African Wildlife And Environment Issue 73

CONSERVATION

Cores from different species of alien invasive trees cored around the Free State Province, South Africa

AT: What does your specific research work mean for environmental management? MK: By studying the tree ring width, and associated characteristics of poplar trees, I am hoping to determine the stand-age structure of different cohorts along the Caledon River. Exact age dating is key to determine both the time of establishment, and the mortality, of a specific tree population. This will tell us how resilient these species are to change in the flow-regime. Not much is known about the lifespan and recruitment success of this alien invader. But importantly, this will also create a more precise dataset of broader environmental parameters that will be more nuanced than the coarser datasets currently available for that specific catchment. Existing weather conditions and flow data will be used to calibrate the streamflow reconstruction mode. From that we can begin to determine if the tree ring width is a sensitive enough datapoint that reflects change in broader hydrological parameters. AT: On behalf of the readers I wish you well in your study. The research you are doing is pioneering because it is establishing a new branch of environmental science within southern Africa.

limits our ability to study the relationship between tree growth located at a precise point within an ever changing but larger environment. It is therefore possible to extend our climate data using proxy data, derived from tree rings, unlocking the nuance and texture from a dataset with greater pixel density. A tree ring responds to a change in environmental conditions. A narrow ring indicates limiting resources, such as moisture availability. On the other hand, several consecutive wider than average rings typically indicate a wetter than average period. AT: How do we dive deeper into the rich data locked within that library? MK: Several principles and concepts guide the study of tree rings. The principle of cross-dating is a key departure point. If a specific tree ring cannot be linked to an exact calendar year, we are unable to cross-date the sample. Cross-dating establishes a precise time stamp on the dataset, so once we have a known point of reference, we can accurately move back and forth over time. The ring-width patterns in one tree, should be matched up with the pattern of the same species of a larger cohort, to build a precise chronology. Missing rings, when no ring formation has taken place during a growth season, or the evidence of false rings, when more than one ring formed during a growth season, are just two of the challenges that dendrochronologists must deal with, when developing a chronology for an area.

Prof Anthony Turton Centre for Environmental Management University of the Free State

9 | African Wildlife & Environment | Issue 73 (2019)