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1.
The present study was conducted to determine the spatial heterogeneity of bulk density, soil moisture, inorganic N, microbial biomass C, and microbial biomass N in the ridge tillage system of Turiel compared to conventional mouldboard ploughing on three sampling dates in May, July, and August. The soil sampling was carried out under vegetation representing the ridge in a high spatial resolution down the soil profile. Bulk density increased with depth and ranged from 1.3 g cm−3 at 10 cm depth to 1.6 g cm−3 at 35 cm in ploughed plots and from 1.0 g m−3 at 5 cm to 1.4 g m−3 at 35 cm in the ridges. In the ploughed plots, the contents of microbial biomass C and microbial biomass N remained roughly constant at 215 and 33 μg g−1 soil, respectively, throughout the experimental period. The microbial biomass C/N ratio varied in a small range around 6.4. In the ridged plots, the contents of microbial biomass C and microbial biomass N were 5% and 6% higher compared to the ploughed plots. Highest microbial biomass C contents of roughly 300 μg g−1 soil were always measured in the crowns in July. The lowest contents of microbial biomass C of 85–137 μg g−1 soil were measured in the furrows. The ridges showed strong spatial heterogeneity in bulk density, soil water content, inorganic nitrogen and microbial biomass.  相似文献   

2.
The impact of intensive cultivation for potato production on the earthworm populations was assessed in two adjacent large field plots. Three successive winter wheat crops had been grown in one plot while winter wheat was grown with minimum cultivation in an understorey of white clover in the other. Both plots were ploughed in spring 1998 and intensively cultivated (grubbing, ridging, bed-tilling, destoning, ridging) prior to planting potatoes. Earthworm populations were reduced from a mean density of 319 individuals m–2 and 55 g m–2 biomass in the conventional wheat plot, and from 1160 individuals and 175 g m–2 biomass in the wheat–clover plot in the 1996/1997 cropping season, to 40–82 individuals and 4–19 g m–2 in June–October 1998 following potato planting. Populations declined to virtually undetectable levels following mechanical potato harvesting in late autumn 1998 and spring cultivation for barley in 1999, remained at very low levels throughout 1999 and had shown no sign of recovering by May 2000. The results show that earthworm populations can be virtually eliminated within a single season by drastic forms of soil cultivation.  相似文献   

3.
Abstract

To determine the rates of increase in C and N stocks in the soil and organic layers following afforestation in Andisols, we measured C and N densities in the organic and soil layers at depths of 0–5, 5–15 and 15–30?cm, together with a chronosequence analysis of 4-year-old, 14-year-old and 23-year-old Japanese cedar (Cryptomeria japonica) and 4-year-old, 12-year-old and 25-year-old Hinoki cypress (Chamaecyparis obtusa) plantations. The short-term changes in C and N were confirmed by repeated sampling 5?years after the first sampling. Tree growth, biomass accumulation and organic layers were much greater in Japanese cedar than in Hinoki cypress plantations. Soil C density (kg?m?3) increased and bulk density decreased with stand age in the surface layer (0–5?cm). The average soil C accumulation rate was 22.9?g?C?m?2?year?1 for Japanese cedar and 21.1?g?C?m?2?year?1 for Hinoki cypress. Repeated sampling showed that the rate of increase in C in the surface soil was relatively slow in young stands and that soil C density (kg?m?3) in the subsurface soil did not change over a 5-year period. Although N accumulated in the tree biomass and organic layers, the soil N density (kg?m?3) did not change after afforestation. Although the andic properties of the soil and differences in the planted species did not influence the rate of increase in soil C, soil C density was expected to increase to a concentration greater than 80?g?kg?1, possibly because of the large C accumulation capacity of Andisols.  相似文献   

