Nutrient cycling in relation to decomposition and organic-matter quality in taiga ecosystems

1983 ◽  
Vol 13 (5) ◽  
pp. 795-817 ◽  
Author(s):  
P. W. Flanagan ◽  
K. Van Cleve
Keyword(s):  
Organic Matter ◽  
Nitrogen Content ◽  
Forest Floor ◽  
Fungal Biomass ◽  
Microbial Respiration ◽  
Black Spruce ◽  
Litter Fall ◽  
Substrate Quality ◽  
Respiration Rates ◽  
Forest Floors

A variety of evergreen and deciduous forests in the taiga of interior Alaska were studied over a 5-year period to examine how the chemical quality of forest-floor organic matter affected its rate of decomposition and mineral cycling within and outside the tree vegetation. Litterbag and respiration studies were used to monitor decomposition. Natural forest-floor substrates and others altered by addition of N, P, and K fertilizer and glucose as a carbon source were studied in the laboratory and field for rates of weight loss and O2 consumption. Forest floors differing in C/N ratios, including those deficient in N, were used to measure substrate quality influences on seedling growth, nutrient content, and tannin content. Microbial (bacteria and fungi) biomass was measured across a range of forest types along with pH, base saturation total pool sizes of N and P, and annual mineralization of organic matter per square metre. Under identical moisture and temperature conditions average respiration rates in evergreen forest-floor L, F, and H substrates were 1.8, 2.8, and 2.0 times less than in the corresponding deciduous forest horizons, respectively. Birch L and F horizons had respiration rates 11.5 times higher than the corresponding black spruce layers. Weight losses in birch L, F, and H horizons were 6, 3, and 2 times higher, respectively, than in the corresponding black spruce substrates. Substrates had a quality-dependent decay rate which did not change when they were relocated within or between sites indicating that measured field climatic differences were not as influential on decay rates as substrate quality components. Fungal biomass was significantly correlated with the quantity of organic matter in all sites (n = 15, r = 0.62) but correlations were better for deciduous (n = 9, r = 0.89), and evergreen (n = 6, r = 0.82) forests separately. Strong correlations exist also between grams of organic matter decayed per square metre per year and fungal biomass (n = 13, r = 0.86), and fungal biomass and grams of N and P mineralized per square metre per year (n = 14, r = 0.95) and (n = 11, r = 0.94, respectively). Seedlings on mineral-deficient substrates produced more tannins than the controls, and seedlings on substrates with widening C/N ratios had successively less tissue with lower N content, and proportionally more roots. Nitrogen content of litter fall in increasingly nitrogen-poor forest floors was correspondingly lower. Nitrogen content of litter fall on N rich forest floors and N fertilized forest floors was proportionately higher. Nitrogen withdrawal in leaves at senescence was inversely correlated with grams N mineralized per square metre per year in forest floors. Fertilization did not influence microbial processes in the field, though lab studies indicated a negative influence of NH4, P, and K on microbial respiration. Glucose added in the laboratory and field markedly increased forest-floor microbial respiration. In vitro glucose-induced increases in respiration were not influenced by addition of ammonium nitrate and were significantly depressed by addition of P and K. In the field, fertilization had no effect on either glucose-induced respiration or microbial biomass.

Organic matter and nitrogen content of the forest floor in even-aged northern hardwoods

1984 ◽  
Vol 14 (6) ◽  
pp. 763-767 ◽  
Author(s):  
C. Anthony Federer
Keyword(s):  
Organic Matter ◽  
Nitrogen Content ◽  
Bulk Density ◽  
Forest Floor ◽  
Mineral Soil ◽  
Organic Content ◽  
Stand Age ◽  
Clear Cutting ◽  
Mature Forest ◽  
Forest Floors

Organic content of the forest floor decreases for several years after clear-cutting, and then slowly recovers. Thickness, bulk density, organic matter, and nitrogen content of forest floors were measured for 13 northern hardwood stands in the White Mountains of New Hampshire. Stands ranged from 1 to about 100 years in age. Forest-floor thickness varied significantly with stand age, but bulk density, organic fraction, and nitrogen fraction were independent of age. Total organic content of the forest floor agreed very well with data from Covington's (W. W. Covington 1981. Ecology, 62: 41–48) study of the same area. Both studies indicated that mature forest floors have about 80 Mg organic matter•ha−1 and 1.9 Mg nitrogen•ha−1. Within 10 or 15 years after cutting, the organic matter content of the floor decreases to 50 Mg•ha−1, and its nitrogen content to 1.1 Mg•ha−1. The question whether the decrease is rapid and the minimum broad and flat, or if the decrease is gradual and the minimum sharp, cannot be answered. The subsequent increase to levels reached in mature forest requires about 50 years. Some of the initial decrease in organic matter and nitrogen content of the forest floor may be caused by organic decomposition and nitrogen leaching, but mechanical and chemical mixing of floor into mineral soil, during and after the harvest operation, may also be important. The difference is vital with respect to maintenance of long-term productivity.

