Long-term low-level nutrient additions significantly impact a low arctic mesic tundra plant community, but species responses differ from high-level fertilization: Implications for predicting climate warming impacts

Arctic climate warming is expected to enhance the soil’s supply of growth-limiting nutrients, resulting in changes in plant community composition. Much of our understanding of nutrient influences on tundra plants is derived from experiments with very high levels of fertilization. Here, aboveground biomass of all species in a mesic birch hummock community, and shoot extension of Betula glandulosa, were measured in response to 11-19 years of factorial annual low-level nitrogen (N) and phosphorus (P) additions that simulate climatically realistic anticipated increases in soil fertility. Only the low N addition treatment had significant effects, enhancing the mosses and some infrequent vascular species’ biomass, reducing others, while the dominant shrubs were unaffected. Hence, overall community composition was altered, but in markedly different ways than classic high-level fertilization responses. By contrast, when measured in much larger sampling areas (9 m2), birch shrub new shoot extens..., , # Long-term low-level nutrient additions significantly impact a low arctic mesic tundra plant community, but species responses differ from high-level fertilization: Implications for predicting climate warming impacts

Dataset DOI: [10.5061/dryad.wstqjq310](https://doi.org/10.5061/dryad.wstqjq310)

## Description of the data and file structure

**Birch shoot length measurements**

At the end of the 2022 growing season, we measured total shoot length and current year’s new shoot extension of all individual birch stems in centrally located 3 m x 3 m sampling areas within 3 replicates of each of the low N and low P factorial experimental plots at Daring Lake, NWT. For each birch individual ramet within the sampling area, the lengths of all stems arising from the soil surface and their associated branches were measured. Concurrently, any new shoot apical extension (i.e. current year’s primary growth) was identified and measured for each stem. Since a very considerable time was required to id...,