48 research outputs found
Detecting trends in landuse and landcover change of Nech Sar National Park, Ethiopia
No full textNech Sar National Park (NSNP) is one of the most important biodiversity centers in Ethiopia. In recent years, a widespread decline of the terrestrial ecosystems has been reported, yet to date there is no comprehensive assessment on degradation across the park. In this study, changes in landcover were analyzed using 30 m spatial resolution Landsat imagery. Interannual variations of normalized difference vegetation index (NDVI) were examined and compared with climatic variables. The result presented seven landcover classes and five of the seven landcover classes (forest, bush/shrubland, wooded grassland, woodland and grassland) were related to natural vegetation and two landcover types (cultivated land and area under encroaching plants) were direct results of anthropogenic alterations of the landscape. The forest, grassland, and wooded grassland are the most threatened habitat types. A considerable area of the grassland has been replaced by encroaching plants, prominently by Dichrostachys cinerea, Acacia mellifera, A. nilotica, A. oerfota, and A. seyal and is greatly affected by expansion of herbaceous plants, most commonly the species of the family Malvaceae which include Abutilon anglosomaliae, A.bidentatum and A.figarianu. Thus, changes in vegetation of NSNP may be attributed to (i) degradation of existing vegetation through deforestation and (ii) replacement of existing vegetation by encroaching plants. While limited in local meteorological station, NDVI analysis indicated that climate related changes did not have major effects on park vegetation degradation, which suggests anthropogenic impacts as a major driver of observed disturbance
Does the exotic equal pollution? Landscape methods for solving the dilemma of planting native versus non-native plant species in drylands
No full textThere is a pressing need to resolve methods that can determine native versus non-native plant use in drylands, arid areas and indeed in more temperate areas around the world. This is because whilst plant introductions may have positive objectives they can have negative landscape and ecological impacts. A key discussion on this issue focuses on whether the use of non-native plant species can be considered to be pollution and pollutive, based on the concept that pollution can be regarded as ‘matter out of place’. There are many examples of nature based , e.g. radon or toxic waters but what this paper focuses on is the issue of human induced pollution in the form of planting. This paper aims to determine a number of methods based on sustainability principles and on those used in landscape and environmental impact assessment to determine when and where non-native plants could be used and where native plants should be used. These sometimes simple and sometimes more complex methods are determined by understanding the genius loci / sense of place, and the ‘nature’ of landscape. They are determined through the identity of landscape character, landscape quality, landscape value and sensitivity to change. A complex model using a matrix tool, determines plant use types by combining sensitivity to change of the landscape relative to the magnitude of change that would be caused through the use of non-native plant species
Ecological restoration across the Mediterranean Basin as viewed by practitioners
No full textRestoration efforts in the Mediterranean Basin have been changing from a silvicultural to an ecological restoration approach. Yet, to what extent the projects are guided by ecological restoration principles remains largely unknown. To analyse this issue, we built an on-line survey addressed to restoration practitioners. We analysed 36 restoration projects, mostly from drylands (86%). The projects used mainly soil from local sources. The need to comply with legislation was more important as a restoration motive for European Union (EU) than for non-EU countries, while public opinion and health had a greater importance in the latter. Non-EU countries relied more on non-native plant species than EU countries, thus deviating from ecological restoration guidelines. Nursery-grown plants used were mostly of local or regional provenance, whilst seeds were mostly of national provenance. Unexpected restoration results (e.g. inadequate biodiversity) were reported for 50% of the projects and restoration success was never evaluated in 22%. Long term evaluation (> 6 years) was only performed in 31% of cases, and based primarily on plant diversity and cover. The use of non-native species and species of exogenous provenances may: i) entail the loss of local genetic and functional trait diversity, critical to cope with drought, particularly under the predicted climate change scenarios, and ii) lead to unexpected competition with native species and/or negatively impact local biotic interactions. Absent or inappropriate monitoring may prevent the understanding of restoration trajectories, precluding adaptive management strategies, often crucial to create functional ecosystems able to provide ecosystem services. The overview of ecological restoration projects in the Mediterranean Basin revealed high variability among practices and highlighted the need for improved scientific assistance and information exchange, greater use of native species of local provenance, and more long-term monitoring and evaluation, including functional and ecosystem services' indicators, to improve and spread the practice of ecological restoration.This work was conducted within the framework of COST of Action ES1104 on ‘Arid lands restoration and combat of desertification: setting up a drylands and desert restoration hub’. FCT-MEC supported A.N. contribution by contract SFRH/BD/51407/2011 and C.B. contribution by contract Investigador FCT. The CGIAR Research Programs in Dryland Systems (CRP-DS; budget code 200008) and in Water Land and Ecosystems (WLE; budget code 950201) supported C. Z. contribution
Does the exotic equal pollution? Landscape methods for solving the dilemma of planting native versus non-native plant species in drylands
