The Morning Blend
Welcome
Complete Media Kit
Commentary by Alan Blixt
Special to the Herald/Review
The San Pedro Riparian National Conservation Area is one of the most biologically diverse places in North America. More than 350 species of birds have been seen on the SPRNCA, along with more than 80 species of mammals and nearly 60 species of reptiles and amphibians. More than 600 species of plants have been identified in the NCA.
Why is there so much diversity here? Overlapping eco-regions, open space, clean air, and large, intact blocks of land are the major reasons. The Rocky Mountains begin just north of here and extend all the way to Alaska. This is a temperate, high elevation mountain range. To the south we find the Sierra Madres, a warm, sub-tropical mountain range extending south into southern Mexico. Our local mountain ranges are the northern most extension of the Sierra Madre and the southern most extension of the Rockies. To the east we find the temperate mid-elevation Chihuahuan Desert and to the west, the sub-tropical low elevation Sonoran Desert. Together, these four large and very different eco-regions blend here in the San Pedro River Valley resulting in a wide variety of habitats.
Within the NCA, the river is characterized by a water-side cottonwood/willow gallery forest on the banks of the river. On the terraces above the river is a Mesquite woodland (or Bosque) adjacent to a floodplain grassland. In the northern portion of the SPRNCA we find desert scrubland above the Sacaton grassland floodplain. Further south in the SPRNCA we have semi-arid grassland instead of the desert scrub.
 Riparian habitat showing beaver dam with rocky terrain and elevation change in the background. (Courtesy of Dutch Nagle) |
The hills located in the vicinity of Charleston include another habitat, rocky outcrops, unique within the SPRNCA. This tremendous variety of habitats offers many unique environments where different species of plants and animals with different preferences not only survive but flourish.
A final major influence is the highly varied climate in Southeastern Arizona with five distinct seasons. We have the classic four seasons familiar in much of the rest of North America, plus our blazing hot dry “pre-summer” season that is the prelude to the summer rainy season. Our two distinct rainy seasons, summer and winter, also have a great influence on habitat and plant communities.
Winter moisture from mid-December through early March is essential for successful spring wildflowers. April, May and June are our driest months of the year and are windy resulting in tremendous wind pollination and seed dispersal. From early July through early September (the monsoon), we receive 50 and 60 percent of our yearly rainfall. These rains are critical for our summer wildflowers and warm-weather grasses. I have never seen an explosion of life anywhere to compare with the onset of our rainy season.
Incidentally, it is the failure of our winter rains that has resulted in our “drought” conditions, which may actually be a return to more historically normal rain patterns rather than a short-term drought that we can simply “wait out.”
Different habitats support different plants and the different plants support different animals. The floodplain/grasslands support bunch grasses, soaptree yucca, gourds, pepper-weed, golden crownbeard, wild sunflower and many other plants. These plants support a wealth of grassland birds as well as a wide variety of insects, grazers and browsers, and then indirectly the predators that consume those animals.
The riparian habitat has enough water for larger plants and trees such as cottonwood, willow, ash, walnut, and seep willow to grow. This wooded area supports yet another community of animals and insects. Here we find many of our larger animals such as bear and mountain lion. Beaver are only found in this habitat. It is also here that we find the greatest number of birds because this environment provides suitable nesting areas as well as abundant food to feed their chicks.
Although the SPRNCA does not offer much elevation change within its boundaries, it is only a few miles to the mountains and canyons of the Huachuca Mountains, where the elevation increases to more than 9,000 feet. The flora and fauna at these higher elevations are certainly different from those found along the river. However, because of the proximity of these mountains and the migratory nature of things, we often see plants and animals within the SPRNCA that do not normally reside here.
When you realize the variety of habitats in this area it is easy to understand the diversity that we enjoy.
Join us on our walks and hikes, or just take a walk on your own and enjoy your public land. (Our next hike is scheduled for Nov. 17 starting at St. David Research Natural Area.)
ALAN BLIXT is a member of the Board of Directors and a docent for the Friends of the San Pedro River. He can be reached at fspr@sanpedroriver.org or FSPR, 1763 Paseo San Luis, Sierra Vista AZ 85635, or by phone at 459-2555. Water Wonderland is a column by the Friends of the San Pedro River that runs the second Friday of each month.
to oh no wrote on Nov 17, 2007 3:36 PM: