Vegetation Cover In Region Research Articles

Quantified moorland vegetation and assessment of the role of burning over the past five millennia

AbstractAimsTo apply the Landscape Reconstruction Algorithm (LRA) to pollen count data from multiple sites to estimate local vegetation abundance and compare with charcoal‐derived records of burning.LocationExmoor, southwest England, UK.MethodsPollen count data from 16 sites were transformed to estimates of distance‐weighted vegetation abundance using the LRA (REVEALS and LOVE models), correcting for bias in pollen production and dispersal. Charcoal concentration data from six sites were normalized using Box‐Cox transformation to produce z‐scores. Moving‐window correlation was undertaken to compare pollen percentage values for key taxa (Calluna, Poaceae) and localized burning. Estimates of distance‐vegetation abundance (LRA output) and time‐averaged charcoal z‐scores were compared to assess the role of burning as a driver for upland vegetation cover.ResultsComparison of pollen percentage and normalized charcoal z‐scores show little correlation between vegetation cover and burning. Estimates of distance‐weighted vegetation abundance and normalized charcoal data show relationships between vegetation change and burning at four of the six sites. The relationships are site‐specific: three sites suggest burning promoted grass‐dominated vegetation, at one site burning promoted heather‐dominated vegetation, and in two sites there is no apparent relationship.ConclusionsThe patterning of vegetation within uplands is a crucial part of ecosystem service delivery, and contemporary and future management benefits from understanding of ‘long‐term’ development, i.e. patterns over millennia. The correction of biases within pollen production and dispersal to produce local vegetation estimates has demonstrated spatial heterogeneity in vegetation cover on Exmoor that is not otherwise evident in the pollen percentage data (which retain a strong influence of the regional vegetation cover). The relationship between LRA‐derived vegetation cover and burning is not apparent in comparisons between pollen percentage data and charcoal records. This implies that studies that use pollen proportional data alone can misrepresent the relationship between vegetation cover and fire. This study demonstrates that fire has been an important part of the development of this cultural landscape.

A Two-Year Study on Mercury Fluxes from the Soil under Different Vegetation Cover in a Subtropical Region, South China

In order to reveal the mercury (Hg) emission and exchange characteristics at the soil–air interface under different vegetation cover types, the evergreen broad-leaf forest, shrub forest, grass, and bare lands of Simian Mountain National Nature Reserve were selected as the sampling sites. The gaseous elementary mercury (GEM) fluxes at the soil–air interface under the four vegetation covers were continuously monitored for two years, and the effect of temperature and solar radiation on GEM fluxes were also investigated. Results showed that the GEM fluxes at the soil–air interface under different vegetation cover types had significant difference (p < 0.05). The bare land had the maximum GEM flux (15.32 ± 10.44 ng·m−2·h−1), followed by grass land (14.73 ± 18.84 ng·m−2·h−1), and shrub forest (12.83 ± 10.22 ng·m−2·h−1), and the evergreen broad-leaf forest had the lowest value (11.23 ± 11.13 ng·m−2·h−1). The GEM fluxes at the soil–air interface under different vegetation cover types showed similar regularity in seasonal variation, which mean that the GEM fluxes in summer were higher than that in winter. In addition, the GEM fluxes at the soil–air interface under the four vegetation covers in Mt. Simian had obvious diurnal variations.

Vegetation cover-another dominant factor in determining global water resources in forested regions.

Forested catchments provide critically important water resources. Due to dramatic global forest change over the past decades, the importance of including forest or vegetation change in the assessment of water resources under climate change has been highly recognized by Intergovernmental Panelon Climate Change (IPCC); however, this importance has not yet been examined quantitatively across the globe. Here, we used four remote sensing-based indices to represent changes in vegetation cover in forest-dominated regions, and then applied them to widely used models: the Fuh model and the Choudhury-Yang model to assess relative contributions of vegetation and climate change to annual runoff variations from 2000 to 2011 in forested landscape (forest coverage >30%) across the globe. Our simulations show that the global average variation in annual runoff due to change in vegetation cover is 30.7%±22.5% with the rest attributed to climate change. Large annual runoff variation in response to vegetation change is found in tropical and boreal forests due to greater forest losses. Our simulations also demonstrate both offsetting and additive effects of vegetation cover and climate in determining water resource change. We conclude that vegetation cover change must be included in any global models for assessing global water resource change under climate change in forest-dominant areas.

