Effects of the extreme drought in 2003 on soil respiration in a mixed forest

We present a field study on the drought effects on total soil respiration (SR_t) and its components, i.e., “autotrophic” (SR_a: by roots/mycorrhizosphere) and “heterotrophic” respiration (SR_h: by microorganisms and soil fauna in bulk soil), in a mature European beech/Norway spruce forest. SR_a and SR_h were distinguished underneath groups of beech and spruce trees using the root exclusion method. Seasonal courses of SR_a and SR_h were studied from 2002 to 2004, with the summer of 2003 being extraordinarily warm and dry in Central Europe. We (1) analyzed the soil temperature (T _s) and moisture sensitivity of SR_a and SR_h underneath both tree species, and (2) examined whether drought caused differential decline of SR_a between spruce and beech. Throughout the study period, SR_a of beech accounted for 45–55% of SR_t, independent of the soil water regime; in contrast, SR_a was significantly reduced during drought in spruce, and amounted then to only 25% of SR_t. In parallel, fine-root production was decreased during 2003 by a factor of six in spruce (from 750 to 130 mg l⁻¹ a⁻¹), but remained at levels similar to those in 2002 in beech (about 470 mg l⁻¹ a⁻¹). This species-specific root response to drought was related to a stronger decline of SR_a in spruce (by about 70%) compared to beech (by about 50%). The sensitivity of SR_a and SR_h to changing T _s and available soil water was stronger in SR_a than SR_h in spruce, but not so in beech. It is concluded that SR_a determines the effect of prolonged drought on the C efflux from soil to a larger extent in spruce than beech, having potential implications for respective forest types. This article belongs to the special issue "Growth and defence of Norway spruce and European beech in pure and mixed stands."     

Sensory irritations and pulmonary effects in human volunteers following short-term exposure to pinewood emissions

Pinewood (Pinus ssp.) is widely used for furniture and building purposes. However, despite its widespread use, information on possible human sensory irritations and pulmonary effects caused by exposure to volatile organic compounds (VOC) emitted from pinewood is sparse. For this purpose, (1) sensory irritation of eyes, nose and throat, (2) lung function parameters (FVC, FEV₁), (3) exhaled nitrogen oxide (NO) concentration, (4) eye blink frequency, and (5) sensory evaluation (using the SD method) were investigated before, after, and partly during exposure of human volunteers to emissions from pinewood panels. Fifteen healthy nonsmokers were exposed for 2 h under controlled conditions to VOCs emitted from pinewood panels in a 48 m³ test chamber. VOC concentrations were about 5 mg/ m³ (loading rate, 1 m²/m³), 8 mg/m³ (loading rate, 2 m²/m³), and 13 mg/m³ (loading rate, 3 m²/m³), respectively. Terpene and aldehyde exposure concentrations ranged from about 3.50 ± 0.51 mg/m³ and 0.07 ± 0.008 mg/m³, 5.00 ± 0.95 mg/ m³, and 0.20 ± 0.02 mg/m³ or 9.51 ± 1.10 mg/m³ and 0.21 ± 0.04 mg/m³ for loading rates of 1, 2, and 3 m²/m³, respectively. The emissions consisted predominantly of α-pinene and δ³-carene. No concentration-dependent effects before or after exposure to the emissions were measured with respect to sensory irritation, pulmonary function, exhaled NO, and eye blink frequency. Only the odor of the emissions was perceived by the study subjects, rated as being closer to “pleasant” than to “unpleasant.” In conclusion, the results of our study suggest that short-term exposure to high VOC concentrations, even up to 13 mg/m³, released from pinewood does not elicit sensory irritation or pulmonary effects in healthy humans under controlled conditions.     

有机农业对农村经济发展促进作用浅析——以新疆伊吾县有机农业发展为例

有机农业是当今世界农业日益商品化、市场化、社会化的必然选择,也是促进我国农业结构战略调整的重要途径之一.本文以新疆伊吾县有机农业发展为例,分析了有机农业对新疆的促进作用.最后,提出了加快有机农业发展的对策和建议.     

