Bodensystematik und Bodenklassifikation Teil I: Grundbegriffe

Soil systematics and classification systems Part I: Fundamentals Soil‐ordering systems are primarily based and developed on one of two underlying principles: They are either categorized according to soil‐forming processes, or the formation of categories develops by chosen parameters. This perspective has already been established in the literature, though it is often confusing as many terms are defined and applied differently. In this contribution, the various definitions of systematics, classification, taxonomy, and identification will be clearly differentiated and summarized. The core of our work is to clearly define and contrast three terms: systematics, classification, and identification. Systematics is the fundamental scientific and deductive ordering of objects into systematic units. The purpose of this approach is to organize the entire spectrum of knowledge within a discipline into a transparent and manageable form. Classification, in direct contrast to systematics, is goal‐oriented and an inductive ordering of objects. Thus, the ordering scheme consists of classes which are clearly parameterized. Identification is the ordering of new objects into an already existing systematics or classification system. Close attention is paid to both the differences and the similarities between a systematics and a classification system, especially pertaining to their practical applications. The identification requires that the category‐forming characteristics can be measured (e.g., for soil systematics, these are the soil‐forming processes and factors). Currently, it is unfortunately not feasible to objectively quantify most soil‐forming processes. Thus, most attempts at categorizing soils by systematics are hypothetical and highly subjective in nature. The resulting identification derived from the soil systematics approach is open to questions and contestable, since a graded measuring system does not yet exist to verify these determinations. In contrast, a soil‐classification system does allow an objective soil‐profile identification, although such systems are conceived pragmatically and designed for a practical purpose (e.g., not scientifically based on process intensities). Unfortunately, such a classification system cannot be applied as a universal scientific categorization system due to this method of conception. Both categorization approaches are required in soil science in order to satisfy both the practical and the scientific aspects of the field. However, substantial research must be done to complete and verify systematics. The only viable short‐term solution is through the development of a graded classification system where the categories of the system are directly derived from the current systematics approach. In the long run both the exact investigation and the detailed modeling of the soil‐forming processes are inevitable.     

Variation of Pythium-induced cocoyam root rot severity in response to soil type

In Cameroon, andosols are suspected to be suppressive to cocoyam (Xanthosoma sagittifolium) root rot disease (CRRD) caused by the Oomycete pathogen Pythium myriotylum. To determine factors involved in disease suppressiveness, andosols were studied in comparison to ferralsols known to be disease-conducive. Soil samples were collected from six sites of which three were in andosols around Mount Cameroon (Boteva, Njonji, and Ekona) and the three others in ferralsols (Bakoa, Lapkwang, and Nko’o canane). Greenhouse plant experiments were used to assess soil suppressiveness. Soils were artificially infested with two levels of P. myriotylum inoculum (100 and 300 mycelia strands g⁻¹ soil) prior to planting cocoyam. Disease severity was significantly higher in ferralsols than in andosols. Andosols partly lost their suppressiveness as a result of autoclaving and could recover suppressiveness following recolonisation by their original microflora. Soil microbial groups implicated in the disease suppression were investigated by assessing the effect of fungicide, bactericide, and pasteurisation on andosol suppressiveness. Andosols suppressiveness was significantly reduced following pasteurisation and treatment with fungicide and bactericide. The possible influence of microbial biomass on andosol suppressiveness was investigated by comparing microbial populations of suppressive andosols to those in andosols that had lost suppressiveness. A comparative analysis of suppressive and conducive soil properties was performed to identify soil variables, which may contribute to soil suppressiveness. Soil chemical analysis results showed that organic matter content was higher in andosols than in ferralsols. In addition, the content of mineral nutrients such as Ca, K, Mg and N, was higher in andosols than in ferralsols. These soil variables negatively correlated with disease severity. By contrast, sand and clay, which were higher in ferralsols than in andosols, were positively related to disease severity. This study has confirmed the suppressive nature of andosols from Mount Cameroon to CRRD. The results suggest that high organic matter content is likely mediating P. myriotylum suppression in andosols by improving soil structure, increasing soil nutrient content and microbial biomass, and sustaining microbial activity.     