No full textThere is a pressing need to resolve methods that can determine native versus non-native plant use in drylands, arid areas and indeed in more temperate areas around the world. This is because whilst plant introductions may have positive objectives they can have negative landscape and ecological impacts. A key discussion on this issue focuses on whether the use of non-native plant species can be considered to be pollution and pollutive, based on the concept that pollution can be regarded as ‘matter out of place’. There are many examples of nature based , e.g. radon or toxic waters but what this paper focuses on is the issue of human induced pollution in the form of planting. This paper aims to determine a number of methods based on sustainability principles and on those used in landscape and environmental impact assessment to determine when and where non-native plants could be used and where native plants should be used. These sometimes simple and sometimes more complex methods are determined by understanding the genius loci / sense of place, and the ‘nature’ of landscape. They are determined through the identity of landscape character, landscape quality, landscape value and sensitivity to change. A complex model using a matrix tool, determines plant use types by combining sensitivity to change of the landscape relative to the magnitude of change that would be caused through the use of non-native plant species
Prokaryotic and eukaryotic unicellular chronomics
No full textAn impeccable time series, published in 1930, consisting of hourly observations on colony advance in a fluid Culture of E. coli, was analyzed by a periodogram and power spectrum in 1961. While the original senior author had emphasized specifically periodicity with no estimate of period length, he welcomed further analyses. After consulting his technician. he knew of no environmental periodicity related to human schedules other than an hourly photography. A periodogram analysis in 1961 showed a 20.75-h period, It was emphasized that "(...). the circadian period disclosed is not of exactly 24-h length." Confirmations notwithstanding, a committee ruled out microbial circadian rhythms based on grounds that could have led to a different conclusion, namely first, the inability of some committee members to see (presumably by eyeballing) the rhythms in their own data, and second, what hardly follows. that there were-too many analyses" in the published papers. Our point in dealing with microbes and humans is that analyses are indispensable for quantification and for discovering a biologically novel spectrum of cyclicities. matching physical ones. The scope of circadian organization estimated in 1961 has become broader, including about 7-day. about half-yearly, about-yearly and ex-yearly and decadal periodisms, among others. Microbial circadians have become a field of their own with eyeballing, yet time-microscopy can quantify characteristics with their uncertainties and can assess broad chronomes (time structures) with features beyond circadians. As yet only suggestive differences between eukaryotes and prokaryotes further broaden the perspective and may lead to life's sites of origin and to new temporal aspects of life's development as a chronomic tree by eventual rhythm dating in ontogeny and phylogeny. (c) 2005 Elsevier SAS. All rights reserved.NIGMS NIH HHS [K06 GM013981, K06 GM013981-43, GM-13981
Appendix to 'Groups of units of orders in Q-algebras'
No full textIn the paper 'Groups of units of orders in Q-algebras' by A.L.S. Corner, the following result is proved: A finite group G is realisable as the group of units of an order in a Q-algebra if and only if G is a C2C4C6QDB-group and either (a) G has a direct factor of order 2, or (b) G admits a direct decomposition G=G0×G1×⋯×Gr, where G1,...,Gr are B-blocks and G0 is a C4QD-group which may be embedded as a subdirect product of copies of C4, Q, D in such a way that it contains the diagonal involution −1.
The author remarks that the final condition relating to the diagonal involution is not very pretty. He believes that it could be replaced by a more desirable requirement that there exists an element g0 of order 4 in G such that CG(g0) is a 2-group. In the appendix by Federico Menegazzo, the proof of the "more desirable'' requirement is provided
A cross-continental test of the Enemy Release Hypothesis: leaf herbivory on Acer platanoides (L.) is three times lower in North America than in its native Europe
No full textAcer platanoides (Norway maple) is a widespread native tree species in Europe. It has been introduced to North America where it has often established dense stands in both secondary woodlands and relatively undisturbed mature woodlands. In Europe A. platanoides is also extending its original range, but generally seems to exist at much lower densities. One explanation for the 'aggressiveness' of invasive plants such as A. platanoides is that they have left behind pests and diseases which limit their population densities in their native lands (the enemy release hypothesis or ERH). To assess the ERH for Norway maple, a large network of collaborators assessed leaf herbivory rates in populations throughout Europe and North America. We found significantly lower total leaf herbivory (1.6% +/- A 0.19, n = 21 vs. 7.4% +/- A 1.94, n = 34) and lower fungal damage (1.0% +/- A 0.35, n = 13 vs. 3.7% +/- A 0.85, n = 34) in North America than in Europe over a 2 year period, which is consistent with the predictions of the Enemy Release Hypothesis. Across years, the average total leaf herbivory was significantly correlated with average annual temperature of the site (P 0.05). Furthermore, only populations in Europe showed very high levels of herbivory (e.g., nine sites had total leaf herbivory ranging from 10.0 to 51.2% in at least 1 year) or leaf fungal damage (only one site in North America showed high levels of fungal damage in 1 year), suggesting the possibility of more frequent episodic outbreaks in the native range. Leaf herbivory and fungal damage are only two aspects of consumer pressure and we do not know whether the differences reported here are enough to actually elicit release from top-down population control, but such large scale biogeographic differences in herbivory contribute towards understanding exotic invasions.VEGA [2/5152/25]; Sponsored Research Office of The University of Montan
Maintaining the Own Responsibility
No full textThis chapter introduces an alternative concept against the dominating trend of a complete outsourcing of IT services, especially in small and medium-sized enterprises (SME). It argues that the undiscriminating adoption of this trend tends to reduce IT on a cost factor and neglects the importance of specific IT knowledge for the continuous improvement of business processes. Also, it neglects the importance of a “communication interface” between the IS users on the one hand and the software development and IT production on the other hand. In opposition to leading management trends, this chapter will present an approach that bases on an internal competence centre for IS and that demands a steady communication between the IT staff and the various departments. In this approach, only selected IT services are externalized and the continuing growth of specific IS knowledge is essential. This approach was developed since the end of the 1990s at the building society, with about 100 employees, in which the author is working.</jats:p
