Effects Of Topographic Factors Research Articles

The effect of topographic factors and land use history on grassland biodiversity in the Polish Carpathians

The effect of topographic factors and land use history on grassland biodiversity in the Polish Carpathians

Effects of Wind-Water Erosion and Topographic Factor on Soil Properties in the Loess Hilly Region of China.

Wind and water erosion processes can lead to soil degradation. Topographic factors also affect the variation of soil properties. The effect of topographic factors on soil properties in regions where wind and water erosion simultaneously occur remains complicated. To address this effect, we conducted this study to determine the relationships between the changes in wind-water erosion and soil properties in different topographic contexts. We collected soil samples from conical landforms with different slope characteristics and positions in the wind-water erosion crisscross region of China. We examined the soil 137Cs inventory, soil organic carbon (SOC), total nitrogen (TN), soil particles, soil water content (SWC), and biomass. 137Cs was applied to estimate soil erosion. The results show that the soil erosion rate followed the order of northwest slope > southwest slope > northeast slope > southeast slope. The soil erosion rate on the northwest slope was about 12.06-58.47% higher than on the other. Along the slopes, the soil erosion rate decreased from the upper to the lower regions, and was 65.65% higher at the upper slope than at the lower one. The change in soil erosion rate was closely related to soil properties. The contents of SOC, TN, clay, silt, SWC, and biomass on the northern slopes (northwest and northeast slopes) were lower than those on the southern slopes (southeast and southwest slopes), and they were lower at the upper slope than at the lower one. Redundancy analysis showed that the variation in soil properties was primarily affected by the slope aspect, and less affected by soil erosion, accounting for 56.1% and 30.9%, respectively. The results demonstrate that wind-water erosion accelerates the impact of topographic factors on soil properties under slope conditions. Our research improves our understanding of the mechanisms of soil degradation in gully regions where wind and water erosion simultaneously occur.

Tree-ring δ2H records of lignin methoxy indicate spring temperature changes since 20th century in the Qinling Mountains, China

Stable hydrogen isotope ratios of wood lignin methoxy groups (δ2HLM values) of mid-latitude forests are increasingly applied to reconstruct δ2H patterns in precipitation of regional to sub-continental scales. To date, the knowledge about the effect of topographic factors on δ2HLM values is still scare, especially in the biogeographic boundary. We measured tree-ring δ2HLM chronologies (1901–2018) from two typical conifer species at three sites with different altitudes of a north-ridge-south transect of the Qinling Mountains (central China), where covers the climate transition zone from warm temperate to subtropics. The δ2HLM chronologies of the north and the south slopes were characterized by a decreasing trend between 1901 and 1955, which turned into a positive trend after 1955. In contrast, the mountain ridge site located at the highest altitude showed continuous increasing δ2HLM values over the entire period from 1901 to 2018. The highest correlations between temperature and δ2HLM chronologies were found for the northern slope and the mountain ridge region spring temperatures (March–May). The observed abrupt changes in the δ2HLM values since the 1950s at lower elevation sites might reveal slope-related moisture effects which superimpose local temperature patterns. During the rapidly warming period 1955–2018, the higher correlations of the δ2HLM chronologies with the spring and mean annual (previous November to current October) temperatures were detected on the warmer northern slope. In summary, although the variations of measured δ2HLM of the three investigated sites reflect geographic-specific hydrological characteristics, the low-frequency temperature changes are documented in the δ2HLM values.

Effects of Topographic Factors on Cultivated-Land Ridge Orientation in the Black Soil Region of Songnen Plain

Topographic factors are essential to the spatial distribution of ridge orientation, yet the literature shows limited exploration of the mechanisms underlying the effects of terrain on cultivated-land ridge orientation in a black soil region. To better understand this subject, interpretation, statistical analyses and field verification were carried out in Songnen Plain, a typical Mollisol area. The results revealed that inclined-ridge cultivation was the most common farming method in the study area. When the slope gradient of cultivated land was greater than 13°, the influence of slope on ridge orientation was obvious, and the residual ridge angle increased with the increase in slope. There was a strongly significant negative correlation between the residual ridge angle and the azimuth angle, and the proportion curves of all ridge orientations with respect to different slope aspects were axisymmetric with respect to azimuth angles of 0°–180°. The relationship among indices such as slope gradient, slope aspect and ridge orientation could be modeled using a Poly2D function. This study indicates that topographic factors are the dominant factor in ridge-orientation selection, and provides a scientific basis for block-scale cultivated-land protection and utilization in black soil region; however, the scientific configuration of ridge orientation requires further research.

