Low Vegetation Density Research Articles

Does sheep grazing affect burrow choice of the pygmy bluetongue lizard (Tiliqua adelaidensis)?

The pygmy bluetongue lizard (Tiliqua adelaidensis) inhabits burrows originally dug by spiders in a few remaining fragments of native Australian grassland. These fragments are typically invaded by exotic plant species and subject to livestock grazing. We predicted that lizards prefer burrows in areas with reduced vegetation cover that will allow them to bask and see their invertebrate prey. We applied alternative grazing regimes to six experimental paddocks and found that sheep reduced vegetation density proportionally to the grazing intensity. Within each paddock, independent of the level of grazing, and in seven of the eight surveys, lizard burrows were in locations with lower vegetation density than random points However lizards moving between burrows in spring showed a tendency to choose burrows with relatively more surrounding vegetation. Our initial hypothesis that lizards would prefer burrows with an intermediate level of grazing that produced some reduction of vegetation cover was not completely supported, probably because lizards often choose burrows early in spring when grasslands have denser vegetation cover, and then tend to remain in the same burrow as grazing or seasonal drying reduces vegetation cover. Changes in vegetation do not seem to induce lizard movement.

京津冀地区城市化对植被覆盖度及景观格局的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 京津冀地区城市化对植被覆盖度及景观格局的影响 DOI: 10.5846/stxb201608311779 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金重大项目（41590841）；全国生态环境十年变化（2000-2010年）遥感调查与评估项目（STSN-12-01）；环境保护部专项（2110203） Spatiotemporal pattern of vegetation cover and its relationship with urbanization in Beijing-Tianjin-Hebei megaregion from 2000 to 2010 Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:定量研究了2000-2010年，京津冀地区植被覆盖度及其景观格局的动态变化，揭示了城市化进程对植被景观的干扰过程及生态质量的影响。结果表明：（1）2000-2010年，城市化进程显著是京津冀城市群土地变化的一大特点，人工表面面积从2000年的1.79×104 km2增加至2.16×104 km2，增幅高达21.16%；（2）京津冀平均植被覆盖度呈增加趋势但不显著（P=0.46），存在明显的时空动态差异。在覆盖度结构上形成了以中低和中植被覆盖度为主导的格局；（3）从景观空间格局变化来看，中低、高覆盖度区域植被景观更加破碎，而低、中等覆盖度区域的植被面积增加，景观破碎度减小；尤其是低植被覆盖度为主的城市区域，景观格局变化幅度大，表现为绿地面积有所增加，景观破碎化程度降低，生态质量有所改善；（4）在整个研究区范围，城市化对区域植被覆盖度存在负面影响，表现为城市化程度与区域平均植被覆盖度存在负相关（P=0.08）；但是在低植被覆盖度的区域（主要为城市区域），城市化程度与植被覆盖面积呈显著正相关（P < 0.001），表明城市区域在城市化进程中植被覆盖面积有所提高，生态质量有所改善，与城市化过程中，日益重视城市绿地的建设有关。 Abstract:Accelerated urbanization and socio-economic development can cause a series of environmental problems, such as decreased ecological quality. Accurately and efficiently quantifying the effects of urbanization on vegetation is critical for understanding regional ecological conservation and achieving sustainable development. Previous studies have primarily focused on the spatiotemporal patterns of vegetation cover and its relationship with climatic factors. Here, we quantified the spatiotemporal patterns of vegetation cover from 2000 to 2010 in the Beijing-Tianjin-Hebei megaregion. We then analyzed the effects of urbanization on vegetation cover dynamics. We used MODIS data and Landsat TM data. We found that (1) during the study period, urban land expanded very rapidly in this megaregion. The area of built-up lands increased from 1.79×104 km2 in 2000 to 2.16×104 km2 in 2010, which is an increase of 21.16%. (2) There was a slight but insignificant (P= 0.45) increasing trend in vegetation coverage from 2000 to 2010. The region was dominated by low-medium and medium coverage vegetation. (3) There were similarities and differences in the spatiotemporal patterns among different types of vegetation with varied levels of vegetation density. For vegetation types with low to medium and high vegetation density, fragmentation of vegetation increased from 2000 to 2010. In contrast, for vegetation types with low and medium vegetation density, the landscape pattern became more aggregated rather than fragmented in regions covered with these types of vegetation. (4) The proportional cover of developed land and vegetation coverage showed negative correlations (P= 0.08). However, the proportional cover of developed land showed a significantly positive relationship with the proportion of area covered by vegetation types with low vegetation density (P < 0.001). 参考文献 相似文献 引证文献

