Simulation of the water and nitrogen balances of forests within a catchment in the northeastern German lowlands

The simulation model FOREST-BGC was used to calculate the regional water and nitrogen balances of coniferous and deciduous forests within the Stöbber catchment area over a period of 4 years. This catchment area is located in the northeastern German lowlands. The forest inventory database of the Landesforstanstalt Eberswalde served as a basis for the estimation of initial values of the forest stands and the soil conditions. The mean annual precipitation rate of the calculation period was 560 mm a^–1, the overall mean annual rate of the calculated interception loss was 178 mm a^–1. Furthermore, a mean annual transpiration rate of 329 mm a^–1 and a mean annual soil water discharge of 77 mm a^–1 were calculated by the model. The simulation of nitrogen leaching resulted in a mean annual rate of 7 kg N ha^–1 a^–1. Some simulation results are compared with measurements, and the database used for the estimation of the model initial values as well as for the model calibration is discussed. Additionally, an evaluation of the model performance was carried out for the purposes of our study. Due to the results of this evaluation, the model algorithms of the nitrogen turnover processes, especially in the soil, seem to be too simple and inappropriate for a realistic calculation of the nitrogen budget of forest ecosystems.     

Microclimate in agroforestry systems in central Amazonia: does canopy closure matter to soil organisms?

Microclimate was recorded and soil organisms were collected 1997-1999 in ecosystem stands of contrasting structure in central Amazonia (a primary forest, a 12-year secondary forest, two different agroforestry systems, a rubber tree (Hevea brasiliensis) plantation, and a peach palm (Bactris gasipaes) monoculture with a densely closed canopy). The aim was to look at the effects of canopy closure on microclimate and soil organisms. Monthly maxima temperature, average air and soil temperatures, and saturation deficit were highest in September 1997, and total annual rainfall in 1997 was 12-28% lower than in the other study years. The monthly average litter temperatures were consistently 2-4 °C higher in the plantation sites than in the rainforest and the secondary forest, and temperatures on single days (not the monthly averages) in the plantations were up to 10 °C higher than in the primary forest. The highest average litter and soil temperatures and the highest temperature maxima were recorded in the agroforestry plantations. Canopy closure strongly determined the litter temperatures in the sites. Soil macrofauna biomass was also strongly correlated to canopy closure (linear regression, P = 0.05). We conclude that a well developed canopy effectively protects the soil macrofauna from high temperature variation and drought stress. Therefore, optimizing these agroforestry systems for canopy closure may contribute to a better management of the beneficial soil decomposer community. This revised version was published online in June 2006 with corrections to the Cover Date.     

Validation of the tetrasensor honey test kit for the screening of tetracyclines in honey

Regarding anti-infectious agents, no maximum residue limits are fixed for honey in the European legislation. Discussions are being conducted in order to set working limits at the European level; for example, for tetracyclines, 20 microg/kg was proposed. The Tetrasensor Honey test kit is a receptor-based assay using dipsticks for a rapid screening (30 min) of honey on the presence of tetracyclines. The test was validated according to Commission Decision 2002/657/EC. The test detects tetracycline, oxytetracycline, chlortetracycline, and doxycycline in honey in a specific and sensitive way. Depending on the type of tetracycline, detection capabilities (CCbeta) between 6 and 12 microg/kg were obtained (4-7 microg/kg for dried dipsticks). The test is rugged and participation with the test in an international ring trial gave compliant results. It can be concluded that the Tetrasensor Honey test kit is a simple and reliable test that can even be used at the production site.     

Evaluation of a vessel-sealing device for laparoscopic granulosa cell tumor removal in standing mares

OBJECTIVE: To describe a laparoscopic technique for granulosa cell tumor removal using a vessel sealing device (LigaSuretrade mark) in standing mares. STUDY DESIGN: Retrospective study. ANIMALS: Eight mares (8-24 years old; weighing, 406-525 kg). METHODS: Before surgery, ovarian size and adjacent body wall thickness was determined by ultrasonography. Mares were sedated and after local anesthesia (inverted L and local infiltration), laparoscopic cannulation was performed without insufflation. The mesovarium was anesthetized and the LigaSure instrument applied to the mesovarium for hemostasis and resection to remove the affected ovary. Mares were hospitalized for 24 hours before discharge. RESULTS: Median ovarian diameter was 10.5 cm (range, 6-14 cm). Median surgery time was 75 minutes (range, 40-180 minutes). Hemostasis was achieved using the LigaSure device in all mares. Median length of the abdominal wall incision made to remove the ovary was 13 cm (range, 5-17 cm); no incisional complications occurred. CONCLUSIONS: The LigaSure vessel sealing device provided adequate hemostasis for removal of larger neoplastic ovaries in standing mares. CLINICAL RELEVANCE: Concerns of ligature placement can be alleviated by use of the LigaSure device and standing laparoscopic technique provides excellent observation of the surgical field ensuring hemostasis.     

