How far do experimentally elevated CO2 levels reach into the surrounding? – An example using the 13C label of soil organic matter as an archive

During the last two decades, free air CO₂ enrichment (FACE) studies have been conducted to study the effects of rising atmospheric CO₂ concentrations on ecosystems. The distances between fumigated and control plots differ widely among those projects, but no experimental data are available how far into the surrounding area an effect of CO₂ fumigation can be detected. As the CO₂ gas added to the fumigated plots has a different ¹³C label than ambient atmospheric CO₂, its carbon can be traced into plants and soil organic matter (SOM). The Swiss FACE in Eschikon had been conducted for 10 years on a grassland site. After it had ended, we analysed soil samples from three transects extending from the plots to the surrounding area for their organic carbon (C_org) content and carbon isotopic signature. We determined the maximum spatial extension to which carbon originating from the fumigation was incorporated into SOM. A budget of the fumigation gas‐derived C_org in the upper 10 cm of the soil showed that approximately 50 kg C were stored within the plots, and an additional 31 kg C were stored in their immediate surroundings up to a distance of 9 m from the gas pipes. The presented approach provides us with a method to determine a posteriori the extension to which the CO₂ fumigation treatment contaminated its immediate surroundings during a FACE experiment. In the presented example, this showed that the distances between plots could have been reduced significantly. Although not generalizable to other experimental settings, the finding indicates that optimizing the spatial layout, e.g. by modelling gas dispersion, will be useful when planning future large‐scale FACE infrastructures. Our approach provides a solid basis to test such gas‐dispersion models on existing FACE sites before planning new sites.     

Release from native herbivores facilitates the persistence of invasive marine algae: a biogeographical comparison of the relative contribution of nutrients and herbivory to invasion success

The effect of herbivory and nutrient enrichment on the growth of invasive and native macroalgal species was simultaneously studied in two biogeographic regions: the Caribbean and Hawaii. Herbivores suppressed growth of invasive algae in their native (Caribbean) and invaded range (Hawaii), but despite similar levels of herbivore biomass, the intensity of herbivory was lower in Hawaii. Algal species with a circumtropical distribution did not show a similar effect of herbivores on their growth. Nutrient enrichment did not enhance growth of any algal species in either region. The reduction in herbivore intensity experienced by invasive algae in Hawaii rather than an escape from (native) herbivores provided invasive macroalgae with “enemy release” sensu the Enemy Release Hypothesis (ERH). Since native, Hawaiian herbivores still feed and even prefer invasive algae over native species, invasion scenario’s that involve predation (e.g. the ERH) could be falsely dismissed when invasive species are only studied in their invasive range. We therefore argue that escape from herbivores (i.e. enemy release) can only effectively be determined with additional information on the intensity of predation experienced by an invasive species in its native range.     

THE DISTRIBUTION AND ACCUMULATION OF SELENIUM IN ROOTS AND SHOOTS OF PLANTS NATURALLY GROWN IN THE SOILS OF KEBAN’S PB-ZN-F MINING AREA,TURKEY

The objective of this study is to determine the distribution factors and enrichment coefficients between soil and plant parts by studying the accumulation and distribution of selenium (Se) in the roots and shoots of different plants. The plants (9 samples of Euphorbia macroclada, 5 samples of Verbascum cheiranthifolium, 8 samples of Astragalus gummifer) and their associated soil samples were collected from the Keban mining area. The roots and the shoots of these plants, together with the associated soils, were analyzed by ICP-MS. The mean Se value of the contaminated surface soils was found to be two to five times higher than those of previously studied uncontaminated surface soils. Se concentrations of the plant parts were lower than those in their associated alkaline soils, where the plants were grown, except for in the shoots of A. gummifer. Mean Se concentrations in the roots of E. macroclada, V. cheiranthifolium, and A. gummifer were 0.82, 0.22, and 0.47 mg kg^?1 on a dry weight basis, respectively, while Se concentrations were 0.29, 0.26, and 2.66 mg kg^?1 in the shoots on a dry weight basis, respectively. The enrichment coefficients and the distribution factors of those plants were lower than 1, except for the distribution factors of V. cheiranthifolium and A. gummifer plants. Thus, it appeared that the shoots of these plants could make them efficient bioaccumulator plants for Se because of high distribution factors and enrichment coefficients. Due to such factors, they can also be used to clean or rehabilitate soils and areas contaminated with Se.     

