Spatial prediction of forest stand variables

This study aims at the development of a model to predict forest stand variables in management units (stands) from sample plot inventory data. For this purpose we apply a non-parametric most similar neighbour (MSN) approach. The study area is the municipal forest of Waldkirch, 13 km north-east of Freiburg, Germany, which comprises 328 forest stands and 834 sample plots. Low-resolution laser scanning data, classification variables as well rough estimations from the forest management planning serve as auxiliary variables. In order to avoid common problems of k-NN-approaches caused by asymmetry at the boundaries of the regression spaces and distorted distributions, forest stands are tessellated into subunits with an area approximately equivalent to an inventory sample plot. For each subunit only the one nearest neighbour is consulted. Predictions for target variables in stands are obtained by averaging the predictions for all subunits. After formulating a random parameter model with variance components, we calibrate the prior predictions by means of sample plot data within the forest stands via BLUPs (best linear unbiased predictors). Based on bootstrap simulations, prediction errors for most management units finally prove to be smaller than the design-based sampling error of the mean. The calibration approach shows superiority compared with pure non-parametric MSN predictions.     

Entomopathogens (Beauveria bassiana and Steinernema carpocapsae) for biological control of bark-feeding moth Indarbela dea on field-infested litchi trees

BACKGROUND: The bark-feeding moth Indarbela dea (Swinhoe) is one of the major pests of litchi (Litchi chinensis Sonn.) in Asia. Effects on larval mortality and web production were tested by repeated, single and combined tree trunk applications of the entomopathogenic fungus Beauveria bassiana (Bals.) Vuill. and the entomopathogenic nematode Steinernema carpocapsae (Weiser). Two separate application trials were conducted in different seasons on young and older larvae respectively. RESULTS: In both trials, complete or nearly complete mortality (100% and 95%) of the larvae was achieved 3 weeks after application of S. carpocapsae alone and 2 weeks after the combined application of B. bassiana and S. carpocapsae (100% in both trials). However, in the combined application, all larvae were killed by one treatment, while the application of S. carpocapsae alone needed to be repeated to reach the same result. The effectiveness of the combined entomopathogen application and of the application of S. carpocapsae alone was not influenced by the age of the larvae. However, the single applications of B. bassiana were only effective on young larvae. In both trials, web production of surviving larvae was very significantly reduced by the application of S. carpocapsae in single and combined treatments. CONCLUSIONS: As the results show, only one application is necessary in the combined application of the two entomopathogens to control I. dea, which implies that such treatment is probably the economically most relevant solution.     

Ground water preservation by soil protection: Determination of tolerable total Cd contents and Cd breakthrough times

Taking Cd as an example we introduce a procedure to estimate tolerable total content of heavy metals in soils with regard to a specific ground water quality criterion. Furthermore, we present a piston‐flow approach to estimate breakthrough times of a sorptive solute to the ground water. Both procedures are applied to the sandy soils in the 4300 ha wastewater irrigation area Braunschweig, Germany. Applicability of these procedures is tested by numerical simulations. The calculated breakthrough times of Cd for an input concentration of 3 μg L⁻¹ and a mean water flux density of 570 mm yr⁻¹ varies, as a function of depth of water table and sorption characteristics, between 10 and 805 years (mean = 141 years). The deviation between the piston‐flow approach and the numerical simulation is on the average 1.6%. We determined a mean tolerable total Cd content of 0.61 mg kg⁻¹ with regard to a ground water quality criterion of 3 μg L⁻¹. The limit of the German sewage sludge regulation (AbfKlärV, 1992) of 1 mg Cd kg⁻¹ exceeds the calculated tolerable total content in 90% of the investigated Ap horizons. Moreover, the results of the numerical simulations show that the limit of 1 mg Cd kg⁻¹ would lead to a concentration in seepage water significantly above 8 μg Cd L⁻¹. We conclude that in the sandy soils of the wastewater irrigation area the current limit of 1 mg Cd kg⁻¹ is not sufficient to keep the Cd concentration in seepage water below 3 μg L⁻¹ and, thus, to ensure ground water protection in the long run.     

