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1.
Crop damages by wildlife is a frequent form of human-wildlife conflict. Identifying areas where the risk of crop damages is highest is pivotal to set up preventive measures and reduce conflict. Species distribution models are routinely used to predict species distribution in response of environmental changes. The aim of this paper was assessing whether species distribution models can allow to identify the areas most at risk of crop damages, helping to set up management strategies aimed at the mitigation of human-wildlife conflicts. We obtained data on wild boar Sus scrofa damages to crops in the Alta Murgia National Park, Southern Italy, and related them to landscape features, to identify areas where the risk of wild boar damages is highest. We used MaxEnt to build species distribution models. We identified the spatial scale at which landscape mostly affects the distribution damages, and optimized the regularization parameter of models, through an information-theoretic approach based on AIC. Wild boar damages quickly increased in the period 2007-2011; cereals and legtmaes were the crops more affected. Large areas of the park have a high risk of wild boar damages. The risk of damages was related to low cover of urban areas or olive grows, intermediate values of forest cover, and high values of shrubland cover within a 2-km radius. Temporally independent validation data demonstrated that models can successfully predict damages in the future. Species distribution models can accurately identify the areas most at risk of wildlife damages, as models calibrated on data collected during only a subset of years correctly predicted damages in the subsequent year [Current Zoology 60 (2): 170-179, 2014].  相似文献   

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3.
Recursion by herbivores is the repeated use of the same site or plants. Recursion by wild animals is rarely investigated but may be ubiquitous. Optimal foraging theory predicts site recursion as a function of the quality of the site, extent of its last use, and time since its last use because these influence site resource status and recovery. We used GPS collars, behaviour and site sampling to investigate recursion to foraging sites for two elephant Elephas maximus borneensis herds in the Lower Kinabatangan Wildlife Sanctuary, Borneo, over a 12 month period. Recursion occurred to 48 out of 87 foraging sites and was most common within 48 hours or between 151-250 days, indicating two different types ofrecursion. Recursion was more likely to occur if the site had previously been occupied for longer. Moreover, the time spent at a site at recursion was the same as the time spent at the site on the first occasion. The number of days that had passed between the first visit and recursion was also positively correlated with how much time was spent at the site at recursion. Habitat type also influenced the intensity of site-use, with more time spent at recursion within riverine/open grass areas along forest margins compared to other habitat types. Recursion is a common behaviour used by the elephants and its pattern suggests it may be a foraging strategy for revisiting areas of greater value. The qualities of recursion sites might usefully be incorporated into landscape management strategies for elephant conservation in the area [Current Zoology 60 (4): 551-559, 2014].  相似文献   

4.
It is well known that forest carbon or sink projects have not been included in theClean Development Mechanism (CDM), one of the flexible mechanisms created under the Kyoto Protocol. The main concern for postponing sink projects is related to issues of methodology and integrity. Project eligibility needs to be judged in a transparent manner if they are real, measurable,provide long-term benefits to mitigate climate change, and provide additional benefits to those thatwould occur in the absence of a certified project. One of the biggest challenges in implementing sink projects is fire risks and the associated biophysical and socio-economic underlying causes. This study attempts to assess fire probability and use it as a tool to estimate fire risk in carbon sink projects. Fire risks may not only threatenongoing projects but may also cause leakage of carbon stocks in other areas, especially in pro-tected areas. This exercise was carried out in the Berbak National Park located in Jambi Province, Sumatra, Indonesia and the surrounding areas. Fire probability is associated with (i) the means by which access to a given area is possible, and (ii) vegetation type or fuel load. Although most fires were intentionally ignited, fire escape iscommon and is enhanced by long spell of dry weather. When this occurs, secondary road was themost frequently used means, and it was certainly the case during 1997/1998 big fires when dam-age to natural vegetation (natural and secondary forests) was substantial. Burnt natural vegetationwas 120000 ha or 95% of the total burnt areas, and released more than 7 Mt of carbon into the atmosphere.  相似文献   

