Decomposition of [14C]Lignocelluloses of Spartina alterniflora and a Comparison with Field Experiments

Decomposition of lignocelluloses from Spartina alterniflora in salt-marsh sediments was measured by using ¹⁴C-labeled compounds. Rates of decomposition were fastest in the first 4 days of incubation and declined later. Lignins labeled in side chains were mineralized slightly faster than uniformly labeled lignins; 12% of the [side chain-¹⁴C]lignin-labeled lignocellulose was mineralized after 816 h of incubation, whereas only 8% of the [U-¹⁴C]lignin-labeled lignocelluloses were degraded during this period. The carbohydrate moiety within the lignocellulose complex was degraded about four times faster than the lignin moiety; after 816 h of incubation, 29 to 37% of the carbohydrate moiety had been mineralized. Changes in concentration of lignin and cellulose in litter of S. alterniflora were followed over 2 years of decay. Cellulose disappeared from litter more rapidly than lignin; 50% of the initial content of cellulose was lost after 130 days, whereas lignin required 330 to 380 days for 50% loss. The slow loss of lignin compared with other litter components resulted in a progressive enrichment of litter in lignin content. The rates of mineralization of [¹⁴C]lignocelluloses in marsh sediments were similar to the rates of lignocellulose decomposition in litter on the marsh.     

Preparation, characterization, and microbial degradation of specifically radiolabeled [C]lignocelluloses from marine and freshwater macrophytes

Specifically radiolabeled [C-lignin]lignocelluloses were prepared from the aquatic macrophytes Spartina alterniflora, Juncus roemerianus, Rhizophora mangle, and Carex walteriana by using [C]phenylalanine, [C]tyrosine, and [C]cinnamic acid as precursors. Specifically radiolabeled [C-polysaccharide]lignocelluloses were prepared by using [C]glucose as precursor. The rates of microbial degradation varied among [C-lignin]lignocelluloses labeled with different lignin precursors within the same plant species. To determine the causes of these differential rates, [C-lignin]lignocelluloses were thoroughly characterized for the distribution of radioactivity in nonlignin contaminants and within the lignin macromolecule. In herbaceous plants, significant amounts (8 to 24%) of radioactivity from [C]phenylalanine and [C]tyrosine were found associated with protein, although very little (3%) radioactivity from [C]cinnamic acid was associated with protein. Microbial degradation of radiolabeled protein resulted in overestimation of lignin degradation rates in lignocelluloses derived from herbaceous aquatic plants. Other differences in degradation rates among [C-lignin]lignocelluloses from the same plant species were attributable to differences in the amount of label being associated with ester-linked subunits of peripheral lignin. After acid hydrolysis of [C-polysaccharide]lignocelluloses, radioactivity was detected in several sugars, although most of the radioactivity was distributed between glucose and xylose. After 576 h of incubation with salt marsh sediments, 38% of the polysaccharide component and between 6 and 16% of the lignin component (depending on the precursor) of J. roemerianus lignocellulose was mineralized to CO(2); during the same incubation period, 30% of the polysaccharide component and between 12 and 18% of the lignin component of S. alterniflora lignocellulose was mineralized.     

Contribution to lignocellulose degradation and DOC formation from a salt marsh macrophyte by the ascomycete Phaeosphaeria spartinicola

Abstract Specifically radiolabeled [¹⁴C-lignin] lignocellulose and uniformly [U-¹⁴C] lignocellulose from the salt marsh grass Spartina alterniflora were incubated with the ascomycete Phaesphaeria s spartinicola . This fungus is the predominant one found on decaying standing dead S. alterniflora leaves in the salt marsh ecosystem. After 45 days of incubation at 20°C, 3.3% of the lignin moiety was mineralized to ¹⁴CO₂ and 2.7% solubilized to DO¹⁴C. Mineralization of the polysaccharides was seven times faster than that of the lignin. About 22% of the radioactivity was evolved as ¹⁴CO₂ but merely 4% was solubilized to DO¹⁴C within the incubation time. Experiments monitoring the ergosterol content of the mycelium incubated with S. alterniflora plant material were done to elucidate the carbon conversion efficiency of the fungus as well as the influence of the cinnamyl phenols p -coumaric and ferulic acid on lignocellulose degration. After 21 days of incubation, P. spartinicola showed a growth yield of 0.45 and 0.38 with and without the additional cinnamyl phenols, respectively. Grown on unextracted S. alterniflora the fungus caused a loss of organic plant material of about 50% with a corresponding growth yield of 0.38 during the incubation period. Investigation of cupric oxide oxidation products of sound and degraded lignocellulose revealed a preferential utilization of the syrinyl and cinnamly phenols compared with vanilly phenols.     

