Interactions between land and atmosphere directly influence hydrometeorological processes and, therefore, the local climate. However, because of heterogeneity of vegetation covers these feedbacks can change over small areas, becoming more complex. This study aims to define how the interactions between soil moisture and vegetation covers influence soil temperatures in very water-limited environments. In order to do that, soil water content and soil temperature were continuously monitored with a frequency of 30 min over two and half hydrological years, using capacitance and temperature sensors that were located in open grasslands and below tree canopies. The study was carried out on three study areas located in drylands of Mediterranean climate. Results highlighted the importance of soil moisture and vegetation cover in modifying soil temperatures. During daytime and with low soil moisture conditions, daily maximum soil temperatures were, on average, 7.1 °C lower below tree canopies than in the air, whereas they were 4.2 °C higher in grasslands than in the air. As soil wetness decreased, soil temperature increased, although this effect was significantly weaker below tree canopies than in grasslands. Both high soil water content and the effect of shading were reflected in a decrease of maximum soil temperatures and of their daily amplitudes. Statistical analysis emphasized the influence of soil temperature on soil water reduction, regardless of vegetation cover. If soil moisture deficits become more frequent due to climate change, variations in soil temperature could increase, affecting hydrometeorological processes and local climate.
Soil moisture has a direct influence on biomass production, food security, and ecosystem functioning, thus resources management in water‐limited environments could be improved if feedbacks between water and vegetation were fully understood. This study tries to define the sensitivity of annual pastures under the influence of different vegetation covers to soil water availability during two contrasting growing seasons, dry and wet. For this reason, soil water content was continuously monitored during two complete hydrological years using capacitance sensors, which were gathered in soil moisture stations located in open grasslands and beneath tree canopies. Pasture growth was recorded by measurements of its height and by biomass cuts. The study was conducted on three private farms located in savanna‐like ecosystems of Spain (dehesa) with Mediterranean climate. Results highlighted the importance of the topsoil (first 15 cm) as the main layer for water supply of natural grasses. Soils below canopies registered longer and more intense water deficits than those located in grasslands. This was reflected in biomass growth, given that when growing conditions were dry, pasture yield decreased more than 40% in grasslands and more than 50% below tree canopies. The studied ecosystems occupy millions of hectares in Spain and Portugal and present a canopy cover up to 40%. If dry episodes become more frequent in the present century due to climate change, important surface, especially under trees, could become drier, less productive, and therefore more prone to land degradation.
The accuracy of different workflows using Structure-from-Motion and Multi-View-Stereo techniques (SfM-MVS) is tested. Twelve point clouds of the Corral del Veleta rock glacier, in Spain, were produced with two different software packages (123D Catch and Agisoft Photoscan), using Low Dynamic Range images and High Dynamic Range compositions (HDR) for three different years (2011, 2012 and 2014). The accuracy of the resulting point clouds was assessed using benchmark models acquired every year with a Terrestrial Laser Scanner. Three parameters were used to estimate the accuracy of each point cloud: the RMSE, the Cloud-to-Cloud distance (C2C) and the Multiscale-Model-to-Model comparison (M3C2). The M3C2 mean error ranged from 0.084 m (standard deviation of 0.403 m) to 1.451 m (standard deviation of 1.625 m). Agisoft Photoscan overcome 123D Catch, producing more accurate and denser point clouds in 11 out 12 cases, being this work, the first available comparison between both software packages in the literature. No significant improvement was observed using HDR pre-processing. To our knowledge, this is the first time that the geometrical accuracy of 3D models obtained using LDR and HDR compositions are compared. These findings may be of interest for researchers who wish to estimate geomorphic changes using SfM-MVS approaches.
Brazil is one of the main producers of pork meat in the world. It is well-known that the agricultural sector is a key component of the economic development of this country, where super-intensive fields are only competitive in the globalized market. For the farmers, the application of swine manure to fertilize the soil can increase the yearly income, but it also may cause serious environmental problems related to soil health and soil quality. In this research, we assessed the effects of applying liquid swine manure in a tropical soybean (Glycine max) plantation to better understand when this technique stops being effective and starts causing a threat to soil health and quality. Therefore, we compared values of several soil properties and the soybean yield on treated fields at 10 random points belonging to 7 different plots that were treated with the liquid swine manure over a period ranging from 0 to 15 years. The results showed a positive linear trend in soybean production from 2.45 to 3.08 Mg ha−1 yr−1. This positive trend was also recorded for some key soil parameters such as porosity and exchangeable cations content (Ca, Mg, K, and Al). Additionally, positive effects were also found for organic matter content after 10 years of application. Our findings suggest that the use of liquid swine manure has a positive effect on soybean yield and improves soil quality, particularly on mixed farms where pigs are intensively raised nearby cultivated fields.
Population growth, global warming, and increased demand for water have caused global concern about increasing water scarcity. Chile has an unequal geographical distribution of water resources. The north-central area where more than half of the country’s population lives has an availability of less than 1000 m3/hab/year. Particularly, the Coquimbo Region has been one of the most affected by drought due to the great agricultural activity in the area. In this study, surveys were carried out in rural schools and households to determine water consumption habits. The results in the schools showed that between 42% and 72% of the wastewater generated comes from the washbasin, which represents light greywater, that is, with low organic matter content. According to the data obtained, the amount of greywater generated on average reached 12 L per capita per day. These waters have the potential to be treated and reused effectively for the flow of toilets or garden irrigation. In the case of households, the generation of greywater was 84% of the total water consumed, of which, more than 86% correspond to light greywater from the shower and washbasin. On average, the light greywater generated daily reached 204 L per person per day. Due to the heterogeneity of drinking water sources in rural areas of the Coquimbo Region, the high rate of greywater generation in both schools and homes indicates the great potential for water treatment and reuse in this area. These results contribute to a better understanding of water consumption habits in rural areas affected by water scarcity and the potential of implementing greywater treatment systems to generate a decrease in demand for drinking water.