Short term response of soil microinvertebrates to application of entomopathogenic nematode-infected insects in two tillage systems

Entomopathogenic nematodes (EPN) in the families Steinernematidae and Heterorhabditidae occur naturally in the soil and are produced commercially for the management of soil-dwelling pests. EPN infected cadavers also represent a potential resource for other soil organisms. We examined the short-term (24 h) response in abundance, diversity and community composition of localized soil microinvertebrates to the presence of EPN-infected insect cadavers in no-till and conventional-till maize. We hypothesized that the response of soil microinvertebrates to the EPN-infected cadavers would vary by soil management practices and EPN species. We expected to observe greater numbers and diversity of arthropods in no-till compared with conventional-till soil, and in the vicinity of steinernematid-infected insect cadavers compare to what would be found in the vicinity of heterorhabditid-infected cadavers. 45,606 invertebrates were collected and identified to 134 morphotaxa. Tillage regime accounted for the majority of the variation observed (84.6%), whereas nematode treatment accounted for 7.5%. Taxonomic richness of invertebrates was greater in treatments with Steinernema carpocapsae-infected cadavers than with Heterorhabditis bacteriophora-infected cadavers. Some invertebrates increased in abundance where EPN were applied whereas others decreased, regardless of tillage practice. Applications of Galleria cadavers infected with steinernematids elicited positive responses from two mite taxa, Galumnidae and Scheloribates spp., while negative responses were elicited from three mite (Histiostomatidae, Scheloribates spp., Eupodes spp.), taxa and Entomobryidae (Collembola) in response to applications of Heterorhabditis-infected cadavers.     

Reducing the dimensionality of soil microinvertebrate community datasets using Indicator Species Analysis: Implications for ecosystem monitoring and soil management

Soil microinvertebrates are closely associated with soil decomposition and nutrient cycles and may be particularly responsive indicators for soil management practices. However, identification of appropriate bioindicator species for many systems has been severely limited by a lack of information on species taxonomy, distribution, and functional role. We evaluated Indicator Species Analysis (ISA) as an objective method for assessing the indicator potential of different taxa without regard to their ecological role or expected management response. Restricting ordination and site classification to significant indicator morphotaxa reduced the dimensionality of the community data matrix by 69% while only slightly decreasing the efficiency of unsupervised classification (from 87.2 to 84.4%); the percentage of total variability explained by first two PCA axes increased following ISA. When these same indicator morphotaxa were used to classify an independent set of samples, the percentage of total variability explained by the first two PCA axes increased from 55.3 to 65.2%; cluster analysis of the test dataset correctly classified 47 out of 50 plots by cover type (94% accuracy). However, restriction of analysis to indicator morphotaxa alone reduced detection of differences between sampling dates relative to the complete dataset. Although care needs to be taken to ensure that the dataset used for indicator selection is fully representative of underlying temporal and spatial variability, ISA appears to overcome many of the limitations associated with parametric and multivariate approaches for identifying indicator morphotaxa and has the potential to greatly reduce the taxonomic expertise and labor costs associated with sorting and identification of soil microarthropods.     

Effect of seasonality and agricultural practices on occurrence of entomopathogenic nematodes and soil characteristics in La Rioja (Northern Spain)

The effects of seasonality and land management on entomopathogenic nematodes (EPNs) distribution and on soil characteristics were studied in natural areas and agricultural fields under organic and conventional management in La Rioja (Northern Spain). The population density of the native EPNs as well as air temperature, rainfall, soil fertility, soil moisture, and soil content of heavy metals were seasonally recorded over 2 consecutive years. The highest occurrence of EPNs was observed in autumn, followed by spring and summer. Agricultural management influenced the amount of soil organic matter, nutrients and heavy metals, as well as soil volumetric moisture and temperature, leading to statistical differences mainly between natural and agricultural sites, but also in some cases between different types of agricultural management. The usefulness of soil organic matter, C, N, P and K content, as well as the C/N, C/P and N/P ratios as indicators for differentiating conventional and organic crop management as well as the role of agricultural practices such as tillage and fertilizing is discussed.     

