Disturbia: The Real Dirt on Palos Verdes PeninsulaDisturbia: The Real Dirt on Palos Verdes Peninsula

Victoria Zamora1, Kimberly Boyd1, Jade Dean2, Karryssa Fenderson3, Marylynn Roun3, Christine M. Rodrigue4, Paul Laris4, Lora Stevens4

1Long Beach Polytechnic High School,2 Long Beach City College,3Woodrow Wilson Classical High School,4CSU-Long Beach

Coastal Sage Scrub (CSS) is a unique plant community because it is found only in Southern California and it supports several endangered species. CSS plants survive in nutrient poor soils. It is usually found along Southern California’s Coast including the Palos Verdes Peninsula. Over the last century, however, invasive species have been able to thrive and out-compete natives on the peninsula. The reasons for their success remain a mystery. This project is the preliminary assessment of differences in edaphic properties of disturbed and undisturbed areas. Samples were taken from two sites which contain both mechanically disturbed and undisturbed areas: Three Sisters and Portuguese Bend (Figures 1-3). Soil properties studied included pH, salinity, grain size, and organic/inorganic carbon content. We hypothesize that soils within disturbed areas have been altered so that they are no longer able to support native vegetation.

Introduction

Methods

Conductivity/ Salinity

Minerals

Grain SizeOrganic Matter

We hypothesized there would be a difference in the soil properties of disturbed and undisturbed sites. We found organic matter and grain size showed the greatest difference. Undisturbed sites had much higher levels of organic carbon than disturbed sites (27;2%). There was a much higher percent of clay in the disturbed sites and a higher percent of silt in the undisturbed. Its not surprising that there is more organic carbon in the undisturbed, because of the high leaf litter from CSS. The finding that disturbed sites have higher clay percentages is in agreement with finding from the other study group, and reflects the fact that plowed areas tended to be more level and have deeper, finer soils. These finer soils were also dominated by non-native grasses. According to the USDA, one would expect to find calcium in areas with high pH. We found that many of our neutral to basic soils had recognizable amounts of calcite. Its not surprising to find the undisturbed to have higher conductivity, which one expects in a semi-arid environment. Perhaps the disturbed sites have lower values due to farming and irrigation.

In the field we used 3 m x 3 m quadrats to sample plant diversity and soil characteristics of our study area. Quadrat locations were chosen using aerial photography to determine disturbance history of the area. Both plowed and intact areas were sampled.

In the lab we used several techniques to test soil properties (figure 4). Inorganic and organic carbon content was determined using a UIC Inc.® coulometer. Mineral identification was done using X-ray diffraction (XRD); soil samples were crushed, mixed with alcohol, and spread onto glass slides (Engleman et al., 1985). Next using the Lewis and McConchie technique (1994), we found the percentage of the different grain sizes in the sediment samples. Lastly, samples were turned into a mixture using nanopure water in a 2:1 ratio and then tested with a YSI™ meter to determine both the pH and conductivity of the solutions.

•pH in undisturbed sites ranges from 6.7 to 8.15 and disturbed sites from 7.2 to 7.9 (see figure)

•Conductivity in undisturbed sites : 113 -1529 mS; disturbed sites 547.9-1451 mS(see figure)

•Grain size of undisturbed is characterized as clay loam and disturbed as clay (see figure)

•Undisturbed sites have a higher percentage of total carbon than disturbed areas (see figure)

Study Sites

DiscussionResults

Acknowledgements

Summary of Results pH

Undisturbed

DisturbedA summary of the results is shown below. We found that pH values were slightly high in the undisturbed sites. Conductivity was also higher in the undisturbed sites. Organic matter and especially organic carbon was much higher in the undisturbed plots while disturbed plots were found to have higher percentage clay content. In terms of minerals, quartz was the most abundant and found on all plots. Calcite was found in most of the undisturbed plots, while magarite was found mostly in disturbed sites. Geothite and whitlockite were only found in the disturbed mustard site.

Engleman, E.E., Jackson, L.L., Norton, D.R., Fisher, A.G., 1985. Determination of carbonate carbon in geologic materials by coulometric titration. Chemical Geology 53, 125-128.

Lewis, D.W. & McConchie, D. 1994. Analytical Sedimentology. Chapman and Hall, New York, pp. 94-108.

Talluto, M.V. and Suding, K.N. 2008. Historical change in coastal sage scrub in southern California, USA in relation to fire frequency and air pollution. Landscape Ecology, 23:803-815.

Soulé, Michael E.; Alberts, Allison C.; and Bolger, Douglas T. 1992. Oikos 63, 1: 39-47.

Conclusion

This study concludes that mechanically disturbed sites are more likely to have low organic carbon, more clay content, and lower salinity (conductivity). We did not find any obvious differences in soil minerals or pH levels between disturbed and undisturbed sites. Furthermore, the differences in soil texture are likely a function of topography and not a result of the mechanical disturbance itself, whereas the high carbon levels found on CSS plots is probably due to the higher leaf litter associated with this plant community. Further research should explore the differences in nitrogen content between the two types as nitrogen has been known to favor invasive grasses over CSS (Talluto, M.V. and Suding 2008).

References

I would like to thank: The National Science Foundation Award #0703798 for funding GDEP Track 2, the Palos Verdes Peninsula Land Conservancy for allowing us to use their land, Brian Nagy for technical support, Jason Manack and Hazel for the support and help Drs. Paul Laris and Chrys Rodrigue for helping and guiding me with my project along with Daniel Cardoza, Karryssa Fenderson, Marylynn Roun, and Jade Dean for their continued help and support. Thanks to the everyone in the “Rock the Water” group who helped me including Lizbeth Rodriguez, Valerie De Jesus, Yoshi Maezumi, and of course Lora Stevens. And always thanks to my Mommy.

Figure 1

Figure 2

Figure 3

Figure 4: Photo credit Kim Boyd