Seasonal dynamics of plant available nutrients in a polygonal tundra landscape
Abstract
Soil nitrogen (N) availability is an important factor determining plant productivity and community composition in Arctic ecosystems, and is expected to alter with climate warming and degradation of permafrost. To effectively represent heterogeneous Arctic landscapes such as polygonal tundra in ecosystem models at multiple scales, an improved understanding of how soil nitrogen availability varies seasonally and across fine scale gradients is needed. Specifically, it is necessary to link soil nutrient availability to recognizable geomorphic units which can be used to scale to whole landscapes, and also to determine the relationship between nutrient availability and key model components such as plant functional type distribution. Here, we used Plant Root Simulators (PRS) to quantify inorganic nitrogen availability in contrasting micro-topographic positions (center, rim and trough) in four polygon types along a gradient from low-center polygons to degraded high-center polygons in coastal tundra on the Barrow Environmental Observatory (BEO) in northern Alaska during 2012 - 2013. We also determined peak above-ground biomass and nitrogen content, plant community composition (fractional leaf area coverage), and measured thaw depth, soil temperature and soil moisture throughout the 2012 growing season. We show that during early (June to mid-July) and late (mid-July to August) growing season, total inorganic N availability and the predominant form of N in the organic soil horizon depended on micro-topographic position, with lowest total available N in the high centers, and NO3- prevalent only in drier locations such as polygon rims and high and flat centers. We also demonstrate that above-ground, total vascular plant N correlated well with growing season NH4+ availability, but that this relationship was weakened by inclusion of non-vascular plant N. NH4+ availability and soil moisture were the main environmental gradients linked to plant community composition, though these factors were not independent. Overall, through linking soil nutrient dynamics to scalable landscape units, these findings enable improved representation of ecosystem processes in models of polygonal tundra landscapes; however, further insights will be gained from higher resolution seasonal measurements at multiple soil depths.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFMGC52B..05S
- Keywords:
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- 0470 BIOGEOSCIENCES Nutrients and nutrient cycling;
- 0469 BIOGEOSCIENCES Nitrogen cycling;
- 0476 BIOGEOSCIENCES Plant ecology