4.
Nitric oxide (NO) plays a central role in the formation of tropospheric ozone, hydroxyl radicals, as well as nitrous and nitric acids. There are, however, large uncertainties around estimates of global NO emissions due to the paucity of data. In particular, there is little information on the rate of NO emission and its sensitivity to processes such as land use changes in dry environments. Here we report on a two-year study on the influence of afforestation on soil NO fluxes in the semi-arid afforestation system in Southern Israel (Yatir forest, mean annual precipitation ∼280 mm). Laboratory incubations were carried out under seasonally defined conditions of soil moisture and temperature using soils sampled in different seasons from the native shrubland (taken both under shrub canopy and in the inter-shrub areas), and from the adjacent ∼2800 ha, 40-year-old pine afforestation site. Combining laboratory results with field measurements of soil moisture and temperature, we up-scaled soil-atmosphere NO fluxes to the ecosystem level. The different microsites differed in their annual mean NO release rates (0.04, 0.14 and 0.03 mg m−2 d−1 for the shrubland under and between shrubs and for the forest, respectively), and exhibited high inter-seasonal variability in NO emission rates (ranging from zero up to 0.25 mg m−2 d−1 in the wet and dry-rewetting seasons, respectively), as well as in temperature responses. Up-scaling results to annual and ecosystem scales indicated that afforestation of the semi-arid shrubland could reduce soil NO emission by up to 65%.  相似文献   

5.
Enchytraeidae were studied at spruce forest sites (Harz, Germany) differing in their exposure and soil acidity affected by acid deposition. Total density ranged between 38 000 and 59 000 ind. m–2 and biomass between 0.5 and 1 g m–2 d.m. (annual means). Of the seven species recorded, Cognettia sphagnetorum, Marionina clavata, and Achaeta camerani were dominant. The site affected most by acidification had the highest densities and lowest species number. Population dynamics and vertical distributions were affected by climate. Field and laboratory data provide evidence for sexual reproduction in C. sphagnetorum. Substrate preference experiments showed this species to prefer spruce litter from the OL-Horizon to that from the OH-Horizon, and spruce litter to beech litter.  相似文献   

6.
We investigated how earthworm communities of agricultural systems vary in abundance, biomass and species composition at different spatial scales. In four farms representative of the main agro-ecological regions of Belgium 14 parcels were sampled using a combined method (hand sorting after formalin extraction). Parcels in both grassland and arable land were studied. In each parcel two or three sample plots (1 m2) were randomly selected; these were further split up in two, resulting in four or six 0.5 m2 subplots per parcel. Principal component analysis was applied to earthworm numbers and biomass. Innovative was that we compared the results from data matrices with raw data with prorated matrices, where unidentified juveniles were added to species following certain rules. To test the degree of variability between the different spatial levels, average distances between subplots, plots and parcels based on ordination scores were compared. A general linear model with a nested structure for subplots, plots, and parcels was built to find absolute differences between farms. Earthworm numbers ranged from 10 to 463 individuals m–2, biomass varied between 3 and 186 g m–2 and species numbers ranged from one to seven per parcel. Ordinations separated earthworm communities along a geographical—mainly soil—gradient on the first axis and distinguished between land uses along the second axis. Both in numbers of individuals and in biomass differences in earthworm populations increased from subplot to parcel level. As expected, differences within a pair of subplots were small. Plots within the same parcel tended to be highly similar, but in some cases large dissimilarities were encountered, reflecting a clustered population structure of earthworm communities at the field scale, and, possibly, abiotic gradients. The largest differences were observed at the parcel level. The latter may be attributed to differences in land use. Prorating had a narrowing effect on the data through which differences became less pronounced.  相似文献   

