This course surveys the diversity, structure and functioning of California’s ecosystems through time and the ways they have influenced and responded to human activities and stewardship. Topics include ecosystem drivers such as climate, soils, and land use history; human and ecological prehistory of the state; comparative marine, freshwater, and terrestrial ecosystem dynamics; and managed ecosystems such as range, fisheries and agriculture in California. The course also emphasizes important skills to understand as a scientist or consumer of scientific information, including data collection, natural history, and writing.
Agriculture
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來自 University of California, Santa Cruz 的課程
Ecosystems of California
16 個評分
從本節課中
Drivers of Statewide Patterns
與講師見面
Erika ZavaletaProfessor
Ecology and Evolutionary Biology
[MUSIC]
I'm Erika Zavaleta and this is Ecosystems of California.
We're near Gilroy today on a agriculture field trip.
Now California is by far the largest agriculturally producing state in the US,
both in terms of its sheer production and
in terms of the diversity of what it produces.
Much of that agricultural production depends on a complex system
of water capture, transport, and irrigation.
So what does agriculture look like in California, ecologically speaking?
Three big ecological dimensions of agriculture in our state are one,
its effects on the state's cycling inflows of water.
Two, its effects on the state's land cover.
And three, its effects on the stocks and flows of fertilizer and
other farm inputs across ecosystem boundaries.
Agriculture uses about 80% of California's water,
that's down from closer to 90% in 1960s.
And in parts of the state where significant irrigation water flows back
into rivers, lakes, and groundwater, agriculture also affects the salinity,
nitrate levels and other features of water quality and chemistry.
With respect to land cover,
agriculture covers about 10% of California's land area.
And certain ecosystem types, like wetlands and grasslands, have had a especially
large proportions of their former area converted to food production.
For example, only about 5% of the wetlands that existed in California
in 1900 remain today, largely because they were drained for agriculture.
With respect to farm inputs, the worst period of pesticide pollution has passed.
And in the 1970s with the banning of DDT and
similar organic compounds, we lost a lot of the really serious impacts on
wildlife that were occurring in the state half a century ago.
But that kind of thing continues to remain an issue.
And one of the biggest and pervasive issues in the state continues to be
the effects of agricultural inputs of nitrogen and
phosphorous on both bodies of water and the atmosphere.
So, what does a managed agricultural system look like in California?
They're incredibly diverse.
And that's even if you look at one crop.
First, California's significant crops range widely,
from things like almonds to lettuce, grapes to alfalfa, and artichokes.
And they inherently look different because of the life histories and
ecological characteristics of the crops themselves.
Whether they're trees, vines, grasses or non-woody flowering plants, and
what part is harvested, for example.
But you can also take a single crop.
Strawberries are grown on large conventional farms like this.
And they're also grown on small organic farms like this.
With more natural vegetation, fewer inputs, less exposed soil, other
crops nearby, and different patterns of interaction with surrounding ecosystems.
It's that idea that we want to dig into some more on our agricultural
field trip today.
The idea of interactions between farms and the larger ecological landscape.
I'm here with Elissa Olimpi who's doing research in the agricultural landscapes
around Gilroy, California tonight.
Elissa can you tell us a little bit more about the farm that we're on and
what you're going to be doing tonight?
>> Yeah, well right now we are in Gilroy, and
we're standing in the middle of a riparian corridor, this is Carnidaro Creek.
And tonight, we're going to be setting up nets to catch bats,
as part of my research.
They're kind of like a fine volleyball net, so the bats hopefully don't see them,
fly into it, get tangled, and then we take them out.
And we take a guano sample from the bat, so we can figure out what they're eating.
The bats out here are using this corridor, as well as flying across the farm fields.
So part of my research is looking at how bats are contributing to pest control.
So how bats are benefiting farmers and
what agricultural insect pests they might be consuming.
We've been working near farms.
We have five or six sites that we've been frequenting.
And then we try to rotate through each of those sites.
Bats are emerging around dusk.
So, right now it's about 8:45 that we start to see the first bats that
are coming out of their roosts and flying around.
Once we have those nets open, we'll check them about every half hour and
extract any bats and take measurements on them.
Bat activity usually starts to slow down around midnight.
And depending on the weather and
the site, that activity will continue until about 2 AM.
Usually bats have one main foraging bout when they emerge at dusk.
And then they will take a break, a pit stop.
They'll roost somewhere during the night and
often come back out again in the early morning.
[SOUND] >> [INAUDIBLE]
>> I can hold it if you want.
>> I am holding it.
>> [INAUDIBLE]
We've gotten a lot better at putting this up.
