A dendroecological reconstruction of age structure and past management in an old-growth pollarded parkland in northern Spain

Pollards have great aesthetic, historical and natural interest. They support many dependent organisms that are rare or infrequent in other habitats. But the area occupied by pollarded woodlands in Europe has become dramatically reduced since mediaeval times. The study of past management practices in pollarded woodlands could provide useful information to develop restoration and management plans. Tree populations structure and past management systems were studied in Tragamon, an old-growth pollarded parkland in the coastal plain. of Asturias, northern Spain. Dendroecological techniques were used to estimate tree ages and to reconstruct canopy history. Pedunculate oak (Quercus robur L.) was the dominant species, with veteran pollards up to 170 cm in dbh. Three main oak cohorts were found: juveniles <50 years, mature trees 130-210 years old, and old-growth trees between 230 and 500 years. The uneven spatial distribution of these cohorts could be a consequence of the contrasting alternation of heavy and lighter grazing intensities in different sectors of Tragamon. Trees were first cut at 30-36 years of age on average. In the period 1730-1849, signals of pollarding occurred synchronously among trees widely spaced throughout the park, indicating mean cutting intervals of 6-9 years. Between 1850 and 1909, mean cutting intervals were 10-12 years and more than 50% of the sampled trees in Tragamon were pollarded in 1905. Since that year, pollarding frequency and intensity have largely declined leading up to a maximum cutting interval of 76 years. Synchronous growth releases in 1976, 1985, and 1992 suggest that significant episodes of tree deaths occurred over the past three decades. The encouragement of oak regeneration and the creation of new pollards are recommended to guarantee the long-term continuity of old pollards and to preserve their singular structure and ecological importance. (C) 2004 Elsevier B.V. All rights reserved.