Soil Respiration Activity Research Articles

Use of 13CO2 as a Tool to Investigate Carbon Partitioning in Field and Greenhouse-grown Apple Trees

Instrumentation to measure soil respiration is currently readily available. However, the relationship between soil respiration and root activity or root mass is not known. Herein we report on preliminary result using a 13CO2 pulse to the foliage to determine if 13C respiration can be related to either root activity or root mass. An experiment was performed in the field on a 5-year-old apple tree (cv. Jonagold on M7). The tree canopy was enclosed in a Mylar® balloon and 2.1 g 13CO2 were pulsed in the balloon for 1 hr. After the pulse, air emitted by the soil and selected roots was collected every 6 hr for 8 days, by bubbling it in 2 M NaOH. 13C/12C ratios were measured with the mass spectrometer. The emission of 13CO2 from the roots gradually increased after the pulse reaching a peak after 100 hr. The emission trend was not linear, but it seemed related to soil temperature. Leaves and fruit were also collected daily. 13C content in leaves was 1.15% right after the pulse, but it progressively decreased to 1.09% at the end of the experiment. The experiment was then repeated on 12 potted apple trees (cv. Redcort on M7) in greenhouse conditions. Six of them were maintained well-watered, whereas six plants were subjected to a mild water stress, by watering them with half of the volume of water used for well-watered plants. After the two soil moisture levels were achieved, the tree canopies of all the 12 trees were pulsed. Leaves, stems, and roots were ground and run in the mass spectrometer. The results of root emission rate were found to be similar to the field experiment. Results also indicated that, in our experiment, stress did not affect root respiration rate. Specific details of the physiology data will be presented.

Organic matter, microbial biomass and enzyme activity of soils under different crop rotations in the tropics

Soil organic matter level, soil microbial biomass C, ninhydrin-N, C mineralization, and dehydrogenase and alkaline phosphatase activity were studied in soils under different crop rotations for 6 years. Inclusion of a green manure crop of Sesbania aculeata in the rotation improved soil organic matter status and led to an increase in soil microbial biomass, soil enzyme activity and soil respiratory activity. Microbial biomass C increased from 192 mg kg–1 soil in a pearl millet-wheat-fallow rotation to 256 mg kg–1 soil in a pearl millet-wheat-green manure rotation. Inclusion of an oilseed crop such as sunflower or mustard led to a decrease in soil microbial biomass, C mineralization and soil enzyme activity. There was a good correlation between microbial biomass C, ninhydrin-N and dehydrogenase activity. The alkaline phosphatase activity of the soil under different crop rotations was little affected. The results indicate the green manuring improved the organic matter status of the soil and soil microbial activity vital for the nutrient turnover and long-term productivity of the soil.

Short‐term decomposition of litter produced by plants grown in ambient and elevated atmospheric CO2 concentrations

The effects of elevated atmospheric CO2 (ambient + 340 μmol mol–1) on above‐ground litter decomposition were investigated over a 6‐week period using a field‐based mesocosm system. Soil respiratory activity in mesocosms incubated in ambient and elevated atmospheric CO2 concentrations were not significantly different (t‐test, P > 0.05) indicating that there were no direct effects of elevated atmospheric CO2 on litter decomposition.A study of the indirect effects of CO2 on soil respiration showed that soil mesocosms to which naturally senescent plant litter had been added (0.5% w/w) from the C3 sedge Scirpus olneyi grown in elevated atmospheric CO2 was reduced by an average of 17% throughout the study when compared to soil mesocosms to which litter from Scirpus olneyi grown in ambient conditions had been added. In contrast, similar experiments using senescent material from the C4 grass Spartina patens showed no difference in soil respiration rates between mesocosms to which litter from plants grown in elevated or ambient CO2 conditions had been added.Analysis of the C:N ratio and lignin content of the senescent material showed that, while the C:N ratio and lignin content of the Spartina patens litter did not vary with atmospheric CO2 conditions, the C:N ratio (but not the lignin content) of the litter from Scirpus olneyi was significantly greater (t‐test;P < 0.05) when derived from plants grown under elevated CO2 (105:1 compared to 86:1 for litter derived from Scirpus olneyi grown under ambient conditions). The results suggest that the increased C:N ratio of the litter from the C3 plant Scirpus olneyi grown under elevated CO2 led to the lower rates of biodegradation observed as reduced soil respiration in the mesocosms. Further long‐term experiments are now required to determine the effects of elevated CO2 on C partitioning in terrestrial ecosystems.