7.
The stock and stability of soil organic carbon (SOC) are critical to soil functions and global carbon cycle, but little quantitative information is available on the precise location and chemical components of SOC for soils across a wide range of climatic gradients. Here, a broad range of zonal soils were collected in forest land at topsoil (0–15 cm) and subsoil (15–30 cm) from temperate to tropical climatic gradient in central to south China. The stock and stability of SOC were determined in terms of aggregate and humic fractionation. SOC in bulk soils with a less significant geographic variation was comparably higher at Haplic Luvisoils in temperate regions (3637.61 g m−2) and Rhodi-Humic Ferrosols in tropical regions (3446.12 g m−2) than in the other experimental soils, but a consistent decreasing trend was observed along the soil profiles with the SOC stock was 1.11–1.97 times higher in the topsoil than in the subsoils. In addition, insoluble humin residue (HMr) as the dominant components of SOC ranged from 643.95 to 2696.90 g m−2 and decreased from temperate to tropical regions, which was consistent with the zonal variation of humic acids (HAs), but contrary to the zonal variation of fulvic acids (FAs) that fluctuated in a range of 39.67–389.55 g m−2 across the experimental sites. According to the results of partial correlation analysis, the variation of FAs stock was significantly attributed to soil pH, bulk density, iron and aluminum oxides, clay, and clay mineral content (|r|>0.61, p < 0.05), while these soil physical properties showed a contradictory effects on HAs, iron-linked humin (HMi), clay-combined humin (HMc), and HMr. Moreover, the aggregate-associated carbon stock was mainly stored in macroaggregates (36.34–76.09%) for both SOC and its chemical components, especially in topsoils, and its zonal variation was associated with that of bulk soils. In general, the redundancy analysis (RDA) revealed that mean annual precipitation (MAP) accounted for 81.8% and 13.8% of the variance in SOC chemical and physical fractionation, respectively, while the corresponding contribution of mean annual temperature (MAT) was 1.5% and 34.7%. With the increase of MAT and MAP, the chemical stability of SOC decreased in the molecular structure, and the physical protection of SOC by aggregate exhibited a unimodal trend. The obtained results would facilitate the development of regional soil carbon prediction and land management against global warming.  相似文献   

8.
A study was conducted in a Setaria italica (L.) Beauv. cropland on the Loess Plateau in order to partition total soil respiration (Rt) into microbial respiration (Rm) and root respiration (Rr) and to determine the carbon balance of the cropland ecosystem. A trenching method with micro-pore mesh was used to create root-free soil cores. Differences between mesh and non-mesh treatments were used to determine root respiration. Similar pattern was found in the diurnal variation of Rt and Rm with the minimum values at 3:00-6:00 h and the maximum at 13:00-15:00 h. The diurnal pattern of Rr was completely different, the minimum values appeared at 11:00-13:00 h and the maximum at 0:00-3:00 h. Soil temperature exerted predominant control over the diurnal variations of Rt and Rm. The daily mean values of Rt, Rm and Rr were close to the measurements taken at 9:00 h. On the seasonal scale, Rm was strongly dependent on soil temperature, with higher correlation with 2-cm-depth temperature (r2 = 0.79, P < 0.001) than with 5-cm-depth temperature. When the effects of both soil temperature and moisture were considered, a linear model provided more accurate prediction of Rm (r2 = 0.83, P < 0.0001). Root respiration (Rr) exhibited pronounced daily variation corresponding to changes in photosynthesis and seasonal variation related to crop phenological development. The seasonal variation in Rr was strongly correlated with leaf area index (LAI) (r2 = 0.85, P < 0.05), and also positively, but marginally correlated with root biomass (RB, P = 0.073). Contribution of root respiration to total soil respiration (Rr/Rt ratio) showed pronounced diurnal and seasonal variations. The daily mean values of Rr/Rt ratios were close to the values obtained at 9:00 h. In different phenological stages, Rr/Rt ratios ranged from 22.3% to 86.6%; over the entire growing season, the mean Rr/Rt ratio was 67.3%.Total annual loss of C due to Rm in 2007 was estimated to be 121.3 g C m−2 at the study site, while the annual NPP (net primary production) was 262.1 g C m−2. The cropland system thus showed net carbon input of 140.8 g C m−2.  相似文献   

