Recovery of native plant communities after the control of a dominant invasive plant species, Foeniculum vulgare: Implications for management

The control and/or removal of a dominant invasive species is expected to lead to increases in native species richness and diversity. Small pilot studies were performed on Santa Cruz Island (SCI), California, in the early 1990s to test the efficacy of different methods on the control of Foeniculum vulgare (fennel) and management’s effects on native species recovery. We chose a treatment that showed significant native species recovery, applied it at the landscape scale, and followed its effects on fennel infested plant communities. We tested the hypothesis that results from small-scale studies translate to the landscape level. We found that although the control of fennel translated from the small to landscape scale, decreasing from an average of 60% to less than 3% cover, native species recovery did not occur in the landscape study as it did in the pilot studies. Invasive fennel cover was replaced by non-native grass cover over time. Unexpectedly, fennel cover in untreated fennel plots decreased significantly (though not as drastically) from over 60% cover to just under 40% cover while native species richness in untreated areas increased significantly. The correlation between precipitation and changes in native and non-native species richness and abundance in this study imply that changes in species abundances were highly correlated with environmental fluctuations. The lack of a native seedbank and the accumulation of non-native grass litter likely prevented the recovery of native species in treated areas. Greater vertical complexity found in fennel communities, which increased visitation by frugivorous birds and likely increased native seed dispersal, may have been responsible for the increase in native species richness in the untreated areas. These results suggest that successful invasive species control and native species recovery experiments conducted at small scales may not translate to the landscape level, and active restoration should be an organic component of such large-scale projects.     

The ecology of extinction: population fluctuation and decline in amphibians

Even among widespread species with high reproductive potentials and significant dispersal abilities, the probability of extinctions should be correlated both with population size variance and with the extent of population isolation. To address how variation in demographic characteristics and habitat requirements may reflect on the comparative risk of species decline, I examined 617 time series of population census data derived from 89 amphibian species using the normalized estimate of the realized rate of increase, ΔN, and its variance. Amphibians are demonstrably in general decline and exhibit a great range of dispersal abilities, demographic characteristics, and population sizes. I compared species according to life-history characteristics and habitat use. Among the populations examined, census declines outnumbered increases yet the average magnitudes for both declines and increases were not demonstrably different, substantiating findings of amphibian decline. This gives no support for the idea that amphibian population sizes are dictated by regimes featuring relatively rare years of high recruitment offset by intervening years of gradual decline such that declines may outnumber increases without negative effect. For any given population size, those populations living in large streams or in ponds had significantly higher variance than did populations of completely terrestrial or other stream-dwelling amphibians. This could not be related to life-history complexity as all the stream-breeding species examined have larvae and all of the wholly terrestrial species have direct development without a larval stage. Variance in ΔN was highest amongst the smallest populations in each comparison group. Estimated local extinction rates averaged 3.1% among pond-breeding frogs, 2.2% for pond-breeding salamanders, and negligible for both stream-breeding and terrestrial direct-developing species. Recoveries slightly exceeded extinctions among European pond-breeding frogs but not among North American pond-breeding frogs. Less common species had greater negative disparities between extinctions and recoveries. Species with highly fluctuating populations and high frequencies of local extinctions living in changeable environments, such pond- and torrent-breeding amphibians, may be especially susceptible to curtailment of dispersal and restriction of habitat.     

The relevance of seral eutrophication and plant competition to the management of successional communities

Seral and plagioclimax communities such as chalk grassland, dune grassland, and heathland, are of great conservational importance in the United Kingdom, and considerable resources are directed towards their management in nature reserves and amenity areas. It is suggested that an important feature of these communities is their low fertility, especially with respect to nitrogen, and that this is directly related to their floristic diversity. Successional changes, usually involving scrub colonization, lead to a build-up in fertility, to loss of floristic diversity, and often to a reduction in the wildlife and amenity value. The traditional forms of management practised on such communities—including grazing, burning, and mowing—probably arrest seral development partially by preventing the build-up of fertility in the ecosystem. Some examples of mineral nutrient studies are considered, and it is suggested that a greater knowledge of nutrient budgets is fundamental to the scientific management of these communities.     

Scientific principles for water utilization in the U.S.S.R.

Water resources are essential for economic and cultural development of a territory. Both economic development and the health of the people depend on the provision of pure water. Scientifically founded plans of water resources use and conservation should be based on a balance approach to the assessment of available water supply sources and, on the forecast of their interconnected change in the future in a close association with the forecast of the whole economy and culture of the studied region. In the future the main threat to the normal development of the economy and life will not be water deficiency but the conversion of rivers, lakes and other water supply sources into sewers. Therefore it is proposed that there be a complete cessation of sewage discharge (even of the so-called purified) into water supply sources while drawing up long-term water management balances.     