Enrichment and Chemical Fraction of Copper and Zinc in the Sediments of the Daliao River System,China

Copper and zinc contents and their chemical forms in the surface sediments of the Daliao River system (DRS) were investigated to quantitatively assess their contamination, mobility, and potential bioavailability. Twenty-seven surface sediment samples were collected and analyzed for total contents of Cu, Zn, Al, Fe and Mn and for chemical forms of Cu and Zn. These results reveal that the total contents of Cu and Zn in the sediment of DRS mainly ranged from 4.5 to 86.1 and 17.7 to 1340.9 mg kg^?1, respectively. The enrichment factors (EFs) were generally lower than 1.0 at most sampling sites, while at T3, B5 and B7 sites of the Taizi River near Benxi, Liaoyang and Anshan cities, respectively, they were more than 2.0. The primary sources of Zn and Cu contamination at these three sites are considered to be iron mining and smelting and some chemical industries. Hence, the total contents of Cu and Zn in the sediments of the Daliao River system mainly ranged around background levels. In general, less than 2% and more than 60% of total Cu and Zn contents in the sediment at most sampling sites were associated to the exchangeable fraction and residual fraction, respectively, showing their low mobility and bioavailability. The major sink for anthropogenic Cu might be organic matter and Fe oxides, while for anthropogenic Zn it was carbonate and the easily reducible phase dominated by Mn and amorphous Fe oxides. Therefore, anthropogenic Cu and Zn have relatively high potential mobility and bioavailability. In comparison with the sediments of other rivers in China and in the world, the sediment of the DRS contained relatively low contents of Cu and Zn.     

On Distance‐Based Permutation Tests for Between‐Group Comparisons

Summary Permutation tests based on distances among multivariate observations have found many applications in the biological sciences. Two major testing frameworks of this kind are multiresponse permutation procedures and pseudo‐F tests arising from a distance‐based extension of multivariate analysis of variance. In this article, we derive conditions under which these two frameworks are equivalent. The methods and equivalence results are illustrated by reanalyzing an ecological data set and by a novel application to functional magnetic resonance imaging data.     

Isolation of Mouse Peritoneal Cavity Cells

The peritoneal cavity is a membrane-bound and fluid-filled abdominal cavity of mammals, which contains the liver, spleen, most of the gastro-intestinal tract and other viscera. It harbors a number of immune cells including macrophages, B cells and T cells. The presence of a high number of naïve macrophages in the peritoneal cavity makes it a preferred site for the collection of naïve tissue resident macrophages (1). The peritoneal cavity is also important to the study of B cells because of the presence of a unique peritoneal cavity-resident B cell subset known as B1 cells in addition to conventional B2 cells. B1 cells are subdivided into B1a and B1b cells, which can be distinguished by the surface expression of CD11b and CD5. B1 cells are an important source of natural IgM providing early protection from a variety of pathogens (2-4). These cells are autoreactive in nature (5), but how they are controlled to prevent autoimmunity is still not understood completely. On the contrary, CD5⁺ B1a cells possess some regulatory properties by virtue of their IL-10 producing capacity (6). Therefore, peritoneal cavity B1 cells are an interesting cell population to study because of their diverse function and many unaddressed questions associated with their development and regulation. The isolation of peritoneal cavity resident immune cells is tricky because of the lack of a defined structure inside the peritoneal cavity. Our protocol will describe a procedure for obtaining viable immune cells from the peritoneal cavity of mice, which then can be used for phenotypic analysis by flow cytometry and for different biochemical and immunological assays.     