Effects of soil extracts from repeated plantation woodland of Chinese-fir on microbial activities and soil nitrogen mineralization dynamics

Effects of soil extracts from repeated plantation woodlands of Chinese-fir on soil fungi growth, the activities of microbial communities, and rates of net soil nitrogen mineralization were investigated. Soil extracts from replanted woodlands significantly inhibited soil non-pathogenic fungi growth, reduced soil respiration activities, and net soil nitrogen mineralization rates. However, soil extracts from replanted woodland increased the growth of pathogenic fungi. The combination of soil extracts and pathogenic fungi did not significantly reduce the growth of Chinese-fir seedlings when compared to the soil extracts alone. The combination of soil extracts with pathogenic and non-pathogenic fungi significantly increased the growth of Chinese-fir seedlings when compared to the combination of soil extracts and pathogenic fungi. The results suggest that the allelochemicals from soil extracts, rather than pathogenic fungi, are the key factor regulating the productivity and nitrogen cycling in repeated plantation woodlands.

Vitality fertilization of Scots pine stands growing along a gradient of heavy metal pollution: short-term effects on microbial biomass and respiration rate of the humus layer.

In 1992 forest vitality fertilization experiments were established on a heavy metal deposition gradient with four treatments in three replications at distances of 0.5, 4 and 8 km from a Cu-Ni smelter in order to estimate their impact on the disturbed forest ecosystem. The increase in Cu concentration in the humus (F/H) layer of the Calluna site type Scots pine (Pinus sylvestris) stands from ca. 300 to 8000 mg kg(-1) d.m. (dry matter) along the 8 km long transect towards the smelter resulted in declining soil microbial biomass and soil respiration activity. Three independent measurements of microbial biomass: C(mic)-FE (fumigation extraction), C(mic)-SIR (substrate induced respiration), and ATP have been used together with an indicator of fungal biomass (ergosterol) and microbial activity (soil respiration). Within this Cu pollution range, all the measured microbial biomass levels declined to 10%-28% of the control plot values and activity assessed by respiration was lowered to 16%. Liming has increased the C(mic)-SIR and respiration rate. Treatments with test fertilizer, made from grounded apatite, did not result in different microbial biomass and respiration rate values compared to the respective controls along the whole gradient. Nitrogen + lime treatments resulted in similar changes to lime alone. No changes, as compared to the respective control, could be detected with nitrogen fertilization at the less polluted end of the gradient.

Microbial responses of forest soil to moderate anthropogenic air pollution

There is a need to introduce soil microbiological methods into long term ecological monitoring programs. For this purpose we studied the impact of moderate anthropogenic air pollution in polluted and less polluted area districts, forest site types Calluna (CT), Vaccinium (VT) and Myrtillus (MT) and the amount of organic matter, measured as carbon content on the soil respiration activity and the ATP content. The main sources of local air pollutants (SO2 and NOx) in the polluted area district were from the capital' region and an oil refinery. Humus (F/H-layer) and the underlying 0 to 5 cm mineral soil samples were collected from 193 study plots located in the 5300 km2 study area. We found that the soil respiration rate in humus layer samples was lower in the polluted area district compared to the less polluted one (16.0 and 19.5 μL CO2 h−1g−1 dw, respectively), but the difference occurred only in the dry, coarse-textured CT forest site type. The mineral soil respiration rate and the mineral soil and humus layer ATP content were not affected, by the air pollution. Most of the variations of the biological variables were explained primarily by the soil carbon content, secondly by the forest site type and thirdly by the area division.

Soil microorganisms at different CO2 and O2 tensions

Microbial biomass and activity were determined in cambisol incubated under ambient and increased (up to 2.23 mmol/L) CO2 concentrations. An immediate negative response of the soil microbial community to [CO]2 increase was observed during the first day with respect to microbial biomass, soil respiration and specific respiration activity (both expressed as CO2 evolution). In contrast, O2 consumption was not affected but anabolic utilization of available substrate increased. These phenomena were observed under conditions of increased CO2 tension but without any change in O2 concentration.

The effect of plant material grown under elevated CO2 on soil respiratory activity

The biodegradability of aerial material from a C4 plant, sorghum grown under ambient (345 µmol mol−1) and elevated (700 µmol mol−1) atmospheric CO2 concentrations were compared by measuring soil respiratory activity. Initial daily respiratory activity (measured over 10 h per day) increased four fold from 110 to 440 cm3 CO2 100g dry weight soil−1 in soils amended with sorghum grown under either elevated or ambient CO2. Although soil respiratory activity decreased over the following 30 days, respiration remained significantly higher (t-test;p>0.05) in soils amended with sorghum grown under elevated CO2 concentrations. Analysis of the plant material revealed no significant differences in C:N ratios between sorghum grown under elevated or ambient CO2. The reason for the differences in soil respiratory activity have yet to be elucidated. However if this trend is repeated in natural ecosystems, this may have important implications for C and N cycling.

