Understanding likely responses of a low Arctic mesic tundra plant community to anticipated climate warming using long-term, climatically realistic soil nutrient enhancements
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Authors
Wood, Dominic Anthony
Date
2025-01-10
Type
thesis
Language
eng
Keyword
Environmental Change , Arctic Tundra , Plant Community , Nutrient Cycling , Soil Fertility
Alternative Title
Abstract
Tundra plant community composition and structure will be directly influenced by the particularly rapid climate warming currently occurring in the Arctic. Furthermore, increased soil microbial activity due to warming will enhance the supply of growth-limiting nutrients to plants and therefore influence plant community composition. In recent decades, vegetation composition has been shifting in many locations across the Low Arctic and shrubs are expanding their cover and range. Tundra greening and the associated reduction in albedo (reflectance) as well as the potential for widespread soil carbon losses to the atmosphere are expected to cause significant positive feedbacks to warming. Currently, we have a limited understanding of these feedbacks – and particularly of how climatically realistic increases in soil fertility will impact vegetation.
Experimental warming significantly increased deciduous and evergreen shrub biomass after 14 years at the low Arctic Daring Lake site, and experiments with factorial large additions of nitrogen and phosphorus eliminating nutrient limitation have increased deciduous shrub growth there and at several other Arctic sites. While these high-level additions demonstrated species’ nutrient limitation regimes and established a dogma of nitrogen-limited plant growth in the tundra, they typically enhance soil nutrient availability far above expected what is expected with climate warming over coming decades.
In this study, plant community aboveground biomass, and shoot growth measurements of Betula glandulosa were measured after 19 and 18 years, respectively, of factorial annual low-level nitrogen and phosphorus additions to simulate climatically realistic anticipated increases in soil fertility Corroborating results from high-level fertilization experiments, the low nitrogen addition significantly influenced some individual species’ biomass, and community composition. Furthermore, soil active layer depth was significantly correlated with community composition, positively with some species and negatively with others, suggesting an additional mechanism by which warming may significantly influence tundra plant communities. Finally, only birch shoot growth measurements from the sampling year corroborated known NP growth colimitation. Together, these responses to low-level factorial N x P additions improve our understanding of likely plant community shifts in response to future climate warming, and suggest scalar issues are critical, often overlooked factors needed to accurately predict patterns of future plant community change.