Mineralization of Detrital Lignocelluloses by Salt Marsh Sediment Microflora

Specifically radiolabeled ¹⁴C-(cellulose)-lignocellulose and ¹⁴C-(lignin)-lignocellulose were isolated from labeled cuttings of Spartina alterniflora (cordgrass) and Pinus elliottii (slash pine). These were used to estimate the rates of mineralization to CO₂ of lignocelluloses of estuarine and terrestrial origin in salt marsh estuarine sediments. The lignin moiety of pine lignocellulose was mineralized 10 to 14 times more slowly than that of Spartina lignocellulose, depending on the source of inoculum. Average values for percent mineralization after 835 h of incubation were 1.4 and 13.9%, respectively. For Spartina lignocellulose, mineralization of the cellulose moiety was three times faster than that of the lignin moiety. Average values for percent mineralization after 720 h of incubation were 32.1 and 10.6%, respectively. Lignocellulose and lignin contents of live pine and Spartina plants were analyzed and found to be 60.7 and 20.9%, respectively, for pine and 75.6 and 15.1%, respectively, for Spartina.     

Anaerobic Biodegradation of the Lignin and Polysaccharide Components of Lignocellulose and Synthetic Lignin by Sediment Microflora

Specifically radiolabeled [¹⁴C-lignin]lignocelluloses and [¹⁴C-polysaccharide]lignocelluloses were prepared from a variety of marine and freshwater wetland plants including a grass, a sedge, a rush, and a hardwood. These [¹⁴C]lignocellulose preparations and synthetic [¹⁴C]lignin were incubated anaerobically with anoxic sediments collected from a salt marsh, a freshwater marsh, and a mangrove swamp. During long-term incubations lasting up to 300 days, the lignin and polysaccharide components of the lignocelluloses were slowly degraded anaerobically to ¹⁴CO₂ and ¹⁴CH₄. Lignocelluloses derived from herbaceous plants were degraded more rapidly than lignocellulose derived from the hardwood. After 294 days, 16.9% of the lignin component and 30.0% of the polysaccharide component of lignocellulose derived from the grass used (Spartina alterniflora) were degraded to gaseous end products. In contrast, after 246 days, only 1.5% of the lignin component and 4.1% of the polysaccharide component of lignocellulose derived from the hardwood used (Rhizophora mangle) were degraded to gaseous end products. Synthetic [¹⁴C]lignin was degraded anaerobically faster than the lignin component of the hardwood lignocellulose; after 276 days, 3.7% of the synthetic lignin was degraded to gaseous end products. Contrary to previous reports, these results demonstrate that lignin and lignified plant tissues are biodegradable in the absence of oxygen. Although lignocelluloses are recalcitrant to anaerobic biodegradation, rates of degradation measured in aquatic sediments are significant and have important implications for the biospheric cycling of carbon from these abundant biopolymers.     

Isolation of a Bacterium Capable of Degrading Peanut Hull Lignin

Thirty-seven bacterial strains capable of degrading peanut hull lignin were isolated by using four types of lignin preparations and hot-water-extracted peanut hulls. One of the isolates, tentatively identified as Arthrobacter sp., was capable of utilizing all four lignin preparations as well as extracted peanut hulls as a sole source of carbon. The bacterium was also capable of degrading specifically labeled [¹⁴C]lignin-labeled lignocellulose and [¹⁴C]cellulose-labeled lignocellulose from the cordgrass Spartina alterniflora and could also degrade [¹⁴C]Kraft lignin from slash pine. After 10 days of incubation with [¹⁴C]cellulose-labeled lignocellulose or [¹⁴C]lignin-labeled lignocellulose from S. alterniflora, the bacterium mineralized 6.5% of the polysaccharide component and 2.9% of the lignin component.     

