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1.
Intersite characterization and variability of soil respiration in different arable and forest soils 总被引:3,自引:0,他引:3
L. Beyer 《Biology and Fertility of Soils》1991,12(2):122-126
Summary Soil respiration was investigated in three loamy Orthic Luvisols (two arable, one forest soil), three sandy Haplic Podzols (also two arable, one forest soil) with a modified intersite method according to Lundegardh (1924). The method allows characterization of the CO2-flux from the soil and interpretation of the different levels with regard to temperature, nutrient and air supply. The method is sensitive to tillage and fertilization effects. In the two arable Luvisols the mean cumulative respiration rate was not uniform compared with the forest soil; in one case it was much higher and in another much lower. CO2 evolution in the Podzol under spruce was much lower than in the two arable Podzols. In the sandy Podzols 5 replicate measurements gave adequate results, with an error probability of 10%, but in the loamy Luvisols it was necessary to use 10 replicates to specify the same degree of difference. If soil respiration is very high, immediately after fertilization with cattle slurry or dung on arable land, or after litterfall in a deciduous forest, more replicates are necessary. 相似文献
2.
《Communications in Soil Science and Plant Analysis》2012,43(9):1278-1291
Carbon dioxide (CO2) concentrations in arable soil profiles are influenced by autotrophic and heterotrophic respiration as well as soil physical properties that regulate gas transport. Although different methods have been used to assess dynamics of soil CO2 concentrations, our understanding of the comparability of results obtained using different methods is limited. We therefore aimed to compare the dynamics in soil CO2 concentrations obtained from an automated system (GMP343 sensors) to those from a manually operated measurement system (i.e., soil gas sampled using stainless steel needles and rods). In a winter wheat field in Denmark, soil CO2 concentrations were measured from 29 November 2011 to 14 June 2012 at upslope and footslope positions of a short catena (25 m). Carbon dioxide was measured at 20- and 40-cm soil depths (i.e., within and below the nominal plow layer) using the two measurement systems. Within the measurement range for the GMP343 sensors (0–20,000 ppm), mean results from the two systems were similar within the plow layer at the upslope (P = 0.060) and footslope (P = 0.139) position, and also below the plow layer at the upslope position (P = 0.795). However, results from the two systems deviated for the soil from the footslope position below the plow layer (P = 0.001). These results were partly attributed to larger variation in soil parameters below than within the nominal plow layer. The data suggested that generally the application of either system may be adequate; however, differences may occur in response to soil spatial variability. A better coverage of spatial variability is more easily addressed using manually operated systems, whereas temporal variability can be covered using the automated system. Depending on the aim of the study, the two systems may be used in combination to enhance both spatial and temporal data coverage. 相似文献
3.
Soil CO2 efflux is the primary source of CO2 emissions from terrestrial ecosystems to the atmosphere. The rates of this flux vary in time and space producing hot moments (sudden temporal high fluxes) and hot spots (spatially defined high fluxes), but these high reaction rates are rarely studied in conjunction with each other. We studied temporal and spatial variation of soil CO2 efflux in a water-limited Mediterranean ecosystem in Baja California, Mexico. Soil CO2 efflux increased 522% during a hot moment after rewetting of soils following dry summer months. Monthly precipitation was the primary driver of the seasonal trend of soil CO2 efflux (including the hot moment) and through changes in soil volumetric water content (VWC) it influenced the relationship between CO2 efflux and soil temperature. Geostatistical analyses showed that the spatial dependence of soil CO2 efflux changed between two contrasting seasons (dry and wet). During the dry season high soil VWC was associated with high soil CO2 efflux, and during the wet season the emergence of a hot spot of soil CO2 efflux was associated with higher root biomass and leaf area index. These results suggest that sampling designs should accommodate for changes in spatial dependence of measured variables. The spatio-temporal relationships identified in this study are arguably different from temperate ecosystems where the majority of soil CO2 efflux research has been done. This study provides evidence of the complexity of the mechanisms controlling the spatio-temporal variability of soil CO2 efflux in water-limited ecosystems. 相似文献
4.