5.
Evaluating the annual sources and sinks of carbon from land-use change helps con-strain other terms in the global carbon cycle and may help countries choose how to comply with commitments for reduced emissions. This paper presents the results of recent analyses ofland-use change in China and tropical Asia. The original forest areas are estimated to have cov-ered 546×10~6 ha in tropical Asia and 425×10~6 ha in China. By 1850, 44% of China's forests had been cleared, and another 27% was lost between 1850 and 1980, leaving China with 13% forestcover (29% of the initial forest area). Tropical Asia is estimated to have lost 26% of its initial forestcover before 1850 and another 33% after 1850. The annual emissions of carbon from the two regions re-flect the different histories over the last 150 years, with China's emissions peaking in thelate 1950s (at 0.2-0.5 Pg C·a~(-1)) and tropical Asia's emissions peaking in 1990s (at 1.0 Pg C·a~(-1)). Despite the fact that most deforestation has been for new agricultural land, the majority ofthe lands cleared from forests in China are no longer croplands, but fallow or degraded shrublands.Unlike croplands, the origins of these other lands are poorly documented, and thus add consider-able uncertainty to estimates of flux before the 1980s. Nevertheless, carbon emissions from China seem to have decreased since the 1960s to nearly zero at present. In contrast, emissions of car-bon from tropical Asia were higher in the 1990s than that at any time in the past.  相似文献   

6.
The study reports lead concentrations and lead and strontium stable-isotope ratios in mandibular molars of roe deer from three different areas in western Germany. Lead concentrations in third molars ranged between 0.23 and 36.61 μg/g (dry weight). Comparing lead concentrations in first molars and third molars in a group of ca. 1.5- or ca. 2.5-year-old individuals from the same area revealed an effect of tooth age on tooth lead content. The higher lead concentrations in the first molars were attributed to the longer period of lead accumulation by the dentin of these teeth compared with the later-forming third molars. Differences in lead isotopic signatures of the teeth were observed between the three areas, presumably reflecting variation in exposure to different sources of environmental lead. We also found marked variation in the 87Sr/86Sr isotope ratios of the teeth, with only a small overlap in values between two of the areas. Strontium isotope analysis alone or in combination with lead isotope analyses can be a useful means of assessing the provenance of deer teeth of unknown geographical origin.  相似文献   

7.
Environmental toxicants are ubiquitous,and many are known to cause harmful health effects.However,much of what we know or think we know concerning the targets and long-term effects of exposure to environmental stressors is sadly lacking.Toxicant exposure may have health effects that are currently mischaracterized or at least mechanistically incompletely understood.While much of the recent excitement about stem cells(SCs)focuses on their potential as therapeutic agents,they also offer a valuable resource to give us insight into the mechanisms and risks of toxicant effects.Not only as a response to the increasing ethical pressure to reduce animal testing,SC studies allow us valuable insight into the true effects of human exposure to environmental stressors under controlled conditions.We present a review of the history of publications on the effects of environmental stressors on SCs,followed by a consolidation of the literature over the past five years on a subset of key environmental stressors of importance to human health and their effects on both embryonic and tissue SCs.The review will make constructive suggestions as to areas of toxicant research where further studies are needed,as well as making indications of the potential utility for advancing knowledge and directing research on environmental toxicology.  相似文献   

8.
 Aims Desertification results in ecological and biological diminution of the earth, and can happen naturally or cause by anthropogenic activities. This process especially affects arid and semi-arid regions, such as the Isfahan region, where the spread of desertification is reaching critical proportions. The aim of this study is to use remotely sensed data to review the trend of desertification in the northern of Isfahan, Iran. Methods Multi-temporal images were employed to evaluate the trend of desertification, specifically the TM and ETM+ data of September, 1990 and September, 2001. Geometric and radiometric corrections were applied to each image prior to image processing and supervised classification, and vegetation indices were applied to produce a land use map of each image in nine classes. The land use classification s in the two map images were compared and changes between land use classes were detected over the 11 year period using a fuzzy and post-classification technique. Important findings The maps and their comparison with false color composite images showed the differences efficiently. With the fuzzy and post-classification method the land use changes were sited on the map. Fuzzy confirmed 53% changed area and 47% unchanged areas in the study region. The results verify the desertification expansion in the study areas. Because of poor land management, agricultural lands converted to desert and abandoned areas, and some marginal pasture lands had to be changed to agricultural land which are desertification spreading according to United Nations Conference on Desertification (UNCOD). Also farmland and pastures have been converted to urban and industrial areas, and the rangelands have been spoiled due to opencast mine excavations. With the mine margins eroding as well as their debris accumulating on the pasture lands, desertification has become worse. Three areas of less-elevated mountains have remained unchanged. This study confirmed that the anthropogenic activities accelerated the desertification process and severely endangered the remaining areas.  相似文献   

