Asymbiotic nitrogen fixation and denitrification in a mature forest in coastal British Columbia

1989 ◽  
Vol 19 (9) ◽  
pp. 1194-1200 ◽  
Author(s):  
G. H. Cushon ◽  
M. C. Feller
Keyword(s):  
British Columbia ◽  
Nitrogen Fixation ◽  
Forest Floor ◽  
Mineral Soil ◽  
Gaseous Nitrogen ◽  
Blue Green Algae ◽  
Asymbiotic Nitrogen Fixation ◽  
Nitrogen Inputs ◽  
Decaying Wood ◽  
Floor Material

Gaseous nitrogen inputs due to asymbiotic nitrogen fixation and outputs due to biological denitrification were estimated for a mature mid-successional Pseudotsugamenziesii (Mirb.) Franco–Thujaplicata Donn–Tsugaheterophylla (Raf.) Sarg. forest in southwestern British Columbia. Forest floor material, mineral soil, decaying wood, foliage, and bark were incubated in an atmosphere of 10 kPa C2H2 to allow the simultaneous measurement of N2O production by denitrifying bacteria and C2H2 reduction by free-living bacteria and blue-green algae. Forest floor material accounted for 70% of an estimated total annual nitrogen fixation of 0.3 kg N•ha−1•year −1.•Relatively small amounts of nitrogen were fixed in mineral soil, decaying wood, and foliage, and no indication of nitrogen fixation activity in bark was detected. Some denitrification was found; it was essentially negligible, although possibly underestimated. The net gaseous nitrogen input into the mid-successional forests of the study area is likely to be < 5% of the total net nitrogen inputs, which are primarily from precipitation.

scholarly journals Post-harvest nitrogen cycling in clearcut and alternative silvicultural systems in a montane forest in coastal British Columbia

2006 ◽  
Vol 82 (6) ◽  
pp. 844-859 ◽  
Author(s):  
Brian D Titus ◽  
Cindy E Prescott ◽  
Doug G Maynard ◽  
Alan K Mitchell ◽  
Robert L Bradley ◽  
...  
Keyword(s):  
British Columbia ◽  
Nitrogen Cycling ◽  
N Mineralization ◽  
Forest Floor ◽  
Mineral Soil ◽  
Soil Horizon ◽  
Thuja Plicata ◽  
N Availability ◽  
Foliar N ◽  
Alternative Silvicultural Systems

The MASS (Montane Alternative Silvicultural Systems) trial was established in the coastal mountains of British Columbia to compare clearcut, patch cut, green tree and shelterwood systems. A number of studies were carried out at the MASS trial to determine the extent to which these variable levels of stand retention retained old-growth attributes of N cycling and associated ecological processes. Harvesting led to increases in N mineralization in the forest floor (2×) and mineral soil (10×), and fluxes of N through the upper 25 cm of mineral soil (2× to 3×). However, fluxes of N were not large (< 0.35 kg ha-1 per growing season). Nitrogen mineralized was predominantly ammonium and not nitrate in the forest floor (> 95% in all but clearcut, > 75% in clearcut) and upper mineral soil horizon (42–86%). The nitrate component came from heterotrophic decomposition of organic matter, not conversion of ammonium to nitrate by autotrophs, and nitrate increases resulted from decreased gross nitrate consumption with harvesting, rather than increased nitrate production. The increases in soil N availability resulting from harvesting were reflected in only slight increases in seedling foliar N concentrations for two to four years after logging (peak of ~ 2% for western hemlock and ~ 1.6% for amabilis fir) before decreasing to below deficiency thresholds for both species. Overall, estimated losses of N from the rooting zone after harvesting (1 kg ha-1 yr-1) were minimal in comparison to estimated N inputs (4 kg ha-1 yr-1), N exports in logs at harvesting (250 kg ha-1) and soil reserves (11 400 kg ha-1). Although unlikely to affect future site productivity, losses of N could be reduced somewhat through the use of shelterwood harvesting. Key words: alternative silvicultural systems, variable retention harvesting, nitrogen cycling, litterfall, decomposition, nitrification, N mineralization, microbial ecology, leaching, foliar N, Abies amabilis, Tsuga heterophylla, Thuja plicata

