Soil CO2 Evolution Research Articles

Soil CO2 evolution in Florida slash pine plantations. I. Changes through time

Soil CO2 evolution rates were measured in slash pine (Pinuselliottii) plantations of three ages in north Florida. At the mature (29-year-old) plantation, which had a closed canopy and a well-developed forest floor of litter and humus overlying the mineral soil, C storage in detritus in the mineral soil was relatively low and soil C release was relatively high (13.0 t•ha−1•year−1). C release was highest (22.7 t•ha−1•year−1) at the clear-cut site, presumably because of high temperatures and rapid decomposition of detritus added during the harvest, and lowest (8.2 t•ha−1•year−1) at the 9-year-old plantation. For a range of forest sites, soil CO2 evolution rates and the magnitude and direction of changes after harvesting show latitudinal variation that probably depends not only on the amount of C contained in dead organic matter in the soil and its decomposition rate but also on the treatment of slash left after harvesting.

Effects of Acid Irrigation on Carbon Dioxide Evolution, Extractable Nitrogen, Phosphorus, and Aluminum in a Deciduous Forest Soil

AbstractA study was initiated to determine the effects of sulfuric and nitric acid irrigation on CO2 evolution, and N, P, and Al availability in a deciduous forest soil. Irrigation with H2O, H2SO4, or HNO3 at 0.05 mol (p+) m−2 and 0.5 mol (p+) m−2 for 1 yr had no consistent effect on CO2 evolution, soil NH+4, extractable P, or extractable Al in a deciduous forest soil under field conditions. Irrigation with HNO3 caused temporary increases in soil NO‐3, but irrigation with H2SO4 had no effect on soil NO‐3. Nitrogen mineralization and nitrification by aerobic incubation were also unaffected by treatments. Seasonal variations in CO2 evolution, NH+4, and extractable P were pronounced, with peaks in CO2 and NH+4 in June and a peak extractable P in August.

Effects of Forest Conversion on the Carbon Budget of a Tropical Soil

To determine how the conversion of mature tropical forests to secondary forests affects the soil carbon budget, major soil carbon storages, inputs, and CO2 evolution from a tropical inceptisol were measured over a six-month period in both a mature lowland Tropical Premontane Wet Forest and a nearby secondary site located on the same soil type. Total carbon storage in and on the mature forest soil was composed of 9330 gC/m2 in soil organic matter, 1850 gC/m2 in litter and 340 gC/m2 in small roots (diameters <5 mm); larger roots were not measured. Average daily inputs to the mature forest soil included 1.3 gC/m2 in litterfall and 0.10 gDOC/m2 in precipitation (throughfall + stem flow). The evolution of CO2 from the mature forest soil averaged 3.4 gC/m2 d, or 2.6 times the average rate of litterfall. Total carbon storage in and on the soil of the second-growth was composed of 8600 gC/m2 in soil organic matter, 700 gC/ m2 in litter and 157 gC/m2 in small roots, or 2060 gC/m2 less than in the mature forest. Litterfall in the young second-growth averaged 0.7 gC/m2 d, and precipitation averaged 0.12 gDOC/m2 d. Soil-CO2 evolution averaged 4.6 gC/m2d, or 1.4 times the rate in the mature forest. Measured inputs of carbon to the soil were considerably less than soil-CO2 evolution rates in both sites; part or all of these differences can be attributed to root production, which was not measured. It was found that forest conversion to young secondary vegetation resulted in losses of soil organic matter, fewer small roots, less non-woody and large wood litter, lower rates of litterfall, and increased rates of soil-CO2 evolution. TROPICAL FORESTS ARE BEING RAPIDLY CONVERTED to a variety of secondary plant communities. Potential consequences of tropical deforestation range from local soil degradation to changes in the world's climate, yet the specific changes that accompany forest conversion are not well documented. The soil is of particular importance after forest removal because it supplies many of the innocula, nutrients, and materials used to rebuild the aboveground community. Traditional cropping systems often lead to soil nutrient and organic matter losses (Nye and Greenland 1960, 1964; Brams 1971; Krebs 1975). Natural fallows, in contrast, tend to increase the fertility of depleted soils (Nye and Greenland 1960). Understanding soil processes under natural secondary vegetation may therefore aid in the development of soil-conserving production systems. I have focused upon soil carbon because carbon is initimately involved in virtually all biological processes, and organic matter, even when present in small amounts, is an extremely important soil constituent. In highly weathered tropical soils organic matter provides most of the cation exchange sites (Nye and Greenland 1960, Sanchez 1976), improves soil aggregation and stability (Allison 1973, Sanchez 1976, Cheng 1977), and is a major source of plant nutrients (Bornemisza 1966, Allison 1973, Sanchez 1976). In addition, soil carbon is dynamic, and reflects changes in the aboveground community. The purpose of this study was to determine how conversion of a mature forest to young secondary vegetation affected the carbon balance of a tropical inceptisol. The major components of a soil carbon budget are shown in Figure 1. I quantified the carbon storages in soil organic matter, litter, and small roots (diameters < 5 mm); carbon inputs in litterfall, throughfall, and stem flow; and carbon release, in the form of CO2, from the soil surface in both a mature forest and a young secondary site in lowland, humid Costa Rica. I then compared the carbon budgets of the two sites to determine the effects of forest conversion on soil carbon.