9.
Pore water and solid phase distributions of C, N, P and Si in sediments of the Arctic Ocean (Svalbard area) have been investigated. Concentrations of organic carbon (Corg) in the solid phase of the sediment varied from 1.3 to 2.8% (mean 1.9%), with highest concentrations found at shallow stations south/southwest of Svalbard. Relatively low concentrations were obtained at the deeper stations north/northeast of Svalbard. Atomic carbon to nitrogen ratios in the surface sediment ranged from below 8 to above 10. For some stations, high C/N ratios together with high concentrations of Corg suggest that sedimentary organic matter is mainly of terrigenous origin and not from overall biological activity in the water column. Organic matter reactivity (defined as the total sediment oxygen consumption rate normalized to the organic carbon content of the surface sediment) correlated with water depth at all investigated stations. However, the stations could be divided into two separate groups with different reactivity characteristics, representing the two most dominant hydrographic regimes: the region west of Svalbard mainly influenced by the West Spitsbergen Current, and the area east of Svalbard where Arctic polar water set the environmental conditions. Decreasing sediment reactivity with water depth was confirmed by the partitioning between organic and inorganic carbon of the surface sediment. The ratio between organic and inorganic carbon at the sediment-water interface decreased exponentially with water depth: from indefinite values at shallow stations in the central Barents Sea, to approximately 1 at deep stations north of Svalbard. At stations east of Svalbard there was an inverse linear correlation between the organic matter reactivity (as defined above) and concentration of dissolved organic carbon (DOC) in the pore water. The more reactive the sediment, the less DOC existed in the pore water and the more total carbonate (Ct or ΣCO2) was present. This observation suggests that DOC produced in reactive sediments is easily metabolizable to CO2. Sediment accumulation rates of opaline silica ranged from 0.35 to 5.7 μmol SiO2 m−2d−1 (mean 1.3 μmol SiO2 m−2d−1), i.e. almost 300 times lower than rates previously reported for the Ross Sea, Antarctica. Concentrations of ammonium and nitrate in the pore water at the sediment-water interface were related to organic matter input and water depth. In shallow regions with highly reactive organic matter, a pool of ammonium was present in the pore water, while nitrate conoentrations were low. In areas where less reactive organic matter was deposited at the sediment surface, the deeper zone of nitrification caused a build-up of nitrate in the pore water while ammonium was almost depleted. Nitrate penetrated from 1.8 to ≥ 5.8 cm into the investigated sediments. Significantly higher concentrations of “total” dissolved nitrogen (defined as the sum of NO3, NO2, NH4 and urea) in sediment pore water were found west compared to east of Svalbard. The differences in organic matter reactivity, as well as in pore water distribution patterns of “total” dissolved nitrogen between the two areas, probably reflect hydrographic factors (such as ice coverage and production/import of particulate organic material) related to the dominant water mass (Atlantic or Arctic Polar) in each of the two areas. The data presented were collected during the European “Polarstern” Study (Arctic EPOS) sponsored by the European Science Foundation  相似文献   

10.
Multisensor data fusion (MDF) is an emerging technology to fuse data from multiple sensors in order to make a more accurate estimation of the environment through measurement and detection. Applications of MDF cross a wide spectrum in military and civilian areas. With the rapid evolution of computers and the proliferation of micro-mechanical/electrical systems sensors, the utilization of MDF is being popularized in research and applications. This paper focuses on application of MDF for high quality data analysis and processing in measurement and instrumentation. A practical, general data fusion scheme was established on the basis of feature extraction and merge of data from multiple sensors. This scheme integrates artificial neural networks for high performance pattern recognition. A number of successful applications in areas of NDI (Non-Destructive Inspection) corrosion detection, food quality and safety characterization, and precision agriculture are described and discussed in order to motivate new applications in these or other areas. This paper gives an overall picture of using the MDF method to increase the accuracy of data analysis and processing in measurement and instrumentation in different areas of applications.  相似文献   

11.
A simple and rapid technique is outlined for 20-40 mUm sectioning of epoxy embedded tissue, removal of areas of interest from the thick sections, resectiening of the selected areas for ultrastructural use. Use of the embeddmg mixture desaibed by Kushida in 1971- makes possible thick sectioning without fracturing. Mounting on glass slides with immersion oil for light microscopic observation facilitates later demouutng for isolation of selected areas. Identification of specific areas of interest is aided by an osmium intensifier stain, p-phenylenediamine. The method is useful for both localizing specific tissue areas and for systematic sampling at precise intervals.  相似文献   