《Soil Science and Plant Nutrition》2013,59(5):794-806
Abstract A regional evaluation of the soil organic carbon (SOC) dynamics for the chernozem zone in northern Kazakhstan is now vitally important for agricultural and environmental policy making. The objectives of the present study were: (1) to predict spatial and temporal variability in C input as crop residues using multi-temporal MODIS satellite images, (2) to clarify spatial and temporal variability in CO2 emission as SOC output using geostatistics and model s, (3) to clarify spatial and temporal variability in the SOC budget using the results from (1) and (2). The mean growing-season C input as plant residues in cereal fields ranged from 0.9 to 1.4 Mg C ha?1, with higher values in wet years. Carbon input as plant residues was higher in the northern part of the area than in the other parts. The average growing-season CO2 emission ranged from 0.9 to 1.1 Mg C ha?1, and was also higher in wet years than in dry years. In addition, more CO2 was emitted in the northern part of this area. Accordingly the average growing-season C budget ranged from –0.2 to 0.3 Mg C ha?1 and showed a negative correlation with air temperature during the crop-growing season. The 5-year C budget for different crop rotation systems ranged from –1.0 (3-year cropped cereal with 2-year bare fallow) to 0.4 (5-year continuous cereal cropped) Mg C ha?1. These results indicate that fallow-based crop rotation systems are degradative with regard to the SOC budget in the studied area. 相似文献
5.
There is a lack of understanding as to which soil property is the most important at regulating the temporal variability of soil CO2 emissions on China’s Loess Plateau. The objective of this study was to evaluate the CO2 emissions and their relationships to certain soil properties in a winter wheat (Triticum aestivum L.) field subject to no-till (NT) and conventional tillage (CT) practices. The CO2 emissions were signi?cantly higher in the CT (257.6 mg CO2 m?2 h?1), compared with the NT (143.8 mg CO2 m?2 h?1), treatment. Soil organic matter content and carbon stock were 8% and 14% higher, respectively, in the NT, compared with the CT, treatment. Regression analyses between the CO2 emissions and soil properties, including soil temperature and carbon stock, explained up to 88% and 60% of the temporal variability in CO2 emissions in the NT and CT treatments, respectively. Linear correlations between the soil temperature and CO2 emissions were recorded in both the NT and CT treatments. Soil temperature was the most important factor in terms of understanding the temporal variability in CO2 emissions in wheat fields of the study area. 相似文献
6.
Suzanne E. Allaire Sébastien F. Lange Jonathan A. Lafond Bernard Pelletier Athyna N. Cambouris Pierre Dutilleul 《Geoderma》2012
Spatial variability of greenhouse gas (GHG) emissions from agricultural lands is not well known although it has a great impact on the accuracy of GHG budget.The objectives of this study were to assess the spatial variability of CO2 emission fluxes (CO2-flux) and correlate these emissions with soil physico-chemical properties at two spatial scales and at different depths using a new geostatistical approach (coregionalization analysis with a drift, CRAD) that performs multiscale spatial analysis.Two agricultural sites with sandy and loamy soils were instrumented at 108 geo-referred sampling points and at two depths during spring 2007 where soil surface CO2-flux and soil physico-chemical parameters were measured. The CO2-flux presented spatial patterns characterized by different scales (i.e., non-spatial, small spatial and large spatial scale components), each describing a different fraction of its variability. About a quarter of CO2-flux variability at the first site and one fifth at the other site was attributed to the non-spatial component. Strongest correlations were obtained between CO2-flux and soil temperature, water saturation (Sw), elevation, electrical conductivity, soil bulk density, and the C/N ratio, but with differences between sites. Correlations were much stronger at large scale. Analyzing correlations between CO2-flux and soil properties without discriminating for scales can miss important scale-dependent processes controlling soil gas emissions. Scales at which these processes vary should therefore be taken into account. 相似文献
7.
