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Extension Note Vol 4: Lessons Learned from ThiRST

As Canada faces an increasing threat of more frequent and severe droughts, understanding how forests respond to such conditions is crucial for sustainable management. Dr. Loïc D’Orangeville, in collaboration with Silva21, the Canadian Forest Service, and JD Irving, is leading the ThiRST (Thinning to Reduce Stress) experiment at the University of New Brunswick. This study aims to explore the effectiveness of silvicultural thinning in mitigating drought impacts on white spruce.


The experiment involves a large-scale rainfall exclusion setup on a 16-year-old white spruce plantation, utilizing 82 eavestroughs constructed around individual trees. However, challenges during the field season, including a remote location and tricky topography, led to modifications in the original plan, with only two out of three blocks implemented. Unexpected structural issues, exacerbated by exceptionally wet weather, caused damage to eavestroughs, impacting the applied drought treatments and raising concerns about data integrity.


Despite setbacks, the project emphasizes key lessons:


Image 1. White spruce trees among plots with fully constructed eavestroughs at the ThiRST site. Photo: Chloe Larstone Hunt, 2023
  1. Material Selection: Careful consideration of materials is vital for outdoor experiments. Insights into using longer, thicker screws and high-quality lumber highlight the importance of robust construction.

  2. Uncooperative Climate: The unusually wet summer of 2023 posed challenges, potentially compromising the effectiveness of drought treatments. Climate fluctuations must be factored into experimental design.

  3. Expect the Unexpected: Despite meticulous planning, unforeseen structural issues arose due to the natural environment. Flexibility in adapting to unexpected challenges is crucial for successful experimentation.

  4. Rigorous Data Collection: The experiment underscores the importance of thorough data collection even in the face of unforeseen circumstances. Adaptability in statistical analysis ensures valuable insights, with future plans to explore tree-level effects and competition within each plot.


As the ThiRST experiment continues into the 2024 growing season, the lessons learned provide valuable insights for forest practitioners and researchers alike, emphasizing the need for resilience and adaptability in the face of complex field conditions. Be sure to read the full Extension Note.


This extension note was written by Chloe Larstone Hunt, a MSc student with Loïc D'Orangeville at the University of New Brunswick with the help of Amy Wotherspoon.


You can read more about Chloe's research (Project AD.3c) Rainfall exclusion experiment: the effect of thinning) here.

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