Vegetation as affected by groundwater depth and microtopography in a shallow aquifer area of the Great Basin

This study was designed to better define the nature of the relationship among vegetation, groundwater level and microtopography in an arid area where depth to groundwater (DTW) was 04 m. Plant cover, DTW and relative elevations were jointly measured along 67 vegetation transects throughout the Owens Valley, CA, USA. These transects were dominated by major species of the area: Artemisia tridentata, Atriplex torreyi, Ericameria nauseosa, Distichlis spicata, Juncus arcticus, Leymus triticoides, Sarcobatus vermiculatus and Sporobolus airoides. Plant species occurrence was associated with different DTW. J. arcticus and D. spicata occurred more frequently in areas with the shallowest groundwater (< 1.5 m). A. torreyi, L. triticoides and E. nauseosa dominated areas with intermediate DTW (1.5-2.0 m); whereas S. airoides, S. vermiculatus and A. tridentata dominated areas with deeper water tables (> 2.0 m). Species were also linked to different microtopographic positions: L. triticoides and J. arcticus were mainly restricted to depressions whereas A. torreyi and A. tridentata were widely distributed in higher positions on the microtopographical gradient. Only 6% of the variation in vegetation cover was accounted for by DTW throughout the study area (N = 820). Cover of individual species was usually unaffected by DTW variation. Results suggest that species distribution is linked to groundwater conditions, but cover of vegetation is only partially affected by DTW variation. This is possible because water tables in our study area are within the rooting depth of most species and plants appear to be well adapted to shallow DTW variations. Copyright (c) 2011 John Wiley & Sons, Ltd.