Abstrakt
Dendrochronology mostly deals with secondary (radial) growth and attention to primary (height) growth has so far been limited. However, tree-ring widths might not adequately represent stem volume increments, net primary productivity and the size of the tree stem carbon sink.
The main reason for the prevailing focus on radial growth is that establishing height growth chronologies requires time-consuming and destructive methods. However, for certain ecological applications, less laboriously acquired data on height growth averaged over several successive years are satisfactory.
Here we present an R package that contains a set of tools for the analysis of height growth. The tools have been developed for input data of tree-ring widths extracted from series of successive stem height levels.
Tree-ring widths ideally represent four directions in each cross section to capture potential changes in stem eccentricity between various height levels. The main computed parameters provided by the package include height growth along the stem, changes of stem eccentricity and stem taper.
Accurate determination of average height growth depends on the correct estimation of the number of tree rings at different stem height levels, which might be complicated by missing rings in off-pith cores. The presented package therefore also contains functions implementing common procedures for the estimation of the number of missing tree rings near to the pith.
Most outputs can be visualized graphically. The package is useful for estimating height growth in ecological and dendrogeomorphological studies, especially in situations where both primary and secondary growth is influenced by different environmental factors.
It is also useful for analysing tree-ring chronologies assembled using serial sectioning, which typically applies to shrubs.