Kuva: (C) Metla/Tarmo Aalto


Needle Trace Method


What is the needle trace method?

The needle trace method (NTM) enables the user to reliably examine the past foliation of conifer trees. The method is based on the examination of the vascular system, needle trace, connecting dwarf shoots and the shoot pith.


The NTM was developed at the Finnish Forest Research Institute's Rovaniemi Research Unit in the late 1980s. Based on an idea initially presented by professor Timo Kurkela, this method enables reliable results to be obtained on the needle age classes and other parameters related to conifer foliage, not only concerning the present, but going back in time hundreds, even thousands of years.


Kuva: (C) Metla/Risto Jalkanen  
The oldest needles die in the autumn. Photo: Risto Jalkanen.  


Pines (Pinus spp.) produce a new needle age class along their branches and along the main stem every growing season. Every autumn the oldest needles die at the average rate of one needle age class. In the long run, pines carry the same number of needle age classes year after year. On average, pines in southern and central Finland have 3-4 and in northern Finland 5-8 green needle age classes. However, the number of needle age classes varies from year to year due to the changing environmental conditions. In summers that are difficult for tree growth, more needles than just those of an oldest age class turn yellow.


A number of methods have been developed for estimating defoliation and the variation in the number of needle age classes on pine. This can be performed with great accuracy if branches are removed from trees for closer examination of the needle age classes. A quicker method for estimating the foliage of living trees is to use binoculars.


A problem with the aforementioned methods is how to obtain long time series of the needle age class variation. One inventory (per year) yields information on only the year in question. Using these methods to obtain even a modest time series takes several years. To solve these problems the NTM was started to develop at the Finnish Forest Research Institute's Rovaniemi Research Unit in 1987.

   Päivitetty:   26.8.2005 / TAal Metla : Tutkimus : Hanke 3294    Palaute Metlan etusivulle
. .