Impact of geographical factors on coastal tourism between İğneada and Kastro Bay, Thracian Black Sea coast, Turkey

This study discusses the relationship between tourism and geomorphologic features, climatic comfort and natural vegetation cover in the coastal region from İğneada to Kastro Bay on the Black Sea. From the point of view of climatic comfort, Thermo-Hygrometric Index (THI) values indicate that May, June, September and October are favorable for coastal tourism while in the months of July and August temperatures are too hot. SSI index values indicate that comfort levels prevail for most people in June and September although the weather can be perceived by some people as cool. In July and August, when the temperatures are higher, the climate is comfortable part of the time, but it is rather hot and sticky. Despite climatic comfort conditions not being suitable for long-duration coastal tourism in the Kıyıköy-İğneada area, the floristic richness of the area and presence of longose forests offer many opportunities in terms of ecotourism. There are also numerous lakes and streams presenting unique possibilities for a variety of so-far unexploited tourism activities. Geomorphologically, uncontaminated sandy beaches and coastal spits as well as sheltered bays such as Kastro Bay are among the important assets of the area in terms of coastal tourism.

A Conversion Method to Determine the Regional Vegetation Cover Factor from Standard Plots Based on Large Sample Theory and TM Images: A Case Study in the Eastern Farming-Pasture Ecotone of Northern China

The key to simulating soil erosion is to calculate the vegetation cover (C) factor. Methods that apply remote sensing to calculate the C factor at a regional scale cannot directly use the C factor formula. That is because the C factor formula is obtained by experiments, and needs the coverage ratio data of croplands, woodlands, and grasslands at a standard plot scale. In this paper, we present a C factor conversion method from a standard plot to a km-sized grid based on large sample theory and multi-scale remote sensing. The results show that: (1) Compared with the existing C factor formula, our method is based on the coverage ratio of croplands, woodlands, and grasslands on a km-sized grid, and takes the C factor formula obtained from the standard plot experiment and applies it to a regional scale. This method improves the applicability of the C factor formula, and can satisfy the need to simulate soil erosion in large areas; (2) The vegetation coverage obtained by remote sensing interpretation is significantly consistent (paired samples t-test, t = −0.03, df = 0.12, 2-tail significance p < 0.05) and significantly correlated with the measured vegetation coverage; (3) The C factor of the study area is smaller in the middle, southern, and northern regions, and larger in the eastern and western regions. The main reason for that is the distribution of woodlands, the Hunshandake and Horqin sandy lands, and the valleys affected by human activities; (4) The method presented in this paper is more meticulous than the C factor method based on the vegetation index, improves the applicability of the C factor formula, and can be used to simulate soil erosion on a large scale and provide strong support for regional soil and water conservation planning.

Modelling impacts of agricultural practice on flood peaks in upland catchments: An application of the distributed TOPMODEL

