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1 Smoke-stimulated germination in the post-fire flora of California chaparral does not appear to be triggered by nitrate. Application of freshly prepared unbuffered KNO3 solutions (pH c. 6.2) failed to enhance germination of five populations of Emmenanthe penduliflora or one Phacelia grandiflora population, regardless of light or stratification conditions. 2 KNO3 buffered at acidic pH (or unbuffered solutions equilibrated with atmospheric CO2) did induce germination, but KNO3 solutions at pH 7 failed to induce germination. Induction of germination is therefore not due to the nitrate ion per se, but rather to high [H+], although buffered controls gave weak germination at low pH, suggesting a role for H+ plus nitrate. However, other anions such as sulphate were equally as effective as nitrate at breaking dormancy. 3 The germination response to KNO3 was affected by the type of filter paper used and this may be linked to differences in pH. 4 NO2, at concentrations present in biomass smoke, was highly effective at inducing germination, and other oxidizing agents also induced germination. 5 Several growth regulators, including nitrite and gibberellin, were stimulatory only at acidic pH, but KCN was stimulatory across a broad pH range. 6 Germination decreased at smoke exposures longer than a few minutes. Also, smoked water samples effective at breaking dormancy were acidic and were less effective when buffered to pH >7. 7 Physical scarification of the seed coat induced germination but the effect was not due to penetration of a water barrier, or to enhanced oxygen uptake or to wound responses such as CO2 or ethylene production. 8 Different effects of the gibberellin inhibitor CCC (chlorocholine chloride) suggested that the mechanisms of scarification-induced and smoke-induced germination may differ. 9 We conclude that either oxidizing gases in smoke and/or acids generated on burnt sites play a role in germination of post-fire annuals in chaparral. [ABSTRACT FROM AUTHOR]

Lowman, H.E.; Hirsch, M.E.; Brzezinski, M.A., and Melack, J.M., 2023. Examining the potential of sandy marine sediments surrounding giant kelp forests to provide recycled nutrients for growth. Journal of Coastal Research, 39(3), 442–454. Charlotte (North Carolina), ISSN 0749-0208. Permeable marine sediments are biogeochemically active and may contribute dissolved nutrients to support primary production in coastal regions. This study examined the potential of permeable marine sediments near giant kelp forests in the Santa Barbara Channel, California as a source of ammonium (NH4+) to the overlying water column to support the observed growth of kelp during summer months when nitrate availability is low. Several nearshore sites located in coastal California in <20 m water depth were sampled for porewater nutrient concentrations, flushing rates, and nutrient fluxes in addition to diel fluctuations in nutrient concentrations of the overlying water column. Time-series analyses of porewater temperatures indicate that porewater flushed to a depth of 15 cm approximately every two hours, and mean NH4+ concentrations of porewater at these depths was 40 µM. The results of flow-through bioreactor incubations indicate that the top 2 cm of sediment are a net source of dissolved nitrogen to the overlying water column and are capable of supplying from 0.05 to 0.90 mmol NH4+ m–2 day–1. Diel water sampling demonstrates that kelp forests may be exposed to NH4+ concentrations greater than 1 µM for multiple hours (four–eight) over a day. These measured reservoirs and exchange rates of NH4+ suggest sandy marine sediments provide a significant source of nitrogen to the water column and may help meet the nitrogen demand by giant kelp during summer in the Santa Barbara Channel. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents an analysis of the aerosol chemical composition, optical properties and size distributions for a range of conditions encountered during a field measurement campaign conducted between July 7–29, 2005 at Point Reyes National Seashore, north of San Francisco, CA. The fractional mass loading derived from hourly measurements of an Aerodyne Mass Spectrometer (AMS) during this period are compared with filter-pack measurements from the Pt. Reyes IMPROVE station with good agreement found between the two if it assumed that chloride is primarily from large sea-salt particles (not measured by the AMS). During the first half of the campaign (July 7–17), conditions at the site were largely maritime while flow during the second half of the campaigns (July 18–29) was influenced by a thermal trough that added a cyclonic twist to the incoming marine air, bringing it from the south with a more extensive over-land trajectory. Neither flow regime was associated with air coming from the San Francisco Bay area to the south. The AMS measurements are partitioned into clear and foggy conditions which are then used to calculate the equivalent molar ratio of ammonium to the sum of sulfate, nitrate and chloride. Ratios calculated from measurements made before the onset of the thermal trough on July 18th were associated with acidic or near-neutral particles. Measurements made after July 18th yield ratios that appear to have excess ammonium. Model calculations of the equilibrium gas-phase mixing ratio of NH3 suggest very high values which we attribute to agricultural practices within the park. Reported as an incidental finding is evidence for the cloud droplet activation of large particles (DP > 0.2 μm) with a corresponding reduction in the single scattering albedo of the non-activated particles, followed by a return in the particle size spectrum to the pre-fog conditions immediately afterwards. [Copyright &y& Elsevier]

