The Experimental Control

Every experiment in science has a control which can be thought of as a test where nothing is done, no treatment, no manipulation, really just a base line for the experiment allowed to run concurrently with experimental treatments.  The grassland restoration project at the Painted Pony Resort has an experimental control.  It is an area marked off by railroad ties at the north end of the property enclosing an area of about 12' x 12'.  This area started as bare earth when the main complex was built and the former estate manager placed the railroad ties to create a planting area but did nothing further.  I have left this area alone to see what would happen if there was no intervention on the landscape (only cutting back tumbleweed occasionally so I don't get any 5' high plants).  While it may appear I have not been diligent in keeping the area free of weeds and other woody shrubs this plot shows what happens if a barren area is left to naturally recover.  The plot is dominated by tumbleweed but also has woody shrubs including mesquite, Indian tea, amaranth, and rubber rabbitbrush and 1 unidentified thick stemmed weed.  Two species of annual grass have grown and one species of a perennial bunch grass has appeared but little else.  This suggests that a passive management strategy of only removing grazers and allowing the land to rest for several seasons is no longer adequate for the landscape recovery when starting from bare ground.  Rather it takes an active management strategy to restore the grassland in this heavily modified desert landscape.  For the estate that means interventions to manage water, soil, vegetation, and animals. 

The question arises as to why simple rest no longer appears to be adequate to recover the grasslands on the estate.  Several factors may be involved with the appearance of only a single perennial grass within the test plot shown below.  It may require longer periods of rest (a couple of years is not sufficient) to recover grasses within the test plot and is a reflection of my inexperience with restoration in the desert.  Or it may be a result of succession in the grassland, that is with enough time the perennial grasses will out compete the other plants.  Or it may be related to changes in climate.  About 20 years ago The Portal Project (a long term desert ecology project in the area) published a paper on the changes within their test plots, noting a shift from grasses to woody shrubs within their enclosures they suggested changes in rainfall were resulting in a shift away from grasses and to woody shrubs.  The Malpai Borderlands group also noted this shift away from grasses and towards woody shrubs with the exclusion of grazers and the loss of fire as a tool for managing grasslands, see their historical photo archives and click on a tag to view historical and recent repeat images.  Changes in climate, especially short term ones, have a particularly large effect on minimally productive desert landscapes and periods of drought in combination with human activity are known to have altered the landscape particularly the drought of 1891-93 in the area.  But are long term changes also having an effect?  Changes in rainfall patterns, especially increasing winter rains favor woody shrubs over perennial grasses making it more difficult to restore grasslands and is one reason the river bottom grasses are currently isolated so grass seed production will continue unabated.  The yearly mean temperature in New Mexico has increased 2 degrees since 1970 and marginal landscapes like the high desert may be the first to respond this change.  Whatever the source it is clear that active management as opposed to passive management techniques are required to create and sustain a productive landscape.

Control plot of vegetation with out any intervention.  Tumbleweed predominates followed by woody shrubs.