Impact assessment of land cover changes on the runoff changes on the extreme flood events in the Kelantan River basin

In the current years, changing the land cover/land use had serious hydrological impacts affecting the flood events in the Kelantan River basin. The flood events at the east coast of the peninsular Malaysia got highly affected in the recent decades due to several factors like urbanisation, rapid changes in the utilisation of land and lack of meteorological (i.e. change in climate) and developmental monitoring and planning. The Kelantan River basin has been highly influenced due to a rapid change in land use during 1984 to 2013, which occurred in the form of transformation of agricultural area and deforestation (logging activities). In order to evaluate the influence of the modifications in land cover on the flood events, two hydrological regional models of rainfall-induced runoff event, the Hydrologic Engineering Center (HEC)-Hydrologic Modeling System (HMS) model and improved transient rainfall infiltration and grid-based regional model (Improved TRIGRS), were employed in this study. The responses of land cover changes on the peak flow and runoff volume were investigated using 10 days of hourly rainfall events from 20 December to the end of December 2014 at the study area. The usage of two hydrological models defined that the changes in land use/land cover caused momentous changes in hydrological response towards water flow. The outcomes also revealed that the increase of severe water flow at the study area is a function of urbanisation and deforestation, particularly in the conversion of the forest area to the less canopy coverage, for example, oil palm, mixed agriculture and rubber. The monsoon season floods and runoff escalate in the cleared land or low-density vegetation area, while the normal flow gets the contribution from interflow generated from secondary jungle and forested areas.

Acoustic evaluation of modular greenery noise barriers

Green noise barriers have become an alternative means of reducing urban traffic noise. In this paper, the acoustic performance of a modular greenery noise barrier is evaluated. In situ measurements of noise reflection were performed using an experimental prototype to estimate the sound absorption coefficients. These coefficients were found to have values of approximately 0.7, higher than those previously found in laboratory measurements for a similar system with a lower vegetation density. The obtained values were input into software for predicting environmental noise to analyse the expected performance of such barriers, particularly in the case of a pair of parallel barriers. A comparison with the results for reflective barriers indicates a significant improvement in sound attenuation of up to 4dBA. The values are similar and even superior to results reported by other authors regarding the effectiveness of absorptive treatments applied to parallel barriers, and furthermore, the proposed barriers offer an aesthetic element for environmental integration.

The impact of climatic and non-climatic factors on land surface temperature in southwestern Romania

Land surface temperature is one of the most important parameters related to global warming. It depends mainly on soil type, discontinuous vegetation cover, or lack of precipitation. The main purpose of this paper is to investigate the relationship between high LST, synoptic conditions and air masses trajectories, vegetation cover, and soil type in one of the driest region in Romania. In order to calculate the land surface temperature and normalized difference vegetation index, five satellite images of LANDSAT missions 5 and 7, covering a period of 26 years (1986–2011), were selected, all of them collected in the month of June. The areas with low vegetation density were derived from normalized difference vegetation index, while soil types have been extracted from Corine Land Cover database. HYSPLIT application was employed to identify the air masses origin based on their backward trajectories for each of the five study cases. Pearson, logarithmic, and quadratic correlations were used to detect the relationships between land surface temperature and observed ground temperatures, as well as between land surface temperature and normalized difference vegetation index. The most important findings are: strong correlation between land surface temperature derived from satellite images and maximum ground temperature recorded in a weather station located in the area, as well as between areas with land surface temperature equal to or higher than 40.0 °C and those with lack of vegetation; the sandy soils are the most prone to high land surface temperature and lack of vegetation, followed by the chernozems and brown soils; extremely severe drought events may occur in the region.

