c6.4.8 – Spontaneous establishment of Pinus nigra at high elevation in central italian apennines: a climate- or man-induced new upper treeline?

Urbinati C* (1), Cola A (2), Cingolani S (1)

Collocazione: c6.4.8 – Tipo Comunicazione: Presentazione orale
6° Congresso SISEF *
Sessione 4: “Sessione 4: Biodiversità, cambiamenti climatici, monitoraggio” *

Contatto: Carlo Urbinati (c.urbinati@univpm.it)

Abstract: A synergy of long term anthropogenic and natural disturbances altered forest cover, structure and functions in most areas of the Apennines in central Italy. Recent abandonment and climate variability seemed to have induced secondary succession processes at treeline ecotones. Such processes have been widely studied in many mountain regions around the world and also in the Italian Alps where natural reafforestation of coniferous species has widely and rapidly occurred in many areas. Less information is available for the Italian Apennines where most timberlines are formed by hardwood species and in particular by coppiced beech (Fagus sylvatica) woods. Shrub species such as Rhamnus alpina, fallax, and Juniperus nana are often involved in secondary successions along the elevation gradient, whereas the beech timberline are mainly stable over time, showing local changes in canopy closure and species composition. In several locations, few hundreds meters above the closed forest line (up to 1900-2000 m asl), where no other tree species are currently present, we have observed the presence of open and young cohorts (8-24 years) of Pinus nigra. This pioneer species was widely used in forest plantations for slope protection purposes at elevation between 1000-1500 m asl. We have investigated two sites in the Marche region at Monte Acuto (PU) and Monte Vettore (AP) in the calcareous “umbro-marchigiano” Apennine. We are testing the hypothesis that climate change could be the main driving force of the pine expansion, although the role of pasture abandonment or reduction is also questionable. Tree-ring and stem internode time series analysis performed on around 150 individuals allowed to assess the progressive establishment process and the climatic control of the height growth dynamics. The trees have low stature and sometimes a shrubby habitus, frequent stem mechanical damages, but vitality seems not compromised with a few trees having already reached maturity. Local and regional climate data show a clear warming trend in the last 20-30 years that could have triggered the pine recolonization. The positive relationship between global warming and treeline upraise has been proved in many studies especially in cold environments such as the arctic or the alpine ones. In the Apennines the temperature increase and the change of precipitation regimes, could reduce the oceanic or the sub-continental conditions which could favour the presence of Pinus nigra at higher elevations. Its dynmics above the current treeline does not seem a simple stochastic phenomenon but a more complex process including, the availability of seeds, their altitudinal dispersion efficiency, the selection of safe sites and the maintenance of suitable climatic conditions.

Citazione: Urbinati C , Cola A , Cingolani S (2007). Spontaneous establishment of Pinus nigra at high elevation in central italian apennines: a climate- or man-induced new upper treeline? . 6° Congresso Nazionale SISEF, Arezzo, 25 – 27 Set 2007, Contributo no. #c6.4.8