Effects of community structure on aboveground net primary productivity (aNPP), leaf area index (LAI) and light use efficiency (LUE) in a boreal mixedwood forest of central Alberta, Canada.

• Author / Creator

  Rivera-Rios, Claudia A.

• Management practices, such as the use of herbicides to reduce abundance of deciduous and herbaceous vegetation can have dramatic influences on community structure and composition in regenerating boreal ecosystems. The vertical structure of boreal stands includes different functional groups: trees, shrubs, herbs, grasses and thallophytes. Each group develops its own leaf area contributing to the total leaf area index (LAI) and therefore to net primary productivity (NNP) of the ecosystem in different degree. However, multiple factors affect NPP and its study becomes complicated. An important concept that simplifies the study of biomass production as well as radiation interception is light use efficiency (LUE), which relates production to the amount of light intercepted.
  The main purpose of this research was to elucidate the effect of community structure on aboveground net primary productivity (aNPP), LAI and LUE.
  This study focussed on the effects of four selected treatments established at the “Judy Creek Mixedwood Experiment” near Whitecourt, Alberta: 1) removal of woody broadleaf vegetation (broadcast woody control; BW), 2) removal of both woody broadleaf and herbaceous vegetation (broadcast complete control; BC), 3) removal of herbaceous vegetation (broadcast herbaceous control; BH), and 4) untreated planted plots (broadcast untreated; BN).Clipped plots and biomass equations were the main methodologies used to evaluate overstory and understory NPP in 2012. Litter traps were used to measure deciduous litter production. A LAI-2000 Plant Canopy Analyzer was used to measure LAI and transmittance (DIFN) that were used to calculate LUE along with aNPP.
  Results indicated that applying vegetation control treatments alters vertical structure of young mixedwood forests, causing differences in the LAI and aNPP of the functional groups. All treatments affected the % cover of the understory. Plots with deciduous trees had significantly higher productivity than plots where deciduous trees were removed. Understory contribution ranged between 1 and 86% of total aNPP among treatments. The understory of the BW treatment where deciduous were removed but understory was not controlled developed a thick layer of grasses and had the largest percent contribution by the understory while treatments which removed herbs and grasses (BH and BC) had much lower contributions.
  Total LUE was significantly lower for treatments where woody trees were removed and highest efficiency was found in the treatment where herbs were removed but woody vegetation was left intact. Herbs, grasses and shrubs were more efficient in plots where no treatment was applied compared to treatments where any kind of vegetation control was performed. White spruce (Picea glauca (Moench) Voss) showed higher light use efficiency in the BC (broadcast complete control) treatment than in the BN (untreated) treatment. Positive linear relationships were found between total LUE and overstory LAI and between total aNPP and overstory LAI. Resulting equations allow estimation of aNPP and LUE of young boreal mixedwood forest from measurements of overstory LAI.

• Subjects / Keywords

  • aNPP
  • efficiency
  • LAI
  • understory
  • LUE
  • productivity
  • herbicides

• Graduation date

  Fall 2018

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3HM5317P

• License

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