Interaction between humus form and herbicide toxicity to Collembola (Hexapoda)

Laboratory experiments were conducted using intact collembolan communities, exposed to Madit D^®, a phenylurea herbicide (active ingredient isoproturon). Effects were investigated using two distinct humus types, an acid Dysmoder and a neutral Eumull. Within two weeks, no effect of the herbicide was displayed by the Eumull population, while the Dysmoder population was stimulated. When animals were able to escape from the herbicide through a perforated wall separating two compartments filled with natural soil, the behavior of collembolan communities exhibited interactive (non-additive) effects of humus type and herbicide application. The combination of an acid soil (supposedly providing greater tolerance to organic pollutants) with a neutral soil, increased biodiversity of Collembola, but caused the disappearance of some acido-sensitive species, pointing to complex relationships between pesticides, soils and soil organisms. Parallel experiments with single species demonstrated that at the recommended dose Madit D^® may cause avoidance effects, but no toxicity.     

Relationships between soil fauna communities and humus forms: Response to forest dynamics and solar radiation

This study investigated the responses of soil animal communities, soil functioning and humus forms to forest dynamics and solar radiation. We examined changes in invertebrate communities and soil features in two subalpine spruce forests (Eastern Italian Alps, Trento) growing on a calcareous bedrock, with different sun exposures (north and south), each forming a chronosequence of three developmental phases: clearing, regeneration stand (25-year-old trees) and mature stand (170-year-old trees). Our results indicate that the two forest sites differed in solar energy input, soil chemical properties and the relationships between forest dynamics and animal communities. In the north-facing site, soil fauna communities were very similar in the three forest developmental phases. Conversely, in the south-facing site, the composition of invertebrate communities and the diversity of zoological groups varied greatly among developmental phases. The highest abundance of total invertebrates, and mites in particular, occurred in the south-facing mature stands while the south-facing regeneration stand was characterised by higher densities of Collembola, Chilopoda, Symphyla, Protura and Aranea. The structure of communities in clearings was the same as in regeneration stands but with lower invertebrate abundance. Humus forms and soil features changed with developmental phases in both the south- and north-facing sites, although variations were more pronounced in the southern exposure. Mature stands were characterised by high levels of soil organic carbon and nitrogen, C/N values and low pH, the clearings and regeneration stands being characterised by a greater release of mineral nitrogen. The diversity of zoological groups (Shannon–Wiener index) was linearly correlated to soil pH, Humus Index, the amount of organic carbon and the species richness of herbaceous plants. Our results about the composition and the diversity of invertebrate communities are consistent with the observations of other authors studying south-exposed forests growing on different bedrock types, indicating that such relationships are widespread. The higher densities of invertebrates in the south-facing site may be attributed to higher solar radiation, and the positive correlation observed between total soil fauna abundance and solar energy supports the “more individuals” hypothesis that assumes a positive relationship between the number of individuals and energy availability. Possible ways by which forest dynamics control soil invertebrate communities are discussed.     

Some characteristics of the humus in soil types (part 3) composition groups of humus

In most literature on soil, the term humus has been used as synonymous with soil organic matter, on the other hand, it has been applied to a portion of soil organic matter that has decomposed and has lost the structure of the original matter, from which it has derived. Scheffer and Schachtschabel ¹⁾ defined the humus not synonymously with soil organic matter, but, in a broad sense, as all the dead organic substances which are accumulated on the soil surface as well as in the soil layer, and undergo continually decomposition, alteration, and synthetic reactions. According to them, the composition groups of humus are divided into non-humic and humic, and the latter group is sub-divided into (1) fulvic acid and humo-lignin acid, (2) humic acid, (3) humin, and (4) humus coal. Some natures of these composition groups of humus are shown in Table 1.     

