Spatial and temporal patterns of greenness on the Yamal Peninsula, Russia: interactions of ecological and social factors affecting the Arctic normalized difference vegetation index

The causes of a greening trend detected in the Arctic using the normalized difference vegetation index (NDVI) are still poorly understood. Changes in NDVI are a result of multiple ecological and social factors that affect tundra net primary productivity. Here we use a 25 year time series of AVHRR-derived NDVI data (AVHRR: advanced very high resolution radiometer), climate analysis, a global geographic information database and ground-based studies to examine the spatial and temporal patterns of vegetation greenness on the Yamal Peninsula, Russia. We assess the effects of climate change, gas-field development, reindeer grazing and permafrost degradation. In contrast to the case for Arctic North America, there has not been a significant trend in summer temperature or NDVI, and much of the pattern of NDVI in this region is due to disturbances. There has been a 37% change in early-summer coastal sea-ice concentration, a 4% increase in summer land temperatures and a 7% change in the average time-integrated NDVI over the length of the satellite observations. Gas-field infrastructure is not currently extensive enough to affect regional NDVI patterns. The effect of reindeer is difficult to quantitatively assess because of the lack of control areas where reindeer are excluded. Many of the greenest landscapes on the Yamal are associated with landslides and drainage networks that have resulted from ongoing rapid permafrost degradation. A warming climate and enhanced winter snow are likely to exacerbate positive feedbacks between climate and permafrost thawing. We present a diagram that summarizes the social and ecological factors that influence Arctic NDVI. The NDVI should be viewed as a powerful monitoring tool that integrates the cumulative effect of a multitude of factors affecting Arctic land-cover change.

Lake surface temperatures in a changing climate: a global sensitivity analysis

We estimate the effects of climatic changes, as predicted by six climate models, on lake surface temperatures on a global scale, using the lake surface equilibrium temperature as a proxy. We evaluate interactions between different forcing variables, the sensitivity of lake surface temperatures to these variables, as well as differences between climate zones. Lake surface equilibrium temperatures are predicted to increase by 70 to 85 % of the increase in air temperatures. On average, air temperature is the main driver for changes in lake surface temperatures, and its effect is reduced by ~10 % by changes in other meteorological variables. However, the contribution of these other variables to the variance is ~40 % of that of air temperature, and their effects can be important at specific locations. The warming increases the importance of longwave radiation and evaporation for the lake surface heat balance compared to shortwave radiation and convective heat fluxes. We discuss the consequences of our findings for the design and evaluation of different types of studies on climate change effects on lakes.

Characterization and differentiation of body fluids, putrefaction fluid, and blood using Hounsfield unit in postmortem CT

The purpose of the present study was to evaluate the ranges of Hounsfield unit (HU) found in body fluids, putrefaction fluids, and blood on postmortem CT and how these ranges are affected by postmortem interval, temperatures, and CT beam energy. Body fluids, putrefaction fluids, and blood from a total of 53 corpses were analyzed to determine the ranges of HU values from postmortem CT images that were taken prior to autopsy. The fluids measured in CT images were obtained at autopsy and examined in terms of macroscopic and microscopic appearances. Body fluids and blood were also collected in plastic bottles, which were subjected to CT scans at different beam energies (80-130 kV) and at various fluid temperatures (4 to 40 °C). At a postmortem interval of 1 to 4 days, the ranges of HU values of the serous fluids (13-38 HU) and the nonsedimented blood (40-88 HU) did not overlap. In the sedimented blood, the upper serum layer exhibited HU value ranges that overlapped with those of the serous fluids. The putrefaction fluids exhibited a range of HU values between 80 and -130 HU. Elevated HU values were observed in fluids with accretive cell impurities. HU values decreased slightly with increasing temperature and CT beam energy. We concluded that serous fluids and blood in fresh corpses can be characterized and differentiated from each other based on HU value ranges. In contrast, body fluids in decomposed corpses cannot be differentiated by their HU value ranges. Different beam energies and corpse temperatures had only minor influences on HU value ranges and therefore should not be obstacles to the differentiation and characterization of body fluids and blood.

Vulnerability to Heatwaves, Floods and Mass Movements in Mountainous Terrain: Test Cases in South Tyrol

South Tyrol is a region that has been often affected by various mountain hazards such as floods, flash floods, debris flows, rock falls, and snow avalanches. Furthermore, areas located in lower altitudes are often influenced by high temperatures and heat waves. Climate change is expected to influence the frequency, magnitude, and spatial extent of these natural phenomena. For this reason, local authorities and other stakeholders are in need of tools that can enable them to reduce the risk posed by these processes. In the present study, a variety of methods are applied at local level in different places in South Tyrol that aim at: (1) the assessment of future losses caused by the occurrence of debris flows by using a vulnerability curve, (2) the assessment of social vulnerability based on the risk awareness of the exposed people to floods, and (3) the assessment of spatial exposure and social vulnerability of the exposed population to heat waves. The results show that, in South Tyrol, the risk to a number of hazards can be reduced by: (1) improving documentation for past events in order to improve existing vulnerability curves and the assessment of future losses, (2) raising citizens' awareness and responsibility to improve coping capacity to floods, and (3) extending heat wave early warning systems to more low-lying areas of South Tyrol.

