Page 232 - Plant Canada 2024 Proceeding

PLANT CANADA 2024

[P57] DRIVERS OF UNDERSTORY VEGETATION COMPOSITION AFTER NOVEL SILVICULTURAL
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TREATMENTS IN CANADIAN BOREAL FORESTS. Marion Noualhaguet , Enrique Hernández-
Rodríguez , Miguel Montoro Girona . Groupe de recherche en écologie de la MRC Abitibi, Institut de
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recherche sur les forêts, Université du Québec en Abitibi-Témiscamingue, 445 boulevard de l'Université,
Rouyn-Noranda, Québec, J9X 5E4, Canada; and Universidad de Huelva, Calle Dr. Cantero Cuadrado, 6,
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21004 Huelva, Spain
Correspondence to: marion.noualhaguet@uqat.ca

Ecosystem-based management uses a wide diversity of harvesting practices to maintain forest
ecosystem integrity by reducing differences between natural and managed forests. The success of this
approach requires comprehensive assessments of forest community regeneration dynamics after
harvesting. Understory vegetation plays a critical role in forest regeneration due to its major implications
in biotic and abiotic interactions and is directly impacted by harvest. To guarantee the maintenance of
biodiversity, a clear and long-term understanding of understory vegetation evolution post-harvest is
crucial. We examined the impacts of novel harvesting patterns, in terms of intensity and spatial
configuration of stem removal, over 18 years post-harvest, on understory vegetation diversity and
composition in young and old stands of the Eastern Canadian boreal forests. Path analyses were used to
assess the indirect impact of harvesting via soil substrate, light condition, live and dead wood covering a
period of one year before and 18 years after harvesting. The understory vegetation was divided into the
three layers: bryophytes, herbaceous and shrubs. The understory diversity response was delayed the first
year after harvesting before reaching a peak 10-year post-harvest, leading to divergence based on
harvesting level, then gradually becoming more similar to unharvested as the canopy regenerates. While
species diversity can recover within 18 years of harvesting, composition takes longer, suggesting that this
metric might be better for assessing long-term effects of harvesting on biodiversity. The path analysis
revealed that trees, live or dead, were the primarily driver of understory community changes across the
fist 10 years post-harvest whereas the preceding understory composition was the mainly influencing
factor between 10- and 18-years post-harvest. These results highlight the complex biotic and abiotic
interactions among understory species, underscoring the importance of considering both environmental
factors and pre-existing understory composition when guiding sustainable forest management strategies
aimed at balancing economic interests with ecological conservation.

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[P58] DOES PHOTOPERIOD REGULATE METHANE EMISSIONS FROM PLANTS? Mirwais M. Qaderi
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and Kate Burton . Department of Biology, Mount Saint Vincent University, 166 Bedford Highway, Halifax,
NS, Canada, B3M 2J6
Correspondence to: mirwais.qaderi@msvu.ca

Previous studies have shown that light quality and quantity affect methane emissions from plants.
However, the role of photoperiod in plant-derived methane has not been addressed. We studied the
effects of two photoperiods – long day (16h light/8h dark), and short day (8h light/16h dark) – on growth
and methane emissions of lettuce (a long-day plant), mung bean (a short-day plant), and tomato (a day-
neutral plant) under a temperature regime of 22/18 C and photosynthetic photon flux density of 300 µmol
o
-1
m s . All three species were grown under both light durations. First, seeds were germinated in Petri
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dishes for one week, then plants were transferred to pots and randomly assigned to one of the two
experimental conditions. Under each condition, twelve plants were grown for 21 days; at that time, plant
growth and physiological traits, including methane emissions, plant dry mass, growth index,
photosynthesis, chlorophyll fluorescence, total chlorophyll, nitrogen balance index, flavonoids, and
anthocyanin, were measured. The lettuce plants that were grown under short-day photoperiod had the
highest methane emissions. The long-day plants that were exposed to short-day conditions and the short-
day plants that were exposed to long-day conditions were stressed; day-neutral plants were also stressed
under short days. All three species had decreased total dry mass under short-day conditions, most likely
because of decreased photosynthesis and increased transpiration and stomatal conductance. Methane
emission was positively correlated with shoot: root mass ratio, nonphotochemical quenching and
anthocyanin, and negatively correlation with stem height, total dry mass, photosynthesis, water-use
efficiency, total chlorophyll, and flavonoids. This study revealed that, besides light intensity and quality,
light duration can also affect methane emissions from plants.

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