The effect of fire severity on ash, and plant and soil nutrient levels following experimental burning in a boreal mixedwood stand

1998 ◽  
Vol 78 (1) ◽  
pp. 35-44 ◽  
Author(s):  
Mark Johnston ◽  
Julie Elliott

The Boreal Mixedwood Ecosystem Study near Thunder Bay, Ontario is a multi-disciplinary investigation of the impacts of harvesting and fire on the structure and function of a boreal mixed-wood ecosystem. The fire component comprises a set of treatments in which fire severity was manipulated by adjusting fuel loadings through a variety of harvesting techniques, and also included fire in standing timber. Intensive fuel sampling before and after the fire enabled detailed determinations of fuel consumption, heat output and forest floor reduction. Nutrient concentrations in ash, soil, and plant tissue following the fire were compared with fire severity in order to quantify potential nutrient inputs and their relationship to the amount of biomass consumed during the fire. Forest floor and woody fuel consumption varied significantly among treatments, with the most important factor being whether or not the stand had been harvested previous to the fire. The pH was highest and P concentrations among the lowest in the ash of unharvested blocks. Nutrient concentrations of the remaining forest floor and upper mineral soil were weakly related to the treatments. Forest floor P concentrations were highest on whole-tree harvested and lowest on uncut blocks. Whole-tree harvested blocks also had the highest pH values in forest floor and mineral soil. Concentrations of N, P, and Mg in the foliage of Populus tremuloides Michx. and Rubus idaeus L. were higher on unharvested burned than cut and burned plots, and were negatively correlated with the depth of forest floor reduction. These results indicate that fire severity plays a role in determining the extent of nutrient enrichment following fire, and may be important in influencing long-term site productivity. Key words: Fire severity, forest fire, nutrient cycles, soil chemistry, fire ecology


1989 ◽  
Vol 19 (6) ◽  
pp. 725-735 ◽  
Author(s):  
O. Q. Hendrickson ◽  
L. Chatarpaul ◽  
D. Burgess

Soil and water chemistry and soil-respiration activity were studied in a mature, mixed conifer and hardwood forest and in adjacent whole-tree harvest (WTH) and conventional harvest (CH) areas dominated by hardwood sprouts. Compared with the uncut mature forest, forest floor contents of N and K were lower in the WTH area 3 years after harvest; Ca and Mg were higher in the CH area, probably owing to inputs in logging slash. Mineral soil Ca and pH were higher in the harvested areas than in the uncut area. During the 2nd year after harvest, cation concentrations in forest floor leachate varied in the order WTH > CH > uncut area, but differences largely disappeared the next year. Soil water NO3 concentrations were slightly elevated in the CH area, but only 1.6 kg N•ha−1•year−1 leached below the rooting zone. Bulk precipitation K and Mg concentrations were lower in the WTH area than in the CH area owing to the loss of canopy leaching from the residual stand. Slightly higher amounts of cations were found in the snowpack under the mature forest canopy. Midwinter rains caused movement of NO3 and H within the snowpack. Despite the higher soil-respiration rates in the harvested areas, no differences in soil organic matter pools were observed relative to the uncut area; harvest-related inputs of slash, decaying roots, and stumps may have offset respiratory carbon losses. Current high nutrient demands of rapidly growing sprouts in the WTH area greatly exceed nutrient inputs in bulk precipitation; this may lead to future growth declines.



Forests ◽  
2020 ◽  
Vol 11 (10) ◽  
pp. 1040
Author(s):  
R. Kasten Dumroese ◽  
Martin F. Jurgensen ◽  
Deborah S. Page-Dumroese

