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California State University San Marcos (2006)

Soil nutrient cycling and storage in semi-arid shrubland ecosystems exposed to high N deposition in Southern California

Zorba-Denison Gypsiana

Titre : Soil nutrient cycling and storage in semi-arid shrubland ecosystems exposed to high N deposition in Southern California

Auteur : Zorba-Denison Gypsiana

Université de soutenance : California State University San Marcos

Grade : Master of Science (2006)

Résumé
Southern California’s geography and expanding population have caused an increasing amount of atmospheric nitrogen (N) deposition into semi-arid shrubland ecosystems. However, the effects of N deposition on semi-arid shrublands of Southern California are still poorly known and must be addressed. This research investigated soil nitrogen storage in several areas of Southern California, which received different levels of exposure to atmospheric nitrogen pollution. Soil samples from five sites of varying atmospheric deposition were analyzed for available and total N, and C, pH and soil organic matter content. The results indicate that soil derived from sites with high pollution exposure had correspondingly higher total N and extractable N, lower pH, and lower C:N ratios than sites with lower pollution exposure. Analysis of resin bags buried below the soil surface (0-1 0 em) showed that accumulation rates of both NH4 and N03 were 1-2 orders of magnitude higher at polluted air sites than at clean air sites, and that soil pH was 0.5 pH point lower in high N pollution sites. These data suggest that atmospheric N deposition can significantly increase soil N storage and rates of N cycling in southern California shrublands. Key words : Nitrogen, carbon, storage, cycling, deposition, C:N, chaparral, coastal sage scrub.

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