THE STUDY OF TEMPORAL CHANGES ON LAND COVER/LAND USE PREVAILING IN BAGHDAD GOVERNORATE USING RS &amp; GIS

This study was carried out in order to identify and mapping the temporal changes for land covers in Baghdad province using Remote Sensing and GIS. Three images were used of land sate taken in 1976, 2000 and 2014 the study area. Suppervised classification and SAVI Index were used to identify land cover classes dominated in the study area. The results of supper classification indicated the presence of five land cover classes including water bodies, bare land, urban, low dense vegetation, and dense vegetation classes. There were four classes of land cover when was used SAVI index: water, no vegetation (bare land and urban), low dense vegetation, and dense vegetation. The results showed that Remote Sensing is a very active and useful tool that can be used to detect land core types. The results showed a decline in class of water bodies from 2.8% to 1.5% for 1976 to 1990 while in 2014 increased to 2.1%. class Urban areas increased continuously with time and accounted for 17.6% , 23.5% and 28.2 % for years of study, indicating the existence of the phenomenon of urban encroachment. Bare land areas accounted for 29.3% , 26.8% and 33.5% of stady years, respectively. The class of low dense vegetation decreased from 44.8% to 31.7% and 29.4% for 1976, 1990 and 2014 respectively, while the class-Dense vegetation increased at 1976-1990 from 5.5% to 16.4% and decreased in 2014 to 6.8%. The SAVI had a role in the detection of agriculture and gave results same to the results of super classification. Results indicated that urban land and salinization process can be consider as the most phenomenon which negatively affected on agriculture area.

Prospects of the ICESat-2 laser altimetry mission for savanna ecosystem structural studies based on airborne simulation data

The next planned spaceborne lidar mission is the Ice, Cloud and land Elevation Satellite 2 (ICESat-2), which will use the Advanced Topographic Laser Altimeter System (ATLAS) sensor, a photon counting technique. To pre-validate the capability of this mission for studying three dimensional vegetation structure in savannas, we assessed the potential of the measurement approach to estimate canopy height in an oak savanna landscape. We used data from the Multiple Altimeter Beam Experimental Lidar (MABEL), an airborne photon counting lidar sensor developed by NASA’s Goddard Space Flight Center. ATLAS-like data was generated using the MATLAS simulator, which adjusts MABEL data’s detected number of signal and noise photons to that expected from the ATLAS instrument. Transects flown over the Tejon ranch conservancy in Kern County, California, USA were used for this work. For each transect we chose to use data from the near infrared channel that had the highest number of photons. We segmented each transect into 50m, 25m and 14m long blocks and aggregated the photons in each block into a histogram based on their elevation values. We then used an automated algorithm to identify cut off points where the cumulative density of photons from the highest elevation indicates the presence of the canopy top and likewise where such cumulative density from the lowest elevation indicates the mean terrain elevation. MABEL derived height metrics were moderately correlated to discrete return lidar (DRL) derived height metrics (r2 and RMSE values ranging from 0.60 to 0.73 and 2.9m to 4.4m respectively) but MATLAS simulation resulted in more modest correlations with DRL indices (r2 ranging from 0.5 to 0.64 and RMSE from 3.6m to 4.6m). Simulations also indicated that the expected number of signal photons from ATLAS will be substantially lower, a situation that reduces canopy height estimation precision especially in areas of low density vegetation cover. On the basis of the simulated data, there is reason to believe that the ability of ICESat-2 to estimate height in savannas will be comparable to the original ICESat mission although the respective sensors have different measurement principles.

Cartographie De L’erosion Qualitative Des Sols Du Bassin Versant De L’aoudour (Rif-Maroc)

The Aoudour watershed located in the northwest of Morocco and spreads over an area of approximately 1000 km2, and occupying the northeastern part of the Ouergha basin contently experiencing the effects of severe water erosion caused by the interaction of several natural factors such as the amount and aggressiveness of rainfall, plenty of steep slopes, low vegetation density and also the dominance of friable land. The Aoudour watershed also undergoes a human action that makes it very vulnerable to environment erosion, the degradation of the vegetation cover in recent decades and also by poor farming techniques. PAP / RAC is a method of qualitative study of water erosion that can prioritize the surface of a watershed in separate units according to its vulnerability to erosion. The method consists of a descriptive and predictive mapping in relation to the identification; evaluation and integration of basic physical factors such as slope, lithology and / or soils and vegetation cover, with the aim of establish initial assumptions about the risk of erosion. The use of remote sensing and GIS tools enabled us creating and overlying of thematic maps, executing speedily the cartographic works and, processing of databases.