12.
A O Oduntan 《Acta anatomica》1992,143(3):178-181
Light- and electron-microscopical techniques were used to study the structure of the inferior conjunctiva of monkeys including the third eyelid (nictitating membrane). The cell layers of the conjunctival epithelium were 8-10 at the margin, 6-8 near the limbus and 2-4 in other areas except in the third eyelid where there were 1-4 layers. The epithelium was 90-100 microns thick at the margin and 35-40 microns at the other areas except at the third eyelid where it was 10-45 microns thick; near the limbus it was 55-60 microns thick. The morphological differences between the epithelia of the various areas of the inferior conjunctiva are highlighted. The similarities and differences between the human and monkey inferior conjunctivas are discussed.  相似文献   

13.
An improved method is described in which tissue areas can be initially identified in thick sections by light microscopy and isolated for subsequent ultrathin sections and observation by electron microscopy. This is achieved by embedding in hard Epon which can be sectioned at 25-150 μm on a sliding microtome after softening the blockface by applying a 60-70 C tacking iron to its surface immediately before each section is taken. The thick sections are then mounted on plastic slides to enable light microscopic selection of areas to be observed by electron microscopy. The selected areas are remounted on faced Epon blanks and resectioned at less than 50 nm. This technique makes it possible to obtain thick sections while maintaining an Epon hard enough for good serial ultrathin sections.  相似文献   

14.
The aim of this study was to utilize magnetic resonance imaging (MRI) to image structural heterogeneity and mass transport inside a biofilm which was too thick for photon based imaging. MRI was used to map water diffusion and image the transport of the paramagnetically tagged macromolecule, Gd-DTPA, inside a 2.5 mm thick cyanobacterial biofilm. The structural heterogeneity of the biofilm was imaged at resolutions down to 22 × 22 μm, enabling the impact of biofilm architecture on the mass transport of both water and Gd-DTPA to be investigated. Higher density areas of the biofilm correlated with areas exhibiting lower relative water diffusion coefficients and slower transport of Gd-DTPA, highlighting the impact of biofilm structure on mass transport phenomena. This approach has potential for shedding light on heterogeneous mass transport of a range of molecular mass molecules in biofilms.  相似文献   

15.
Four areas containing different cell morphologies were mapped on Porphyra blades and five different cell types (i.e. tapered with long extensions, large and vacuolated, vegetative and dividing, and reproductive: males and females) were identified in them. Tissues from these areas were dissociated, and protoplasts and single cells were isolated from the dissociated tissue of each distinct region. Regeneration rates of the isolated cells and protoplasts (isolates) varied depending on their morphological type. Regeneration rates were lowest in cultured isolates from the area just above the holdfast (ca. 1 %) and increased gradually to over 80% in isolates from areas of vegetative and reproductive regions away from the holdfast. Four distinct morphological patterns were observed among the regenerating plants. Cells isolated from vegetative areas developed into leafy plants while in liquid culture, and into calli when grown on solid medium. Isolates from reproductive areas developed into either a long thin or short thick filamentous plant. Those from ripe patches of carposporangia developed into thin conchocelis filaments, while isolates from non-differentiated cells bordering the ripe reproductive patches developed into thick filaments resembling the morphology of conchosporangial branches. The blade of Porphyra appears simple as it consists of a single cell layer; however, it is complex both morphologically and physiologically.  相似文献   

16.
In order to maintain branch strength and a confluent outer membrane, trepostome bryozoans had to maintain a continuous colony surface without any structural gaps. This put great constructional demands on colonies with relatively thick exozones to fill the exozonal space while preserving a suitable autozooecial spacing for colony-wide feeding currents. This situation was magnified in a giant colony of the trepostome Tabulipora from the Early Permian Kim Fjelde Fm. in eastern North Greenland. This single branch colony fragment had a diameter of 37.5 mm. A block was cut out of the 8- mm thick exozone, and 20 serial tangential peels were made at varying distances from the endozone. Exilazooecial and autozooecial chamber cross-sectional area, packing, spacing, and wall thickness were measured in the maculae and intermacular areas. Results indicate that, in this colony, volumetric space in the exozone was occupied by budding new exilazooecia in the maculae and by exozonal budding: budding of new exilazooecia in the intermacular areas that transform into autozooecia. Exilazooecia played a dominantly space-filling role in the maculae as well as helped to maintain regular spacing of autozooecia in the intermacular areas.  相似文献   

