Integrated weight longlines with paired streamer lines - Best practice to prevent seabird bycatch in demersal longline fisheries

To evaluate a new technology - integrated weight longlines (IW) - as a viable seabird mitigation technology for demersal longline fisheries, we compared three experimental mitigation treatments, IW line alone, IW with paired streamer lines (IWPS) and unweighted longlines (UW) with PS (UWPS), to a control of no deterrent (UW alone). Trials took place on two vessels targeting Pacific cod (Gadus macrocephalus) over a five-month period in the Bering Sea, Alaska, USA. We used multiple criteria for evaluations - catch rates of all taxa, seabird abundance and attack rate, and gear sink rate and performance - making this study the largest and most comprehensive experiment of its kind.All mitigation technologies dramatically decreased seabird bycatch rates while having little to no effect on fish catch rates. Mitigation was more effective for surface foraging seabirds (Fulmarus glacialis and Larus spp.) than for diving seabirds (short-tailed shearwaters, Puffinus tenuirostris), reducing mortality rates by 91-100% and 80-97%, respectively. Based on multiple criteria, IWPS performed best, sinking gear within the protection of streamer lines eliminating surface forager catch completely and reducing shearwater catch by 97%, relative to the control. UWPS, status quo in the Alaska fishery, and IW alone performed similarly reducing surface forager catch rates by 98% and 91%, respectively, and shearwater rates by 87% and 80%, respectively. Seabird abundance and attack rate were poor proxies of seabird mortality, especially for IW gear. IW lines reduced the distance astern that birds have access to sinking baits by near half and its handling qualities proved superior to UW. We conclude that IW longlines and paired streamer lines are the core mitigation techniques and when deployed together, constitute the best management practice for seabird conservation in demersal longline fisheries using autoline systems.     

Effects of experimental soil frost on the fine‐root system of mature Norway spruce

Soil‐frost events may influence the dynamics of fine roots and therefore affect root‐derived C fluxes to the soil. We studied the impact of soil frost on the fine‐root dynamics of Norway spruce (Picea abies [L.] Karst.) by a replicated snow‐removal experiment in a mature forest in SE Germany. Snow removal in the three treatment plots reduced soil temperature significantly with minima <–5.5°C in the O layer while the snow‐covered control plots never reached temperatures below the freezing point. Sequential soil coring in the O layer at the beginning and at the end of the soil‐frost period as well as after thawing revealed that the soil frost treatment increased fine‐root mortality by 29%. However, enhanced fine‐root production in the snow‐removal plots nearly compensated for the fine‐root losses caused by low temperatures. These findings were confirmed by minirhizotron observations in the O layer and the upper 25 cm of the mineral soil showing that relative fine‐root loss was by far higher in the snow‐removal plots than in the control plots. Compensatory fine‐root production in the snow‐removal plots exceeded fine‐root production in the control plots during a period of 8 weeks after the soil frost application by 39% in the O layer while it was similar in both plot types in the mineral soil. Sequential coring and minirhizotron observations led to substantially different fine root–longevity estimates for the soil frost period. However, in both cases, the snow‐removal treatment was characterized by a significant reduction in root longevity indicating a faster fine‐root turnover. As a consequence, experimental soil frost enhanced the C input to the soil via root death at our study site by approx. 42 g m^–2 and stimulated the C investment towards the root system of the spruce trees due to a higher sink activity.     

Short-term and long-term effects of human trampling on above-ground vegetation, soil density, soil organic matter and soil microbial processes in suburban beech forests

Understanding the effects of disturbance by human trampling on ecosystem processes is essential for the management of recreational areas. Discussions on recreational impacts are based either on data from trampling experiments or on field survey data from sites subjected to long-term recreational use, but rarely on a combination of both. We examined whether results from a short-term trampling experiment reflect the impact of long-term trampling around frequently used fire places. We compared short- and long-term effects of human trampling on above-ground forest vegetation and soil physical, chemical and microbial characteristics. We found both similarities and differences in short- and long-term trampling effects. Both short- and long-term trampling reduced plant cover, plant height and species density, though long-term effects were more pronounced than short-term effects. In both approaches, leaf litter biomass decreased, whereas soil density increased with trampling intensity. Other soil characteristics including soil moisture, total soil organic matter content and total organic nitrogen content were not or only marginally affected by short- and long-term trampling. Furthermore, soil microbial biomass and the activity of dehydrogenase did not change in both approaches. In contrast, the activity of β-glucosidase was only reduced by short-term trampling, whereas activity of phosphomonoesterase was reduced only by long-term trampling. Soil compaction was one factor reducing microbial activities at low and medium trampling intensities in our experiment and in the highly compacted area around the fire rings. We conclude that it could be problematic to use the results of short-term trampling experiments to predict general long-term trampling effects. Our results imply also that the restoration of degraded sites might be hampered by the low nutrient turnover resulting from the reduced litter layer and changes in enzyme activities, mitigating a successful re-establishment and growth of plants.     

