The objective of the SelPiBio Life+ project is to demonstrate how an innovative silvicultural treatment in Pinus nigra increases the degree of the biodiversity at the level of the soil environment (fungi, bacteria, flora, mesofauna, nematodes). In particular, the effect of the selective thinnings respect the traditional mode is evaluated and the absence of any treatment in pine stands in juvenile stages at the level of production and forest protection and soil biodiversity.

New logging practices in the forests

Italian biodiversity experiment

Although the effectiveness of effects on increasing the stability of black pine monocultures has been already demonstrated, this practice has not been adopted usually in the pine forests of the Apennines. Within this project, the goal was to demonstrate that innovative management technique may change the diversity of the horizontal and vertical structures of the forest, and consequently the canopy, which determines a light, water and temperature regime different at the soil level and therefore, helps to increase plant, mycological and microbiological biodiversity ant the creation of others habitats, ecological niches, source of nutrients, favoring the increased biodiversity.

Specifically, the project will deliver the following results:

• analysis of the relationship forest structure – mycological biodiversity
• analysis of the relationship forest structure – flora biodiversity
• analysis of the relationship structure of the forest – biodiversity mesofauna
• analysis of the relationship structure of the forest – biodiversity of soil microbial components
• multiple correlations between soil biodiversity components considered
• selvicultural relationship between treatment and timber production (rate of increase of the economic value of the mass as a function of the applied treatments).

  

All these forests come from forest restocking. It began in Italy around 1880 in the ex-austrian regions. Around the early 1900s, the afforestation of black pine spread in almost all Italian regions. The firsts forest restockings were mostly with a single specie although eventually form in association with Acer pseudoplatanus. Among the many species and provenances  it used Pinus austriaca (Hoss) on calcareous soils and subspecies Pinus calabrica Delam.  on substrates rather acidic nature. The firsts thinnings are usually made later than expected; in fact, it is rare that the first treatments were carried out of less than 30-35 years old.

The traditional thinnings

The thinnings are the selective removal of trees, primarily undertaken to improve the growth rate or health of the remaining trees. The classical silviculture for black pine expect a low thinning with a frequency of 10-15 years for a rotation-age of 90 years.

From an analysis performed on 88 experimental masses in Tuscany in permanent plots of the CREA SEL (compared among them) it follows that the relationship between the dominant and the dominated floor remains practically constant in the development stages of pole and sawtimber that they have not had any treatment. In these developmental stages the number of pines dominated percentage is about 25% of the total number of plants.

Therefore the first thinning, acting on approximately 30% of the number of individuals do not affect at the dominant floor.

Recent experimental studies have shown that the sensitive part, because of the thinning, is the dominant forest floor (Cantiani and Piovosi 2009, Bianchi et al. 2010). Treatments that do not affect the dominate forest floor do not make any effect on the growth and stability of the forest. Without influencing the dominate forest floor, the radiation received on the soil is not modified significantly and therefore does not influence the dynamics of the flora and the rest of biotic soil components. In contrast, treatments of high thinnings  and selective thinnings modificate significantly positively all these characteristics.

The variable-density thinnings

The proposed method is based on experimental evaluations, and has the characteristic of being easily applied. As already mentioned, there is a selective thinning system with the aim of increasing the functionality of the pine forests, with particular attention to the role of hydrological protection. The method is valid for forest restockings with a medium to good  vegetative vigor with a regular density and no evidence of pathological problems.

The signaling of the specimens for cut in the first selective thinning is characterized by:

• positive selection of candidate plants to form the mass that will reach end of shift;
• liberation of the candidate of its direct competitors, meaning all those that represent an obstacle to the free growth of the canopy of the candidate plants.

With the choice of the candidates plants, we have the opportunity to guide the stand from the point of view of the specific composition. It is a choice made in the forest management plan and closely dependent on the characteristics of the stand treatment objective.

The successive stage of the definition of the candidates plants is to liberate it of their  immediate competitors. Competing plants are those that intertwine directly in their natural development of the canopy with the canopy of the candidates. Searching the efficacy of the treatment it would be sufficent to release the candidates of the dominant and co-dominant (on the top of the canopy) plants that are in direct competition with them. In order to get greater effectiveness in increasing the differentiation degree of structural  of the stand and help increase microclimatic soil changes (ligth and water) and promote biodiversity at soil level, it is also recommended to remove the plants of the dominated floor bordering the candidate.

The removal of competing plants aims to liberate fully the canopy of the candidate plants creating a discontinuity between the whole crown of the canopy of each candidate and those of potential future competitors plants.

Conclusions

The proposed silvcultrual method has the followings strong points:

• The method has been designed based on the analysis of real structures of black pine forest restocking present in the Apennines (generally sawtimber where the density depends directly of the auto-thinning);
• it is a thinning system with a simple and easy application;
• it is a elastic method, despite the necessary rigidity in the application of some parameters (limit on the maximum number of candidates and, above all, the importance of choosing plants with good physical and biological characteristics);
• it controls treatment evaluations ( the indelible marks of the candidate plants ensures the subsequent control of the choices);
• it encourages in a short terms to increase the mechanical stability of the stand;
• guarantees greater timber harvesting in terms of quantity and quality of the products;
• increases the diversity of the horizontal and vertical structure of the treated stands;
• increases the diversity of the micro-environments and therefore biodiversity at the soil level;
• makes more flexible the choice of the different options for the regeneration/ succession of the stands.

Any manipulation by  the man over a forest, despite the positive expectations, is also a disorder. The cutting of some plants may involve mechanical damage to plants left standing; classic activities skidding, although is carried out with light machinery, produce impacts to ground level (soil compaction, rolled on the floor, etc.).

Forest management in recent decades has been towards with an excessive caution in the silvicultural activities. This has led, in the specific case of the thinning in the sawtimbers, to act almost exclusively in the dominated floor, following the logic of “disturbing” as little as possible the stand dominant floor. Often these interventions of minimum actions do not follow the logic of improving the social and ecological productive, protective, and yet can assume only negative effects for the general system of the forest.

The variable-density thinnings porposed by the SelPiBio project is consistent with this logic.

The cardinal points of the intervention mode are:

• the effectiveness of the intervention in providing effective stimulus to growth and improving the shape of the individuals candidates (protective and productive function);
• creating an optimum environment for increasing plant and animal biodiversity.

Source: SelPiBio Project: Cantiani P., Sanz Canencia, I., et al. (2016). SelPiBio project tecnical manual.

Images: Cantiani P., Sanz Canencia, I., et al. (2016). SelPiBio project tecnical manual.