POST-FIRE DEVELOPMENT OF CANOPY STRUCTURE IN A MEDITERRANEAN SHRUB,QUERCUS COCCIFERAL.

The canopy structure, including density, the apportionment of biomass in basal stem and branch diameter classes and foliage, and leaf characteristics, was examined for a dense Quercus coccifera garrigue in southern France at 3,9, and 33 years since the last fire. Indications of changing canopy structure were considered in relation to succession, regeneration strategies, water relations, and flammability. Other shrub species and herbs are most abundant at 3 and 33 years following fire, but at 9 years Q. coccifera is especially dominant. At 9 years the density of stems in the middle range of diameter classes is greatest, overall biomass reaches its peak, and leaf area index is highest. The canopy closes quickly, but by 33 years evidence for self-thinning, slowed but continuing basal sprouting, and declining leaf area and biomass is found; senescence may be beginning, but it is not an important factor in the first 33 years of canopy development. The continuity of the below-ground biomass in this and similar vegetation probably plays an important role in determining the optimum tactics for ramets through cyclic successions. Renewed competition in later years in a more open canopy of Q. coccifera, as indicated by the data, probably would be limited by recurrent fire. [Key words: biomass, canopy, density, mediterranean, physiognomy.]     

SOIL VARIATION ON NORTH AND SOUTH SLOPE CATENAS ON A KAME IN SOUTHEAST WISCONSIN

Soils from two catenas on north-and south-facing slopes of a kame were analyzed to determine the effect of lithology, topography, and microclimate on profile development. In loess on the north-facing slope, where microclimate favored CaCO₃ dissolution and clay translocation, pedogenesis was rapid and an A-E-Bt-C profile developed. In contrast, an A-Bt-C profile developed on the south-facing slope. In gravel where limestone/dolostone dissolution was slow, A-C profiles were found and CaCO₃ was depleted to a ≤ 25-cm depth, 20± cm less than reported for similar Michigan soils. Slopewash and runoff are inferred to have caused silt accumulations and greater infiltration at the base of ≥ 20° slopes, resulting in a thicker solum in foot-and toe-slope positions, whereas on slopes of ≤ 7° infiltration and interflow are the dominant processes, resulting in a thicker solum on the transportational midslope. The differences in soil profile development are attributed to sediment facies changes at 25- to 50-cm depth and resulting groundwater movement. [Key words: soil development, soil spatial variability, kame slope catena, Wisconsin.]     

ENVIRONMENTAL CONSEQUENCES OF HUMAN ACTIVITY ON THE YELLOW RIVER AND ITS DELTA,CHINA

The Yellow River is unique among the major rivers of the world because of its extremely heavy sediment load in relation to its small discharge. The Yellow River has changed courses numerous times during the past 5000 to 6000 years. With its large sediment load, most of which comes from the Loess Plateau of central China, the river has created a number of deltas along the coast of northern China. The abandoned deltas are eroding, whereas the present delta being formed in Bohai Bay is growing rapidly. Human activity, including extensive agriculture, heavy water consumption, the use of river-control structures, and war, has been responsible for many of the changes occurring in the Yellow River and its delta. [Key words: hydrology, loess, floods, Yellow River, Bohai Bay, China.]     

An analysis of intra-event precipitation variability for the United States (1980–2010)

Hourly precipitation data were collected from 143 first-order US weather stations during the period from 1980 to 2009 to assess the internal distribution of precipitation events lasting at least three hours. A total of 46,595 individual precipitation events were identified and evaluated using the mean, standard deviation, skewness, kurtosis, and the number of peaks occurring within an event. Mean event duration is longest along the West and Northwest coasts, the Mid-South, the Mid-Atlantic, and the Northeast; while shorter-duration events are more frequent in the Rocky Mountains, the Southwest, and the Great Plains. Mean event precipitation and standard deviation are greatest along the Gulf Coast and decrease inland. Precipitation events are positively skewed, indicating that more precipitation tends to occur earlier in the event. The most positively-skewed events are also located in regions flanking the Gulf of Mexico, while less-skewed events are common in the Northwest and Rocky Mountain regions. Event kurtosis is negative throughout the entire USA, with the highest negative values generally west of the Front Range, where cyclonic development and transition produce more evenly distributed precipitation within storms. Intra-event precipitation maxima were also evaluated, with western Florida and the desert Southwest having the greatest number per event.     

