Abundance and depth stratification of soil arthropods as influenced by tillage regimes in a sandy loam soil

Different tillage regimes can change soil micro‐environmental characteristics, which may influence the distribution and abundance of soil arthropods. In this study, soil arthropods and soil properties under a winter wheat–summer maize cropping system were investigated in different tillage regimes over four seasons at two depths. The tillage treatments included conventional tillage (CT ), tillage once a year (T1), tillage every two years (T2) and no‐tillage (NT ). The results showed that the primary taxa of soil arthropod were Acarina (65.8%), Collembola (28.5%), Diplura (1.4%) and Coleoptera (1%) over the whole sampling period. The total arthropod density was influenced by tillage treatments and season of sampling. Values for CT plots were significantly greater than those for the NT plots in autumn and spring. In contrast, the Shannon–Wiener diversity index (H’) and the evenness index (J) were relatively higher in CT treatment. The Acarina/Collembola (A/C) ratio was significantly smaller in NT treatment for some sampling seasons as mites were more sensitive to tillage practices. The QBS ‐ar index did not show a clear pattern among treatments in this study. Soil arthropods notably showed seasonal variation in depth stratification. Relative to CT , the total soil arthropods in the NT plots tended to concentrate in the upper layer due to soil compaction in the lower layer. The climate conditions and soil physical properties were the main factors affecting the soil arthropod distribution and composition, as the soil chemical and microbial properties did not differ significantly among all tillage treatments.     

The effect of land management practices on soil erosion and land desertification in an olive grove

The need for reliable estimates of soil loss under different land management practices (LMPs) is becoming imperative in the Mediterranean basin to inform decisions on more effective strategies for land management. The effect of LMPs on soil erosion and land degradation has been investigated using experiments from November 2008 to November 2011 in an olive grove in central Crete (Greece). The study area was on sloping land with soils formed on marl deposits which are vulnerable to desertification because of surface runoff and tillage. The experimental design included three treatments with two replicates (3 × 5 m experimental plots) corresponding to the following LMPs: (i) no tillage–no herbicide application, (ii) no tillage–herbicide application and (iii) ploughing to 20 cm perpendicular to the contours. The following variables were monitored: surface water runoff, sediment loss, soil temperature at 10 cm, soil moisture content at depths of 20 and 50 cm, as well as selected climatic variables. The results show that the no tillage–no herbicide management practice gave the lowest sediment loss (1.44–4.78 g/m²/yr), the lowest water runoff (1.8–11.5 mm/yr), the greatest amount of water stored in the soil, the lowest soil temperature and the lowest desertification risk compared with the other treatments. Tillage resulted in the greatest sediment loss (13.6–39.2 g/m²/yr) and surface runoff (16.5–65.0 mm/yr), and an intermediate amount of water stored in the soil. In addition, this treatment led to the loss of soil thickness of 3.7 mm/yr because of ploughing. The results demonstrate the high risk of desertification in the investigated region and the methodology can be used in other Mediterranean areas as an assessment framework for evaluating land degradation and the impact of land management on soil erosion.     

Experimental assessment of runoff and soil erosion in an olive grove on a Vertic soil in southern Spain as affected by soil management

Abstract. Three different management systems were compared in an olive grove on a Vertic soil, near the city of Cordoba, Spain. Rainfall, runoff and soil loss were recorded from experimental plots of 6×12 m for three years. Results indicated that the no-tillage system, which was kept weed-free with herbicides, gave the largest soil loss (8.5 t ha⁻¹ yr⁻¹) and average annual runoff coefficient (21.5%), due to increased soil compaction, particularly outside the canopy projection area. A system that used a grass cover gave the lowest soil losses (1.2 t ha⁻¹ yr⁻¹) and average annual runoff coefficient (2.5%) due to the protective effects of the cover and increased soil aggregate stability. The third system, conventional tillage, gave intermediate results, with a soil loss of 4.0 t ha⁻¹ yr⁻¹ and an average runoff coefficient of 7.4%. The search for alternative soil management to conventional tillage should consider occasional light tillage to establish a grass cover that would keep both soil erosion and runoff losses to a minimum.     

