RESUMO
Climate change affects plant dynamics and functioning of terrestrial ecosystems. This study aims to investigate temporal changes in global vegetation coverage and biomes during the past three decades. We compared historic annual NDVI time series (1982, 1983, 1984 and 1985) with recent ones (2015, 2016, 2017 and 2018), captured from NOAA-AVHRR satellite observations. To correct the NDVI time series for missing data and outliers, we applied the Harmonic Analysis of Time Series (HANTS) algorithm. The NDVI time series were decomposed in their significant amplitude and phase given their periodic fluctuation, except for ever green vegetation. Our findings show that the average NDVI values in most biomes have increased significantly (F-value<0.01) by 0.05 ndvi units over during the past three decades, except in tundra, and deserts and xeric shrublands. The highest rates of change in the harmonic components were observed in the northern hemisphere, mainly above 30° latitude. Worldwide, the mean annual phase reduced by 9° corresponding to a 9 days shift in the beginning of the growing season. Annual phases in the recent time series reduced significantly as compared to the historic time series in the five major global biomes: by 14.1, 14.8, 10.6, 9.5, and 22.8 days in boreal forests/taiga; Mediterranean forests, woodlands, and scrubs; temperate conifer forests; temperate grasslands, savannas, and shrublands; and deserts, and xeric shrublands, respectively. In tropical and subtropical biomes, however, changes in the annual phase of vegetation coverage were not statistically significant. The decrease in the level of phases and acceleration of growth and changes in plant phenology indicate the increase in temperature and climate changes of the planet.
RESUMO
This paper will consider the contribution that changes in road geometry and driver visual information make to the incidence and distribution of road casualties in different driving environments. This relationship will be explored specifically for the Kings Highway, a major arterial road connecting Queanbeyan with coastal southern New South Wales, Australia. It introduces and suggests a new empirical approach of plotting crashes with road segmentation, calculating sinuosity indices and grades as key features of road geometry, and critical visual points as a behavioural component of road curvature, within a GIS context. It is an approach that might be used when detailed road geometry data is not available. The visualisation and segmentation approach in this research might be used for summarising crash rates and road geometry factors, and for comparing day/night and eastbound/westbound driving conditions. The results suggest some early interpretations for detailed road safety studies that might be considered at local or national levels. The rate of crashes increases according to changes in road geometry factors during the day and for eastbound travel. This is not the case for night driving where the incidence of crashes is similar on both straight and curved roads segments due to the headlight effect and limited background visual field. Crash clusters at day-time may be due to the stronger effect of road geometry (e.g. combination of curvature and vertical grade) on driver behaviour travelling eastbound. The outcomes suggest that it might be essential to consider the effect of environmental factors in any road safety and crash analysis studies.