Many researchers are interested in the variability of root-respired δ13CO2 as an indication of linkages between belowground plant respiration and canopy processes. Most studies in this area have, however, relied upon the assumption that temporal variability of total soil respired δ13CO2 reflects autotrophic soil processes, but in fact few supporting measurements of purely autotrophic soil respiration (partitioned from total soil respiration) are available. Here we use a combination of physical and isotopic partitioning methodologies to track the variability in autotrophic and heterotrophic soil δ13CO2 at five sites in Eastern Canada during a very dry growing season. Three dimensional modeling of soil isotopic transport dynamics in the static sampling chambers allow us to constrain measurement bias and to eliminate non-steady-state effects as a potential driver of observed variability. We provide experimental results that support a pivotal assumption made in prior interpretations of soil δ13CO2 dynamics: we observed minimal isotopic variability in soil microbial δ13CO2 efflux, but appreciable temporal variability in root-respired δ13CO2 at sites where near drought conditions were observed, suggesting that isotopic discrimination is likely linked to seasonal variations in transpirational demand. 相似文献
8.
D.C. Reicosky R.W. Gesch S.W. Wagner R.A. Gilbert C.D. Wente D.R. Morris 《Soil & Tillage Research》2008,99(2):221-231
Rising atmospheric carbon dioxide (CO2) concentrations from agricultural activities prompted the need to quantify greenhouse gas emissions to better understand carbon (C) cycling and its role in environmental quality. The specific objective of this work was to determine the effect of no-tillage, deep plowing and wind speeds on the soil CO2 concentration in muck (organic) soils of the Florida Everglades. Miniature infrared gas analyzers were installed at 30 cm and recorded every 15 min in muck soil plowed with the Harrell Switch Plow (HSP) to 41 cm and in soil Not Tilled (NT), i.e., not plowed in last 9 months. The soil CO2 concentration exhibited temporal dynamics independent of barometric pressure fluctuations. Loosening the soil resulted in a very rapid decline in CO2 concentration as a result of “wind-induced” gas exchange from the soil surface. Higher wind speeds during mid-day resulted in a more rapid loss of CO2 from the HSP than from the NT plots. The subtle trend in the NT plots was similar, but lower in magnitude. Tillage-induced change in soil air porosity enabled wind speed to affect the gas exchange and soil CO2 concentration at 30 cm, literally drawing the CO2 out of the soil resulting in a rapid decline in the CO2 concentration, indicating more rapid soil carbon loss with tillage. At the end of the study, CO2 concentrations in the NT plots averaged about 3.3% while that in the plowed plots was about 1.4%. Wind and associated aerodynamic pressure fluctuations affect gas exchange from soils, especially tilled muck soils with low bulk densities and high soil air porosity following tillage. 相似文献
9.
E. N. Ikkonen N. E. García-Calderón A. Ibáñez-Huerta J. D. Etchevers-Barra P. V. Krasilnikov 《Eurasian Soil Science》2018,51(6):674-681
Seasonal changes of the soil CO2 concentration and the rate of CO2 fluxes emission from the soil formed on the sediments of the former Lake Texcoco, which occupied a significant part of the Mexico Valley until the mid-17th century, were studied. The soils (Fluvic Endogleyic Phaeozems) were characterized by a low CO2 fluxes rate, which is related to their high alkalinity. The mean values of soil respiration were 6.0–14.1 mg C/(m2 h) depending on vegetation type, which corresponds to 60–157 g C/(m2 yr). The contribution of plants to the CO2 fluxes insignificantly varied by seasons and depended on the species composition of vegetation. The soil CO2 concentration and soil respiration in eucalypt (Eucalyptus globulus Labill.) plantation were two times higher than those in the grass–subshrub area, the ground cover of which consisted of Distichlis spicata (L.) Greene and Suaeda nigra (Raf.) J.F. Macbr. species. This can be related to the significant volumes of gas production during the respiration of eucalypt roots and associated rhizosphere community. The contribution of the root systems of grass cover to the soil CO2 fluxes in eucalypt plantation slightly varied within the year and was equal to 24% on the average. In the grass–subshrub area, its value varied from 41% in the cold season to 60% in the warm season. The spatial variability of soil CO2 concentration and its flux rate to the atmosphere was due to the differences in plant species composition and hydrothermal conditions, and their temporal trend was closely related to the seasonal accumulation of plant biomass and soil temperature. 相似文献
10.