AbstractUpland agricultural land management activities such as grazing, vegetation burning, and bare ground restoration impact hydrological elements of headwater catchments, many of which may be important for downstream flood peaks (e.g., overland flow and soil water storage). However, there is poor understanding of how these management practices affect river flow peaks during high magnitude rainfall events. Using the distributed TOPMODEL, spatial configurations of land management were modelled to predict flood response in an upland catchment, which contains different regions operating subsidized agricultural stewardship schemes. Heavy grazing leading to soil compaction and loss of vegetation cover in stewardship regions covering 79.8% of the catchment gave a 42‐min earlier flow peak, which was 82.2% higher (under a 1‐hr 15‐mm storm) than the current simulated hydrograph. Light grazing over the same regions of the catchment had much less influence on river flow peaks (18 min earlier and 32.9% increase). Rotational burning (covering 8.8% of the catchment), most of which is located in the headwater areas, increased the peak by 3.2% in the same rainfall event. Vegetation restoration with either Eriophorum or Sphagnum (higher density) in bare areas (5.8%) of the catchment provided a reduction of flood peak (3.9% and 5.2% in the 15‐mm storm event), whereas the same total area revegetated with Sphagnum in riparian regions delivered a much larger decrease (15.0%) in river flow peaks. We show that changes of vegetation cover in highly sensitive areas (e.g., near‐stream zones) generate large impacts on flood peaks. Thus, it is possible to design spatially distributed management systems for upland catchments, which reduce flood peaks while at the same time ensuring economic viability for upland farmers.

Vegetation interpretation and classification from high resolution true colour map images of shanghai city

Vegetation interpretation and classification is the core work of regional ecological monitoring and carbon sinks calculating. Different from traditional remote sensing data, the development of high resolution true colour map provides a new possibility of vegetation interpretation and classification, especially for scattered, small-scale vegetation distributions in city regions. In Hue, Saturation and Value (HSV) colour space, colour model and texture model are combined to extract vegetation features, adjusting weights of the two features as a whole to achieve a better identification effect. Based on the nearest neighbour method, the model matches the features of candidate images with typical training vegetation samples. The main researches and innovations are as fol- lows: (i) The research uses high resolution true colour map images to provide real-time and more convenient data, making the study less limited to low spatial resolution of sensing images. (ii) It explores vegetation cover in city regions in an effective way, which is dispersed in size, variable in type and difficult to be located pre- cisely. (iii) The results of simulation show that this method is feasible and the feature-weighted model im- proves the precision to 83.3 % around by adjusting weight parameters, much better than single feature model. (iv) Combined with the annual Net primary productivity (NPP) values in different vegetation types, the carbon storage of carbon sinks in one area of 23,373 m2 is calculated, ranging from 9,000 - 12,000 kg, providing a new way to track the carbon footprints in city regions.

Strong Gradients in Forest Sensitivity to Climate Change Revealed by Dynamics of Forest Fire Cycles in the Post Little Ice Age Era

AbstractThe length of the fire cycle is a critical factor affecting the vegetation cover in boreal and temperate regions. However, its responses to climate change remain poorly understood. We reanalyzed data from earlier studies of forest age structures at the landscape level, in order to map the evolution of regional fire cycles across Eastern North American boreal and temperate forests, following the termination of the Little Ice Age (LIA). We demonstrated a well‐defined spatial pattern of post‐LIA changes in the length of fire cycles toward lower fire activity during the 1800s and 1900s. The western section of Eastern North America (west of 77°W) experienced a decline in fire activity as early as the first half of the 1800s. By contrast, the eastern section showed these declines as late as the early 1900s. During a regionally fire‐prone period of the 1910s–1920s, forests in the western section of Eastern boreal North America burned more than forests in the eastern section. The climate appeared to dominate over vegetation composition and human impacts in shaping the geographical pattern of the post‐LIA change in fire activity. Changes in the atmospheric circulation patterns following the termination of the LIA, specifically changes in Arctic Oscillation and the strengthening of the Continental Polar Trough, were likely drivers of the regional fire dynamics.

Apport De La Teledetection Pour Le Suivi SpatioTemporel De L’occupation Du Sol Dans La Region Montagneuse Du Tonkpi (Cote D’ivoire)