Debris discs around M stars: non-existence versus non-detection

Motivated by the reported dearth of debris discs around M stars, we use survival models to study the occurrence of planetesimal discs around them. These survival models describe a planetesimal disc with a small number of parameters, determine if it may survive a series of dynamical processes and compute the associated infrared excess. For the Wide-field Infrared Survey Explorer (WISE) satellite, we demonstrate that the dearth of debris discs around M stars may be attributed to the small semimajor axes generally probed if either: (1) the dust grains behave like blackbodies emitting at a peak wavelength coincident with the observed one; (2) or the grains are hotter than predicted by their blackbody temperatures and emit at peak wavelengths that are shorter than the observed one. At these small distances from the M star, planetesimals are unlikely to survive or persist for time-scales of 300 Myr or longer if the disc is too massive. Conversely, our survival models allow for the existence of a large population of low-mass debris discs that are too faint to be detected with current instruments. We gain further confidence in our interpretation by demonstrating the ability to compute infrared excesses for Sun-like stars that are broadly consistent with reported values in the literature. However, our interpretation becomes less clear and large infrared excesses are allowed if only one of these scenarios holds: (3) the dust grains are hotter than blackbody and predominantly emit at the observed wavelength; (4) or are blackbody in nature and emit at peak wavelengths longer than the observed one. Both scenarios imply that the parent planetesimals reside at larger distances from the star than inferred if the dust grains behaved like blackbodies. In all scenarios, we show that the infrared excesses detected at 22 μm (via WISE) and 70 μm (via Spitzer) from AU Mic are easily reconciled with its young age (12 Myr). Conversely, the existence of the old debris disc (2–8 Gyr) from GJ 581 is due to the large semimajor axes probed by the Herschel PACS instrument. We elucidate the conditions under which stellar wind drag may be neglected when considering dust populations around M stars. The WISE satellite should be capable of detecting debris discs around young M stars with ages ∼10 Myr.

Optimum Electron Temperature and Density for Short-Wavelength Plasma-Lasing from Nickel-like ions

Soft X-ray lasing across a Ni-like plasma gain-medium requires optimum electron temperature and density for attaining to the Ni-like ion stage and for population inversion in the View the MathML source3d94d1(J=0)→3d94p1(J=1) laser transition. Various scaling laws, function of operating parameters, were compared with respect to their predictions for optimum temperatures and densities. It is shown that the widely adopted local thermodynamic equilibrium (LTE) model underestimates the optimum plasma-lasing conditions. On the other hand, non-LTE models, especially when complemented with dielectronic recombination, provided accurate prediction of the optimum plasma-lasing conditions. It is further shown that, for targets with Z equal or greater than the rare-earth elements (e.g. Sm), the optimum electron density for plasma-lasing is not accessible for pump-pulses at View the MathML sourceλ=1ω=1μm. This observation explains a fundamental difficulty in saturating the wavelength of plasma-based X-ray lasers below 6.8 nm, unless using 2ω2ω pumping.

Crop Yield Responses to Temperature Fluctuations in 19th Century Finland: Provincial Variation in Relation to Climate and Tree Rings

Past agricultural responses to climate variability can helps us to better understand the current and future impacts of climate change on agricultural production. We studied rye (Secale cereale) and barley (Hordeum vulgare) yield responses to temperature fluctuations in Finland during the period 1861–1913. Our analyses demonstrate the high sensitivity of non-industrialised northern agriculture to temperature anomalies. We found evidence of a strong relationship between monthly and seasonal mean temperatures and crop yields. In particular, high spring temperatures were associated with higher yields. Additionally, we tested temperature-sensitive tree-ring series for their value in indicating previous agricultural outputs. The results imply that tree-ring proxies (in particular, maximum latewood density) can provide novel material for studies of historical periods and locations where instrumentally measured climate and harvest data are not available.

Climate-pollen relationships AD 1901-1996 in two small mires near the forest limit in the northern and central Swiss Alps

Climatic relationships were established in two 210Pb dated pollen sequences from small mires closely surrounded by forest just below actual forest limits (but about 300 m below potential climatic forest limits) in the northern Swiss Alps (suboceanic in climate; mainly with Picea) and the central Swiss Alps (subcontinental; mainly Pinus cembra and Larix) at annual or near-annual resolution from ad 1901 to 1996. Effects of vegetational succession were removed by splitting the time series into early and late periods and by linear detrending. Both pollen concentrations detrended by the depth-age model and modified percentages (in which counts of dominant pollen types are down-weighted) are correlated by simple linear regression with smoothed climatic parameters with one-and two-year timelags, including average monthly and April/September daylight air temperatures and with seasonal and annual precipitation sums. Results from detrended pollen concentrations suggest that peat accumulation is favoured in the northern-Alpine mire either by early snowmelt or by summer precipitation, but in the central-Alpine mire by increased precipitation and cooler summers, suggesting a position of the northern-Alpine mire near the upper altitudinal limit of peat formation, but of the central-Alpine mire near the lower limit. Results from modified pollen percentages indicate that pollen pro duction by plants growing near their upper altitudinal limit is limited by insufficient warmth in summer, and pollen production by plants growing near their lower altitudinal limit is limited by too-high temperatures. Only weakly significant pollen/climate relationships were found for Pinus cembra and Larix, probably because they experience little climatic stress growing 300 m below the potential climatic forest limit.