Soil pCO2, soil respiration, and root activity in CO2-fumigated and nitrogen-fertilized ponderosa pine

The purpose of this paper is to describe the effects of CO2 and N treatments on soil pCO2, calculated CO2 efflux, root biomass and soil carbon in open-top chambers planted with Pinus ponderosa seedlings. Based upon the literature, it was hypothesized that both elevated CO2 and N would cause increased root biomass which would in turn cause increases in both total soil CO2 efflux and microbial respiration. This hypothesis was only supported in part: both CO2 and N treatments caused significant increases in root biomass, soil pCO2, and calculated CO2 efflux, but there were no differences in soil microbial respiration measured in the laboratory. Both correlative and quantitative comparisons of CO2 efflux rates indicated that microbial respiration contributes little to total soil CO2 efflux in the field. Measurements of soil pCO2 and calculated CO2 efflux provided inexpensive, non-invasive, and relatively sensitive indices of belowground response to CO2 and N treatments.

Soil microbial biomass and activity of a disturbed and undisturbed shrub-steppe ecosystem

Disturbance of shrub-steppe soils and alterations in plant cover may affect the distribution, size and activity of soil microorganisms and their ability to biogeochemically cycle essential nutrients. Therefore, the soil microbial biomass and activity and selected soil enzyme activities were determined for two arid ecosystems, an undisturbed perennial shrub-steppe and annual grassland, which was initially shrub-steppe and has been an annual grassland since the disturbance caused by farming ceased in the 1940s. Soils were sampled at 0–5 and 5–15 cm depths beneath sagebrush ( Artemisia tridentata Mutt.), bluebunch wheatgrass [ Elytrigia spicata (Pursh) D.R. Dewey] and cryptogamic soil lichen crust at the perennial site and beneath downy brome ( Bromus tectorum L.) at the annual grassland site. Soils were analyzed for physical properties, inorganic N, microbial biomass C and N, respiration and several enzymes. The soil pH and bulk density usually increased, while inorganic N, total N and total C decreased as a function of soil depth. Soil microbial biomass C and N, soil respiration and soil dehydrogenase activity were 2–15 times higher in the top 5 cm of soil than at the 5–15 cm depth regardless of plant type. Loss of this surface soil would therefore be detrimental to microbially-mediated cycling of nutrients. Surface soil (0–5 cm depth) microbial biomass C and N and soil respiration, dehydrogenase and phosphatase activity were influenced by plant type and decreased in the order B. tectorum A. tridentata = E. spicata soil crust. Spatial distribution of plant species at the shrub-steppe site resulted in “islands” of enhanced microbial biomass and activity underneath the shrubs and grasses when compared to the interplant areas covered with soil crust. When plant cover was used to compute a landscape estimate of soil microbial biomass C and N for the perennial shrub-steppe and the annual grassland, similar values were obtained. This indicates that while the distribution of microorganisms may be more heterogeneous in the shrub-steppe, the average across the landscape is the same as the more homogeneous annual grassland.

The influence of soil compaction on microbial biomass and organic carbon turnover in micro-and macroaggregates

Agricultural practices with high traffic and with low input of organic material into the soil result in the deterioration of soil structure leading to soil compaction. It is accompanied by the reduction of gas exchange and by limited colonizable habitats. The changes in microbial biomass and its activity cannot be readily explained by interactions of altered gas and water exchange. In order to explain the differences in biological activity of compacted and uncompacted soils, the soil structure related microbial turnover was observed. The content and the availability of soil organic carbon, microbial biomass and respiration activity in micro- (< 0.2 mm) and macroaggregates (2–5 mm) from the plots with different wheel induced compactive treatments were measured in the layers 0–10, 10–20 and 20–30 cm. In the topsoil (0–30 cm) of the wheel tract plot the higher content of total carbon (0.942% C org) and higher availability of C than in the no traffic (0.907% C org) and high traffic (0.908% C org) plots were established. The compacted plots contained less total carbohydrates in macroaggregates. The average value of microbial biomass was lower only in the high traffic plot — 99 μg C g −1 against 159 in the no traffic plot. The compacted plots differed from the other treatments in the distribution of microbial biomass in soil layers; the maximum of microbial biomass was in the lower layers (20–30 cm) instead of in the surface layer. The “potential” activity of microbial biomass reached maximal values in the high traffic plot.