Diversity surfaces and species wave fronts in a soil microarthropod assemblage: Adding the dimension of time

As a general rule, animal species of intermediate size within a given taxonomic group are most abundant in nature. It is not known if these patterns occur in small-bodied taxa, such as soil microarthropods, or how these patterns change through time. Here I show that Oribatida (Acari), the most abundant and diverse arthropod fauna of coniferous forest soils, exhibit this pattern. However, the pattern is more complex than reported for other arthropods. I analyzed the total species surface comprising 6613 individuals and 54 species by forest stand. The underlying pattern consists of 15-year stands and 30-year stands forming two distinct and separated maxima. These results suggest that assemblage patterns form early in the development of ecological communities, and that these patterns appear within the soil assemblage as waves propagating in species–abundance–body size space during forest development. These results also support the assertion that undescribed species will likely be of intermediate size within a group. This analysis contributes to investigations of biodiversity and body size relationships by adding the temporal dimension. Potential applications are in disturbance and indicator studies or other work where changes in assemblage structure are used as measures of disturbance or as response variables in manipulative studies.     

Nematode faunal response to long-term application of nitrogen fertilizer and organic manure in Northeast China

Nematode faunal response to the long-term (20-year) application of nitrogen fertilizer and organic manure was monitored in a Hapli-Udic Cambosol of Northeast China, where no fertilizer (C), nitrogen fertilizer (N), organic manure (M) and nitrogen fertilizer plus organic manure (N + M) treatments were compared. The obtained results showed that total nematode abundance responded positively to the M and N + M treatments. The numbers of Acrobeloides increased in the M and N + M treatments at maize jointing and booting stages, and those of Aphelenchoides were higher in the N + M treatment than in the N treatment at maize ripening stage. Early in the growing season, the numbers of bacterivores of cp-1 (cp, colonizer-persister) and cp-2 guilds were higher in the M and N + M treatments than in the N treatment, while those of bacterivores and fungivores of cp-4 guilds were higher in the C treatment than in the N, M and N + M treatments. Except at maize seedling stage, the numbers of fungivores of cp-2 and herbivores of cp-3 guilds were higher in the N + M treatment than in the C treatment. Ratios of the weighted abundance of representatives of specific functional guilds were used as indicators of food web structure, enrichment and decomposition channels. Values of the enrichment index (EI) at maize seedling and jointing stages were higher in the M and N + M treatments than in the C and N treatments, while an opposite trend was observed in the channel index (CI). Higher EI and lower CI suggest an enriched soil food web dominated with bacterial decomposition channels in the M and N + M treatments.     

Palatability of microfungi to soil arthropods in relation to the functioning of arbuscular mycorrhizae

We investigated the feeding preferences of six species of mites and collembolans for three fungi commonly associated with roots of Acer saccharum (Glomus macrocarpum, Alternaria alternata and Trichoderma harzianum), from a maple-forest soil in southern Ontario, Canada. Experiments were also conducted in vitro to determine animal feeding responses to (1) increasing quantities of hyphal biomass, (2) the presence of root vs. litter fungal substrates, and (3) hyphae of different widths of Glomus macrocarpum. The results indicate that arthropods prefer to graze in the litter region rather than in the deeper soil layers. Under ideal moisture/temperature conditions, animals are forced to the lower regions by interspecific interactions. They prefer to graze on hyphae of conidial fungi rather than on those of arbuscular mycorrhizal fungi. When arbuscular mycorrhizal fungal hyphae are grazed, there is a clear preference for the narrower hyphae, which are those further away from the root. The thicker hyphal segments, commonly found connecting absorptive hyphal fans to roots, were less preferred. These data are not consistent with the hypothesis that microarthropods are detrimental to arbuscular mycorrhizal associations, and suggest that Glomalean fungi may have evolved mechanisms to deter grazing by microarthropods.     

Effect of phosphogypsum application and bacteria co-inoculation on biochemical properties and nutrient availability to maize plants in a saline soil

Phosphogypsum (PG), which contains Ca, P and S and has an acidic effect, may be applied to manage soil constraints such as alkalinity and salinity. For increasing nutrients bioavailability, biofertilizers are commonly applied. Therefore, the aim of this study was to assess PG effect either alone or in combination with the mixed co-inoculation of plant growth promoting rhizobacteria on a saline soil. In a greenhouse pot experiment with maize (Zea mays L.), the inoculated and non-inoculated saline soils were treated with PG at 10 g kg^?1 (PG10), 30 g kg^?1 (PG30), and 50 g kg^?1 (PG50). The soil pH, electrical conductivity (EC_e), and macro-(NPK) and micronutrients (Fe, Mn, Zn, and Cu) availability to mays were examined. Applying PG reduced soil pH and co-inoculation induced significant decreases in soil EC_e. Applying PG increased significantly soil available P. Applying PG combined with co-inoculation effectively increased the soil available K. The soil available micronutrients decreased significantly with PG. However, the inoculated maize treated with PG showed significant higher dry weight (82.1–127.4%) and nutrients uptake than the control. It could be concluded that PG along with co-inoculation may be an important approach for alleviating negative effects of salinity on plant growth.     

