Suchergebnisse

10 páginas.-- 4 tablas.-- 60 referencias.-- Supporting InformationAdditional Supporting Information may be found in the online version of this article ; 1. Understanding the proximate factors that govern the widespread mast-seeding process is a question of considerable interest that remains poorly understood. The identity and effect of these factors may vary among coexisting species that differ in leaf habit, potentially resulting in temporally asynchronous patterns of seed production. 2. In this study, we aim to identify the proximate causes of mast-seeding using two oak species with contrasting leaf habit that coexist in southern Spain, the deciduous Quercus canariensis and the evergreen Q. suber. Simultaneously, we review the literature on environmental drivers of mast-seeding in Mediterranean oaks, distinguishing between evergreen and deciduous species. 3. Our results indicate that Mediterranean oaks are primarily sensitive to weather, mast-seeding being strongly correlated with water availability and air temperature, mainly in the spring and summer. 4. The two study oak species were affected by weather in quite different ways, most likely because of different abiotic requirements as well as contrasting functional strategies of resource use and biomass allocation. Specifically, annual seed production in Q. canariensis was more severely limited by drought than in Q. suber, but responded positively to warmer spring temperatures. 5. Q. canariensis showed a large interannual variability, whereas Q. suber exhibited much more constant seed production. These two species also exhibited a very low level of synchrony in their temporal patterns of seed crop size, most likely due to phenological differences in the processes of flowering and seed maturation. 6. Synthesis. Our results indicate that weather plays a crucial role as a proximate driver of mastseeding in Mediterranean oaks. We hypothesize that the current abundance of co-occurring species that differ in leaf habit could be altered under future climate change scenarios. The decline of seed production with drier conditions will be potentially greater in deciduous species, particularly those inhabiting wetter sites. Alternatively, the expected warmer temperatures could negatively affect evergreen species as a consequence of their more conservative strategy of biomass allocation. Our findings suggest that understanding how species with different functional or phenological attributes adjust their reproductive abilities to weather may enable us to infer the effects of ongoing environmental changes on population recruitment and dynamics. ; We thank the "Consejería de Medio Ambiente" (Andalusian Government) and the technical staff of Los Alcornocales Natural Park, for the facilities and support to carry out our fieldwork. We are very grateful to María Amían, Ana Pozuelos, Rocío Sánchez and other undergraduate students for field assistance. This study was supported by a postdoctoral contract of the Andalusian Government to IMPR, by the Spanish MEC projects Heteromed (REN2002- 4041-C02-02), Dinamed (CGL2005-5830-C03-01) and Interbos (CGL2008-04503-C03-01), and by the Andalusian Anasinque-PE2010-RNM-5782 project. WDK was supported by the National Science Foundation (grant DEB-0816691). ; Peer reviewed

13 páginas.-- 2 figuras.-- 7 tablas.-- 47 referencias.-- Additional supporting information may be found in the online version of this article at http://onlinelibrary.wiley.com/doi/10.1002/ecy.1490/suppinfo.-- Koenig_et_al ; Although the functional basis of variable and synchronous seed production (masting behavior) has been extensively investigated, only recently has attention been focused on the proximate mechanisms driving this phenomenon. We analyzed the relationship between weather and acorn production in 15 species of oaks (genus Quercus) from three geographic regions on two continents, with the goals of determining the extent to which similar sets of weather factors affect masting behavior across species and to explore the ecological basis for the similarities detected. Lag-1 temporal autocorrelations were predominantly negative, supporting the hypothesis that stored resources play a role in masting behavior across this genus, and we were able to determine environmental variables correlating with acorn production in all but one of the species. Standard weather variables outperformed "differential-cue" variables based on the difference between successive years in a majority of species, which is consistent with the hypothesis that weather is linked directly to the proximate mechanism driving seed production and that masting in these species is likely to be sensitive to climate change. Based on the correlations between weather variables and acorn production, cluster analysis failed to generate any obvious groups of species corresponding to phylogeny or life-history. Discriminant function analyses, however, were able to identify the phylogenetic section to which the species belonged and, controlling for phylogeny, the length of time species required to mature acorns, whether they were evergreen or deciduous, and, to a lesser extent, the geographic region to which they are endemic. These results indicate that similar proximate mechanisms are driving acorn production in these species of oaks, that the environmental factors driving seed production in oaks are to some extent phylogenetically conserved, and that the shared mechanisms driving acorn production result in some degree of synchrony among coexisting species in a way that potentially enhances predator satiation, at least when they have acorns requiring the same length of time to mature. ; This study was supported by National Science Foundation grant DEB- 1256394; Andalusian projects Anasinque- PE2010- RNM- 5782, P07- RNM02688, and P10- AGR6501; Spanish MEC projects Heteromed REN2002- 4041- C02- 02, Dinamed CGL2005- 5830- C03- 01, and Interbos CGL2008- 04503- C03- 01; a postdoctoral contract of the Andalusian Government (to IMPR); and a post-doctoral contract of the Operative Program of the European Social Fund (to MDC). ; Peer reviewed

