Wind - Agroecology: The Ecology of Sustainable Food Systems - page 90

FIGURE 7.3 Lodged corn knocked over by gusty, rain-laden winds near Cárdenas, Tabasco, Mexico.

In agroecosystems, wind damage occurs most fre-
quently in annual crops nearing maturity, when the plants
are top heavy with grain or fruit. This type of damage,
where the crop stand is flattened to the ground, is called
lodging . In fruit crops, such as apples or plums, wind can
both diminish pollination at the flowering stage and knock
fruits off the tree before picking can occur (Figure 7.3).

by a drop in CO 2 as a result of photosynthetic uptake. Plant
growth can be slowed if the concentration of CO 2 goes too
low, because photosynthesis is limited. Air movement,
however, acts to mix the air around plants, disturbing the
oxygen-rich boundary layer around leaves and accelerating
the diffusion of CO 2 toward the stomata. In this way, wind
can actually be beneficial to plants.

C HANGES IN THE C OMPOSITION OF A IR
S URROUNDING P LANTS

OTHER EFFECTS OF WIND

Wind impacts individual plants directly, as detailed above.
But wind has agroecosystem-level effects as well because
of its ability to transport materials.

Apart from desiccation and the physical alteration of plant
form, wind can also change the quality of air surrounding
the plants. The air immediately around an organism is
important since it is through the atmospheric medium that
gas exchange and heat exchange can take place. The atmo-
sphere directly affects plants by providing the CO 2 used
in photosynthesis and the oxygen used for respiration.
Normal air is composed of 78% nitrogen, 21% oxygen,
and 0.03% CO 2 . (The remaining less-than-1% is a mixture
of water vapor, dust, smoke, pollutants, and other gases.)
In the immediate atmosphere surrounding plants, however,
levels of oxygen and CO 2 vary considerably since plants
produce oxygen and take in CO 2 . During the day, oxygen
levels close to plants can rise dramatically, accompanied

W IND E ROSION

In any region with low and variable rainfall (or the poten-
tial for drought), occasional or frequent high-velocity
winds, and high evaporation losses from the soil surface,
wind erosion of soil can be a problem. Under such con-
ditions, a loose, dry, smooth, and finely granulated soil
surface lacking or partially lacking vegetative cover is
easily eroded by wind.
Loss of soil by wind erosion involves two processes:
detachment of particles and transport of particles. Wind