DistributionPonderosa pine is the most widely distributed
pine in North America, extending from British Columbia, Canada, in the
north, to Durango, Mexico, in the south. In the United States, it is found
from Nebraska west to the Pacific Coast.
TemperatureRegardless of the location where ponderosa pine
grows, average annual temperatures are between 42° and 50° F.,
and average July and August temperatures range between 62° and 70°
F. Ponderosa pine is found at elevations from sea level to about 9,000
feet. Throughout its range, as you move from north to south, the species
tends to grow at progressively higher elevations, and it is more restricted
to higher elevations in drier climates.
Tree SpeciesMost of the ponderosa pine forests are at elevations
between 5,500 and 8,500 ft on the Mogollon Plateau in Arizona. Although
ponderosa pine trees dominate these forests, they often contain Douglas-fir,
quaking aspen, and southwestern white pine at high elevations, and alligator
juniper (Juniper depeanna) and Colorado pinyon (Pinus edulis)
and its singleleaf form (P. edulis var. fallax) at low elevations.
Gambel oak (Quercus gambelii) is scattered throughout. Grasses
and grasslike plants, forbs, and half-shrubs grow beneath ponderosa pine
overstories.
PrecipitationPonderosa pine is generally found in regions
with arid conditions and summer rainfall. For typical areas where ponderosa
pine grows in the United States, average annual precipitation varies from
10 to 21 inches and the average precipitation during the growing season
(May through August) is from 2 to 6 inches. Also see: water
yield and potential increase.
Where ponderosa pine grows in Arizona, 6 inches of the total growing
seasonal precipitation of seven inches falls in July and August following
the MayJune dry period. Summer showers provide little moisture that
is useful to young pine seedlings. Total growing season precipitation
may mean little to the growth of the trees because of the distribution
pattern (small rainfall amounts separated by a period of several days
of no rainfall). A young tree seedling must quickly develop its root system
to be able to reach the water stored in the soil. Thus, ponderosa pine
trees mostly depend upon the water stored in the soil for their growth
and survival.
High transpiration rates and soil moisture deficiencies can curtail the
growth of plants in ponderosa pine even in forests which receive 20 to
30 inches of annual precipitation. High elevation forests tend to have
greater frequencies and amounts of precipitation than low elevation forests;
although this can be altered by storm patterns and topography. Usually
only a small amount of summer rain is converted into streamflow.
Fifty percent or more of the annual precipitation occurs during the winter
season and is the major source of runoff95 percent of the annual
streamflow. Because winter precipitation normally occurs as low
intensity rain or snow, and runoff is the product of either low intensity
rainfall or snowmelt, erosion potential is energy limited, and the dominant
parent materials generally limit the supply of sediment (e.g., heavy clay
soil characteristic of volcanic-derived soil) or the transport of the
dominant sediment size particles (e.g., coarse textured soils derived
from sedimentary and granitic parent materials) unless runoff is substantially
concentrated.
Resources and activitiesPonderosa pine forests are a valuable
source of water, timber, forage, and recreation. Carrying capacities for
livestock and wildlife, which graze these rangelands from late spring
to early autumn, are relatively high. A diversity of wildlife species
use these forests for cover and food, both seasonally and yearlong.
SoilsPonderosa pine grows on a variety of soils ranging
from volcanic to sedimentary origin. The physical properties of the soil,
and thus its moisture-retaining capacity, play an important role in the
tree's development, possibly more than the chemistry of the soil.
Studies have shown strong relationships between the vertical growth of
ponderosa pine and soil depth. In the Black Hills of South Dakota, soil
depth had more influence on tree height than soil parent material. In
Montana, pine growth response has been related to soil type, effective
soil depth, landform, and moisture availability. Increased water at a
site increased plant growth regardless of the soil type and landform.
The high water tables associated with springs tend to increase site productivity
regardless of the soil type and landform.
Volcanic basalt and cinders are the most common soil parent materials
in Arizona (57%), although sedimentary soils (43%) are also found throughout
these forests. Topography is characterized by extensive flat, rolling
mesas, intermixed with steeper, mountainous terrain, and a diversity of
slope and aspect combinations.
Images Available
There are over 1000 images available in the image
database illustrating various aspects and conditions found in chaparral
ecosystems in southwestern United States. These can be accessed
after getting into the database by using the key words Ponderosa Pine.
Additional key words are available for searching the images in a drop
down list within the database.