what are the green giants

more important?

The data compiled so far have led to some conclusions about the importance of large trees in Lousada and where conservation efforts should be made.

Although there are several studies on the importance of large trees and their microhabitats, this is the first national effort dedicated to this theme.

During this Lousada project, the importance of trees in terms of habitat support functions was measured based on the diversity of microhabitats that these trees have. The analysis was carried out with the 10 most common species in the territory.

The diversity of microhabitats varies from tree to tree, however there are easy-to-measure characteristics that allow estimating their value for each tree. Our analysis concluded that the diversity of microhabitats for each tree varies with:

1. ITS trunk diameter

For any tree species, the larger the diameter of its trunk, the greater the diversity of microhabitats found .

2. ITS total height

As we can see in the image above, there is a time in the life of a tree that they start to lose height because they can no longer bear the weight of their leaves, thus losing some branches to compensate.

Smaller trees have a general tendency to have a greater diversity of microhabitats. If this low height is found in trees with a large diameter of trunk, it is because we are almost certainly facing a tree of great age and therefore with some signs of decay, potentiating a panoply of microhabitats only found in trees with these characteristics .

3. The management applied to each tree

The management applied to trees, such as pruning, has a great influence on the diversity of microhabitats present and can either increase the existing diversity or lead to a reduction in it.

Tree pruning usually leads to a standardization of existing microhabitats, these trees being dominated by wounds that sometimes turn into cavities and devoid of natural microhabitats like dead branches.

4. The species of the tree

The average diversity found between different species of trees allowed to identify those that are most important to support biodiversity.

The natural differences between species are able to greatly dictate the microhabitats found in the trees. However, their anatomy, capacity for growth, the relationship they have with other organisms, the functions they have in the territory and which dictate the management applied to them, leads to great variations in this comparison between species.

The following graph shows the importance relationship between the 10 most common species, based on the most important species - Quercus robur (alvarinho oak). This graph takes into account only the species of the tree, removing any of the remaining factors that lead to changes in these results.

Taking these results into account, for example, a plane tree with the same dimensions and applied management as a white oak, will have only 58% of the diversity of microhabitats that the white oak has.

Different species despite having similar microhabitat diversity values, the set of these structures can be very different. For example, Pinheiros pinaster ( Pinus pinaster ) and Tilias ( Tilia sp. ), With equal values ​​of diversity compared to the oak, support completely different microhabitats.

In pine trees it is expected to find dead branches, rough bark and wounds from loss of branches. In linden trees it is normal to find a smoother bark, a great diversity of epiphyte organisms such as lichens and mosses.

Although we have more important species than others, there are variations among them that must be taken into account in moments of decision in the management of the territory, especially if we aim to help support biodiversity.

To find out more about the work that has achieved these results, access here .

© Gigantes Verdes, 2020