Research Highlights: This experiment compares a range of combinations of harvest, prescribed fire, and wildfire. Leveraging a 30-year-old forest management-driven experiment, we explored the recovery of woody species composition, regeneration of the charismatic forest tree species Larix occidentalis Nutt., and vegetation and soil carbon (C) and nitrogen (N) pools. Background and Objectives: Initiated in 1967, this experiment intended to explore combinations of habitat type phases and prescribed fire severity toward supporting regeneration of L. occidentalis. At onset of the experiment, a wildfire affected a portion of the 60 research plots, allowing for additional study. Our objective was to better understand silvicultural practices to support L. occidentalis regeneration and to better understand the subsequent impacts of silvicultural practices on C and N pools within the vegetation and soil. Materials and Methods: We categorized disturbance severity based on loss of forest floor depth; 11 categories were defined, including controls for the two habitat type phases involved. We collected abundance, biomass, and C and N concentrations for the herbaceous layer, shrubs, and trees using nested quadrats and 6 to 10 experimental units per disturbance category plot. Moreover, we systematically sampled woody residue from transects, and forest floor, soil wood, and mineral soil with a systematic grid of 16 soil cores per disturbance category plot. Results: We found that (1) disturbance severity affected shrub species richness, diversity, and evenness within habitat type phases; (2) L. occidentalis regenerates when fire is part of the disturbance; (3) N-fixing shrub species were more diverse in the hotter, drier plots; (4) recovery levels of C and N pools within the soil had surpassed or were closer to pre-disturbance levels than pools within the vegetation. Conclusions: We confirm that L. occidentalis regeneration and a diverse suite of understory shrub species can be supported by harvest and prescribed fire, particularly in southern and western aspects. We also conclude that these methods can regenerate L. occidentalis in cooler, moister sites, which may be important as this species’ climate niche shifts with climate change.



2000 ◽  
Vol 80 (3) ◽  
pp. 507-514 ◽  
Author(s):  
Sylvain St-Laurent ◽  
Rock Ouimet ◽  
Sylvie Tremblay ◽  
Louis Archambault

Following the Rio and Kyoto protocols, forest sequestration of organic C (Corg) appears to be among the measures to reduce atmospheric C. In this context, we assessed the evolution of soils' reserves of Corg after complete whole-tree forest harvesting in the balsam fir–yellow birch forest of eastern Quebec. The experimental design consisted of eight plots in mature stands, and 10 plots in 7-, 12-, and 22-yr-old clearcuts in the "Seigneurie du Lac Métis", located 80 km south-east of Rimouski, Quebec, Canada. The soil type was an Orthic Humo-ferric Podzol. Major Corg losses occured in the forest floor of the 7-, 12- and 22-yr-old harvested plots compared with mature stands. The FH horizon of harvested plots showed a loss of 44% (−30.5 t ha−1) in dry weight and 13.5% (−62.1 g kg–1) in Corg content between 7 and 22-yr-old harvested plots. More than half the Corg content of the forest floor was lost in that time (−52% or −16.6 t ha−1). The Corg stock of the L horizon were lowered only for the 7-yr-old treatment (2.5 t ha−1) compared with mature stands (4.9 t ha−1). No significant differences in the Corg stocked in the first 30 m of the mineral soil were found between treatments. It appears that the forest floor of balsam fir–yellow birch stands has become a source of Corg for at least 22 yr after forest harvesting. Key words: Forest harvesting, soil, organic carbon, forest floor



1986 ◽  
Vol 16 (4) ◽  
pp. 872-874 ◽  
Author(s):  
O. Q. Hendrickson

Three years after harvesting a mixed conifer–hardwood forest in Ontario, the density of sweet fern (Comptoniaperegrina (L.) Coult.) was far greater on a whole-tree harvest site (logging slash removed) than on an adjacent conventional harvest site (logging slash present). These differences were related to the degree of site disturbance, particularly forest floor removal. Nodule fixation rates also appeared to reflect the degree of disturbance, being highest in plants growing along a logging road where the sandy, nitrogen-poor mineral soil was exposed, and exceptionally low on the conventional harvest site (0.67 μmol C2H4 g dry weight−1 h−1). Overall, acetylene reduction activity showed a significant negative correlation (r = −0.77, p < 0.001) with total N.



