The influence of dominant plants on water dynamics at a semiarid grassland-shrubland ECOTONE: implications for the recruitment of <i>Larrea tridentata</i>

TitleThe influence of dominant plants on water dynamics at a semiarid grassland-shrubland ECOTONE: implications for the recruitment of Larrea tridentata
Publication TypeConference Paper
Year of Publication1999
AuthorsHochstrasser T., Peters DC
Conference Name84th Annual Meeting, Ecological Society of America
Date PublishedAugust 8-12, 199
Conference LocationSpokane, WA
ARIS Log Number100398
AbstractWe evaluated the effects of dominant grasses and shrubs on soil water dynamics and recruitment success at a grassland-shrubland ecotone. Microsites around the dominant grass (Bouteloua eriopoda) and the dominant shrub (Larrea tridentata) were observed to support different subdominant plants at the Sevilleta National Wildlife Refuge LTER site in central New Mexico. We hypothesized that these two dominants differ in their influence on soil water dynamics, which, together with soil texture differences, result in differential recruitment between microsites. We were particularly interested in recruitment of shrubs that may promote their invasion into grasslands. We used a daily time-step soil water model to evaluate the effects of different dominant species on the establishment of L. tridentata. We were interested in the effects of these species on light and soil water resources. Our results indicated that, although B. eriopoda plants effectively acquired water during the growing season, recruitment of L. tridentata could occur in these microsites near the end of the growing season when the grass was becoming dormant. This resulted in higher probabilities of recruitment of Larrea in grass-dominated microsites than in shrub microsites. This contrasts with field observations showing that germination of L. tridentata was higher in shrub than grass microsites. Therefore, recruitment is also affected by other factors, including seed availability. These results further our understanding of the dynamics of grass-shrub interactions and provide one mechanism to explain shrub invasion into grasslands.