Evaluating the most suitable nonlinear growth model for turbot (Scophthalmus maximus) in aquaculture 2 (weight application): Multi‐criteria model selection and growth prediction

Seeking the most suitable model to describe the growth of turbot, we analysed growth data of two different turbot (Scophthalmus maximus) strains reared communally in a recirculating aquaculture system. We fitted 10 different nonlinear growth models to individual weight gain data (n = 2,010) during the grow‐out phase. Analyses were carried out for each strain, for sexes within strains and for a pooled data set containing both strains and sexes. To assess the model performance, three different criteria are used. Further, a growth‐simulation was performed to evaluate the shape of the generated curve. This way we could assess the capability of the models to predict future growth. The 3‐parametric Gompertz model achieved the best fit in 42.9% of all cases tested and the lowest Bayesian information criterion in 100% of cases. The model produced realistically shaped curves and asymptotic values matching the biological attributes of the species. In contrast, 5‐parametric functions projected unrealistically shaped curves and predicted improbable mature sizes. Our results show that increasing number of parameters do not lead to increasing goodness of fit, but tend to result in overfitting, and demonstrate the advantages of the 3‐parametric Gompertz model for describing the growth of turbot.     

Systemic infection in European perch with thermoadapted virulent Aeromonas salmonicida (Perca fluviatilis)

In non‐salmonid fish, Aeromonas salmonicidacan cause local infections with severe skin ulcerations, known as atypical furunculosis. In this study, we present a systemic infection by a virulent A. salmonicidain European perch (Perca fluviatilis).This infection was diagnosed in a Swiss warm water recirculation aquaculture system. The isolate of A.  salmonicida encodes a type three secretion system (TTSS) most likely located on a plasmid similar to pAsa5/pASvirA, which is known to specify one of the main virulence attributes of the species A. salmonicida. However, the genes specifying the TTSS of the perch isolate show a higher temperature tolerance than strains isolated from cold‐water fish. The function of the TTSS in virulence was verified in a cytotoxicity test using bluegill fry and epithelioma papulosum cyprinid cells.     

Denitrification in drained and rewetted minerotrophic peat soils in Northern Germany (Pohnsdorfer Stauung)

This study was conducted to assess the nitrogen removal potential of a minerotrophic peatland in Northern Germany, where hydrological conditions were partly restored in the beginning of the 1990s. Actual denitrification and the effect of nitrate (NO₃^—) and glucose additions on denitrification rates were determined in two flooded and one drained histosols in spring and summer 1998. In the flooded soils, denitrification was insignificant, but the drained field emitted significant rates. Additions of NO₃^— stimulated denitrification at all sites in spring and summer, whereas glucose additions had no effect. Low NO₃^— concentration in floodwater was obviously limiting denitrification in the flooded soils. In the drained soil, a coupled nitrification/denitrification might explain the low but significant denitrification rates. No spontaneous production of nitrous oxide occurred in the flooded soils, whereas at the drained site an increase in spontaneous nitrous oxide concentration was measured during incubation in the summer samples. The suggested introduction of NO₃^— rich water from a stream flowing through the area would apparently induce denitrification in the flooded fields.     

Assessment of Highly Polluted Fluvisol in the Spittelwasser Floodplain Based on National Guideline Values and MNA-Criteria (11 pages)

Background, Goal and Scope

Nearly all large European rivers have been used as disposal pathways for several unwanted substances. Deposition of the contaminated solids occurs in regions of slack water and also during floods in adjacent floodplains. As a result of the recurrent input, most of the floodplains in central Europe are contaminated by manifold inorganic and organic pollutants, representing a risk for both plants and groundwater at the site, and for areas downstream. The aim of the present paper is to demonstrate and assess the sink and source functions of a highly contaminated 'fluvisol' (= alluvial soil) for inorganic and persistent organic pollutants. The extent of contamination is described on the basis of national guidelines. These results are further discussed on the basis of the 'monitored natural attenuation' (MNA) potential, i.e., with respect to the requirements for the cheapest problem solution for large scale contamination of floodplains. The MNA potential is assessed according to several lines of evidence such as contaminant burial, mechanical and chemical mobility, transformation to less toxic forms, and dilution due to dispersion.

Methods

The existing inorganic and organic pollutant status and the ecotoxicological potential of the Spittelwasser floodplain near Jeßnitz was documented by analysing several element and compound depth profiles of a typical alluvial soil site. Geochemical analyses were performed on solid material and soil solution according to standard procedures. In laboratory experiments monoliths were continuously irrigated with deionised water and the leachate was analysed weekly. In addition to the geochemical, the ecotoxicological status of the samples was studied using different biotests for the dissolved and the solid phase.

Results

The measured alluvial soil profile is severely contaminated with numerous inorganic and organic pollutants. Highest enrichment factors according to the catchment based, element specific geological background were found for Hg (402), Pb (8.9), Cr (7.1) and Cd (6.3). Assessment was made of the hazard potential of both the solid material and the soil solution according to the German Federal Soil Protection and Contaminated Sites Ordinance (BBodSchV). Relating to the respective maximum contents in the soil profile, the overstepping of BBodSchV trigger values is highest for Hg with a coefficient of 49.0 followed by Cd (14.3), Pb (12.2), Zn (7.3), Cr (5.9) and Cu (3.6). Pollutant concentrations in the soil solution exceed the threshold values for Cd, Cu and Zn by factors of 6.3 to 12. While DDT is retained in the topsoil, there is a considerable translocation of HCH towards deeper horizons.