Denitrification and nitrogen fixation in floodplain successional soils along the Tanana River, interior Alaska

1993 ◽  
Vol 23 (5) ◽  
pp. 956-963 ◽  
Author(s):  
K.M. Klingensmith ◽  
K. Van Cleve
Keyword(s):  
Nitrogen Fixation ◽  
Forest Floor ◽  
Nitrogenase Activity ◽  
Mineral Soil ◽  
White Spruce ◽  
Interactive Effects ◽  
Successional Stage ◽  
Alder Forest ◽  
Mineral Soils ◽  
Soil Interface

Forest floors and mineral soils from early (open willow), middle (poplar–alder), and late (white spruce) floodplain primary successional stages were examined for nitrogen fixation and denitrification. The acetylene-reduction and acetylene-inhibition techniques were used separately and in combination to measure nitrogenase and denitrification activities, both in laboratory and field studies. In situ N2O production was undetectable at all sites and during all sampling periods. Denitrifying activity measured in the field with acetylene amendments was low to undetectable, except after a brief flood in the open willow stand when N2O production ranged from undetectable to 34 ng N•cm−2•h−1 within the newly deposited alluvium–old mineral soil interface. Intact core assays also had low to undetectable denitrification activities; the highest activities (259 ng N•g−1 h−1) were measured in the poplar–alder forest floor in the fall. Laboratory studies showed that potential denitrification enzyme activity (DEA) was also greatest in the poplar–alder forest floor (4332 ng N•g−1•h−1), once again occurring in the fall. In early and midsuccessional stages, the interactive effects of temperature, carbon, and NO3− limited denitrification, yet even with the addition of the limiting amendments, low to undetectable DEA was observed in mineral soils. The later white spruce successional stage also had low to undetectable DEA, increasing only with the addition of the full DEA media and independent of temperature changes. Nonsymbiotic nitrogenase activities were highly variable, ranging from undetectable to 30 ng N•cm−2•h−1. Highest activities were seen in the open willow, newly deposited alluvium–old mineral soil interface immediately after a flood and approximately 1 month after the flood on the newly deposited silt surface. Only the white spruce forest floor had measurable nonsymbiotic nitrogenase activity at all sampling times. Alder root nodule nitrogenase activity showed no significant differences between sampling periods. The estimated annual nitrogen fixation rate of 164 kg N•ha−1 for alder root nodules is a substantial N contribution to the alder stand and to the floodplain ecosystem in general.

Effects of broadcast slash burning on fuels and soil chemical properties in the Sub-boreal Spruce Zone of central British Columbia

1987 ◽  
Vol 17 (12) ◽  
pp. 1577-1584 ◽  
Author(s):  
A. M. Macadam
Keyword(s):  
British Columbia ◽  
Forest Floor ◽  
Mineral Soil ◽  
Chemical Properties ◽  
Soil Samples ◽  
Available P ◽  
Soil Layers ◽  
Exchangeable Ca ◽  
Positive Correlations ◽  
Slash Burning

Soil samples were taken before and 9 and 21 months after the operational broadcast burning of logging slash in two clear-cuts in the Sub-boreal Spruce Zone of central British Columbia. Average slash consumption on the two clear-cuts was estimated from line intersect samples at 20 and 24 t/ha and forest floor depth was reduced by 28 and 36%. Nine months after burning, soil N had decreased by 376 kg/ha (18% of preburn levels) while available P had increased by 37–157 kg/ha. Burning resulted in substantial increases in forest floor base saturation, pH, exchangeable Ca and Mg, and available P. Changes within the 0–15 and 15–30 cm mineral soil layers were variable and in general less pronounced. Significant positive correlations were observed between the consumption of large fuels and postburn changes in forest floor pH and exchangeable Ca and Mg. Changes in forest floor N were negatively correlated with amounts of fine slash consumed. A strongly negative correlation was observed between forest floor depth of burn and changes in forest floor exchangeable K concentrations.