Pyrite oxidation in a sediment sample of an open-cut brown coal mine: mineral formation,buffering of acidity and modeling of cations and sulfate

Secondary reactions occurring in pyrite‒containing sediments under aerobic conditions are complex and are not fully understood. Objectives were to (i) study the formation of secondary minerals using x‒ray diffraction (XRD) and ion activity product (IAP) calculations; (ii) to obtain a budget of acidity producing and consuming processes; and (iii) to study the performance of a chemical equilibrium model (including kinetic reactions) using sequential batch experiments with varying input solutions on samples of different pyrite oxidation states. A sediment sample from the open pit coal mine Garzweiler, Germany, was oxidised in the laboratory to obtain four different pyrite oxidation states. Sequential batch experiments were carried out using H₂O, 100 mM CaCl₂ and 10 mM NaOH as input solutions. A coupled equilibria model was used to describe the experiments. The model (PHREEQC) included inorganic complexation, redox reactions, precipitation/dissolution of sparingly soluble salts, multiple cation exchange and pyrite oxidation using a simple input function. IAP calculations and XRD showed the formation of large amounts of gypsum with increasing pyrite oxidation and for the highly oxidised sample also the formation of hydroniumjarosite. The budget of acidity consuming processes followed the order (i) release of Fe(III) into the solution phase (51% of produced acidity); (ii) Al release into solution and exchangeable phases (probably mainly due to silicate weathering, 22% of produced acidity); and (iii) CEC reducing processes (11% of produced acidity). Modeling of the sequential equilibration experiments with water and CaCl₂ gave satisfactory agreements between modeled and measured pH and sorption values, indicating that the main processes governing pH and ion sorption were quite well understood. However, model results of the alkaline additions at larger pyrite oxidation states differed considerably from the experimental results.     

Release of carbon and nitrogen compounds by plant roots and their possible ecological importance+

The root-borne C- and N-flux in the plant/soil system was studied by determining the ¹⁴C- or ¹⁵N-balances in pot trials with soil as a substrate (¹⁴CO₂- or ¹⁵NH₃-application to the shoots, comparison of sterile and nonsterile treatments for quantification of root-borne substances). The following results were obtained: 1. The amount of (primary) root-borne carbon compounds released into soil was (besides root respiration) 11—20% of net-CO₂-assimilation or 13—32% of the ¹⁴C incorporated into the plants (= 1 t C · ha^—1). 5—6% of ¹⁵N assimilated by the plants were released as root-borne N compounds (= 15 kg N · ha^—1). 2. A considerable portion of the root-borne C (about 6% = 600 kg C · ha^—1) was found in the rooted soil zone at the end of the experiments (rhizodeposition). 3. (Primary) root-borne C and N compounds found in immediate vicinity of the roots (about 60—80%) were mainly water soluble, whereas most of the C and N compounds found in a greater distance were water insoluble. The water soluble exudates consisted mainly of neutral (carbohydrates) and acid fractions (organic acids). The basic fraction (amino acids) made up a small portion only. 4. The root-borne C and N compounds influenced the nutrient balance of soil and plant directly and/or indirectly via microbes (depending on species, variety and nutritional status of plants). 5. Microbes stimulated the release of C- and N-compounds, but rapidly respired 65—85% of the root-borne C-compounds, thereby putting a burden on the C-budget of the “host” plant. 6. It could be shown by the example of hup⁺ Rhizobium meliloti strains (tested by ³H₂-incorporation) and the wheat-Serratia-association, that energy efficient microbenplant systems can improve plant performance.     

Complexity and information propagation in hydrological time series of mountain forest catchments

Ecosystem analysis is typically done by determination of species composition, structural exploration, determination of matter and energy fluxes and/or system analyses based on deterministic or probabilistic/stochastic model approaches. However, regarding ecosystem dynamics, temporal structure, information content, complexity of signals, and their modifications when subsequently passing through different subsystems, have not intensively been studied to date. Structure in time series characterised by information and complexity measures may provide additional, powerful tools to analyse state and dynamics of ecosystems. Along their path through ecosystem compartments, e.g., hydrological signals are transformed in several ways, comprising changes in randomness, autocorrelation structures, and smoothness. Thus, time series analyses with complexity and information measures are of interest for a holistic understanding of ecosystem behaviour and early indications of natural and anthropogenic disturbances of ecosystems such as ecosystem degradation and climate change. Further, these measures provide additional criteria for the calibration of model parameters, tests of model validity, and determination of the necessary degree of complexity of process models. In this paper, we present the outcome from applications of information and complexity measures to hydrological time series in two climatically different forest ecosystems in South Germany and southern Ecuador. Information and complexity measures are different for different parameters but ecosystems of the same type such as mountain forests exhibit similar behaviour. We hypothesise that complexity of hydraulic time series increases with the number of abiotic and biotic variables involved in the generating process of the time series. Thus, complexity should reach a minimum in the precipitation signal which is controlled by abiotic, atmospheric factors only, and reach a maximum in the root zone where the interaction of abiotic and biotic variables is high. Hydrological time series under study cover the sequence of hydrological signals from open precipitation, throughfall, sapflow, water fluxes in the soil compartment and system discharge. We detected pronounced data aggregation and transformation effects of hydrological signals along their path through subsystems in terms of information propagation. We further found similar patterns in different ecosystems of the same general type. As a result of intensive abiotic and biotic interactions, a pronounced maximum of complexity was found in the moisture signal of the soil compartment.     

