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Abstract Detail


Ecophysiology

Zimmerman, Shawna [1], Rosentreter, Roger [2], Serpe, Marcelo [1].

Effects of lichen-dominated biological soil crusts on seed water status and root penetration of two annual grasses.

Biological soil crusts can affect seed germination and seedling establishment. We have investigated the effect of biological soil crusts on seed water status as a potential mechanism affecting germination. The seed water potential of two annual grasses, Bromus tectorum and Vulpia microstachys, were analyzed after placing the seeds on bare soil, on a crust that contains a variety of lichens and mosses (mixed crust), or on a crust dominated by the crustose lichen Diploschistes muscorum (lichen crust). For the two grasses studied, seed water potential was significantly higher on the bare soil and mixed crust than on the lichen crust. These differences in water potential correlated with differences in germination, which was much lower on the lichen crust. The three seedbed surfaces received the same amount of water and initially all reached high water potentials. However, differences in water potential developed between watering events. Between waterings, the water potential of the soil and mixed crust remained above -0.5 MPa, while there was a marked decline in the water potential of the lichen surface to about to -4 MPa. To ascertain that water was the main factor limiting germination on the lichen crust, we conducted germination tests in an environment with 100% relative humidity. Under these conditions, germination on the lichen crust was similar to that on the bare soil. The seeds that germinated on the lichen crust did not penetrate, however, this surface and their root tips became necrotic. Our results indicate that the presence of crustose lichens can inhibit seedling establishment by two mechanisms, a reduction in seed water absorption and an inhibition of root penetration.


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1 - Boise State University, Department of Biology, 1910 University Drive, Boise, Idaho, 83725-1515, USA
2 - USDI Bureau of Land Management, Boise, Idaho, 83709, USA

Keywords:
biological soil crusts
water potential
root penetration.

Presentation Type: Poster:Posters for Topics
Session: P
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM
Number: P69005
Abstract ID:1150


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