Dendroclimatological investigations on teak (Tectona grandis L. F.) in Nilambur (North) forest division of Kerala

Abstract

A study was conducted on teak (Tectona grandis L. f.) grown in plantations at Nilambur (North) forest division with the objectives of analyzing tree-ring chronologies to find out their dendroclimatic potential and the tree growth-climate relationship and also to find out whether any significant relationship exists between climate and mean vessel area (MVA) of teak and its prospect for climatic reconstruction of the study area. In order to achieve the above objectives, cross sectional discs were collected from sites located in Edakkode, Kanakuthu and Conolly’s plot. The average ring width and MVA of each year obtained from the different radii were used to cross date and construct the chronology using the TSAP Win software. A cubic smoothing spline was used for standardization of the tree ring data using the software ARSTAN. Bootstrap correlation and response function analyses were carried out with moving intervals to find out tree growth-climate relationship using DENDROCLIM was performed. Statistical parameters such as Signal to Noise Ratio (SNR) and Expressed Population Signals (EPS) of all chronologies have desired levels and the sites had good dendroclimatic potential. Ring width and MVA chronologies of teak for the Nilambur region were developed. Rainfall in previous July, previous December and current October were correlated with ring width. Winter temperature (December-January) and southwest monsoon (June- September) were the seasonal climatic variables that mostly controlled ring width in the study sites. The monthly temperatures for January and previous June created major response in ring width. Mean vessel area responded to monthly rainfall for months previous June, previous September, previous November and current May. Seasonal climate which influenced vessel area were of southwest monsoon (June-September) temperature and rainfall and northeast monsoon (October-November) rainfall. Mean vessel area responded to monthly temperatures of previous August, current May and December. Using transfer functions climatic data for months and seasons with highest response and the period which is not available (1870-1900) from the instrumental record were reconstructed from tree ring data.