Jornada Basin LTER

Ephemeral Streambeds More Productive in Desert Ecosystem

Jornada LTER researchers, led by John Wainwright and Tony Parsons, have discovered that vegetation growing in areas of sediment deposited by ephemeral streams (“beads”) shows marked differences from surrounding areas. These depositional areas have significantly higher vegetation cover and contain significantly higher proportions of grass species. Furthermore, creosotebush plants show evidence of less moisture stress, higher rates of soil-nitrogen transformations, and greater loss of nitrogen to the atmosphere compared with the surrounding areas. All these factors are consistent with higher rates of infiltration and, hence, high soil moisture in these depositional areas. Ephemeral streams typically show areas of deposition and areas of erosion along their length; the areas of deposition are transient over decadal timescales. Because these areas of deposition are favorable to grass growth, landscape modifications to promote deposition may offer a method for remediation of degraded lands in dryland environments.

Wireless Fencing Improves Grazing Management in Arid Ecosystems

Jornada LTER researchers, in cooperation with FuTure Segue and the USDA Agricultural Research Service, led by Dean M. Anderson are developing near real-time wireless technology to alter the behavior of cattle on grasslands and shrublands that could make traditional internal fencing obsolete. Directional Virtual Fencing (DVFTM) is a patented methodology that uses computer technology, animal behavior, and electro-mechanically ramped cues to locate animals and move them across a landscape in a manner characteristic of rotational stocking, but without the challenges of conventional fencing. The animal-mounted unit combines a solar-powered global positioning system (GPS) with spatial data in a geographic information system (GIS) to determine animal location. If an animal penetrates a Virtual Boundary (VBTM), then cues are automatically activated and applied to either the animal’s right or left side to modify the its behavior to return to the Virtual Paddock (VPTM) with the least amount of stress. Progress is underway to move animals from one part of the landscape to another using DVFTM that will allow better utilization of forage in a landscape. In the future, combining DVFTM with remotely sensed images containing ecological information, such as forage production and/or quality, biodiversity, and water sources, has the potential to revolutionize ecological research as well as land stewardship by turning foraging animals into ecological management tools.

How Will Global Climate Change Affect Shrub-Grass Relationships in Arid Lands?

Global climate models predict regional changes in average seasonal precipitation, but few experimental studies have addressed how changes in the delivery of precipitation within a season affect ecosystem responses in arid lands. Initial findings in our rain modification study during the very dry New Mexico summer of 2003, indicate that changes in the distribution of an additional 60 mm of precipitation had a significant effect on ecosystem function. Mesquite shrubs, which are encroaching on these formerly grass-dominated systems, were able to use water from both small frequent rainfall events and large infrequent rainfall events, with the most positive responses occurring with the latter. By contrast, biological soil crust communities, which colonize surface soil and are essential in these arid regions for minimizing soil erosion, benefited from smaller more frequent events. This study at the Jornada LTER, in collaboration with the USDA-ARS led by Keirith Snyder, will continue over a number of years to determine how experimentally applied frequent small rainfall events differ in their impacts from infrequent large rainfall events. Our results have important implications for understanding grass-shrub dynamics in this region, and for predicting future changes with directional changes in climate.

Carbon Storage in Arid Ecosystems: The Forest is Below Ground

Though forest and peat bogs are well known reservoirs of terrestrial carbon, desert soils can store as much carbon or more. Our research, led by Curtis Monger, show that most carbon in deserts exists as inorganic carbon (pedogenic CaCO3) and of that, large amounts are in the form of calcified soil microbes. At the Jornada Basin LTER, organic carbon is much greater belowground than above-ground. This is especially true for mesquite shrub mounds, which have deep tap roots and far-reaching laterals. Of the broad areas where mesquite is the dominant species, it can be said: at the Jornada Basin LTER, the forest is below ground.