Valuation Survey

Forest Inventory Section

Summaries of Valuation and Reconnaissance Surveys 1926-1950

A substantial number of forest surveys were conducted in Guyana during the second quarter of the 20th Century. These were primarily concerned with the assessment of exploitable timber species within the main accessible forestry belt, but their value is greatly enhanced in that they also recorded a wide range of non-commercial species (many of which are now of interest to forest producers and researchers.

This phase of surveys used a modified version of the method used by Brandis in the teak forests of Burma at the end of the last century (20th Century). Transects of 20 – 30 metres were laid out in a systematic manner without stratification, usually based around access roads and navigable stretches of the country’s many rivers and creeks. Sampling intensities were generally below 2.5%: the reconnaissance surveys are distinguished by their lower sampling intensities. Tree diameters were measured with calipers by 4 inch (10cm) class, though most of the summary information available only provides frequencies by species for all trees > 16 inches diameter (c. 41 cm), without individual diameter classes.

A significant part of the interior was covered by these exercises, particularly when one considers the additional difficulties involved in field work in those days.

D.B. Fanshawe summarised the tree frequency information from these valuation and reconnaissance surveys by seven main regions, presenting the resulting figures in Principal Timbers (1954). These figure (popularly called “Fanshawe’s Tables”) have been a valued source of information for forestry companies, since they provide estimates of the frequencies of commercial sizes of important species by region. (This seminal work has just been re-printed by GFC; copies are available from Head Office at a price of G$1000 (c. US$6)).

Though tree frequency information for the individual survey exercises was assembled in 1949, it appears that few copies of the resulting report were ever produced and the information was not widely available in this form. It is now reproduced here in electronic format, along with an index map.

Presenting the results by area offers obvious advantages over the regional figures, which (as Fanshawe put it) are "averages of averages". Also to note is that the main forest concession boundaries are included in the index map to facilitate the pin-pointing of surveys relevant to individual forest concession holders. These concession boundaries must be considered approximate, since the small scale of the map does not allow them to precisely match their detailed legal descriptions.

Although this forest survey information is still of great value to forest managers and researchers alike, its limitations must be recognized:

	The age of the information means that it cannot be considered fully representative for areas which have been logged or subject to other human use since the survey was conducted. Moreover some areas may have been significantly affected by natural disturbances such as fire and drought over this period;
	Although the Forest Department has always employed the best tree identification specialists available, there is some variation in the use and precision of common tree names. One common name often corresponds with more than one currently recognized scientific species (see table in downloadable file). An initial attempt has been made to cross-reference the common names used in these surveys with the appropriate botanical taxa, but this must be seen as an approximation;
	None of the original raw data is believed to be available for these surveys: therefore it is not possible to calculate sampling errors on the estimates given;
	Little information is available on the proportions of different forest types sampled during the surveys. It is therefore not possible to determine to what extent the frequency estimates are weighted towards particular types. The dependence on rivers and creeks for access (e.g. in the North West surveys) may tend to bias some estimates in favor of riverine forest types.

In spite of these limitations, the information provides valuable information on the presence and approximate frequencies of many tree species within and around the areas surveyed. Moreover, the information is likely to still be accurate for those areas that have not been significantly exploited or otherwise disturbed since the surveys were conducted.

In conclusion, for the purposes of forest management, the summaries provide useful baseline information, but this alone will not be adequate they must be supplemented by:

	more recent surveys,
	information on the main vegetation types,
	details of past logging activities and other disturbances

Where necessary these must be verified by new assessments (e.g. low-intensity ground exercises).

For research purposes, there is wide scope for examining the distribution and density of individual species and/or species groups of interest across the range of areas surveyed. This information can also be examined in relation to other ecological, environmental, social or economic data.

The original reports on most these surveys are available in GFC, though maps are only available for a limited number of these.

The tables and the map

An index map to the locations of the Valuation/Reconnaissance Surveys is provided. The number of each coloured survey area corresponding with the field of the same number in the down-loadable Excel file.

Two worksheets are contained in this file; these are selected using the two labeled tabs at the base of the worksheet.

The worksheets contain the same information, but the tree frequencies are expressed in two commonly used metric and imperial measures, respectively, i.e.

a) Mean number of stems above 16 inches (c. 41cm) diameter per 100 hectares (=1 square km)

b) Mean number of stems above 16 inches (c. 41 cm) diameter per 1000 acres

The letter “p” in the table notes that the species was present within the area, but that no large numbers were encountered within the transects of sufficient size to be recorded.

To get a summary table for each area, simply click on it on the map. The figures in these tables are expressed in the metric format, i.e. stems greater than 16 inches per 100 hectares (1 square km).

In each of these tables, the species are presented in order of frequency, i.e. the most frequent species comes at the top of the list.

Foresters may enjoy testing their knowledge of which species are most common in each survey area - make your prediction then just click on the area to find out what the survey found!

This is the first installment of Forest Resource Information being compiled by the GFC’s Forest Inventory Section. Please check this page again for down-loads of other (more recent) geo-referenced forest inventory data as they are published.

[ Home ] [ Up ] [Email Logon]

This page requires the use of Macromedia Flash Plug-in v7.0 for effects/graphics and Adobe Acrobat Reader to view documents. Click the icons to the download the software. This site is best viewed with 800 x 600 or higher resolution.