Search results for "forest"
showing 10 items of 3780 documents
Variable scale effects on hillslope soil erosion during rainfall-runoff processes
2021
Abstract The variation of soil erosion across scales remains a controversial issue. A theoretical framework, coupling the normalized Green-Ampt equation for infiltration, 1D kinematic wave model for overland flow, and WEPP erosion modeling approaches for soil erosion, was used to explain and quantify the direct effect of scale on the soil erosion process. The results show that the relation between interrill erosion and slope length accords with a power-law decreasing trend, while the relation of rill erosion versus slope length shows a power-law increasing trend. Moreover, the power-law scaling of interrill erosion becomes more prominent with an increase of rainfall duration and intensity b…
A pedotransfer function for estimating the soil erodibility factor in Sicily
2009
The soil erodibility factor, K, of the Universal Soil Loss Equation (USLE) is a simple descriptor of the soil susceptibility to rill and interrill erosion. The original procedure for determining K needs a knowledge of soil particle size distribution (PSD), soil organic matter, OM, content, and soil structure and permeability characteristics. However, OM data are often missing and soil structure and permeability are not easily evaluated in regional analyses. The objective of this investigation was to develop a pedotransfer function (PTF) for estimating the K factor of the USLE in Sicily (south Italy) using only soil textural data. The nomograph soil erodibility factor and its associated firs…
Experiments for testing soil texture effects on flow resistance in mobile bed rills
2018
Abstract In this paper a recently theoretically deduced rill flow resistance equation, based on a power-velocity profile, was tested experimentally on plots of varying slopes and soil texture in which mobile bed rills are incised. Measurements of flow velocity, water depth, cross section area, wetted perimeter and bed slope conducted in rill reaches incised on experimental plots, having different slope values (9, 14, 22, 24 and 26%) and soil texture (clay fraction ranging from 42 to 73%), and literature data were used to calibrate the flow resistance equation. In particular, the relationship between the velocity profile parameter Γ, the channel slope, the flow Froude number and texture frac…
Exotic Guavas are Foci of Forest Regeneration in Kenyan Farmland
2007
Fruiting trees in degraded areas are attractive for frugivorous birds and may become centers of regeneration. However, a number of tree species in degraded areas are exotic species. Thus, the question arises whether these exotic species can also act as foci for forest regeneration. In the farmland adjacent to Kakamega Forest, Kenya, we investigated the frugivore assemblage in, and seed rain and seedling establishment under, 29 fruiting exotic guava trees (Psidium guajava) at different distances to the forest. The results show that 40 frugivorous bird species visited guava trees. All of the seed and 82 percent of the seedling species found under the treecrowns were animal dispersed, 58 and 5…
A full‐scale study of Darcy‐Weisbach friction factor for channels vegetated by riparian species
2021
In this article, an open channel flow resistance equation, deduced applying dimensional analysis and incomplete self-similarity condition for the flow velocity distribution, was tested using measurements carried out in a full-scale channel equipped with three types of riparian plants (Salix alba L., Salix caprea L. and Alnus glutinosa L.). In the experimental channel, having banks lined with boulders, the vegetation branches were anchored in a concrete bottom. For each species, the measurements were carried out with plants having different amounts of leaves, different plant density and plant area index. The relationship between the scale factor Γ of the velocity profile and the Froude numbe…
An automatic approach for rill network extraction to measure rill erosion by terrestrial and low‐cost unmanned aerial vehicle photogrammetry
2019
For an erosion event (October 2016) occurred at the Sparacia experimental area (Southern Italy), both terrestrial and low-altitude aerial surveys were carried out by consumer grade camera and quadcopter (low-cost unmanned aerial vehicle [UAV]) to measure rill erosion on two plots with steepness of 22% and 26%. Applying the structure from motion (SfM) technique, the three-dimensional digital terrain models (3D-DTMs) and the quasi three-dimensional models (2.5D-digital elevation model [DEM]) were obtained by the two surveys. Furthermore, 3D-DTM and DEM were built using the available aerial photographs (166) and adding 40 terrestrial photographs. For the first time, the convergence index was a…
Comparing Physical Quality of Forest and Pasture Soils in a Sicilian Watershed
2011
Forest and pasture soils should have differing properties due, for example, to differing root characteristics or livestock trampling rates, but contradictory results are reported in the literature. The surface soil physical and hydraulic properties of five forest and pasture sites were determined in a Sicilian watershed. In general, forest soils had a significantly lower bulk density, b (by 17 to 35%), and a higher field saturated hydraulic conductivity, Kfs (by a factor of 3.4-11.5) than pasture soils. Differences between water retention characteristics of forest and pasture soils were low when high levels of organic matter, OM, content (> 7.1%) were detected for both land uses. The mean …
Trophic cascades in benthic marine ecosystems: lessons for fisheries and protected-area management
2000
An important principle of environmental science is that changes in single components of systems are likely to have consequences elsewhere in the same systems. In the sea, food web data are one of the few foundations for predicting such indirect effects, whether of fishery exploitation or following recovery in marine protected areas (MPAs). We review the available literature on one type of indirect interaction in benthic marine ecosystems, namely trophic cascades, which involve three or more trophic levels connected by predation. Because many indirect effects have been revealed through fishery exploitation, in some cases we include humans as trophic levels. Our purpose is to establish how wi…
Large-scale drainage and breeding success in boreal forest grouse
2007
Summary 1 The breeding success of Finnish grouse has been in decline for decades. While it has been shown that fragmentation and modern forestry practices such as clear-cutting affect the viability of grouse populations, little is known about effects of large-scale drainage. The drainage network in Finland has increased dramatically during the past decades. By 1988, 6 million ha of bog ecosystems had been drained. This is likely to have had a profound direct and indirect effects on grouse productivity. Because ditches persist in time, large-scale drainage may therefore have strong potential for affecting the long-term breeding success of three forest grouse species in Finland. 2 Using a mix…
Comparison of social-ecological resilience between two grassland management patterns driven by grassland land contract policy in the Maqu, Qinghai-Ti…
2018
Embraced for decision-making, resilience has evolved as a meaningful term in areas such as ecology, the economy and society. After a policy of grassland contracts was implemented on the Qinghai-Tibetan Plateau, two grassland management patterns evolved: the multi-household management pattern (MMP) and the single-household management pattern (SMP). Within a resilience-driven perspective, this study compared the outcomes of these grassland management patterns by measuring their effects on the resilience of grazing, ecological, economic and social systems. Resilience indicators for each of the four systems were: grazing system (grazing space, transhumance, water source and reproduction); ecolo…