A.R. Panosso J. Marques Jr. G.T. Pereira N. La Scala Jr. 《Soil & Tillage Research》2009,105(2):275-282
Soil management causes changes in physical, chemical, and biological properties that consequently affect soil CO2 emission (FCO2). Here, we studied the soil carbon dynamics in areas with sugarcane production in southern Brazil under two different sugarcane management systems: green (G), consisting of mechanized harvesting that produces a large amount of crop residues left on the soil surface, and slash-and-burn (SB), in which the residues are burned before manual harvest, leaving no residues on the soil surface. The study was conducted during the period after harvest in two side-by-side grids installed in adjacent areas, having 60 points each. The aim was to characterize the temporal and spatial variability of FCO2, and its relation to soil temperature and soil moisture, in a red latosol (Oxisol) where G and SB management systems have been recently used. Mean FCO2 emission was 39% higher in the SB plot (2.87 μmol m−2 s−1) when compared to the G plot (2.06 μmol m−2 s−1) throughout the 70-day period after harvest. A quadratic equation of emissions versus soil moisture was able to explain 73% and 50% of temporal variability of FCO2 in SB and G, respectively. This seems to relate to the sensitivity of FCO2 to precipitation events, which caused a significant increase in SB emissions but not in G-managed area emissions. FCO2 semivariogram models were mostly exponential in both areas, ranging from 72.6 to 73.8 m and 63.0 to 64.7 m for G and SB, respectively. These results indicate that the G management system results in more homogeneous FCO2 when spatial and temporal variability are considered. The spatial variability analysis of soil temperature and soil moisture indicates that those parameters do not adequately explain the changes in spatial variability of FCO2, but emission maps are clearly more homogeneous after a drought period when no rain has occurred, in both sites. 相似文献
11.
Knowledge about soil formation in tropical montane rainforests is scarce and patchy. We examined the altitudinal change of soils in a Bolivian tropical montane rainforest, aiming to illuminate the contribution of podzolization and hydromorphic processes to soil formation. In three transects from 1700 m to 3400 m a.s.l. we determined the pH, exchangeable cation exchange capacity, carbon and nitrogen stocks, and iron and aluminium fractions from 26 soil profiles. Three zones of different dominant soil forming processes were found: In the lower montane forest (LMF, 1700–2200 m a.s.l.), Dystropepts with high nutrient concentration and acidity were common. The pronounced change to the upper montane cloud forest (UMCF, 2200–2700 m a.s.l.) coincided with the appearance of Placorthods with more acidic conditions, deep ectorganic horizons and increasing translocation of sesquioxides. In the sub-alpine forest (SCF, 2700 m–3400 m a.s.l.), hydromorphic processes dominated over podzolization, resulting in Placaquods with low mineralization rate and nutrient concentration. This shows that due to increasing wetness and colder temperatures at high altitudes, dominant soil forming processes change from podzolization to hydromorphism soils with increasing altitude. 相似文献
12.
Creighton M. Litton Christian P. Giardina Gregory P. Asner 《Soil biology & biochemistry》2011,43(11):2315-2323
Soil-surface CO2 efflux (FS; ‘soil respiration’) accounts for ≥50% of the CO2 released annually by the terrestrial biosphere to the atmosphere, and the magnitude and variability of this flux are likely to be sensitive to climate change. We measured FS in nine permanent plots along a 5.2 °C mean annual temperature (MAT) gradient (13-18.2 °C) in Hawaiian tropical montane wet forests where substrate type and age, soil type, soil water balance, disturbance history, and canopy vegetation are constant. The objectives of this study were to quantify how the (i) magnitude, (ii) plot-level spatial variability, and (iii) plot-level diel variability of FS vary with MAT. To address the first objective, annual FS budgets were constructed by measuring instantaneous FS monthly in all plots for one year. For the second objective, we compared plot-level mean instantaneous FS in six plots derived from 8 versus 16 measurements, and conducted a power analysis to determine adequate sample sizes. For the third objective, we measured instantaneous FS hourly for 24 h in three plots (cool, intermediate and warm MATs). The magnitude of annual FS and the spatial variability of plot-level instantaneous FS increased linearly with MAT, likely due to concomitant increases in stand productivity. Mean plot-level instantaneous FS from 8 versus 16 measurements per plot yielded statistically similar patterns. The number of samples required to estimate plot-level instantaneous FS within 10% and 20% of the actual mean increased with MAT. In two of three plots examined, diel variability in instantaneous FS was significantly correlated with soil temperature but minimal diel fluctuations in soil temperature (<0.6 °C) resulted in minimal diel variability in FS. Our results suggest that as MAT increases in tropical montane wet forests, FS will increase and become more spatially variable if ecosystem characteristics and functioning undergo concurrent changes as measured along this gradient. However, diel variation in FS will remain a minor component of overall plot-level variation. 相似文献
13.