Relationships between testate amoebae and fungi in humus microcosms

Malt extract was added to soil in order to provoke the natural growth of fungi. The testate community was quantified. The main species, Phryganella acropodia increased in numbers during the first 3 weeks then it reached a steady state. The growth of three other species: (Centropyxis aerophila sphagnicola, Plagiopyxis declivis and Tracheleuglypha acolla) was followed and their densities were one-tenth of those of P. acropodia although their numbers increased towards the end of the experiment when the density of P. acropodia became stable.Features of the growth of the testate amoebae were estimated (rate of growth, production, mortality, number of generations and generation time) to explain the fluctuations of their densities.The numbers of fungal spores and the variation of the biomass of mycelium were measured, and were different to what would have been expected as the biomass of fungi remained unaltered. The hypothesis of mycophagy by P. acropodia is proposed and supported by the frequency of the presence of this species on mycelium.     

Relationships between soil properties and feeding activity of soil fauna in acid forest soils

We investigated the relationships between soil chemical properties, humus form, and feeding activity in eight forest sites in Northrhine‐Westphalia, Germany. The study sites varied in forest type (oak, oak‐hornbeam, spruce, and pine). Three study sites were located under the same climatic conditions, and five study sites were distributed all over Northrhine‐Westphalia. We determined humus form, soil chemical properties, and feeding activity in three replication plots per site. We used the bait‐lamina test to determine feeding activity of soil fauna. Independent of forest type, all study sites were very acid with pH(CaCl₂) values in the Ah horizon between 2.8 and 4.0. The three study sites located under the same climatic conditions showed very homogenous soil chemical properties (pH in Ah: 2.9–3.0), whereas the five other sites varied significantly due to their soil chemical parameters (pH in Ah: 2.8–4.0). All single sites presented feeding activities with a very low spatial heterogeneity. Forest types and climatic conditions were not related to activity of soil fauna. Feeding activity and thickness of the O layer were strongly negatively correlated, whereas the activity was strongly positively correlated to soil pH in the five study sites with a wide range of soil chemical parameters. The three extremely acid forest sites presented significant differences in feeding activities that were not related to soil chemical properties.     

Near-infrared characteristics of forest humus are correlated with soil respiration and microbial biomass in burnt soil

Near-infrared spectroscopy and soil physicochemical determinations (pH_H2O, organic matter content, total C content, NH _inf4 ^sup+ , total N content, cation-exchange capacity, and base saturation) were used to characterize fire-or wood ash-treated humus samples. The spectroscopic and the soil physicochemical analysis data from the humus samples were used separately to explain observed variations in soil respiration and microbial biomass C by partial least-square regression. The first regression component obtained from the physicochemical and spectroscopic characterization explained 10–12% and 60–80% of the biological variation, respectively. This suggests that information on organic material collected from near-infrared spectra is very useful for explaining biological variations in forest humus.     

Structural relationships among vegetation,soil fauna and humus form in a subalpine forest ecosystem: a Hierarchical Multiple Factor Analysis (HMFA)

Aboveground vegetation, four belowground fauna groups and humus composition have been analyzed in order to investigate the links between autotrophic and heterotrophic communities in a Norway-spruce mountain forest in Tours-en-Savoie (France). The aboveground plant community was recorded in small patches corresponding to contrasting microhabitats. Animal communities and humus layers were sampled within the same patches. The relationships between humus profile, faunistic and floristic compositional gradients were investigated by Multiple Factor Analysis (MFA) and, for the first time in ecology, a Hierarchical Multiple Factor Analysis (HMFA) was used to interpret differences among humus layers. The analysis revealed a pattern with three main groups of microhabitats. The thorough study of separate humus layers could explain this result. The interplay of plant–animal–soil interactions is likely to drive the ecosystem toward three alternative states supporting humus traditional classification between mull–mor–moder. HMFA revealed the importance of depth to explain this contrast among humus forms, using humus layers as diagnostic tools in both inert and living components. HMFA also showed contrast between unexploited and exploited parts of the forest, but the study of soil and vegetation indicate that this contrast does not only hold in forest management but also in geomorphology. RV-coefficients among the six groups of variables showed significant fauna–fauna relationships in almost all humus layers except Actinedida. Plant–soil interactions are not as strong as expected and are even weaker when the soil in question is deep. In addition, HMFA failed to show direct interactions between plant and soil fauna but, paradoxically, HMFA does suggest that indirect plant–fauna interactions are at the focus of the ecosystem strategy that leads to the differentiation of ecological niches within the forest mosaic.     

