PARENT SESSION
Poster Session #72: Water Relations II.
Friday, August 9. Presentation from 8:00 AM to 9:30 AM. Exhibit Hall B & C, TCC
133
Hydraulic lift: Evidence of soil moisture redistribution by Prosopis glanduosa in a semi-arid savanna parkland in southern Texas.
ARCHER, S.*,1, BARNES, P.2, ZOU, C.1, MCMURTRY, C.1, JESSUP, K.2, 1 Texas A&M University, College Station, TX, (sarcher@neo.tamu.edu)2 Southwest Texas State University, San Marcos, TX, (PB03@academia.swt.edu)
ABSTRACT- Diel variation in surface (0-50 cm) soil water potential (
s ) was quantified over an annual cycle in upland habitats of a subtropical savanna parkland ecosystem that differed in woody patch development and soils (small discrete tree-shrub clusters on shallow, duplex soils vs. larger, extensive groves on deep, sandy soils). Our objective was to ascertain the influence of soil discontinuities (presence/absence of argillic horizon) on the occurrence and significance of hydraulic lift (HL). Nocturnal increases in surface s were observed intermittently throughout the year, and were most pronounced during spring and autumn when deeply rooted overstory Prosopis glandulosa trees were most active physiologically, and when soil moisture levels were moderate (s = -1 to -3 MPa), but distinctly stratified with depth (dry surface/wet deep soil layers). HL occurred in both habitats, but contrary to expectations, was more frequently detected in clusters (argillic horizon present) than in groves (argillic layer absent) (63 vs 38% of 24 soil psychrometers/habitat). When HL occurred, the average magnitude of diel fluctuations was 0.19 and 0.15MPa in cluster and grove, respectively. Our results document the existence of hydraulic lift in this savanna parkland, but indicate that the process is temporally and spatially variable and strongly influenced by the timing and magnitude of precipitation and edaphic factors that influence soil moisture profiles and plant rooting patterns. Ramifications for growth of understory shrubs are summarized in a companion abstract.
KEY WORDS: argillic horizon, competition, facilitation, overstory-understory interactions