Genetic diversity in sweetpotato [Ipomoea batatas (L.) Lam.] in relationship to geographic sources as assessed with RAPD markers

Available evidence shows that sweetpotato originated from either Central or South American lowlands with subsequent dispersal to North America, Europe, Africa, Asia and the pacific islands. A total of 71 polymorphic RAPD molecular markers were used to assess the genetic relationships amongst 74 sweetpotato varieties originating from a total of 23 sweetpotato producing countries within six geographical regions, namely, South America, Central America/Caribbean, United States of America (USA), East Africa, Asia and Oceania. An Analysis of Molecular Variance (AMOVA) indicated that 93.4% of the total variance was due to the differences between genotypes within regions. The difference between regions was significant (P < 0.001) but only contributed 6.6% to the variance. Genetic distance (PhiST) calculated with AMOVA and multidimensional scaling (MDS) revealed that the South American and the Central American/Caribbean genotypes formed two separate clusters. East African varieties, which have unique characteristics from other traditional varieties, were distinct from other traditional varieties from South America and Oceania. These results support the reported hypothesis of the origin and dispersal of the sweetpotato and indicate that the primary centre of diversity probably has two distinct genepools. It is proposed that the dispersal of the sweetpotato from its origin may have mainly involved varieties from Central America/Caribbean as opposed to varieties from South America. There is an indication that new genepools may be evolving in Africa and Asia due to hybridisation and adaptation to the local environments.     

Feeding deterrence and contact toxicity of Stemona alkaloids-a source of potent natural insecticides

On the basis of chronic feeding bioassays with neonate larvae of Spodoptera littoralis reared on an artificial diet, the methanolic leaf and root extracts from Stemona collinsae displayed very high insect toxicity compared to those of two Aglaia species, a commercial Pyrethrum extract, and azadirachtin, whereas S. tuberosa extracts demonstrated low activity in roots and no activity in leaves. Beyond that, in leaf disk choice tests against fifth instar larvae, S. collinsae showed strong antifeedant activity, whereas S. tuberosa was characterized by remarkable repellency. The anti-insect properties of both species were based on pyrrolo[1,2-a]azepine alkaloids, from which didehydrostemofoline (asparagamine A) was the major compound of the roots of S. collinsae, exhibiting the highest toxicity in feeding assays. Saturation and hydroxylation of the side chain in the co-occurring stemofoline and 2'-hydroxystemofoline, respectively, led to an increasing loss of activity. Contact toxicity tests with stemofoline and didehydrostemofoline exhibited even higher activities than those of Pyrethrum extract. Tuberostemonine was the dominating alkaloid in the roots of S. tuberosa, showing outstanding repellency but no toxic effects.     

Reptile diversity and rodent community structure across a political border

The peace treaty between Israel and Jordan found the Arava desert ecosystem, shared by the two countries, in a state of developmental dichotomy. On the Israeli side, vast lands have been settled and transformed into agricultural fields, while the Jordanian side has remained relatively intact and inhabited by only a few traditional and pastoral societies. This study examined the effect of different landscape units and proximity to agriculture on reptile diversity and rodent community structure on both sides of the border. It appears that in addition to the effect of proximity to agricultural fields and landscape habitat, the border between the two countries may play a role in determining diversity on the respective sides. While reptile abundance was generally higher on the Israeli side of the border, diversity was found to be significantly higher on the Jordanian side. Rodent community structure also revealed significant differences between the two sides of the border, mainly due to the more favorable conditions for psammophilic gerbils in Jordan. When comparing Western society with pastoral traditional society, it appears that development activities of the former have altered diversity and community structure of the taxa studied in the Arava. We suggest that in addition to the effects of habitats and human disturbances, such as modern agricultural practices, cultural differences between societies should be considered when conservation plans are developed for cross-border ecosystems.     

Distribution, status, and conservation needs of Asian elephants (Elephas maximus) in Lampung Province, Sumatra, Indonesia

In the mid 1980s, Asian elephant (Elephas maximus) populations were believed to persist in 44 populations on the Indonesian island of Sumatra. Twelve of these populations occurred in Lampung Province, but our surveys revealed that only three were extant in 2002. Causal factors underlying this decline include human population growth, changes in land use, and human-elephant conflict. Nevertheless, our surveys in the Province’s two national parks, Bukit Barisan Selatan and Way Kambas, produced population estimates of 498 (95% CI = [373, 666]) and 180 (95% CI = [144, 225]) elephants, respectively. The estimate for Bukit Barisan Selatan is much larger than previous estimates; the estimate for Way Kambas falls between previous estimates. The third population was much smaller and may not be viable. These are the first estimates for Southeast Asian elephant populations based on rigorous sampling-based methods that satisfied the assumptions of the models used, and they suggest that elephant numbers in these parks are of international importance. While our results suggest that Sumatra’s remaining elephant populations may be larger than expected, they also suggest that the future for these animals is bleak. Human-elephant conflict was reported around all three areas in Lampung and their elephant populations are currently threatened by habitat loss and poaching. Local solutions are possible, but will require much greater commitment by all stakeholders.     

