Ecosystem effects of groundwater depth in Owens Valley, California

Abstract

Owens Valley, California, USA, is an important source of water for the city of Los Angeles; however, recent studies have documented losses of grass cover coinciding with decreased watertable depths in many locations. These changes in community composition are assumed to be associated with shallower rooting depths and greater vulnerability to declining watertable depths in grasses compared to neighbouring shrubs. However, the hydraulic properties and water stress resistance of most species in Owens Valley have not been measured. In addition, the relationships between groundwater depth and other aspects of ecosystem function such as nutrient cycling are not well understood. In this study, we measured grass and shrub cover, vulnerability to cavitation, and plant and soil isotopic and chemical composition at 9 sites along a depth to watertable gradient of 0Ð3-5Ð7 m in Owens Valley. Contrary to expectations, the grass species was more resistant to water stress-induced cavitation than either shrub species. However, grass cover declined in sites with deeper watertables while shrub cover remained constant. Water isotopes indicated shallower rooting depths in grasses than in shrubs, although the phreatophytic shrub Ericameria nauseosa had enriched leaf water isotopes at deep groundwater sites, indicating water stress. Sites with lower grass cover contained less soil nitrogen (N) that was also more isotopically enriched, which is indicative of greater ecosystem N losses. These results show that groundwater depth is correlated with a number of ecosystem traits in these Great Basin Desert ecosystems and should be considered when evaluating future changes in groundwater depth.

Carbon stock and its responses to climate change inCentralAsia

“…Current C modeling studies had similar problems in drylands. Although deep roots and related deep‐soil water and C processes were important to the structure and functions of dryland ecosystems (Goedhart & Pataki, ), deep‐soil mechanisms were rarely considered in ecosystem models that have been widely used in regional or global C cycle research (Schimel et al ., ; Tian et al ., ). In comparison, the AEM used in this study can address the root distribution in deep soil and the groundwater uptake process by phreatophytes (Zhang et al ., ).…”

“…Our study further revealed that 65-68% of the SOC in temperate deserts was stored in deep soil (under the top 1 m). Plant roots in desert ecosystems can grow deep into soil in search of water (Goedhart & Pataki, 2011), and SOC in deep soil layers accounted for a remarkable fraction of the full soil profile in deserts (Jobb agy & Jackson, 2000;Wang et al, 2010;Rumpel & K€ ogel-Knabner, 2011). However, previous field soil surveys in Central Asia mainly focused on upper layers within the top 1 m and could have underestimated the C stock in Central Asia (Lioubimtseva & Adams, 2002;Sommer & De Pauw, 2011).…”

Do groundwater dynamics drive spatial patterns of tree density and diversity in Neotropical savannas?

“…). Soil moisture and soil water regime have also been assumed to largely affect spatial distribution patterns of tree species along topographic gradients (Groeneveld & Or ; Gottsberger & Silberbauer‐Gottsberger ; Haridasan ; Goedhart & Pataki ; Mata‐Gonzales et al. ).…”

“…Results of these studies, however, have been inconclusive with no clear negative or positive correlations between savanna physiognomies and soil fertility or aluminium availability (Ratter et al 1997;Moreira 2000;Ruggiero et al 2002). Soil moisture and soil water regime have also been assumed to largely affect spatial distribution patterns of tree species along topographic gradients (Groeneveld & Or 1994;Gottsberger & Silberbauer-Gottsberger 2006;Haridasan 2008;Goedhart & Pataki 2011;Mata-Gonzales et al 2012). Long-term quantitative studies of underground water table depth variations along topographic gradients are lacking in Neotropical savannas, therefore it is difficult to assess the effects of water table dynamics on the spatial distribution of woody species, particularly patterns of tree density and species diversity.…”

Mapping Potential Groundwater‐Dependent Ecosystems for Sustainable Management

“…GDEs in the United States occur in a number of potentially stressed ecoregions, particularly the Great Basin in Nevada (Naumburg et al ; Steinwand et al ), the Edwards Plateau in Texas (Jackson et al ; McElrone et al ), the Sonoran Desert in Arizona (Scott et al ), and in California, the Owens Valley (Elmore et al ; Goedhart and Pataki ) and the foothills (Miller et al ) and riparian meadows of the Sierra Nevadas (Loheide et al ; Loheide and Gorelick , ; Lowry et al ). Two distinct types of GDEs are significant for sustainable groundwater development (Eamus et al ): (1) biota living in and around springs, groundwater‐fed wetlands, and riparian zones, all of which rely on the surface expression of groundwater; and (2) vegetation with root access to deeper (more than 2 m) stores of water which require the subsurface presence of groundwater.…”