Preparation, Characterization, and Microbial Degradation of Specifically Radiolabeled [14C]Lignocelluloses from Marine and Freshwater Macrophytes

Specifically radiolabeled [¹⁴C-lignin]lignocelluloses were prepared from the aquatic macrophytes Spartina alterniflora, Juncus roemerianus, Rhizophora mangle, and Carex walteriana by using [¹⁴C]phenylalanine, [¹⁴C]tyrosine, and [¹⁴C]cinnamic acid as precursors. Specifically radiolabeled [¹⁴C-polysaccharide]lignocelluloses were prepared by using [¹⁴C]glucose as precursor. The rates of microbial degradation varied among [¹⁴C-lignin]lignocelluloses labeled with different lignin precursors within the same plant species. To determine the causes of these differential rates, [¹⁴C-lignin]lignocelluloses were thoroughly characterized for the distribution of radioactivity in nonlignin contaminants and within the lignin macromolecule. In herbaceous plants, significant amounts (8 to 24%) of radioactivity from [¹⁴C]phenylalanine and [¹⁴C]tyrosine were found associated with protein, although very little (3%) radioactivity from [¹⁴C]cinnamic acid was associated with protein. Microbial degradation of radiolabeled protein resulted in overestimation of lignin degradation rates in lignocelluloses derived from herbaceous aquatic plants. Other differences in degradation rates among [¹⁴C-lignin]lignocelluloses from the same plant species were attributable to differences in the amount of label being associated with ester-linked subunits of peripheral lignin. After acid hydrolysis of [¹⁴C-polysaccharide]lignocelluloses, radioactivity was detected in several sugars, although most of the radioactivity was distributed between glucose and xylose. After 576 h of incubation with salt marsh sediments, 38% of the polysaccharide component and between 6 and 16% of the lignin component (depending on the precursor) of J. roemerianus lignocellulose was mineralized to ¹⁴CO₂; during the same incubation period, 30% of the polysaccharide component and between 12 and 18% of the lignin component of S. alterniflora lignocellulose was mineralized.     

Thermophilic anaerobic biodegradation of [C]lignin, [C]cellulose, and [C]lignocellulose preparations

Thermophilic (55 degrees C) anaerobic enrichment cultures were incubated with [C-lignin]lignocellulose, [C-polysaccharide]lignocellulose, and kraft [C]lignin prepared from slash pine, Pinus elliottii, and C-labeled preparations of synthetic lignin and purified cellulose. Significant but low percentages (2 to 4%) of synthetic and natural pine lignin were recovered as labeled methane and carbon dioxide during 60-day incubations, whereas much greater percentages (13 to 23%) of kraft lignin were recovered as gaseous end products. Percentages of label recovered from lignin-labeled substrates as dissolved degradation products were approximately equal to percentages recovered as gaseous end products. High-pressure liquid chromatographic analyses of CuO oxidation products of sound and degraded pine lignin indicated that no substantial chemical modifications of the remaining lignin polymer, such as demethoxylation and dearomatization, occurred during biodegradation. The polysaccharide components of pine lignocellulose and purified cellulose were relatively rapidly mineralized to methane and carbon dioxide; 31 to 37% of the pine polysaccharides and 56 to 63% of the purified cellulose were recovered as labeled gaseous end products. An additional 10 to 20% of the polysaccharide substrates was recovered as dissolved degradation products. Overall, these results indicate that elevated temperatures can greatly enhance rates of anaerobic degradation of lignin and lignified substrates to methane and low-molecular-weight aromatic compounds.     

Thermophilic Anaerobic Biodegradation of [14C]Lignin, [14C]Cellulose, and [14C]Lignocellulose Preparations

Thermophilic (55°C) anaerobic enrichment cultures were incubated with [¹⁴C-lignin]lignocellulose, [¹⁴C-polysaccharide]lignocellulose, and kraft [¹⁴C]lignin prepared from slash pine, Pinus elliottii, and ¹⁴C-labeled preparations of synthetic lignin and purified cellulose. Significant but low percentages (2 to 4%) of synthetic and natural pine lignin were recovered as labeled methane and carbon dioxide during 60-day incubations, whereas much greater percentages (13 to 23%) of kraft lignin were recovered as gaseous end products. Percentages of label recovered from lignin-labeled substrates as dissolved degradation products were approximately equal to percentages recovered as gaseous end products. High-pressure liquid chromatographic analyses of CuO oxidation products of sound and degraded pine lignin indicated that no substantial chemical modifications of the remaining lignin polymer, such as demethoxylation and dearomatization, occurred during biodegradation. The polysaccharide components of pine lignocellulose and purified cellulose were relatively rapidly mineralized to methane and carbon dioxide; 31 to 37% of the pine polysaccharides and 56 to 63% of the purified cellulose were recovered as labeled gaseous end products. An additional 10 to 20% of the polysaccharide substrates was recovered as dissolved degradation products. Overall, these results indicate that elevated temperatures can greatly enhance rates of anaerobic degradation of lignin and lignified substrates to methane and low-molecular-weight aromatic compounds.     