Soil biota and soil properties in the surface rooting zone of mesquite (Prosopis glandulosa) in historical and recently desertified Chihuahuan Desert habitats

Summary The woody legume, mesquite (Prosopis glandulosa) has expanded from its historical habitats (playas and arroyos) to recently occupied grassland and dune habitats during the desertification of perennial grasslands in the Chihuahuan Desert. We studied historical and recently occupied sites, having hypothesized that the trophic structure and population density of soil microarthropods and nematodes associated with the surface root system of mesquite would differ in sites representing historical and recent habitats, and that the N mineralization potential would be lower in the recent habitats. Our results showed that net N mineralization potential did not differ significantly among the sites, even though soil nutrient concentrations and texture varied widely. Concentrations of organic C, N, and P were lowest in the recent dune habitat and highest at the playa. Very low concentrations of P in the dune and grassland soils implicated P as a limiting factor in these systems. The bacterial-feeding and omnivore-predator functional groups made up the largest fraction of the nematode community at most of the sites. The high density of plant-feeding nematodes at the playa indicated that herbivory is potentially most important at this site. Total microarthropod densities did not vary significantly among habitats, with Collembola densities highest in the mesquite dunes. Grazers were the dominant microarthropod functional group. While both C and N pool sizes were higher in the historical habitats, a higher substrate lability in the recent habitats appeared to support biota populations and N mineralization rates equivalent to those in the playa and arroyo. Differences in soil properties and biota among historical and recent mesquite habitats may be important for understanding the changes that have occurred in Chihuahuan Desert ecosystems during desertification.     

Barley yield response to soil organic matter and texture in the Pampas of Argentina

Soil organic matter (SOM) is known to play a major role in soil fertility due to its influence on physical, chemical and biological properties of soil; and it is closely related to particle size distribution. The ratio of SOM (g kg⁻¹) to clay + silt content (g kg⁻¹) was evaluated as an indicator of soil quality for barley (Hordeum vulgare) grain yield, reflecting N availability and soil physical conditions to which crop development is sensitive. Thirty-eight sites in the semiarid Pampa region of Argentina with a wide range of SOM and texture were evaluated for malting barley yield during three growing seasons. In control plots, 51% of grain yield could be explained by this indicator. The threshold value between high and low N-fertilization response was 4.4. Better yield prediction to almost 68% was achieved by combining the SOM to clay + silt indicator with initial nitrate content of the soil at seeding. This combined indicator was also able to explain a high proportion of water use efficiency, particularly in the early growth stages. The ratio of SOM to clay + silt content provided a better tool for estimating grain yield than nutrient availability or SOM alone.     

Kinetic parameters of dehydrogenase in the assessment of the response of soil to vermicompost and inorganic fertilisers

 Kinetic parameters (V _max and K _m) of dehydrogenase activity were determined in order to assess the metabolic response of a soil about 1 year after organic and mineral treatments. The soil was planted with maize (Zea mays) and treated with the following fertilisers: organic (vermicompost; VC), mineral (ammonium phosphate and urea), and an organo-mineral mixture. V _max, which represents a measurement of the quantity of enzyme, markedly increased in organic and organo-mineral treatments, indicating that the addition of organic matter caused an increase in dehydrogenase in the active microbial biomass. K _m, representing enzyme-substrate affinity and/or different sources of the enzymes, was similar in VC-treated soil and control soil, while it doubled in organo-mineral and mineral treatments. These results suggest that the use of VC did not alter the enzyme-substrate affinity, while mineral fertiliser reduced this affinity or changed the composition and activity of soil microbiota. A positive correlation was found between V _max, the metabolic index (dehydrogenase/water-soluble carbon ratio), and the soil organic matter content. The kinetic constants of dehydrogenase activity and the metabolic index may be considered valid parameters to monitor the evolution of microbiological activity in soil. Received: 4 February 2000     

川西亚高山森林土壤过氧化氢酶活性对升高温度和CO_2浓度的响应

川西亚高山针叶林由于其特殊地理位置和特定生态环境下植被的演替动态,使之成为全球变化的敏感性区域之一。本文通过原位模拟升高温度2(±0.4)℃和CO2浓度加倍对川西亚高山针叶林土壤过氧化氢酶活性的影响。结果显示升温和升高CO2浓度对岷江冷杉(Abies faxoniana)根际和非根际土壤过氧化氢酶活性的影响不同,还与冷杉的种植密度有关。同时,冷杉根际和非根际土壤过氧化氢酶活性对升高温度和CO2浓度的响应还随着时期而发生变化。另外,遮荫处理也会影响土壤过氧化氢酶活性。原位研究结果表明亚高山针叶林土壤酶对升高温度和CO2的响应并非简单的提高或者抑制,不同时期、不同密度以及与非根际环境中过氧化氢酶活性反应差异很大,可能涉及的土壤学和生态学过程十分复杂,需深入研究。     

