Object identification and characterization with hyperspectral imagery to identify structure and function of Natura 2000 habitats

Habitat monitoring of designated areas under the EU Habitats Directive requires every 6 years information on area, range, structure and function for the protected (Annex I) habitat types. First results from studies on heathland areas in Belgium and the Netherlands show that hyperspectral imagery can be an important source of information to assist the evaluation of the habitat conservation status. Hyperspectral imagery can provide continuous maps of habitat quality indicators (e.g., life forms or structure types, management activities, grass, shrub and tree encroachment) at the pixel level. At the same time, terrain managers, nature conservation agencies and national authorities responsible for the reporting to the EU are not directly interested in pixels, but rather in information at the level of vegetation patches, groups of patches or the protected site as a whole. Such local level information is needed for management purposes, e.g., exact location of patches of habitat types and the sizes and quality of these patches within a protected site. Site complexity determines not only the classification success of remote sensing imagery, but influences also the results of aggregation of information from the pixel to the site level. For all these reasons, it is important to identify and characterize the vegetation patches. This paper focuses on the use of segmentation techniques to identify relevant vegetation patches in combination with spectral mixture analysis of hyperspectral imagery from the Airborne Hyperspectral Scanner (AHS). Comparison with traditional vegetation maps shows that the habitat or vegetation patches can be identified by segmentation of hyperspectral imagery. This paper shows that spectral mixture analysis in combination with segmentation techniques on hyperspectral imagery can provide useful information on processes such as grass encroachment that determine the conservation status of Natura 2000 heathland areas to a large extent. A limitation is that both advanced remote sensing approaches and traditional field based vegetation surveys seem to cause over and underestimations of grass encroachment for specific categories, but the first provides a better basis for monitoring if specific species are not directly considered

Rhizoctonia solani as a component in the bottom rot complex of glasshouse lettuce

The basal parts of maturing glasshouse lettuce can be attacked by several soil fungi, which cause bottom rot. Until recently quintozene was generally applied against this disease complex. The study of the causal fungi - especially Rhizoctonia solani - and their control was undertaken in view of the need for quintozene replacing fungicides.A survey revealed that Botrytis cinerea was the most frequently observed pathogen, especially in winter crops. The incidence of Sclerotinia minor, Sclerotinia sclerotiorum, Pythium spp. and Rhizoctonia solani was much lower. These fungi were more prevalent in autumn and late spring crops than in winter crops. Many of the attacked heads were infected by more than one pathogen. On an average disease severity caused by R. solani was the highest and by Pythium spp. the lowest. Trials showed that on untreated areas the average loss of lettuce heads of export quality class caused by bottom rot was 17 per cent, whereas on plots treated with appropriate fungicides this loss was 5 per cent.For the detection of R. solani in the soil a relatively simple and fast paper disk bait method was improved and standardized. In addition a time saving quantitative technique was developed by plating out sieved soil clumps on a selective medium.The paper disk method proved that the horizontal dispersion of R. solani propagules in the soil of lettuce glasshouses is not random, but clustered. This pattern could be characterized by the negative binomial distribution. Propagules were found throughout the whole ploughlayer but the inoculum density decreased remarkly as the depth of sampling increased.The average inoculum density on 62 holdings was low: 0.6 propagule of R. solani per 100 g of soil. The individual glasshouse values were related to the period of sampling, soil disinfestation and the use of quintozene.During winter crops the inoculum density remained low, in spring time the values were higher, especially at the end of the cropping period. An attack of R. solani in most lettuce crops can be characterized as a "simple interest disease" sensu Vanderplank. This implies that the reduction of the initial inoculum in the soil is the most important factor in the control strategy.On a log-log scale there appeared to exist a linear relationship between the initial inoculum density of R. solani determined with the paper disk method and the infections of lettuce heads. This indicates that this method of detection has a disease forecasting value. A tentative threshold value of initial inoculum density of 0.2-0.5 propagules per 100 g of soil was established, if the value is less than this no economic loss need be expected.Most of the R. solani isolates from lettuce leaves that were examined showed that the minimum temperature required for infection was at least 9°C.The incubation period at this temperature was from 11 - 15 days, whereas at 20°C less then 3 days. The linear extension of the lesions on infected leaves was at 20°C about 8 mm per 24 hour. These data confirm the observations that on lettuce, ,cropped during winter months with a low temperature regime, the attack is minimal, and that in late spring crops with periods of high temperature the attack can progress very quickly. Isolates were obtained with specific low temperature requirements from a glasshouse with a winter crop which had been severely attacked.Rhizoctonia solani in lettuce appeared to be hygrophylic, but free water is not necessary for the initiating of the infection process.All seventeen glasshouse crops tested, in a host range experiment, were attacked by R. solani.In isolates obtained from diseased heads, three out of four known European anastomis groups of R. solani occurred. The other, anastomis group 3 ("potato group") was only found once among isolates from soil.The dicarboximides, iprodione and vinclozolin, have proved in field and in vitro experiments, to be good replacements for quintozene to control attacks of B. cinerea, R. solani and Sclerotinia spp. The infection by Pythium spp. appears to increase when quintozene and dicarboximides are used. Further research is necessary in order to establish whether the chemical control of Pythium spp. will be required economically.Soil disinfestation with methyl bromide caused a large reduction of the inoculum density of R. solaniFinally it has been discussed that the control of bottom rot should be optimized by integration of the culture of the more tolerant "upright" cultivars, the management of appropriate cultural measures and a reduced dose of fungicides