Effects of 2,4-d on nitrogen fixation and carbon dioxide evolution in a soil microcosm

Two concentrations of 2,4-dichlorophenoxyacetic acid (2,4-D) 1.7 kg ha−1 and 3.4 kg ha−1 were applied to oats (Avena sativa L. ‘Orbit’) grown in terrestrial microcosms in a sandy soil. Carbon dioxide evolution and non-symbiotic N2 fixation (C2H2 reduction) were measured weekly. On day 70 of the study, 2,4-D was applied a second time at the same application rates and soil CO2 evolution and N2 fixation were measured more frequently. Soil CO2 evolution over 24 h period was significantly decreased by 40 to 50% at both application rates of 2,4-D. This response lasted less than 7 days. Nitrogen fixation was unaffected by 2,4-D except for an unexplained decrease observed in the 1.7 kg ha−1 treatment 35 days after 2,4-D application. This effect was not observed on the following sampling date. The second application of 2,4-D failed to produce any significant change in soil CO2 evolution or N2 fixation. From these studies we conclude soil microbial populations either degraded or became acclimated to 2,4-D as a result of the initial application and that 2,4-D has no significant adverse effect on N2 fixation or soil CO2 evolution.

Effects of Plutonium on Soil Microorganisms

As a first phase in an investigation of the role of the soil microflora in Pu complex formation and solubilization in soil, the effects of Pu concentration, form, and specific activity on microbial types, colony-forming units, and CO(2) evolution rate were determined in soils amended with C and N sources to optimize microbial activity. The effects of Pu differed with organism type and incubation time. After 30 days of incubation, aerobic sporeforming and anaerobic bacteria were significantly affected by soil Pu levels as low as 1 mug/g when Pu was added as the hydrolyzable Pu(NO(3))(4) (solubility, <0.1% in soil). Other classes of organisms, except the fungi, were significantly affected at soil Pu levels of 10 mug/g. Fungi were affected only at soil Pu levels of 180 mug/g. Soil CO(2) evolution rate and total accumulated CO(2) were affected by Pu only at the 180 mug/g level. Because of the possible role of resistant organisms in complex formation, the mechanisms of effects of Pu on the soil fungi were further evaluated. The effect of Pu on soil fungal colony-forming units was a function of Pu solubility in soil and Pu specific activity. When Pu was added in a soluble, complexed form [Pu(2)(diethylenetriaminepentaacetate)(3)], effects occurred at Pu levels of 1 mug/g and persisted for at least 95 days. Toxicity was due primarily to radiation effects rather than to chemical effects, suggesting that, at least in the case of the fungi, formation of Pu complexes would result primarily from ligands associated with normal (in contrast to chemically-induced) biochemical pathways.