Simulation of soil organic carbon stocks in a Mediterranean olive grove under different soil-management systems using the RothC model

Agricultural soils play a very important role in regulating the carbon dioxide (CO₂) content of the atmosphere, and can behave either as carbon sources or sinks. We have simulated the dynamics of carbon in the soil under different land uses and soil-management systems in a Mediterranean olive grove with the Rothamsted carbon (RothC) model. To this end we chose patches of native vegetation (NV) and two different olive grove soils (chromic calcisols and calcic vertisols) under different soil-management systems: conventional tillage (T), and mulching with shredded olive-pruning debris and residues from olive-fruit cleaning (PD + CR). We measured the clay content, bulk density, soil organic carbon (SOC) and total nitrogen (N) in each patch. The SOC and N values decreased by more than 30% as a result of a change in soil use from NV to T olive grove. After adding PD + CR these values rose once more, even to levels above NV. The RothC model performed well for covered soils (NV and PD + CR) but overestimated the SOC values after the soil use was changed from NV to T olive grove, probably due to high carbon losses caused by erosion, common to T soils in the Mediterranean basin. As a result of mulching the soil with only pruning debris, CO₂ emitted to the atmosphere was reduced by >55% for both soils. Associated with this decrease in the emission rate, RothC estimated a potential carbon sequestration of 0.5 and 0.6 t C/ha/yr for chromic calcisols and calcic vertisols, respectively. The reuse of organic debris generated in the olive grove, such as pruning debris and residues from olive-fruit cleaning, is an efficient way of improving soil properties, diminishing CO₂ emissions and increasing the soil’s capacity to store carbon.     

华北潮土区不同耕作方式下土壤动物丰富度与多样性

在黄淮海平原小麦-玉米一年两熟地区,试验设置了5个处理,分别为玉米小麦每年均翻耕(CTWT)、玉米免耕+小麦每年翻耕(CNTWT)、玉米免耕+小麦每2年翻耕(CNTW2T)、玉米免耕+小麦每4年翻耕(CNTW4T)、玉米小麦每年均免耕(CNTWNT),所有处理的农作物地上秸秆全部移出。调查结果显示,中小型土壤动物在数量上占总数的比例为83%～91%,土壤动物主要分布在表层,占有其总量的71.9%～73.2%。土壤动物存在显著的季节性动态,其丰富度在玉米季高于小麦季。土壤动物Shannon多样性指数在整体上表现为翻耕高于免耕处理,玉米季翻耕处理下有更高的均匀度指数,但小麦季均匀度指数差异不显著。多元典范冗余分析表明,耕作方式主要是对土壤动物的时间动态和垂直分布产生影响,从而间接地影响了土壤动物的数量和组成。     

A study of spatial variability of soil loss with high resolution DEMs: A case study of a sloping olive grove in southern Spain

Land degradation worldwide over several centuries has become a serious problem. This phenomenon has been accentuated in agricultural areas, where the amount of topsoil loss creates a gradual loss of farmland productivity. Ploughing is responsible for tillage erosion which causes more soil movement than natural soil creepage. In fact sediment transport is more rapid using heavy machinery than with primitive ploughs. The main aim of our research is to monitor, in detail, the sediment deposition phenomenon of eroded soil. Here the role of high resolution DEMs is essential. We develop a DEM generated from field measurements taken by GPS. The high spatial density of these measurements allows us to generate DEMs of high resolution: cell sizes of 0.5, 1 and 1.5 m. Three zones of different area are used in order to analyse the scale effects. In this study we assess precise models that represent a soil redistribution phenomenon.     

Efficiency of acetylene reduction (nitrogen fixation) in soil: Effect of type and concentration of available carbohydrate

Sandy loam field soil and Acer saccharum (maple) forest soil were amended with different concentrations of glucose and mannitol and incubated at different pO₂ levels. Nitrogenase activity was determined by repeated 1-h C₂H₂ reduction assays performed at the ambient pO₂ of incubation. Calculated efficiencies of N₂ fixation increased with increasing anaerobiosis and with decreasing added carbohydrate concentration. Efficiencies up to 30 mg N₂ fixed per gram of glucose consumed were obtained under anaerobic conditions in the presence of 0.25% (w/w) glucose. Evidence suggested that low aerobic efficiencies were caused by intense competition for carbohydrate and by lower pH values attained. High concentrations (up to 3.0% w/w) of glucose under aerobic conditions suppressed the development of N₂ase activity. Mannitol supported N₂ase activity the development of which was very much delayed under aerobic conditions but little delayed under anaerobic conditions.     