Changes in the phyllosphere community of the resurrection fern, Polypodium polypodioides, associated with rainfall and wetting

A combination of analyses were used to characterize the changes that occur in a bacterial community present in the phyllosphere of the epiphytic resurrection fern, Polypodium polypodioides, as the fern rehydrates from a desiccation-resistant, physiologically inactive state. Enrichment assays showed an increase in the viable count of bacteria using labile organic substrates following rainfall. Isolates obtained from enrichments were predominantly Gram-positive bacteria affiliated with various groups of the Actinobacteria and Firmicutes. In contrast, sequencing of 16S rRNA genes clones obtained from whole community DNA revealed that much of the community was dominated by other taxa, particularly the Alphaproteobacteria. Similar isolates were obtained from both dry and hydrated P. polypodioides fronds, whereas 16S rRNA gene sequencing of community DNA revealed different ribotypes on the dry and wet fern, and an overall reduction in richness following wetting. Wetting also produced changes in phyllosphere extracellular enzyme activity, with an initial burst of activity following rainfall and a subsequent burst approximately 48 h later. These findings suggest that the resurrection fern harbors a complex phyllosphere community, and that rehydration of the fern following rainfall may act as an enrichment culture stimulating certain bacterial populations and changing the overall community structure and activity.     

Bioassay Method in Evaluation of Trophic Conditions and Nutrient Limitation in the Danube Wetland Waters (1388–1426 r. km)

The algal growth potential (AGP) in water samples of the Danube wetland waters (1388–1426 r. km) as well as the effect of nitrogen (in final concentration of 0.16 g l⁻¹) and phosphorus enrichment (in final concentration of 0.02 g l⁻¹) on the AGP was investigated by miniaturized bioassay method. Values of the total biomass of Chlorella kessleri up to the 14th day of incubation were suitable for the evaluation of trophic conditions according to the classification of AGP. On the basis of the AGP results, trophic conditions in 55% of the samples were oligo-mesotrophic and in 46% of the samples meso-eutrophic. A statistically significant correlation (r = 0.34) was established between the AGP of C. kessleri in original water samples and NO₃ concentrations in situ. The TN/TP ratio in the wetland waters indicated a greater limitation due to nitrogen than phosphorous. Significantly lower TSI_TN than TSI_SD, TSI_Chla and TSI_TP indicated nitrogen limited conditions. In order to quantify established nutrient limitation by the bioassay method, the effect of added N and P concentrations on the growth rate of C. kessleri was expressed as the degree of nutrient limitation (Δr d⁻¹) during 7 days of incubation. In the Danube wetland waters only N limitation was established in June and July; N and P limitation in May and September while in August and October 2003 neither of the tested nutrients were limiting. From May to October 2003 the significantly highest degree of nitrogen (Δr = 0.736 d⁻¹) and phosphorus limitation (Δr = 0.474 d⁻¹) was determined in Lake Sakadaš.     

饲养密度和鸡笼局部遮光对肉种鸡产蛋期行为与福利的影响

用行为录像记录分析仪(TheObserverVideo-Pro,Noldus)观察和测定肉种鸡在产蛋期行为的变化。对两种不同饲养密度(或者空间供给单鸡笼组,1600cm2/只;双鸡笼组,800cm2/只)及鸡笼后部局部遮光与对照组进行比较实验结果表明,单鸡笼组肉种鸡的转身、挠头等行为均显著多于双鸡笼组,而展翅行为显著少于双鸡笼组;遮光组的肉种鸡采食行为显著多于未遮光组;遮光单鸡笼组肉种鸡,其产蛋行为趋向选择暗光区域。研究提示,虽然密度对蛋鸡行为的效应大于遮光的效应,但是局部遮光能够在一定程度上增加盒式笼养鸡的环境丰富度,降低密度增大引起的拥挤效应,可能缓解其较差的福利状态。