9.
Many studies have shown that changes in nitrogen (N) availability affect the diversity and composition of soil microbial community in a variety of terrestrial systems, but less is known about the responses of microbes specific to biological soil crusts (BSCs) to increasing N additions. After seven years of field experiment, the bacterial diversity in lichen-dominated crusts decreased linearly with increasing inorganic N additions (ambient N deposition; low N addition, 3.5 g N m−2 y−1; medium N addition, 7.0 g N m−2 y−1; high N addition, 14.0 g N m−2 y−1), whereas the fungal diversity exhibited a distinctive pattern, with the low N-added crust containing a higher diversity than the other crusts. Pyrosequencing data revealed that the bacterial community shifted to more Cyanobacteria with modest N additions (low N and medium N) and to more Actinobacteria and Proteobacteria and much less Cyanobacteria with excess N addition (high N). Our results suggest that soil pH, together with soil organic carbon (C), structures the bacterial communities with N additions. Among the fungal communities, the relative abundance of Ascomycota increased with modest N but decreased with excess N. However, increasing N additions favored Basidiomycota, which may be ascribed to increases in substrate availability with low lignin and high cellulose contents under elevated N conditions. Bacteria/fungi ratios were higher in the N-added samples than in the control, suggesting that the bacterial biomass tends to dominate over that of fungi in lichen-dominated crusts after N additions, which is especially evident in the excess N condition. Because bacteria and fungi are important components and important decomposers in BSCs, the alterations of the bacterial and fungal communities may have implications in the formation and persistence of BSCs and the cycling and storage of C in desert ecosystems.  相似文献   

10.
Earlier studies of postmining heaps near Sokolov, Czech Republic (0–46 years old) showed that massive changes in plant community composition occur around 23 year of succession when the heaps are colonized by the earthworms Lumbricus rubellus (Hoffm.) and Aporrectodea caliginosa (Savigny). The aim of the current study was to test the hypothesis that the introduction of earthworms into a postmining soil enhances growth of late succession plant species. In a laboratory experiment, earthworms significantly increased biomass of Festuca rubra and Trifolium hybridum grown in soil from a 17-year-old site. The biomass increase corresponded to a significant decrease in pH and an increase in oxidable C, total N, and exchangeable P, K, and Ca content. A second laboratory experiment showed higher biomass production of late successional plant community (Arrhenatherum elatius, Agrostis capillaris, Centaurea jacea, Plantago lanceolata, Lotus corniculatus, and Trifolium medium) in soil from late successional stage (46 years old); the introduction of earthworms into soil from an early successional stage (17 years old) increased biomass production. In a field experiment, introduction of L. rubellus to enclosures containing a 17-year-old soil not colonized by earthworms significantly increased the biomass of grasses after 1 year. The results support the hypothesis that colonization of postmining areas by earthworms can substantially modify soil properties and plant growth.  相似文献   

11.
《Applied soil ecology》2001,16(1):23-34
The succession of soil nematodes from initial planting with Pinus sylvestris seedling to about 30-year-old pine plantations on coal mining sands in the Lusatian lignite-mining district near Cottbus (Germany) was studied and compared with the nematode fauna of a 40-year-old semi-natural pine forest on naturally formed sandy soil. The initial stage was primarily characterised by a very low abundance (20×103 individuals/m2), which increased over a period of two years to values common in older pine plantations (500–600×103 individuals/m2). In the semi-natural forest the mean abundance of nematodes was about 1300×103 individuals/m2. Populations of Tardigrada, Rotifera and Enchytraeidae also increased with stand age. Nematode biomass increased from 49 to 543 mg m−2 in pine plantations and slightly decreased in the semi-natural forest to 301 mg m−2 over the period of investigation. The early colonisation of the initial stage was by bacterivorous (Acrobeloides) and fungal feeding (Aphelenchoides) nematodes, but the communities diversified as succession progressed with bacterivorous nematodes of the genera Plectus, Wilsonema and Metateratocephalus, root-fungal feeding Filenchus, omnivorous Aporcelaimellus and Eudorylaimus, and predacious Prionchulus becoming abundant. The abundance of plant-parasitic nematodes was very low. The greatest number of nematode genera was found in the semi-natural forest.  相似文献   