Context. Grazing by large herbivores may have a considerable influence on ground vegetation as well as on the species composition and abundance of granivors (e.g. small rodents) and this may affect forest regeneration. Very few studies have focussed on the effects of herbivore disturbance on forest regeneration by looking at the modified seed-hoarding behaviour of small rodents.
Aims. To test the indirect effects that grazing disturbance by domestic animals has on seed dispersal through the modified seed-hoarding behaviour of small rodents.
Methods. We looked at the differences in seed removal and caching of Liaodong oak (Quercus liaotungensis) by small rodents between a plot that was grazed and a plot that was ungrazed by domestic goats in a warm-temperate forest in northern China in 2006 (a non-mast-seeding year) and 2008 (a mast-seeding year).
Key results. Seed removal and caching by small rodents were significantly higher in the grazed plots, especially in the mast-seeding year (2008). Significantly more seeds were buried in soil during the mast-seeding year (2008) compared with the non-mast-seeding year (2006).
Conclusions. Grazing-induced disturbance might stimulate hoarding efforts by seed-caching rodents. Mast seeding benefits seed survival and forest regeneration.
Implications. The presence of large herbivores is likely to benefit early seed dispersal in forests by increasing the hoarding activities of rodents.

Abstract
In 1968 the American military launched Operation Igloo White (OIW), seeding the mountainous forests of the Ho Chi Minh Trail in Laos and Vietnam with a network of seismic, olfactory, and auditory sensors that picked up and relayed signals to data bunkers in Thailand where enemy locations were mapped in real time. The author argues that operating in such a continually evolving, mosaiclike environment required the American military to develop a fine-graine attunement to the forested trail in which they could track an elusive enemy. Attunement, or this intimate spatial knowledge, was both a media habit developed and enforced through sensors and their monitoring of environments, as well as a form of a priori knowledge required to develop and operationalize sensors in a forested space (in the first place). The operation, and thus this essay, writes a history of media habits and practices like militarized attunement—in which the capture of textured environmental data (of the forest) becomes tethered to the capture of the enemy. The author narrativizes this militarized attunement to the forest via deployment (the attunement to forest and its biogeographical considerations that shape sensor-embedding practices), detection (the registering and interpretation of the sensory data of the forest and the enemies in it), and deception (the use of camouflage and the tactical deception to the sensors the North Vietnamese respond with)—the three sensory practices that roughly map onto the biography of OIW itself.