Nutrient contents and efficiencies of beech and spruce saplings as influenced by competition and O<Subscript>3</Subscript>/CO<Subscript>2</Subscript> regime

Saplings of Fagus sylvatica and Picea abies were grown under conditions of intra and interspecific competition in a 2-year phytotron study under combinations of ambient and elevated ozone (+O₃ which is 2 × O₃, but <150 nl l⁻¹) as well as carbon dioxide concentrations (+CO₂ which is amb. CO₂ + 300 μl CO₂ l⁻¹) in a full factorial design. Saplings were analysed for various mineral nutrients in different plant organs as well as biomass production and crown development. The study was based on the assumption that nutritional parameters important for growth and competitiveness are affected by stress defence under limiting nutrient supply. The hypotheses tested were (1) that nutrient uptake-related parameters (a) as well as efficiencies in nutrient use for above-ground competition (b) of beech rather than spruce are impaired by the exposure to elevated O₃ concentrations, (2) that the efficiency in nutrient uptake of spruce is enhanced by elevated CO₂ concentrations in mixed culture, and (3) that the ability to occupy above-ground space at low nutrient cost is co-determinant for the competitive success in mixed culture. Clear nitrogen deficiencies were indicated for both species during the 2-year phytotron study, although foliar nitrogen-biomass relationships were not so close for spruce than for beech. O₃ stress did not impair nutrient uptake-related parameters of beech; thus hypothesis (1a). was not supported. A negative effect of elevated O₃ (under amb. CO₂) on the N and P based efficiencies in above-ground space occupation (i.e. lower crown volume per unit of N or P invested in stems, limbs and foliage) of beech supported hypothesis (1b). It appeared that ozone stress triggered a nutrient demand for stress defence and tolerance at the expense of above-ground competition (trade-off). Crown volume of beech under O₃ stress was stabilized in monoculture by increased nutrient uptake. In general, the +CO₂-treatment was able to counteract the impacts of 2 × O₃. Elevated CO₂ caused lower N and S concentrations in current-year foliage of both tree species, slightly higher macronutrient amounts in the root biomass of spruce, but did not increase the efficiencies in nutrient uptake of spruce in mixed culture. Therefore hypothesis (2) was not supported. At the end of the experiment spruce turned out to be the stronger competitor in mixed culture as displayed by its higher total shoot biomass and crown volume. The amounts of macronutrients in the above-ground biomass of spruce individuals in mixed culture distinctly exceeded those of beech, which had been strongly reduced by interspecific competition. The superior competitiveness of spruce was related to higher N and P-based efficiencies in above-ground space occupation as suggested in hypothesis (3). This article belongs to the special issue “Growth and defence of Norway spruce and European beech in pure and mixed stands”.     

Synthesis and Bioactivity of Ancorinoside B,a Marine Diglycosyl Tetramic Acid

The sponge metabolite ancorinoside B was prepared for the first time in 16 steps and 4% yield. It features a β-d-galactopyranosyl-(1→4)-β-d-glucuronic acid tethered to a d-aspartic acid-derived tetramic acid. Key steps were the synthesis of a fully protected d-lactose derived thioglycoside, its attachment to a C₂₀-aldehyde spacer, functionalization of the latter with a terminal N-(β-ketoacyl)-d-aspartate, and a basic Dieckmann cyclization to close the pyrrolidin-2,4-dione ring with concomitant global deprotection. Ancorinoside B exhibited multiple biological effects of medicinal interest. It inhibited the secretion of the cancer metastasis-relevant matrix metalloproteinases MMP-2 and MMP-9, and also the growth of Staphylococcus aureus biofilms by ca 87% when applied at concentrations as low as 0.5 µg/mL. This concentration is far below its MIC of ca 67 µg/mL and thus unlikely to induce bacterial resistance. It also led to a 67% dispersion of preformed S. aureus biofilms when applied at a concentration of ca 2 µg/mL. Ancorinoside B might thus be an interesting candidate for the control of the general hospital, catheter, or joint protheses infections.