Search Results (7)

The tropical dry regions in the Neotropics are under intense anthropogenic pressures, resulting in changes for local communities related with their life patterns, wellbeing, and their relationship with ecosystems. The region has a history of human occupation that has shaped the traditional use of resources. We evaluated the richness, redundancy, and divergence of traditional uses of tree species present in vegetation patches of the tropical dry region of the Gulf of Mexico using functional diversity indices. The most used species are Acacia cochliacantha, Cedrela odorata, Enterolobium cyclocarpum, Gliricidia sepium, and Guazuma ulmifolia, and the uses with the broadest distributions across the region are firewood and pasture management, while reforestation is the least common use. While distance to the nearest patch of the closest human settlement is the most predictive variable associated with inhabitants’ different uses or recognitions of the value of different plant species, the most recognized and valued species are widely distributed in Mexico. Even when the forest cover is greatly reduced, the inhabitants recognize numerous uses that can be obtained from the vegetation patches. The approach used in this work provides important baseline information, as well as a methodology that facilitates the identification of priority areas for conservation. Full article

Greece, like the rest of the Mediterranean countries, faces wildland fires every year. Besides their short-term socioeconomic impacts, ecological destruction, and loss of human lives, forest fires also increase the burnt areas’ risk of flash flood phenomena, as the vegetation, which acted in a protective way against runoff and soil erosion, is massively removed. Among the most severe wildland fire events in Greece were those of summer 2021, which were synchronous to the very severe heat waves that hit the broader area of the Balkan Peninsula. More than 3600 km² of land was burnt and a significant amount of natural vegetation removed. Three of the burnt areas are examined in this work, namely, Attica, Northern Euboea, and the Peloponnese, in order to assess their risk of future flash flood events. The burnt areas were mapped, and their geological and geomorphological features studied. Flash flood hazard assessment was accomplished through a Boolean logic-based model applied through Geographic Information Systems (GIS) software, which allowed the prioritization of the requirement for protection by identifying which locations were most prone to flooding. The largest part of our study areas is characterized by geomorphological and geological conditions that facilitate flash flood events. According to our findings, in almost all study areas, the regions downstream of the burnt areas present high to very high flash flood hazard, due to their geomorphological and geological features (slope, drainage density, and hydrolithology). The only areas that were found to be less prone to flood events were Vilia and Varimpompi (Attica), due to their gentler slope inclinations and overall geomorphological characteristics. It is known that vegetation cover acts protectively against flash floods. However, in this case, large areas were severely burnt and vegetation is absent, resulting in the appearance of flash floods. Moreover, imminent flooding events are expected to be even more intense in the areas downstream of the burnt regions, possibly bearing even worse impacts on the local population, infrastructure, etc. Full article

Coastal dunes are valuable and vulnerable habitats that require scientific exploration and understanding of their natural processes; therefore, the aims of this study were to determine the current vegetation characteristics of dune habitats along the Bulgarian Coast in terms of species richness and cover of typical psammophytes and different non-psammophytic plant groups, and to analyze how they respond to certain environmental drivers. Data were collected from 12 dune systems. The research was focused on embryonic, white and grey dunes. The field work was conducted throughout July and August 2017. The vegetation was sampled at 154 phytosociological plots (5 m × 5 m). To understand how the vegetation responds to different drivers, we tested the correlation of defined species group richness and cover in relation to (1) the soil pH and EC values, (2) the distance from inland to the sea and (3) the range of different categories of land cover in the surrounding area. In order to track temporal vegetation changes, we compared the cover of defined species groups between 2003 and 2017. We registered a total number of 269 vascular plants, 12 bryophytes and 5 lichens. The strongest presence in all dune types, both in species richness and cover, was the group of grass- and shrubland plants. Weeds and ruderal plants had significant coverage in grey dunes, while the richness and cover of forest and alien plants were negligible among the studied dune habitats. The comparison of data between 2003 and 2017 revealed a substantial decline in the cover of psammophytes. We observed a clear pattern regarding the share of species richness of psammophytes and non-psammophytes among different locations. We detected that grey dunes were the most affected by the penetration of non-psammophytes. Full article