CO2 efflux plays a key role in carbon exchange between the biosphere and atmosphere, but our understanding of the mechanism controlling its temporal and spatial variations is limited. The purpose of this study is to determine annual soil CO2 flux and assess its variations in arable subtropical soils of China in relation to soil temperature, moisture, rainfall, microbial biomass carbon (MBC) and dissolved organic carbon (DOC) using the closed chamber method. Soils were derived from three parent materials including granite (G), tertiary red sandstone (T) and quaternary red clay (Q). The experiment was conducted at the Ecological Station of Red Soil, The Chinese Academy of Sciences, in a subtropical region of China. The results showed that soil CO2 flux had clear seasonal fluctuations with the maximum value in summer, the minimum in winter and intermediate in spring and autumn. Further, significant differences in soil CO2 flux were found among the three red soils, generally in the order of G>T>Q. The average annual fluxes were estimated as 2.84, 2.13 and 1.41 kg CO2 m−2 year−1 for red soils derived from G, T and Q, respectively. Soil temperature strongly affects the seasonal variability of soil CO2 flux (85.0-88.5% of the variability), followed by DOC (55.8-84.4%) and rainfall (43.0-55.8%). The differences in soil CO2 flux among the three red soils were partly explained by MBC (33.7-58.9% of the variability) and DOC (23.8-33.6%). 相似文献
14.
The effect of soil moisture,soil particle size,litter layer and carbonic anhydrase on the oxygen isotopic composition of soil‐released CO2
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Soil respiration and photosynthesis are the two largest carbon dioxide (CO2) fluxes between terrestrial ecosystems and the atmosphere and, therefore, the dominant processes influencing the oxygen isotopic composition of atmospheric CO2. The characterization of temporal and spatial variations of plant and soil‐related fluxes of different oxygen isotopologues of CO2 (12C16O2; 12C16O18O) is relevant to constraining the global carbon budget. The oxygen isotopic composition of soil‐respired CO2 is controlled by its release rate, the degree of isotopic equilibrium with soil water and the diffusional transport of CO2. The hypothesis of this study was that, as well as soil moisture, the soil particle size, the presence of an organic litter layer and the enzyme carbonic anhydrase (CA) would have a significant impact on the oxygen isotopic composition of soil‐released CO2. We tested this hypothesis with soil microcosm experiments on columns of medium and fine sand. Soil water content and soil texture influenced the isotopic composition of soil‐released CO2 significantly. A litter layer had a significant effect on the isotopic composition of water vapour but not on CO2 released from soil. In the absence of CA, oxygen isotope equilibration between the CO2 invasion flux and soil water was insignificant, whereas in the presence of CA about 55% of the CO2 invading the soil exchanged oxygen isotopes with soil water. Our findings highlight the importance of small‐scale variability of soil attributes for the oxygen isotopic composition of soil‐released CO2 as well as the strong impact of CA activity in soils. 相似文献
15.
CH4 production in a flooded soil as affected by elevated atmospheric CO2 was quantified in a laboratory incubation study. CH4 production in the flooded soil increased by 19.6%, 28.2%, and 33.4% after a 2-week incubation and by 38.2%, 62.4%, and 43.0%
after a 3-week incubation under atmospheres of 498, 820, and 1050 μl l–1 CO2, respectively, over that in soil under the ambient CO2 concentration. CH4 production in slurry under 690, 920, and 1150 μl l–1 CO2 increased by 2.7%, 5.5%, and 5.0%, respectively, after a 3-day incubation, and by 6.7%, 12.8%, and 5.4%, respectively, after
a 6-day incubation over that in slurry under the ambient CO2 concentration. The increase in CH4 production in the soil slurry under elevated CO2 concentrations in a N2 atmosphere was more pronounced than that under elevated CO2 concentrations in air. These data suggested that elevated atmospheric CO2 concentrations could promote methanogenic activity in flooded soil.
