Forest health inventory (Sanasilva)

A healthy Norway Spruce

The Sanasilva Inventory has been carried out in its current form since 1985. Its aim is to monitor the health of the Swiss forest using crown and tree parameters as indicators of forest condition.

The size of the systematic sample grid has been changed twice since 1985. From 1985 until 1992 approximately 8,000 trees were assessed on nearly 700 plots placed on a 4x4 km grid. In 1993, 1994 and 1997 approximately 4,000 trees were assessed on a 8x8 km subgrid. In 1995, 1996 and 1998 till 2002 approximately 1100 trees on a 16x16 km subgrid were assessed.

The name of the inventory has changed subsequently with the change in assessment methods. Until 1992 the inventory was called "Forest damage inventory" ("Waldschadensinventur"), in 1993 this was changed to "Forest condition inventory" ("Waldzustandsinventur"). Since 1995 the inventory has been called the "Sanasilva Inventory."

Methods

Every three years (1997, 2000), the Sanasilva-Inventory is carried out on a 8x8 km grid (ca. 170 plots ). In other years the grid is reduced to 16x16 km (49 plots). Each plot consists of two circles with identical center. The outer circle has a radius of 12.62 m (500 m²) and the inner circle has a radius of 7.98 m (200 m²). All trees with a diameter at breast height of at least 12 cm in the inner circle and with a minimum breast height diameter of 36 cm in the outer circle will be assessed. An identical satellite plot has been established 30 m due North of each plot.

The field assessment is carried out in July and August. An inventory crew consists of two persons. One is responsible for the tree assessment and the other for the data entry. Data are collected using the Paravant field-computer and a data entry software called "Tally." Responsibilities are switched from plot to plot. During the inventory on the 8x8 km grid, 10 percent of the plots are assessed by a second team as part of a consistency check.

Main parameters assessed in the SSI

The Sanasilva-Inventory focusses on three groups of indicators for tree condition:

1. Defoliation
   is assessed as the percent defoliation of a tree in comparison to a reference tree of same species and age growing at the same site with maximum foliage, the percentage of this defoliation that cannot be attributed to a known cause, the part of tree crown with above average defoliation, the percentage of defoliated branches and twigs and their location in the tree crown.
2. Discolouration
   is recorded as the distance of the average tree crown colour from a reference crown colour for this species (assessed in hue, value and chroma using Munsell color charts for plants), the percentage and the location of up to two colours different to this reference colour.
3. Increment
   is defined as the change of tree size variables between two or more assessment periods (i.e. diameter at breast height, tree height, tree crown length, average crown width).

In addition to these, following parameters are assessed: identified causes of defoliation, tree crown competition, ocurrence of epiphytes, mistletoe and climbers in the crown.

• For a more detailed description of the assessment method in 1997 see our field manual (PDF, 1.4 MB, in german).
  

Results

Publication

• Brang P. (Red.) 1998: Sanasilva-Bericht 1997. Zustand und Gefährdung des Schweizer Waldes - eine Zwischenbilanz nach 15 Jahren Waldschadenforschung. Ber. Eidgenöss. Forsch.anst. Wald Schnee Landsch. 345: 102 Seiten ISSN: 1016-3166 / ISBN: 3-905620-67-7. Price: CHF 21.--

• You can get it at:
  
• F. Flück-Wirth
  Internationale Buchhandlung
  CH-9053 Teufen, Switzerland
  Phone: +41 (0)71 333 16 87
  Fax: +41 (0)71 333 16 64
  E-mail: flueck-teufen @ dm.krinfo.ch

Contact

• Matthias Dobbertin