Isolation and analysis of the non-hydrolysable fraction of a forest soil and an arable soil (Lacadée, southwest France)

Recent studies have pointed to the occurrence in soil organic matter of an insoluble macromolecular fraction, resistant to drastic alkali and acid hydrolysis. This non-hydrolysable fraction may contribute to the stable carbon pool in the soil and thus be important for the global carbon budget. We have developed a method to isolate such chemically resistant components, whilst ensuring complete elimination of the hydrolysable constituents of the organic matter but avoiding the formation of insoluble compounds via Maillard-type condensation reactions. Maize leaves, material especially susceptible to artefact formation, were used for this optimization. Several of the treatments that we tested, including the Klason lignin protocol, proved unsuitable. The most suitable protocol, by progressive hydrolysis with trifluoroacetic and hydrochloric acid, revealed a non-hydrolysable fraction in maize leaves accounting for about 5% by weight of the leaves and corresponding chiefly to lignin and condensed tannins. The protocol was applied to a forest soil and to the soil from an adjacent plot cleared 35 years ago and since cropped continuously with maize. The abundance, chemical composition and sources of the non-hydrolysable fraction of these two soils were determined by a combination of spectroscopy, pyrolysis and electron microscopy. This fraction accounted for about 6% of the total organic carbon of both soils; it contains aliphatic moieties, black carbon, melanoidins and, we think, condensed tannins.     

Differential thermal analysis (DTA) and thermogravimetry (TG) of soil humus substances

DTA and TG data as well as infra red spectra and elementary analysis of chernozem- and podzolicsoil humic and fulvic acids revealed two structures — aromatic and aliphatic in their molecules. The aromatic structure predominates in humic acids, the aliphatic in fulvic acids.     

Relationships between soil respiration and soil moisture

The interaction of soil microbes with their physical environment affects their abilities to respire, grow and divide. One of these environmental factors is the amount of moisture in the soil. The work we published almost 25 years ago showed that microbial respiration was linearly related to soil-water content and log-linearly related to water potential. The paper arose out of collaboration between two young researchers from different areas of soil science, physics and microbiology. The project was driven by not only our curiosity but also the freedom to operate without the constraints common to the current system of science management. The citation history shows three peaks, 1989, 1999 and from 2002 to the present day. Interestingly, the annual citation rate is as high as it has ever been. The initial peak is due to the application of the work to studies on microbial processes. The second peak is associated with the rise of simulation modelling and the third with the relevance of the findings to climate change research. In this article, our paper is re-evaluated in the light of subsequent studies that allow the principle of separation of variables to be tested. This re-evaluation lends further credence to the linear relationship proposed between soil respiration and water content. A scaled relationship for respiration and water content is presented. Lastly, further research is suggested and more recent work on the physics of gas transport discussed briefly.     

A mathematical model of energy budgets of forest humus of the mull,moder and mor types in Poland

A mathematical solution is proposed of the long-discussed problem of accumulation and decomposition of forest humus, and a generalized form of a dynamic mathematical model of energy budgets of a forest humus layer with any number of subhorizons differing in degree of decomposition is presented. Methods of taking measurements of the relevant parameters for the model are also indicated.The model in question has been applied in analysing the results of detailed studies of energy budgets of forest-floor layers in examples of three climax forest ecosystems with three different types of forest humus (mull, moder, mor).     