scholarly journals Microbial Substrate Utilization and Vegetation Shifts in Boreal Forest Floors of Western Canada

2021 ◽  
Vol 4 ◽  
Author(s):  
Emily Lloret ◽  
Sylvie Quideau
Keyword(s):  
Boreal Forest ◽  
Microbial Communities ◽  
Forest Floor ◽  
Microbial Respiration ◽  
Substrate Utilization ◽  
Utilization Efficiency ◽  
Western Canada ◽  
Spruce Forest ◽  
Vegetation Shifts ◽  
Forest Floors

Boreal forest soils are highly susceptible to global warming, and in the next few decades, are expected to face large increases in temperature and transformative vegetation shifts. The entire boreal biome will migrate northward, and within the main boreal forest of Western Canada, deciduous trees will replace conifers. The main objective of our research was to assess how these vegetation shifts will affect functioning of soil microbial communities and ultimately the overall persistence of boreal soil carbon. In this study, aspen and spruce forest floors from the boreal mixedwood forest of Alberta were incubated in the laboratory for 67 days without (control) and with the addition of three distinct 13C labeled substrates (glucose, aspen leaves, and aspen roots). Our first objective was to compare aspen and spruce substrate utilization efficiency (SUE) in the case of a labile C source (13C-glucose). For our second objective, addition of aspen litter to spruce forest floor mimicked future vegetation shifts, and we tested how this would alter substrate use efficiency in the spruce forest floor compared to the aspen. Tracking of carbon utilization by microbial communities was accomplished using 13C-PLFA analysis, and 13C-CO2 measurements allowed quantification of the relative contribution of each added substrate to microbial respiration. Following glucose addition, the aspen community showed a greater 13C-PLFA enrichment than the spruce throughout the 67-day incubation. The spruce community respired a greater amount of 13C glucose, and it also had a much lower glucose utilization efficiency compared to the aspen. Following addition of aspen litter, in particular aspen leaves, the aspen community originally showed greater total 13C-PLFA enrichment, although gram positive phospholipid fatty acids (PLFAs) were significantly more enriched in the spruce community. While the spruce community respired a greater amount of the added 13C-leaves, both forest floor types showed comparable substrate utilization efficiencies by Day 67. These results indicate that a shift from spruce to aspen may lead to a greater loss of the aspen litter through microbial respiration, but that incorporation into microbial biomass and eventually into the more persistent soil carbon pool may not be affected.

Bioassay of forest floor nitrogen supply for plant growth

1986 ◽  
Vol 16 (6) ◽  
pp. 1320-1326 ◽  
Author(s):  
K. Van Cleve ◽  
O. W. Heal ◽  
D. Roberts
Keyword(s):  
Forest Floor ◽  
Black Spruce ◽  
Nitrogen Concentration ◽  
N Uptake ◽  
Mineral Soil ◽  
Forest Types ◽  
N Supply ◽  
Paper Birch ◽  
Forest Floors ◽  
P Supply

Using a bioassay approach, this paper considers the nitrogen-supplying power of forest floors from examples of the major forest types in interior Alaska. Yield and net N uptake by paper birch seedlings grown in standardized mixtures of quartz sand and forest floor organic matter, and separate incubation estimates of N mineralization and nitrification for the forest floors, were employed to evaluate potential N supply. Black spruce and floodplain white spruce forest floors supplied only one-fifth the amount of N taken up by seedlings growing in other forest floors. Incubation estimates showed these forest floors yielded 4 and 15 times less extractable N, respectively, than the more fertile birch forest floors. In comparison with earlier estimates of P supply from these same forest floors, the upland types showed greater deficiency of N whereas floodplain types showed greater deficiency of P in control of seedling yield. The latter condition is attributed to the highly calcareous nature of the floodplain mineral soil, the consequent potential for P fixation, and hence greater potential deficiency of the element compared with N in mineralizing forest floors. Nitrogen concentration of the forest floors was the best predictor of bioassay response.

