Geoscience Reference
In-Depth Information
(a)
(b)
Figure 10.18 The tundra biome.
(a) The vegetation here consists of low-growing plants, primarily very short grasses, mosses, and li-
chens, which have adapted to the short, cold growing season. (b) Lichens are a mix of algae, bacteria, and fungi that favor rocky surfaces
such as those pictured here. The central rock, which is about 15 cm (6 in.) wide at its thickest point, is surrounded by low-growing moss.
VISUAL CONCEPT CHECK
10.2
This image shows a typical scene in one of the
major biomes on Earth. Which biome is pictured
here, and how do migrating atmospheric pressure
systems influence the seasonal climate and thus
the vegetation in this place?
Local and Regional Factors
That Influence the Geographic
Distribution of Vegetation
Slope and Aspect
The
slope
of an area is its degree of steepness, with high slopes
being places that are steep and low slopes being relatively flat.
As the slope of a landscape increases, the amount of water that
runs off the surface, rather than soaking into the ground, usually
increases. Steep slopes thus typically have less available soil
moisture, and the associated vegetation can be different than
on shallow slopes. Soils also tend to be thinner on steep slopes
than on shallow slopes, which influence the amount of nutrients
available for plants.
Another factor related to the slopes within a particular land-
scape is the concept of
aspect
. Slope aspect refers to the orienta-
tion of the slope—that is, whether the slope faces north, south,
east, or west. Aspect is an important variable in plant geography
In addition to the geographic distribution of biomes, other
factors can influence the types of plants that live in a region
or area. It is useful to think of these variables as being local
or regional in scale because they may cause a particular pat-
tern within the overall biome. The following discussion of lo-
cal factors is not meant to be a complete review of all the
variables that can influence the distribution of vegetation, but
rather seeks to provide a good sense of the most important of
these factors.
The degree of steepness of a portion of the landscape.
Slope
