Sinkhole formation, dynamics, and colonization in the Churince System, a disturbed desert wetland in Cuatrociénegas, Coahuila, Mexico

Background/Question/Methods

The Cuatrociénegas Valley, in the Chihuahuan Desert, has several microhabitats that include a complex system of wetlands. All the aquifers in the region are overexploited, and are mainly used to irrigate alfalfa. The Churince System, that includes a terminal lake, is quickly disappearing.

As water stopped arriving from the Churince spring to the terminal Churince Lake, numerous sinkholes of different sizes and depths were formed, creating  humid and shaded microhabitats embedded in a dry and salty matrix. These microhabitats are colonized by riparian species that are only found in the borders of water bodies under normal conditions.

We studied the formation, dynamics and colonization of sinkholes in the Churince System, as well as their physical characteristics (size, depth and level of water) in order to determine the above-ground symptoms of disturbance of the hydrological system. We analyzed the dynamics of sinkholes censing them every two months, and measuring their physical parameters, species richness and plant cover. Sinkholes were categorized by their surface, their richness and the general plant cover, and a matrix probability model (Gotelli, 2008; Caswell, 2001) was built to project their behavior in time, and a general colonization pattern was identified.

Results/Conclusions

Sinkholes became more abundant during 2008 and 2009; their rate of formation has decreased since 2010, as the lake and the creek have lost water and dried. The matrix model predicts a constant formation and growth of sinkholes, with increasing size and plant cover. Water level changes annually and seasonally. In January 2008, 2009, 2010, 2011 and 2012, 50.8%, 44.6%,  24.3% , 50%, and 0 .66% of sinkholes, respectively, had water. Most of the colonizers are perennials. Samolus ebracteatus var coahuilensis is the most frequent species, as it can be found in more than 90% of the sinkholes. It is usually the first colonizer, followed by Flaveria chlorifolia and Bolboschoenus maritimus. As sinkholes are colonized, the relative cover of S. ebracteatus diminishes, and that of B. maritimus and the graminae increases. The presence of sinkholes and of riparian species away from the borders of water bodies are an early alarm system of disturbance of the hydrological systems in Cuatrociénegas.