Tree scale distributed multipoint measuring system of photosynthetically active radiation

L Palva*, T Markkanen, E Siivola, E Garam, M Linnavuo, Saulius Nevas, F Manoochehri, S Palmroth, K Rajala, H Ruotoistenmaki, T Vuorivirta, I. Seppala, T Vesala, Pertti Hari, R Sepponen

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review


A tree scale distributed multipoint measuring system of photosynthetically active radiation (PAR) has been designed. The system is divided into a central unit, measuring units and sensor-amplifiers. Measurements can be carried out with a maximum number of 32 measuring units each comprising 24 sensor-amplifiers. The feasibility of the system has been demonstrated with measurements within a Scots pine canopy using a 12 m telescopic mast with horizontal cross-booms. Two sensor arrays of 4 m in length comprising about 40 sensors were divided into 10-sensor sub-arrays of 1, 2, and 4 m in length. The simultaneously measured PAR averages over the sub-arrays differed considerably from the 4 m reference arrays. The maximum difference was 100% in the case of the 1 m sub-arrays, 80% in the case of the 2 m sub-arrays and 54% in the case of the 4 m sub-arrays. When averaged over the 6 h measuring period around noon, the respective maximum differences were 27, 15 and 3%. (C) 2001 Elsevier Science B.V. All rights reserved.

Original languageEnglish
Pages (from-to)71-80
Number of pages10
JournalAgricultural and Forest Meteorology
Issue number1
Publication statusPublished - 6 Jan 2001
MoE publication typeA1 Journal article-refereed


  • multipoint measuring system
  • photosynthetically active radiation
  • sensor
  • photodiode
  • data acquisition
  • Scots pine

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