Interactions between the external mycelium of the mycorrhizal fungus Glomus intraradices and other soil microorganisms as affected by organic matter

The influence of organic matter on the interactions between external mycelium of the arbuscular mycorrhizal (AM) fungus Glomus intraradices, the bacterium Burkholderia cepacia and other soil microorganisms was studied in a root-free sand environment. Organic matter amendment, in terms of ground barley leaves, markedly increased the growth of the external mycelium of G. intraradices as estimated both with the fatty acid biomarker 16:1ω5 and hyphal length measurements. Mycelial proliferation of G. intraradices in sand with organic matter was unaffected by both inoculation with B. cepacia and a soil filtrate containing a mixed population of indigenous microorganisms. On the other hand, in the absence of organic matter, both inoculation with B. cepacia and the soil filtrate reduced the growth of G. intraradices, as estimated with measurements of 16:1ω5. In contrast, B. cepacia inoculation increased hyphal length density of G. intraradices in the absence of organic matter. Overall, the presence of external mycelium of G. intraradices increased the bacterial biomass and counteracted a suppressive effect of B. cepacia on the growth of saprotrophic fungi.     

An example of chartreuse skin colour in Onion (Allium cepa L.) cultivar Greenella

Genetic lines and example cultivars are used as markers to define variation when describing or evaluating wild or cultivated germplasm. Occasionally genotypes previously described in the literature are no longer available. This was thought to be the case for chartreuse skin colour in Onion. However, registration authorities undertaking Distinctness, Uniformity and Stability tests recently observed this skin colour in the cultivar Greenella and have provided seed to a genebank for long-term conservation. This characteristic is suitable both for use as a genetic marker and as an example cultivar for describing Onion skin colours.     

Triacylglycerol analysis for the quantification of cocoa butter equivalents (CBE) in chocolate: feasibility study and validation

A new European legislation (2000/36/CE) has allowed the use of vegetable fats other than cocoa butter (CB) in chocolate up to a maximum value of 5% in the product. The vegetable fats used in chocolate are designated as cocoa butter replacements and are called cocoa butter equivalents (CBE). The feasibility of CBE quantification in chocolate using triacylglycerol (TAG) profiles was conducted by analyzing 55 samples of CBs and 31 samples of CBEs using a liquid chromatograph equipped with an evaporative light scattering detector (HPLC-ELSD). Statistical evaluation of the data obtained has been performed, and a simulation study has been carried out to assess the viability to use this method for quantifying the amount of CBE in real mixtures and in chocolates. The TAGs POP, POS, PLS, and the ratios POP/PLS, POS/PLP (P, palmityl; O, oleyl; S, stearyl; L, linoleyl) are particularly significant to discriminate between CB and CBE. Analysis of 50 mixtures between 5 different CBEs and 10 different CBs at 2 different concentration levels is presented. The data are visualized and interpreted. A mathematical model has been developed to assess the amount of CBE in real mixtures. This predictive model has been successfully applied and validated on dark chocolates including authorized CBE. The results are affected by +/-2.1% absolute average error. In particular, estimations between 10 and 20% of CBE show a very good match. On the other hand, values equal to or smaller than 5% show a larger prediction error (detection limit of the method). For the main purpose of this method (i.e., quantification of CBE at 5% max in chocolate, which represents about 15% of the total fat) this model shows very good results. For milk chocolate, the mathematical model can also be used if TAG are integrated from partition number (PN) 46 to 54. Consequently, the model proposed provides sufficient information to verify the real application of the European legislation.     

Orientation of homing pigeons altered by a change in the direction of an applied magnetic field

Homing pigeons were equipped with a pair of small coils around their heads. Birds with an induced field of 0.6 gauss and the south magnetic pole up, oriented toward home normally under both sun and overcast. Birds with the polarity reversed oriented toward home when the sun was visible but often flew away from home under overcast.     

Generation of spatially coherent light at extreme ultraviolet wavelengths

We present spatial coherence measurements of extreme ultraviolet (EUV) light generated through the process of high-harmonic up-conversion of a femtosecond laser. With a phase-matched hollow-fiber geometry, the generated beam was found to exhibit essentially full spatial coherence. The coherence of this laser-like EUV source was shown by recording Gabor holograms of small objects. This work demonstrates the capability to perform EUV holography with a tabletop experimental setup. Such an EUV source, with low divergence and high spatial coherence, can be used for experiments involving high-precision metrology, inspection of optical components for EUV lithography, and microscopy and holography with nanometer resolution. Furthermore, the short time duration of the EUV radiation (a few femtoseconds) will enable EUV microscopy and holography to be performed with ultrahigh time resolution.