Abundance,diversity and connectance of soil food web channels along environmental gradients in an agricultural landscape

Soil food webs respond to anthropogenic and natural environmental variables and gradients. We studied abundance, connectance (a measure of the trophic interactions within each channel), and diversity in three different channels of the soil food web, each comprised of a resource-consumer pair: the microbivore channel (microbes and their nematode grazers), the plant–herbivore channel (plants and plant-feeding nematodes), and the predator–prey channel (predatory nematodes and their nematode prey), and their associations with different gradients in a heterogeneous agricultural landscape that consisted of intensive row crop agriculture and grazed non-irrigated grasslands in central California. Samples were taken at three positions in relation to water channels: water’s edge, bench above waterway, and the adjacent arable or grazed field. Nematode communities, phospholipid fatty acid (PLFA) biomarkers, and soil properties (NH₄⁺-N, NO₃⁻-N, total N, total C, pH, P, bulk density and soil texture) were measured, and riparian health ratings were scored. Environmental variables were obtained from publicly-available data sources (slope, elevation, available water capacity, erodability, hydraulic conductivity, exchangeable cation capacity, organic matter, clay and sand content and pH).The abundance and richness in most food web components were higher in grazed grasslands than in intensive agricultural fields. Consumers contributed less than their resources to the abundance and richness of the community in all channels. The association between richness and abundance for each component was strongest for the lowest trophic links (microbes, as inferred by PLFA) and weakest for the highest (predatory nematodes). The trophic interactions for the predator–prey and plant–herbivore channels were greater in the grassland than in the cropland. Fields for crops or grazing supported more interactions than the water’s edge in the plant–herbivore and microbivore channels. Connectance increased with the total richness of each community. Higher connectance within the microbivore and predator–prey soil food web channels were associated with soil NO₃⁻-N and elevation respectively, which served as surrogate indicators of high and low agricultural intensification.     

Abundance, diversity and connectance of soil food web channels along environmental gradients in an agricultural landscape

Soil food webs respond to anthropogenic and natural environmental variables and gradients. We studied abundance, connectance (a measure of the trophic interactions within each channel), and diversity in three different channels of the soil food web, each comprised of a resource-consumer pair: the microbivore channel (microbes and their nematode grazers), the plant–herbivore channel (plants and plant-feeding nematodes), and the predator–prey channel (predatory nematodes and their nematode prey), and their associations with different gradients in a heterogeneous agricultural landscape that consisted of intensive row crop agriculture and grazed non-irrigated grasslands in central California. Samples were taken at three positions in relation to water channels: water’s edge, bench above waterway, and the adjacent arable or grazed field. Nematode communities, phospholipid fatty acid (PLFA) biomarkers, and soil properties (NH₄⁺-N, NO₃⁻-N, total N, total C, pH, P, bulk density and soil texture) were measured, and riparian health ratings were scored. Environmental variables were obtained from publicly-available data sources (slope, elevation, available water capacity, erodability, hydraulic conductivity, exchangeable cation capacity, organic matter, clay and sand content and pH).The abundance and richness in most food web components were higher in grazed grasslands than in intensive agricultural fields. Consumers contributed less than their resources to the abundance and richness of the community in all channels. The association between richness and abundance for each component was strongest for the lowest trophic links (microbes, as inferred by PLFA) and weakest for the highest (predatory nematodes). The trophic interactions for the predator–prey and plant–herbivore channels were greater in the grassland than in the cropland. Fields for crops or grazing supported more interactions than the water’s edge in the plant–herbivore and microbivore channels. Connectance increased with the total richness of each community. Higher connectance within the microbivore and predator–prey soil food web channels were associated with soil NO₃⁻-N and elevation respectively, which served as surrogate indicators of high and low agricultural intensification.     

Soil fauna abundance and diversity in a secondary semi-evergreen forest in Guadeloupe (Lesser Antilles): influence of soil type and dominant tree species

The importance of secondary tropical forests regarding the maintenance of soil fauna abundance and diversity is poorly known. The aims of this study were (1) to describe soil fauna abundance and diversity and (2) to assess the determinants of soil fauna abundance and diversity in two stands of a tropical semi-evergreen secondary forest. Soil macrofauna and microarthropod abundance and soil macrofauna diversity were described at two sites developed on different soils and with different site histories: (1) a natural secondary stand (natural forest) under two dominant tree species, Pisonia subcordata and Bursera simaruba, and (2) a planted secondary forest (planted forest) under three tree species, B. simaruba, Swietenia macrophylla, and Tabebuia heterophylla. The effects of both soil and main tree species’ litter quality were assessed to explain soil fauna abundance and diversity. The abundance of soil macrofauna was significantly higher in the soil under the planted forest, and soil fauna communities were contrasted between the two sites. In the planted forest, a soil-dwelling macrofauna community developed (mainly consisting of the anecic earthworm Polypheretima elongata). In the natural forest, soil macrofauna and microarthropod communities were located at the soil surface. The effect of plant litter quality varied according to each dominant tree species and was superimposed to soil effect. The lowest macrofauna abundance was associated with B. simaruba in the natural forest. T. heterophylla supported a much greater macrofauna community than the two other tree species studied at the same soil, and it appears likely that this is due to the palatability of its leaves compared with the other trees (low lignin, tannins, soluble phenols).     