A Late-glacial and Holocene record of climatic change from a Swiss peat humification profile

Colorimetric measurements of alkaline extracts from two Swiss peat cores have provided a complete 14500-year-long record of peat humification, a proxy of effective precipitation. Peat from the cold Younger Dryas (11050–9550 cal. bc) was well preserved despite low levels of precipitation. A particularly dry period, peaking at c. 7100 cal. bc, is indicated by well-decomposed peat. Peat from c. 6750–4250 cal. bc shows a low degree of decomposition, indicating a wet bog surface despite relatively warm temperatures and therefore indicating high levels of precipitation. A sharp transition to higher levels of decomposition c. 4450–3750 cal. bc indicates a major transition to a drier bog surface. Subsequently, peat humification generally decreases towards the end of the deeper profile (c. cal. ad 1050), indicating a gradual return to wetter conditions. This gradual decrease is punctuated by periods of particularly low humification which appear to be due to shifts to higher levels of effective precipitation from c. 2500 to 1350 cal. bc, c. 1050 to 550 cal. bc, centered around 150 cal. bc, and from c. cal. ad 550 onwards. Anthropogenic influences appear to have affected peat humification at the site at least since the Middle Ages. This study indicates that humification in colder regions/time periods could be more affected by temperature than precipitation and vice versa.

The palaeoecological history of the Praz-Rodet bog (Swiss Jura) based on pollen, plant macrofossils and testate amoebae (Protozoa)

Stratigraphy, radiocarbon dating and analyses of pollen, plant macrofossils and testate amoebae were used to reconstruct the development and ecology of a small raised bog in a karst-dominated landscape in the Swiss Jura Mountains. Special focus was on past vegetation and on the history of Pinus rotundata in relation to anthropogenic and climatic influences. Testate amoebae were used to reconstruc-t past local soil pH and water-table depth. The inferred development of the Praz-Rodet bog typifies a classic hydroseral tefrestrialization of a small basin. Two features are specific for this site. First, the bog was much wetter than today for a long period; according to our hypothesis, this only changed as a consequence of human activities. Second, two hiatuses are present at the coring location (Younger Dryas--early Preboreal, and 4700-2800 cal. yr BP), the former probably caused by low lake productivity due to cold temperatures and the latter by the erosional activity of the adjacent small river. The date of 2800 cal. yr BP for renewed peat accumulation may be related to climatic change (Subboreal-Subatlantic transition). Pollen indicators failed to show one hiatus: an apparently complete pollen sequence is therefore no guarantee of an uninterrupted sediment accumulation. Evidence of early minor human impact on the vegetation in the Joux Valley dates back to c. 6850 calendar years, congruous with the early Neolithic in the Jura Mountains. The history of Pinuis rotindata appears to be more complex than previously believed. Human activity is clearly responsible for the present abundance of this species, but the tree was naturally present on the bog long before the first evidence of important human disturbance of the site (1500 cal. yr BP). It is suggested that, in karst-dominated landscapes, dense forests growing on mineral soils around raised bogs may significantly reduce summer evapotranspiration by acting as windbreaks. Forest clearance results in increased evapotranspiration, causing a lowering of the water table on the bog and a modification of the vegetation cover. This hypothesis has implications for the management of similar small raised bogs in karst-dominated landscape.

Rapid divergence in physiological and life-history traits between northern and southern populations of the British introduced neo-species, Senecio squalidus

Alien plants provide a unique opportunity to study evolution in novel environments, but relatively little is known about the extent to which they become locally adapted to different environments across their new range. Here, we compare northern and southern populations of the introduced species Senecio squalidus in Britain; S. squalidus has been in southern Britain for approximately 200 years and reached Scotland only about 50 years ago. We conducted common garden experiments at sites in the north and south of the species’ range in Britain. We also conducted glasshouse and growth chamber experiments to test the hypothesis that southern genotypes flower later, are more drought-tolerant, germinate and establish better at warmer temperatures, and are less sensitive to cold stress than their more northern counterparts. Results from the common garden experiments are largely consistent with the hypothesis of rapid adaptive divergence of populations of the species within the introduced range, with genotypes typically showing a home-site advantage. Results from the glasshouse and growth chamber experiments demonstrate adaptive divergence in ability to tolerate drought stress and high temperatures, as well as in phenology. In particular, southern genotypes were more tolerant of dry conditions and high temperatures and they flowered later than northern genotypes. Our results show that rapid local adaptation can occur in alien species, and they have implications for our understanding of the ecological genetics of range expansion of introduced weeds.