Glacial and Post-Glacial Shifts

The last glaciation caused dramatic changes in the forest composition of southern Italy. During glacial peaks, coniferous forests extended to sea level, while mixed oak forests dominated during temperate interglacial periods. The post-glacial period, which began approximately 11,700 years ago, saw several shifts in the distribution of deciduous oak forests in response to climatic changes. Oaks eventually established a relatively stable presence in a middle submontane belt, situated between the montane belt (dominated by beech and silver fir) and the Mediterranean evergreen belt. The climate-induced expansions and contractions during the post-glacial period are believed to explain certain characteristics of present-day oak forests, such as: the frequent replacement of mesic oak species (Quercus robur and Q. petraea) by more adaptable species like Q. pubescens and Q. cerris; the widespread presence of Q. cerris in the lower montane belt, favored by its adaptation to clay soils

Historical Human Impact

Over the centuries, human activities have drastically reduced the deciduous oak forests in the submontane belt. These activities include:

• Intensive cutting

• Agricultural expansion

• Grazing

Many historical documents and toponyms refer to areas where oaks are now absent or scarce. Oak forests were heavily exploited to supply shipyards, and the unification of Italy brought increased demand for agricultural land and railway sleepers, further contributing to forest reduction. In southern Italy, this has resulted in the clearing of many oak forests and severe fragmentation of remaining stands.

Oak Forests in Southern Inland Areas: The Case of Basilicata

In the inland areas of southern Italy, such as Basilicata, Quercus cerris dominates the natural forest vegetation between 500 and 1200 meters altitude. The composition and structure of these forests vary with altitude:

• Up to 1000 meters: Turkey oak mixes with maple and hornbeam, often featuring a dense understory of shade-tolerant species like wild rose, Cytisus sp., hawthorn, blackthorn, Lonicera sp., etc.

• Above 1000 meters: Oak forests transition to montane beech forests, including species such as maple, sycamore, and Lobel's maple

• In warmer locations: More xeric forests develop, where Turkey oak associates with Hungarian oak (Quercus frainetto) and downy oak (Quercus pubescens), often with a shrubby understory

Current Forest Structure

The present-day oak forests in this region are characterized by:

• Predominance of even-aged stands with mono-layer canopies, often resulting from the conversion of coppice to high forest

• Occurrence of bi-layered stands where oaks dominate a hornbeam layer

• Presence of "aged" coppice stands that have exceeded traditional rotation periods

• Frequent heavy grazing in many oak stands