Mika Sulkava

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— Assessment of model properties with respect to data is important for reliable analysis of data. After training, Self-Organizing Map (SOM) can be assessed, for instance, with respect to its quantiza-tion or its topology preservation properties with one-number summaries. In this paper, we present a decomposition of the SOM distortion measure for measuring(More)
The timing and rate of xylem formation during the growing season are key processes in determining the amount and properties of wood produced. Despite the basic nature of the process, our present knowledge concerning xylem formation is surprisingly fragmentary. It has proven difficult to distinguish between the changes caused by xylem formation and those(More)
— Understanding the nutritional states and profiles of tree species is important for monitoring the well-being of forests. Data from foliar surveys are available, but there is still need to better understand the underlying nutritional mechanisms in trees. In this paper, the nutrient concentrations of pine and spruce needles in Finland between 1987–2000 are(More)
This paper introduces the use of nutrition profiles as a first step in the development of a concept that is suitable for evaluating forest nutrition on the basis of large-scale foliar surveys. Nutrition profiles of a tree or stand were defined as the nutrient status, which accounts for all element concentrations, contents and interactions between two or(More)
Dendrometers are devices, which measure continuously the stem radius of a tree. In this work, we studied the use of cumulative sum (CUSUM) charts for automatically and, thus, objectively determining the onset and cessation dates of radial increase based on dendrometer data. We used data measured in two forest stands in southern Finland to demonstrate the(More)