Bioassay of forest floor phosphorus supply for plant growth

1985 ◽  
Vol 15 (1) ◽  
pp. 156-162 ◽  
Author(s):  
K. Van Cleve ◽  
F. Harrison
Keyword(s):  
Forest Floor ◽  
Black Spruce ◽  
Forest Types ◽  
P Deficiency ◽  
Interior Alaska ◽  
Rooting Medium ◽  
Forest Floors ◽  
Work Supports ◽  
Plant Bioassays

This paper considers the extent to which phosphorus (P) supply for plant use is controlled by the chemical quality of forest floor organic matter, independent of climate. Using plant bioassays, forest floor materials from representative examples of each of the major forest types in interior Alaska were examined for nutrient supplying power. The work supports conclusions reached in earlier studies which indicated that black spruce forest floors were highly nutrient limited compared with those of other interior Alaska forest types. In addition, floodplain white spruce forests may experience marked P deficiency because of dilution of the element by periodic siltation. Potential phosphorus supply for seedling growth was best described by P concentration of the rooting medium. The supply also was related to the concentrations of lignin and tannin which control forest floor decomposition and recycling of P within the microbial population.

Addition of organic matter and elements to the forest floor of an old-growth Acersaccharum forest in the annual litter fall

1991 ◽  
Vol 21 (4) ◽  
pp. 462-468 ◽  
Author(s):  
I. K. Morrison
Keyword(s):  
Organic Matter ◽  
Forest Floor ◽  
Base Cations ◽  
Dry Weight ◽  
Turnover Time ◽  
Residence Times ◽  
Litter Fall ◽  
Old Growth ◽  
Northern Ontario ◽  
Element Transfer

Litter fall and its content of N, P, K, Ca, Mg, S, Fe, Mn, Zn, and Cu were measured monthly over a 5-year period in an old-growth Acersaccharum Marsh, stand on a till site in central northern Ontario. Determined were the following: the amount, and the temporal and spatial distributions, of organic matter and elements deposited annually in the different litter fractions; the proportion of elements conserved within the tree phytomass through retranslocation versus that shed in the annual litter fall; and the residence time of litter-transported elements in the forest floor. Element transfer through the annual litter fall was also compared with that by other vectors of transport to the forest floor. Over the study period, total litter fall averaged 3730 kg•ha−1•year−1 (dry weight), with 78% consisting of leaves, 8% of flowers and fruits, and the remaining 14% mainly of twigs, branches, and bark slough. Annual element depositions (kg•ha−1) averaged as follows: N, 40.6; P, 1.8; K, 9.1; Ca, 37.6; Mg, 3.9; S, 3.0; Fe, 0.57; Mn, 2.67; Zn, 0.28; and Cu, 0.03. Turnover time of the forest floor was calculated as 7.4 years. Residence times (years) of elements in the forest floor were as follows: N, 18.3; P, 18.3; K, 1.5; Ca, 6.1; Mg, 6.8; S, 5.1; Fe, 257.2; Mn, 4.8; Zn, 18.1; and Cu, 5.8. Although the turnover time of forest-floor organic matter did not differ appreciably from values reported for A. saccharum forests elsewhere, residence times for elements suggested somewhat slower cycling, probably as a result of reduced uptake related to the advanced age of the stand. Potassium, followed by S, P, and N, were all conserved to a high degree by A. saccharum trees through retranslocation to the tree's perennial parts prior to leaf fall; Cu, Mn, and Mg were conserved to a lesser degree; Zn, Ca, and Fe were conserved very little. In comparing the leaching loss of elements from foliage with quantities conserved through retranslocation and quantities shed in the annual litter fall, the relative orders of magnitude do not give cause for concern that A. saccharum trees risk appreciable leaching losses of base cations, including K, from foliage as a result of acidified precipitation, at least at levels experienced in central northern Ontario during the early 1980s.