[SOUND] >> [LAUGH]
Okay.
>> Yawning.
>> There's a bat.
>> There's a bat.
So first bat of the night.
And it flew in from my side of the net, so it was going downstream I guess.
And they're delicate but they're still pretty feisty you see
If I look at its calcar, which is the membrane between its leg and
its tail, based on the size, I know it's one of two species.
Right here coming of its leg,
there is a little bit of cartilage that goes out towards the tail.
So for this species we know that it's a Yuma Myotis because that cartilage is,
it's kind of smooth.
If it were a little thicker and
had a bit of a corner, then it would be called keeled.
So this bat doesn't have a keeled calcar, so we know it's a Yuma Myotis.
I'm going to put it in this clean paper bag and
hope that it poops in there and gives me a fecal sample.
But we'll take it back, we'll finish checking the nets I guess, and
then we'll take it back to our processing station and take some measurements on it.
Take a hair clipping, weigh it, measure its forearm.
You made lots of poops.
>> Yay.
>> [LAUGH] Good job.
We need those.
This is the first bat that we've captured tonight.
It's a little Yuma Myotis.
So I'm going to measure its forearm.
This can also be a way to distinguish between species.
This one we already know, but
the range of the forearm can help with that, so, 34.5.
And then we want to know the sex, this is a female.
Now I want to see if she's reproductive or not.
So the bats right now either have given birth or
are lactating, so I'll look for a nipple.
She does have a nipple that's not really exposed, but
it looks like maybe she's post-reproductive.
But I can check and see if she feels pregnant at all.
And I'll just feel her abdomen and feels like she's full but it's kind of squishy,
so it's probably just insects, not that she's pregnant.
And then I want to check and
just confirm, I think it's an adult because I think she's post-reproductive.
But I can look at the joints in the wing and see if the bones have ossified.
So it's easy to see if there's a light under it.
And so these joints look fairly nodular, not elongated,
and you can't see through them, there's no clear parts.
So the bone is ossified at the joint, so it's an adult.
You can see there's some spots where maybe the wing had some tears before, but
it heals up very quickly.
A way to mark the bats so that we can make sure that we're not taking samples from
the same bat multiple times is to cut a patch of fur between the scapula.
So this bat looks like it's got all the fur there, so
I don't think we've caught it before.
This bat has really thick fur.
From the hair we can tell more about the diet using carbon and nitrogen isotopes.
So now we just have to weigh this bat.
So this bat weighs 6.9 grams, which is a pretty big bat for this species.
So since we have all the samples that we need and
there's enough fecal samples in the bag, we are done with this bat.
If she doesn't want to fly away right away, I can put her back in a bag and
kind of stuff her in my shirt to keep warm.
And then I'll be able to feel her moving around and
I'll know that she's ready to go.
Usually, if we haven't had them for very long and they're being feisty like this,
then you just really need to let them know that they're free, [LAUGH].
because she's been trying to escape as long as I've had her.
So she's figuring out where she's, come here [LAUGH].
>> [INAUDIBLE] >> Yeah, it's very bright.
She might be a little disoriented.
There she goes.
So we have samples from six sites all over the central coast, farms, and
different landscapes.
And my research question is asking whether or
not bats are eating different things in these different landscapes.
Around here there's not a whole lot of natural habit,
other sites there's more forest.
And possibly with more habitat comes more different kinds of insects.
So we take these tubes, these fecal samples, and
I will be learning how to process them in the lab.
I'm going to work with a lab down at UCLA to extract the DNA.
And then I'll prepare the samples and then send them probably
to UCLA has a service where they can actually read the DNA,
come up with a barcode for all of the species that are in all of those samples.
So I'll have a list of barcodes of species that we can
match up with the public database.
And figure out what species that the bats actually consumed.
Then we'll look at what they're eating across the different landscapes and
sites, see if that's different.
>> Elissa's repeating this kind of sampling at both organic and
conventional farms, and at farms located both in a sea of other farms and
bordering forests and natural waterways.
Her findings will help us understand how both practices on single farms and larger
landscape planning affect the connections between wildlife and crop production.
In the bigger picture, California's agriculture is always evolving rapidly in
response to things like the changing availability of water in the state.
And one of the things about California agriculture that has been true for
a long time is that it's a great center for innovation in all kinds of ways.
Both at the small scale, sustainable end of the spectrum, and at the large scale,
commercial end.
So, although agricultural and other ecological values often conflict here in
California, the state also has resources and opportunities like nowhere else.
To learn to better align food production with other values like wildlife
conservation.
[MUSIC]
