VARIANCE AS AN ECOSYSTEM PROPERTY: LESSONS LEARNED FROM LONG-TERM APPROACHES

Aquatic ecology was predicated on the assumption that the variability of lakes is stable and can be partitioned into that which is known (explained) and that which is yet to be understood (unexplained or error).  However, this paradigm was disrupted in the late 1990s by the Trophic Cascade Hypothesis which envisioned variability as an intrinsic ecosystem property subject to its own controls. Whole-ecosystem experiments were subsequently used to elucidate the controls of lake variability; however, they can be difficult to interpret if their scale and magnitude are not realistic, if the trials alter fundamental lake properties, or if lake response is influenced by past conditions. Fortunately, studies spanning decades can help place large experiments into context and define the spatial and temporal variance of lakes.  These approaches include: decadal monitoring of lake properties; continuous small-scale experiments within the long-term context; repeated landscape-scale surveys; high-resolution monitoring, remotely-sensed time series, modelling and; paleolimnology. These approaches show how historical conditions alter ecosystem variability, cause abrupt state changes, and persist for decades after removal of stressors,  Similarly, long-term approaches are the main means to quantify the presence and effects of cyclic (migratory), discontinuous (catastrophe), slow (warming), or cryptic (emerging) phenomena on lakes. Comparisons among long-term approaches identifies their relative strengths and weaknesses, while forecasting the path forward for the next century.

Primary Presenter: Peter Leavitt, University of Regina (peter.leavitt@uregina.ca)

Authors:

The Members of the Limnology Laboratory, University of Regina  (Limnology@uregina.ca)