Relationships between parameters of the humus status of forest and meadow soils and their altitudinal position on the main Crimean range

The influence of bioclimatic conditions related to the elevation above sea level on the quantitative and qualitative parameters of humus in mountain soils has been studied. It is shown that changes in the water and temperature conditions with the altitude do not exert significant effect on the humus content in mountain- forest soils, because the total amount of soil organic matter mainly depends on the composition and state of the vegetation cover. The humus content is the highest in meadow soils formed on mountain plateau with excessive moistening, which determines the formation of dense grass cover and the temperature regime favorable for humification. The percentage of Cha in the composition of Corg and the optical density of humic acids (HAs) are the qualitative parameters of the soil humus status changing with the altitude. The intensity of humus coloring of the soil depends on the content and optical density of HAs. A comparison of color intensity in the mountainous meadow chernozemlike soils and plain chernozems has shown its significant dependence on the hydrothermic conditions.     

北京八达岭地区典型林分林地土壤抗蚀性分析

为研究八达岭地区不同森林植被对土壤抗蚀性的影响,揭示不同林分林地土壤抗蚀性特征,以该地区典型植被类型(油松林、针阔混交林、阔叶林和灌木林)为研究对象,运用主成分分析及相关分析方法,研究该区域内,不同林分类型土壤的抗蚀性.结果表明:八达岭地区林分林地土壤干筛时,团聚体主要集中于5～2 mm粒径范围内,在0.5-0.25 mm粒径范围内质量分数最少;湿筛后,＜0.25 mm小粒径范围内质量分数最大,在10～5 mm大粒径范围内质量分数最少.为比较各典型林分林地土壤抗蚀性,选取土壤理化性质、土壤团聚特征等12种指标,以主成分分析方法为基础,确定评价北京八达岭地区土壤抗蚀性的最佳指标体系,同时,经相关分析选定干筛时,土壤几何平均直径(GMD)为八达岭地区各典型林分林地最佳土壤抗蚀指标.经分析,八达岭地区各典型林分土壤表层(0～10 cm)抗蚀性由强到弱依次为阔叶林＞灌木林＞针阔混交林＞油松林;对于主要发生土壤侵蚀的0～20 cm土壤表层抗蚀性由强到弱为灌木林＞油松林＞阔叶林＞针阔混交林;在各土层平均值综合情况下,评价结果选取抗蚀性综合指数表示,得出各林地土壤抗蚀性由强到弱依次为灌木林＞油松林＞针阔混交林＞阔叶林.     

On the complex formation between soil humus and polyvalent cations

In 1946 BREMNER et al.(1) suggested a theory that, in soils, polyvalent metals are combined with organic matter as metal-organic matter complexes, and that these complexes are insoluble in solvents that do not themselves form complexes with metals. The principle of one of the most prevailing methods for humus extraction, the neutral sodium pyrophosphate extraction proposed by BREMNER and LEES (2), is a corollary of the theory.     

Effects of acid anion additions (trifluoroacetate and bromide) on soil solution chemistry of a northern hardwood forest soil

Experimental plots within the Hubbard Brook Experimental Forest, NH, were treated with sodium trifluoroacetate (TFA) and lithium bromide (Br), to study the impact of TFA alone and in the presence of increased anion concentrations (e.g. acid deposition) on the soil solution chemistry of a northern hardwood forest soil. Trifluoroacetate is a major atmospheric degradation product of replacement compounds of chlorofluorocarbons (CFC) and Br is widely used as a hydrologic tracer. Calculated drainage losses via soil water flow were less than 60% of inputs, added during the summer, and TFA and Br were temporarily retained in the soil until fall. The initial indication of an acid input of the treatments (HTFA, HBr) in the Bs2 horizon, which reflects stream water chemistry as well, was an increase of base cations in the soil solution, decreasing the soil's acid neutralizing capacity. Thereafter, trifluoroacetate and Br concentrations peaked after the peak in base cations, synchronous with peaks in H⁺ and Al concentrations. Organic anions, nitrate and chloride played the major role in accompaning base cations out of the solum. Sulfate retention at soil adsorption sites was increased by the presence of TFA and Br, reducing its role as a mobile anion of base cations in this experiment. Relative retention of anions for the whole profile of this northern hardwood forest soil was estimated by correlation analyses and input-output balances in decreasing order on an equivalant basis: SO₄ > TFA = Br ≥ Cl > NO₃ > organic anions. Recovery from acid additions were recorded within several weeks after the treatments were stopped. Evaluating the impact of added chemical compounds to soils must be considered within the context of linkages among element cycles and pools.     