Structure-antioxidant efficiency relationships of phenolic compounds and their contribution to the antioxidant activity of sea buckthorn juice

The phenolic composition of juice derived from fruits of sea buckthorn (Hippophae rhamnoides) was investigated by high-performance liquid chromatography (HPLC) with diode array and electrochemical detection. Flavonols were found to be the predominating polyphenols while phenolic acids and catechins represent minor components. Of the seven flavonols identified, isorhamnetin 3-O-glycosides were the most important representatives quantitatively. However, because of their structural properties, they were poor radical scavengers as shown by electron spin resonance spectroscopy. Phenolic compounds such as quercetin 3-O-glycosides, catechins, and hydroxybenzoic acids with a catechol structure exhibited good antioxidant capacities, but their concentration in sea buckthorn juice was small. These phenolic compounds, determined by HPLC, accounted for less than 5% of the total antioxidant activity of the filtered juice. Ascorbic acid was shown to be the major antioxidant in sea buckthorn juice. Because of its high concentration of 1.22 g/L, it contributes approximately 75% to total antioxidant activity. The remaining difference can be attributed to higher molecular weight flavan-3-ols (proanthocyanidins), which were determined photometrically after acid depolymerization to colored anthocyanidins.     

Intensive recreational activities in suburban forests: A method to quantify the reduction in timber value

Central European forests are generally multifunctional; the same forest areas are used for timber production and recreation. In frequently visited areas damage to trees can be observed. We developed a method to estimate the actual reduction in timber value due to recreation-induced damage. The method was tested in two suburban (oak–hornbeam and beech) forests sustainably maintained by a selective management system and with free access in northwestern Switzerland. Considering the total forest areas, 9.4% of oak trees and 23.0% of beech trees were damaged by recreational activities. The resulting reduction in timber value averaged 19 and 53 € ha^?1 a^?1 in the two forests. The annual reduction in timber value due to recreation-induced damage can account for up to 16% of the total proceeds. The monetary benefits of forest recreation in these areas, however, by far exceed the damage to trees.     

Colluvisols under cultivation in Schleswig-Holstein. 3. Soil organic matter transformation after translocation

‘Colluvisols’ (Colluvi-cumulic Anthrosols) are an important soil unit in North Germany. In the landscape of loamy till these soils are associated with eroded Luvisols. The soil organic matter (SOM) of top layers of both soils was compared by using approaches of wet chemistry, CPMAS ¹³C-NMR and pyrolysis field-ionization mass spectrometry (Py-FIMS). The Luvisols are sources of SOM transfer due to a continuous erosion process. The annual input of straw and plant residues induces the dominance of litter compounds like proteins, polysaccharides and lignin in the SOM. The Colluvisols are sinks of SOM transfer with a predominance of humic compounds. Lignin is degraded forming humic compounds with an alkylic and aromatic structure. In these soils selected compounds with higher mass signals were detected by Py-FIMS, which may indicate the existence of typical “SOM markers” in the colluvic materials.     

Einfluss verschiedener Bodenentseuchungsmaßnahmen auf das Unkrautsamenpotenzial sowie auf mikrobielle Aktivitäten im Boden

In autumn soil from the upper layer of a long-term weed nursery was sampled. This soil was fumigated with “Basamid Granulat” (dazomet) or treated with a steamer or remained untreated. During 19 months germinating weed seeds were counted in representative samples. Both sterilizing procedures nearly eliminated the seeds of annual weeds. Another part of the treated soil was incubated under laboratory conditions up to twelve weeks to investigate biomass-related dehydrogenase activity (DHA) and substrate-induced short-term respiration (KZA) as well as carbon mineralization (LZA), alkaline phosphatase (APA) and arylsulfatase (ASA). The steaming strongly reduced APA, ASA, DHA and KZA whereas “Basamid Granulat” mostly acted weaker. The LZA was slightly reduced by “Basamid Granulat” but slightly increased by steaming. Lucerne meal partly modified these effects. In a succeeding trial the disinfected soil was additionally treated with the herbicidal reference compound “Herbogil Liquide D” (dinoterb) after ten weeks. In the not disinfected soil the herbicide caused a dose-related inhibition of the DHA and – depending on sampling time, lucerne meal or dosage – affected the LZA. In the previously fumigated soil herbicidal effects may be modified. Overall the soil disinfection as well as the reference compound impaired the soil biocenosis.