Vegetation dynamics and their response to groundwater and climate variables in Qaidam Basin, China

ABSTRACTThis article discusses an evaluation of Moderate Resolution Imaging Spectroradiometer (MODIS) time-series data for monitoring vegetation variation in Qaidam Basin, Northwest China. In this study, 16 day composite 250 m normalized difference vegetation index (NDVI) products (MOD13Q1) acquired from 2000 to 2011 were processed to determine vegetation cover fraction (VCF) for detecting the annual dynamics of different types of vegetation cover in the basin and the products were validated by comparing field measurement in spatial distribution. The results show that the annual NDVI value increased from 0.126 to 0.172 on average between 2000 and 2011. The basin interior is dominated by desert and 74% of the area is covered by low-density shrubs and bare soil. Both areas of bare soil and low-density vegetation present a decreased rate, whereas medium-, medium-high-, and high-density vegetation show increase trends in the vegetation cover. Generally, the vegetation fluctuation depends on various attributes such as climate change, elevation, water table depth, and total dissolved solids (TDS) in arid areas. We found strong statistical correlation between NDVI time series and climatic factors such as air temperature and precipitation. There is also an agreement between the spatial distribution of NDVI value and elevation, because elevation has important impacts on the distribution of vegetation pattern, which are different in coverage. The vegetation dependent on water table depth is more complicated: shrubs of Phragmites australis, Artemisia desertorum, and Tamarix ramossissima Ledeb. are sensitive to water table depth and the maximum NDVI occurred at a water table depth shallower than 2 m. However, high-height shrub such as Nitraria Schoberi L. reflects less dependence on water table depth. Normally, vegetation can develop well at TDS between 0 and 3 g l−1 whereas Tamarix ramossissima Ledeb. can still survive when the TDS is larger than 8 g l−1.

Detecting the Temporal Scaling Behavior of the Normalized Difference Vegetation Index Time Series in China Using a Detrended Fluctuation Analysis

Vegetation is an important part of terrestrial ecosystems. Although vegetation dynamics have explicit spatial and temporal dimensions, the study of the temporal process is in its infancy. Evaluation of temporal scaling behavior could provide a unique perspective for exploring the temporal nature of vegetation dynamics. In this study, the Global Inventory Modeling and Mapping Studies (GIMMS) Normalized Difference Vegetation Index (NDVI) was used to reflect vegetation dynamics, and the temporal scaling behavior of the NDVI in China was determined via detrended fluctuation analysis (DFA). Our main objectives were to reveal the temporal scaling behavior of NDVI time series and to understand variation among vegetation types. First, DFA revealed similar exponents, which ranged from 0.6 to 0.9, for all selected pixels, implying that a long-range correlation was generally present in the NDVI time series at the individual pixel scale. We then extended the analysis to all of China and found that 99.30% of the pixel exponents ranged from 0.5 to 1. These results suggest that the NDVI time series displays strong long-range correlation throughout most of China; however, the exponents exhibited regional variability. To explain these differences, we further analyzed the exponents for 12 vegetation types based on a vegetation map of China. All of the vegetation types exhibited well-defined long-range correlation, with exponents ranging from 0.7189 to 0.8436. For all vegetation types, the maximum and average value and standard deviation of the exponents decreased with increasing annual maximum NDVI values, suggesting that low vegetation density is much more sensitive to external factors. These findings may be useful for understanding vegetation dynamics as a complex, temporally varying phenomenon.

Microhabitat selection and diel patterns of zooplankton in a Mediterranean temporary pond

Changes in zooplankton microhabitat use in lakes through diel migrations (vertical and horizontal) have been related to habitat heterogeneity and to predation pressure, among other factors. However, there is a controversy concerning the effectiveness of diel migrations in temporary ponds, due to the shallowness of these systems and their distinct aquatic predator communities (mainly macroinvertebrates and amphibians). In order to test if diel microhabitat selection patterns described from lakes hold in temporary ponds, we developed a study using funnel traps at different zones of the pond (high and low vegetation density; surface and bottom of the pond) that were checked during the day and at night. Additionally, we assessed predation risk by sampling the macroinvertebrate community at the same time. In the studied Mediterranean temporary pond, zooplankton exhibited diel patterns of microhabitat selection: cladocerans showed a diel horizontal pattern, whereas copepods showed a diel vertical pattern. Results suggest that microhabitat selection and the associated diel pattern may be explained by both biological (potential predation) and environmental drivers (habitat heterogeneity and protection against ultraviolet radiation).