Received: 2 March 1998 相似文献
16.
Elienai Ferreira da Silva Mara Regina Moitinho Daniel De Bortoli Teixeira Elton da Silva Bicalho Guilherme Adalberto Ferreira Castioni Gener Tadeu Pereira Newton La Scala 《Soil Use and Management》2020,36(4):658-670
Soil CO2 emission (FCO2) in agricultural areas results from the interaction of different factors such as climate and soil conditions. Our objective was to investigate the spatiotemporal variation of FCO2, temperature (Tsoil), moisture (Msoil) and air-filled pore space (AFPS), as well as their interactions, during the sugarcane field reform. The study was conducted on a 90 × 90 m sampling grid with 100 points at 10 m spacings. Ten assessments of FCO2, Tsoil and Msoil were carried out at each point over a 28-day period. The greatest mean values of FCO2 (0.74 g m−2 hr−1) and Msoil (31.7%) were obtained on Julian day 276, 2013, being associated with precipitation events at the study site. Also, the smallest values of AFPS (19.17%) and Tsoil (20.90°C) were observed on the same day. The spatial variability of FCO2, Tsoil, Msoil and AFPS was best described by an adjusted spherical model, although an exponential model better fitted some results. The spatial pattern of all soil attributes showed little temporal persistency, indicating a high complexity for FCO2 during precipitation. Correlation maps assisted in identifying regions where Msoil and AFPS better controlled the emission process and where Tsoil was important. A major challenge for world agriculture is to increase the efficiency of conventional soil management practices. We highlight the importance of the spatial pattern of soil properties that directly influence the CO2 emission dynamics. Future mitigation actions should involve less intense tillage and ensure homogeneous applications of soil inputs, thereby reducing production costs and the contribution of these activities to CO2 emissions during the sugarcane field reform. 相似文献
17.
Myroslava Khomik M. Altaf Arain J.H. McCaughey 《Agricultural and Forest Meteorology》2006,140(1-4):244
Temporal and spatial variability of soil respiration (Rs) was measured and analyzed in a 74-year-old, mixedwood, boreal forest in Ontario, Canada, over a period of 2 years (August 2003–July 2005). The ranges of Rs measured during the two study years were 0.5–6.9 μmol CO2 m−2 s−1 for 2003–2004 (Year 1) and 0.4–6.8 μmol CO2 m−2 s−1 for 2004–2005 (Year 2). Mean annual Rs for the stand was the same for both years, 2.7 μmol CO2 m−2 s−1. Temporal variability of Rs was controlled mainly by soil temperature (Ts), but soil moisture had a confounding effect on Ts. Annual estimates of total soil CO2 emissions at the site, calculated using a simple empirical Rs–Ts relationship, showed that Rs can account for about 88 ± 27% of total annual ecosystem respiration at the site. The majority of soil CO2 emissions came from the upper 12 to 20 cm organic LFH (litter–fibric–humic) soil layer. The degree of spatial variability in Rs, along the measured transect, was seasonal and followed the seasonal trend of mean Rs: increasing through the growing season and converging to a minimum in winter (coefficient of variation (CV) ranged from 4 to 74% in Year 1 and 4 to 62% in Year 2). Spatial variability in Rs was found to be negatively related to spatial variability in the C:N ratio of the LHF layer at the site. Spatial variability in Rs was also found to depend on forest tree species composition within the stand. Rs was about 15% higher in a broadleaf deciduous tree patch compared to evergreen coniferous area. However, the difference was not always significant (at 95% CI). In general, Rs in the mixedwood patch, having both deciduous and coniferous species, was dominated by broadleaf trees, reflecting changing physiological controls on Rs with seasons. Our results highlight the importance of discerning soil CO2 emissions at a variety of spatial and temporal scales. They also suggest including the LFH soil layer and allowing for seasonal variability in CO2 production within that layer, when modeling soil respiration in forest ecosystems. 相似文献
18.
