Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Accueil du site → Master → Etats Unis → 2014 → Reduction of ET depletion through management of riparian saltcedar and native inland saltgrass in a semi-arid region

New Mexico State University (2014)

Reduction of ET depletion through management of riparian saltcedar and native inland saltgrass in a semi-arid region

Solis Juan Carlos

Titre : Reduction of ET depletion through management of riparian saltcedar and native inland saltgrass in a semi-arid region

Auteur : Solis Juan Carlos

Université de soutenance : New Mexico State University

Grade : Master of Science (M.S.) 2014

Résumé
Surface water supplies in the southern part of semi-arid region of New Mexico have been heavily affected in the recent two decades due to sporadic precipitation events, limited flows in the Rio Grande and increase of population. The Rio Grande has been the primary source of water supply for the region including the riparian areas along its banks. These riparian areas, which depend on the Rio Grande and summer precipitation, are also going through environmental changes. The native plants such as cottonwood, inland saltgrass, willows and others that are accustomed to occasional flooding, shallow groundwater table and summer monsoonal precipitation are disappearing. They are being replaced by species such as the exotic saltcedar (Tamarix spp.) that are more adaptable to deeper groundwater table, less precipitation and, poor soil and water quality. These changes are causing a less diverse and unhealthy plant communities along the riparian areas of the Rio Grande. To better understand consumptive water use of riparian plants (exotic and native), this study investigated evapotranspiration (ET) depletion of saltcedar in an area by Caballo, New Mexico managed by the U.S. Bureau of Reclamation during 5 years from 2009 through 2013. In addition, the net ET depletion was evaluated when saltcedar managed area was replaced by native vegetation such as saltgrass. Evapotranspiration of a dense saltcedar at Bosque del Apache National Wildlife refuge along the Rio Grande by San Antonio, New Mexico was used as a baseline for this study. Measurement if ET was conducted using energy budget method using eddy covariance technique. Evapotranspiration of dense monotypic saltcedar, monotypic saltgrass, and saltcedar managed by herbicide applied via carpeted roller applicator and mowing was determined as a residual in the energy budget. During the 5 years of measurement, the ET of dense monotypic saltcedar varied from 1279 mm/yr to 1448 mm/yr with an average of 1363 mm/yr. The ET during growing season (241 days) averaged to 1183 mm. The ET of saltgrass varied from 780 mm/yr to 866 mm/yr with an average of 832 mm/yr and during growing season (241 days) averaged to 722 mm. Annual ET of managed saltcedar varied according to different treatments — herbicide, mowing, or none. In comparison to untreated dense saltcedar, the treatment of saltcedar with herbicide applied via carpeted roller applicator resulted in a second year ET reduction of 27% or 204 mm. Management of saltcedar using herbicide applied via carpeted roller applicator in 2008, followed by mowing once in 2011 resulted in 33% or 268 mm reduction in ET in 2012. The difference in ET between dense saltcedar and saltgrass during the growing season ranged from 34% and 44% and on annual basis (365 days), a difference in ET loss of 36% or 479 mm was estimated. The difference in ET between managed saltcedar and saltgrass initially ranged between 25% to 28% (261 mm - 343 mm ) but as time progressed and management continued the difference decreased to 9 - 11% (64 mm - 69 mm) indicating that saltcedar dominance was decreasing and low water consuming replacement vegetation was increasing. Management of saltcedar using herbicide via carpet roller applicator and by mowing reduced ET depletion (conserved water) and improved plant diversity allowing low water consuming plants, in this case saltgrass and other shrubs, to thrive. It can be concluded from this investigation that managing saltcedar by mowing or by using herbicide treatments would increase the spread of native grasses such as saltgrass, suppress saltcedar dominance as well as reduce ET losses. However, the timing of mowing should be adjusted as recommended in this study in order to improve its effectiveness and probably reduce cost of management on a long-term basis. Herbicide treatments and methods of application for suppression should be further evaluated in lieu frequent mowing.

Mots clés  : Stream conservation — New Mexico. Saltcedar — Control — New Mexico. Riparian plants — New Mexico — Management.

Présentation (NMSU Library)

Page publiée le 7 novembre 2014, mise à jour le 24 décembre 2019