Environmental heterogeneity compensates the potential homogenising effect of abandonment of grazing in a sub-Mediterranean mountain landscape

ABSTRACT Background Anthropogenic mountain grasslands undergo major changes in their composition and structure after abandonment of their use as pastures or hay meadows. Distinct plant community-types may develop in habitats that differ in environmental conditions, such as soil water availability; however, few studies have addressed this issue in abandoned anthropogenic grasslands. Aims To quantify the effects of topographic factors and variables related to soil water availability on α and β taxonomic diversity (TD) and functional diversity (FD) to assess the role of landform heterogeneity in shaping vegetation structure. Methods We classified the vegetation of long-abandoned central Apennine pastures and related their species composition and diversity to environmental variables. Results We identified four community-types whose distribution was related to topographically determined soil water availability. The species composition of drought-tolerant communities on south-eastern slopes with shallow soils was largely similar to that of anthropogenic grasslands. Resource-poor conditions were related to enhanced α-TD and β-TD and reduced α-FD for traits related to temporal niche differentiation and resource acquisition strategies. Conclusion In long-abandoned sub-Mediterranean grasslands, landform heterogeneity guarantees a certain level of TD and FD at the landscape scale, contrasting the assumed role of abandonment of grazing on homogenisation of vegetation features.

A retrospective analysis of injury cases for visitor risk management in a nature-based touristic destination

ABSTRACT Outdoors organization is necessary in order to learn from prior experiences so as to create a proactive visitor risk management approach. Using retrospective analysis, this paper presents the epidemiology of visitor injuries at a forest recreation area in Taiwan. This article estimates that the injury rates occurred by weather and topographical factors using Poisson and negative binomial (NB) regression models, because the data characteristics in the current study are discrete and non-negative values. Weather variables, such as average temperature, relative humidity, and rain condition, have a positive relationship with visitor injury rate, which model selection criteria and goodness−of−fit showed to be the best fit for the NB model. The effects of topographic factors, namely average elevation and average slope of injury locations, are insignificant for visitor injury rate. Our finding confirms injury rates in nature are associated with weather, especially the appearance of rain. Each of these offers empirical evidence for future injury prevention programmes and for the proper perception of injury risk.

Effects of topographic factors on soil black carbon storage in coniferous forests at the north end of Greater Khingan Mountains

Effects of topographic factors on soil black carbon storage in coniferous forests at the north end of Greater Khingan Mountains

Effects of topographic factors on distribution of cacti along an elevation gradient in Brazilian Caatinga

Abstract The Cactacea family comprises 128 genera and 1450 species with predominantly neotropical distribution. Cacti are commonly found in arid and semi-arid regions and have great ecological relevance due to their interactions with animals and other groups of plants. Abiotic interactions, such as topography, altitude, rainfall, temperature and soils, also influence the composition and distribution of cacti. The objective of the present study was to assess patterns of species composition and distribution for cacti along an elevation gradient in Brazilian Caatinga vegetation. Four transects (composed by 25 plots of 100 m² each) were established at each of two mountain sites. The topographic variables of elevation, slope, rockiness and soil depth were evaluated to determine if they affect the distribution of richness and abundance of cacti along the elevation gradient using Spearman's (rs) correlation coefficient. A total of 554 individuals of five cacti species (Pilosocereus gounellei, Pilosocereus pachycladus, Tacinga palmadora, Tacinga inamoena and Melocactus zehntneri) were sampled. Cacti richness and abundance were found to be negatively correlated with elevation, slope and rockiness, and positively correlated with soil depth (p<0.05). All species exhibited aggregate spatial distribution patterns, which may be related to different environmental conditions produced by interactions among topographic variables (slopes, rockiness and soil depth), that synergistically influence the patterns of species richness and abundance along the elevation gradient.

