Tree species partition N uptake by soil depth in boreal forests

Area of Science:

• Ecology
• Forest Science
• Biogeochemistry

Background:

• Nitrogen (N) partitioning facilitates herbaceous species coexistence in N-depleted habitats.
• N partitioning in trees, however, remains largely unproven.

Purpose of the Study:

• To investigate N acquisition strategies of black spruce (Picea mariana) and jack pine (Pinus banksiana) in the Canadian boreal forest.
• To determine if spatial N partitioning occurs between these tree species.

Main Methods:

• Analysis of foliage and soil 15N natural abundance.
• A 12-year in situ 15N addition experiment.
• Comparison of N uptake depths between black spruce and jack pine across seven eastern Canadian boreal forest sites.

Main Results:

• Black spruce primarily absorbs N from organic soil layers.
• Jack pine acquires N from deeper mineral soil horizons.
• Consistent differences in foliar 15N natural abundance between species indicate widespread N spatial partitioning.
• Distinct relationships between delta15N and leaf N concentration highlight varied N acquisition strategies.

Conclusions:

• Complementary N acquisition mechanisms likely facilitate tree species coexistence in N-limited boreal ecosystems.
• N partitioning may contribute to the observed biodiversity-productivity relationship in the eastern Canadian boreal forest.
• Findings offer insights for forest management and understanding boreal forest regeneration processes.