17.
The nerves and nerve endings in the skin of tropical cattle were studied using histological and histochemical techniques. Many nerve trunks and fibres were present in the reticular and papillary dermis in both hairy and non-hairy skin sites. In non-hairy skin locations such as the muzzle and lower lip, encapsulated endings akin to Krause and Ruffini end bulbs, which arise from myelinated nerve trunks situated lower down the dermis were observed at the upper papillary layer level. Some fibre trunks seen at this level extended upwards to terminate within dermal papillae as bulb-shaped longitudinally lamellated Pacinian-type endings, while other onion-shaped lamellated nerve structures were located either within dermal papillae or near the dermo-epidermal area. Intraepidermal free-ending nerve fibres, appearing non-myelinated were observed in areas with thick epidermis. Intraepidermal free-ending nerve fibres, appearing non-myelinated were observed in areas with thick epidermis. On hairy skin sites, however, organized nerve endings or intraepidermal nerve endings were not readily identifiable.  相似文献   

18.
SYNOPSIS. Oocysts of Eimeria nieschulzi from the laboratory rat, Rattus, norvegicus , were studied by scanning and transmission electron microscopy. Oocysts had a rough outer wall with apparent random depressions. The oocyst wall is composed of 2 layers: an osmiophilic outer layer consisting of a rough external and smooth internal surface, and a relatively thick, electron-lucent inner layer. The outer layer is composed of a dense, coarsely granular matrix. The inner layer consists of homogeneous fine granular material interspersed with coarse osmiophilic granules and contains one closely applied membrane on the outermost surface. Several raised lenticular areas are seen on the coarse outer surface of the inner layer. These layers are 102 (75–128) and 176 (135–204) nm thick, respectively.
The sporocyst wall is thin, consisting of 3 to 4 unit membranes, and measures 27 (18–34) nm thick.  相似文献   

19.
Observation of semi-thin and ultrathin sections performed in the gills of green crabs (Carcinus maenas) kept in 100% and in dilute 30% sea water respectively reveals marked differences between the six anterior and the three posterior pairs of gills. The anterior gill lamellae are almost entirely lined by a thin pavement epithelium (0.9 to 3 mum thick) which does not undergo any noticeable change when crabs are acclimated from full to dilute sea water. This supports the view it is chiefly involved in the respiratory function. In addition to the pavement epithelium, the posterior gills exhibit small areas corresponding to a thick prismatic epithelium (10 mum) the ultrastructure of which is similar to that of most of the so-called 'salt transporting epithelia'. When submitted to reduced external salinity, this epithelium undergoes structural changes consisting of elaboration of an extensive apical plasma membrane infolding system, enlargement of the subcuticular compartment and close association of mitochondria with basolateral membrane infoldings. Pilaster cells exhibit ultrastructural features of either thin (respiratory) or thick (salt transporting) epithelial differentiation according to their localization within the gill. Their peculiar organization suggests they ensure, in addition, mechanical reinforcement of the gill lamellae against blood hydrostatic pressure. The fact that salt-transporting epithelium areas do not exceed, at most, 30% of the total lamellar surface is probably related to the weak osmoregulatory capabilities of the shore crab.  相似文献   

20.
The development of the basement membrane and collagen fibrils below placodes, including the corneal region of the ectoderm, lens epithelium, nasal plate, and auditory vesicle in anuran larvae was observed by transmission electron microscopy and compared with that in nonplacodal regions such as the epidermis, neural tube, and optic vesicle. In the corneal region the lamina densa becomes thick concomitantly with the development of the connecting apparatuses such as hemidesmosomes and anchoring fibrils. The collagen fibrils increase in number and form a multilayered structure, showing similar morphology to the connective tissues below the epidermis. These two areas, i.e., the corneal region and epidermis, possess much collagenous connective tissue below them. On the other hand, the neural tube and ophthalmic vesicle that originated from the neural tube each have a thin lamina densa and a small number of underlying collagen fibrils. The lamina densa does not thicken and the number of collagen fibrils do not significantly increase during development. These two areas possess little extracellular matrix. The nasal plate and auditory vesicle show intermediate characteristics between the epidermis-type and the neural tube-type areas. In these areas, the lamina densa becomes thick and hemidesmosomes and anchoring fibrils develop. The number of collagen fibrils increases during development, but does not show an orderly arrangement; rather, they are randomly distributed. It is thought that the difference in the arrangement of collagen fibrils in different tissues is due to differences in the extracellular matrix around the collagen fibrils. Placodal epithelia have the same origin as epidermis, but during development their morphological characteristics differ and they are not associated with the pattern of extracellular matrix with characteristics of epidermal and corneal multilayered collagen fibril areas.  相似文献   

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