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

Vourlitis, George L.; Fernandez, John S.

doi:10.1016/j.jaridenv.2012.02.006

Cited by 17 publications

(21 citation statements)

References 52 publications

(69 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Root structures play an important role for N storage in low N environments (Lipson and others 1996). The N storage capacity of A. fasciculatum roots is at least half as large as for shoots (Vourlitis and Fernandez 2012) and early in the season, prior to any aboveground growth, A. fasciculatum begins to accumulate fine root biomass (Kummerow and others 1978). A. fasciculatum has a well-developed lignotuber (Moreno and Oechel 1991) and, although lignotubers are most commonly associated with resource replenishment following a disturbance (James 1984), it is conceivable that lignotubers also facilitate seasonal N storage.…”

Section: Discussionmentioning

confidence: 99%

“…A. fasciculatum (Vourlitis and Fernandez 2012) and other shrubs native to chaparral are N conserving (Gray and Schlesinger 1983), whereas annual nonnative plants have a more open N cycle (Jackson and others 1988;Parker and Schimel 2010). In annual plants 15 N retrieval, at peak biomass, was twice as high as in A. fasciculatum despite higher biomass and N content of shrubs.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

The Influence of Altered Rainfall Regimes on Early Season N Partitioning Among Early Phenology Annual Plants, a Late Phenology Shrub, and Microbes in a Semi-arid Ecosystem

et al. 2014

View full text Add to dashboard Cite

In Mediterranean-type ecosystems, nitrogen (N) accumulates in soil during dry summer months and rapidly becomes available during early season rain events. The availability of early season N could depend on the size of rainfall events, soil microbial activity, and phenology of the plant community. However, it is poorly understood how precipitation patterns affect the fate of early season N. Microbes and plants with early phenology may compete strongly for early season N but theory suggests that microbial N storage can meet plant N demands later in the season. Using a 15 N tracer and rainfall manipulation we investigated the fate of early season N. N allocation patterns differed substantially between microbes, early and late phenology plants. As expected early phenology annuals and microbes took up 15 N, within 1 day, whereas a latephenology shrub allocated 15 N to leaves later in the season. We saw no evidence for microbial storage of early season N; the peak of 15 N in shrub leaves did not coincide with detectable levels of 15 N in the microbial biomass or labile soil pool. This suggests that shrubs were able to access early season N, store and allocate it for growth later in the season. Although we saw no evidence of microbial N storage, N retention in soil organic matter (SOM) was high and microbes may play an important role in sequestering N to SOM. Plant N uptake did not respond significantly to 1 year of rainfall manipulation, but microbes were sensitive to dry conditions. 1 year after 15 N addition shrubs had resorbed up to half of the N from leaves whereas N in annuals remained as dead leaf litter. Differences in end-of-season N partitioning between dead and living biomass in the two vegetation types suggest that plant species composition could affect N availability in the following growing season, but it may take several years of altered precipitation patterns to produce rainfall-dependent changes.

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

The Influence of Altered Rainfall Regimes on Early Season N Partitioning Among Early Phenology Annual Plants, a Late Phenology Shrub, and Microbes in a Semi-arid Ecosystem

et al. 2014

View full text Add to dashboard Cite

show abstract

“…As an alternative to using indicators of N-saturation, N-budgets have been shown to be useful (Fenn and others 2008), particularly when estimating N-retention in N-fertilizer addition studies (Vourlitis and Fernandez 2012). However, we raise two concerns regarding the ability of N-budgets, based on an annual timescale, to signal when Mediterraneantype ecosystems reach N-saturation (that is, saturation of all sinks).…”

Section: Application Of Indicators Of N-saturation and N-budgets To Xmentioning

confidence: 97%

“…With increasing N supply, N outputs should begin to balance N inputs, eventually shifting to net N losses during ecosystem saturation (Stoddard 1994). Although this approach may be used to understand how much N was retained by an ecosystem on an annual basis (Fenn and others 2008;Vourlitis and Fernandez 2012), it requires intensive sampling of N fluxes. Annual N-budgets may also be sensitive to the episodic nature of fluxes in xeric landscapes, and may suggest N-saturation (that is, saturation of all N sinks) despite ecosystem components remaining N-limited.…”

Section: Introductionmentioning

confidence: 99%

Assessing Nitrogen-Saturation in a Seasonally Dry Chaparral Watershed: Limitations of Traditional Indicators of N-Saturation

et al. 2014

View full text Add to dashboard Cite

To evaluate nitrogen (N) saturation in xeric environments, we measured hydrologic N losses, soil N pools, and microbial processes, and developed an N-budget for a chaparral catchment (Sierra Nevada, California) exposed to atmospheric N inputs of approximately 8.5 kg N ha -1 y -1. Dual-isotopic techniques were used to trace the sources and processes controlling nitrate (NO 3 -) losses. The majority of N inputs occurred as ammonium. At the onset of the wet season (November to April), we observed elevated streamwater NO 3 -concentrations (up to 520 lmol l -1 ), concomitant with the period of highest gaseous N-loss (up to 500 ng N m -2 s -1 ) and suggesting N-saturation. Stream NO 3 -d 15N and d 18O and soil N measurements indicate that nitrification controlled NO 3 -losses and that less than 1% of the loss was of atmospheric origin. During the late wet season, stream NO 3 -concentrations decreased (to <2 lmol l -1 ) as did gaseous N emissions, together suggesting conditions no longer indicative of N-saturation. We propose that chaparral catchments are temporarily N-saturated at £ 8.5 kg N ha -1 y -1 , but that N-saturation may be difficult to reach in ecosystems that inherently leak N, thereby confounding the application of N-saturation indicators and annual N-budgets. We propose that activation of N sinks during the typically rainy winter growing season should be incorporated into the assessment of ecosystem response to N deposition. Specifically, the N-saturation status of chaparral may be better assessed by how rapidly catchments transition from N-loss to N-retention.

show abstract

“…These high N inputs increase N availability through direct fertilization and N mineralization (Michalski et al, 2004;Sirulnik et al, 2007;. Increases in N availability also cause tissue and litter N-enrichment and a decline in C:N ratios (Fenn et al, 2003b;Vourlitis and Fernandez, 2012), an increase in net primary production (NPP) (Pasquini and Vourlitis, 2010;Vourlitis, 2012), and changes plant species composition (Zavaleta et al, 2003;). However, there may be a threshold of N input, or a "critical load" (Cresser, 2000), where the ecosystem capacity to utilize and immobilize N is exceeded (Groffman et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

Carbon and nitrogen mineralization of semi-arid shrubland soils exposed to chronic nitrogen inputs and pulses of labile carbon and nitrogen

Vourlitis

Fernandez

2015

Journal of Arid Environments

View full text Add to dashboard Cite

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

Cited by 17 publications

References 52 publications

The Influence of Altered Rainfall Regimes on Early Season N Partitioning Among Early Phenology Annual Plants, a Late Phenology Shrub, and Microbes in a Semi-arid Ecosystem

The Influence of Altered Rainfall Regimes on Early Season N Partitioning Among Early Phenology Annual Plants, a Late Phenology Shrub, and Microbes in a Semi-arid Ecosystem

Assessing Nitrogen-Saturation in a Seasonally Dry Chaparral Watershed: Limitations of Traditional Indicators of N-Saturation

Carbon and nitrogen mineralization of semi-arid shrubland soils exposed to chronic nitrogen inputs and pulses of labile carbon and nitrogen

Contact Info

Product

Resources

About