Objective: This study aims to characterize and to map vegetation cover in the mountainous region of Tonkpi in order to evaluate forest dynamics by remote sensing. Methodology and Results: This work relied on four satellite images of the scene 198-55 Landsat 4 TM 1990 from Landsat 7 ETM+ in 2000, Landsat 5 TM 2011 and Landsat 8 OLI-SHOTS 2015. Based on field data, classification was conducted using the maximum likelihood method in satellite images (OLI-SHOTS, ETM + and TM) in order to map vegetation from 1990 to 2015. These maps were superimposed to the Digital elevation model produced from an ASTER image in order to assess forest dynamics at altitude levels. The diachronic study of land use revealed a change in the landscape with a significant reduction of dense forest (-35.6%) and crop lands and fallow (-42.14%), and an increase of degraded forests (15.13%) and bare soil land and houses (10.46%). Moreover, high altitudes occupy a large proportion (37.7%) of the landscape (12,284 km2 ), followed by medium altitudes (34.6%), and low altitudes (27.7%). Concerning bare soil and homes, there is a large increase of the area at low altitudes (88, 96%) while concerning crops and fallow, the area reduction was more pronounced at high altitudes ( -53.64%). The medium altitudes have the highest rate of increase (51.14%) in degraded forests, and the highest decrease (-43.25%) in the dense forests. Conclusion and Application: The study shows that high altitudes occupy the largest proportion of the total area of the region and a change in the landscape due to human activities. Based on the results, we recommend a spatio-temporal monitoring of the net erosion on the mountains in order to maintain its agricultural potential and fight effectively against erosion.

The influence of the spatial heterogeneity of vegetation cover and surface topography on vertical CO2 fluxes within the atmospheric surface layer

The influence of the spatial heterogeneity of vegetation cover and topography on CO2 fluxes in the atmospheric surface layer is estimated using a two-dimensional (2D) hydrodynamic model of turbulent exchange. A ~4.5-km-long profile that crossed a hilly area with a mosaic vegetation cover in Tula region was selected for model experiments. During the first experiment, a wind field and vertical fluxes were calculated by the 2D model for the entire selected profile with respect to the horizontal heterogeneity of the vegetation cover and surface topography. In the second experiment, the profile was considered an assemblage of elementary independent homogeneous segments; for each of them, vertical fluxes were calculated by the 2D model with the assumption of ‘zero’ horizontal advection, i.e., the required functions are independent of the horizontal coordinates. The influences of any boundary effects that appear at the interface between the different vegetation communities and at topographical irregularities on the turbulent regime are ignored in this case. For the profile selected, ignoring the horizontal advection, disturbances in the wind field that appeared at surface topography irregularities, and boundaries between different vegetation communities can lead to a 26% underestimation of the total CО2 absorption by the ground surface on a clear sunny day under summer weather conditions.

Analysis of the Effects of Drought on Vegetation Cover in a Mediterranean Region through the Use of SPOT-VGT and TERRA-MODIS Long Time Series

The analysis of vegetation dynamics and agricultural production is essential in semi-arid regions, in particular as a consequence of the frequent occurrence of periods of drought. In this paper, a multi-temporal series of the Normalized Difference of Vegetation Index (NDVI), derived from SPOT-VEGETATION (between September 1998 and August 2013) and TERRA-MODIS satellite data (between September 2000 and August 2013), was used to analyze the vegetation dynamics over the central region of Tunisia in North Africa, which is characterized by a semi-arid climate. Products derived from these two satellite sensors are generally found to be coherent. Our analysis of land use and NDVI anomalies, based on the Vegetation Anomaly Index (VAI), reveals a strong level of agreement between estimations made with the two satellites, but also some discrepancies related to the spatial resolution of these two products. The vegetation’s behavior is also analyzed during years affected by drought through the use of the Windowed Fourier Transform (WFT). Discussions of the dynamics of annual agricultural areas show that there is a combined effect between climate and farmers’ behavior, leading to an increase in the prevalence of bare soils during dry years.

