Spatial patterns of central European pointer years from 1901 to 1971

Three hundred and seventy-seven tree-ring width site chronologies including all eight principal forest tree species within Central Europe (5° to 15°E; 43° to 53°N) are expressed as Cropper-values and mapped using a Geographical Information System (here after referred to as GIS). Spatial classification of positive and negative growth anomalies and their occurrence within altitudinal zones, results in nine differing sub-groups of pointer years. In total, 39 years between 1901 and 1971AD are subdivided into these groups. The other 32 years show only growth anomalies in less than 40% of the research area, and therefore were excluded from further investigations.

Climatological interpretation of the growth patterns of the nine groups documents mutual temperature and precipitation forcings. Extreme positive pointer years represent optimal growth conditions, i.e., moderate cool and wet conditions during the growing season. For the other years we summarize (i) warm and wet (warm and dry) springs result in positive (negative) anomalies in the Central European lowlands and (ii) warm (cold) summers result in positive (negative) anomalies in the Central European highlands. In some years, however, similar climatological conditions yield to divergent growth response patterns.