Latest precambrian (Cadomian) zircon ages, Nd isotopic systematics and P-T evolution of granitoid orthogneisses of the Erzgebirge, Saxony and Czech Republic

Single zircons from two orthogneiss complexes, the Grey Gneiss and Red Gneiss, the lowermost tectonic units in the Erzgebirge, were dated. The grey Freiberg Gneiss is of igneous origin and has a ²⁰⁷Pb/²⁰⁶Pb emplacement age of 550±7 Ma. A quartz monzonite from Lauenstein contains idiomorphic zircons with a mean ²⁰⁷Pb/²⁰⁶Pb age of 555±7 Ma as well as xenocrysts ranging in age between 850 and 1910 Ma. Red gneisses from the central Erzgebirge contain complex zircon populations, including numerous xenocrysts up to 2464 Ma in age. The youngest, idiomorphic, zircons in all samples yielded uniform ²⁰⁷Pb/²⁰⁶Pb ages between 550±9 and 554±10 Ma. Nd isotopic data support the interpretation of crustal anatexis for the origin of both units. _Nd(t) values for the grey gneisses are –7.5 and –6.0 respectively, (mean crustal residence ages of 1.7–1.8 Ga). The red gneisses have a wider range in _Nd(t) values from –7.7 to –2.8 (T _DM ages of 1.4–1.8 Ga). The zircon ages document a distinct late Proterozoic phase of granitoid magmatism, similar in age to granitoids in the Lusatian block farther north-east. However, Palaeozoic deformation as well as medium pressure metamorphism ( 8 kbar/600–650° C) are identical in both gneiss units and distinguish these rocks from the Lusatian granitoids. The grey and red gneisses were overthrust by units with abundant high-pressure relicts and a contrasting P-T evolution. Zircon xenocryst and Nd model ages in the range 1000–1700 Ma are similar to those in granitoid rocks of Lusatia and the West-Sudetes, and document a pre-Cadomian basement in parts of east-central Europe that, chronologically, has similarities with the Sveconorwegian domain in the Baltic Shield.     

Gro?forschung mit anderen Namen

Naturwissenschaften Aktuell

Großforschung mit anderen Namen     

The ladybird<Emphasis Type="Italic"> Thalassa saginata</Emphasis>, an obligatory myrmecophile of<Emphasis Type="Italic"> Dolichoderus bidens</Emphasis> ant colonies

The larvae and pupae of the ladybird Thalassa saginata develop inside colonies of the dolichoderine ant Dolichoderus bidens. This association is the first specific and obligatory relationship recorded between ants and ladybirds. The ants provide shelter and protection to the larvae but the diet of the latter remains unclear. The integration of T. saginata larvae into the ant colonies is achieved by mimicking the cuticular patterns of the ants brood. Moreover, the larvae secrete substances from their hairs and anal gland that are likely to enhance their attractiveness.     

Biomineralization in plants as a long-term carbon sink

Carbon sequestration in the global carbon cycle is almost always attributed to organic carbon storage alone, while soil mineral carbon is generally neglected. However, due to the longer residence time of mineral carbon in soils (10²–10⁶ years), if stored in large quantities it represents a potentially more efficient sink. The aim of this study is to estimate the mineral carbon accumulation due to the tropical iroko tree (Milicia excelsa) in Ivory Coast. The iroko tree has the ability to accumulate mineral carbon as calcium carbonate (CaCO₃) in ferralitic soils, where CaCO₃ is not expected to precipitate. An estimate of this accumulation was made by titrating carbonate from two characteristic soil profiles in the iroko environment and by identifying calcium (Ca) sources. The system is considered as a net carbon sink because carbonate accumulation involves only atmospheric CO₂ and Ca from Ca-carbonate-free sources. Around one ton of mineral carbon was found in and around an 80-year-old iroko stump, proving the existence of a mineral carbon sink related to the iroko ecosystem. Conservation of iroko trees and the many other biomineralizing plant species is crucial to the maintenance of this mineral carbon sink.     

