Trends and signals in tree-ring parameters

• Main Author: Konter, Oliver
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Johannes Gutenberg-Universität Mainz 2016
• Subjects: ddc:550; Fennoscandia
• Online Access: https://openscience.ub.uni-mainz.de/handle/20.500.12030/1963; https://hdl.handle.net/20.500.12030/1963; https://doi.org/10.25358/openscience-1961

Tree-rings are frequently used to develop annually resolved paleoclimate reconstructions of periods in time when meteorological instrumental measurements are not available. Commonly used proxy records derived from tree-rings are ring width, maximum latewood density, and stable carbon and oxygen isotopes. Calibrating the different tree-ring proxies against available meteorological data is a prerequisite for reconstruction approaches, as results provide the essential statistical relationships to convert proxy data into the targeted climate data. Additionally, the evaluation of potential non-climatic biases is crucial for accurate calibration results. In this dissertation, methods for identifying proxy-specific biases are developed and evaluated for associated impact on various calibration setups. Focus is placed on age-related climate sensitivity trends in growth and density data, insect-induced disturbances in interannual growth patterns, and effects of elevated atmospheric CO2 concentrations on stable isotopic compositions. Age-related alternation in the climate sensitivity of tree-ring width data has been previously reported and is here revisited by analyzing a large dataset of 692 Pinus sylvestris L. series from northern Fennoscandia. Additionally and for the first time, maximum latewood density measurements of the same trees are included. Results indicate significant decreasing climate sensitivity with increasing age in both tree-ring parameters, while density data are less affected, thus, more suitable for the development of climate reconstructions. Temperature reconstructions for this region can dismiss age-related biases, by using density data from evenly distributed cambial ages, i.e. including young and old trees, as a function of time. The larch budmoth (Zeiraphera diniana Gn.) is characterized by regular population oscillations and cyclic mass outbreaks (8-10 years), causing interannual disturbances in tree-ring width chronologies from host trees and reduced climate signal strength. In contrast to ...