Stand dynamics of naturally regenerated radiata pine (Pinus radiata D. Don) on Stonyhurst Station, North Canterbury, New Zealand: A dissertation submitted in partial fulfilment of the requirements for the Degree of Bachelor of Science with Honours At Lincoln University

Abstract

On Stonyhurst Station, North Canterbury, New Zealand an area of Pinus radiata has naturally regenerated after a catastrophic wind event 27 years ago. Two contrasting stands were selected (stands A and B) and the trees were measured to evaluate differences in structure between the two stands. Within each stand nine ten-tree variable radius plots were located in a systematic grid. Trees were measured for height, diameter at breast height and age. Each tree was classified as to what type of microsite it had established on. Mean plot tree density, mortality, height, basal area, volume and mean annual increment (MAI) were calculated on a per hectare basis for each stand. Individual tree means were also calculated per stand. Individual tree means were calculated for basal area, volume and MAI in both stands. Nearest neighbour competition was also measured. A competition index was developed to measure nearest neighbour competition. Stand A had less than half as many trees as stand B. Stand A also had taller trees and contained higher volumes but the individual tree basal areas were similar for both stands. Both stands had high numbers of trees that have survived from the first five years of establishment. These older trees had higher MAI values. Individual tree MAI in stand A was two times higher than stand B. A significant effect of nearest larger neighbour competition on individual tree MAI was found. In stand A there was a stronger correlation between individual tree MAI and the competition index. This indicates a stronger influence of nearest larger neighbours on tree growth rates in stand A. The frequency of trees on mound and even microsites was significantly different between stands. Trees on even ground microsites were common in both stands. In stand B mounded microsites produced higher MAI values than other microsite categories. This may indicate that mounded microsites increase MAI in suboptimal conditions. The strong differences between stand A and B appear to be influenced by aspect, which in tum affects soil properties. It is considered that moisture availability is having a strong influence on tree growth. Stand A, due to its aspect, is thought to have better moisture availability, creating faster growth rates resulting and higher variability in the stand structure. It also promotes intense competition for resources. Growth in stand B is considered to be limited by moisture stress resulting in slower growth rates, which in tum slows competition between trees. This has resulted in much higher stand densities in stand B. Further research is recommended to evaluate the effect of these soil properties on stand growth.