Pathology of conifer seed and timing of germination in high-elevation subalpine fir and Engelmann spruce forests of the southern interior of British Columbia

1999 ◽  
Vol 29 (2) ◽  
pp. 187-193 ◽  
Author(s):  
Jianwen Zhong ◽  
Bart J van der Kamp
Keyword(s):  
British Columbia ◽  
Forest Floor ◽  
Mineral Soil ◽  
Seed Viability ◽  
Low Frequency ◽  
High Elevation ◽  
Subalpine Fir ◽  
Engelmann Spruce ◽  
Black Mold ◽  
Nurse Logs

Unstratified seed of Engelmann spruce (Picea engelmannii Parry) and subalpine fir (Abies lasiocarpa (Hook.) Nutt.) in nylon mesh bags was placed on various natural and disturbed forest floor seed beds in the Engelmann Spruce - Subalpine Fir Zone in the southern interior of British Columbia in September 1995 and recovered just before snow melt in June 1996. Fifty-two and 86% of the viable spruce and fir seed, respectively, had germinated before snowmelt. Germination under snow may be an adaptation of these high-elevation species to short cool growing seasons. Seed viability at recovery was significantly lower on undisturbed forest floor seed beds (spruce, 13%; fir, 12%) than on exposed mineral soil (spruce, 57%; fir, 42%). Viability of seed placed on nurse logs was 38 and 23% for spruce and fir, respectively. Isolation from ungerminated seed yielded a Rhizoctonia sp., an as yet unidentified black mold at high frequencies, and several other seed pathogens at low frequency. Multiple linear regression of the frequency of isolation of Rhizoctonia and black mold on seed viability was highly significant for both tree species. Seed pathogens appear to cause a major loss of seed and seedlings in these forests, and this may explain both the common occurrence of regeneration on nurse logs and the requirement of mineral soil seed beds for adequate regeneration.

Clear-cutting, woody residue removal, and nonsymbiotic nitrogen fixation in forest soils of the Inland Pacific Northwest

1992 ◽  
Vol 22 (8) ◽  
pp. 1172-1178 ◽  
Author(s):  
M.F. Jurgensen ◽  
R.T. Graham ◽  
M.J. Larsen ◽  
A.E. Harvey
Keyword(s):  
Nitrogen Fixation ◽  
Pacific Northwest ◽  
Forest Floor ◽  
Prescribed Burning ◽  
Mineral Soil ◽  
Western Montana ◽  
Subalpine Fir ◽  
Residue Removal ◽  
Clear Cutting ◽  
Northern Idaho

The effect of clear-cutting and woody residue removal on soil nonsymbiotic nitrogen fixation, as estimated by the acetylene reduction technique, was investigated on a subalpine fir (Abieslasiocarpa (Hook.) Nutt.) site in western Montana and on a cedar (Thujaplicata (Donn ex D. Don) Lindl.)–hemlock (Tsugaheterophylla (Raf) Sarg.) site in northern Idaho. Nitrogen fixation in the forest floor, soil wood, and mineral soil on the subalpine fir site averaged 0.9 kg N•ha−1•year−1 in the uncut stand. This nitrogen input was reduced by 10% after clear-cutting followed by prescribed burning, and by 22% after clear-cutting followed by intensive residue removal. Nitrogen fixation in the uncut cedar–hemlock stand averaged 1.1 kg N•ha−1•year−1 and was reduced by 26% after prescribed burning. Clear-cutting only and clear-cutting followed by intensive woody residue removal had little effect on nitrogen fixation. However, large amounts of woody residue left on the cut site nearly doubled the amounts of nitrogen fixation compared with the uncut stand. Lower nitrogen fixation after harvesting on both the Idaho and Montana sites was due mostly to reductions in forest floor and large woody residue. Replacement of nitrogen losses from prescribed burning on these sites by nonsymbiotic nitrogen fixation and precipitation would take from 150 to 400 years, depending on the severity of the bum treatments.