Developing MODIS-based cloud climatologies to aid species distribution modeling and conservation activities

Author(s): Douglas, Michael William; Beida, Rahama; Mejia, John F.; Fuentes, Marcia Vetromilla | Abstract: WorldClim (Hijmans et al. 2005) has been the de-facto source of basic climatological analyses for most species distribution modeling research and conservation science applications because of its global coverage and fine (l1 km) spatial resolution. However, it has been recognized since its development that there are limitations in data-poor regions, especially with regard to the precipitation analyses. Here we describe procedures to develop a satellite-based daytime cloudiness climatology that better reflects the variations in vegetation cover in many regions of the globe than do the WorldClim precipitation products. Moderate Resolution Imaging Spectroradiometer (MODIS) imagery from the National Aeronautics and Space Administration (NASA) Terra and Aqua sun-synchronous satellites have recently been used to develop multi-year climatologies of cloudiness. Several procedures exist for developing such climatologies. We first discuss a simple procedure that uses brightness thresholds to identify clouds. We compare these results with those from a more complex procedure: the MODIS Cloud Mask product, recently averaged into climatological products by Wilson and Jetz (2016). We discuss advantages and limitations of both approaches. We also speculate on further work that will be needed to improve the usefulness of these MODIS-based climatologies of cloudiness. Despite limitations of current MODIS-based climatology products, they have the potential to greatly improve our understanding of the distribution of biota across the globe. We show examples from oceanic islands and arid coastlines in the subtropics and tropics where the MODIS products should be of special value in predicting the observed vegetation cover. Some important applications of reliable climatologies based on MODIS imagery products will include 1) helping to restore long-degraded cloud-impacted environments; 2) improving estimations of the spatial distribution of cloud-impacted species; and 3) helping to identify areas for rapid biological assessments. The last application can even benefit from qualitative perusal of the current MODIS climatologies.

Modern pollen–vegetation relationships in saltmarsh habitats along a salinity gradient of a fluvial estuary

The classification of vegetated habitats and the palynological study of surface sediments are used to evaluate the plant-pollen relationship in the saltmarshes of the Chuí River (southern Brazil). The visual plant cover was recorded in five transects perpendicular to the river's margins and positioned along 4.5km of the estuarine gradient. Two-way Indicator Species Analysis (TWINSPAN) of the plant cover in 65 sampled quadrats was used to characterize five vegetated habitats. These habitats were distinguished by their elevation in the intertidal zone and their location in the estuarine gradient. The salinity of surface water that flooded low marshes decreased from 20 to 4 between transect 1 and transect 5. A total of 10 surface soil samples from marsh habitats were taken in the same transects as for the study of vegetation, and pollen and spores were identified. The pollen frequencies of dominant families (Cyperaceae, Poaceae, Chenopodicaeae, Juncaceae and Asteraceae) on the surface of marsh habitats show high correlations with the parent plant cover (0.66 to 0.81), but pollen taxa show a higher richness in the plant taxa. The most frequent spores (massulae) encountered in all samples belong to the aquatic fern Azolla filiculoides, followed by spores of the moss Phaeoceros. The palynological data obtained are consistent with the regional vegetation cover characteristics of saltmarshes, but it is difficult to distinguish different habitat types (Discriminant Analysis results). This low discrimination of pollen-spore assemblages is related to the widespread distribution of the indicator plant species, mostly taxa known to produce large quantities of (primarily) wind-dispersed pollen, which are also redeposited or transferred by tides or freshwater influxes. The low taxonomic resolution of pollen grains of dominant taxa, such as Cyperaceae and Poaceae, also creates difficulties to distinguish the vegetated marsh habitats based on pollen assemblages. The widespread presence of pollen from introduced plants such as Pinus species near the saltmarshes emphasizes the anthropogenic impact on this region.

Changes in vegetation cover and composition in the Swedish mountain region.