2012 ◽  
Vol 42 (8) ◽  
pp. 1456-1466 ◽  
Author(s):  
Suzanne Brais ◽  
Pascal Drouin

Decaying wood contribution to the heterogeneity of forest soils could depend on tree species and wood decay stage. The study was conducted in an 85-year-old trembling aspen ( Populus tremuloides Michx.) – jack pine ( Pinus banksiana Lamb.) forest in northwestern Quebec, Canada. Trees, snags, logs, and forest floor originating from wood buried within the forest floor (lignic FF) and from fine litter (alignic FF) were inventoried in fifteen 400 m2 plots (nine jack pine and six trembling aspen). Chemical properties of alignic and lignic FF and logs were measured and relative nutrient availability in the mineral soil assessed under logs and under lignic and alignic FF using PRS probes. No significant differences between forest covers were found for the proportion of C and nutrients contained in deadwood (snags, logs, and lignic FF) relative to tree biomass plus necromass (deadwood plus alignic FF) content. Lignic FF was characterized by a higher C/N ratio and exchangeable acidity than alignic FF and its nutrient concentrations were between those of alignic FF and logs. Differences in wood characteristics may explain some of the differences in forest floor properties observed between trembling aspen and jack pine. Nutrient availability in the mineral soil was affected by the overlaying materials and could reflect differences in the dynamics of individual nutrients.



2013 ◽  
Vol 10 (7) ◽  
pp. 11899-11933 ◽  
Author(s):  
I. C. Meier ◽  
C. Leuschner

Abstract. Precipitation as a key determinant of forest productivity influences forest ecosystems also indirectly through alteration of the nutrient status of the soil, but this interaction is not well understood. Along a steep precipitation gradient (from 970 to 520 mm yr−1 over 150 km distance), we studied the consequences of reduced precipitation for the soil and biomass nutrient pools and dynamics in 14 mature European beech (Fagus sylvatica L.) forests on uniform geological substrate. We tested the hypotheses that lowered summer precipitation (1) is associated with less acid soils and a reduced accumulation of organic matter on the forest floor, and (2) reduces nutrient supply from the soil and leads to decreasing foliar and root nutrient concentrations. Soil acidity, the amount of forest floor organic matter, and the associated organic matter N and P pools decreased to about a half from wet to dry sites; the C/P and N/P ratios, but not the C/N ratio, of forest floor organic matter decreased. Net N mineralization (and nitrification) rate and the available P and K pools in the mineral soil did not change with decreasing precipitation. Foliar P and K concentrations (beech sun leaves) increased while N remained constant, resulting in decreasing foliar N/P and N/K ratios. N resorption efficiency increased toward the dry sites. We conclude that a reduction in summer rainfall significantly reduces the soil C, N and P pools but does not result in decreasing foliar N and P contents in beech. However, more effective tree-internal N cycling and the decreasing foliar N/P ratio towards the dry stands indicate that tree growth may increasingly be limited by N and not by P with decreasing precipitation.



1992 ◽  
Vol 2 (3) ◽  
pp. 139 ◽  
Author(s):  
RA Hartford ◽  
WH Frandsen

Fire effects on aplant community, soil, and air are not apparent when judged only by surface fire intensity. The fire severity or fire impact can be described by the temperatures reached within the forest floor and the duration of heating experienced in the vegetation, forest floor, and underlying mineral soil. Temporal distributions of temperatures illustrate heat flow in duff and mineral soil in three instrumented plots: two with slash fuel over moist duff and one with litter fuel over dry duff. Fires in the two slash fuel plots produced substantial flame lengths but minimal heating in the underlying mineral soil. In contrast, smoldering combustion in the dry duff plot produced long duration heating with nearly complete duff consumption and lethal temperatures at the mineral soil surface. Moisture content of duff and soil were key variables for determining f i e impact on the forest floor.



2013 ◽  
Vol 22 (6) ◽  
pp. 780 ◽  
Author(s):  
Andrew T. Hudak ◽  
Roger D. Ottmar ◽  
Robert E. Vihnanek ◽  
Nolan W. Brewer ◽  
Alistair M. S. Smith ◽  
...  