Effects of bigleaf maple on soils in Douglas-fir forests

1990 ◽  
Vol 20 (3) ◽  
pp. 259-266 ◽  
Author(s):  
Jeremy S. Fried ◽  
James R. Boyle ◽  
John C. Tappeiner II ◽  
Kermit Cromack Jr.
Keyword(s):  
Forest Floor ◽  
Mineral Soil ◽  
Nutrient Content ◽  
Douglas Fir ◽  
Organic Carbon Content ◽  
Coast Range ◽  
Litter Fall ◽  
Turnover Rates ◽  
Calcium Magnesium ◽  
Forest Floors

Soil chemical and physical properties, forest floor weights, nutrient content and turnover rates, and litter fall weights and nutrient content under bigleaf maple (Acermacrophyllum Pursh) and Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco var. menziesii) were compared on five sites on the eastern margin of the Oregon Coast Range. Litter fall weight and nutrient content were significantly greater under maple on every site for every macronutrient and for most micronutrients. Forest floor biomass and nutrient content were extremely variable, much more so than litter fall, and there were no consistent differences between the two species. However, turnover rates for forest floor biomass and nutrients were significantly faster under maple for every nutrient at every site. Bulk density of mineral soil was also highly variable with significant differences at only two sites. Soil under maple was consistently higher in nitrogen, and less consistently, in potassium. There were no consistent trends in amounts of calcium, magnesium, or phosphorus. Soil organic carbon content under maple was significantly greater than under Douglas-fir on four of five sites. These differences may result from the more rapid turnover of forest floors under maple trees.

The response of root and microbial respiration to the experimental warming of a boreal black spruce forest

2014 ◽  
Vol 44 (8) ◽  
pp. 986-993 ◽  
Author(s):  
Jason G. Vogel ◽  
Dustin Bronson ◽  
Stith T. Gower ◽  
Edward A.G. Schuur
Keyword(s):  
Picea Mariana ◽  
Microbial Respiration ◽  
Black Spruce ◽  
Control Treatment ◽  
Prolonged Release ◽  
Spruce Forest ◽  
Experimental Warming ◽  
Soil Microbial ◽  
Respiration Rates ◽  
And Control

We investigated the effects of a 5 °C soil + air experimental heating on root and microbial respiration in a boreal black spruce (Picea mariana (Mill.) B.S.P.) forest in northern Manitoba, Canada, that was warmed between 2004 and 2007. In 2007, the 14C/12C signatures of soil CO2 efflux and root and soil microbial respiration were used in a two-pool mixing model to estimate their proportional contributions to soil CO2 efflux and to examine how each changed in response to the warming treatments. In laboratory incubations, we examined whether warming had altered microbial respiration rates or microbial temperature sensitivity. The 14C/12C signature of soil CO2 efflux and microbial respiration in the heating treatments were both significantly (p < 0.05) enriched relative to the control treatment, suggesting that C deposited nearer the atmospheric bomb peak in 1963 contributed more to microbial respiration in heated than control treatments. Soil CO2 efflux was significantly greater in the heated than control treatments, suggesting the acclimation to temperature of either root or microbial respiration was not occurring in 2007. Microbial respiration in laboratory incubations was similar in heated and control soils. This study shows that microbial respiration rates still responded to temperature even after 4 years of warming, highlighting that ecosystem warming can cause a prolonged release of soil organic matter from these soils.

A low-cost unit for measuring carbon dioxide evolution from organic matter under field conditions

1976 ◽  
Vol 6 (1) ◽  
pp. 33-39
Author(s):  
Harald Piene ◽  
Keith Van Cleve
Keyword(s):  
Organic Matter ◽  
Forest Floor ◽  
Low Cost ◽  
Oxygen Depletion ◽  
Field Conditions ◽  
Carbon Dioxide Evolution ◽  
Seasonal Trends ◽  
Respiration Rates ◽  
Laboratory Calibration ◽  
Incubation Periods

A chamber was constructed and tested to determine respiration rates from forest floor L-layer material under field conditions. Seasonal trends in CO2 evolution closely followed seasonal trends in moisture content in the organic matter. Maximum respiration rates were encountered over a moisture range from about 65 to 100%.During laboratory calibration tests, no depression of respiration rates as a result of oxygen depletion in the chambers was detected except at 32 °C, where depression occurred after about 6 h incubation. Regardless of temperature, the KOH in the chambers absorbed nearly all (99.6 to 100%) of CO2 that evolved during incubation periods of up to 48 h duration.