scholarly journals Factors Influencing Spatial Variability in Nitrogen Processing in Nitrogen-Saturated Soils

2001 ◽  
Vol 1 ◽  
pp. 505-513 ◽  
Author(s):  
Frank S. Gilliam ◽  
Frank C.C. Somerville ◽  
Frank N.L. Lyttle ◽  
Frank M.B. Adams
Keyword(s):  
Spatial Variability ◽  
N Mineralization ◽  
Forest Floor ◽  
Mineral Soil ◽  
Nitrifying Bacteria ◽  
Saturated Soils ◽  
N Saturation ◽  
Net N Mineralization ◽  
Net Nitrification ◽  
Floor Material

Nitrogen (N) saturation is an environmental concern for forests in the eastern U.S. Although several watersheds of the Fernow Experimental Forest (FEF), West Virginia exhibit symptoms of N saturation, many watersheds display a high degree of spatial variability in soil N processing. This study examined the effects of temperature on net N mineralization and nitrification in N-saturated soils from FEF, and how these effects varied between high N-processing vs. low N-processing soils collected from two watersheds, WS3 (fertilized with [NH4]2SO4) and WS4 (untreated control). Samples of forest floor material (O1 horizon) and mineral soil (to a 5-cm depth) were taken from three subplots within each of four plots that represented the extremes of highest and lowest rates of net N mineralization and nitrification (hereafter, high N and low N, respectively) of untreated WS4 and N-treated WS3: control/low N, control/high N, N-treated/low N, N-treated/high N. Forest floor material was analyzed for carbon (C), lignin, and N. Subsamples of mineral soil were extracted immediately with 1 N KCl and analyzed for NH4+ and NO3-to determine preincubation levels. Extracts were also analyzed for Mg, Ca, Al, and pH. To test the hypothesis that the lack of net nitrification observed in field incubations on the untreated/low N plot was the result of absence of nitrifier populations, we characterized the bacterial community involved in N cycling by amplification of amoA genes. Remaining soil was incubated for 28 d at three temperatures (10, 20, and 30°C), followed by 1 NKCl extraction and analysis for NH4+and NO3-. Net nitrification was essentially 100% of net N mineralization for all samples combined. Nitrification rates from lab incubations at all temperatures supported earlier observations based on field incubations. At 30°C, rates from N-treated/high N were three times those of N-treated/low N. Highest rates were found for untreated/high N (two times greater than those of N-treated/high N), whereas untreated/low N exhibited no net nitrification. However, soils exhibiting no net nitrification tested positive for presence of nitrifying bacteria, causing us to reject our initial hypothesis. We hypothesize that nitrifier populations in such soil are being inhibited by a combination of low Ca to Al ratios in mineral soil and allelopathic interactions with mycorrhizae of ericaceous species in the herbaceous layer.

scholarly journals Decomposition rates of surface and buried forest-floor material

2017 ◽  
Vol 47 (8) ◽  
pp. 1140-1144 ◽  
Author(s):  
Cindy E. Prescott ◽  
Anya Reid ◽  
Shu Yao Wu ◽  
Marie-Charlotte Nilsson
Keyword(s):  
Forest Floor ◽  
Mineral Soil ◽  
Site Preparation ◽  
Soil C ◽  
Mechanical Site Preparation ◽  
C Stocks ◽  
Mesh Bags ◽  
Regional Climates ◽  
Floor Material

Mechanical site preparation is assumed to reduce soil C stocks by increasing the rate at which the displaced organic material decomposes, but the evidence is equivocal. We measured rates of C loss of forest-floor material in mesh bags either placed on the surface or buried in the mineral soil at four sites in different regional climates in British Columbia. During the 3-year incubation, buried forest-floor material lost between 5% and 15% more C mass than material on the surface, with the greatest difference occurring at the site with the lowest annual precipitation. Studies of the long-term fate of buried and surface humus are needed to understand the net effects of site preparation on soil C stocks.

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