Prime indagini sugli effetti della selvicoltura d’albero sulle dinamiche di crescita e di competizione delle specie sporadiche tutelate dall’ordinamento forestale toscano
Author(s)
Sansone, Dalila
Date Issued
May 28, 2013
Type
Doctoral Thesis
Abstract
Aim of the work is to increase currently available knowledge on auto-ecology, growth and
competition dynamics of sporadic tree species. Species protected by Tuscany Forest Law on
the “custodial management of biodiversity” (art. 12, DPGR 48/R 2003) are being considered
here. These species are characterized by a weak competitive ability as compared with social,
dominant species and by a progressive disappearance in the final stages reached by the forest
coenosis. The customary, historically applied forest management, has not promoted and even
supported the presence of sporadic trees because based on the “stand approach”. Such
criterion does not increase compositional diversity because its main goal is the successful
tending and regeneration of main tree species only.
Attention paid nowadays to sporadic trees is due to biodiversity issues and to the inherent
species-specific ecological value, but it may be addressed too to a productive issue, many of
them growing valuable wood. Given the lack of concern for this purpose showed so far, large
knowledge gaps exist today both on the auto-ecology and silvicultural management of specific
diversity scattered into the main crop layer.
The work suggests the enforcement of a silvicultural model based on the criteria and methods
of tree-oriented silviculture, a well-known approach in Central Europe, rarely applied in Italy to
date. The main difference to traditional silvicultural practice is the implementation of
interventions only around the best phenotypes (target trees), aimed at tending, controlling and
speeding up their growth and getting in this way high quality timber, i.e. boles free of branches.
This technique foresees the removal of neighbouring trees in a way that crowns of selected
subjects are being allowed to growth freely. Care is devoted in the practice to balance cost of
intervention-economical revenue.
Demonstrative tree-oriented practices have been carried out on an area of 80 ha in two districts
different as for climate conditions and forest types: (i) the Colline Metallifere hilly area (southwestern
Tuscany): broadleaved forests aged differently and managed under the coppice with
standards system; (ii) the Abetone-Melo mountain area (north-western Tuscany, Apennine
range): beech evenaged forest aged differently and no more managed chestnut coppice forests.
The basic principles of tree-oriented silviculture have been adapted to the types concerned and,
in a few cases, this model has been integrated with traditional cultivation practices. Stands
representative as for tree species composition and management system were chosen and
described (mensurational and stand structure parameters) to define the general background
conditions of tree growth. In these stands 362 target trees of 12 different species were selected.
On this sample, monitoring was implemented according to the following contents: (i)
mensurational parameters (trunk and crown sizes); (ii) qualitative features (bole length free of
branches); (iii) gap sizes created by selective cuttings; (iv) level of inter-tree competition by the
Hegyi index.
Aim of monitoring layout is to check the variation of parameters of interest over time and verify
their relationships with the applied methods of silvicultural intervention. The most notable issue
seems to be the relationship dbh-crown growth with removal intensity. Stand structure analysis
showed to be helpful to defining tree removal effects on spatial arrangement and types of
diversity at the stand level. All these features were described by a set of specific indexes
(Richness, Shannon, Simpson (species diversity); Cox, Pielou, Clark-Evans (horizontal
structure); Species Profile Index, Vertical Evenness (vertical structure); Neighbourhood-Based
Indexes as for tree size, mingling and spatial arrangement.
First results show the effects on vertical stand structure and its diversity, even if the percentage
of removal at the stand level is very low (except where tree-oriented and traditional silviculture
are being practiced together). The intensity of spotty interventions is vice versa high, because of
the removal of competitors all around the target tree, i.e. of dominant trees. No information is
available about growth dynamics following practices implementation, since these have been
accomplished over the last two years.
We do think that the monitoring system defined at stand as well as at target tree level may be a
consistent and effective management tool, taking into account the increased attention devoted
to sporadic tree species. The demonstrative interventions were implemented into areas where
silviculture is a key economic sector. We suppose therefore this experience can contribute
spreading tree-oriented silviculture approach and increase the awareness of stakeholders about
the ecological and productive potential of regional forests.
Tailoring tree-oriented silviculture criteria to the specific quality of the intervention areas can
enhance biodiversity and increase the overall value of mass plus quality woody production. This
last issue can certificate the sustainability of the proposed silviculture as an optional forest
management system. The actual evaluation of tree-oriented silviculture effects on the dynamics
of stand structures and on the awaited enhanced biodiversity, requires anyway long-term
observations. In this perspective, the present work provides a basis and a starting point.
Additional information
Dottorato di ricerca in Scienze e tecnologie per la gestione forestale e ambientale
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