UAV PHOTOGRAMMETRY-BASED FOR OPEN PIT COAL MINE LARGE SCALE MAPPING, CASE STUDIES IN CAM PHA CITY, VIETNAM

The use of lightweight Unmanned Aerial Vehicle with the aerial photogrammetry approach to construct the Digital Surface Model (DSM) has been effectively applied for various types of topography. However, the ability to carry out this approach for huge active open coal mines is insufficiently investigated, furthermore, the influences of topographical factors on the accuracy of DSM are ambiguous. This experiment attempts to apply the UAV method for the two active coal mines with the total area of 7.99 km2 , exploited at a range from -300 m to 300 m altitude to figure out the effect of topographic factors on the accuracy of DEM constructed from UAV images. A total of 972 UAV images and 17 ground control points have been coupled to construct DSM of the mines. Besides, 16 checking points located at different elevations are used to evaluate the accuracy of DEM and to define the influence. DEMs are generated with the maximum RMSE of 0.086 m, 0.099 m, and 0.170 m corresponding to X, Y, and Z dimensional errors. The results show the unclear correlation between the vertical accuracy of DEM and the relative elevation (R2=0.064), the general slope of the mines, and the number of ground control points using in the coal mines as well.

Topography Significantly influences the Growth Dynamics of Moso Bamboo Along a 10-year Chrono Sequence Following Afforestation

ABSTRACT Topography plays a critical role in the growth, development, and carbon accumulation of Moso bamboo. However, it is still unknown whether the effects of topography on the newly sprouted culms, the diameter at breast height (DBH) and the carbon stocks of newly sprouted culms (called carbon stocks below) vary temporally following Moso bamboo afforestation. In this study, thirty-one 20 × 20 m long-term sample plots were established and the DBH, age, height, and coordination of every newly sprouted culm were measured from 2009 to 2018. Four Moso bamboo expansion periods (rhizome expansion period, early period, middle period, and stable period) were divided according to the patterns of change of newly sprouted culms. Structural equation modeling and univariate analysis were combined to assess the dynamic effects of topographic factors (slope, aspect, slope position, and topographic complexity) and the effect of single topographic factors and their interactions on the carbon stocks during the four expansion periods. The result showed that the leading topographic factors influencing DBH, newly sprouted culms and carbon stocks were depended on the expansion period. Furthermore, the effective degree of leading topographic factor, aspect, decreased from the early period to a stable period. The four topographic factors studied here did not influence carbon stocks and newly sprouted culms during the stable period. The optimal interactions between carbon stocks and slope position and aspect (an east aspect of lower and upper slope positions) were relatively larger than those of a single aspect (east aspect), and significantly decreased in a stable period. Low topographic complexity was beneficial to the carbon accumulation under abrupt slopes but middle topographic complexity was needed under steeper slopes (steep and dangerous slope). Overall, this study offers a greater understanding of the effect of topography on Moso bamboo growth and provides a scientific basis for the selection of suitable afforestation locations for forest management.

Fire from policy, human interventions, or biophysical factors? Temporal–spatial patterns of forest fire in southwestern China

Forest fire is a recurrent and serious problem which stirs major environmental, economic, and social concerns. Information on the temporal–spatial distribution of ignition probability and identifying the factors that drive the pattern of forest fire occurrences are the most challenging issues over the world. In this study, the spatial distribution and temporal variation in forest fire occurrence were examined by applying the Maximum Entropy (Maxent) algorithm. Redundancy analyses were used to determine the contributions of driving factors (forest fire policy, human interventions, and biophysical variables) to the forest fire occurrences. In addition, the strength of the relationship between the forest fire policy, human interventions, and biophysical variables and their direct and indirect effects on forest fire occurrences were determined using structural equation models (SEMs). Our results showed the Maxent model was suitable for predictive modeling of the distribution of forest fire occurrences in southwestern China. The predicted area of forest fire occurrences in southwestern China during 2000–2017 was 3.25 × 105 km2 which mostly concentrated in the southern region. There was an increasing trend of forest fire crossing national and provincial borders. According to the temporal pattern of forest fire occurrences, additional ignition probability areas including the central Yunnan and the eastern Sichuan were found in spring when compared to those in winter. Moreover, forest fire policy is the main driver underlying the ignition, followed by biophysical factors and human interventions. These should be considered as key elements in the design of forest fire prevention programmes. Although the explanatory power of driving factors varied, national border distance (NBD) and conductive index (CI) that represented effects of forest fire policy were constantly the key driving variables. In addition, there is heterogeneity among the biophysical factors. The meteorological factors significantly affected on ignition probability in different temporal scale, while the effects of topographic factors were smaller. Human interventions had no significant direct effect on ignition probability, while they via fire policy had a significant positive indirect effect on the probability of fire occurrence. The results suggest that we should strengthen the administrative capacities to prevent forest fires, and improve the fire prevention publicity and education on the residents living near the national border and/or in low population density areas to get higher awareness and compliance of forest fire policies for local residents.

