Analiza comparativă a răspunsului dendroclimatologic al molidului (Picea abies (L.) Karst.) şi bradului (Abies alba Mill.) din nordul Carpaţiilor Orientali [Comparative analysis of the dendrochronological response of Norway spruce (Picea abies (L.) Karst.) and Silver fir (Abies alba Mill.), from the North of Eastern Carpathians]

Abstract

This paper present an exemple of the applicability of dendroclimatological research methods in the study of forest ecosystems, using the dendrochronological series from Giumalau Secular Forest (GIUA - Norway spruce), Slatioara Secular Forest (SLAA -Norway spruce, SLAB - Silver fir) and Demacusa Basin (DEMA - Silver fir). In the case of the Norway spruce, respectively the GIUA and SLAA dendrochronological series, one can notice a significant negative correlation with the temperatures from the end of the previous vegetation season (July, August, and September) and positive with the rainfalls from that period. The same type of reaction concerning the previous vegetation season is also present in the case of the Silver fir, but the intensity is lower. As far as the current vegetation season is concerned, the Norway spruce has a significant positive reaction (GIUA - February, March, SLAA - April, July) to the regime of rainfalls. The thermal regime at the end of the season of vegetative repose and at the beginning of the vegetation season, months January - June induces a positive response from the Norway spruce. The Norway spruce’s response to modification of the thermal regime in the vegetation season, months July-August, is negative, the high temperatures directly and indirectly determining a decrease of the growth in diameter rhythm. In case of the dendrochronological series from Giumalau Secular Forest - GIUA - the temperature in August is negative and significantly correlated with the growth index. The end of the vegetation season, namely September, has a positive influence on growth, as far as the thermal regime is concerned, the reaction being negative to pluviometric regime. In the case of the Silver fir, there is a positive reaction, even very strong and significant in the case of Slatioara-s series of growth indexes - SLAB, to temperatures from the cold season (December-March). The same positive response can be noticed in the case of the temperatures from the vegetation season (July - August), for the series of indexes from Demacusa Basin, the correlation being significant in the case of the temperatures from August. The rainfalls at the beginning of vegetation season (April - June) determine an acceleration of radial growth rhythm, but the correlation is insignificant from the statistical point of view. The comparative analysis of the series of real and estimated by statistical models growth indexes indicates a very good reliability of the response functions. Distribution of residual errors is random, except for the period 1985-1992 in the case of dendrochronological series from Slatioara (Norway spruce and Silver fir) and Demacusa, when the statistic model systematically overestimates the growth indexes. The explanation can be found in the presence of a disturbance signal with intense manifestation in this period, the hypothesis issued being the presence of some phenomena of intense pollution. This manifestation is very obvious, especially in the case of the Norway spruce from Slatioara Secular Forest - SLAA.