Relative Contributions of Bacteria and Fungi to Rates of Degradation of Lignocellulosic Detritus in Salt-Marsh Sediments

Specifically radiolabeled [¹⁴C-lignin]lignocellulose and [¹⁴C-polysaccharide]lignocellulose from the salt-marsh cordgrass Spartina alterniflora were incubated with an intact salt-marsh sediment microbial assemblage, with a mixed (size-fractionated) bacterial assemblage, and with each of three marine fungi, Buergenerula spartinae, Phaeosphaeria typharum, and Leptosphaeria obiones, isolated from decaying S. alterniflora. The bacterial assemblage alone mineralized the lignin and polysaccharide components of S. alterniflora lignocellulose at approximately the same rate as did intact salt-marsh sediment inocula. The polysaccharide component was mineralized twice as fast as the lignin component; after 23 days of incubation, ca. 10% of the lignin component and 20% of the polysaccharide component of S. alterniflora lignocellulose were mineralized. Relative to the total sediment and bacterial inocula, the three species of fungi mediated only very slow mineralization of the lignin and polysaccharide components of S. alterniflora lignocellulose. Experiments with uniformly ¹⁴C-labeled S. alterniflora material indicated that the three fungi and the bacterial assemblage were capable of degrading the non-lignocellulosic fraction of S. alterniflora material, but only the bacterial assemblage significantly degraded the lignocellulosic fraction. Our results suggest that bacteria are the predominant degraders of lignocellulosic detritus in salt-marsh sediments.     

Microbial degradation of lignocellulose: the lignin component

A new procedure was developed for the study of lignin biodegradation by pure or mixed cultures of microorganisms. Natural lignocelluloses were prepared containing C in primarily their lignin components by feeding plants l-[U-C]phenylalanine through their cut stems. Lignin degradation was observed in numerous soils by monitoring evolution of CO(2) from [C]lignin-labeled oak (Quercus albus), maple (Acer rubrum), and cattail (Typha latifola). An organism (Thermonospora fusca ATCC 27730) that is known to degrade cellulose but not lignin was shown to grow on lignocellulose in the presence of [C]lignocelluloses without evolution of CO(2). A known lignin degrader (a white-rot fungus, Polyporus versicolor) was shown to readily evolve CO(2) from damp C-labeled cattail and C-labeled maple.     

Preparation of specifically labeled C-(lignin)- and C-(cellulose)-lignocelluloses and their decomposition by the microflora of soil

Microbial decomposition of lignocellulose in soil was studied using radioisotope techniques. Natural lignocelluloses containing C in either their lignin or cellulose (glucan) components were prepared by feeding plants l-[U-C]phenylalanine or d-[U-C]glucose, respectively, through their cut stems. Detailed chemical and chromatographic characterization of labeled lignocelluloses from three hardwood and three softwood species showed that those labeled by the [C]glucose incorporation method contained specifically labeled cellulosic components, whereas those labeled by the [C]phenylalanine incorporation method contained specifically labeled lignin components. Microbial degradation of these differentially labeled lignocelluloses was followed by monitoring CO(2) evolution from selected soil samples incubated with known amounts of radiolabeled lignocelluloses. The lignin components of the six woods were shown to be decomposed in soil 4 to 10 times more slowly than their cellulosic components. These rates of mineralization were comparable to the generalized patterns previously reported in the literature. The present technique, however, was thought to be simpler, more sensitive, and less prone to interference than methods previously available.     