Effect of Slope on the Analysis of Forest Fire Risk

The main cause of forest fires is human activities. For this reason, when talking about the risk of forest fire in an area, it is mentioned about the intensity of human activities that can cause forest fire when vegetation and topographic compatibility are provided. In other words, although the type, amount, humidity and intensity of the combustible material is suitable with the effect of topographic factors in an area, if there is no human activity that will cause fire, only lightning caused forest fires can be mentioned. While evaluating the impact of slope on forest fire risk in our study, the starting points of the last 10 years forest fires have occurred in Turkey were analyzed with geographic information systems (GIS). Thus, it has been tried to make an objective assessment of the impact of the slope on forest fire risk. According to the results of the analysis, 40.53% of the forest fires which examined in Turkey occured in the range of slope between 0-10%. Therewithal, 87.16% of these fires occured in the range of slope between 0-30%. As a result, contrary to the general opinion, it is thought that the forest fire risk decrease as the slope increases.

Predicting Vegetation Carbon Density Distribution in different Terrains in Subtropical Forests in China

ABSTRACT Through large-scale afforestation and reforestation, China has increased its forest area and improved forest quality, making considerable contributions to carbon stocks of the world’s forests. As one of the important indicators of forest quality and carbon potential, vegetation carbon density (VCD) is affected by different factors at different scales, but little is known about the effect of topographic factors on the VCD of subtropical forests in the southeast of China, especially at a large regional scale. Based on the national forest continuous inventory protocols, more than 2000 permanent samples (2061 samples in 2009, 2115 samples in 2014, and 2132 samples in 2016) of major forest types (Bamboo forests (BB), broad-leaved forests (BF), mixed forests (MF), coniferous forests (CF)) were grouped by topographic factors to compare the distribution of VCD in Zhejiang Province of China. The four topographic factors (altitude, slope gradient, aspect, and slope position) explained 16.2%~28.4% of the variance in different forest types in the random forest model and the importance order of the four terrain variables is basically corresponding to the significance in the radar charts. The VCD of each forest type varies significantly at different altitudes (p < .05, except for the BB samples in 2009). In general, VCD tends to be higher at high altitudes. The VCD in BB and BF varies significantly with slope gradient (p < .05, the largest on the steep slope and the smallest on the gentle slope); however, the VCD of CF and MF showed almost no difference in different slope gradients. We found significant differences in VCD between the eight aspects in the mixed forest (p < .05, the largest in the S and SW aspects), but not in the other three forest types. As for different slope positions, the VCD of ridges is relatively large, and the VCD of the upslope is generally larger than that of the downslope (more pronounced in BB and BF, all p < .05). This study made a detailed analysis of the greening distribution in different topographic factors, and the research conclusion could provide a scientific basis for the selection of afforestation location and forest scientific management, and contribute to the improvement of the capability of coping with climate change in subtropical forests.