Microbial biomass turnover and enzyme activities following the application of farmyard manure to field soils with and without previous long-term applications

We studied the build-up and turnover of microbial biomass following the addition of farmyard manure to an unmanured soil and to soils from a long-term experiment in which different levels of farmyard manure had been applied for the last 23 years. The application of farmyard manure at 15–90 t ha-1 to previously unmanured soil increased the microbial biomass during the first 3 months of incubation but a gradual decline occurred with further incubation for up to 12 months. Microbial biomass C was positively correlated with soil organic C and ranged from 1.8% to 2.2% of organic C after 12 months of farmyard manure applications. Biomass turnover increased with the application of farmyard manure, ranging from 0.81 to 0.87 year-1 with various levels of manure. Amendment of soils from the long-term manure experiment with various levels of farmyard manure led to a build-up and decline in biomass C as seen in the unmanured soils, but biomass C was higher in all treatments compared to the corresponding unmanured soil treatments. Biomass turnover was greater compared to the unmanured soil treatments and it decreased with increasing levels of farmyard manure. The average soil respiratory activity increased with increasing levels of farmyard manure, but respiratory activity per unit of biomass C decreased with increasing levels of manure. Enzyme activities were greater in long-term manured soils compared to unmanured soils amended with various levels of manure. There was a significant correlation between biomass C and enzyme activities.

The distribution of pollutant heavy metals and their effect on soil respiration and acid phosphatase activity in mineral soils of the Rouyn-Noranda region, Québec

The distribution of pollutant heavy metals (Cu, Zn, Ni, Cd and Pb) from a CuZn smelter near Rouyn-Noranda, Québec and their effect on soil respiration and phosphatase activity were studied in mineral soils along two transects oriented in the direction of prevailing winds. The LFH horizon was the more contaminated soil layer having retained the larger part of the atmospheric pollution. The 0–15 cm layers also showed high levels of heavy metals in the vicinity of the smelter. The log-concentration of pollutant heavy metals decreased progressively with the log-distance from the emitting point, and did not accumulate into the 15–30 cm layer significantly. Cd and Pb appeared to have less mobility than Cu and Zn. Soil respiration was a better indicator in assessing the effect of heavy metal pollutants on soil microbial populations than was acid phosphatase activity in these mineral soils with different organic contents.

Effect of Green Manure an the Respiration Activity and Some Chemical Properties of the Orthic Luvisol

Summary The results of respirometric tests of soil samples from a field trial (1981–1984) showed that organic matter application (green phytomass of vetch oats mixture) characterized by a high content of easily decomposable organic compounds is a highly effective regulatory factor of respiration activity in soil. Inorganic fertilizers and liming in interaction with organic substrate application mostly supported the organic matter stabilization in the soil. Green organic matter favourably influenced the chemical properties of the soil tested and cation exchange capacity and the sum of exchangeable basic cations.

Influence of soil mineral nitrogen content on soil respiratory activity and measurements of microbial carbon and nitrogen by fumigation-incubation procedures

The influence of soil mineral-N (min-N) content on rates of respiratory activity (CO2 production), and measurements of microbial biomass carbon and nitrogen by fumigation-incubation procedures, was investigated with three fertile soils and one low-fertility soil. These soils were sampled at each of the four seasons from pastures in which intensive grazing can result in high levels of min-N. Values of CO2-C flush and thin-N flush [the difference between CO2-C and min-N produced by fumigated samples and an unfumigated contl ol (or, for CO2-C only, fumigated control)] were used as indices of biomass C and N. Soil min-N content was adjusted by the addition of ammonium sulfate (approx. 50 �g NH4+-Ng-1 soil). In the low fertility soil and two of the fertile soils, added min-N had no significant effect on CO2 production or CO2-C flush values. In the other soil (Castlepoint), the added min-N usually lowered CO2 production in unfumigated samples, and increased CO2-C flush values when an unfumigated control was used; CO2-C flush values were not affected when a fumigated control was used. Use of a fumigated control for estimating biomass C in these grassland soils is recommended. Added min-N had few significant effects on the min-N flush values of the three fertile soils. In the low-fertility soil (Pomare), the min-N flush values of summer and autumn samples were appreciably higher in the presence of added min-N, with the results suggesting that the min-N flush values of the samples without added min-N were erroneously low because of N immobilization. Overall, min-N flush measurements appear to provide a satisfactory index of microbial biomass in fertile soils under pasture, but care in the interpretation of min-N flush values from low-fertility grassland soils seems advisable.

Nutrient cycling following whole-tree and conventional harvest in northern mixed forest

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 &gt; CH &gt; 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.