Effects of Petroleum Hydrocarbons on Plant Litter Microbiota in an Arctic Lake

The effects of petroleum hydrocarbons on the microbial community associated with decomposing Carex leaf litter colonized in Toolik Lake, Alaska, were examined. Microbial metabolic activity, measured as the rate of acetate incorporation into lipid, did not vary significantly from controls over a 12-h period after exposure of colonized Carex litter to 3.0 ml of Prudhoe Bay crude oil, diesel fuel, or toluene per liter. ATP levels of the microbiota became elevated within 2 h after the exposure of the litter to diesel fuel or toluene, but returned to control levels within 4 to 8 h. ATP levels of samples exposed to Prudhoe Bay crude oil did not vary from control levels. Mineralization of specifically labeled ¹⁴C-[lignin]-lignocellulose and ¹⁴C-[cellulose]-lignocellulose by Toolik Lake sediments, after the addition of 2% (vol/vol) Prudhoe Bay crude oil, motor oil, diesel fuel, gasoline, n-hexane, or toluene, was examined after 21 days of incubation at 10°C. Diesel fuel, motor oil, gasoline, and toluene inhibited ¹⁴C-[lignin]-lignocellulose mineralization by 58, 67, 67, and 86%, respectively. Hexane-treated samples displayed an increase in the rate of ¹⁴C-[lignin]-lignocellulose mineralization of 33%. ¹⁴C-[cellulose]-lignocellulose mineralization was inhibited by the addition of motor oil or toluene by 27 and 64%, respectively, whereas diesel fuel-treated samples showed a 17% increase in mineralization rate. Mineralization of the labeled lignin component of lignocellulose appeared to be more sensitive to hydrocarbon perturbations than was the labeled cellulose component.     

Fungal decomposition of Abies needle and Betula leaf litter

The effect of litter type and incubation temperature on the ability of fungi to decompose leaf litter of subalpine trees was examined by a pure-culture test. Mass loss of Abies needle and Betula leaf litter and utilization patterns of lignin and carbohydrates were investigated under two temperature conditions (20 C and 10 C) and compared for 29 species in basidiomycetes, ascomycetes and zygomycetes. The decomposing ability was generally higher in basidiomycetes than in ascomycetes and zygomycetes. Mass loss (% original mass) of litter was higher in Betula than in Abies and higher at 20 C than at 10 C. The 29 fungi were divided into lignocellulose decomposers, cellulose decomposers and sugar fungi based on their substrate utilization in Abies and Betula litter. Mass loss of lignin and carbohydrates by lignocellulose and cellulose decomposers was higher in Betula than in Abies. Mass loss of carbohydrates was higher at 20 C than at 10 C, but the temperature did not influence mass loss of lignin, indicating lignin decomposition by fungi was less sensitive to temperature than carbohydrate decomposition. Lignin/carbohydrate loss ratio (L/C) of Collybia spp. that caused selective delignification was lower at 20 C than at 10 C. These results indicate that the decomposability of litter, lignin and carbohydrate was different between Abies and Betula and that temperature affected not only the rate at which fungi decompose litter but also the ability of fungi to use lignin and carbohydrates.     

Degradation of Softwood, Hardwood, and Grass Lignocelluloses by Two Streptomyces Strains

Two Streptomyces strains, S. viridosporus T7A and S. setonii 75Vi2, were grown on softwood, hardwood, and grass lignocelluloses, and lignocellulose decomposition was followed by monitoring substrate weight loss, lignin loss, and carbohydrate loss over time. Results showed that both Streptomyces strains substantially degraded both the lignin and the carbohydrate components of each lignocellulose; however, these actinomycetes were more efficient decomposers of grass lignocelluloses than of hardwood or softwood lignocelluloses. In particular, these Streptomyces strains were more efficient decomposers of grass lignins than of hardwood or softwood lignins.     

Degradation of extractive-free lignocelluloses by Coriolus versicolor and Poria placenta

Summary The wood-decay fungi Coriolus versicolor, a white-rot fungus, and Poria placenta, a brown-rot fungus, were grown on an extractive-free lignocellulose prepared from quackgrass (Agropyron repens). Their abilities to decompose this lignocellulose were compared to their abilities to decompose softwood (Picea pungens) and hardwood (Acer rubrum) lignocelluloses. The two fungi were grown on malt-extract dampened lignocelluloses at 28°C for up to 12 weeks. Replicate cultures were periodically harvested and lignocellulose decomposition was followed by monitoring substrate weight loss, lignin loss, and carbohydrate loss. Coriolus versicolor decomposed the lignin and carbohydrate components of the grass lignocellulose as efficiently as the softwood and hardwood lignocelluloses. Poria placenta, however, was not an efficient degrader of either lignin or carbohydrate in the grass lignocellulose. Poria placenta readily decomposed carbohydrate components of the softwood lignocellulose but not the hardwood lignocellulose.Paper number 81520 of the Idaho Agricultural Experiment Station     

Temporal relationship between the deposition and microbial degradation of lignocellulosic detritus in a Georgia salt marsh and the Okefenokee Swamp