An Analysis of Overstory Tree Canopy Cover in Sites Occupied by Native and Introduced Cottontails in the Northeastern United States with Recommendations for Habitat Management for New England Cottontail.

The New England cottontail (Sylvilagus transitionalis) is a high conservation priority in the Northeastern United States and has been listed as a candidate species under the Endangered Species Act. Loss of early successional habitat is the most common explanation for the decline of the species, which is considered to require habitat with dense low vegetation and limited overstory tree canopy. Federal and state wildlife agencies actively encourage landowners to create this habitat type by clearcutting blocks of forest. However, there are recent indications that the species also occupies sites with moderate overstory tree canopy cover. This is important because many landowners have negative views about clearcutting and are more willing to adopt silvicultural approaches that retain some overstory trees. Furthermore, it is possible that clearcuts with no overstory canopy cover may attract the eastern cottontail (S. floridanus), an introduced species with an expanding range. The objective of our study was to provide guidance for future efforts to create habitat that would be more favorable for New England cottontail than eastern cottontail in areas where the two species are sympatric. We analyzed canopy cover at 336 cottontail locations in five states using maximum entropy modelling and other statistical methods. We found that New England cottontail occupied sites with a mean overstory tree canopy cover of 58% (SE±1.36), and was less likely than eastern cottontail to occupy sites with lower overstory canopy cover and more likely to occupy sites with higher overstory canopy cover. Our findings suggest that silvicultural approaches that retain some overstory canopy cover may be appropriate for creating habitat for New England cottontail. We believe that our results will help inform critical management decisions for the conservation of New England cottontail, and that our methodology can be applied to analyses of habitat use of other critical wildlife species.

Computational modeling of flow and morphodynamics through rigid-emergent vegetation

The flow and bed morphodynamics through rigid, emergent cylinders which are regarded as vegetation are computed using a three-dimensional numerical model by employing a large-eddy simulation approach with a ghost-cell immersed-boundary method. The scour and transport processes are solved using sophisticated sediment transport and morphodynamic models in a physics-based manner. In an infinitely long patch, the vegetation density significantly influences the flow and morphodynamic behavior. Under a low vegetation density, the scour and deposition are similar to those of an isolated cylinder, while there are significant variations at a higher vegetation density. The cylinder-interval variation has a negligible impact on the maximum scour depth, which is similar to that in an isolated cylinder case. In the high-vegetation-density case, a decrease in cylinders in a selected domain decreases the physical realism of the morphodynamic process. The scour and transport processes in a partly vegetated small patch show a significant difference, compared to the long patch. In this case, local and global scours are observed around the small patch and the maximum scour always occurs around the front cylinders (i.e., leading edge). The scour depth increases with a decrease in the cylinder interval, and the computed scour depths and trends agree well with the measured data in the literature.

Applicability of VI in arid vegetation delineation using shadow-affected SPOT imagery.

GDVI(3), GDVI(2), NDVI, MSAVI and SAVI were evaluated for their dynamic ranges, the class accuracy of the Vegetation Index (VI) classifications, the effects of shadow delineation on the other land use classes and their applicability in vegetation delineation in Al-Qara Mountains, Oman. Supervised classifications of a SPOT scene by Support Vector Machines (SVM) algorithm were employed. GDVI(3) showed the widest dynamic range in all land use types, while GDVI(2) also exhibited evidently wider dynamic ranges for arid to semi-arid Al-Qara than NDVI, MSAVI and SAVI. GDVI(3) reported the highest accuracies in delineating natural vegetation (dense - 74.80%, medium-dense- 43.19%), except for low-dense vegetation (40.51%). It also performs the best in delineating bare soil and dry grass with over 80% and 60% accuracies. The attenuated reflectance created by the shadows results in VI signals in the range of dry grass to bare soil, enabling us to neglect the shadow effect on natural vegetation delineation due to below 9.50% omissions from the shadows class. GDVI(3) also limits shadow delineation better than the other indices, which will enable us to analyze spectral information recovery by the VI with the help of ground truth information under the shadows. For applications such as land degradation assessments, GDVI(3) has better prospects over the other indices explored. Saturation at high-vigor vegetation is an issue in GDVI(3), GDVI(2) and NDVI. Our study also points to a dependency of a VI's capability to weaken shadows on the number of training data pixels to be utilized in a supervised classification.