Climate change, higher levels of natural resource demands, and changing land use will likely lead to changes in vegetation configuration in the mountain regions. The aim of this study was to determine if the vegetation cover and composition have changed in the Swedish region of the Scandinavian Mountain Range, based on data from the long-term landscape biodiversity monitoring program NILS (National Inventory of Landscapes in Sweden). Habitat type and vegetation cover were assessed in 1740 systematically distributed permanent field plots grouped into 145 sample units across the mountain range. Horvitz-Thompson estimations were used to estimate the present areal extension of the alpine and the mountain birch forest areas of the mountain range, the cover of trees, shrubs, and plants, and the composition of the bottom layer vegetation. We employed the data from two subsequent 5-year monitoring periods, 2003-2007 and 2008-2012, to determine if there have been any changes in these characteristics. We found that the extension of the alpine and the mountain birch forest areas has not changed between the inventory phases. However, the total tree canopy cover increased in the alpine area, the cover of graminoids and dwarf shrubs and the total cover of field vegetation increased in both the alpine area and the mountain birch forest, the bryophytes decreased in the alpine area, and the foliose lichens decreased in the mountain birch forest. The observed changes in vegetation cover and composition, as assessed by systematic data in a national and regional monitoring scheme, can validate the results of local studies, experimental studies, and models. Through benchmark assessments, monitoring data also contributes to governmental policies and land-management strategies as well as to directed cause and effect analyses.

Distribution changes of woody plants in Western Iran as monitored by remote sensing and geographical information system: a case study of Zagros forest

The status of woody plants in dry-land systems is a fundamental determinant of key ecosystem processes. Monitoring of this status plays an important role in understanding the dynamics of woody plants in arid and semi-arid ecosystems. The present study determined the dynamism of the Zagros forests in Iran using Remote Sensing and Geographic Information System techniques and statistical science. The results show that the density of trees varied from 10 to 53 % according to the physiographic and climatic conditions of semi-arid regions. The best and lowest correlation between vegetation indices and forest density were obtained for the global environmental monitoring index (GEMI; R 2 = 0.94) and soil adjust vegetation index (R 2 = 0.81), respectively. GEMI is used to monitor land use changes over a 10-year period. Results show that 2720 ha2 of forest have been destroyed by human interference and tillage on steep slopes during this period which also resulted in the loss of the fertile soil layer. GEMI determined the areas with a biomass of trees and could normally separate border regions with low biomass density of trees from regions without canopy cover. The results revealed that assessment of forest and vegetation cover in arid and semi-arid arduous forest regions using satellite digital numbers and ordinary sampling is subject to uncertainty. A stratified grouping procedure should be established to increase the accuracy of assessment.

Spatial Analysis of Land Surface - Vegetation Relationship in Mountainous Areas of the Tropics Using Srtm-3 Dem

Digital elevation models (DEMs) have shown much potential for use in the extraction of land surface parameters and analysis of the relationship between land surface units and vegetation cover. However, there is lack of studies on the use of SRTM-3 DEM in vegetation studies of mountainous regions. This study is therefore an attempt to relate land surface parameters to vegetation cover in the Obudu mountain region using SRTM-3 DEM and Landsat data. Geomorphometric classification of the land surface was done using an unsupervised ISOCLUST algorithm while vegetation cover classification was done using the supervised approach based on the Maximum Likelihood algorithm. The resultant land surface units and vegetation cover maps were then related using grid-based statistic within the geographic information systems. The overall measure of difference between the two maps yielded a chi-square (d.f. = 24) = 1.9154, p > 0.05. This implies that there is no significant difference between the land surface units and the vegetation cover in the study area. This findings support the use of SRTM-3 for land surface and vegetation mapping where there is no higher quality data, or the cost of obtaining one is inhibitive; a situation that is faced by many developing economies like Nigeria. However, this results should be interpreted and used within the context of the uncertainty that is contained in the SRTM-3 DEM.

Arctic browning: extreme events and trends reversing arctic greening.

Arctic browning: extreme events and trends reversing arctic greening.