Temperature dependence and seasonal variations in rates of microbial degradation of the lignin and polysaccharide components of specifically radiolabeled lignocelluloses were determined in sediment and water samples from a Georgia salt marsh and the nearby Okefenokee Swamp. Although temperature regimes in the two ecosystems were similar, rates of mineralization ofSpartina alterniflora lignocellulose in salt marsh sediments increased eightfold between winter and summer, whereas rates of mineralization of lignocellulose from an analogous freshwater macrophyte,Carex walteriana, in Okefenokee sediments increased only twofold between winter and summer. Temperature was the major factor influencing seasonal variations in rates of lignocellulose degradation in both environments. At any given temperature, no substantial differences in lignocellulolytic potential were observed with sediment samples collected at each season. In both ecosystems, the bulk of the lignocellulosic detritus was not degraded at the time of its peak deposition during the fall and winter. Instead, the periods of maximal decomposition occurred during the following spring and summer. These results suggest that periods of maximal nutrient regeneration from the mineralization of lignocellulosic detritus coincide with periods of highest primary production, and that, depending on hydrologic conditions, significant horizontal transport of essentially intact lignocellulosic material is possible due to the lag period between deposition and microbial degradation.     

Degradation of softwood [14C lignin] lignocelluloses and its relation to the formation of humic substances in river and pond environments

The fate of lignin in water and sediment of the Garonne river (France) and of a pond in its floodplain was examined using specifically labeled [¹⁴C-lignin] lignocelluloses. No significant differences appeared in the mineralization rate of alder, poplar or willow [¹⁴C-lignin] in running water samples. Conversion of total radioactivity to ¹⁴CO₂ ranged between 18.7% and 24.4% after 120 days of incubation. Degree of ¹⁴C-labeled lignin mineralization in standing water and sediments was clearly lower, especially in submerged sediments, and was correlated with oxygen supply. After 60 days of incubation 3.3% to 7.9% of the ¹⁴C-labeled lignin was recovered in water samples as dissolved organic carbon originating from microbial metabolism. In water extracts from sediment the percentage of dissolved organic ¹⁴C was only 0.4% to 1.3% of the applied activity. In the humic fraction extracted from sediments it did not exceed 4.4% which was much lower than in soils. No significant difference appeared between river and pond conditions for humic substances formation.     

Impact of nitrogen and phosphorus on [C]lignocellulose decomposition by stream wood microflora

Nutritional and physical factors affecting the decomposition of [C]lignocellulose prepared from Douglas fir (Pseudotsuga menziesii) were examined by incubating the labeled substrate with homogenized surface wood scrapings obtained from a Douglas fir log in a Pacific Northwest stream. Incubations were conducted in distilled water, in stream water collected from four different sources, or in a defined mineral salts solution with or without supplemental N (KNO(3)). Decomposition rates of [C]lignocellulose, as measured by CO(2) evolution, were greater in each of the four filter-sterilized sources of stream water than in distilled water alone. Decomposition experiments conducted in stream water media with the addition of defined mineral salts demonstrated that [C]cellulose decomposition was stimulated 50% by the addition of either KNO(3) or KH(2)PO(4)/K(2)HPO(4) and further enhanced (167%) by a combination of both. In contrast, [C]lignin decomposition was stimulated (65%) only by the addition of both N and P. Decomposition of [C]lignocellulose was greatest when supplemental KNO(3) was supplied in concentrations of at least 10.0 mg of N liter but not increased further by higher concentrations. The decomposition of [C]lignocellulose increased as the incubation temperature was raised and NO(3)-N supplementation further increased these rates between three-and sevenfold over the range of temperatures examined (5 to 22 degrees C). Accumulation of NH(4) (2 to 4 mg of N liter) was always observed in culture filtrates of incubations which had been supplemented with KNO(3), the quantity being independent of NO(3) concentrations >/= 10 mg of N liter. The role of supplemental NO(3) in the decomposition of [C]lignocellulose is discussed in relation to wood decomposition and the low concentrations of N found in stream ecosystems of the Pacific Northwest.     

Effects of Selected Assay Parameters on Measurement of Lignocellulose Mineralization with a Radiolabeled Substrate

Varying the amount of labeled substrate or the amount of leaf material resulted in significant nonlinear changes in lignocellulose mineralization, as measured with natural [¹⁴C]lignin-labeled lignocellulose. The use of periodic rather than continuous aeration was found not to have significant effects on measured mineralization.