12.
Net ecosystem carbon dioxide exchange was measured in two contrasting peatlands in northern Alberta, Canada using the eddy covariance technique during the growing season (May–October). Sphagnum spp. made up approximately 66% of the total LAI (1.52 m2 m−2) at the poor fen and the total N content of Sphagnum capitula was 7.8 mg g−1 at the peak of the growing season. In contrast, the dominant plant species at the extreme-rich fen site, the perennial sedge, Carex lasiocarpa, accounted for approximately 60% of the total LAI (1.09 m2 m−2), and had leaf total N content of 19.3 mg g−1 at peak biomass. In addition, the peak aboveground biomass was higher at the poor fen (230.9 g m−2) than at the extreme-rich fen (157.1 g m−2). Both sites had maximum daily rates of net CO2 uptake of approximately 5 μmol m−2 s−1, and typical nighttime rates of CO2 loss of approximately 2 μmol m−2 s−1 during the peak of the growing season. Calculations of maximum photosynthetic and respiratory capacity were consistently higher at the extreme-rich fen. The poor fen was a net sink for CO2 during 4 of the 6 months (peaking at 44 g C m−2 in July), while only slight net losses of CO2 (3 g C m−2) occurred in May and September. In contrast, the extreme-rich fen was calculated to be a significant net sink for CO2 only during 2 months of the growing season (peaking at 30 g C m−2 in August), while significant net losses of CO2 occurred in May (8 g C m−2) and in October (13 g C m−2). The plant species at the poor fen site were active earlier and later in the growing season, while it took longer for C. lasiocarpa to develop leaf tissue, and leaf senescence and reduction in photosynthetic activity occurred earlier in the fall at the extreme-rich fen. When integrated over the 6-month growing season, the poor fen was a net sink (90 g C m−2) that was three times larger than the extreme-rich fen (31 g C m−2). The ratio of cumulative total ecosystem respiration to gross primary production was 0.7 at the poor fen and 0.9 at the extreme-rich fen.  相似文献   

13.
Performance of three exotic species of Leucaena (L. diversifolia, L. shannonii and L. leucocephala) and one local selection of L. leucocephala was evaluated on sodic soil sites (pH 8.6–10.5) in order to select promising species for biomass production and reclamation of these soils. There were significant differences among three species with respect to their field survival (47.7–95.5 per cent), growth in terms of stem volume (40.8–118.6 m3 ha−1) and biomass production (24–70 Mg ha−1) after eight years of growth. L. leucocephala was rated as the most promising species irrespective of seed source, followed by L. shannonii. L. diversifolia could not perform well on these hostile soils. A definite improvement in physicochemical properties of soil particularly in surface layers (0–5 cm) was observed after eight years of plantations as compared to the same at uncultivated site. The soil pH and sodium content decreased followed by an increase in organic carbon, nitrogen and phosphorus content. However, efficiency of different species varied greatly to ameliorate these soils depending on quantity and quality of organic matter lying on the floor. L. leucocephala, irrespective of seed origin, showed greater promise for afforestation of sodic soils because of its potential to produce higher biomass per unit area and greater efficiency to ameliorate fertility status of these soils. The study revealed that matching of species to soil conditions is very important for a successful plantation programme and sustainable development of degraded soil sites. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