The effect of depth on the morphology, bacterial clearance, and respiration of the mediterranean sponge chondrosia reniformis (Nardo, 1847)

To support the successful application of sponges for water purification and collagen production, we evaluated the effect of depth on sponge morphology, growth, physiology, and functioning. Specimens of Eastern Mediterranean populations of the sponge Chondrosia reniformis (Nardo, 1847) (Demospongiae, Chondrosiida, Chondrosiidae) were reciprocally transplanted between 5 and 20 m depth within the KaŠ-Kekova Marine Reserve Area. Control sponges at 5 m had fewer but larger oscula than their conspecifics at 20 m, and a significant inverse relationship between the osculum density and size was found in C. reniformis specimens growing along a natural depth gradient. Sponges transplanted from 20 to 5 m altered their morphology to match the 5 m control sponges, producing fewer but larger oscula, whereas explants transplanted from 5 to 20 m did not show a reciprocal morphological plasticity. Despite the changes in morphology, the clearance, respiration, and growth rates were comparable among all the experimental groups. This indicates that depth-induced morphological changes do not affect the overall performance of the sponges. Hence, the potential for the growth and bioremediation of C. reniformis in mariculture is not likely to change with varying culture depth. The collagen content, however, was higher in shallow water C. reniformis compared to deeper-growing sponges, which requires further study to optimize collagen production.This research was executed within the Connected Circularity program, financed by strategic funding of Wageningen University and Research and the knowledge base of the Ministry of Agriculture, Nature, and FoodQuality (KB40), and was part of the ERA-NET project Biogenink (project 4195), funded by the EuropeanCommission in conjunction with the Dutch Science Foundation NWO and the Portuguese Foundation for Science and Technology (FCT) (project M-ERA-NET-2/0022/2016)

Fean wetter buorkje II : Samenvattende rapportage praktijkproeven hoger zomerpeil Fries Veenweidegebied 2007-2008

De provincie Fryslân en Wetterskip Fryslân zoeken naar een vorm van peilbeheer die de bodemdaling in het Friese veenweidegebied vertraagt, maar een sterke landbouw niet in de weg staat. De oplossing wordt gezocht in hoger zomerpeil. Daarbij is ’s zomers, wanneer vanwege de lagere grondwaterstanden en de hogere temperaturen 90% van de bodemdaling plaatsvindt, de drooglegging 60-70 cm, terwijl die ‘s winters 90 cm blijft

Expressions 2021

https://openspace.dmacc.edu/expressions/1037/thumbnail.jp