Topographic variables to determine the diversity of woody species in the exclosure of Northern Ethiopia

Exclosures are established with the objective of rehabilitating degraded lands and restoring of woody vegetation. Various studies have been conducted to evaluate the success of exclosure on restoring woody species diversity. However, works focusing on the effect of topographic factors on woody species diversity are scarce. Understanding the factors that determine woody species diversity is important for management purposes. Therefore, this paper analyzes the effect of altitude, slope, and aspect as topographic variables on woody species diversity in Dawsura exclosure in northern Ethiopia. Data on species identity, abundance, slope, elevation and aspect were recorded from 58 sampling plots. Different diversity indices were used to analyze the data and one-way ANOVA and linear regression was conducted. There were a total of 34 woody species represented 15 families, of which 62% and 38% were trees and shrubs respectively. Altitude (r2 = 0.63, p = 0.000 and r = 0.794, p < 0.01) and slope (r2 = 0.57, p = 0.002 and r = 0.68, p < 0.01) correlated significantly and positively with Shannon diversity, whereas aspect (r2 = 0.12, p = 0.378 and r = 0.27, p > 0.05) did not correlate significantly with Shannon diversity. Woody species diversity at moderate (1.44) and high (1.85) altitudes was significantly different from that of low (0.86) altitude areas (p = 0.0013). Furthermore, significantly higher woody species diversity was recorded at steep slope (1.88) and moderately steep slope (1.62) areas as compared to the gentle slope (0.95) areas. No significant variation was observed in woody species diversity among the aspect categories (p > 0.05). The study concludes that woody species diversity is largely regulated by slope and altitude than aspect in the exclosure. We suggest other environmental and anthropogenic variables should be taken into consideration in future studies on woody species diversity.

Analysis on Precipitable Water Vapor over the Tibetan Plateau Using FengYun-3A Medium Resolution Spectral Imager Products

The Tibetan Plateau is the largest and highest plateau in the world, and its complex terrain affects the distribution of precipitable water vapor (PWV) in the atmosphere, which plays an important role in the weather and climate of East Asia. In this paper, the characteristics of PWV over the Tibetan Plateau are studied using the FengYun-3A Medium Resolution Spectral Imager (MERSI) water vapor products, which are retrieved from the MERSI raw images of Chinese second-generation polar orbit meteorological satellite. Firstly, the accuracy of the MERSI 5-minute water vapor product is validated using three referenced water vapor data from TERRA/MODIS, ground-based GPS, and AERONET sun photometer over the Tibetan Plateau. Then, the spatial distribution and seasonal variation of PWV over the plateau are analyzed, and the effects of topographic factors on PWV are discussed. The results indicate that the MERSI 5-minute water vapor product has a good accuracy over the Tibetan Plateau, which the mean absolute error of MERSI water vapor product is in the range of 28.91%-37.54%, the mean absolute error range between 1.87 and 2.76 millimeter (mm), and the mean bias is between -1.14 and 0.64 mm comparing three referenced data. The PWV content appears as a typical spatial pattern over the Tibetan Plateau where there is a decrease from east to west of the Tibetan Plateau with increasing elevation, with the highest values over the south of Tibet. A second pattern also appears over the eastern part of the Tibetan Plateau, where the PWV content in the Qaidam Basin and the south of Tarim Basin are also considerably high. The seasonal variation of PWV content over the Tibetan Plateau presents to be highest in summer, followed by autumn and spring, and lowest in winter. The PWV content changes periodically during the year, which fits with a quadratic polynomial over monthly scales. The topographical factors of the Tibetan Plateau were found to affect the water vapor, where the altitude and latitude are negatively correlated with water vapor, while the slope and longitude show a positive correlation with water vapor; however, the aspect does not appear to have any significant influence on water vapor.

