The Effects Of Alluvial Sediment Hardness On Coastal Sage Scrub On The Land Lab At CSUSB

Event Center A & B

The Land Lab at CSUSB is inhabited by endangered coastal sage scrub. The vegetation in part of the Land Lab was destroyed when a large amount of sediment was dumped on top during construction of parking structures in 2007. Three previous studies measured the penetrability of the alluvial sediment. The first trial showed a dramatic decrease in penetrability of the disturbed sediment relative to the undisturbed land. The second trial showed further decrease in penetrability. The third and fourth trials showed a further slight decrease. The penetrability levels in this area, (both disturbed and undisturbed areas), decreased well after the dirt piles were removed (2007 vs. 2011). Clearly, something else was causing this continued decrease in penetrability. Caliche build-up from precipitation may be a factor to the difficulties in penetration of the alluvial sediment of the Land Lab. Following this theory, the annual precipitation values from the University’s weather station were compared to the penetrability data. This comparison showed that both followed the same trend. The precipitation year 2010-2011 showed the highest rainfall. This is also the same year the penetrability of the alluvial sediment was at its highest. This supports the idea that caliche may have been mobilized during the years with the highest precipitation. Caliche then precipitated in the sediment pore spaces and partially cemented the sediment. The data have been fairly consistent suggesting that in the past two years with very little rain, there was little addition to the formation of caliche, or mobilization of the existing caliche.