Turkey Lakes Watershed Study reference list: 2018

18-01 Buttle, J.M., K.L. Webster, P.W. Hazlett and D.S. Jeffries. 2018. Quickflow response to forest harvesting and recovery in a northern hardwood forest landscape. Hydrological Processes doi: 10.1002/hyp.13310

Summary: Hydrologic response to forest harvesting was studied by evaluating catchment quickflow (QF, water delivered rapidly to the stream channel), a metric of high-flow events controlling a catchment’s solute and sediment export. A 31-year examination of QF delivery from treatment (clearcut, selection, and shelterwood harvest) and control catchments in a deciduous forest landscape in TLW was conducted. Prior to harvesting, there was no significant increase in QF with P (precipitation) below a threshold P of 35-46mm; however, there was a significant QF vs. P relationship below this threshold for all treatments postharvest. Clearcutting increased the number of QF events for the entire postharvest period and the first 9-year postharvest compared to the other treatments; nevertheless, evidence for inter treatment differences in total QF depth delivered from catchments during the growing season was inconclusive.

18-02 Buttle, J.M., F.D. Beall, K.L. Webster, P.W. Hazlett, I.F. Creed, R.G. Semkin and D.S. Jeffries. Hydrologic response to recovery from differing silvicultural systems in a deciduous forest landscape with seasonal snow cover. Journal of Hydrology doi: 10.1016/j.jhydrol.2018.01.006

Summary: Results from a 31-year examination of hydrological response to and recovery from alternative harvesting strategies in a deciduous forest landscape with seasonal snow cover in the TLW. A quantitative means of assessing hydrologic recovery to harvesting was also developed. Clearcutting resulted in increased water year (WY) runoff and increased runoff in all seasons, with greatest relative increases in summer. Direct runoff and baseflow from treatment catchments generally increased after harvesting, although annual peak streamflow did not. Largest WY runoff, seasonal and direct runoff, and baseflow increases occurred in the selection harvest catchment, likely as a result of interception of hillslope runoff by a forest access road and redirection to the stream channel. Hydrologic recovery appeared to begin towards the end of the 31 years, but was incomplete for all harvesting strategies 15 years after harvesting. Harvesting enhance the relative importance of surface and near-surface water pathways on catchment slopes for all treatments, with the clearcut catchment showing most pronounced and prolonged response.

18-03 Senar, Ó.E. 2018. Causes and consequences of soil carbon mobilization and lake brownification in northern forested landscapes. 2018. PhD Thesis, Western University, London. 148 pp, 3 appendices.

Summary: This dissertation investigated the causes of soil carbon destabilization and consequences of the mobilized soil carbon to lake food webs in catchment 38 in TLW. Carbon export increased as temperatures increased. Changes in hydrologic connectivity interacted with topography to modulate the timing, magnitude, and fate of soil carbon export. Increased temperatures led to changes in hydrologic disconnectivity that favoured export of soil carbon from carbon-rich wetlands to the atmosphere. However, extreme precipitation events saturated the soils and increased the frequency of periods of hydrologic connectivity from the catchment to the drainage network that led to higher export of carbon to streams, rivers and lakes. Increased carbon content in lakes resulted in lower light availability and larger nutrient pools in lakes. Brownification of clear oligotrophic lakes increased pelagic primary productivity, but favoured cyanobacteria that could adapt to the browner conditions. Changes in biomass and composition of phytoplankton communities altered the carbon transfer and efficiency of lake food webs.

18-04 Senar, Ó.E., K.L. Webster and I.F. Creed. 2018. Catchment‐Scale Shifts in the Magnitude and Partitioning of Carbon Export in Response to Changing Hydrologic Connectivity in a Northern Hardwood Forest. Journal of Geophysical Research: Biogeosciences doi: 10.1029/2018JG004468

Summary: The results from a 5-year study of a northern hardwood forested catchment (TLW) indicated that hydrologic connectivity affected both the magnitude and fate of carbon export. Atmospheric carbon export was the major pathway from the catchment; its rate was regulated by topographic position but enhanced or supressed through changes in soil moisture and hydrologic connectivity. Past trends suggest a shift to a warmer climate and changes in the timing, duration, and intensity of hydrologic connectivity that are leading to an increase in annual atmospheric carbon export but a decrease in annual aquatic carbon export, despite the intensification of autumn storms. The increase in atmospheric carbon export creates a positive feedback for climate warming that will further disrupt hydrologic connectivity and aquatic carbon export, with consequences for downstream streams and lakes.

18-05 Yeung, A.C.Y., J.L. Musetta-Lambert, D.P. Kreutzweiser, P.K. Sibley and J.S. Richardson. 2018. Relations of interannual differences in stream litter breakdown with discharge: bioassessment implications. Ecosphere doi: 10.1002/ecs2.2423

Summary: This study quantified how interannual hydrologic differences contributed to the spatio-temporal variability of litter breakdown rate and its components (fragmentation, λ_f; and dissolution and microbial decomposition λ_m) in low-order unimpacted, perennial streams across three climatically similar regions in temperate Canada (including TLW). Contrary to the hypothesis, interannual hydrologic variability was unrelated to λ_f and poorly predicted λ_m and litter breakdown rates in course leaf bags (k_c) during fall within regions. Within-region spatial and temporal differences in k_c approximated or exceeded the range of natural variability suggested to characterize reference conditions by a bioassessment framework. There is a need to include other structural and functional indicators to ensure comprehensive stream bioassessments.