农业土壤中的氧化亚氮排放: 为减排综述时空变化 总被引:3,自引:0,他引:3
This short review deals with soils as an important source of the greenhouse gas N2O. The production and consumption of N2O in soils mainly involve biotic processes: the anaerobic process of denitrification and the aerobic process of nitrification. The factors that significantly influence agricultural N2O emissions mainly concern the agricultural practices (N application rate, crop type, fertilizer type) and soil conditions (soil moisture, soil organic C content, soil pH and texture). Large variability of N2O fluxes is known to occur both at different spatial and temporal scales. Currently new techniques could help to improve the capture of the spatial variability. Continuous measurement systems with automatic chambers could also help to capture temporal variability and consequently to improve quantification of N2O emissions by soils. Some attempts for mitigating soil N2O emissions, either by modifying agricultural practices or by managing soil microbial functioning taking into account the origin of the soil N2O emission variability, are reviewed. 相似文献
19.
《Communications in Soil Science and Plant Analysis》2012,43(3-4):341-349
Abstract The extraction of a field‐moist soil with DTPA will result in a level of extractable iron (Fe) lower than that of the air‐dried soil. Soil gas‐phase carbon dioxide (CO2) levels may be considerably higher than ambient atmospheric levels, especially in wet soils in the field. This study was undertaken to determine whether gas‐phase CO2 level influences the quantity of Fe extracted by DTPA. Three moist calcareous soils were incubated for 21 days, each at three different partial pressures of CO2, after which the moist soils were extracted with DTPA. A sample of each soil was also air dried, and was subsequently extracted with DTPA. In each case, DTPA‐extractable Fe from the moist sample was lower than that from the air‐dried sample; however, DTPA‐extractable Fe increased with increasing CO2 partial pressure of in the moist soils. DTPA‐extractable Fe concentration for a given soil following air drying was not significantly influenced by the CO2 partial pressure during incubation of the originally field‐moist soil. DTPA‐extract pH of the moist soils followed the same trend as soil‐solution pH (i.e., as CO2 concentration of the soil gas‐phase increased, soil solution pH and DTPA extract pH both decreased); however, the slope of the pH versus log PCO2 curve was less pronounced in the DTPA extract due to the buffering capacity of the triethanolamine. From this study, it is concluded that elevated soil gas‐phase CO2 partial pressure does not contribute to the lower level of DTPA‐extractable Fe observed when the extraction is performed on a field‐moist versus an air‐dried soil; increased CO2 partial pressure actually resulted in a slight increase in concentration of DTPA‐extractable Fe obtained from a field‐moist soil. 相似文献
20.
Dongli She Yuanhang Fei Qian Chen Luis Carlos Timm 《Archives of Agronomy and Soil Science》2016,62(12):1625-1639
High spatial variability of soil salinity in coastal reclamation regions makes it difficult to obtain accurate scale-dependent information. The objectives of this study were to describe the spatial patterns of saline-sodic soil properties (using soil pH, electrical conductivity (EC1:5) and sodium ion content (SIC) as indicators) and to gain knowledge of the scaling relationships between those variables. The soil pH, EC1:5 and SIC data were measured at intervals of 285 m along a 13,965-m temporal transect in a coastal region of China. The spatial variability of soil pH was weak but it was strong for soil EC1:5 and SIC at the measurement scale. There was a significant positive correlation between soil EC1:5 and SIC, while correlations between soil pH and either EC1:5 or SIC were weak and negative. For each saline-sodic soil parameter, the variability changed with the decomposition scales. The high-variance area at the larger scales (≥570 m) occupied less than 10% of the total area in the local wavelet spectrum, which meant that the spatial variations of the salinity indicators were insignificant at these scales. For local wavelet coherency, at a scale of 1500–2800 m and a sampling distance of 0–4500 m, the covariance was statistically significant between any two of the saline-sodic soil parameters. 相似文献