Judy Meyer (Coweeta) and John Hobbie (Arctic Tundra) were forward-seat-sitters in our last-in-the-caravan van on the Jornada science meeting field-trip along semi-arid dirt-roads of southern New Mexico. When I asked them to roll up their windows John said, "I guess we will find something about this dust in your next little newsletter (now a blog)." They were uncanny in their future telling. This issue of CED is about dust and its motor: the wind. We should be careful to note that Judy Meyer just wasn't herself. At our lunch stop she lamented the lack of trees and a stream in this otherwise nice LTER. The cement swimming pool surrounded with lovely mesquite didn't cut it with Judy.
The field trip began with a dusty ride to the "high-country" of the Jornada. In the future, I will learn to pick my van driver with great care. You need to select a driver with a high top-of-the-pecking-order status. You might, otherwise, get a van driver with lots of peck marks. Then you too could end up riding in the rooster-tail of dust of a low-pecker driven van. I was not the only novice oblivious to the need to know southwest van-driver sociology. Meyer and Hobbie were in the van but I was more the novice rider as I got the backbench of the four-seat dust-trap. They (Meyer and Hobbie) held control of the sluice gates that let the Valley Fever microbes in or out of the windows. I have learned that LTER locals like to talk about the diseases a visitor might get. At the VCR, we talk about Lyme disease. Niwot is fond of Glardia. The desert-pavement busters at the Jornada lay Valley Fever on you and then tell you that the problem is only serious when inhaling soil aerosols.
On these creosote-bush hillsides a local [read Wesley Jarrell] told the gawking CC-field-trippers that some 2.5 inches of the desert surface had been removed or deflated by wind and perhaps by some erosion during overland flow. All this occurred in the last 50 years. During the dust bowl days in Oklahoma, circa 1930s, the former sodbusters went to places like Oxnard, Pismo Beach and Altadena and the dust went to places like Pawtucket, Nantucket and Hicksville. Well, we need to talk about inter-ecosystem effects mediated by the winds.
First, we need to consider what the dust is. Here is my list of contents: weathered fragments of local parent rock and organic detritus with nutrient contents, spores, pollen, bacteria and seeds and dust from distant ecosystems deposited in days of yore. A more formal statement of what dust is comes from Geiger's book Climate Near the Ground. Geiger says dust is dry, rough, microscopic yet visible components of air plankton. Dust ranges in size from 1 to 50 microns and has terminal velocities between 0.1and 200 mm/sec. The stuff falls out of the air but gets out quicker by being washed out by rainwater. The atmospheric chemistry wags would use the words dry and wet deposition. Wind blown dust is an adjective linkage between ecosystems.
Dry deposition of dust is very much dependent on the roughness of the landscape. On 10 April 1935, over the German village Werm, 9000 dust particles per liter were measured. Downwind of Werm, over the farmland around the village, dust averaged 4000 particles per liter and on down-wind in the forests the dust content dropped down to 1500 particles per liter. Trees catch dust. Take a run down a country dirt road. Dust from the road (plus water splashed mud) cause the hedgerows on the side of the road to grow upward while the road is cut down. Hedgerows are dust and detritus traps. Privet hedges in cities also collect dust and grow upward. Urban dust is especially lovely stuff. Eating city dirt is like eating 1940s paint chips. Your minimum dose of lead is easy to attain.