14.
Identifying the patterns of soil microbial responses to increasing nitrogen (N) availability are important since microbial processes are related to the potential nutrient transformations. The effects of the addition of N to the soil microbial community of the Gurbantunggut Desert, China, are described in this paper. The study was conducted over a two-year period with trials commencing at the beginning of each growing season. Soil enzyme activity, microbial biomass and microbial community level physiological profile (CLPP) were determined at 0–5 cm and 5–10 cm soil depths. Nitrogen was added to the soil at five rates plus a control, i.e. 0, 0.5, 1, 3, 6 and 24 g N m−2 y−1. We hypothesized that soil enzyme activities and microbial biomass N (MBN) would firstly increase and then decrease, and CLPP would be altered with increasing N addition, due to the deleterious effects of higher N addition upon microbial activity. Because of the relatively higher organic matter in the upper depth of soil layers, we further hypothesized that the responses of microbial activities in the 0–5 cm depth would be more marked than at 5–10 cm. In partial support of our hypothesis, soil enzyme activities, microbial biomass and nutrient concentrations responded to N addition with the most significant changes occurring in the 0–5 cm soil depth. Addition of N resulted in an increase in MBN and a decrease in urease activity. Invertase and alkaline phosphatase (AlP) activities increased at low doses of N addition and showed a decrease at higher doses. There was no evidence of change in oxidative enzyme activity at low N treatments but activity decreased at high N additions. However, the CLPP was not affected by N addition. The results of this study suggest that N supplementation in this desert soil may affect C transformation, increase availability of N and P, and immobilize N in the microbial biomass. Responses of the enzyme activity to N supplementation occurred within the context of an apparently stable or unresponsive microbial community structure.  相似文献   

15.
Plot trenching and root decomposition experiments were conducted in a warm-temperate oak chronosequence (40-year-old, 48-year-old, 80-year-old, and 143-year-old) in China. We partitioned total soil surface CO2 efflux (RS) into heterotrophic (RH) and rhizospheric (RR) components across the growing season of 2009. We found that the temporal variation of RR and RH can be well explained by soil temperature (T5) at 5 cm depth using exponential equations for all forests. However, RR of 40-year-old and 48-year-old forests peaked in September, while their T5 peaks occurred in August. RR of 80-year-old and 143-year-old forests showed a similar pattern to T5. The contribution of RR to RS (RC) of 40-year-old and 48-year-old forests presented a second peak in September. Seasonal variation of RR may be accounted for by the different successional stages. Cumulative RH and RR during the growing season varied with forest age. The estimated RH values for 40-year-old, 48-year-old, 80-year-old and 143-year-old forests averaged 431.72, 452.02, 484.62 and 678.93 g C m−2, respectively, while the corresponding values of RR averaged 191.94, 206.51, 321.13 and 153.03 g C m−2. The estimated RC increased from 30.78% in the 40-year-old forest to 39.85% in the 80-year-old forest and then declined to 18.39% in the 143-year-old forest. We found soil organic carbon (SOC), especially the light fraction organic carbon (LFOC), stock at 0-10 cm soil depth correlated well with RH. There was no significant relationship between RR and fine root biomass regardless of stand age. Measured apparent temperature sensitivity (Q10) of RH (3.93 ± 0.27) was significantly higher than that of RR (2.78 ± 0.73). Capillary porosity decreased as stand age increased and it was negatively correlated to cumulative RS. Our results emphasize the importance of partitioning soil respiration in evaluating the stand age effect on soil respiration and its significance to future model construction.  相似文献   

16.
Carbon dioxide, water vapour and energy fluxes were measured above and within a maritime pine forest during an atypical year with long-lasting reduced soil water availability. Energy balance closure was adequately good at both levels. As compared with what is usually observed at this site the ecosystem dissipated less energy via latent heat flux and more via sensible heat flux. The understorey canopy was responsible for a variable, significant component of the whole canopy fluxes of water vapour and carbon dioxide. The annual contribution of the understorey was 38% (154 mm) of the overall evaporation (399 mm) and 32% (89 mm) of the overall sensible heat flux (274 mm). The participation of the understorey reached 45% of the overall evaporation and 30% of the daytime overall assimilation during significant soil water deficit periods in summertime. Even during winter, understorey photosynthesis was consistent as it compensated soil and understorey respiration. The ecosystem behaved as a sink of carbon, with a negative annual carbon budget (−57 g C m−2). However, due to high soil water deficit, the annual ecosystem GPP was 40% less than usually observed at this site. This budget resulted from a sink of −131 g C m−2 for the overstorey and a source of +74 g C m−2 for the understorey. Moreover, on an annual basis the overstorey layer contributed to almost two-thirds of the ecosystem respiration. Finally, the effect of long-lasting soil water deficit on the maritime pine forest was found more important than the effect of the heat wave and drought of summer 2003.  相似文献   