Decomposition, litter fall, and forest floor nutrient dynamics in relation to fire in eastern Ontario jack pine ecosystems

1987 ◽  
Vol 17 (12) ◽  
pp. 1496-1506 ◽  
Author(s):  
M. G. Weber
Keyword(s):  
Organic Matter ◽  
Old Age ◽  
Forest Floor ◽  
Nutrient Dynamics ◽  
Jack Pine ◽  
Litter Fall ◽  
Turnover Rates ◽  
Equilibrium Conditions ◽  
Age Class ◽  
Eastern Ontario

Decomposition, litter fall, and nutrient and organic matter turnover rates were determined in five eastern Ontario jack pine (Pinusbanksiana Lamb.) stands having various burning histories, including wildfire. The stands included a 65-year-old age-class (stand No. 1), two stands within this age-class that were treated with nonlethal understorey fires in 1962 and 1963 (stand Nos. 2 and 3, respectively), a 21-year-old age-class (stand No. 4), and an 8-year-old age-class (stand No. 5) created by experimental burning plots within the 21-year-old age-class. Overstorey and understorey litter decomposition was assessed separately using the litterbag (1-mm mesh size) technique over a 2-year period. Overstorey litter weight loss did not vary among stands and understorey litter lost significantly more weight (P < 0.05) in the older age-classes (stands 1,2, and 3) compared with the younger stands (stands 4 and 5). Litterbag nutrient dynamics between overstorey and understorey were significantly different (P < 0.05) for P, K, and Cain all stands. Magnesium and N dynamics were the same in both litter types on all treatments, as was Fe, except in the 65-year-old stand where significantly more Fe was accumulated in understorey litter (P < 0.04) at the end of the litterbag exposure period. Three-year averages of annual litter fall ranged from 119 kg•ha−1•year−1 in the 8-year-old age-class to 4182 kg•ha−1•year−1 in the older stands. Nutrient inputs through litter fall reflect the developmental stage occupied by the younger stands along a continuum leading to equilibrium conditions of the 65-year-old age-class. Forest floor nutrient and organic matter residence times (or annual fractional turnover) were longest (least amount cycled) in the 8-year-old stand (57.6 years for organic matter), indicating harsh environmental controls over nutrient dynamics. Recovery for the 21-year-old age-class to turnover rates approaching equilibrium conditions (10-year residence time for organic matter) was rapid, demonstrating ecosystem stability in its interaction with fire. Detrimental effects on ecosystem processes can be expected if a stand-replacing fire recurs during early stages of jack pine ecosystem development.

The effects of experimental fires on black spruce forest floors in interior Alaska

1983 ◽  
Vol 13 (5) ◽  
pp. 879-893 ◽  
Author(s):  
C. T. Dyrness ◽  
Rodney A. Norum
Keyword(s):  
Forest Floor ◽  
Black Spruce ◽  
Mineral Soil ◽  
Available P ◽  
Small Scale ◽  
Total N ◽  
Burned Areas ◽  
Forest Floors ◽  
Surface Mineral ◽  
Total P

Seven units (about 2 ha each) of black spruce – feather moss forest were experimentally burned over a range of fuel moisture conditions during the summer of 1978. Surface woody fuels were sparse and the principal carrier fuel was the forest floor (largely mosses and their decomposition products). Forest floors after burning comprised a small-scale mosaic of unburned, scorched, lightly burned, moderately burned, and heavily burned (organic materials entirely consumed) conditions. Percentage of the unit area in the moderately and heavily burned condition ranged from 11.2 to 77.2% and percent decrease in forest-floor thickness varied from 27.4 to 63.1% in the seven units. Forest-floor consumption was most closely correlated with the moisture content of lower moss (01 horizon) and lower duff layers (022 horizon) at the time of burning. For the first 3 years after fire, biomass production was greater on heavily burned than on lightly burned sites (58 vs. 37 g/m2 on an annual basis). Heavily burned sites were completely dominated by the invading species Epilobiumangustifolium L., Ceratodonpurpureus (Hedw.) Brid., and Marchantiapolymorpha L., whereas lightly burned plots were occupied by sprouting species such as Calamagrostiscanadensis (Michx.) Beauv., Vacciniumuliginosum L., and Ledumgroenlandicum Oeder. Soil pH and amounts of total P and available P in the forest floor increased significantly as a result of burning; and in all cases, increases reached a maximum in moderately and heavily burned areas. Total N in the forest floor increased significantly in moderately burned, but decreased slightly in heavily burned areas. Total N and total P showed smaller increases in the surface mineral soil as a result of burning. Supplies of available P in the mineral soil increased almost 4-fold in moderately burned and over 16-fold in heavily burned areas.

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