White ash results from the complete combustion of surface fuels, making it a logically simple retrospective indicator of surface fuel consumption. However, the strength of this relationship has been neither tested nor adequately demonstrated with field measurements. We measured surface fuel loads and cover fractions of white ash and four other surface materials (green vegetation, brown non-photosynthetic vegetation, black char and mineral soil) immediately before and after eight prescribed fires in four disparate fuelbed types: boreal forest floor, mixed conifer woody slash, mixed conifer understorey and longleaf pine understorey. We hypothesised that increased white ash cover should correlate significantly to surface fuel consumption. To test this hypothesis, we correlated field measures of surface fuel consumption with field measures of surface cover change. Across all four fuelbed types, we found increased white ash cover to be the only measure of surface cover change that correlated significantly to surface fuel consumption, supporting our hypothesis. We conclude that white ash load calculated from immediate post-fire measurements of white ash cover, depth and density may provide an even more accurate proxy for surface fuel consumption, and furthermore a more physically based indicator of fire severity that could be incorporated into rapid response, retrospective wildfire assessments.



2017 ◽  
Vol 26 (4) ◽  
pp. 296 ◽  
Author(s):  
Randall K. Kolka ◽  
Brian R. Sturtevant ◽  
Jessica R. Miesel ◽  
Aditya Singh ◽  
Peter T. Wolter ◽  
...  

Forest fires cause large emissions of C (carbon), N (nitrogen) and Hg (mercury) to the atmosphere and thus have important implications for global warming (e.g. via CO2 and N2O emissions), anthropogenic fertilisation of natural ecosystems (e.g. via N deposition), and bioaccumulation of harmful metals in aquatic and terrestrial systems (e.g. via Hg deposition). Research indicates that fires are becoming more severe over much of North America, thus increasing element emissions during fire. However, there has been little research relating forest floor and mineral soil losses of C, N and Hg to on-the-ground indices of fire severity that enable scaling up those losses for larger-scale accounting of fire-level emissions. We investigated the relationships between forest floor and mineral soil elemental pools across a range of soil-level fire severities following the 2011 Pagami Creek wildfire in northern Minnesota, USA. We were able to statistically differentiate losses of forest floor C, N and Hg among a five-class soil-level fire severity classification system. Regression relationships using soil fire severity class were able to predict remaining forest floor C, N and Hg pools with 82–96% confidence. We correlated National Aeronautics and Space Administration Airborne Visible and Infrared Imaging Spectrometer-Classic imagery to ground-based plot-scale estimates of soil fire severity to upscale emissions of C, N and Hg to the fire level. We estimate that 468 000 Mg C, 11 000 Mg of N and over 122 g of Hg were emitted from the forest floor during the burning of the 28 310 ha upland area of the Pagami Creek fire.



1993 ◽  
Vol 41 (4) ◽  
pp. 247-265
Author(s):  
G. Arnold ◽  
A. Van Diest

In 1985-1988, a 25-yr-old Scots pine forest in Netherlands was limed and fertilized with P, K and Mg in a 24 factorial design and in an experiment with 5 liming levels, in order to alleviate potential nutrient deficiencies as a result of high N depositions (ca. 40 kg ha-1 yr-1). In this paper, effects of fertilization and liming on nutrients in forest floor and mineral soil are discussed as a basis for explanation of foliar nutrient concentrations and tree performance. Of all treatments, liming showed the widest array of effects, especially in forest floor: raised pH and lowered extractable Al in forest floor, and after 4 yr those in 0-50 cm mineral soil. These effects, except for that on forest floor pH, were stronger with increasing lime dosages. Liming showed transient effects on amounts of soil inorganic N (Ni). Until 1989, Ni in forest floor was lowered and that in mineral soil was raised by liming. This could be attributed to the formation of NO3, which is more mobile than NH4. Plots limed with 3 t lime/ha appeared to have higher Ni concentrations in the whole sampled profile than those limed with >3 t/ha or unlimed plots, the reason for which is unclear. Liming removed extractable K and Mg from forest floor probably by exchange against Ca. Residence time of added P and possibly Mg in forest floor was increased by liming, probably by solubility of added fertilizers. Added K was poorly retained in forest floor and probably quickly leached to soil layers deeper than 50 cm.



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