Conversion of rangelands into cultivated land is one of the main challenges affecting the management of rangelands in Ethiopia. In order to inform policy makers about trends in land-use conversion, this study examined the drivers, trends, and impacts of land conversions in five locations selected in the Borana rangelands of Southern Ethiopia. This study integrated survey interviews from agro-pastoralists, participatory appraisals, rainfall data, and remotely sensed satellite data from Landsat images taken in 1985 and 2011. Results indicate that there is a marked increase in cultivated land in some of the study sites while in the other sites there is a slight reduction. The bare lands increased in some parts of the study sites though there was slight recovery of grassland in some of the degraded areas. Settlement areas with permanent housing increased. Woodland vegetation decreased except on mountain escarpments where there were slight gains. The results further show that, during this period, bushland decreased while at the same time grassland increased. Shrub/grassland with seasonally flooded areas increased in the bottomlands. Inhabitants interviewed in the study areas perceived land use and land cover changes to be driven by interplay of recurrent drought, loss of pasture, food insecurity, and decline in income. Changes in policies that govern natural resources have influence the land use change in this area and the expansion of cultivation. Expansion of cultivation practices upon rangelands has resulting in significant loss of vegetation biomass and soil erosion, thereby precipitating rangeland degradation. The results provide comprehensive insights regarding the influence of internal and external drivers of land conversion that should be considered when making decisions for land use planning. Full article

Tomato (Solanum lycopersicum L.) is an important vegetable for supplying vitamins, minerals and fiber in human diets worldwide. Successful open field production of tomato in the tropics is limited by insect pests among other constraints. Two trials were conducted at the Horticulture Research and Teaching Field, Egerton University, Kenya with the objective of evaluating the effects of agricultural nets (agronets) herein called eco-friendly nets (EFNs) and floating row covers (FRCs) on pest population and yield of tomatoes. A randomized complete block design with five replications was used. Tomato plants were protected with either fine mesh EFN (0.4-mm pore diameter), large mesh EFN (0.9-mm pore diameter) or FRC. The EFN and FRC were maintained permanently closed or opened thrice a week from 9 am to 3 pm. Two control treatments were used: open unsprayed (untreated control) or open and sprayed with alpha-cypermethrin based insecticide (treated control). The use of EFN and FRC helped to manage pests with the lowest pest population obtained under FRC maintained permanently covered and the highest population recorded in the untreated control. Covering tomato plants with EFN or FRC also resulted in more marketable fruit and lower yield losses compared with the unprotected systems. The EFN and FRC offer great potential as part of integrated systems for pest management and yield improvement in tomato production in regions with a tropical climate. Full article

Most remote sensing studies in deserts focus solely on vegetation monitoring to assess the extent of desertification. However, the application of sand dune encroachment into such studies would greatly improve the accuracy in the prediction criteria of risk-prone areas. This study applies the latter methodology for tracking desertification using sand dunes in the Kelso Dunes (in Newberry-Baker, CA, USA). The approach involves the comparison of spectral characteristics of the dunes in Landsat Thematic Mapper (TM) images over a 24-year period (1982, 1988, 1994, 2000, and 2006). During this 24-year period, two El Niño events occurred (1983 and 1993); it was concluded that despite the shift in predominant winds, the short-term variation in wind direction did not make a noticeable change in dune formation, but greatly influences vegetation cover. Therefore, relying solely on vegetation monitoring to assess desertification can lead to overestimations in prediction analysis. Results from this study indicate that the Kelso Dunes are experiencing an encroachment rate of approximately 5.9 m³/m/yr over the 24-year period. While quantifying the Kelso Dunes or any natural dynamic system is subject to uncertainties, the encroachment rate approach reflects the highly heterogeneous nature of the sand dunes (in regards to spectral variability in brightness) at Kelso Dunes and serves as an exemplar for future research. Full article

Daily evapotranspiration fluxes over the semi-arid Catania Plain area (Eastern Sicily, Italy) were evaluated using remotely sensed data from Landsat Thematic Mapper TM5 images. A one-source parameterization of the surface sensible heat flux exchange using satellite surface temperature has been used. The transfer of sensible and latent heat is described by aerodynamic resistance and surface resistance. Required model inputs are brightness, temperature, fractional vegetation cover or leaf area index, albedo, crop height, roughness lengths, net radiation, air temperature, air humidity and wind speed. The aerodynamic resistance (r_ah) is formulated on the basis of the Monin-Obukhov surface layer similarity theory and the surface resistance (r_s) is evaluated from the energy balance equation. The instantaneous surface flux values were converted into evaporative fraction (EF) over the heterogeneous land surface to derive daily evapotranspiration values. Remote sensing-based assessments of crop water stress (CWSI) were also made in order to identify local irrigation requirements. Evapotranspiration data and crop coefficient values obtained from the approach were compared with: (i) data from the semi-empirical approach “K_c reflectance-based”, which integrates satellite data in the visible and NIR regions of the electromagnetic spectrum with ground-based measurements and (ii) surface energy flux measurements collected from a micrometeorological tower located in the experiment area. The expected variability associated with ET flux measurements suggests that the approach-derived surface fluxes were in acceptable agreement with the observations. Full article