Variation in Soil Characteristics Decouple Nitrogen and 15N in Riparian Salmon Forests in Haida Gwaii, British Columbia

Le résumé fourni par la source

Nitrogen is an essential and limiting nutrient in terrestrial ecosystems. In certain places, such as seabird islands and salmon forests, animals transfer large quantities of marine derived nitrogen (MDN) into the system, lowering nutrient limitations and increasing productivity. Previous methods to study the ecological impacts of MDN rely on natural isotope variations between marine nitrogen and terrestrial nitrogen. However, they frequently do not account for the active role soils play in the assimilation of nitrogen or the isotope fractionation that occurs through microbial transformation. My research aims to identify how variations in soil properties affect the distribution and abundance of MDN across a range of distances to salmon rivers and forest compositions. We sampled soils in 33 plots across three different rivers at 0-10cm and 20-30cm of depth, quantifying plant characteristics in each plot. We then analyzed the soils for pH, particle size, 𝛿15N, 𝛿13C, and C:N ratios. Total nitrogen was best modeled by river, distance from river, and total carbon (R²c=0.72), while 𝛿15N was best modeled by river, depth, mean grain size, pH and total basal area (R²c=0.78). The divergence of these models suggests that microbial fractionation has decoupled the relationship between TN and 𝛿15N. This decoupling may be driven by anaerobic clay soils favoring denitrification that drives the loss of light nitrogen from the system or by efficient use of MDN through plant uptake. As a result, there is clear need for paired soil and foliar sampling and careful interpretation of 𝛿15N when assessing the role of salmon in driving the nitrogen cycle and structuring plant communities.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.