Carbon and nitrogen storage in soil and litter of southern Californian semi-arid shrublands

Abstract

Semi-arid shrublands of southern California, including chaparral and coastal sage, are found in widely varying elevation and microclimatic regimes and are subjected to disturbance such as fire and atmospheric N deposition that have the capacity to alter soil and litter C and N storage. Here we present a case study where soil and litter C and N were measured over 19 months in post-fire chaparral and mature coastal sage stands to assess whether differences in soil and litter C and N between these diverse shrublands could be attributed to differences in elevation, stand age, rainfall, and/or estimated N deposition exposure. Our results indicate that atmospheric N deposition exposure, either alone or in conjunction with other environmental variables (elevation, rainfall, and/or stand age), was the most frequent predictor of the spatial pattern in the soil and litter N and C variables observed. These results are consistent with those reported for high-elevation coniferous forests arrayed along an N deposition gradient in southern California, suggesting that N deposition may affect the soil N and C storage of semiarid shrublands and woodlands in a qualitatively similar manner.

Soil nitrogen cycling is resilient to invasive annuals following restoration of coastal sage scrub

“…The lack of divergence in total soil C and N, extractable P and pH from invaded to long-term restored treatments may reflect a high level of resistance to exotic plant invasion. The impacts of invasion may not be greater than the known influence of environmental variables such as elevation or precipitation (Vourlitis et al, 2007). It may also be that native shrubs and exotic grasses are insufficiently different in chemistry to cause changes in litter chemistry.…”

Impacts of chronic N input on the carbon and nitrogen storage of a postfire Mediterranean‐type shrubland

“…Chaparral shrublands in urban basins of Southern California can be exposed to 2.5–5.0 g N m −2 yr −1 [ Fenn et al ., ] and up to 14.5 g N m −2 yr −1 at higher elevations [ Fenn and Poth , ; Fenn et al ., ]. Atmospheric N inputs increase total and available N through direct fertilization and an increase in N mineralization, promote losses of N from gaseous efflux and leaching, and enhance soil acidification [ Fenn et al ., ; Vourlitis et al ., , , ; Vourlitis and Fernandez , ; Homyak and Sickman , ]. Because chaparral plant growth and net primary production is thought to be N limited [ Kummerow et al ., ; McMaster et al ., ; Gray and Schlesinger , ; Vourlitis , ], N enrichment from chronic N deposition has the capacity to alter the successional trajectory of ecosystem C and N accumulation.…”

Changes in the soil, litter, and vegetation nitrogen and carbon concentrations of semiarid shrublands in response to chronic dry season nitrogen input

“…The increase nitrification leads to higher rates of NO 3 leaching (Fenn and Poth, 1999;Meixner and Fenn, 2004), a decline in soil pH ' Wood et al, 2007, and an increase in nitric oxide (NO) emission (Anderson and Poth, 1989;Fenn et al, 1996). In turn, increases in N availability consistently lead to tissue and litter N-enrichment and a decline in C:N ratios, especially when N inputs are sustained over a long period of time (Fenn et al, 2003b;Vourlitis et al, 2007b). Nitrogen-enrichment has also lead to changes in plant species composition , and often, an increase in the abundance of annual plants, especially non-native grasses (Minnich and Dezzani, 1998;Pasquini and Vourlitis, 2010;Sirulnik et al, 2007).…”