Mika Sulkava

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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)
— 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)
— 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)
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)
Possible changes of the growing season of trees would have significant consequences on forest production. Predicting the onset of tree growth on the basis of climate records can be used for estimating the magnitude of such changes. Conventional methods for estimating the onset of tree growth use cumulative temperature sums. These estimates, however, are(More)