17.
Brown-coal opencast mining provides a virgin soil substratum at a scale of square kilometres that is open to primary succession. Focusing on this process, we investigated changes in collembolan species composition in a long-term study that lasted almost 40 years (1960–1998) at mine sites, afforested with deciduous trees. The geological overburden, which characterises the soil quality, consisted mainly of Pleistocene and Tertiary sands, interspersed with lignite and dark Tertiary loam and clay.

According to their appearance during the primary succession, we established eight colonising groups, representing 90 of 113 species found. Results from soil samples as well as from pitfall traps were taken into account for the definition of the groups. Thus, edaphic and epedaphic life forms were equally regarded. Generally, “initial”, “pioneer” and “woodland” groups were discernible.

Largest changes in species composition occurred during the first ten years, as indicated by decreasing species turnover rates and increasing alpha diversity. A comparison with other (essentially shorter) studies on Collembola of mine sites (12 in Europe, 3 in other parts of the world) showed that some pioneer species are cosmopolitan whilst others seem to be regionally specific. Important events in the ecosystem development of mine sites, as indicated by the collembolan community, are the first occurrence of other humiphagous soil animal groups, especially that of earthworms, followed by a disappearance of the ectohumus layer. The similarity between collembolan communities of mine sites and of adjacent native woodlands is greatest ten years after afforestation. Fifty years after afforestation, the collembolan community still differed markedly from that of native stands. Thus, a gradual development of the mine site collembolan communities to a comparable native woodland community is not evident from the data.  相似文献   


18.
Cai  Zejiang  Xu  Minggang  Zhang  Lu  Yang  Yadong  Wang  Boren  Wen  Shilin  Misselbrook  Tom H.  Carswell  Alison M.  Duan  Yinghua  Gao  Suduan 《Journal of Soils and Sediments》2020,20(8):3124-3135
Purpose

Decarboxylation of organic anions in crop straw is recognized as one of the mechanisms for increasing pH in acidified soils. However, the effectiveness of specific compounds in alleviating soil acidification from nitrification has not been well determined. This study examined three organic anions commonly found in crop straws and their effect on soil acidity and N transformation processes following urea application to a red soil (Ferralic Cambisol).

Materials and methods

A 35-day incubation experiment was conducted using soil after receiving 26 years of two different nutrient treatments: (1) chemical nitrogen, phosphorus, and potassium fertilization (NPK, pH 4.30) and (2) NPK plus swine manure (NPKM, pH 5.88). Treatments included three rates (0.25, 0.5, and 1.0 g C kg?1) of calcium citrate, 0.5 g C kg?1 calcium oxalate, 0.5 g C kg?1 calcium malate, urea-only (control) soil, and a non-treated soil as a reference. Soil acidity, mineral N species, decarboxylation, and their correlations were determined.

Results and discussion

All three organic anions significantly increased pH in both soils and the effectiveness was positively correlated with application rate. The change in total exchangeable soil acidity was dominated by aluminum concentration in the NPK soil, but by proton concentration in the NPKM soil. At ≥?0.5 g C kg?1, the anions decreased soil exchangeable acidity by 25–68% in NPK soil and by 63–88% in NPKM soil as compared with control. Oxalate was the most effective in increasing soil pH by 0.70 and 1.31 units and reducing exchangeable acidity by 3.79 and 0.33 cmol(+) kg?1 in NPK and NPKM soils, respectively, and also resulted in the highest CO2 production rate. Addition of organic anions led to a lower nitrification rate in NPKM soil relative to the NPK soil.

Conclusions

These results imply that crop straws rich in organic anions, especially oxalate, would have a higher potential to alleviate soil acidification.