Soil organic carbon distribution in relation to land use and its storage in a small watershed of the Loess Plateau, China

Soil organic carbon (SOC) is an important component in agricultural soil, and its stock is a major part of global carbon stocks. Estimating the SOC distribution and storage is important for improving soil quality and SOC sequestration. This study evaluated the SOC distribution different land uses and estimated the SOC storage by classifying the study area by land use in a small watershed on the Loess Plateau. The results showed that the SOC content and density were affected by land use. The SOC content for shrubland and natural grassland was significantly higher than for other land uses, and cropland had the lowest SOC content. The effect of land use on the SOC content was more significant in the 0-10 cm soil layer than in other soil layers. For every type of land use, the SOC content decreased with soil depth. The highest SOC density (0-60 cm) in the study area was found in shrublandII (Hippophae rhamnoides), and the other land uses decreased in the SOC density as follows: natural grassland > shrublandI (Caragana korshinskii) > abandoned cropland > orchard > level ground cropland > terrace cropland > artificial grassland. Shrubland and natural grassland were the most efficient types for SOC sequestration, followed by abandoned cropland. The SOC stock (0-60 cm) in this study was 23,584.77 t with a mean SOC density of 4.64 (0-60 cm).     

狼尾草等6种植物对十溴联苯醚污染土壤的生理响应及其修复效果

考察了狼尾草、龙葵、空心菜、苣菜、芥菜和鱼腥草6种植物对土壤中十溴联苯醚（BDE-209）的生理响应及其修复效果。结果表明,在BDE-209污染条件下,供试植物体内丙二醛（MDA）含量升高,表明植物受到一定的毒害作用,而在植物抗逆境机制作用下,植物体内可溶性蛋白质含量升高,超氧化物歧化酶（SOD）活性下降;在供试植物生物量方面,BDE-209对龙葵、空心菜和狼尾草地上部有促进作用,而对苣菜、芥菜具有一定的抑制作用;6种修复植物体内均检测出BDE-209,且地上部与根部BDE-209含量具有显著差异,其中狼尾草根部干重含量高达16.93mg·kg-1;修复60d后,土壤中BDE-209含量均有一定程度的下降,最高去除率可达40.44%,且根际土与非根际土BDE-209去除率有显著差异。修复效果依优劣次序为狼尾草〉龙葵、空心菜〉鱼腥草〉芥菜〉苣菜。     

Differential growth response of Curculigo orchioides to native arbuscular mycorrhizal fungal (AMF) communities varying in number and fungal components

The study reports diversity of arbuscular mycorrhizal fungal (AMF) species in the rhizosphere of an endangered anticancerous herb – Curculigo orchioides Gaertn. in its natural habitat. A total of 18 species of AMF, belonging to three genera (Acaulospora, Glomus and Gigaspora) were recorded, with Glomus microcarpum being the most abundant species type. The AMF species composition across the study sites appeared to be influenced by soil pH rather than soil P and vegetation. Acaulospora laevis spores were restricted to sites where the soil pH was acidic. The effectiveness of these native AMF species on growth performance of C. orchioides plants was compared under experimental conditions. In general, the mycorrhizal plants were superior in most of the evaluated parameters, but the extent to which the growth of mycorrhizal plants was influenced varied with the inocula used. The plants inoculated with mixed consortia containing maximum AMF species richness exhibited improved growth in comparison to consortia containing lower AMF diversity and monospecies cultures. The variable plant responses observed with any two consortia having same species richness in the present study could be due to variable component AMF species and their relative abundance. These results emphasize the need to protect the below-ground diversity of AMF and recommend their usage for restoration practices.     