Effect of food type and placement on earthworm (Aporrectodea tuberculata) burrowing and soil turnover

Subsurface-dwelling Aporrectodea tuberculata, a common earthworm in Upper-Midwest (USA) agricultural fields, may be a significant component of agroeco-systems with regard to soil mixing and preferential transport of water and chemicals. In this study we looked at effects of food residue placement and food type on A. tuberculata burrowing and soil turnover in two-dimensional Evans box microcosms. Four food residue placements mimicked patterns induced by primary tillage and two food types, readily available and natural food sources, with no food as a control. An average earthworm population of 100 earthworms m^-2 was calculated to generate 1058 km ha^-1 of new burrows and turnover 7.9 Mg ha^-1 of soil in 1 week of activity at 20°C. Burrowing was random until food sources were encountered, at which time burrowing appeared to center around the food source.     

Analysis of the distribution of endemic and rare arthropods in high endemism areas of Algarve-South Portugal

The study of several arthropod groups in high endemism areas (HEA) of Algarve, the Southernmost province of Portugal, has revealed endemic species and species not yet recorded for the Portuguese fauna. The list includes 3 species of Isopoda endemic to Algarve, to Portugal or to the Iberian Peninsula, 2 species new to Portugal and 2 species new to the Iberian Peninsula; 2 species of Pseudoscorpiones not yet cited to Portugal; 11 species of Pauropoda new to Portugal, including one new species probably endemic; 15 species of Collembola endemic to the Portuguese or to the Iberian Peninsula faunas (Gama et al. 1997) and 37 species and 5 subspecies of Staphylinidae endemic to Algarve.With the exception of Collembola, which have been studied by us, the remaining groups have been submitted for study to several specialists.These findings heighten the biological richness of these areas of high endemism in terms of conservation of biological diversity. The authors draw attention to the necessity to preserve or restore the biological value of these areas, encouraging the adoption of protective measures and the creation of research programmes that include the implementation of taxonomic studies and co-operation between taxonomists and ecologists in order to preserve the biodiversity of these areas.     

Rhizosphere effects on soil bacterial abundance and diversity in the Yellow River Deltaic ecosystem as influenced by petroleum contamination and soil salinization

In this study, we compared the differences of bacterial abundance and diversity between rhizosphere and surrounding bulk soils under soil salinization and petroleum contamination in the Yellow River Delta on a 110-km-distance scale. In comparison with bulk soils, rhizosphere soils were mainly characterized by lower salinity and higher water content in saline soils. For bacterial abundance, the numbers of total bacteria and hydrocarbon degraders were significantly higher in rhizosphere soils than those in bulk soils. Although there was no significant difference in total petroleum hydrocarbon (TPH) concentration between the two types of soils, TPH had distinctly different effects on bacterial abundance in rhizosphere and bulk soils. TPH concentration was the major determinant of total bacterial abundance and had positive effects on abundances of hydrocarbon degraders. However, the abundances of total bacteria and hydrocarbon degraders in bulk soils were primarily determined by soil salinity and water content. Great abundance of rhizosphere bacteria suggested that plant roots could alleviate the stresses from soil salinization and provide more favorable microhabitats for bacterial growth. TPH had positive effects on bacterial diversity of both rhizosphere and bulk soils. Our results support the view that petroleum in the environments functions as both toxic chemicals and carbon sources to soil bacteria. Great abundance and diversity of total bacteria in plant rhizospheres would potentially improve the roles of bacteria in maintaining ecosystem functioning in the degraded ecosystems. Our results would improve our understanding of the relationships between rhizosphere effects and multiple environmental stresses that control the development of bacterial community in fragile anthropologically-affected ecosystems.     

