Filmed on location, the landscapes were barren. There were
rocks and dirt, bushes and the rare tree, buttes and canyons, coyotes and lizards
– typical American southwest. But the movies were filmed in Italy and Spain! These were
the spaghetti westerns.
The stories took place in the American southwest and
northwestern Mexico, but they were actually half a world away. How can
the countryside around the Mediterranean Sea look like the desert southwest in
America? The climate, flora, and fauna of very different places can look very
similar because they are the same biome,
sooo…..
Question of the Day:
What makes biomes the same or different and who decides which biome it is?
First of all, some of the desert southwest isn’t desert. It
is a biome called chaparral (chapa = scrub in Spanish). Chaparral is
the smallest of all the world’s biomes. A biome is a major ecosystem with a
single climate, but perhaps more than one habitat or community. It’s a huge ecosystem,
which in turn is made up of several smaller habitats. The major idea is that it
is housed within a single climatic region.
In North America, the chaparral is found in California and
maybe Arizona, at about 40˚ North latitude. In Spain and Italy, chaparral is
found at just about the same latitude. In fact, all around the edge of the
Mediterranean is very chaparral-like, including North Africa and much of
Israel.
The distance from the equator with the tilt of the Earth
means that 40˚ South latitude might have much the same climate, and we see that
the Chilean chaparral, as well as similar biomes in South Africa and Australia
are close to 40˚S.
Also called a Mediterranean scrub biome, chaparral is hot,
dry, and liable to catch fire. Many of it plants depend on fire to disperse or
activate their seeds (pyrophytes = fire-loving). Others have below ground
growth that sprouts after a fire. We will have to do some posts on pyrophytes
soon. However, lots of fire doesn’t mean chaparral is lifeless; it has 20% of the
world’s plant species and many are endemic
(only found in that climate).
A 2013 study in PNAS shows that fire is essential for regrowth
of
habitats. The study found that a chemical is produced by
plants
when they catch fire, called karrikins. This signaling
molecule
settles in the soil after the fire and binds to the seeds
that
are there. The binding protein was discovered to be KA12,
which
then alters its shape and promotes germination of the
seeds right after the fire is over. Amazing. |
But it’s all a lie! The tumbleweed proper is known as
Russian thistle (Salsola tragus,
probably several species). It doesn’t roll along because of the harsh and
destructive nature of the chaparral; this is how it disperses it seeds. After
flowering, the plant dries up and disengages from its roots on purpose. As it
rolls, it drops seeds, like a trail of breadcrumbs never to be used to find a
way home.
Heck, Russian thistle isn’t even from the chaparral biome. It's native to the steppe grasslands of Russia, a different biome altogether.
Russian steppe is cold, and is wet, but it is windy, so it’s mechanism of seed
dispersal works in chaparral. Therefore, it can survive in California, and
Spain, and Italy, and Morocco, and Israel. Here we have a plant that is
identified closely with one climate that comes from another.
Indecision and overlap abound when it comes to naming and
defining biomes. For instance, what makes a chaparral a chaparral and not a
desert? What makes it a chaparral and not a grassland?
For many ecologists, the difference is precipitation.
Deserts get less rain, snow, fog, or humidity than chaparrals, which in turn
get less of these things than grasslands. But others divide grasslands into
tall and moist versus short and wet. So does the dry grassland still get more
rain than the chaparral?
In the chaparral of Israel, different biomes can come as
close together as different slopes of a canyon. A 2012 study has proposed that
these canyon faces with completely different flora and climate should be used
as “evolution canyons” where global
warming can be monitored and changes in many different ecosystems can be tracked
in a small place. And this is all supposed to be within the world's smallest biome?
At 50-60˚ S latitude, there is very little land. Almost all
the way around the Earth at those latitudes there is nothing but ocean. So
latitude isn’t everything when it comes to defining biomes. Tierra del Fuego
and the southern part of Patagonia are located south of 50˚ S, but they are
defined as neither taiga nor tundra.
The major terrestrial biomes of the world include desert,
tundra, taiga, deciduous forest, grassland, and tropical rainforest. But these lists
are often incomplete or vague. Chaparral is often left off the list; it has
climate very similar to desert, plants able to deal with desert-like heat, and
plants that come from grassland biomes. What is even weirder, it is the only
biome where the wet season is the same as the winter season. Overall, it’s an
in between biome and muddies the waters, so it often falls through the cracks.
Biomes may be classified by climate (Holdridge scheme),
which generally equates to latitude, but we have already seen exceptions to
that. Another scheme, Whittaker’s biome-typing, works to classify regions based
on temperature and precipitation. Other systems are based on some combination
of these factors, but if they are using the same factors, why don’t they agree
better?
Another problem is in the naming itself. Who decides on the
name, and what does it mean in different areas of the world? The World Wide
Fund For Nature (WWF) has a naming system that tries to be specific and generic
at the same time. What is often called rainforest is designated by WWF as
either “tropical and subtropical moist
broadleaf forest” or “tropical and subtropical dry broadleaf forest”
depending on the amount of precipitation. Don’t really roll off the tongue, do they?
Locality plays a
role in the naming problem. Mediterranean scrub biome - is it by the sea,
not always. Is it only scrub brush, not always. So that name isn’t so good. But
even around the Med it’s called different things – maquis in Italy, garrigue
in France, phyrygana in Greece and batha in Spain. In America, it’s the
high chaparral – like the TV show.
But in Chile, it’s called matorral (mata = shrub in Spanish). In South
Africa, it’s the renosterveld or fynbos, but Australians know it as mallee scrub or Kwongan heath.
Carolus Linnaeus
(1707-1778) developed a binomial system for naming in botany and zoology, specifically
to alleviate the locality and organizational naming problems. But a system such
of this was never developed for ecology. Why not?
All of this imprecise naming and description, and we’ve only
touched on the terrestrial biomes. There's a whole set of problems attached to
the aquatic biomes as well. Some definitions list only one biome in water, with
different freshwater regions (ponds, lakes and such), and marine regions
(oceans, reefs, estuaries).
So - are the bogs considered part of the taiga, or just
habitats within a biome? Or are they their own biome within a biome? Not easy
to decide. Biomes are essential for organizing the life on Earth, but the
learning would be easier if we could find a Linnaeus for ecology.
Next week, can you have mold without mildew? Just what are they anyway?
Nevo, E. (2012). "Evolution Canyon," a potential microscale monitor of global warming across life Proceedings of the National Academy of Sciences, 109 (8), 2960-2965 DOI: 10.1073/pnas.1120633109
Guo, Y., Zheng, Z., La Clair, J., Chory, J., & Noel, J. (2013). Smoke-derived karrikin perception by the / -hydrolase KAI2 from Arabidopsis Proceedings of the National Academy of Sciences, 110 (20), 8284-8289 DOI: 10.1073/pnas.1306265110
Next week, can you have mold without mildew? Just what are they anyway?
Nevo, E. (2012). "Evolution Canyon," a potential microscale monitor of global warming across life Proceedings of the National Academy of Sciences, 109 (8), 2960-2965 DOI: 10.1073/pnas.1120633109
Guo, Y., Zheng, Z., La Clair, J., Chory, J., & Noel, J. (2013). Smoke-derived karrikin perception by the / -hydrolase KAI2 from Arabidopsis Proceedings of the National Academy of Sciences, 110 (20), 8284-8289 DOI: 10.1073/pnas.1306265110
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