Habitats exist at many spatial scales:
->Global
--->Continental
------>Region or State
--------->Landscape
------------>Farm
--------------->Field
------------------>Site
-------------------->Microsite
->Global
To
extra-terrestrial aliens looking down at us, the earth is a habitat inhabited by what we
call biology. The world is our habitat, not a bad one at that.
--->Continental
Each
continent on earth has many habitats unique to it. North America is our continent, and it
sometimes seems that our unique habitats are infested with weeds that came from every
continent on earth.
------>Region or State
The state of Iowa has many habitats within it. Below is a view of another region, the
Province of Ontario in Canada. Its habitats can be seen below and extending over a large
area, off the edge of the horizon. They grow quackgrass in their habitats much better than
we do in our habitats here in Iowa.
--------->Landscape
A landscape is an extensive area with varied scenery and habitats as viewed from a single
aspect. The farms and countryside around Ontario can be seen in these landscape scale
aerial photographs below. How many different habitats can you indentify in each?
------------>Farm
Below are two Ontario farms, and important spatial scale of habitats for crop production.
The one on the left has some white patches in it, possibly caused or related to drainage,
what do you think caused them? The patches are not at a farm scale, but at a site scale.
The farm on the right has rolling topography, and in the distance is a rapeseed field with
a nice infestation of wild mustard in flower. Rapeseed is the big competitor to soybean in
the world oil market. The Canadians call rapeseed Canola, Canadian Oil-a maybe.
--------------->Field
Still more of Ontario, below are some field habitats. Far left is small grain field with
some patchy, site scale problems, maybe associated again with drainage. What do you think
the problem is there? Left center is a nice hay field, a perennial habitat. See the big
bales drying in the northern sun? I have to admire the farmer, owner of this field for
their restraint in not cutting down that wonderful maple tree. Most owners would view the
tree as lost yield. In fact, it is an important habitat to local animals, a refuge. Right
center is a roadway and a sloping field. The field shows you two important qualities of a
habitat or site, slope and aspect. Do you know the difference? There is also a weed
problem on the headlands of this field habitat, weeds probably. Roads and roadsides are
habitats too, every see a weed punch through the pavement? I have. Far right is a tidy hay
field. The farmer on a tractor is in the center of this very symetrical field. I bet they
had fun making those perfect square rings with the mower. Let it dry and bale it up.
------------------>Site
A site is a local part of a field. Site-specific management is becoming of interest to
more farmers every day. Site-specific management of weeds will require us to know where
the weed patches are, and if they will move in the future. Yield monitors and field maps
generated with GIS/GPS equipment have increased farmer awareness and interest in managing
weeds at this spatial scale. What happened to the site in the corner of the field in the
picture below on the left? Center below is a corner of a field site that has many
problems, including atrazine carryover that has killed or stunted the soybeans, not to
mention volunteer corn and stony soil. The field on the right also has some serious site
habitat problems. It's too late to grow soybeans in this field with its atrazine residues
from the previous year; but a trap (or better yet a gun) could solve the need to relocate
the large mammal (badger? muskrat?) den (the hole) to a different habitat. Still too many
stones in this habitat to my liking.
-------------------->Microsite
To an individual weed, the spatial scale that counts is the microsite. Microsites are as
varied as any other spatial level of habitat, but more varied microsites exist in a small
area than other scales. Below are some microsites of interest. Left is a velvetleaf that
found the soil under this clod was an ideal place to start its life. Center is a
quackgrass shoot that has emerged from the sandy Ontario soil from a mother rhizome below.
On the right are some horsetail (Equisetum arvense) spore heads that have emerged
in their cold early spring soil microsite, ready to spread their ancient propagules.
The small velvetleaf plant (below) has exploited an available microsite, adjacent to the cement highway on South Dakota Road, south of Ames near the Curtiss Research Farm and the ISU Press. Not the most favorable microsite, but enough to set seed and keep the whole thing going another year.
Another unusual microsite was exploited by the grass plants (below), the roof of the Emperors Palace. The Forbidden City in Peking, China was the microsite habitat of the former Chinese ruler. That microsite is now denied to his heirs, but that hasn't stopped these weeds from thriving there. This microhabitat is one very small part of the continental scale habitat now infested by the Communists.