Sugar fragmentation in the maillard reaction cascade: formation of short-chain carboxylic acids by a new oxidative alpha-dicarbonyl cleavage pathway

The formation of short-chain carboxylic acids was studied in Maillard model systems (90 degrees C, pH 6-10) with emphasis on the role of oxygen and water. The total amount of acetic acid formed did not depend on the reaction atmosphere. In the presence of labeled dioxygen or water (18O2, H2 17O), labeled oxygen was partially incorporated into acetic acid. Thermal treatment of 1-deoxy-d-erythro-2,3-hexodiulose (1) and 3-deoxy-d-erythro-hexos-2-ulose in the presence of 17O-enriched water under alkaline conditions led to acetic and formic acid, respectively, as indicated by 17O NMR spectroscopy. The suggested mechanism involves an oxidative alpha-dicarbonyl cleavage leading to an intermediary mixed acid anhydride that releases the acids, e.g., acetic and erythronic acid, from 1. Similarly, glyceric and lactic acids were formed from 1-deoxy-3,4-hexodiuloses, corroborated by complementary analytical techniques. This paper provides for the first time evidence for the direct formation of acids from C6-alpha-dicarbonyls by an oxidative mechanism and incorporation of a 17OH group into the carboxylic moiety. The experimental data obtained support the coexistence of at least two newly described reaction mechanisms leading to carboxylic acids, i.e., (i) a hydrolytic beta-dicarbonyl cleavage as a major pathway and (ii) an alternative minor pathway via oxidative alpha-dicarbonyl cleavage induced by oxidizing species.     

Facilitated cross-species transmission of prions in extraneural tissue

Prions are infectious pathogens essentially composed of PrP(Sc), an abnormally folded form of the host-encoded prion protein PrP(C). Constrained steric interactions between PrP(Sc) and PrP(C) are thought to provide prions with species specificity and to control cross-species transmission into other host populations, including humans. We compared the ability of brain and lymphoid tissues from ovine and human PrP transgenic mice to replicate foreign, inefficiently transmitted prions. Lymphoid tissue was consistently more permissive than the brain to prions such as those causing chronic wasting disease and bovine spongiform encephalopathy. Furthermore, when the transmission barrier was overcome through strain shifting in the brain, a distinct agent propagated in the spleen, which retained the ability to infect the original host. Thus, prion cross-species transmission efficacy can exhibit a marked tissue dependence.     

Short‐time clay‐mineral evolution in a soil chronosequence in Oléron Island (France)

Major weathering sequences in soils are well established; however, knowledge on rates of mineral transformations remains unknown, because it is often difficult to date precisely soil processes. This work was carried out on soils developed on recent (< 188 y) sand dunes on the W coast of Oléron Island (France). The coast has been protected against marine and wind erosion by constructing five consecutives barriers close to the coastline since 1820 (1820, 1864, 1876, 1889, 1948) defining the maximum age of the soil parent material, as before the areas between the barriers were under water. Soils on the older dunes have low clay content (> 94% of sand) and exhibit a bleached E horizon that overlies a yellowish brown B horizon. The process responsible for their formation is podzolization promoted by the high permeability of the material and complexing organic matter produced by coniferous vegetation. Initial mineralogy of C horizons is homogenous and constituted of chlorite, illite, illite/smectite mixed‐layer minerals, and kaolinite, quartz, calcite (≈ 8% related to shell fragments), and feldspars. The initial clay‐mineral assemblage of the E horizons is dominated by illite (well‐crystallized WCI and poorly crystallized PCI) and chlorite. With progressive podzolization, poorly crystallized illite is first transformed to illite/smectite mixed‐layer minerals and in a further step into smectite. In addition, transformation of well‐crystallized illite leads to formation of ordered illite/smectite mixed‐layer minerals in the E horizons, which is not commonly described in soils. In the B horizons, illite/smectite mixed‐layer minerals are present with traces of smectite, as well as Al and Fe oxi‐hydroxides as revealed by DCB and oxalate chemical extractions. This chronosequence illustrates that over short distances and short time (< 188 y) intense mineral weathering and soil development occur. Major clay‐mineral changes occur between 132 and 188 y in agreement with development of the pine forest producing acidic litter.     

Do individual-tree growth models correctly represent height:diameter ratios of Norway spruce and Scots pine?

Height:diameter ratios are an important measure of stand stability. Because of the importance of height:diameter ratios for forest management, individual-tree growth models should correctly depict height:diameter ratios. In particular, (i) height:diameter ratios should not exceed that of very dense stands, (ii) height:diameter ratios should not fall below that of open-grown trees, (iii) height:diameter ratios should decrease with increasing spacing, (iv) height:diameter ratios for suppressed trees should be higher than ratios for dominant trees. We evaluated the prediction of height:diameter ratios by running four commonly used individual-tree growth models in central Europe: BWIN, Moses, Silva and Prognaus. They represent different subtypes of individual-tree growth models, namely models with and without an explicit growth potential and models that are either distance-dependent (spatial) or distance-independent (non-spatial). Note that none of these simulators predict height:diameter ratios directly. We began by building a generic simulator that contained the relevant equations for diameter increment, height increment, and crown size for each of the four simulators. The relevant measures of competition, site characteristics, and stand statistics were also coded. The advantage of this simulator was that it ensured that no additional constraint was being imposed on the growth equations, and that initial conditions were identical. We then simulated growth for a 15- and 30-year period for Austrian permanent research plots in Arnoldstein and in Litschau, which represent stands at different age-classes and densities. We also simulated growth of open-grown trees and compared the results to the literature. We found that the general pattern of height:diameter ratios was correctly predicted by all four individual-tree growth models, with height:diameter ratios above that of open-grown trees and below that of very dense stands. All models showed a decrease of height:diameter ratios with age and an increase with stand density. Also, the height:diameter ratios of dominant trees were always lower than that of mean trees. Although in some cases the observed and predicted height:diameter ratios matched well, there were cases where discrepancies between observed and predicted height:diameter ratios would be unacceptable for practical management predictions.