sdu faculty of forestry journal special edition 2009 - Orman Fakültesi

SDÜ Faculty of Forestry Journal
Analysis of means shows that the districts which differ the most of the global
mean are Retiro and Salamanca. In both of them, the areas of the studied green
spaces reached lower figures than the rest of the districts. A possible explanation is
that the bigger the area of green spaces observed is, the more representative of the
district it becomes; however it is likely that an area threshold exists, so from this
point the results will be stable.
4.3 Main problem in trees is stem wounds.
The major problem in trees is stem wounds, followed by dead branches,
epicormic shoots and decay (Table 4).
Table 4. Percentage of affected SYGs by 4 main disturbances. In each year, during the
whole period and in all the inventoried green spaces.
224
% of SYGs
Disturbances 2005 2006 2007 2008 All years
Stem wounds 13.2 22.8 31.4 36.4 25.2
Dead branches 10.2 8.2 18.6 33.6 18.0
Epicormic shoots 4.3 12.2 1.4 31.9 15.9
Decay 13.5 17.9 17.1 12.6 14.8
Stem wounds is also the most important problem identified in some districts,
such as Arganzuela, Barajas, Hortaleza and Villa de Vallecas. The cause of this
high frequency was mostly unknown, but some SYGs with stem wounds had, at the
same time, sunburns lesions (11.2%) or human damages (9.0%) like those which
were caused by lawn mowers, vehicles, tree shelters, stakes, and so forth.
Therefore, these disturbances may have caused some of the stem wounds.
Stem wounds were also very common in several urban tree surveys (Rocray,
1983; Jaenson et al., 1992; Chacalo et al., 1994, Fostad and Pedersen, 1994;
Cumming et al., 2001; Ayuntamiento de Madrid, 2009), besides, in the last three
ones, the injuries were mainly caused by mechanized machinery and automobiles.
Neither of them mentions any kind of sunburn lesion on the bark, nor the one
conducted in street trees of Madrid.
Another consideration is the importance of SYGs which were damaged by
decay. More than 60% of the SYGs with decay had, at the same time, stem
wounds, which showed a possible relationship between these two variables. The
explanation is that wounds can be penetrated by organisms which produce decay,
such us fungi (Agrios, 2005). Therefore, the abundance of these two factors could
indicate bigger internal defects of the trees and, trees could turn into hazardous
because some decays might end up in failure. Besides, the strength loss due to
decay is greater when it is produced by peripheral wounds, as in this survey (Kane
et al., 2001). Any conifer SYG was affected by decay, maybe because of the
existence of resin, as it was explained by Rodríguez Barreal et al referring to
cypress (Rodríguez Barreal et al., 2000).