Maria Chiara Manetti

Site-specific growth responses to climate drivers of Pinus pinea L. tree rings in Italian coastal stands

ContextSix Pinus pinea stands growing under the Mediterranean type climate in Italy along the Tyrrhenian and Sardinian coasts.AimsTo identify the main climatic factors driving variability in growth responses to contrasting climate conditions at local and regional scales using tree-ring analysis.MethodsCommon growth patterns in tree rings were explored with clustering techniques. Local and regional growth responses to climate were examined using a dendroclimatic analysis. To remove the age-dependent trend we decomposed the tree ring width data into age-bands, thereafter standardised and recombined into a single mean site chronology.ResultsThe main grouping of tree ring series reflected climate-driven growth patterns, with a clear separation between stands from wetter and drier sites. The most interesting results were found at a seasonal scale and showed i) a shift of the main precipitation inputs from previous autumn-winter to current early-spring period, and ii) a bimodal pattern of sensitivity to water availability, when increasing drought conditions.ConclusionOur findings suggest that water deficit limits P. pinea growth also during late summer months in drier sites. In view of the projected increases in the frequency and duration of summer droughts in the Mediterranean basin, detecting differences in growth responses to site-specific climate patterns may allow selection of more appropriate mitigation and conservation strategies across most of its present range.

Climate variability, soil aridity, and growth rate of Pinus pinea L. in Castelporziano forest: an exploratory data analysis

Sensitivity to climate change and anthropogenic disturbance is a typical feature of Mediterranean forests growing under dynamic and manipulated environmental conditions. In the present study, a large sample of stone pines (Pinus pinea L.) was analyzed in five sites of Castelporziano and Castelfusano forests (Rome, central Italy) to assess tree-growth variability (1964–2009) with the aim to derive information on long-term climatic trends possibly reflected in the radial growth response. The multivariate exploratory analysis of tree ring widths, which were standardized to remove the age trend, showed a marked spatial variability among sites and a heterogeneous time pattern that allows for the classification of the investigated years into three homogeneous groups: 1964–1974, 1975–1997, and 1998–2009. The years 1975 and 1998 were identified as the candidate break points in the local climate regime. Coherence of the 1998 break point was verified by comparing two time intervals (1981–1997 and 1998–2011) of the meteorological time series of precipitation and temperatures available for Castelporziano station. Results indicate a significant shift toward aridity and warming in the area supporting the information obtained from the analysis of dendro-chronological time series. Implications of the spatio-temporal monitoring of climate variations through indirect sources are discussed in the light of conservation of the residual pristine forest of Castelporziano taken as a paradigmatic example for other Mediterranean coastal forests.

Tree-Ring Growth Trends of Abies alba Mill: Possible Adaptations to Climate Change in Marginal Populations of Central Italy

A dendroclimatic analysis was used to assess the climate-growth relationships of Abies alba Mill. over the last century in marginal populations of Central Italy. Tree-ring cores were collected in five mixed silver fir forests at low and high-elevation sites of the Apennines range in Tuscany and Marches. Regular and moving correlations functions were applied to tree-ring width series and monthly climate gridded data. Principal component analysis displayed groups of chronologies with similar growth patterns, discriminating for altitude and geographical location. Climate-growth relationships showed the positive influence of late-spring and summer precipitations and the negative effect of summer temperatures. Stands growing within the optimal altitude range for the species showed a positive and a decreasing negative influence of spring and summer temperatures, respectively. At the highest site (1375 m asl) the positive effect of previous year spring-summer precipitation and summer temperature of both previous and current year became scarce or null. Results suggest that the shifting influence of summer precipitation on tree-rings growth from July to August of the previous year is a possible response of silver fir to the significant reduction of spring precipitation and general temperature increase throughout the 20th century.

Old-growth forests. report from the plots established by Aldo Pavari

The canonical attributes of old-growth forests, their importance for management approaches fostering the development of structurally complex conditions are reported. The relict presence of primary forests led to withdraw from the regular silvicultural management patches of forests and assign them to a non-intervention regime. They have been referred to as “unmanaged forest reserves”. In this context, at mid 1900, A. Pavari established a network of 24 permanent plots at the purpose of “saving from anthropogenic disturbance and studying the natural evolutive pattern of different forest types to establish wellgrounded rules of management”. Most of plots set up by Pavari have nowadays lost their effectiveness because of various occurrences. Five plots are described here as for their numerical, structural and compositional dynamics. The recorded parameters draw systems that, even if far from equilibrium, show the occurrence of positive evolutive patterns. Differences to natural forests are, basically, the heritage of the previous multiple uses of forest soil and stand as well. On this basis, the component species have modified their presence in term of richness, evenness and dominance, depending on their auto-ecology,resistance or resilience. The long-term monitoring of primary forests and secondary systems left to the natural evolution finds out manifold, sound reasons today. The practice of ordinary management has been reduced greatly and the foreseeable trend is to increase further over the next period. According to its progress, many forests are experiencing a prolongation of the prearranged rotations and a post-cultivation phase is becoming the rule; stands are therefore getting older. Findings by old-growth forests and unmanaged forest areas monitoring will provide references for managing this diffuse condition.