Relationship Between Biological Soil Crusts and Desert Shrub

Relationship Between Biological Soil Crusts and Desert Shrub Cover Presented By: Matthew Bridges (UC Davis), Kea Rutherford (UC Berkeley), Zach Jordan (UC Santa Cruz), Sandy Gad (UC Riverside), Tiffany Alvarado (UCLA)

Let’s Talk About Soil ❖ Civilization rise and fall ❖ Easter Island- sound familiar? ❖ NONRENEWABLE resource

Desert Soil Crusts

Major Functions of Soil Crusts

Research Question Central Question: What is the relationship between soil crust thickness and aspect on shrub cover? ❖ Explanatory Variable: Soil crust thickness ❖ Explanatory Variable: Aspect ❖ Response Variable: shrub percent coverage ❖ Covariate (explanatory): soil moisture

Methods Crust thickness sample must be taken with a quadrat Vegetation measured using a line-intercept transect of 30 m Random number (120) selection out of a plastic bag Estimate center of hill for starting point Soil moisture sample taken at 15 m mark of transects 2 & 4 10 m 20 m Soil crust thickness taken at 10 m & 20 m * Haphazard slope selection * Throw a rock to determine starting point on flats Starting height randomly generated

Transects ❖ Line-Intercept Method ❖ Calculating percent vegetation cover Vegetation = Cover Length covered by vegetation Length of transect

Quadrats

Determining Soil Moisture Content ❖Weigh out 200 g of soil ❖Baked soil ❖Weigh baked soil ❖Use (Wa - Wb)/Wa

Results Question: What is the relationship between soil crust thickness on shrub cover? p>0. 10 R^2=0. 0013

B A A p<0. 01

B B A p<0. 01

A B B p=0. 001

Interpretation ❖ Average soil crust thickness v. Aspect: Flash floods and annual crust disturbance ❖ Water content v. Aspect: Largest particles stay in wash→ Low retention ❖ Shrub coverage v. Aspect: Vegetation capitalization

Connections to Other Research 0. 1<p<0. 05 R^2=0. 098 Ram et. al 2006 suggest that thicker soil crusts decrease plant available moisture

Soil Crusts and Climate Change Red areas indicate high C fixation from Cryptobiotic crusts L. G. Sancho et al.

Thank You!

Citations Ram, Almog, and Yair Aaron. “Negative and Positive Effects of Topsoil Biological Crusts on Water Availability along a Rainfall Gradient in a Sandy Arid Area. ” CATENA 70, no. 3 (August 1, 2007): 437– 42. doi: 10. 1016/j. catena. 2006. 11. 012. Zhang, Yuanming, Asa L. Aradottir, Marcelo Serpe, and Bertrand Boeken. “Interactions of Biological Soil Crusts with Vascular Plants. ” In Biological Soil Crusts: An Organizing Principle in Drylands, edited by Bettina Weber, Burkhard Büdel, and Jayne Belnap, 226: 385– 406. Cham: Springer International Publishing, 2016. doi: 10. 1007/978 -3 -319 -30214 -0_19.