.

And like us, when we have too much food,

we store it.

A tree that is 300 years old,

like a Sitka spruce in Alaska's rainforest,

has been out there absorbing carbon for centuries.

That carbon has been stored in its trunk and in its roots

and it's really important for cooling down the planet

during the current climate crisis.

@MacabreSalmon, I've always wondered,

why do pine forests smell of air freshener?

Actually, air freshener smells like pine forest.

So trees will produce a terpene

when they're under stress.

It's a chemical that you smell in the forest

when it's at a certain level.

The really interesting thing about this is

that there are certain beetles

that can detect those terpenes

and they will continue the process

accelerated towards the tree's death,

which is not a bad thing in the forest

because as that tree dies,

it's creating habitat for all this wildlife.

And as it dies and falls over,

it is being recycled into the nutrients in the soil.

@carterkr, I'm writing an essay

on anthropogenic natural disturbances

on a forest ecosystem,

which is a fancy way of saying things that [beep] up trees.

Well, things that really are not good for trees

are clear-cut logging.

When we go in there with chainsaws

and we kill all the trees,

that causes a major unnatural disturbance

to the forest ecosystem,

which causes all kinds of problems for wildlife habitat,

which releases carbon to the atmosphere

because the trees are no longer storing it.

And it also can damage water supplies

because you need to have a road system

for most of these places that are doing logging

and those roads are funneling

all kinds of sediment pollution into streams.

And when there's a lot of trees dying in the forest

like is happening in the Rockies,

that release of chemicals

will trigger an outbreak of insects,

like in this case the beetle outbreaks

that then kill the trees

and turn the forest a kind of red coloration

as the needles are dying in those forests.

Trees also will experience natural mortality agents.

The American chestnut is functionally extinct in the wild.

There's a fungal pathogen

that is very specific to American chestnut trees

and kills them before they can mature

and become part of the old-growth forest.

@MattPowersSoil asks,

Do you know the layers of a forest?

Yes, I do know the layers.

Let me walk you through the different layers

of a tropical rainforest.

So if you're going to imagine yourself on an elevator

and you start at the top level, the penthouse,

the emergent trees,

then you move down a couple of floors

and you're in the canopy of the forest

and that is where most of the trees are.

Below the canopy you can get into younger trees.

They're the trees that have been suppressed

below the dominant canopy.

Sometimes there's a tree that dies creating a gap

that will then result in a race to the top

as plants try to fill that gap in,

taking advantage of the nutrients and the light levels.

And then we've got even more complexity

on the forest floor.

You kind of think of that as the basement of the forest.

There's all kinds of different species

and mycorrhizal fungi in some of these forests

that add to a layering effect

that we see in these older forests.

@MentalSymphony ask, Quick question,

why do trees stop growing at the same height?

Me, what kind of high ask question is that?

Trees will stop growing at a certain height.

Really good example in California is the coast redwoods.

Those trees can get to over 300 feet tall

and they stop growing

because they can't get all the nutrients and the water

up to the top of the tree canopy.

So they will compensate for that

by living in the fog belt.

And that fog belt surrounds them in moisture

so that they don't have to figure out

how to get all that water up to their top

because they've already got water there from fog.

And so the way plants get water and nutrients

all the way up to their stem

is they have what's called the xylem and phloem tissue.

It's like a series of tubes that allows them

to get that water up all the way to their stems

and out to their twigs and their branches.

And it's remarkable.

It's like the tree circulatory system.

Here's a question from Quora.

What the difference between a tree farm and a forest?

I consider a tree farm

where all the trees are planted in rows like a crop,

a monoculture, a Franken forest

that are grown mostly for timber yield.

A forest is a living ecosystem.

It's trees interacting with other vegetation,

with the soils, with wildlife.

The trees are different ages.

They're different sizes.

When you go into a Franken forest,

the trees are all the same age.

There's hardly any structure.

There's very little habitat.

So you lose all of those special benefits

that we get from the natural forest.

@JSuperswan asked,

How do controlled burns work?

Well, they're not really controlled burns.

We like to call them prescribed fires.

And so what managers of a forest might do

is they might light a fire under certain conditions

so that they can clear the understory

in a low-intensity burn

and reintroduce fire to ecosystems

that need frequent fire in a low-intensity way.

@Ryderfangfang is asking,

Do trees compete with each other in nature?

Trees will compete within and across species.

When trees come back after like a natural disturbance,

the seed rain that happens

will give you a lot of tightly spaced trees

that are all competing for the same limited nutrients

and light levels in a forest

and they'll eventually sort it out

because there are winners and losers

in competition battles like this,

eliminating those that are less fit

and less adapted to that site.

Some plants will release a chemical called an allelopath

and that will kill surrounding vegetation

so that plant will prosper

and out-compete its competitors.

So those are all the questions for today.

Thank you for watching Forest Support.

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