Effects of silver nanoparticles on the microbiota and enzyme activity in soil   总被引：1，自引：0，他引：1  

Mathias Hänsch  Christoph Emmerling 《植物养料与土壤学杂志》2010,173(4):554-558

To assess the impact of silver nanoparticles (SNP) on soil microbial biomass, microbial activity, and enzyme activities, a medium‐term experiment over four months was performed in which soil was applied with increasing SNP‐application rates compared to a control. The treatments included a single SNP‐application dose analogous to 3.2 (SNP‐1), 32 (SNP‐10), and 320 (SNP‐100) μg Ag (kg dry soil)^–1 and a control without SNP application, respectively. At the end of the experiment, clear evidence was found that microbial biomass was significantly decreased with increasing SNP‐application rate, while basal respiration was increased in this direction. In addition, metabolic quotients were increased in the SNP treatments compared to the control. This is at least circumstantial evidence that the efficiency of substrate use was lowered in SNP‐treated soils. Another suggestion might be that after four months microbial‐community composition was changed due to SNP. No treatment effects were found for microbial biomass N, fluorimetric enzymes, and the abiotic soil parameters pH and soil organic C.  相似文献   

Canopy vs. understory: Does tree diversity affect bee and wasp communities and their natural enemies across forest strata?     

Stephanie Sobek  Teja Tscharntke  Christoph Scherber  Susanne Schiele  Ingolf Steffan-Dewenter 《Forest Ecology and Management》2009

Bees and wasps provide important ecosystem services such as pollination and biocontrol in crop-dominated landscapes, but surprisingly little information is available on hymenopteran communities in temperate forest ecosystems. Species richness and abundance of bees and wasps can be hypothesised to increase with plant diversity, structural complexity, and availability of food and nesting resources. By experimentally exposing standardised nesting sites, we examined abundance and species richness of cavity-nesting bees (pollinators), wasps (predators) and their associated parasitoids across a tree diversity gradient in a temperate deciduous forest habitat. In addition, spatial distribution of individuals and species across forest strata (canopy vs. understory) was tested. Abundance and species richness was high for predatory wasps, but generally low for pollinators. Species-rich forest stands supported increased abundance, but not species richness, of pollinators and predatory wasps, and also increased abundance and species richness of natural enemies. In addition, the forests showed a distinct spatial stratification in that abundance of bees, wasps and parasitoids as well as parasitism rates were higher in the canopy than understory. We conclude that particularly the canopy in temperate forest stands can serve as an important habitat for predatory wasp species and natural enemies, but not bee pollinators. Enhanced tree diversity was related to increased hymenopteran abundance, which is likely to be linked to an increase in nesting and food resources in mixed forest stands.  相似文献   

Lichen diversity in temperate montane forests is influenced by forest structure more than climate     

Christoph Moning  Silke Werth  Frank Dziock  Claus Bässler  Johannes Bradtka  Torsten Hothorn  Jörg Müller 《Forest Ecology and Management》2009

Although the effect of forest management on lichens in temperate forests has been widely examined, little is known about the influence of management-related factors on their biodiversity relative to factors that cannot be altered by management. Here we determined whether forest structure or climate determines lichen diversity in the Bavarian Forest National Park in southeastern Germany, taking spatial variables into account. We investigated 517 single tree stems along 4 transects in 113 pre-stratified plots (8 m in diameter) in this montane forest. We grouped environmental variables into three sets: climate (macroclimate, non-manageable), forest structure (manageable), and space. The explanatory powers of these sets of variables for lichen diversity were compared using variance partitioning for the lichen community, species density, and threatened species density. The relationships of single characteristics of forest structure with lichen species diversity were analyzed using generalized linear models (GLM). Lichen diversity was better explained by stand structures than by climate. Spatial effects influenced the number of species per plot. Among the structural features, the availability of dead wood and sycamore maple as well as forest continuity were most important for the enhancement of lichen diversity. Open canopy structures affected the total diversity positively. Although the availability of large trees was not an influential factor in the GLM at the plot level, high diversity levels were generally associated with large stem diameters at the level of single stems. We provide recommendations for sustainable forest-management practices that aim at specifically enhancing lichen diversity in temperate areas experiencing low levels of air pollution.  相似文献   