Interactions between soil animals and ectomycorrhizal fungal mats

Estimates of microbial biomass were made for ectomycorrhizal fungal mats colonizing mineral soil in a 50–75-year-old Douglas-fir stand in western Oregon. The ectomycorrhizal fungal mats are from the basidiomycete, Hysterangium setchellii. Numbers and biomass of soil animals including microarthropods and nematodes were estimated for both fungal mat and non-mat areas. The mats generally showed a significantly greater microbial biomass and also greater numbers of soil microarthropods. Protozoans were also sampled and exhibited greater abundance in fungal mats for amoebae and ciliates, but not flagellates. We hypothesize that these mats represent a larger and more active microbial biomass, available as a soil-animal food resource. Fungal mats had greater concentrations of soil C and soil N, and soil respiration and enzyme activity rates were significantly greater in mat than non-mat soil.

The pattern of winter respiratory response to temperature, moisture, and freeze–thaw exposure in Bouteloua gracilis dominated grassland soils of southwestern Alberta

Winter respiratory activity of soils from Bouteloua gracilis dominated grassland of southwestern Alberta was examined, both under in situ field conditions and over a matrix of defined laboratory conditions. The effect of winter thaw conditions was very pronounced on observed rates of soil surface CO2 evolution. Under conditions of diurnally fluctuating air temperatures, from ca. −18 to +8 °C, soil surface temperatures in early January ranged from ca. −12 to +4 °C, while concurrently measured respiratory activity ranged from less than 2 to over 16 mg CO2∙m−2∙h−1. By early spring, soil surface heating was even more extreme as a result of the greater magnitude of midday insolation exposure, with observed mean values of CO2 release ranging from less than 10 to over 60 mg CO2∙m−2∙h−1. Laboratory incubations showed continued, although low rates of respiratory activity in soils held at subzero temperatures, with a marked biphasic response pattern evident in Arrhenius plots of soil respiration. Predicted cumulative soil surface CO2 release was estimated at 34–48 g CO2∙m−2, depending on whether the effects of observed postthaw respiratory response were included. Some 55% of overall winter soil respiratory activity in the top 8 cm of the soil profile is predicted to occur at temperatures between −4 and +4 °C, with the remaining respiratory activity largely occurring at temperatures up to 15 °C. This magnitude of soil surface CO2 release represents between 3 and 30% of previously observed estimates of belowground root mass loss in the winter period, depending on whether this mass loss is presumed to occur over the entire winter period or mainly in early spring, coinciding with the peak period of root exudate production.

Herbicide toxicity and microbial responses in soil

AbstractThe question mark placed on a few herbicides because of their longer persistence in Black Cotton soil made this ecotoxicological assessment necessary. Since microbial responses can be used as an indicator of herbicide toxicity, soil respiration, dehydrogenase, and viable bacterial counts were used as the parameters to assess herbicide toxicity. Basalin, Lasso, and Tafazine are used in Black Cotton Soil of Southwest part of India. Soils treated with 1,5, and 25 ppm (w/w) and assessed 1, ε, 11, 16, and 21 days later, indicated a significant inhibitory effect on microbial activity measured in terms of these parameters. The improvement in soil quality started after 16–21 days in Basalin treated soil only. Further, there exists a correlation between soil respiration and number of bacterial colonies, and soil respiration and dehydrogenase activity. The study warrants a rigorous screening of all the recommended preemergence herbicides in Black Cotton soil of this fertile area.

Effect of Simulated Acid Precipitation on Soil Microbial Activity in a Typic Quartzipsamment

AbstractThe effects of acid precipitation on microbial and enzyme activities were determined in a field study near Melrose, FL. Three transects of two plots each were irrigated with lake water acidified with 7:3 (v/v) H2SO4/HNO3 to pH 3.0 or 3.6, or with unacidified lakewater (pH 4.6, control) at a rate of 10 cm/week for 20 weeks. The experimental plots were divided into covered and uncovered subplots to determine the effect of excluding natural rainfall (pH 4.6). The application of 200 cm of simulated acid precipitation did not significantly influence soil pH, respiration, or arylsulfatase activity. Phosphatase activity decreased under the pH 3.0 treatment and urease activity was stimulated by the pH 3.6 treatment. The amount of N mineralized over a 12‐week incubation period was lower in soil from the pH 3.0 treatmenthan in soil from the pH 3.6 and 4.6 treatments. After the application of 200 cm of simulated acid rain; soil pH, respiration, and phosphatase activity levels were lower in the plots protected from natural rainfall. Twenty‐four weeks after the last acid application there were no differences in any of the measured parameters between the pH treatments.