M58 LINKING VARIABILITY IN GUT MICROBIOME AND LARGE-SCALE BRAIN NETWORK CONNECTIVITY

Exclosures are established with the objective of rehabilitating degraded lands and restoring of woody vegetation. Various studies have been conducted to evaluate the success of exclosure on restoring woody species diversity. However, works focusing on the effect of topographic factors on woody species diversity are scarce. Understanding the factors that determine woody species diversity is important for management purposes. Therefore, this paper analyzes the effect of altitude, slope, and aspect as topographic variables on woody species diversity in Dawsura exclosure in northern Ethiopia. Data on species identity, abundance, slope, elevation and aspect were recorded from 58 sampling plots. Different diversity indices were used to analyze the data and one-way ANOVA and linear regression was conducted. There were a total of 34 woody species represented 15 families, of which 62% and 38% were trees and shrubs respectively. Altitude (r2 = 0.63, p = 0.000 and r = 0.794, p < 0.01) and slope (r2 = 0.57, p = 0.002 and r = 0.68, p < 0.01) correlated significantly and positively with Shannon diversity, whereas aspect (r2 = 0.12, p = 0.378 and r = 0.27, p > 0.05) did not correlate significantly with Shannon diversity. Woody species diversity at moderate (1.44) and high (1.85) altitudes was significantly different from that of low (0.86) altitude areas (p = 0.0013). Furthermore, significantly higher woody species diversity was recorded at steep slope (1.88) and moderately steep slope (1.62) areas as compared to the gentle slope (0.95) areas. No significant variation was observed in woody species diversity among the aspect categories (p > 0.05). The study concludes that woody species diversity is largely regulated by slope and altitude than aspect in the exclosure. We suggest other environmental and anthropogenic variables should be taken into consideration in future studies on woody species diversity.

Effects of topographic factors on leaf traits of apricot in the Loess Plateau, Northwest China

As important topographic factors, slope aspect and gradient affect plant growth and leaf functional traits by regulating the combination of water and heat. Exploring the response of leaf functional traits to topographic factors is helpful for understanding plant adaptation strategies. We investigated the effects of sunny slope (including half sunny slope) and shady slope (including half shady slope) and three slope gradient (15°-20°, 21°-25°, and 26°-30°) on the leaf functional traits of apricot (Prunus armeniaca L.), the main afforestation tree species on the Loess Plateau. The results showed that: 1) Slope aspect and gradient exerted significant effects on all functional traits. Except leaf water content (LWC), other leaf functional traits were not affected by the interaction of slope aspect and gradient. 2) The leaf area (LA) under the sunny slope was equivalent to that under the shady slope. Leaf dry matter content (LDMC) and LWC (0.27 g·g-1 and 67.0%, respectively) were significantly higher under the shady slope than under the sunny slope (0.24 g·g-1 and 59.6%, respectively), while specific leaf area (SLA) (163.05 cm2·g-1) was significantly lower under the former than under the latter (183.72 cm2·g-1). 3) At different slope gradients, SLA and LA reached a maximum value at 15°-20° (184.04 cm2·g-1) and 26°-30° (21.14 cm2), respectively. 4) Except no difference in soil water content (Θ) between 15°-20° and 26°-30°, it differed significantly between two slope aspects and among other slope gradients. The Θ was one of the main factors causing the differences in functional traits, especially in the 0-10 cm soil layer. 5) SLA was negatively correlated with LWC and LDW and positively correlated with LA. LDW was positively correlated with LWC and negatively correlated with LA. Θ was positively correlated with LWC but not with other leaf functional traits.

The effects of topographical factors on the distribution of plant communities in a mountain meadow on the Tibetan Plateau as a foundation for target-oriented management

Abstract Mountains are storehouses of biodiversity and natural resources. However, mountain rangeland is one of the most fragile ecosystems in the world due to the harsh natural conditions. The biodiversity and productivity in mountain regions are further under severe threat because of topography heterogeneity and poor management. To improve mountain rangeland management to sustain ecosystem services, we should better understand the relationships between topographical factors and plant distributions. The purpose was to elaborate on an alternative management strategy for mountain rangelands. In this study, we selected a hill covered by alpine meadow on the north-eastern Tibetan Plateau and quantified the effects of hill aspect and altitude on soil temperature, soil moisture, and plant and functional group distribution in terms of cover, height, frequency, richness, abundance and biomass in 189 quadrats on the hill. The results show that 1) with increasing altitude, the plant species cover, height, abundance, richness and biomass first increased and then decreased on the shadow aspect and on the ridge, whereas they increased linearly on the sunny aspect, 2) the altitude and aspect explained 58.6% of the total variance in the distribution of soil temperature and moisture, with aspect alone explaining 52.1% of the total variance and making the greatest contribution to the alpine meadow, and 3) the hill aspect had higher effects than the altitude on the distribution of species and functional groups in the community. The combined contributions of hill aspect and altitude and the individual effect of aspect alone were greater at the functional group level than at the species level. In conclusion, priority should be given to the differences in the soil and plant distribution caused by different aspects to provide a framework for designing tailored management plans for local farmers to preserve biodiversity on one hand whilst increasing productivity for economically viable farming and for preserving the provisioning of ecosystem services in mountain rangeland ecosystems on the other hand.