Slash and Burn Impacts on a Costa Rican Wet Forest Site

Impacts of felling, mulching, and burning on budgets of C, N, S, P, K, Ca, and Mg; rates of CO2 evolution from the soil; soil seed storage; and plant growth were evaluated. The felled tropical evergreen forest was 8—9 yr old, interspersed with patches of 70—yr—old forest and had a leaf area index of 6 and aboveground biomass of 5.2 kg/m2. Harvest of the largest trees removed 18% of the S, and >10% of all other elements except N. During the 11—wk mulching and drying periods, 33% of the K and 13% of the P disappeared, but losses of other elements were <6%. Burn temperatures were >620°C in surface fuels, but soil temperatures were seldom >100°C at 1 cm or >50°C at 2 cm. The burn volatilized 1600 g/m2 C, 49 g/m2, and 13 g/m2 S. Postburn wind and water erosion of ash, plus leaching, removed 34 g/m2 N, 20 g/m2 K, 1 g/m2 P, 39 g/m2 Ca, and 7 g/m2 Mg, but insignificant amounts of C and S. After the burn and onset of the rains, 57% of the initial amount of N and 39% of the initial C still remained because of conservation of the organic—rich upper 3 cm of soil. Soil CO2 evolution was greater from beneath the 11—wk—old slash (3.6 gC°m—2°d—1), probably because the slash conserved soil moisture better than the actively transpiring forest. After the burn both the burned field and forest soil evolved CO2 at °4.5 gC°m—2°d—1. At this rate, 154 d of decomposition and respiration would release as much C into the atmosphere as did the burn. Soil seed storage dropped from °8000 seeds/m2 (67 species) in the forest, to 6000 seeds/m2 (51 species) after 11 wk of mulching, to 3000 seeds/m2 (37 species) after the burn. The seeds not killed by the burn, the survival of mycorrhizal fungi, and the release of nutrients resulted in vigorous and diverse postburn regrowth.

Relations between soil microflora and CO2 evolution upon decomposition of cellulose

The investigation was carried out to study the relation between CO2 evolution and the changes in microflora in the case of cellulose-decomposition in soil with special attention to the heterogeneity of soil crumbs. The rates of CO2 evolution correlated with the number of Gram-negative bacteria, while the number of cellulose-decomposing microorganisms did not. The Gram-negative bacteria probably contribute directly to CO2 evolution by decomposing simple sugars produced from cellulose by cellulose-decomposing microorganisms. Both the Gram-negative bacteria and cellulose-decomposing microorganisms seemed to grow luxuriantly on the surface area of soil crumbs with added cellulose powder. Therefore, it is speculated that there is a cooperation between the Gram-negative bacteria and the cellulose-decomposing microorganisms with respect to cellulose decomposition in soil. The main locus where this reaction takes place may be the surface area of soil crumbs.

Influence of compound fertilizer and cupric sulfate on soil enzymes and CO2-evolution

1. Compound fertilization inhibits the enzymatic activities of the hydrolytic decomposition of litter. 2. In the nursery soil examined urease and xylanase activities had been distinctly reduced after six weeks, whereas cellulase and invertase activities had scarcely been affected after this period. 3. Through compound fertilization the enzymatic activities of intracellular dehydrogenases increased by the same amount as the microbial biomass. 4. It was proved that, in the case of litter decomposition, extracellular biochemical activity was not at all bound to be in direct relation to the microbial biomass, but that it is closely connected to the decomposible organic matter. 5. An additional treatment of the soil with cupric sulfate brought a toxic effect. Dehydrogenase activity was inhibited by a further 72%, urease and xylanase activities by 30%. Invertase activity was only reduced by 15% and cellulase activity by 10%. 6. The present studies make it possible to understand the complicated interaction between soil microorganisms and the plant, point to the inhibition of litter decomposition by chemical soil treatments (fertilization, addition of a heavy metal) and suggest the competition for nutrients between the plant and the soil microflora. 7. A new method for the determination of invertase activity in soils was developed.

Effect of SO2 and bisulfite on heterotrophic activity in an acid soil.