Re-examination of data distributions from several forested sites in the eastern Sierra Nevada Mountains shows consistent, positive outliers and skew for NH, NO, and mineral N in resin lysimeters and resin capsules, indicating that most values were low but hotspots of high N flux were present in most cases. Exact causes of these N flux hotspots is not known, but could include water flux hotspots (e.g., preferential flowpaths), microbial hotspots, and possibly the entry of N-enriched O horizon interflow. Soil and resin stake (PRS probe) data from one site (North Lake Tahoe) also showed consistent, positive outliers and skew for NH, NO, and mineral N, suggesting the presence of microbially produced hotspots. Bicarbonate-P data from soils and ortho-P data from PRS probes also showed highly positive skew and extreme outliers, but Bray (HCl/NHF-extractable) P in soils did not. Other measured nutrients (extractable Mg, K, SO, and Ca) also showed positive skew and outliers, but less so than NH, NO, and mineral N. Calcium stood out among measured nutrients as the most abundant nutrient with the least outliers and the lowest (sometimes negative) skew. The differences in distributions of NH, NO, and mineral N and those of Ca may reflect relative abundance: the most abundant ion, Ca, shows little evidence of hotspots whereas the much less abundant ions, NH, NO consistently show evidence of hotspots. We hypothesize that the differing distributions of N and Ca reflect the relative biological competition for these nutrients and that positively-skewed distributions and hotspots will be characteristic of any other nutrient when it is in limited supply relative to biological demand. [ABSTRACT FROM AUTHOR]

In recent years, the extreme eutrophication of the Salton Sea has been associated with massive fish kills and associated bird kills. Analysis of the magnitude and direction of high wind events indicates that major fish kills are preceded by strong and persistent wind events, with a 24-h accumulated wind magnitude above a critical threshold of approximately 90 m/s. Twelve of the 14 cases of reported fish kills analyzed were found to be preceded by such wind conditions. The winds could potentially produce upwellings of hypolimnetic water at the upwind end of the Sea, resulting in the entire water column being low in dissolved oxygen and high in concentrations of hydrogen sulfide and ammonium. Remotely sensed thermal infrared data from the MODIS instrument on the Terra satellite was available for 5 of the 14 fish kills analyzed. Evaluation of satellite-derived surface temperature maps for these 5 fish kills shows that upwellings did take place after the wind events, affecting a large fraction of the Sea’s area. The location of the upwelling and the fish kills coincided in all cases, confirming the relationship among wind patterns, upwellings, and fish kills in the Salton Sea. The importance of physically mediated processes, such as upwellings, need to be considered in evaluating future remediation strategies for the Salton Sea. [ABSTRACT FROM AUTHOR]

Meteorological factors affecting concentration of dissolved inorganic nitrogen in rain were examined. Rain samples were collected on an event basis from a location 100 km east of the Los Angeles Basin. Analysis of the data demonstrated a double decay function where small increases in rain volume resulted in large decreases in nitrogen concentration. In separate time series collections of individual storms, storm wind direction also influenced nitrogen concentrations [ABSTRACT FROM AUTHOR]