Simulation of Flows through Submerged Vegetation Patches Using Macroscopic Turbulence Models

Macroscopic approach incorporating the spatial averaging procedure is commonly used to investigate turbulent flows in porous media, terrestrial and aquatic canopies. In this work the hydrodynamics of flows through a semi-rigid vegetation patch (VP) was investigated with two macroscopic turbulence models. We modified the Reynolods Averaged Navier Stokes (RANS) equations to obtain the Volume Averaged (VARANS) equations and performed simulations using the open source code OpenFOAM. The numerical results of gradually varied flows over submerged VPs are compared with the corresponding experimental measurements. The results show that the macroscopic turbulence models simulate the velocity profiles with acceptable accuracy. The increase of vegetation density generates higher Reynolds stress around the top of vegetation and smaller velocity inside the VP. The two models perform differently in the computation of Reynolds stress, with the profiles from the model of Uittenbogaard (2003) requiring a shorter distance to reach the uniform state for the case of low vegetation density. Further works will be carried out to identify the cause of difference and to achieve a refined macroscopic turbulence model.

The Impact of Tourism Development on the Structure of Agricultural Landscape of the Dongshan River Basin, Taiwan

After the establishment of the Dongshan River Scenic Area of Yilan County in Taiwan, land use in the Dongshan River Basin has undergone dramatic change, from agricultural areas to recreational settings, in the past decades. The pur- pose of this study was to apply the approach of landscape ecology to analyze the spatiotemporal transition of the agricultural landscape of the river basin after tour- ism development. The study aimed to examine the landscape change in the river ba- sin and its ecological implications. Maps of the Dongshan River Basin in 1987 and 2003 were generated, and the land uses were grouped into six land-use types: paddy fields, high-density vegetation, low-density vegetation, water, built-up land, and sandy beaches. A set of landscape metrics were computed with FRAGSTATS. The results showed that, from 1987 to 2003, the major change in the river basin land- scape was a rapid increase in the area of built-up patches, while the areas for all other land use decreased. As for paddy fields, although their overall structure was not significantly altered over the study period, 5% (301 hectares) of the paddy fields had been replaced by urban settlements, which included the river park, the booming country house scene, and a traditional arts center. These changes were the main con- tributors to the increasing patch edge of paddy fields. Viewing paddy fields in Dong- shan River Basin as unique man-made habitats, attention is then given to both the dispersion of built-up patches and the increase in size of the patch edge of paddy fields.

Aquatic vegetation indices assessment through radiative transfer modeling and linear mixture simulation

Although spectral vegetation indices (VIs) have been widely used for remote sensing of vegetation in general, such indices have been traditionally targeted at terrestrial, more than aquatic, vegetation. This study introduces two new VIs specifically targeted at aquatic vegetation: NDAVI and WAVI and assesses their performance in capturing information about aquatic vegetation features by comparison with pre-existing indices: NDVI, SAVI and EVI. The assessment methodology is based on: (i) theoretical radiative transfer modeling of vegetation canopy-backgrounds coupling, and (ii) spectral linear mixture simulation based on real-case endmembers. Two study areas, Lake Garda and Lakes of Mantua, in Northern Italy, and a multisensor dataset have been exploited for our study. Our results demonstrate the advantages of the new indices. In particular, NDAVI and WAVI sensitivity scores to LAI and LIDF parameters were generally higher than pre-existing indices’ ones. Radiative transfer modeling and real-case based linear mixture simulation showed a general positive, non-linear correlation of vegetation indices with increasing LAI and vegetation fractional cover (FC), more marked for NDVI and NDAVI. Moreover, NDAVI and WAVI show enhanced capabilities in separating terrestrial from aquatic vegetation response, compared to pre-existing indices, especially of NDVI. The new indices provide good performance in distinguishing aquatic from terrestrial vegetation: NDAVI over low density vegetation (LAI<0.7–1.0, FC<40–50%), and WAVI over medium-high density vegetation (LAI>1.0, FC>50%). Specific vegetation indices can therefore improve remote sensing applications for aquatic vegetation monitoring.

