Structure and dynamics of radial growth in a pedunculate oak (Quercus robur L.) stand in the Cărpineni Forest District

Abstract

The pedunculate oak (Quercus robur L.) forests of south central Moldova developed under warm, arid conditions on the southern and southeastern hilly spurs of the Codri uplands (Forestry Districts of Cărpineni, Mereșeni, Bozieni, Anenii Noi, Zloți, Cantemir, and Baimaclia). The examined forest is a pure, even aged oak stand, 110 years old according to the forest management plan. It is naturally regenerated and of fundamental type, with an area of 2.0 ha. The site lies on an undulating lower slope with a southern aspect, a gradient up to 6°, and an elevation of 183 m above sea level. The soil is a typical clay illuviated chernozem. Across the stand, the diameter distribution is polymodal. Tree numbers fluctuate across the 16–48 cm and 68–72 cm diameter at breast height (DBH) classes, with peaks at 24, 28, 32, and 36 cm. This pattern is typical of natural forests and reflects light competition among mid and lower canopy trees, together with the absence of harvesting; older trees remain standing and enter decline. The results suggest that regeneration in the smallest diameter classes is influenced less by competition per se than by the presence of overstory trees (a shelter effect). The height structure is two layered. Heights were grouped into 2 m classes. Tree numbers from the lower to middle classes are relatively high, peaking at 12 m and a smooth transition among adjacent classes. The near uniform counts in the lower layer likely reflect horizontal canopy closure and a terminal development phase in which regeneration is prominent. Increment cores were used to develop ring width series for the stand. The series shows the signal typical of open grown (isolated) trees or low-density stands. Pronounced drought related growth declines are evident in 1946–1947, followed by post disturbance recovery.