Non-Timber Variables in Forest Inventories Dieter R. Pelz

Abstract

The inclusion of non-timber variables in forest inventories is considered important, as demonstrated by the F AO resources assessment. In many forest inventories some environmental variables are considered, such as site or vegetation variables. Others can be derived partially or completely from standard variables. A survey of national forest inventories shows the range and considerable scope of the assessments, often several hundred variables are measured or observed during the inventory. However, the information required from environmental assessments by non-foresters often cannot be met by the standard forest inventories. For a more complete assessment the scope of most inventories has to be expanded to include additional variables. In many cases the design of the inventory has to be changed, as the assessment of non-timber functions and environmental variables requires alternative statistical designs.

3.1.1 Introduction

Forest inventories by definition assess the functions of the forest, their spatial distribution and their temporal development. This implies the assessment of all forest functions.

Traditional forest inventories had the main objective to provide information on timber, its amount and the development over time. Other variables, such as site variables were only observed if they had direct impact on the timber information, for example to assess the productivity of the forest. With a decreasing resource base and increasing pressure on forest lands, nontimber functions are getting more and more attention.

3.1.2 Forest Functions

In many inventories, significant progress has been made to include non-timber functions as well. These non-timber functions are rather important in all forest regions, for tropical and temperate forests, as demonstrated by the forest resources assessment of F AO/ECE. In the Forest Resources Assessment for the temperate regions the country representatives did fill out a questionnaire on the importance of the forest functions in their respective country.

This gives an indication of the relative importance of the various forest functions by country.

Table 1. Forest functions in the EEC region (FAO/ECE 1990).

Importance

Function ^high medium low

Wood production 48 26 26

Protection 12 19 69

Water 8 14 78

Grazing 8 15 77

Hunting 26 52 22

Nature conservation 6 38 ₅₆

Recreation 12 47 41

In 1992 an expert panel discussed in the Nairobi meeting organized by UNEP, ways to include environmental parameters in global forest assessments.

Forests in all regions can provide a variety of different functions, for which information is needed on the local, national and partly even global level.

If we talk about forest functions and their assessment, we have to keep in mind that it will be impossible to measure and observe all functions, the relevant variables and attributes completely. We will have to restrict the inventory to a specific set of variables and attributes. For example, if biodiversity is to be assessed, only tree or shrub level biodiversity can be included, it will be impossible in most cases to observe the entire floristic or even faunistic biodiversity.

Even for the supply function, we find a variety of of minor forest products that could be listed for the temperate forests, they would be difficult to include in a single inventory in a comprehensive way. For example Table 2 shows such an listing.

Table 2. Forest products in temperate forests (partly from FAO/ECE 1990).

wood products/non-wood products

food non food

game cork

mushrooms and truffles aromatic and medicinal plants

berries dyes

hip/briers gum/oil

nuts resin

honey christmas/new year trees

birch sap hides/skins

snails game trophies

milk (sheep, goat) seeds

fish carobs

This list of the forest products is by far not complete, there is a variety of different products, that are of regional importance and not listed here.

Some of the functions have economic importance, some have a market price, others do not. The assessment of all these items pose quite some problems, as they cannot be measured like standard inventory data. With respect to forest assessments, we have to note several problems.

1. Seasonality: some of the functions, variable or attributes can only be observed during specific seasons ( e.g.fruits, partly protection).

2. Area reference: some of the functions relate to sample plots, others to specific small areas, some to large areas, e.g. wind protection will extend far beyond the forest itself.

3. Assessment only indirectly possible during inventory, such as recreational use, which can be assessed from other indicators.

4. Variables are qualitative (e.g.conservation ).

5. Suitability vs. actual use of the function (recreation - a forest might be suitable for recreation, but the actual use depends on the proximity to settlements, accessibilty etc.).

6. Assessment very costly (measuring herbaceous vegetation or faunistic biodiversity).

These are some of the reasons why all forest functions are not regularly assessed during inventories.