Effects of six years of simulated N deposition on gross soil N transformation rates in an old-growth temperate forest   总被引：1，自引：0，他引：1  

Peng Tian  Jinbo Zhang  Christoph Müller  Zucong Cai  Guangze Jin 《林业研究》2018,29(3):647-656

Elevated atmospheric nitrogen(N) deposition has been detected in many regions of China, but its effects on soil N transformation in temperate forest ecosystems are not well known. We therefore simulated N deposition with four levels of N addition rate(N0, N30, N60, and N120) for6 years in an old-growth temperate forest in Xiaoxing'an Mountains in Northeastern China. We measured gross N transformation rates in the laboratory using ~(15)N tracing technology to explore the effects of N deposition on soil gross N transformations taking advantage of N deposition soils. No significant differences in gross soil N transformation rates were observed after 6 years of N deposition with various levels of N addition rate. For all N deposition soils, the gross NH_4~+ immobilization rates were consistently lower than the gross N mineralization rates,leading to net N mineralization. Nitrate(NO_3~-) was primarily produced via oxidation of NH_4~+(i.e., autotrophic nitrification), whereas oxidation of organic N(i.e., heterotrophic nitrification) was negligible. Differences between the quantity of ammonia-oxidizing bacteria and ammonia-oxidizing archaea were not significant for any treatment, which likely explains the lack of a significant effect on gross nitrification rates. Gross nitrification rates were much higher than the total NO_3~- consumption rates,resulting in a build-up of NO_3~-, which highlights the high risk of N losses via NO_3~- leaching or gaseous N emissions from soils. This response is opposite that of typical N-limited temperate forests suffering from N deposition,suggesting that the investigated old-growth temperate forest ecosystem is likely to approach N saturation.  相似文献   

Comparison of subcutaneous dexmedetomidine–midazolam versus alfaxalone–midazolam sedation in leopard geckos (Eublepharis macularius)     

Grayson A. Doss  Dustin M. Fink  Kurt K. Sladky  Christoph Mans 《Veterinary anaesthesia and analgesia》2017,44(5):1175-1183

Objective

To compare dexmedetomidine–midazolam with alfaxalone–midazolam for sedation in leopard geckos (Eublepharis macularius).

Study design

Prospective, randomized, blinded, complete crossover study.

Animals

Nine healthy adult leopard geckos.

Methods

Geckos were administered a combination of dexmedetomidine (0.1 mg kg^?1) and midazolam (1.0 mg kg^?1; treatment D–M) or alfaxalone (15 mg kg^?1) and midazolam (1.0 mg kg^?1; treatment A–M) subcutaneously craniodorsal to a thoracic limb. Heart rate (HR), respiratory rate (f_R), righting reflex, palpebral reflex, superficial and deep pain reflexes, jaw tone and escape response were assessed every 5 minutes until reversal. Conditions for intubation and response to needle prick were evaluated. Antagonist drugs [flumazenil (0.05 mg kg^?1) ± atipamezole (1.0 mg kg^?1)] were administered subcutaneously, craniodorsal to the contralateral thoracic limb, 45 minutes after initial injection, and animals were monitored until recovery.

Results

HR, but not f_R, decreased significantly over time in both treatments. HR was significantly lower than baseline at all time points in D–M and for all but the 5 and 10 minute time points in A–M. HR was significantly higher in A–M at all time points after drug administration when compared with D–M. Sedation scores between protocols were similar for most time points. All animals in A–M lost righting reflex compared with seven out of nine (78%) geckos in D–M. Geckos in A–M lost righting reflex for significantly longer time. Mean ± standard deviation time to recovery after antagonist administration was 6.1 ± 2.2 minutes for D–M and 56 ± 29 minutes for A–M, and these times were significantly different.