A comparative analysis of DEM‐based models to estimate the solar radiation in mountainous terrain

Daily solar radiation estimates of four up‐to‐date solar radiation models (Solar Analyst, r.sun, SRAD and Solei‐32), based on a digital elevation model (DEM), have been evaluated and compared in a Mediterranean environment characterized by a complex topography. The models' estimates were evaluated against 40 days of radiometric data collected in 14 stations. Analyzed sky conditions ranged from completely overcast conditions to clear skies. Additionally, the role of the spatial resolution of the DEM has been evaluated through the use of two different resolutions: 20 and 100 m. Results showed that, under clear‐sky conditions, the daily solar radiation variability in the study area may be reasonably estimated with mean bias errors under 10% and root mean square error values of around 15%. On the other hand, results proved that the reliability of the estimates substantially decreases under overcast conditions for some of the solar radiation models. Regarding the role of the DEM spatial resolution, results suggested that the reliability of the estimates for complex topography areas under clear‐sky conditions improves using a higher spatial resolution.     

Spatio-temporal analysis of tree height in a young cork oak plantation

Cork oak is one of the most valuable natural forest genera in the Mediterranean basin. Modelling cork oak growth has been a challenge for foresters in recent years because of strong site and genetic influences, below-ground competition, management regimes and age effects. Because cork productivity is related to forest height, which is, in turn, related directly with site characteristics, an increase in the accuracy of height prediction implies improved productivity estimation. A Bayesian maximum entropy (BME) geostatistical model was applied to characterize the space–time pattern of height of young cork oak in a forest stand from central Sardinia in the years 2000, 2002, 2003, 2006 and 2008. Cork oak height maps were produced for each of the 5 years. The main goals were to analyse and interpret through time (i) the changes in spatial correlation and (ii) the changes in spatial distribution of cork oak height. The plantation was characterized by an increasing spatial dependence through time, whereas the temporal range was 2 years. Cork oak height was significantly correlated with wind speed (reduced by a neighbouring forest) in all the years implying a single trend. The correlations were larger for 2006 and 2008 than for previous years. Three other environmental variables (shade, elevation and slope) were less significant and their influence restricted to 2 years only. This research has several implications for the management of cork oak in the young phase.     

Statistics-based outlier detection for wireless sensor networks

Wireless sensor network (WSN) applications require efficient, accurate and timely data analysis in order to facilitate (near) real-time critical decision-making and situation awareness. Accurate analysis and decision-making relies on the quality of WSN data as well as on the additional information and context. Raw observations collected from sensor nodes, however, may have low data quality and reliability due to limited WSN resources and harsh deployment environments. This article addresses the quality of WSN data focusing on outlier detection. These are defined as observations that do not conform to the expected behaviour of the data. The developed methodology is based on time-series analysis and geostatistics. Experiments with a real data set from the Swiss Alps showed that the developed methodology accurately detected outliers in WSN data taking advantage of their spatial and temporal correlations. It is concluded that the incorporation of tools for outlier detection in WSNs can be based on current statistical methodology. This provides a usable and important tool in a novel scientific field.     

Revaluation of the natural-resource potential of Ukraine

We provide a rationale for the technique of revaluating the natural-resource potential which is built upon the natural crop yield of Ukrainian lands obtained, with the observance of rotation cropping and by implementing the complex of mechanical tillage operations without fertilizer application. An assessment is made of Ukraine’s natural-resource potential within the context of three physical-geographical countries, four zones, three subzones, and 14 krais.