球囊霉素及其在土壤生态系统中的作用

球囊霉素(Glomalin)是一种在土壤中大量存在的、由丛枝菌根真菌(Arbuscular mycorrhizal fungi, AMF)产生的具有良好热稳性的特殊糖蛋白。球囊霉素因其在促进土壤团聚体形成,保持团聚体稳定性,增加土壤有机碳库,提高植物抗逆能力以及降低重金属在土壤中的毒性等方面的作用备受人们关注。目前由于提取方法的原因,人们一般将球囊霉素的命名改为球囊霉素相关土壤蛋白(Glomalin related soil protein, GRSP)。随着研究的不断深入,人们对GRSP在生态系统中的作用展开了广泛的研究。GRSP对土壤颗粒有较强的胶结作用,其胶结能力为其他胶结物质的3～10倍;作为有机碳库的重要组成部分对土壤有机碳的贡献率为6.98%～31.3%,并且在土壤中周转时间较长为6～42年;GRSP还可以螯合不同的重金属,减少它们在土壤中的毒害作用以及降低潜在毒性。但想要更为深入的了解GRSP在生态系统中的作用需要对其结构进行进一步的了解、提取测定方法进行进一步的优化。本文重点总结了国内外研究中GRSP对土壤团聚体、土壤有机碳库的作用,GRSP研究中存在的主要问题以及未来...     

长期施用化肥对塿土微生物多样性的影响

【目的】土壤微生物在土壤有机质分解、营养循环、植物生长等方面都发挥着重要作用,研究长期施用化肥对其产生的影响可为农田合理施用化肥、培肥土壤和高产高效可持续性农业生产提供理论依据。【方法】以陕西杨凌"国家黄土肥力与肥料效益监测基地"的长期定位试验为基础,利用BIOLOG分析并结合常规分析研究了6种长期不同化肥施用方式不施肥(CK)、单施氮肥(N)、氮钾配施(NK)、磷钾配施(PK)、氮磷配施(NP)和氮磷钾配施(NPK)对土土壤微生物量和微生物功能多样性的影响。【结果】与不施肥CK相比,长期单施氮肥(N)的SMBC、SMBN没有显著变化,但明显降低了土壤微生物商和土壤微生物对氮素的利用;NP和NPK配施能够显著增加土SMBC和SMBN含量,明显提高了土壤微生物商,使土壤微生物种群结构发生了明显变化但土壤微生物对氮素的利用没有显著提高;长期偏施肥处理(NK、PK)的SMBC、SMBN和微生物商虽轻微增加,但土壤微生物种群结构没有显著改变。BIOLOG分析结果显示施磷处理(PK、NP和NPK)对微生物代谢活性的促进作用较大且在培养初期代谢活性较不施磷处理(CK、N和NK)增加显著。长期单施氮肥(N)对于提高土壤微生物多样性没有显著作用而其他化肥施用处理可以提高土土壤微生物群落的碳源利用能力、物种的丰富度和优势度,其中NP和NPK处理配施效果最好。化肥施用对土土壤微生物群落的均匀度没有显著影响。主成分分析的结果表明不同处理的土壤微生物对碳源利用表现出显著差异,氮磷养分的差异是产生分异的主要原因。【结论】土区小麦玉米轮作下,平衡施肥(NP或NPK配施)对于改善农田土壤微生物特性具有良好作用。     

Infant mortality and soil type: a case study in south-central England (with discussion)

We have analysed the differences in infant mortality for 1981 to 1990 in areas of contrasting soil types in south-central England. The soils overlie rocks of varied lithology and hydrology, ranging from porous and permeable Chalk and limestones, to the generally wet and impermeable Oxford and Lower Jurassic Clays. The study area comprises 504 administrative wards, for each of which the soil has been classified as being predominantly‘Wet’, ‘ Intermediate’ or ‘Dry’, depending on the degree of seasonal or periodic waterlogging. The soil classes used are those mapped by the Soil Survey of England and Wales and relate closely to the underlying geology. We find proportionately more infant deaths on the‘Wet’ soils, and a gradation towards lower infant mortality rates on the drier soils. Overall, infant mortality on the‘Wet’ soils is 31·9 percent greater than on the‘Dry’ soils, for reasons that remain unexplained. This relation between infant mortality and soil moisture remains after the effect of social class has been removed.     

Effect of the disposal of sludge from olive processing on some soil characteristics: Laboratory experiments

A laboratory experiment was performed during a 40-day incubation period in order to evaluate changes in organic and inorganic compounds of soil amended with two doses of sludge obtained from olive-oil processing waste waters. Differences between the amounts of organic components of the amended soil and those of the control, although related to doses and sampling time, disappeared at the end of the experimental period. On the contrary, the inorganic anion contents were still different for the various treatments, which suggest, especially for NO₃ ^? and SO₄ ^2?, a transient inhibition in the soil-sludge system. A germination test, carried out on the soil amended with different doses of sludge, indicates that after about twenty days even the soil containing the highest dose of sludge did not show toxicity any longer.