Fog and its influence on the water relations of adult and sapling trees in a coastal California pine forest
Abstract
Following extreme drought in southern California in recent years (2007-2009), widespread tree mortality became evident in a Bishop pine (Pinus muricata) forest on Santa Cruz Island, which harbors the southernmost extent of this rare, endemic, and relictual species in California. Our ability to predict shifts in the distribution of this and other coastal tree species in a drier and possibly less foggy future requires a mechanistic understanding of how this species responds to changes in available moisture, especially summertime fog water inputs that offset drought-like conditions. In this research, we addressed the following questions: Is the water status of Bishop pines affected by fog water inputs? If so, do adult and sapling trees respond differently? Xylem pressure potential (XPP) measurements were used to quantify the physiological response of trees to fog events throughout the rainless summer. We measured saplings and adults through fog events at two sites along a coastal-inland moisture gradient. To quantify fog events in terms of potential plant-available water, we measured fog-drip and shallow soil moisture (0-10 cm) after fog events. We found that adults maintained a lower level of water stress throughout the summer compared to saplings (June XPP: -0.55, -0.54 MPa; September XPP: -0.96, -1.16 MPa, for adults and saplings, respectively). We also found that water stress of Bishop pines declined with increasing shallow soil moisture from fog-drip for both age classes, and this relationship was stronger for sapling (R2=0. 60, p<0.05) than for adult trees (n.s.). These results suggest that water stress in saplings is alleviated by summertime fog more than for adults, and that the mechanism is increased use of shallow soil moisture. These results will contribute to mechanistically based predictions of how coastal forests may respond to a drier climate, which may also become less foggy.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFM.A43B0141B
- Keywords:
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- 0426 BIOGEOSCIENCES / Biosphere/atmosphere interactions;
- 1655 GLOBAL CHANGE / Water cycles