Discussion

The algae test confirms a strong toxicity in the top layer of the soil profile. In contrast, no such toxic reactions were indicated by the luminescent bacteria test and the Daphnia test at this depth. However, the deeper layers (10 - 100 cm) show a toxic reaction by the Daphnia test, thus indicating a relevant translocation of contaminants.

Conclusions and Perspectives

The Spittelwasser floodplain represents a significant sink for inorganic and persistent organic pollutants. Simultaneously, the area is a relevant secondary source of dissolving contaminants like heavy metals and HCH. Although strict criteria in the lines of evidence for applying MNA are not fulfilled, it can be stated that the alluvial soil offers a high natural retention potential for As, Hg, DDT, and PCDD/F. These pollutants are firmly retained and are not found in the soil leachate. This meets the demands of the EC-WFD for pollutant retention close to their primary source. But for agricultural use and groundwater recharge the natural attenuation potential of the soils in the Spittelwasser area will not be sufficient to achieve acceptable conditions medium-term. The main problem for the dissemination of pollutants is not chemical stability but mechanical dispersion. This is particularly the case for PCDD/F, with concentrations of more than 10,000 ng/kg I-TEQ in the upper Spittelwasser soil layers. Dispersion processes can result in a wide spatial contamination of downstream floodplains.     

Low importance for a fungal based food web in arable soils under mineral and organic fertilization indicated by Collembola grazers

We investigated the Collembola community at an arable field where mineral and organic fertilizers have been applied at low and high rates for 27 years. As food resources for Collembola, the soil microbial community was analyzed using phospholipid fatty acids (PLFAs). A special focus was put on AM fungi, which were estimated by the marker 16:1ω5 in PLFA (viable hyphae) and neutral lipid fatty acid (NLFA – storage fat in spores) fractions. Additionally, whole cellular lipids in crop plant tissues and manure were assessed. Greater Collembola species richness occurred in plots where mineral fertilizer was added. In contrast, soil microbial biomass including AM fungal hyphae increased with addition of organic fertilizer, while the amount of AM fungal spores and biomass of saprotrophic fungi were not affected by fertilizer type. The lipid pattern in wheat roots was altered by fertilizer type, application rate and their interaction, indicating different rhizosphere communities. In sum, the availability and composition of food resources for Collembola changed considerably due to farm management practice. The major diet of three dominant Collembola species, Isotoma viridis, Willemia anophthalma and Polyacanthella schäffer was determined by lipid profiling. Multivariate analysis demonstrated species specific lipid patterns, suggesting greater importance of species than management practice on the diet choice. Nevertheless, feeding strategy was affected by fertilizer type and availability of resources, as trophic biomarker fatty acids indicated feeding on wheat roots (and to some extent saprotrophic fungi) with mineral and a shift to soil organic matter (litter, detritus) with organic fertilization. Although AM fungi dominated the soil fungal community, the AMF marker 16:1ω5 was not detected in Collembola lipids, indicating that these were not consumed. The very low amount of saprotrophic fungi in the soil and the fact that Collembola as major fungal grazers did not feed on AM fungi indicates that the fungal energy channel in the investigated arable field is of little importance to the faunal food web.     

Growth response of 98 barley (Hordeum vulgare L.) genotypes to elevated CO2 and identification of related quantitative trait loci using genome‐wide association studies

Elevated CO₂ (eCO₂) concentrations can stimulate crop growth, but little is known about intraspecific variability in the response to eCO₂ and the underlying genetics in cereals. Field experiments over two years with 98 barley genotypes were conducted in open‐top chambers (OTCs) under ambient CO₂ (400 ppm) and eCO₂ (700 ppm) concentrations. At crop maturity, different fractions of aboveground biomass (AGB) were measured, and genome‐wide association studies (GWASs) were conducted to identify quantitative trait loci (QTL). Averaged across all genotypes, eCO₂ significantly enhanced AGB by 15%, while the increase in culm and ear biomass alone was not significant. The AGB response to eCO₂ of the individual genotypes ranged from c. ?36% to +95% compared with ambient CO₂ (aCO₂), showing a large variability of growth responses. In GWAS, 51 associations between SNP markers and the relative changes (eCO₂/aCO₂) in biomass were detected on different chromosomes. Loci potentially involved in biomass alterations under eCO₂ were identified. The wide range of variability in responses might be exploited by marker‐based breeding for climate‐resilient barley.