Albedo and land surface temperature shift in hydrocarbon seepage potential area, case study in Miri Sarawak Malaysia

The presence of hydrocarbon seepage is generally associated with rock or mineral alteration product exposures, and changes of soil properties which manifest with bare development and stress vegetation. This alters the surface thermodynamic properties, changes the energy balance related to the surface reflection, absorption and emission, and leads to shift in albedo and LST. Those phenomena may provide a guide for seepage detection which can be recognized inexpensively by remote sensing method. District of Miri is used for study area. Available topographic maps of Miri and LANDSAT ETM+ were used for boundary construction and determination albedo and LST. Three land use classification methods, namely fixed, supervised and NDVI base classifications were employed for this study. By the intensive land use classification and corresponding statistical comparison was found a clearly shift on albedo and land surface temperature between internal and external seepage potential area. The shift shows a regular pattern related to vegetation density or NDVI value. In the low vegetation density or low NDVI value, albedo of internal area turned to lower value than external area. Conversely in the high vegetation density or high NDVI value, albedo of internal area turned to higher value than external area. Land surface temperature of internal seepage potential was generally shifted to higher value than external area in all of land use classes. In dense vegetation area tend to shift the temperature more than poor vegetation area.

Infestation by Hypoderma tarandi in reindeer calves from northern Finland—Prevalence and risk factors

Serum samples from 953 reindeer (Rangifer t. tarandus) calves-of-the-year from 21 reindeer herding co-operatives in Finland in slaughter season 2006/2007 were assayed for antibodies against Hypodermin C by an ELISA detecting IgG. Data on presence of Hypoderma tarandi larvae on 12,327 reindeer hides from 17 of the 21 herding co-operatives in slaughter season 2005/2006 were included for support. ELISA showed a seroprevalence of 60.9%, with no significant difference between females and males, and increase with latitude (southernmost and northernmost co-operatives examined, Pudasjärvi and Kaldoaivi, 11.8 and 100% of seropositives, respectively). The proportion of larva positive hides (range 0.5–60% per co-operative) was low compared to the proportion of seropositives. Also the proportion of larva positive hides increased with latitude. Our findings indicated that high latitude combined with open landscape, presence of low vegetation and high reindeer density provided more favorable conditions for sustaining of high degree of warble fly infestation, and furthermore, that any possible effect of ivermectin treatment on infestation rate was ruled out by the higher effect by the above factors.

Geographic information systems and logistic regression for high-resolution malaria risk mapping in a rural settlement of the southern Brazilian Amazon.

BackgroundIn Brazil, 99% of the cases of malaria are concentrated in the Amazon region, with high level of transmission. The objectives of the study were to use geographic information systems (GIS) analysis and logistic regression as a tool to identify and analyse the relative likelihood and its socio-environmental determinants of malaria infection in the Vale do Amanhecer rural settlement, Brazil.MethodsA GIS database of georeferenced malaria cases, recorded in 2005, and multiple explanatory data layers was built, based on a multispectral Landsat 5 TM image, digital map of the settlement blocks and a SRTM digital elevation model. Satellite imagery was used to map the spatial patterns of land use and cover (LUC) and to derive spectral indices of vegetation density (NDVI) and soil/vegetation humidity (VSHI). An Euclidian distance operator was applied to measure proximity of domiciles to potential mosquito breeding habitats and gold mining areas. The malaria risk model was generated by multiple logistic regression, in which environmental factors were considered as independent variables and the number of cases, binarized by a threshold value was the dependent variable.ResultsOut of a total of 336 cases of malaria, 133 positive slides were from inhabitants at Road 08, which corresponds to 37.60% of the notifications. The southern region of the settlement presented 276 cases and a greater number of domiciles in which more than ten cases/home were notified. From these, 102 (30.36%) cases were caused by Plasmodium falciparum and 174 (51.79%) cases by Plasmodium vivax. Malaria risk is the highest in the south of the settlement, associated with proximity to gold mining sites, intense land use, high levels of soil/vegetation humidity and low vegetation density.ConclusionsMid-resolution, remote sensing data and GIS-derived distance measures can be successfully combined with digital maps of the housing location of (non-) infected inhabitants to predict relative likelihood of disease infection through the analysis by logistic regression. Obtained findings on the relation between malaria cases and environmental factors should be applied in the future for land use planning in rural settlements in the Southern Amazon to minimize risks of disease transmission.