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In Lower Saxony, Germany, research has been conducted in naturally developing strict forest reserves (SFR) for the last five decades. The intention of this study was to examine the overall scientific approach of long-term research in SFR, review the development and the strengths and weaknesses of the research program in Lower Saxony, refine the conceptual model underlying the investigations and point out key lessons for SFR research. Long-term research in SFR follows an observational and explorative approach with the intention to capture the real world complexity of naturally developing forests. We found that two main challenges are typical: guaranteeing target-orientation and preventing subjectively biased data analysis. Because relevant scientific questions are changing in the course of time target- orientation is an intrinsic general problem of longterm research. Subjectively biased data analysis is considered to be a result of inadequate hypothesis building. In Lower Saxony, the basic research idea was to study the main processes of tree demography and the dynamics of forest structure. The measurement protocol, the system of monitoring plots and the turnover of inventories were adapted stepwise to fit current research questions as well as staff and financial resources. As data integrity is reliable, the SFR scheme in Lower Saxony has developed into a functioning long-term program. The need for improvement is seen in scientific and applied impact. A conceptual model of the main demographic processes and structure attributes formed the basis for the measurement protocol and helped to generate a versatile data pool. This initial model was refined (Fig. 3) to serve as a basis for deriving admissible hypothesis and, thus, to prevent subjectively biased data analysis. It is concluded that long-term research in SFR, in combination with one-off comparative approaches, should be strengthened and better use should be made of the collected database. To secure success, it needs a combination of stubbornness to safeguard the program and adaptability to attune to current requirements. [ABSTRACT FROM AUTHOR]

Recent technological developments have finally brought virtual reality (VR) out of the laboratory and into the hands of developers and consumers. However, a number of challenges remain. Virtual travel is one of the most common and universal tasks performed inside virtual environments, yet enabling users to navigate virtual environments is not a trivial challenge--especially if the user is walking. In this article, we initially provide an overview of the numerous virtual travel techniques that have been proposed prior to the commercialization of VR. Then we turn to the mode of travel that is the most difficult to facilitate, that is, walking. The challenge of providing users with natural walking experiences in VR can be divided into two separate, albeit related, challenges: (1) enabling unconstrained walking in virtual worlds that are larger than the tracked physical space and (2) providing users with appropriate multisensory stimuli in response to their interaction with the virtual environment. In regard to the first challenge, we present walking techniques falling into three general categories: repositioning systems, locomotion based on proxy gestures, and redirected walking. With respect to multimodal stimuli, we focus on how to provide three types of information: external sensory information (visual, auditory, and cutaneous), internal sensory information (vestibular and kinesthetic/proprioceptive), and efferent information. Finally, we discuss how the different categories of walking techniques compare and discuss the challenges still facing the research community. [ABSTRACT FROM AUTHOR]