Browsing by Subject "Methodologie"

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Testing vegetation flammability : examining seasonal and local differences in six mediterranean tree species
(2016) Kauf, Zorica; Fangmeier, Andreas
Fire is an important factor controlling vegetation structure, with 40% of terrestrial ecosystems owing their distribution and ecological properties to the accompanying fire regime. In recent decades climate and land use change led to shifts in fire regimes rendering ecosystems more vulnerable to fire. The greatest effects of these changes are expected in the Mediterranean regions. Vegetation is the only factor affecting fire regime which can be directly managed. Promotion of less flammable species is considered to be a valid management option for reducing negative consequences of wildland fires, but reliable information on vegetation flammability and its fluctuations is still lacking. This study strived to bring new insight on the relationship between environmental conditions, fluctuations of morphological characteristics, physiological activity and measured flammability related parameters of Mediterranean tree species. Only a small part of the field study data is included in the final thesis. The field study was conducted from May to October 2010 in the Mediterranean biogeographic region of Croatia, where three sampling locations were positioned along a climate gradient. Selected species included: Aleppo pine (Pinus halepensis Mill.), Holm oak (Quercus ilex L.), olive (Olea europaea L.), carob (Ceratonia siliqua L.), pomegranate (Punica granatum L.), and strawberry tree (Arbutus unedo L.). If possible, all the species were sampled on all the locations during each sampling event. Presented results include: results of the leaf litter flammability method pretesting, regular measurements on leaf litter samples, and monthly measurements on fresh leaf samples. P. granatum samples were not included in the method pretesting, instead laurel (Laurus nobilis L.), mastic (Pistacia lentiscus L.) and Japanese mock orange (Pittosporum tobira Thunb.) were sampled in order to increase the diversity of the materials included. All measured traits of leaf litter) are reported and the relationships between them examined. For fresh leaves only ignition related traits and moisture content results are presented, the relationship between them is examined, and potential effects of the Keetch-Byram drought index on these parameters are explored. Initially, the application of already established epiradiator based methods was intended. Nevertheless, method pretesting identified several flaws of established methods. It revealed that an epiradiator is not a stabile heat source as previously thought, recognising a need for monitoring and stabilizing epiradiator temperature to ensure similar heat exposure at the beginning of each tests. Furthermore, pretesting results demonstrated that materials that rarely flame under certain testing conditions can readily flame if testing conditions are slightly altered, thus challenging the presumption that low ignition frequency always corresponds to low fire danger (flammability) – a basic presumption of the vegetation flammability tests. Results of leaf litter flammability testing showed that properties of the leaf litter particles significantly change within the fire season, and indicated that species specific weathering and decomposition could play an important role in these changes. They demonstrated that a change in a single leaf trait can have opposite effects on different flammability parameters, and that these relationships are dependent on the incoming heat flux. Results of fresh leaves testing identified phenological changes as important factor governing fluctuation of moisture content and ignition related parameters, and showed that the relationship between drought indices and moisture content is not limited to shallow rooting species. They challenged the presumption that increasing leaf thickness is related to “fire retardance” – a relationship found if samples are tested outside their natural moisture content range. Instead, this study, in which fresh leaves were tested within their natural moisture content range, implies that higher sclerophylly is related to higher ignition frequency, indicating an opposite trend and confirming the importance of moisture content as one of the most important factors governing fire behaviour of the materials. All the gathered data indicated that, O. europaea, Q. ilex and P. halepensis exhibit higher tendency to ignite than C. siliqua and P. granatum; A. unedo showed high variation in ignition related parameters. Nevertheless, ignition related parameters reveal only a part of the information on fire behaviour of the material. Overall results demonstrated that the experimental setup can have tremendous impacts on the results of flammability tests, thus data interpretation should be done with caution. Furthermore, instead of attributing single flammability scores based on all measured parameters, interpretation of test results in relation to their influence on fire behaviour is advocated.
The potential of smartphone apps to collect self-recorded data in agricultural households : a study on time-use in Zambia
(2019) Daum, Thomas; Birner, Regina
Mobile information and communication technologies (ICTs) have spread across the developing world and are used increasingly by smallholder farmers. While the potential of ICTs, such as smartphone applications, to provide new opportunities for agricultural development is widely acknowledged, the potential to use them as research tools has not been explored. This thesis assesses the potential of smartphone applications for the collection of data from agricultural households in developing countries. Can smartphone applications that use visual tools be used for self-recording of data by the respondents themselves where literacy levels are low? Can such smartphone applications that allow for real-time data recording increase the accuracy of the collected data? Answering these questions is important as, so far, data from agricultural households are usually collected using surveys, which are prone to recall biases. This is a problem, as researchers, policymakers and development practitioners need reliable data for their work. Poor data can lead to misguided policy recommendations and actions with adverse effects on vulnerable population groups. This can lead to agricultural development trajectories that are socially unequal and unsustainable. To assess the potential of smartphone apps to collect self-recorded data, a smartphone application called Timetracker was developed as part of this thesis. The Timetracker allows study respondents to record data in real time with the help of illustrations. Recording data in real time reduces recall bias, and using pictures ensures that participants with low literacy can use the application. In its current form, the Timetracker can be used to collect data on time-use and nutrition. Collecting reliable data on time-use and nutrition is key for various strands of research. For example, time-use data are needed to calculate labor productivity and analyze how productivity is affected by new technologies. Time-use data can also help reveal gender-based power relations and asymmetries by pointing out unpaid domestic work. Similarly, nutritional data are crucial for various academic fields and debates. For example, nutritional data are needed to explore the factors determining food and nutrition security, to study how farm diversity affects consumption diversity and to monitor food and nutrition policies and programs. This study is based on three main chapters, which reflect the main objectives of the whole thesis: 1) to explore and test whether smartphone applications can be used to collect data from rural households in developing countries focusing on time-use and nutrition data, 2) to assess the accuracy of data collected with smartphone applications vis-à-vis recall-based data collection methods, and 3) to use the data to understand the effects of agricultural mechanization on the intrahousehold allocation of time-use within smallholder farming households in Zambia. The first two chapters have a primarily methodological focus. The last chapter is an empirical study. This thesis concludes that in addition to improving the accuracy of socioeconomic data collection, smartphone applications may open new research pathways, including through the opportunities provided by real-time data collection and by combining self-recorded data with sensor-recorded data, which may open interesting transdisciplinary research pathways. This thesis suggests that there is a large and still untapped potential for using smartphone applications to collect data on complex agricultural systems in the digital age.