Using Cs measurements to validate the application of the AGNPS and ANSWERS erosion and sediment yield models in two small Devon catchments

Distributed erosion and sediment yield models are being increasingly used for predicting soil erosion and sediment yields in agricultural catchments. In most applications, validation of such models has commonly been restricted to comparison of the predicted and measured sediment output from a catchment, because spatially distributed information on rates and patterns of soil redistribution within the catchment has been lacking. However, such spatially distributed data are needed for rigorous model testing, in order to validate the internal functioning of a model and its applicability at different spatial scales. The study reported in this paper uses two approaches to test the performance of the agricultural non-point source pollution (AGNPS) and areal non-point source watershed environmental response simulation (ANSWERS) erosion and sediment yield models in two small catchments in Devon, UK. These involve, firstly, comparison of observed and predicted runoff and sediment output data for individual storm events monitored at the basin outlets and, secondly, information on the spatial pattern of soil redistribution within the catchments derived from ¹³⁷Cs measurements. The results obtained indicate that catchment outputs simulated by both models are reasonably consistent with the recorded values, although the AGNPS model appears to provide closer agreement between observed and predicted values. However, the spatial patterns of soil redistribution and the sediment delivery ratios predicted for the two catchments by the AGNPS and ANSWERS models differ significantly. Comparison of the catchment sediment delivery ratios and the pattern of soil redistribution in individual fields predicted by the models with equivalent information derived from ¹³⁷Cs measurements indicates that the AGNPS model provides more meaningful predictions of erosion and sediment yield under UK conditions than the ANSWERS model and emphasises the importance of using information on both catchment output and sediment redistribution within the catchment for model validation.     

云南省主要地质背景区铜、锰、锌、镁、钾在岩石-土壤-饲料系统的分布与迁移规律研究

对云南省6个主要地质背景区的土壤、岩石和饲料样品的铜、锰、锌、镁和钾元素进行测定分析。结果表明:玄武岩和碳酸盐岩红壤区土壤和饲料钾、镁、锌、锰和铜元素含量较丰富;碳酸盐岩、碎屑岩和玄武岩混合型黄红壤区居中;而由碎屑岩和变质岩发育的土壤区土壤和饲料钾、镁、锌、锰和铜元素最低。饲料中钾、镁、锌、锰和铜的含量受地质背景值,特别是土壤中元素的丰度的影响不大。     

黄土丘陵区油松、沙棘人工林土壤呼吸动态及其对土壤温度和水分的响应

作为陆地生态系统碳通量的重要组成部分,土壤呼吸在维持全球碳循环及碳平衡中具有重要作用.以黄土丘陵区油松、沙棘人工林为研究对象,于2015年6月至2016年5月,采用LI-8100土壤碳通量测量系统,分别观测二者的土壤呼吸(Rs)、5 cm土壤温度(T)和水分(W),分析2种人工林Rs的动态特征及其对T和W的响应.结果表明:1)季节尺度油松、沙棘人工林Rs夏季(6-8月)最高(2.31和2.89 μmolCO2/m2·s),冬季(12-2月)最低(0.60和0.65μmolCO2/m2·s),年均值分别为1.51和1.92 μmolCO2/m2·s,年呼吸总量分别为18.90和22.81tCO2/hm2·a,冬季呼吸量占年呼吸总量比例分别为14.67％和12.65％;日尺度最高值出现在10:00-16:00,最低值均出现在6:00.2)季节尺度2种林分Rs与T均呈显著指数关系(P＜0.01),与W则呈显著线性负相关(P＜0.01),且沙棘林全年尺度土壤呼吸Q10值(1.40)显著高于油松林(1.34,P＜0.01).3)日尺度上,油松、沙棘人工林W分别大于13％和12％时,T对Rs的解释量(R2)均有所提高.因此,在充分考虑温度和水分对土壤呼吸影响的同时,加强冬季土壤呼吸的观测,对未来气候变化条件下,区域碳循环估算模型的完善具有重要意义.     

Nutrient status of soil and winter wheat (Triticum aestivum L.) in response to long-term farmyard manure application under different climatic and soil physicochemical conditions in the Czech Republic

Long-term field experiments with annual crop rotation were established in 1955 and 1956 at three locations (Lukavec, ?áslav, Ivanovice) in the Czech Republic, which differ in their climate and soil physicochemical properties. The effect of cattle farmyard manure (FM) and a combination of FM and mineral (NPK) fertilizer application (FMNPK) on nutrient status of soil and the response of winter wheat, and nutrient content of wheat grain and straw were evaluated after ~60 years since the establishment. The results showed higher pseudototal (aqua regia soluble) contents of phosphorus and sulfur from FM and FMNPK application compared with control, whereas the labile and moderatory labile content of individual nutrients (except calcium) varied between treatments. The nutrient content of wheat grain and straw was more significantly (p < 0.05) affected by the location and growing season than by the fertilizers. The substantial changes in wheat nutrient uptake occurred for the weakly acidic loamy Gleyic Phaeozem, whereas the lowest response due to fertilizer application was observed for the acidic Cambisol (sandy loam texture). Even after six decades of FM and FMNPK application, the effectiveness of these treatments was predominantly influenced by the soil and climatic conditions at the individual locations.