Exotic Smooth Structures on Small 4-Manifolds

Let M be either CP^2#3CP^2bar or 3CP^2#5CP^2bar. We construct the first example of a simply-connected symplectic 4-manifold that is homeomorphic but not diffeomorphic to M.Comment: 11 page

Nereid from space: rotation, size and shape analysis from K2, Herschel and Spitzer observations

In this paper, we present an analysis of K2 mission Campaign 3 observations of the irregular Neptune satellite, Nereid. We determined a rotation period of P = 11.594±0.017 h and amplitude of Δm = 0.0328m ± 0.0018m, confirming previous short rotation periods obtained in ground-based observations. The similarities of light-curve amplitudes between 2001 and 2015 show that Nereid is in a low-amplitude rotation state nowadays and it could have been in a high-amplitude rotation state in the mid-1960s. Another high-amplitude period is expected in about 30 yr. Based on the light-curve amplitudes observed in the last 15 yr, we could constrain the shape of Nereid and obtained a maximum a:c axis ratio of 1.3:1. This excludes the previously suggested very elongated shape of a:c ≈ 1.9

Landscape evolution and climate in Madagascar: lavakization in the light of archive precipitation data

In Madagascar, soil erosion is significant even when it is compared to world averages. A resulting special geomorphic feature is a form of gully erosion known as lavaka that appears in the highlands of the country. Lavakization (the generation and development of these features) is due to rather unique multifactorial environmental conditions. Among many factors (geology, soil composition, human activities, etc.), the spatial and temporal distribution of precipitation is a key factor influencing the behaviour of lithology and the vegetation cover of the island. The inter-annual variability in precipitation seems to be responsible for the enhanced generation of small cracks that might eventually lead to the development of a gully. However, the way of the development of such gullies is unknown. To what extent the actual precipitation pattern contributes to the aforementioned phenomenon has not yet been studied in great detail. This paper aims to analyze lavaka distribution with GIS methods and to study the relation between lavaka density and climatic conditions. Study areas have been designated throughout the country and lavakas have been identified using satellite imagery. Archive climate data of the study areas have been used to understand the influence of the weather on gully density. Data show that the spatial distribution of precipitation is connected to the appearance of lavakas to a given extent and its effect is further strengthened by the tropical cyclones. However, neither the amount of the precipitation, nor its variability alone can explain the high variation found in the spatial distribution of lavakas. Further multidisciplinary studies are necessary to draw conclusions about lavaka formation and to describe the process of lavaka development.En Madagascar, la erosión del suelo es muy elevada, incluso cuando se compara con los promedios del resto del mundo, dando lugar a formas de relieve especiales, conocidas como lavakas, que aparecen en las regiones montañosas de Madagascar. La “lavakización” (generación y evolución de estas formas) se debe a una multitud de condiciones ambientales únicas. De entre las muchas condiciones, (geología, composición del suelo, influencia antrópica, etc.), la distribución espacial y temporal de la precipitación es el factor más importante para explicar el comportamiento erosivo de la litología y las características de la cubierta vegetal de la isla. La ocurrencia de estaciones secas y lluviosas es aparentemente responsable del crecimiento de pequeñas grietas que eventualmente pueden conducir al desarrollo de lavakas. Sin embargo, se desconoce cómo se desarrollan esos barrancos. Además, la pregunta de hasta qué punto la precipitación y su pauta afecta al fenómeno mencionado todavía no ha sido contestada. El objetivo de este artículo es analizar la distribución de lavakas con métodos de GIS y examinar la relación entre su densidad y las condiciones climáticas. Las áreas de estudio han sido elegidas a lo largo del país, y las lavakas han sido identificadas con la ayuda de imágenes de satélite. Se han utilizado datos climáticos para comprender la influencia del clima en la densidad de los barrancos. Los datos de la precipitación nos permiten establecer una correlación entre la aparición de los barrancos y la distriubución espacial de la precipitación. Además, su efecto es incentivado adicionalmente por ciclones tropicales. No obstante, ni la cantidad o la variabilidad de la precipitación por sí solas pueden explicar la variedad existente en la distribución espacial y el tamaño de las lavakas. Nuevas investigaciones multidisciplinares son necesarias para conocer mejor los procesos de desarrollo y la aparición de lavakas

High-Resolution transect sampling and multiple scale diversity analyses for evaluating grassland resilience to climatic extremes

Diversity responses to climatic factors in plant communities are well understood from experiments, but less known in natural conditions due to the rarity of appropriate long-term observational data. In this paper, we use long-term transect data sampled annually in three natural grasslands of different species pools, soils, landscape contexts and land use histories. Analyzing these specific belt transect data of contiguous small sampling units enabled us to explore scale dependence and spatial synchrony of diversity patterns within and among sites. The 14-year study period covered several droughts, including one extreme event between 2011 and 2012. We demonstrated that all natural grasslands responded to droughts by considerable fluctuations of diversity, but, overall, they remained stable. The plant functional group of annuals showed high resilience at all sites, while perennials were resistant to droughts. Our results were robust to changing spatial scales of observations, and we also demonstrated that within-site spatial synchrony could be used as a sensitive indicator of external climatic effects. We propose the broad application of high-resolution belt transects for powerful and adaptive vegetation monitoring in the future

Solving the conflict between intensive and extensive approaches: transect based sampling design for comparative studies on fine scale plant community organization

Background and Aims: Non-equilibrium ecological paradigm considers plant community as a complex dissipative system, which calls for a methodology with explicit representation of spatiotemporal patterns. However, recording vegetation patterns at this fine scale is time consuming and labour intensive. In contrast, understanding general rules of community organization and vegetation structure would require large number of comparative case studies. There is a clear trade-off between these intensive and extensive aspects in ecological applications. Here, we explore how field sampling techniques can be optimized compromizing between high resolution and large extent data collections. The coordinated distributed experiments and surveys based on these optimized sampling techniques might open new perspectives in comparative community ecology and macroecology. Materiai & Methods We used simulated data and field patterns recorded in form of spatial coordinates of plant individuals or presence of species in high resolution grids. Applying computerized resampling techniques we tested how coenostate variables will change by changing the sampling parameters (resolution, extent and the shape of sampled area). We used information theory models for analyses which represent complex community patterns (beta diversity of species combinations and species associations) as a function of spatial resolution. (Campetella et al. 2004). Main Results & Interpretations Results did not differ between high resolution grid data and spatial coordinate data. The absolute values of diversity and spatial dependence were similar between grids and transects, while the related characteristic scales slightly changed. Although scales were slightly biased when measured by transects, all ordering relations (i.e. differences between the compared vegetation types) remained invariant. Decreasing the spatial extent of samples resulted in strong increase of stochastic variance and produced artefacts. These problems were less pronounced when transects were used or the shape of grids become elongated. Comparing the effects of different sampling parameters, sample extent was the most critical. Using the same extent, transects give more representative data. Transect sampling was also much faster than other sampling methods. We concluded that resolution and extent could be optimized if long (50 m) transects of contagious 5 cm x 5 cm sampling units were used. This protocol was tested and proved to be applicable in a wide range of vegetation types including forest herb layer communities, grasslands in old fields, tall- and shortgrass steppes, mountain grasslands and semi-desert communities (Gosz et al. 2000, Virágh et al. 2008). We propose using this sampling design in future coordinated distributed experiments and surveys for studying non-equilibrium dynamics and assembly rules of vegetation in a more operative way and improving the predictability of vegetation processes