Conclusions and clinical relevance

Combination D–M or A–M provided sedation of a level expected to allow physical examinations and venipuncture in leopard geckos. A–M provided a faster onset of sedation compared with D–M. Recovery was significantly faster following antagonist reversal of D–M, compared with A–M.  相似文献   

The effects of a topical lipid complex therapy on dogs with atopic dermatitis: a double blind,randomized, placebo‐controlled study          下载免费PDF全文

Stefan Hobi  Christoph Klinger  Janine Classen  Ralf S. Mueller 《Veterinary dermatology》2017,28(4):369-e84

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An anatomical study of plate‐rod fixation in feline tibiae          下载免费PDF全文

Andreas Gutbrod Dr Med Vet  DECVS  Simona Vincenti Dr Med Vet  Karolin Kühn Dr Med Vet  DECVDI  Sebastian Christoph Knell Dr Med Vet  DECVS  Philipp Alexander Schmierer DECVS  Antonio Pozzi Prof Med Vet  DECVS 《Veterinary surgery : VS》2017,46(7):909-914

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Productivity of temperate broad-leaved forest stands differing in tree species diversity   总被引：1，自引：0，他引：1  

Mascha Jacob  Christoph Leuschner  Frank M. Thomas 《Annals of Forest Science》2010,67(5):503-503

? Understanding the effects of tree species diversity on biomass and production of forests is fundamental for carbon sequestration strategies, particularly in the perspective of the current climate change. However, the diversity-productivity relationship in old-growth forests is not well understood.

? We quantified biomass and above-ground production in nine forest stands with increasing tree species diversity from monocultures of beech to stands consisting of up to five deciduous tree species (Fagus sylvatica, Fraxinus excelsior, Tilia spp., Carpinus betulus, Acer spp.) to examine (a) if mixed stands are more productive than monospecific stands, (b) how tree species differ in the productivity of stem wood, leaves and fruits, and (c) if beech productivity increases with tree diversity due to lower intraspecific competition and complementary resource use.

? Total above-ground biomass and wood production decreased with increasing tree species diversity. In Fagus and Fraxinus, the basal area-related wood productivity exceeded those of the co-occurring tree species, while Tilia had the highest leaf productivity. Fagus trees showed no elevated production per basal area in the mixed stands.

? We found no evidence of complementary resource use associated with biomass production. We conclude that above-ground productivity of old-growth temperate deciduous forests depend more on tree species-specific traits than on tree diversity itself.

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High-flux solar-driven thermochemical dissociation of CO2 and H2O using nonstoichiometric ceria     

Chueh WC  Falter C  Abbott M  Scipio D  Furler P  Haile SM  Steinfeld A 《Science (New York, N.Y.)》2010,330(6012):1797-1801

Because solar energy is available in large excess relative to current rates of energy consumption, effective conversion of this renewable yet intermittent resource into a transportable and dispatchable chemical fuel may ensure the goal of a sustainable energy future. However, low conversion efficiencies, particularly with CO(2) reduction, as well as utilization of precious materials have limited the practical generation of solar fuels. By using a solar cavity-receiver reactor, we combined the oxygen uptake and release capacity of cerium oxide and facile catalysis at elevated temperatures to thermochemically dissociate CO(2) and H(2)O, yielding CO and H(2), respectively. Stable and rapid generation of fuel was demonstrated over 500 cycles. Solar-to-fuel efficiencies of 0.7 to 0.8% were achieved and shown to be largely limited by the system scale and design rather than by chemistry.  相似文献   

The decline of endangered stone crayfish (Austropotamobius torrentium) in southern Germany is related to the spread of invasive alien species and land‐use change          下载免费PDF全文

Christoph Chucholl  Anne Schrimpf 《水产资源保护:海洋与淡水生态系统》2016,26(1):44-56