Caracterização e Avaliação da Flora e Vegetação no
Caracterização e Avaliação da Flora e Vegetação no
Caracterização e Avaliação da Flora e Vegetação no
Create successful ePaper yourself
Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.
1 Objectives<br />
VIII Assessment of Ground Vegetation 5<br />
Within the framework of intensive monitoring activities at Level II, vegetation assessment is<br />
important for two different reasons. Firstly, vegetation is a major component of forest ecosystems.<br />
Vegetation layers contain a large part of total forest biological diversity. They play a<br />
direct role in water or nutrient cycling, and strongly interact with other biotic components (insects,<br />
game, etc.). Vegetation has been also identified as a specific target for the calculation of<br />
critical loads/levels. Secondly, vegetation is a good bioindicator of environmental changes. Our<br />
current k<strong>no</strong>wledge of the ecological niche of numerous plant species allows changes in underlying<br />
environmental factors to be deduced from vegetation changes. Thus, the long-term study<br />
of vegetation dynamics at selected locations will provide information on changes in other forest<br />
ecosystem variables (soil, microclimate, etc.).<br />
The two main objectives of the vegetation assessment are:<br />
• characterization of the current state of the forest ecosystems on the basis of their<br />
composition;<br />
• monitoring of the vegetation changes due to natural and anthropogenic environmental<br />
factors.<br />
The characterization will allow plots to be positioned within identifiable vegetation types. The<br />
aims of studies of vegetation dynamics are to describe, explain and model succession, by an<br />
analysis of pathways, causes and mechanisms of vegetation changes.<br />
2 Sampling design<br />
Since there is a trade-off between the accuracy of species cover estimation and the area which<br />
can be surveyed, two different sampling designs may be used, which either lead to a more<br />
qualitative or to a more quantitative characterization:<br />
• in the first case, the dynamics are assessed by monitoring changes in the species composition<br />
of a large number of species over a large area, utilizing sampling units greater than<br />
100 m 2 , with a low to medium accuracy in estimates of changes in cover for each of these<br />
species;<br />
• in the second case, the study concentrates on population dynamics (expansion or regression)<br />
on a smaller area. Small sampling units (in general under 10 m 2 ) are used for a more<br />
accurate estimation of species cover.<br />
The area selected for vegetation assessment must be representative for the plot, in order to<br />
allow the comparison with other parameters recorded on the same plot. Several sampling units<br />
can be used in order to obtain statistical replication.<br />
2.1 Total area surveyed, number and shape of sampling units<br />
According to phytosociological usage, the minimal requirement is to sample almost all of the<br />
species at the plot level. In order to achieve comparability of results between countries, a<br />
common sampling area (CSA) of 400 m 2 , representative for the ground vegetation of the Level<br />
II plot, is man<strong>da</strong>tory. This area can be reached as the sum of smaller sub-plots within the Level<br />
up<strong>da</strong>ted 06/2002