Erratum

Naturwissenschaften Aktuell     

A participatory approach to the establishment of a baseline scenario for a reforestation Clean Development Mechanism project

This paper is part of a two-year study to investigate the feasibility of initiating a Clean Development Mechanism (CDM) project in an indigenous community of Eastern Panamá, Ipetí-Emberá. We use participatory mapping and matrices as well as household surveys to develop a land-use/land-cover baseline scenario and examine the role of local participation in assessing land-use change. In Ipetí, land-use change has not occurred in a linear way over the last decades, and our data unveils socio-economic factors as potential key drivers of change. The concordance that we observed between geographic information and individual and collective perceptions of land-use change substantiates the possibility of using local knowledge in the establishment of baseline data for CDM projects. Our calculations suggest that the total carbon (C) stocks in the Tierra Colectiva (TC) of Ipetí-Emberá in 2004 represents a 47% reduction from the estimated C stock at the onset of settlement in the early 1970’s. Results from the participatory assessments predict that, in 2024 and in absence of a CDM project, the C stocks will decline from 301,859 t C in 2004 to 155,730 t C, which constitutes a reduction of 52%. The scenario with CDM estimates C stocks of 305,853 t C for 2024, a value slightly superior to the 2004 value. In the TC there is ground to believe that cattle ranching is likely to become an ever more important activity as the population is young and growing and cannot easily move elsewhere. Forests tend to be cleared for cultivation while pastures are established on short fallows. Our baseline scenario underlines the potential for a CDM project to make a significant difference in the future C stocks of this landscape.     

CLIMATE CHANGE AND NATURAL HAZARDS IN NORTHERN CANADA: INTEGRATING INDIGENOUS PERSPECTIVES WITH GOVERNMENT POLICY

A study of the relationship between natural hazards and climate change in the international context provides the background for a discussion of the expected changes. In the context of this global discussion, this paper reviews the current perspectives of those natural hazards that are likely to be influenced by climate change, using northern Canada as a regional case study. The northern implications of the United Nations Framework Convention on Climate Change are examined, including the status of climate change action by the northern territorial governments, the evolving role of indigenous people, and the responsibility for climate change impacts. The difficulties surrounding natural hazards research in remote locations, and the approaches of indigenous people to natural hazards are then presented. The paper concludes with a suggested policy approach for climate change and natural hazards in northern Canada, underscoring the need for more comprehensive adaptive strategies to complement the current tendency to focus on the mitigation of greenhouse gases produced in this region.     

A course in Environmental Planning and Management

Summary This paper describes a 13-weeks, third-year course in Environmental Planning and Management developed and taught by the authors. Initiated in 1969, the course consists of a mix of lectures, seminars, workshop/laboratory sessions and field-based projects. The objectives of the course are for students: to become aware of the need for, and the complexities of, environmental management; to be able to criticise constructively work done by environmental agencies and consultants, managers and decision makers; and to learn and apply some of the methods and techniques used in environmental management.Topics covered by the current syllabus are: concepts of resource and environment; constitutional aspects; international law and the environment; Australian and Canadian environmental legislation and agencies; human manipulation of ecosystems; energy subsidies; modification of biogeochemical cycles; population dynamics and cropping; fisheries; national parks and reserves—policies in different countries; international heritage areas; environmental assessment (including impact assessment, land evaluation, land capability and land suitability assessment); and regional, integrated land-use and environmental planning and management. Techniques taught include: field surveys and interviewing; laboratory analysis of selected water quality, sediment and soil parameters including nutrient concentrations, heavy metal and pesticide residues; and for some students, applications of geographic information systems (GIS) technology following preceding GIS courses.A major problem is selecting the most appropriate mix between the social and natural sciences—appropriate, first in terms of students' heterogeneous skills and backgrounds, and second, in terms of understanding the causes of environmental problems and issues, and devising practicable solutions.