Remote Sensing of Watershed: Spectral Ratioing Study for Watershed Management

River catchments are basic hydrologic units and are important from the point of view of water budget management. There are longitudinal and seasonal variations in the catchment due spatio-temporal differences in terms of lithology, rainfall condition, intensity, land use land cover. Geospatial techniques and satellite data provide cost effective information about watershed. It is easy and profitable to use these techniques as data acquisition is easy, processing is fast Ratioing is one of the digital image processing technique useful to extract information about catchment characteristics and parameters for watershed development and planning. Indices give subtle tonal variations to identify the features spectrally. It de-emphasizes the effect of sun illumination, effect of topographic factors and highlights the region as per spectral properties of specific features. It enhances the quality of image to study the features in detail. These indices are also used to improve the accuracy of classification algorithms. For the current study Landsat-8 OLI used to study NDMI, EVI2, EBI, BSI, MNDWI and MODIS product MOD11A2 and MOD13A2 has used to study TCI, VCI and VHI indices. The study indicates that indices are one of the good techniques to extract spatially and temporally varying features. NDMI provides moisture condition information across watershed. EBAI and BSI highlights built up area and give idea about impervious surface. BSI gives information about bare soil where erosion mostly very common. EVI2 enhance the vegetation and MNDWI emphasize the waterbodies which seasonally varies. TCI, VCI and VHI useful to study drought conditions. The correlation between TCI and VHI, VCI and VHI studied to get information about drought. The above indices useful to study and extract several parameters to study runoff, erosion, sedimentation, ground water condition etc. Indices provide unidealistic information at various wavelengths. Repetitive coverage allows to monitoring dynamic features like water, vegetation, soil. Indices enhance the spectral information, increase the reparability of the classes of interest, and improve the quality of mapping. Such kind of technique’s are beneficial for conservation and management of the earth resources for local government bodies to conserve the water and to reduce the intensity of the drought.

Soil and water conservation measures reduce soil and water losses in China but not down to background levels: Evidence from erosion plot data

The efficacy of soil and water conservation measures (SWCMs) on reducing the loss of soil and water has been widely tested at the plot scale in China. However, an integrated comparison of the efficacy and an overall investigation of the controlling factors of the efficacy is absent. Therefore, an extensive dataset compiling erosion plot measurement of applying SWCMs on controlling soil loss and runoff in China was established in this study. In total, 848 erosion plots representing 2494 plot years were retained in this dataset which compiled from 108 publications and 2 data reports. The 15 most frequently tested SWCMs were identified and described. Soil loss ratio (SLR) and runoff ratio (RR) of each SWCMs was calculated to assess the efficacy of an SWCMs on reducing soil and water loss. The potential controlling factors, such as slope, slope length, annual precipitation, were evaluated for the controlling factor for both SLR and RR. Our results suggested that in general, applying the SWCMs can reduce soil loss by ca. 70% (overall SLR is 0.39 ± 0.02) and runoff by ca. 50% (overall RR is 0.54 ± 0.05), respectively. However, erosion rates on plots with SWCMs in China were, in general, still significantly higher than erosion rates measured under permanent vegetation cover land and, on average, ca. one order of magnitude higher than soil formation rates which required for a soil-neutral agriculture. On overall, the SLR presented a significant relation with topographic factors: positive with slope gradient and negative with slope length. This suggests that the support practice factor (P factor) of RUSLE model might be overestimated when values measured from plot scale are directly applied to larger areas (catchment or region scale). The SLR and RR values presented in this study can be applied for the planning of SWCMs in China and can be used to estimate the P factor when applying RUSLE model whereby the effect of topographic factors on SWCM efficacy can be accounted for.