An Application of WEAP Model in Water Resources Management Considering the Environmental Scenarios and Economic Assessment Case Study: Hirmand Catchment

Hirmand catchment is one of the important trans boundary catchment in Iran. Sistan people living in south east Iran related to this catchment. Meanwhile drought of the last two decades, due to dust storms jeopardized the Human health. Also, causing destroyed vegetation cover and animal habitat in region. The first objective of the present study is water resources management under environmental scenarios using the WEAP model in Hirmand catchment. In study, dust stabilization and animal-plant sustainable ecosystem scenarios have been applied. The second objective is economic assessment of defined scenarios. According to the results, average total demand in dust stabilization and animal-plant sustainable ecosystem scenarios increased about 238 and 231 million cubic meters compared to the current account, respectively. Also, unmet demand compared to the current account increased 193 and 200 million cubic meters, approximately. According to the economic assessment calculations, benefit in dust stabilization scenario 160 milliards rials and in animal-plant sustainable ecosystem scenario 209 milliards rials decreased in agriculture sector. Therefore, despite the decline in benefit, in policy making and water resources management should be special attention to protect the environment wetlands.

Indirect and direct effects of soil properties on soil splash erosion rate in calcareous soils of the central Zagross, Iran: A laboratory study

Detachment of soil particles by means of raindrop impact is mainly affected by soil properties especially in the absence of vegetation cover. This study was conducted to investigate the direct and indirect effects of soil properties on splash erosion rate in calcareous soils of low vegetation cover in Lordegan region, Iran. For this purpose, Total Soil Splash (TSE), downslope (DSE) and upslope (USE) Splash erosion rate are measured under the following four conditions that comprised different values of Slope (S:%) and Rainfall Intensity (RI:mmh−1): 5–50, 5–80, 15–50, 15–80, respectively, using Multiple Splash Sets (MSS). As potential estimating parameters, Surface Shear Strength (SSS), Mean Weight Diameter (MWD), Organic Matter (OM), calcium carbonate, clay content, silt and sand fractions were estimated. The effects of soil estimators on soil splash erosion rate were quantified using a path analysis and Multi-Linear Regression (MLR) approaches applied to data collected from 105 points of soil profiles (A horizon). The results showed that the particle size distribution, SSS and MWD are sensitive to some of the parameters for estimating TSE, DSE and USE rate. MWD carried the highest direct effects while SSS the highest indirect ones (via MWD) on splash erosion. Particle size effects on soil splash weren't in general observed in higher slopes and rainfall intensities. The Particle size has in general a more direct rather than an indirect effect on splash erosion. Fine silt exerted an ambivalent role on splash erosion: A high detachability of fine silt directly increases splash erosion while its capability to form a surface crust, reduces splash erosion. Indirect effect of OM through its association with MWD and SSS is more than it's direct effects. Positive direct effect of calcium carbonate is more than its indirect negative effect via its association with MWD, probably due to the presence of calcium carbonate within the size of silt and fine sand in the studied soils, causing an increase in soil detachability.

Estimating ground fractional vegetation cover using the double-exposure method

Fractional vegetation cover (FVC) is a key parameter in ecological models. It is important to determine the ground FVC quickly and accurately in studies of soil erosion, surface energy balance, and carbon cycling. As one of the FVC ground measurement methods, the photographic method is easy to operate with relatively high precision. However, its classification result showed poor accuracy when an image of a high-contrast scene contained a shadow region where a low signal-to-noise ratio (SNR) existed, because the single-exposure image in the photographic method did not contain sufficient surface information about both the illuminated and shadowed parts. This article presents application of a double-exposure photographic method to determine vegetation cover in the shadow region of an image. It consists of two measurements used in acquiring images (normal and over-exposure) and one image-processing part to handle the obtained images. Illuminated vegetation and soil, as well as the shadow region, was classified with the normally exposed image in the intensity, hue, and saturation (IHS) colour space, and the shadow region was further classified as shadowed vegetation and shadowed soil using the over-exposed image. The results indicate that the over-exposed image reduced the average bias of the FVC in the shadow region from 15.40% to −4.14% and the root mean square error (RMSE) from 0.174 to 0.066. The RMSE of the entire scene was 0.055 in the over-exposed image and 0.092 in the single-exposed image. The double-exposure method also showed a better classification result than the high dynamic range method in deep shadow regions. This study shows that this method is capable of distinguishing vegetation and soil in the shadow region and thus it is an effective and accurate method for ground FVC measurement.