Methods for evaluating human impact on soil microorganisms based on their activity,biomass, and diversity in agricultural soils

The present review is focused on microbiological methods used in agricultural soils accustomed to human disturbance. Recent developments in soil biology are analyzed with the aim of highlighting gaps in knowledge, unsolved research questions, and controversial results. Activity rates (basal respiration, N mineralization) and biomass are used as overall indices for assessing microbial functions in soil and can be supplemented by biomass ratios (C : N, C : P, and C : S) and eco‐physiological ratios (soil organic C : microbial‐biomass C, qCO₂, qN_min). The community structure can be characterized by functional groups of the soil microbial biomass such as fungi and bacteria, Gram‐negative and Gram‐positive bacteria, or by biotic diversity. Methodological aspects of soil microbial indices are assessed, such as sampling, pretreatment of samples, and conversion factors of data into biomass values. Microbial‐biomass C (µg (g soil)^–1) can be estimated by multiplying total PLFA (nmol (g soil)^–1) by the F_PLFA‐factor of 5.8 and DNA (µg (g soil)^–1) by the F_DNA‐factor of 6.0. In addition, the turnover of the soil microbial biomass is appreciated as a key process for maintaining nutrient cycles in soil. Examples are briefly presented that show the direction of human impact on soil microorganisms by the methods evaluated. These examples are taken from research on organic farming, reduced tillage, de‐intensification of land‐use management, degradation of peatland, slurry application, salinization, heavy‐metal contamination, lignite deposition, pesticide application, antibiotics, TNT, and genetically modified plants.     

Microbial processes and the site of N2O production in a temperate grassland soil

To understand nitrous oxide (N₂O) emissions from terrestrial ecosystems it is necessary to understand the processes leading to N₂O production. Here, for the first time, results are presented which identify in situ the processes of N₂O production in a temperate grassland soil. A small portion of the nitrogen (N) applied in the summer to the grassland soil was rapidly transported below the main rooting zone (>20 cm) and resulted in large N₂O productions at depths of 20-50 cm. Preferential pathways must have been responsible for this movement because the soil conditions were not conducive to leaching by piston flow. The N₂O was entirely produced by nitrate (NO₃⁻) reduction which was surprising because the bulk soil was aerobic. Therefore, reduction processes can operate during times of the year when it is least expected and cause large N₂O concentrations deep in the soil profile.     

Fresh Israeli Jaffa blond (Shamouti) orange and Israeli Jaffa red Star Ruby (Sunrise) grapefruit juices affect plasma lipid metabolism and antioxidant capacity in rats fed added cholesterol

The bioactivity of Israeli Jaffa blond (Shamouti) fresh orange and Israeli Jaffa red Star Ruby (Sunrise) grapefruit juices was investigated in vitro and in vivo. The contents of bioactive compounds of these juices were determined. The influence of bioactive compounds on plasma lipids and plasma antioxidant activity in rats fed cholesterol-containing and cholesterol-free diets was assessed. Significant differences in the contents of dietary fibers were not found. The contents of total polyphenols, flavonoids, and anthocyanins in fresh orange and grapefruit juices were 962.1 +/- 27.2 and 906.9 +/- 27.1; 50.1 +/- 3.3 and 44.8 +/- 3.2; and 69.9 +/- 5.6 and 68.7 +/- 5.5 microg/mL, respectively. The antioxidant potential measured by the scavenging activity against nitric oxide, the beta-carotene-linoleate model system (beta-carotene), and the 1,1-diphenyl-2-picrylhydrazyl and 2,2'-azino-bis(3-ethyl-benzothiazoline-6-sulfonic acid) diamonium salt assays was higher in orange juice but not significantly. A high level of correlation between contents of total polyphenols and flavonoids and antioxidant potential values of both juices was found. Diets supplemented with orange and to a lesser degree with grapefruit juices improved plasma lipid metabolism only in rats fed added cholesterol. However, an increase in the plasma antioxidant activity was observed in both groups. In conclusion, fresh orange and grapefruit juices contain high quantities of bioactive compounds, which guarantee their high antioxidant potential, and the positive influence on plasma lipid metabolism and plasma antioxidant activity could make fresh orange and grapefruit juices a valuable supplement for disease-preventing diets.