Abstract

Abstract. Unraveling the environmental controls influencing Arctic tundra productivity is paramount for advancing our predictive understanding of the causes and consequences of warming in tundra ecosystems and associated land–atmosphere feedbacks. This study focuses on aquatic emergent tundra plants, which dominate productivity and methane fluxes in the Arctic coastal plain of Alaska. In particular, we assessed how environmental nutrient availability influences production of biomass and greenness in the dominant aquatic tundra species: Arctophila fulva and Carex aquatilis. We sampled a total of 17 sites distributed across the Barrow Peninsula and Atqasuk, Alaska, following a nutrient gradient that ranged from sites with thermokarst slumping or urban runoff to sites with relatively low nutrient inputs. Employing a multivariate analysis, we explained the relationship of soil and water nutrients to plant leaf macro- and micro-nutrients. Specifically, we identified soil phosphorus as the main limiting nutrient factor given that it was the principal driver of aboveground biomass (R2=0.34, p=0.002) and normalized difference vegetation index (NDVI) (R2=0.47, p=0.002) in both species. Plot-level spectral NDVI was a good predictor of leaf P content for both species. We found long-term increases in N, P and Ca in C. aquatilis based on historical leaf nutrient data from the 1970s of our study area. This study highlights the importance of nutrient pools and mobilization between terrestrial–aquatic systems and their potential influence on productivity and land–atmosphere carbon balance. In addition, aquatic plant NDVI spectral responses to nutrients can serve as landscape hot-spot and hot-moment indicators of landscape biogeochemical heterogeneity associated with permafrost degradation, nutrient leaching and availability.

Highlights

  • In the Arctic, plant growth is limited by several factors including low temperatures, short growing seasons and nutrient availability (Chapin et al, 1975; Shaver et al, 1998)

  • We focus on the influence of soil and water nutrients on plant biomass and greenness of Carex aquatilis and Arctophila fulva, the dominant aquatic emergent vascular plants in the Arctic coastal plain (Andresen et al, 2018; Villarreal et al, 2012), to answer the following questions. (i) How is aquatic tundra responding to nutrient availability? (ii) How does environmental nutrient status influence leaf nutrients in aquatic tundra? (iii) What are the spectral responses (NDVI) of aquatic tundra to nutrient availability?

  • We found significantly higher amounts of leaf Al, B, Ba, Mn, Na, Ni, Si and Zn in C. aquatilis compared to A. fulva (p

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Summary

Introduction

In the Arctic, plant growth is limited by several factors including low temperatures, short growing seasons (e.g., irradiance) and nutrient availability (Chapin et al, 1975; Shaver et al, 1998). Abrupt thaw and recent lake drainage events enhanced during warm summers have contributed to increased productivity through the availability of fertile soils (Jones et al, 2012; Loiko et al, 2020; Nitze et al, 2020; Turetsky et al, 2020). These factors highlight the complexity of tundra plant growth and production under a warming and changing Arctic with implications for carbon budgets (McGuire et al, 2018; Oberbauer et al, 2007). Unraveling the covarying climate and environmental controls influencing Arctic tundra productivity is paramount for advancing our predictive understanding of the causes and consequences of warming in tundra ecosystems and associated land–atmosphere feedbacks

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