Die aktuellen weltpolitischen Entwicklungen werfen ein Schlaglicht auf die zentrale Bedeutung der Pflanzenproduktion für die menschliche Ernährung. Die Aussaat als wichtiger Teilprozess wird aktuell intensiv in die Optimierung der Pflanzenproduktion als Gesamtsystem einbezogen. Neue Antriebskonzepte wie z. B. Nexat oder autonome Antriebseinheiten eröffnen für die Sätechnik praxistaugliche Perspektiven einer Integration in ganzheitliche Maschinensysteme. Drill- und Einzelkornsämaschinen erhalten neue Möglichkeiten, um Saatgut, Dünger und chemische Wirkstoffe zeitgleich in verschiedenen Kombinationen und räumlichen Zuordnungen auszubringen. Die Einzelkornsaat von Getreide bekommt durch aktuelle Entwicklungen weitere Impulse. Detailverbesserungen an zentralen Baugruppen wie Vereinzelungs- und Tiefenführungssystemen bilden wichtige Innovationen der Sätechnik. ; Current global political developments highlight the central importance of plant production for human nutrition. Sowing as an important sub-process is currently being intensively included in the optimization of plant production as an overall system. New drive concepts such as Nexat or autonomous drive units open up practical perspectives for integration into integrated machine systems for sowing technology. Seed drills and precision seed drills are given new opportunities to apply seeds, fertilizers and chemical agents in different combinations and spatial allocations at the same time. The precision sowing of grain is getting further impetus from current developments. Improvements in the details of central assemblies such as singulation and depth control systems represent important innovations in sowing technology.

AbstractTechnology is critical to international development, but the theory and practice of leveraging technology for humanitarian goals is not well developed. Technology Seeding is thus presented as a comprehensive model that draws upon proven design and technology transfer scholarship. Key characteristics include (i) design as the point of intervention, (ii) the building of technology from first principles (both scientific and disciplinary) and (iii) local adaptation. A case study that led in part to the methodology's development is presented. Technology Seeding, which enables and empowers the marginalized, is shown to be well suited for socially just long‐term sustainable development. Copyright © 2012 John Wiley & Sons, Ltd.

It is an understatement to say that people are confused about cloud seeding. While it has been called "the crime of the century" and outlawed in Pennsylvania, the governments of the dry, western part of the United States continue to spend tax revenues on cloud seeding to increase water supplies. During the past five years, I have talked with officials responsible for decisions regarding cloud seeding programs in about 15 states of the U.S.A., in a dozen other countries, and in the World Meteorological Organization. Some of the officials involved are experts in atmospheric physics, but most are not. Members of the latter group have expressed a great need for reliable, concise information about how cloud seeding works and what it does to the weather. This book is addressed to them and to all students of the environmental sciences in general and of the atmospheric sciences in particular who need answers to those questions. The book should be useful to graduates of a university program in any of the physical sciences or engineering, and to upperclassmen in those subjects. A review of basic cloud physics is provided to make the presentation meaningful to persons with only minimal preparation in meteorology. The presentation of statistical methods used in the evaluation of cloud seeding projects presupposes no special knowledge of statistics on the part of the reader. The subject of weather modification has been studied by meteorologists, physicists, chemists, statisticians, lawyers, ecologists, economists, and sociologists, each from a different point of view. Disagreements among these groups sometimes obscure the larger issues. For example, the debate that followed the publication of the Final Report of the Advisory Committee on Weather Control in 1957 was dominated by statisticians. The real question of whether or not the Advisory Committee was correct in concluding that cloud seeding had increased precipitation in mountains of the western U.S.A. was obscured by debate over such details as the relative merits of square root and gamma transfonnations for nonnalizing rainfall statistics. This book attempts to present a general view of the subject but with the emphasis on physical rather than legal, economic, or sociological aspects. The current state of the art is described, and some,promising areas for additional research are pointed out. Underlying the entire book is the author's conviction that the evidence on the effects of cloud seeding can be sifted to yield a coherent picture that is consistent with the laws of atmospheric physics.

This paper provides nested sets and vector representations of knockout tournaments. The paper introduces classification of probability domain assumptions and a new set of axioms. Two new seeding methods are proposed: equal gap seeding and increasing competitive intensity seeding. Under different probability domain assumptions, several axiomatic justifications are obtained for equal gap seeding. A discrete optimization approach is developed. It is applied to justify equal gap seeding and increasing competitive intensity seeding. Some justification for standard seeding is obtained. Combinatorial properties of the seedings are studied.