Glucose oxidation was inhibited in a forest soil (pH 4.01) previously exposed by 1.0 microliter of SO2 per liter, the extent of inhibition and the decline in pH being directly related to the length of exposure. The phase of rapid CO2 evolution in protein hydrolysate-amended soil previously treated with 5.0 microliter of SO2 per liter for 24 h or 1.0 microliter/liter for 48 h was delayed, but the degradation of the amino acid mixture then proceeded rapidly. Bacterial numbers in soil incubated for 48 h with 1.0 microliter of SO2 per liter were reduced, but the bacteria grew rapidly if glucose or an amino acid mixture was added after the exposure period. Low levels of bisulfite inhibited amino acid decomposition in soil at pH 3.89, but the effect was less pronounced in soil at pH 4.01. Comparable levels of sulfate were not toxic to carbon mineralization. Approximately 1.0 microgram of bisulfite S and about 20 microgram of sulfate S per g of soil appeared when the soil was treated with 1.0 microliter of SO2 per liter for 48 h. Bisulfite added to the soil disappeared readily. The possible ecological significance of the findings is discussed.

SO2 and NO2 effects on microbial activity in an acid forest soil

The rate of glucose decomposition and the pH fell in a forest soil (initial pH 4.06) exposed to 1.0 ppm SO2. No such effect was noted if the soil was exposed to 1.0 ppm nitrogen dioxide (NO2). Nitrite but not bisulfite (5μg N or S/g of soil) inhibited O2 consumption and CO2 evolution in the glucose-amended forest soil, and nitrite and bisulfite acted synergistically in inhibiting these processes. Iron and manganese were solubilized when the soil was exposed to 10 ppm SO2, but NO2 caused no such change.

The effect of partial sterilization of field soils by chemicals upon differential microbial counts, carbon dioxide activity, and rates of organic matter decomposition.

Varying dosage rates of calcium hypochlorite, mercuric chloride, and sodium propionate were used as partial sterilization agents in field and greenhouse trials to determine the effect on soil biological activity, and thereby, organic matter decomposition rates. Application of the chemicals often resulted in the initial stimulation of respiration rates. In greenhouse and field trials this stimulation was most commonly associated with the application of sodium propionate. Fungal counts decreased and bacterial counts increased when this chemical was used. Within 4 weeks after treatment, all rates of application of the various chemicals depressed soil CO2 evolution. Thirteen months after treatment, plots treated with 100 lb of mercuric chloride per acre had one quarter as many actinomycetes and total microbes, and one third as many fungi, as did the control plots. Respiration was also considerably lower. Calcium hypochlorite treated plots retained reduced total counts and sodium propionate reduced fungal counts. Respiration in these last plots was not depressed.The changes in organic matter decomposition due to chemical treatments were not statistically significant in the greenhouse or field studies.General lack of correlation between the three measures of biological activity used in this study indicate the necessity for the further development of methods for measuring the population of microorganisms in soil.

Effect of Douglas‐Fir Sawdust Mulches and Incorporations on Soil Microbial Activities and Plant Growth

AbstractSawdust and other wood wastes applied to soil may retard plant growth by inducing nitrogen deficiency but these effects with Douglas‐fir are less pronounced than with many other residues of wide C:N ratio. While Douglas‐fir wood is extremely low in nitrogen it is low also in available carbon. The predominating lignin‐cellulose complex is resistant and only slowly metabolized, enabling a minimum amount of nitrogen, repartitioned among successive crops of microbes, to suffice for long‐continued decomposition.Sawdust showed no direct toxicity and had little effect on soil pH. Resins and other extractives were readily decomposed. Apparent decomposition percentages based on 50 days CO2 production without added available nitrogen in soil respiration experiments were: for dextrose 60, wheat straw 48, red alder 40, ponderosa pine 33, western red cedar 33, Douglas‐fir 30, pitch 30, western hemlock 27, bark 26, and lignin 6%, respectively. Although added nitrogen fertilizer hastened decomposition of organic matter having wide C:N ratio, it commonly depressed cumulative CO2 evolution in soil respiration.Greenhouse and field studies indicate that to avoid induced nitrogen deficiency 5 to 10 pounds of nitrogen per ton of sawdust are generally sufficient during the first year; nitrogen additions the following 2 or 3 years may be successively halved. Douglas‐fir sawdust without added nitrogen often causes no retardation and in some cases significant increases of certain crops such as sunflowers and strawberries. Corn appeared much more sensitive to nitrogen deficiency. All wood wastes and cereal straws at 100 tons per acre have been found to depress plant growth unless nitrogen is added.