Many forest inventories gather a variety of data regularly. For example, in the Swedish NFI more than 200 variables are observed or measured. In Switzerland, a large number of variables collected relate directly to the timber resources, others such as site variables can also be used for environmental assessments. For example, information on soil protection, rock slides and avalanches is recorded, in addition to a number of variables that relate to recreation, other variables relate directly to nontimber functions.

Most variables collected during national forest inventories are timber oriented, but can be used also for environmental assessments as well.

Table 3. Forest Vegetation and Multi-resource information collected by Forest Inventory and Analysis Units in USA. (USFS 1993).

In the U.S. forest resource inventories include multi-resource information, with the emphasis depending on the region, the specific needs and conditions.

Specific aspects of non-timber functions are assessed in many inventories, on the local, regional or national level. For example the inventory of state forests in Illinois/USA included information on wildlife habitat ( den trees for squirrels, tree cavities etc, acorn and nut yields in hardwood forests), providing valuable information for management.

Management inventories in Europe often include an assessment of recreational aspects, number of picnic sites, number of trails etc.

Often, some of the aspects are assessed not in forest inventories, but in special mapping exercises. For example, in some states in Germany, complete mappings are done for biotopes, where rare or endangered living spaces or features are mapped, forest ecosystems, where a variety of site and vegetation variables are mapped in great detail, and forest functions, where the major forest functions, such as recreation, protection, watersheds etc. are mapped for the forest land. The integration of these results with standard forest inventories are difficult.

In most cases, however one has to realize, that the main emphasis of forest inventories is still on the assessment of timber. Even from these traditional inventories a variety of information can be derived for the assessment of forest functions.

In other cases, regular timber inventory data can be combined with auxiliary information to evaluate some aspects of forest functions. As example WULLSCHLEGER (1982) developed an estimation scheme for the Swiss National Forest Inventory. In this scheme, outside factors such as erosion, elevation, accessibility etc., are related to specific functions, such as recreation, protection against avalanches etc. In addition, the sources of attributes are given, such as topographic maps, terrestrial samples, available statistics etc.

Even if this scheme is not complete and applicable in all cases, it provides a good starting point for a more complete assessment of non-timber functions.

In the following some examples are given for the assessment of non-wood goods and services.

3.1.3 Derivation from Standard Inventories

The production of some minor forest products, such as mushrooms, berries, nuts, and game can be estimated from regular forest inventory data, in conjunction with appropriate production functions, giving the yield of acorns for example as function of basal area and age of the stand. Such an approach has been described by PELZ and THOM (1979).

The protection against erosion, avalanches, landslides etc. can be assessed by the attributes slope, vegetation cover, age of the stand, structure and slope distance to the object to be protected.

Biodiversity of plants or ecosystems can be assessed by the composition of the veg­

etation, age, structure, and soil.

Recreation can be partially estimated by attributes such as road density or accessibilty, management system, distance to next settlement, parking spaces, length of hiking trails etc.

The use of the regular forest inventory data requires production functions to allow the estimation from basic data. In some cases these production functions may be available for the region under consideration, in others special studied have to be conducted to derive apprpriate and accurate functions.

3.1.4 Use of Auxiliary Data

For the estimation of other forest functions, or more detailed aspects of functions, additional data will have to be collected from other sources, such as statistics or maps.

These data can be overlaid with the forest inventory data, using GIS. Soil maps, precipitation maps, biotop maps etc. are widely available in many countries, though in many cases not yet in digital form, requiring a large effort to get the map information into GIS.

The supply of minor forest products can be estimated from statistics on exports, sales, hunting etc. or from the amount of permits issed or royalties collected.

The protection function can partially be evaluated by using vegetation maps, soil and geological maps, precipitation maps etc, or 3-D models of the landscape.

For the assessment of the recreation function statistics on tourism could be helpful, or statistics on maintance of hiking trails, giving the length of trails, number of picnic sites etc.