Experimental Warming of Typically Acidic and Nutrient-Poor Boreal Soils Does Not Affect Leaf-Litter Decomposition of Temperate Deciduous Tree Species
Belanger, N. and C. C. Richard. 2023.
Abstract
Ongoing rapid climatic changes are expected to modify the structure, composition, and
functioning of forest ecosystems. Studying the influence of such changes on biogeochemical processes is thus crucial for a fuller understanding of forest response to climate change. In a temperate
forest of Quebec, Canada, we emulated climate change by warming the acidic, nutrient-poor, and
dry soils of two mixedwoods by 3 to 4 °C using heating cables. Leaf-litter mass loss of the local red
maple, sugar maple, large-tooth aspen, and American beech were monitored to assess the ability of
these tree species to condition boreal soils in the context of their northward migration under climate
change. We hypothesized that decomposition rates of all leaf-litter types would be decreased
equally by warming due to a drying effect of the soil and its surface, which is detrimental to microbial biomass and activity. Our results suggest differences in decomposition rates between tree species as follows: sugar maple > red maple ≥ American beech = large-tooth aspen. There was no indication of a slower turnover in these marginal soils compared to other studies conducted on typical
hardwood soils. Moreover, no difference in litter mass loss was detected between treatments, likely
due to a drying effect of the soil warming treatment. Results imply that climate change has a marginal influence on lea-litter dynamics of temperate tree species on soils that are typical of the boreal
forest. However, some variables that could play an important role on litter decomposition in the
context of climate change were not measured (e.g., plant phenology, understory composition and
density, microbes) and thus, uncertainties remain. The soil drying effect by warming also needs to
be further documented and modeled. The study year was characterized by significant periods of
water stress but was not considered an exceptional year in that regard. It would be relevant to test
for leaf-litter dynamics during dry and wet summers and verify again our initial hypothesis of decreased leaf-litter decomposition rates due to soil warming/drying.
Key Words
climate change; temperate forests; acidic soils; warming; drying; leaf litter dynamics