  相似文献   

19.
《Applied soil ecology》2011,47(3):355-371
Secondary succession of nematodes was studied in 1–48-year-old abandoned fields on cambisols in South Bohemia, Czech Republic, and compared with cultivated field and sub-climax oak forests. Bacterivores were the predominant group in the cultivated field whereas in forests root-fungal feeders (mainly Filenchus) were almost as abundant as bacterivores. The total abundance of nematodes in the cultivated field averaged 868 × 103 ind m−2. During the first three years of succession the abundance practically did not change (775 × 103 ind m−2), the fauna was still similar to that in cultivated field but the biomass increased mainly due to Aporcelaimellus. Then the abundance increased up to 3731 × 103 ind m−2 in 7–8-year-old abandoned fields, plant parasites (Helicotylenchus) dominated and the fungal-based decomposition channel was activated. Later the abundance stabilised at between 1086 and 1478 × 103 ind m−2 in 13–25-year-old successional meadow stages with high population densities of omnivores and predators. The total abundance of nematodes was low in the 12–13-year-old willow shrub stage (594 × 103 ind m−2), increased in the 35–48-year-old birch shrub stage (1760 × 103 ind m−2) and the nematode fauna developed towards a forest community. The diversity and maturity of nematode communities generally increased with the age of abandoned fields but the highest values were in meadow stages (81–113 species, 57–68 genera, MI 2.73–3.30). The development of meadow arrested succession towards forests or diverted succession towards a waterlogged ecosystem. The succession of nematodes was influenced by the method of field abandonment (bare soil vs. legume cover, mowing) that affected the formation of either a shrub or meadow stage, and by the soil water status. The composition of the nematode fauna indicated that the soil food web could recover faster from agricultural disturbance under successive meadows than under shrubs.  相似文献   

20.
Reduction of nitrous oxide (N2O) to dinitrogen (N2) by denitrification in soils is of outstanding ecological significance since it is the prevailing natural process converting reactive nitrogen back into inert molecular dinitrogen. Furthermore, the extent to which N2O is reduced to N2 via denitrification is a major regulating factor affecting the magnitude of N2O emission from soils. However, due to methodological problems in the past, extremely little information is available on N2 emission and the N2:N2O emission ratio for soils of terrestrial ecosystems. In this study, we simultaneously determined N2 and N2O emissions from intact soil cores taken from a mountainous beech forest ecosystem. The soil cores were taken from plots with distinct differences in microclimate (warm-dry versus cool-moist) and silvicultural treatment (untreated control versus heavy thinning). Due to different microclimates, the plots showed pronounced differences in pH values (range: 6.3–7.3). N2O emission from the soil cores was generally very low (2.0 ± 0.5–6.3 ± 3.8 μg N m−2 h−1 at the warm-dry site and 7.1 ± 3.1–57.4 ± 28.5 μg N m−2 h−1 at the cool-moist site), thus confirming results from field measurements. However, N2 emission exceeded N2O emission by a factor of 21 ± 6–220 ± 122 at the investigated plots. This illustrates that the dominant end product of denitrification at our plots and under the given environmental conditions is N2 rather than N2O. N2 emission showed a huge variability (range: 161 ± 64–1070 ± 499 μg N m−2 h−1), so that potential effects of microclimate or silvicultural treatment on N2 emission could not be identified with certainty. However, there was a significant effect of microclimate on the magnitude of N2O emission as well as on the mean N2:N2O emission ratio. N2:N2O emission ratios were higher and N2O emissions were lower for soil cores taken from the plots with warm-dry microclimate as compared to soil cores taken from the cool-moist microclimate plots. We hypothesize that the increase in the N2:N2O emission ratio at the warm-dry site was due to higher N2O reductase activity provoked by the higher soil pH value of this site. Overall, the results of this study show that the N2:N2O emission ratio is crucial for understanding the regulation of N2O fluxes of the investigated soil and that reliable estimates of N2 emissions are an indispensable prerequisite for accurately calculating total N gas budgets for the investigated ecosystem and very likely for many other terrestrial upland ecosystems as well.  相似文献   

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