Principal soil types (Great soil groups) in Japan

Classified into three types, zonal, intra-zonal, and azonal, Japanese soil type may be explained as follows (see “General map of principal soil types”).     

Simulation of solution chemistry in an acidic forest soil

The computer simulation model SOILEQ was used to estimate soil solution chemistry over a 7 week period from October 3 to November 14, 1988 in the soils of a sugar maple forest located near St. Hippolyte, Quebec, Canada. Model parameters for pH-dependent CEC and exchangeable cations were calculated from laboratory measurements while soil solution chemistry, including Al solubility, at the start of the simulation was taken from values obtained from lysimeter samples. Model predictions were compared with values obtained from 12 sets of soil solution collectors over the same time period. Predicted values of Ca, Mg and K in the mineral soil horizons at 25-, 75- and 125-cm depths generally fall within the 95% confidence interval of the median for the measured values. Simulated values of pH and inorganic Al are not as close to the measured values. Some error due to drift is apparent, most notably for base cations in solutions leaving the organic surface horizons, and may be attributable to decomposition of organic matter, not included in the simulation model. The results indicate that other mechanisms that release H* (nitrification, for example) and base cations (mineral weathering or mineralization of organic matter) need to be considered.     

红壤丘陵区不同植被类型土壤颗粒分形与水分物理特征

为探明红壤丘陵区不同植被对土壤分形结构及水分物理特征的改良作用与机制,运用土壤分形学和水文物理学原理与方法,以南方红壤丘陵区福建省长汀县为例,研究经济林、针阔混交林、乔灌混交林及针叶林4种植被类型土壤颗粒组成、分形维数、水分物理参数及其相关性。结果表明:1)红壤丘陵区不同植被类型土壤中以粗砂粒质量含量最高,细砂粒和石砾质量含量次之,粉黏粒质量含量较低,与裸地相比,不同植被类型具有显著提高土壤细砂砾和粉黏粒质量含量的作用,并且混交林作用程度高于纯林;2)红壤丘陵区不同植被类型具有降低土壤密度、增加土壤孔隙度的功能,针阔混交林、乔灌混交林、针叶林、经济林土壤的饱和蓄水量分别是裸地的1.20、1.16、1.14和1.10倍,表土层(0～20 cm)贮水能力好于表下土层(20～40 cm);3)土壤颗粒分形维数与土壤粉黏粒、总孔隙度、饱和蓄水量、孔隙比呈极显著正相关,与石砾质量含量、土壤密度呈极显著负相关,红壤丘陵区4种植被类型土壤均为不均匀性良好的土壤,以混交林土壤粒径分布结构较好,尤其是以针阔混交林的最好,其次是纯林的,针叶林好于经济林,表土层(0～20 cm)大于20～40 cm土层。     

皆伐对不同坡度及结构的林分土壤理化性状的影响

选择人工林伐区3种不同坡度和4种不同结构林分的林地作为试验地,研究分析各种林地皆伐作业前后土壤理化性状的变化情况.结果表明:皆伐后除土壤容重和结构体破坏率2项指标增大外,其余土壤理化性质指标均下降.土壤持水性能变差,孔隙度减小,养分含量降低,且土壤理化性质的变化幅度与林地坡度大小及林分结构有关.主成分分析结果表明:皆伐对不同坡度林地土壤理化性质的干扰程度,由大到小依次为30°的林地、23°的林地和16°的林地;皆伐对不同结构林分林地土壤理化性状的干扰影响,由大到小依次为短轮伐期阔叶林(尾叶桉纯林)林地、杉阔混交林林地、马杉混交林林地和杉木纯林林地.从有利于环境保护,减少采伐作业对不同坡度和不同结构林分林地土壤理化性状影响的角度,提出了相应的技术措施.