Access

You are not currently logged in.

Access your personal account or get JSTOR access through your library or other institution:

login

Log in to your personal account or through your institution.

Water Source Utilization by Pinus jeffreyi and Arctostaphylos patula on Thin Soils over Bedrock

K. L. Rose, R. C. Graham and D. R. Parker
Oecologia
Vol. 134, No. 1 (Jan., 2003), pp. 46-54
Published by: Springer in cooperation with International Association for Ecology
Stable URL: http://www.jstor.org/stable/4223473
Page Count: 9
  • Download ($43.95)
  • Cite this Item
Water Source Utilization by Pinus jeffreyi and Arctostaphylos patula on Thin Soils over Bedrock
Preview not available

Abstract

Stable isotopes were used to evaluate water sources for co-occurring Jeffrey pine (Pinus jeffreyi Grev & Balf.) and greenleaf manzanita (Arctostaphylos patula Greene) in the southern Sierra Nevada, California, where soils averaged only 75 cm thick but were underlain by up to 5 m of weathered granitic bedrock. Soils and underlying weathered bedrock were sampled three times during both the 1997 and 1998 growing seasons, in 25 cm increments, from 0 to 400 cm or until hard bedrock was reached, and plant stem tissue was sampled simultaneously. Extracted water from the soil/bedrock substrate and plant tissue was analyzed for δ 18O and/or δD, and depth of water source was determined by inference in conjunction with moisture status of the substrate. Water source utilization over the growing seasons for both plants generally followed a pattern similar to that observed for water depletion. Predominant water use was initially from the surface soils. Progressively deeper water sources, including weathered bedrock to a depth of several meters, were exploited as the season progressed and the overlying substrate was depleted of moisture. Early in the growing season, stable isotope values were slightly lower for pine than for manzanita (e.g., average δD in June 1997 was -81‰ for pine and -77‰ for manzanita), and suggest that the functional rooting depth for pine may have been slightly greater than for manzanita. In September 1997, manzanita δD values averaged -57‰ while pine values averaged -85‰, indicating that manzanita opportunistically utilized summer precipitation while pine used more dependable bedrock water. In 1998, soils remained moist through July due to a late snowfall. Unlike the previous year, pine and manzanita δD values were not significantly different in mid- and late-growing season, and both plants exploited bedrock-derived water as soil water was depleted. Water held within bedrock was essential for meeting plant transpirational requirements over the summer drought.

Page Thumbnails

  • Thumbnail: Page 
[46]
    [46]
  • Thumbnail: Page 
47
    47
  • Thumbnail: Page 
48
    48
  • Thumbnail: Page 
49
    49
  • Thumbnail: Page 
50
    50
  • Thumbnail: Page 
51
    51
  • Thumbnail: Page 
52
    52
  • Thumbnail: Page 
53
    53
  • Thumbnail: Page 
54
    54